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Browse subject: riparian forests
Number of records: 42

Tests of landscape influence: nest predation and brood parasitism in fragmented ecosystems
About this Resource: The effects of landscape fragmentation on nest predation and brood parasitism, the two primary causes of avian reproductive failure, have been difficult to generalize across landscapes, yet few studies have clearly considered the context and spatial scale of fragmentation. Working in two river systems fragmented by agricultural and rural-housing development, we tracked nesting success and brood parasitism in ;mt2500 bird nests in 38 patches of deciduous riparian woodland. Patches on both river systems were embedded in one of two local contexts (buffered from agriculture by coniferous forest, or adjacent to agriculture), but the abundance of agriculture and human habitation within 1 km of each patch was highly variable. We examined evidence for three models of landscape effects on nest predation based on (1) the relative importance of generalist agricultural nest predators, (2) predators associated with the natural habitats typically removed by agricultural development, or (3) an additive combination of these two predator communities. We found strong support for an additive predation model in which landscape features affect nest predation differently at different spatial scales. Riparian habitat with forest buffers had higher nest predation rates than sites adjacent to agriculture, but nest predation also increased with increasing agriculture in the larger landscape surrounding each site. These results suggest that predators living in remnant woodland buffers, as well as generalist nest predators associated with agriculture, affect nest predation rates, but they appear to respond at different spatial scales. Brood parasitism, in contrast, was unrelated to agricultural abundance on the landscape, but showed a strong nonlinear relationship with farm and house density, indicating a critical point at which increased human habitat causes increased brood parasitism. Accurate predictions regarding landscape effects on nest predation and brood parasitism will require an increased appreciation of the multiple scales at which landscape components influence predator and parasite behavior.

Tsuga canadensis (L.) Carr. mortality will impact hydrologic processes in southern Appalachian forest ecosystems
About this Resource: Eastern hemlock (Tsuga canadensis (L.) Carr.) is one of the principal riparian and cove canopy species in the southern Appalachian Mountains. Throughout its range, eastern hemlock is facing potential widespread mortality from the hemlock woolly adelgid (HWA). If HWA-induced eastern hemlock mortality alters hydrologic function, land managers will be challenged to develop management strategies that restore function or mitigate impacts. To estimate the impact that the loss of this forest species will have on the hydrologic budget, we quantified and modeled transpiration over a range of tree sizes and environmental conditions. We used heat dissipation probes, leaf-level gas-exchange measurements, allometric scaling, and time series modeling techniques to quantify whole-tree and leaf-level transpiration (EL) of eastern hemlock. We monitored trees ranging from 9.5 to 67.5 cm in diameter along a riparian corridor in western North Carolina, USA during 2004 and 2005. Maximum rates of daily tree water use varied by diameter and height, with large trees transpiring a maximum of 178-186 kg H2O·tree-1·d-1. Values of EL could be predicted from current and lagged environmental variables. We forecasted eastern hemlock EL for inventoried stands and estimated a mean annual transpiration rate of 63.3 mm/yr for the hemlock component, with 50% being transpired in the winter and spring. In typical southern Appalachian stands, eastern hemlock mortality would thus reduce annual stand-level transpiration by 10% and reduce winter and spring stand-level transpiration by 30%. Eastern hemlock in the southern Appalachians has two distinct ecohydrological roles: an evergreen tree that maintains year-round transpiration rates and a riparian tree that has high transpiration rates in the spring. No other native evergreen in the southern Appalachians will likely fill the ecohydrological role of eastern hemlock if widespread mortality occurs. With the loss of this species, we predict persistent increases in discharge, decreases in the diurnal amplitude of streamflow, and increases in the width of the variable source area.

An assessment of dead wood patterns and their relationships with biophysical characteristics in two landscapes with different disturbance histories in coastal Oregon, USA
About this Resource: Understanding the relative importance of landscape history, topography, vegetation, and climate to dead wood patterns is important for assessing pattern-process relationships related to dead wood and associated biodiversity. We sampled dead wood at four topographic positions in two landscapes (1400-2100 km2) that experienced different wildfire and salvage histories in coastal Oregon. Study objectives were to (i) determine whether and how the landscapes differed in dead wood amounts and characteristics and (ii) evaluate relationships between dead wood characteristics and potentially related biophysical variables associated with historical and current vegetation, topography, climate, soils, and ecoregion. Despite differences in history, the two landscapes differed little in total dead wood volume; however, they differed in dead wood volume by structural type, decay class, and source (legacy/nonlegacy). Dead wood varied by topographic position, and topography was of greatest importance compared with other factors. In this mountainous region, upper topographic positions may be source areas for dead wood and riparian areas and streams sinks for dead wood. Climate explained more variance in dead wood in the landscape that burned earlier and was not salvaged. Landscape-scale patterns of dead wood are evident in landscapes with different disturbance histories and despite finer-scale variation in topography, vegetation, and other biophysical attributes.

Reduced-impact logging: Challenges and opportunities
About this Resource: Over the past two decades, sets of timber harvesting guidelines designed to mitigate the deleterious environmental impacts of tree felling, yarding, and hauling have become known as “reduced-impact logging” (RIL) techniques. Although none of the components of RIL are new, concerns about destructive logging practices and worker safety in the tropics stimulated this recent proliferation of semi-coordinated research and training activities related to timber harvesting. Studies in Southeast Asia, Africa, and South and Central America have clearly documented that the undesired impacts of selective logging on residual stands and soils can be substantially reduced through implementation of a series of recommended logging practices by crews that are appropriately trained, supervised, and compensated. Whether reducing the deleterious impacts of logging also reduces profits seems to depend on site conditions (e.g., terrain, soil trafficability, and riparian areas), whether the profits from illegal activities are included in the baseline, and the perspective from which the economic calculations are made. A standardized approach for calculating logging costs using RILSIM software is advocated to facilitate comparisons and to allow uncoupling RIL practices to evaluate their individual financial costs and benefits. Further complicating the matter is that while there are elements common to all RIL guidelines (e.g., directional felling), other components vary (e.g., slope limits of 17-40° with ground-based yarding). While use of RIL techniques may be considered as a prerequisite for sustaining timber yields (STY), in particular, and sustainable forest management (SFM), in general, RIL should not be confounded with STY and SFM. This confusion is particularly problematic in forests managed for light-demanding species that benefit from both canopy opening and mineral soil exposure as well as where harvesting intensities are high and controlled primarily by minimum diameter cutting limits. These qualifications notwithstanding, since logging is the most intensive of silvicultural treatments in most tropical forests managed for timber, some aspects of RIL are critical (e.g., protection of water courses) whether forests are managed for STY, SFM, or even replacement by agricultural crops.

Soil Attributes in a Sierra Nevada Riparian Meadow as Influenced by Grazing.
About this Resource: Data on the effects of livestock grazing on soil nutrient availability are virtually nonexistent for meadow systems. We measured the effect of livestock grazing on soil, emphasizing soil-solution chemistry, in a Sierra Nevada riparian meadow. Treatments were livestock exclusion (begun in 1989) and grazing to leave 1000 kg·ha-1 of vegetation. Ceramic tension lysimeters were placed in the treatments (2 replicates) by landscape position (stream edge, midfloodplain, and forest edge), and by depth (approximately 0.1, 0.6, and 1.2 m below the soil surface). Lysimeter water was extracted twice monthly in April, May, and June of 1990 through 1993, and cations and anions were quantified. In addition, KCl-extractable NO3- and NH4+; bicarbonate-extractable ortho-P; available Mn, Cu, Fe, and Zn; and root-length density (RLD) were quantified in soils by treatment, landscape position, and soil depth in July 1991 and September 1993. RLD was not affected by grazing. Significant (P0.05) treatment effects were largely limited to the forest edge. The grazed treatment had greater lysimeter-extractable Na+, Ca+2, Mg+2, and NO3-; higher pH; and less K+ and NH4+ than the excluded treatment. Compared with corresponding excluded treatments, bicarbonate-extractable P was significantly greater on the grazed forest edge, and available Mn was significantly greater at the grazed stream-edge position in 1991. Extractable NO3- was significantly higher in the 0-25 cm depth increment of the grazed treatment, and available Zn was significantly greater on the grazed midfloodplain position in 1993. Grazing did not result in more anoxic soil conditions than the excluded treatment. Grazing effects were most pronounced at the forest edge, possibly as a result of spatial transfer of nutrients via cow urine and feces. Management goals to sustain high-elevation meadows should emphasize maintenance of high RLD to sequester soil nutrients.

Dynamics of wood in stream networks of the western Cascades Range, Oregon
About this Resource: We develop and test a conceptual model of wood dynamics in stream networks that considers legacies of forest management practices, floods, and debris flows. We combine an observational study of wood in 25 km of 2nd- through 5th-order streams in a steep, forested watershed of the western Cascade Range of Oregon with whole-network studies of forest cutting, roads, and geomorphic processes over the preceding 50 years. Statistical and simple mass balance analyses show that natural process and forest management effects on wood input, transport processes, and decomposition account for observed patterns of wood in the stream network. Forest practices reduced wood amounts throughout the network; in headwater streams these effects are fixed in stream segments bordered by cuts and roads, but in larger channels they are diffused along the channel by fluvial transport of wood. Landforms and roads limited delivery of wood by debris flows to mainstem channels. Network dynamics studies and watershed management plans should include spatial patterns of debris flow initiation and runout, flood redistribution, and reduction of wood in the network by forest cutting and intentional wood removal from channels on time scales of forest succession and recurrence of major floods.

Changes in Vegetation Condition and Surface Fluxes during NAME 2004
About this Resource: The vegetation in the core region of the North American monsoon (NAM) system changes dramatically after the onset of the summer rains so that large changes may be expected in the surface fluxes of radiation, heat, and moisture. Most of this region lies in the rugged terrain of western Mexico and very few measurements of these fluxes have been made in the past. Surface energy balance measurements were made at seven sites in Sonora, Mexico, and Arizona during the intensive observation period (IOP) of the North American Monsoon Experiment (NAME) in summer 2004 to better understand how land surface vegetation change alters energy flux partitioning. Satellite data were used to obtain time series for vegetation indices and land surface temperature for these sites. The results were analyzed to contrast conditions before the onset of the monsoon with those afterward. As expected, precipitation during the 2004 monsoon was highly variable from site to site, but it fell in greater quantities at the more southern sites. Likewise, large changes in the vegetation index were observed, especially for the subtropical sites in Sonora. However, the changes in the broadband albedo were very small, which was rather surprising. The surface net radiation was consistent with the previous observations, being largest for surfaces that are transpiring and cool, and smallest for surfaces that are dry and hot. The largest evaporation rates were observed for the subtropical forest and riparian vegetation sites. The evaporative fraction for the forest site was highly correlated with its vegetation index, except during the dry spell in August. This period was clearly detected in the land surface temperature data, which rose steadily in this period to a maximum at its end.

Historical fires in Douglas-fir dominated riparian forests of the southern Cascades, Oregon
About this Resource: Despite the ecological importance of fire in Pacific Northwest forests, its role in riparian forests is just beginning to be documented. This study reconstructed the historical occurrence of fire within riparian forests along different stream sizes in coast Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirbel] Franco) dominated forests within the drier western hemlock (Tsuga heterophylla [Raf.] Sarg.) forest series of the Upper Steamboat Creek watershed of the Umpqua National Forest, Oregon. Fire dates were determined from a total of 194 firescarred wedges from stumps sampled at 15 riparian and 13 upslope one-hectare plots. Fire was common historically in both the riparian zones and upslope forests of this study area. Riparian Weibull median probability fire return intervals (WMPIs) were somewhat longer (ranging from 35-39 years, with fire return intervals ranging from 4-167 years) than upslope WMPIs (ranging from 27-36 years, with fire return intervals ranging from 2-110 years), but these differences were not significant. Fires were probably mixed in severity and likely patchy, considering the high incidence of fires occurring only at a riparian plot or only at an upslope plot within a pair, but not at both. Finally, fire return intervals showed a non-significant trend of decreasing length from west to east to north aspects. An increased sampling effort may have shown this decrease to be significant. Based on the results from this study, it is evident that restoring fire will be necessary to protect riparian forest health in this study area. Historical recruitment of large woody debris was likely patchy and pulsed for these mixed-severity fire regime forests.

Transpiration of cottonwood/willow forest estimated from sap flux
About this Resource: Cottonwood/willow forests in the American Southwest consist of discrete, even-aged vegetation patches arranged in narrow strips along active and abandoned stream channels of alluvial flood plains. We used the heat-pulse velocity technique in this study to estimate transpiration in 12 such forest patches along a perennially flowing reach of the San Pedro River in southeastern Arizona, USA during five periods from April to October 1997. Transpiration per unit sapwood area was consistently higher for the larger cottonwood trees found on outer secondary channels compared to that of smaller cottonwood trees along the active channel, but statistically significant differences were found only in August and October. Conversely, transpiration per unit sapwood area in willow was markedly higher for trees along the primary channel than for those few larger trees that were sampled on the outer margins of the forest. Average daily transpiration at the canopy scale among the patches in July was 4.8±0.7 mm per day and ranged from 5.7±0.6 mm per day in young forest patches adjacent to the primary stream channel to 3.1±0.6 mm per day in more successionally advanced patches on secondary channels. Differences in our estimates of transpiration between forest patches along primary and secondary stream channels were related to differences in the ratio of sapwood area to ground area of the forest patches, and leaf area index. Estimates of transpiration from this forest type, and projections of transpiration and groundwater flux over larger areas on the San Pedro River, should take into account structural variation in these forests that relate to population dynamics of dominant trees.

Cicada emergence in Southwestern riparian forest: influences of wildfire and vegetation composition
About this Resource: Annually emerging cicadas are a numerically and ecologically dominant species in Southwestern riparian forests. Humans have altered disturbance regimes that structure these forests such that floods are less common and wildfires occur more frequently than was historically the case. Impacts of these changes on primary consumers such as riparian cicadas are unknown. Because cicadas are consumed by a variety of animal species, disturbances that alter timing of their emergence or abundance could have consequences for species at higher trophic levels. We trapped emerging cicadas (Tibicen dealbatus) in burned and unburned riparian forest plots along the Middle Rio Grande in central New Mexico (USA) to determine effects of wildfire and vegetation structure on their density and phenology. We measured vegetation variables and soil temperature at cicada traps and related these variables to variation in emergence density and phenology. We also experimentally heated soil under emergence traps to examine the relationship between soil temperature and emergence phenology. Emergence density was similar in wildfire and unburned plots, though emergence date averaged earlier in wildfire plots and experimentally heated traps. We identified models containing cottonwood proximity (distance from the nearest cottonwood tree) and cottonwood canopy coverage as the most parsimonious explanations of emergence density at each trap. Model selection results were consistent with the literature and field observations that showed that cottonwood trees are an essential resource for T. dealbatus. Cottonwood canopy was also correlated with low soil temperatures, which are associated with later emergence dates. Failure of cottonwoods to reestablish following wildfire could result in cicadas emerging at lower densities and at earlier dates. For cicadas to emerge at densities and times that provide the greatest benefits to birds and other riparian-obligate secondary consumers, riparian forests should be protected from fire, and native vegetation in wildfire sites should be restored.

Controls on transpiration in a semiarid riparian cottonwood forest
About this Resource: Cottonwood (Populus spp.) forests are conspicuous and functionally important elements of riparian vegetation throughout much of the western U.S. Understanding how transpiration by this vegetation type responds to environmental forcing is important for determining the water balance dynamics of riparian ecosystems threatened by groundwater depletion. Transpiration was measured in semiarid riparian cottonwood (Populus fremontii) stands along a perennial and an intermittent reach of the San Pedro River in southeastern Arizona. Sap flow was measured using thermal dissipation probes and scaled to the stand level to investigate stand water use in relation to canopy structure, depth to groundwater and climate forcing. The cottonwood stand located at the perennial stream site had higher leaf-to-sapwood area ratio (0.31 ± 0.04 m2 cm-2), leaf area index (2.75) and shallower groundwater depth (1.1-1.8 m) than the stand at the intermittent stream site (0.21 ± 0.04 m2 cm-2, 1.75 and 3.1-3.9 m, respectively). Moreover, total annual transpiration was higher at the perennial stream site (966 mm) than at the intermittent stream site (484 mm). The significant positive and linear correlation between transpiration and vapor pressure deficit indicated high hydraulic conductance along the root-shoot pathway of cottonwood trees at the perennial stream site. During the peak dry period prior to the summer rainy season, the trees at the intermittent stream site exhibited greater water stress as transpiration did not increase beyond its mid-morning peak with increasing vapor pressure deficit, which was likely due to leaf stomatal closure. However, this stress was alleviated after significant monsoonal rains and runoff events had recharged soil moisture and raised groundwater levels. Riparian cottonwood forests are exposed to extreme fluctuations in water availability and transpiration demand throughout the growing season, and their access to shallow groundwater sources determines their structural and physiological responses to drought. Spatial and temporal variation in depth to groundwater induces drought stress in cottonwood threatening their productivity and existence along the river systems throughout much of western U.S.

Riparian communities associated with Pacific Northwest headwater streams: assemblages, processes, and uniqueness
About this Resource: Riparian areas of large streams provide important habitat to many species and control many instream processes - but is the same true for the margins of small streams? This review considers riparian areas alongside small streams in forested, mountainous areas of the Pacific Northwest and asks if there are fundamental ecological differences from larger streams and from other regions and if there are consequences for management from any differences. In the moist forests along many small streams of the Pacific Northwest, the contrast between the streamside and upslope forest is not as strong as that found in drier regions. Small streams typically lack floodplains, and the riparian area is often constrained by the hillslope. Nevertheless, riparian-associated organisms, some unique to headwater areas, are found along small streams. Disturbance of hillslopes and stream channels and microclimatic effects of streams on the riparian area provide great heterogeneity in processes and diversity of habitats. The tight coupling of the terrestrial riparian area with the aquatic system results from the closed canopy and high edge-to-area ratio for small streams. Riparian areas of the temperate, conifer dominated forests of the Pacific Northwest provide a unique environment. Forest management guidelines for small streams vary widely, and there has been little evaluation of the local or downstream consequences of forest practices along small streams.

Sensitivity of riparian ecosystems in arid and semiarid environments to moisture pulses
About this Resource: Structural and functional dynamics of riparian vegetation in arid and semiarid basins are controlled by hydrological processes operating at local, landscape and catchment scales. However, the importance of growing-season precipitation as a control on evapotranspiration (ET) and carbon cycling in these ecosystems varies considerably across the riparian landscape, depending largely on access to the near-surface water table. Here we describe key findings from ongoing ecohydrological studies along the Upper San Pedro River (USPR) in semiarid, south-eastern Arizona, USA. Depth to the water table varies substantially across the riparian landscape along the USPR drainage, and is a key factor controlling the sensitivity of cottonwood (Populus fremontii) water-source use, transpiration rate and photosynthetic metabolism to inputs of monsoonal moisture during the growing season. Landscape-scale functional variation in cottonwood forests has been incorporated into spatially explicit ET models for estimating water balance components along the USPR. However, of greater importance for understanding controls on water and carbon exchange processes in the riparian corridor is the conversion of sacaton (Sporobolus spp.) grasslands on pre-entrenchment floodplain terraces to communities dominated by the deep-rooted woody legume, mesquite (Prosopis velutina). Mesquite is now the dominant cover in the riparian corridor and has increased by more than 300% in the USPR basin since 1972. The physiognomic shift from grassland to mesquite woodland on pre-entrenchment floodplain terraces alters the sensitivity of ET and CO2 exchange to inputs of growing-season precipitation. Because mature mesquite shrubs and trees have greater access to groundwater in these habitats than sacaton, ET and gross ecosystem production (GEP) are relatively decoupled from variation in monsoonal precipitation. However, decomposition of litter and soil organic matter in floodplain ecosystems remains highly coupled to monsoonal moisture inputs after mesquite encroachment. Responses of net ecosystem exchange of CO2 (NEE) to inputs of monsoonal rainfall are therefore not simple, but depend on vegetation composition and the connection of dominant plants to the water table. The heterogeneous vegetation patterns and groundwater depths in the riparian landscape offer unique opportunities for understanding fundamental ecohydrological processes linking carbon and water cycles in both riparian and upland ecosystems.

Headwater riparian forest-floor invertebrate communities associated with alternative forest management practices
About this Resource: Headwater streams and their riparian zones are a common, yet poorly understood, component of Pacific Northwest, USA, landscapes. We describe the ecological importance of headwater stream riparian zones as habitat for forest-floor invertebrate communities and assess how alternative management strategies for riparian zones may impact these communities. We compared community composition of forest-floor invertebrates at increasing distances along trans-riparian (stream edge to upslope) transects in mature forests, clearcuts, and riparian buffers of 30-m width with upslope clearcuts. Invertebrates were collected using pitfall traps in five replicate blocks of three treatments each in the Willamette National Forest, Oregon, USA. We measured microclimate and microhabitat variables at pitfall locations. Despite strong elevation and block effects on community composition, community analyses revealed a distinct “riparian” invertebrate community within 1 m of the stream edge in mature forest treatments, which was strongly related to cool, humid microclimate conditions. Invertebrate community composition in buffer treatments was far more similar to that of mature forests than to clearcuts; a pattern mirrored by microclimate. These results suggest that, within our study sites, forest-floor invertebrate distributions are strongly associated with microclimate and that riparian buffers of 30-m width do provide habitat for many riparian and forest species. Riparian reserves may serve as effective forest refugia and/or dispersal corridors for invertebrates and other taxa, and their incorporation into watershed management plans likely will contribute to meeting persistence and connectivity objectives.

The lemur diversity of the Fiherenana - Manombo Complex, southwest Madagascar
About this Resource: We conducted the first comprehensive lemur survey of the Fiherenana - Manombo Complex (Atsimo - Andrefana Region), site of PK32-Ranobe, a new protected area within the Madagascar Protected Area System. Our cross - seasonal surveys of three sites revealed the presence of eight lemur species representing seven genera and four families, of which three are diurnal and five are nocturnal species. Six species were only recorded in the riparian and transitional forests of the Fiherenana and Manombo river valleys, while the spiny thicket at Ranobe contains only Microcebus (two species), all larger species having been extirpated by hunting in recent years. Two of our records (Mirza coquereli and Cheirogaleus sp.) represent new locality records or range extensions, but we failed to record one species (Phaner pallescens) expected to occur in the area, and question the literature supporting its presence south of the Manombo river. Our findings highlight the importance of the Fiherenana-Manombo Complex for the conservation of lemurs in southwest Madagascar, but also show that PK32 - Ranobe fails to protect the full lemur diversity of the Complex. The protected area does not include the riparian forests of the Manombo and Fiherenana rivers, and at least three lemur species are therefore unprotected. We strongly support the proposed extension of the protected area to include these riparian forests as well as other important habitats for locally endemic bird and reptile taxa. RÉSUMÉ: La zone du Complexe Fiherenana - Manombo (Région d’Atsimo- Andrefana), site de PK32 - Ranobe, une nouvelle aire protégée dans le Système des Aires Protégées de Madagascar (SAPM), a fait l’objet d’un premier inventaire de lémuriens. Nos prospections dans trois sites à différentes saisons ont révélé la présence de huit espèces de lémuriens représentés dans sept genres et trois familles, dont trois sont des espèces diurnes et cinq sont des espèces nocturnes. Nous n’avons pas pu identifier l’espèce du genre Lepilemur ni celle du genre Cheirogaleus à défaut de disposer de spécimens. Six espèces ne se trouvaient que dans les forêts riveraines et les forêts de transition des vallées des fleuves Fiherenana et Manombo. Le fourré épineux de Ranobe n’abrite que des Microcebus (deux espèces), toutes les espèces plus grandes ayant déjà été exterminées par la chasse au cours des dernières années. Nos estimations de densité indiquent que la population des Microcebus est deux fois plus importante dans le fourré épineux que dans la forêt riveraine (1,078 individus / km² vs. 546 individus / km²). Nous avons estimé la densité d’Eulemur rufus à 40 groupes / km² dans la vallée du Fiherenana, mais nos transects ne nous ont pas permis d’obtenir des estimations fiables pour les densités de Lemur catta et de Propithecus verreauxi. Deux des espèces répertoriées (Mirza coquereli et Cheirogaleus sp.) représentent de nouvelles observations pour la zone ou des extensions de leurs aires de répartition connues, mais nous n’avons pas pu trouver l’espèce Phaner pallescens qui devait être présente dans la zone et nous émettons des doutes portant sur les références publiées rapportant la présence de l’espèce au sud du fleuve Manombo. Nos résultats mettent en exergue l’importance du Complexe Fiherenana - Manombo pour la conservation des lémuriens dans le sud - ouest de Madagascar, mais ils indiquent que l’aire protégée de PK32 - Ranobe ne protège pas la diversité complète des lémuriens du Complexe. Les forêts riveraines des fleuves Fiherenana et Manombo ne sont pas incluses dans l’aire protégée de sorte qu’au moins trois espèces de lémuriens ne bénéficient alors d’aucune protection. Compte tenu des objectifs du SAPM et plus particulièrement de l’Objectif 1, à savoir ‘Conserver l’ensemble de la biodiversité unique de Madagascar’, nous estimons que la nouvelle aire protégée du PK32-Ranobe n’atteint pas ces objectifs et nous appuyons les efforts des promoteurs afin de re-délimiter l’aire protégée pour inclure les forêts riveraines ainsi que d’autres habitats importants pour la conservation des oiseaux et des reptiles localement endémiques.

The effects of riparian forest management on the freshwater environment: a literature review of best management practice
About this Resource: National Forests and Water Guidelines require the establishment of riparian buffers to help protect the freshwater environment from disturbance by silvicultural operations on the adjacent land. The main functions of the riparian buffer are considered to be sediment removal and erosion control, protection of water quality, moderation of shade and water temperature, maintenance of habitat structural diversity and ecological integrity, and improvement of landscape quality. This review paper assesses how these functions are affected by the design and management of the riparian forest zone, with a focus on the width of the buffer, the structure of the vegetation and species choice. It is not possible to specify a definitive riparian buffer width that will protect the freshwater environment from every potential threat. Forestry agencies usually recommend widths between 10 and 30 m. Buffer widths towards the lower end of this scale tend to protect the physical and chemical characteristics of a stream, while the maintenance of ecological integrity requires widths at the upper end. In terms of structure and species, the benefits are greatest where the riparian buffer replicates native riparian woodland with an open canopy of mixed species of varied age class. The optimum level of shade is difficult to quantify but limited work suggests that a good balance is achieved where around 50% of the stream surface is open to sunlight and the remainder covered by dappled shade. Within the management of riparian woodland there is a need to consider a stream’s sensitivity and intrinsic value. Some sites will benefit from active intervention such as thinning, coppicing or pollarding, while others will be favoured by a hands-off approach. Long-term continuity of management is important to ensure that the potential benefits to the freshwater environment are realised. Keywords: riparian woodland, riparian buffer, woodland management, freshwater environment, water quality

Relative humidity gradients across riparian areas in eastern Oregon and Washington forests
About this Resource: Riparian relative humidity (RH) gradients were examined at 12 sites east of the Cascade Mountains in Oregon and Washington (USA) in 1997. All the sites were on commercial timber lands with selective (partial) harvesting as the silvicultural prescription. The microclimatic information is needed to prescribe effective buffers for riparian dependent flora and fauna in eastside forests. RH was monitored at increasing distances from the stream edge to 30 m into the adjacent riparian forests. Within 10 m of the stream edge RH was similar to upland conditions with little change beyond 10 m. At 9 of the 12 sites differences in mean minimum RH were significant (P<0.05) between 0 and 5 m. The length of time that RH was less than 50% between 0 and 5 m was significant at 11 of the 12 sites. Diurnal fluctuation ranges of more than 75% RH with maximums close to 100% occurred at night at all sites. The diurnal pattern of temperature is the dominant process in air moisture regime in these eastside forests. The small daytime increases in RH close to the stream, which can be maintained over short distances by steep local topography, are apparently due to evaporation from wetted stream width and transpiration from vegetation immediately adjacent to the stream.

SWAT Revisions for Simulating Landscape Components and Buffer Systems
About this Resource: Methods for simulating different landscape positions within the SWAT model are being examined. A three component system, consisting of the watershed divide, the hillslope, and the floodplain landscape positions, has been developed to address flow and transport across hydrologic response units prior to concentration in streams. The modified SWAT model is capable of simulating flow and transport from higher landscape positions to lower positions within a single river basin. The revision was developed to address variable source areas within watersheds and stream-side buffer systems which exist alongside many streams. The enhanced model will allow for more accurate simulation of natural transport processes within a hillslope. The revision was tested using data collected from a low-gradient watershed near Tifton, Georgia, USA which contains heavily vegetated riparian buffers. The modified model provided reasonable simulations of surface and subsurface flow across the landscape positions without calibration. The application demonstrates the applicability of the model to simulate filtering of surface runoff, enhanced infiltration, and water quality buffering typically associated with riparian buffer systems.

Loss of foundation species: consequences for the structure and dynamics of forested ecosystems
About this Resource: In many forested ecosystems, the architecture and functional ecology of certain tree species define forest structure and their species-specific traits control ecosystem dynamics. Such foundation tree species are declining throughout the world due to introductions and outbreaks of pests and pathogens, selective removal of individual taxa, and over-harvesting. Through a series of case studies, we show that the loss of foundation tree species changes the local environment on which a variety of other species depend; how this disrupts fundamental ecosystem processes, including rates of decomposition, nutrient fluxes, carbon sequestration, and energy flow; and dramatically alters the dynamics of associated aquatic ecosystems. Forests in which dynamics are controlled by one or a few foundation species appear to be dominated by a small number of strong interactions and may be highly susceptible to alternating between stable states following even small perturbations. The ongoing decline of many foundation species provides a set of important, albeit unfortunate, opportunities to develop the research tools, models, and metrics needed to identify foundation species, anticipate the cascade of immediate, short- and long-term changes in ecosystem structure and function that will follow from their loss, and provide options for remedial conservation and management.

Estimating the biomass of harvestable epiphytic moss in Central Western Oregon
About this Resource: To address the need for inventory estimates for the non-timber forest product of epiphytic moss (a mixture of bryophytes), we inventoried 100 randomly selected 1/8 ha sites in 50- to 200-year-old upland and riparian forests below 915 m elevation in central western Oregon, USA. All commercially harvestable moss was removed from each site, using methods commonly employed by commercial harvesters, and weighed. Although harvestable epiphyte mats were found in 29% of the sites, only 6% had enough moss for the site to be considered harvestable by commercial standards (>50 kg/ha). The commercial moss biomass inventories across all sites, which ranged from 0 kg/ha to 217 kg/ha, are substantially lower than those previously reported for northern Oregon. We examined relationships of harvestable moss occurrence and abundance to environmental variables to facilitate the understanding and prediction of harvestable moss biomass on the landscape. Harvestable moss was most likely to be found in low elevation (<500 m) areas, within 50 m of perennial water, on sites that supported more than 10 m2/ha in hardwood basal area, and on sites that lacked dry-site shrubs such as Berberis nervosa, Gaultheria shallon, and Holodiscus discolor. Our inventory method is presented and its applicability to other regions is discussed.

Postfire response of red alder, black cottonwood, and bigleaf maple to the Whatcom Creek fire, Bellingham, Washington
About this Resource: The June 1999 pipeline leak and subsequent explosion in Whatcom Creek resulted in a fire that scorched ~10 ha of coniferous and riparian forest in Bellingham, Washington, USA. This fire provided an opportunity to study the postfire responses of red alder (Alnus rubra), black cottonwood (Populus trichocarpa) [P. balsamifera subsp. trichocarpa], and bigleaf maple (Acer macrophyllum) in the 3.2-ha scorched riparian zone. Bigleaf maple endures all but the most intense fires, resprouting vigorously after fire. Red alder and black cottonwood are known resprouters that may survive low intensity fires, but data about their responses to fire are sparse. The postfire status of every tree in the burn zone was evaluated immediately after the fire in June 1999, and during the first postfire growing season in May 2000. Tree response, in relation to trunk diameter, percent crown scorch, and percent bark scorch, was categorized as (1) alive with a new leafy crown; (2) topkilled and resprouted; or (3) dead. Fire intensity was higher on the left bank (left side of the creek when facing downstream), where trees experienced greater mortality. More than half the 854 trees in the burn zone survived the fire, 57% by forming new leafy crowns and 43% by resprouting. Red alder, black cottonwood and bigleaf maple demonstrated abilities to survive a disturbance to which they are not ordinarily subjected. All three species resisted low intensity fire and reformed leafy crowns on the right bank, and they endured moderate to high intensity fire by resprouting after topkill on the left bank. On the left bank, probabilities of surviving 100% crown scorch were 0.24 for red alder, 0.66 for black cottonwood, and 0.68 for bigleaf maple; probabilities of surviving 100% bark scorch were 0.09 for red alder, 0.66 for black cottonwood, and 0.60 for bigleaf maple.

EVALUATION OF NATURAL RECOVERY OF CILIARY FORESTS IN SPRING IN THE SOUTH AREA OF MINAS GERAIS
About this Resource: This study evaluated the efficiency of the natural regeneration process, as a method of riparian forest rehabilitation surrounding anthropized water spring. The work was conducted in two water springs. The spring 1 is located in Lavras-MG county and 2 in Itumirim-MG county. This last one presented two quite different situations; part of it was classified as disturbed area and part classified as degraded area. For evaluating the floristic composition and structure of the natural regeneration, 37 portions of 10 x 2,0 m, in the Spring 1, and, 74 portions in Spring 2, 37 in each area, were plotted. All individuals with DBH lower than 5 cm and height higher than 0.10 m were registered and identified. Aspects related to physiognomic structure were analyzed (density, frequency and distribution of the heights of the plants in size classes) and communitarian (composition and diversity). For the two springs, 528 and 593 individuals in the first and second evaluation, respectively, were registered. However, in relation to the number of species, it was not verified any change between the first and the second evaluation (46 species). It was observed that, seven months after the isolation of the area, a significant increase of 9. 5%, 11,8% and 17% in the spring 1 and in spring 2 disturbed area and in spring 2 degraded area, respectively. The results indicate that natural regeneration is efficient for recovering disturbed and degraded springs.

Patrones de preferencias de hábitat y de distribución y abundancia invernal de aves en el centro de España. Análisis y predicción del efecto de factores ecológicos
About this Resource: Patterns of habitat preference and distribution and abundance of wintering bird fauna in central Spain. Analysis and prediction of the effect of ecological factors.- This paper analyses the effect of geographic, topographic, land use and habitat structure variables on the composition and structure of wintering bird communities in Central Spain (Iberian peninsula). Parameters describing the avifauna varied in a predictable way considering a small group of coarse-grained variables defining the geographical and altitudinal location of the censuses, and the basic characteristics of the structure and typology of habitats: 49-76% of variance accounted for total bird density and for abundance of four ecological groups, 37-63% accounted for species richness and diversity, and 65% explained the relative abundance of species with conservation problems according to the European scale (SPEC figs.). Regarding the most widespread species in the study area, significant models were obtained by means of tree regression analysis for 50 species, with an average reduction of deviance of 39%. Altitude was the most important variable affecting bird community parameters and abundance of each bird species, showing a consistent and marked negative effect. Structural complexity of the vegetation and geographical location followed as the variables of importance explaining variability. The habitats with the lowest bird density, richness and diversity of birds were mountain grasslands/shrublands, young pine re-forestations, and Pyrenean oak forests at 1,200-1,600 m a.s.l. The habitats with the highest values on these parameters were riparian forests, agricultural mosaics, and holmoak 'dehesa' parklands, mainly located at the southern and western part of the region and at intermediate altitudes. The total density of birds increased from east to west, was higher in intermediate altitudes than in the extremes of the altitudinal range, and increased with habitat structural complexity (i.e., vertical development and degree of vegetation cover), agricultural use of the land, and the presence of water (e.g., streams, rivers, flooded areas). Density of strictly wintering species in the study region decreased latitudinally from southeast to northwest, being higher at intermediate altitudes in localities with presence of water and woodlands dominated by coniferous trees. Abundance of facultative or obligate frugivorous species was very low. Richness of species was higher toward the western part of the study area, increased with habitat structural complexity, and was lower at higher altitudes. On the other hand, the less diverse bird assemblages were those that inhabit agricultural landscapes and/or areas located at higher altitudes. Habitats and areas with a higher relative abundance of species with conservation problems at the European scale (SPEC scores) were located at intermediate altitudes in the southwest and southeast of the study region. The relative abundance of this group of species was also associated to the presence of water, habitat structural complexity and agricultural use. The relationship between the European conservation status of species (SPEC scores) and the patterns of distribution, abundance, habitat preferences and ecological width of 72 species was also analysed. Species with more conservation problems on the European scale have a marked preference for structurally simpler habitats (e.g., agricultural and grasslands habitats) and have a broader altitudinal and among-habitats distribution. Results from the 44 census localities were extrapolated to the remaining region using a geographical information system in order to build predictive maps for density, species richness, species diversity and weighed European conservation status. This work shows that valuable knowledge can be obtained from fragmentary and dispersed data, in order to describe general patterns of distribution, abundance and habitat preferences of birds. This methodological approach could be a valid in environmentally heterogeneous, large regions, with few qualified bird observers and researchers.

Use of woody debris piles by birds and small mammals in a riparian corridor
About this Resource: Woody debris piles, a natural component of rivers draining the coastal forests of the Pacific Northwest, provide a unique resource in the riparian-river corridor. We describe the distribution of woody debris piles on the Skykomish River, Washington, and examine their use by birds and small mammals. We found an average of one debris pile per 15 m of river bank; the inside of these piles was significantly cooler than the ambient environment. Over sixteen bird species were observed using the debris piles while other bird species in the area were never observed on the debris piles. The overall species richness of small mammals was greater at debris piles (9 species) than at reference sites in nearby areas without woody debris (4 species). On cobble bars, there was a greater abundance of small mammals at debris piles than at reference sites. We conclude that debris piles may provide valuable resources to both birds and small mammals particularly on otherwise barren cobble bars

The influence of forest health and protection treatments on erosion and stream sedimentation in forested watersheds of Eastern Oregon and Washington
About this Resource: A variety of Forest Health and Protection treatments have been proposed to reduce long-term risks to forests from wildfire, insects, and disease. This review examines the potential effects of these treatments on sediment production in watersheds of eastern Oregon and Washington, USA, channel forming processes, riparian vegetation, and risks posed to riparian zones. Wildfires can affect upland erosion; however, erosion from prescribed fires burning the same area should be much smaller. Dense riparian vegetation might help regulate the amount of sediment that reaches streams, but this effect would be strongly dependent on the geomorphic setting. Forest pathogens are not expected to cause accelerated erosion and stream sedimentation directly, but indirect effects might be substantial if they lead to increased wildfire. The largest risk of accelerated erosion is expected from ground-disturbing activities during fuels reduction treatments, such as construction of roads and firebreaks or salvage logging or thinning. Intense grazing has changed composition and cover of riparian vegetation, leading to bank erosion, and in many places, widening or incision of stream channels. Improved grazing prescriptions can result in major changes to riparian vegetation, but response of channel morphology will most likely be slow. Most of the studies reviewed were conducted at the site or small-watershed scale. Consequently, conclusions at these scales are generally well supported by the available literature. The cumulative effects of forest health and protection treatments imposed across a large region are difficult to assess, however. Given the current state of knowledge, dramatically changing forest land use practices across eastern Oregon and Washington-including the widespread use of prescribed fires, salvage logging, and mechanical fuel treatments-is a long-term, landscape-scale experiment, the cumulative effects of which are unknown.

Distribution, abundance, and habitat association of riparian-obligate and -associated birds in the Oregon Coast Range
About this Resource: We studied the abundance, distribution, and habitat associations of the aquatic-foraging riparian-associated vertebrate community along four stream basins transecting managed forests in the Oregon Coast Range, 1992-1994. The riparian-associated community we observed consisted primarily of birds with few observations of mammals. Belted kingfishers (Ceryle alcyon), American dippers (Cinclus mexicanus), great blue herons (Ardea herodias), and mallards (Anas platyrhynchos) comprised >85% of these observations, but we observed only one group (gtoreq1 individual observed together) from this community for each kilometer of stream surveyed. Bird abundances among years were not different (all P > 0.05). Species distribution was affected by stream order, stream basin, and season in each species, but to varying degrees. Belted kingfishers, common mergansers (Mergus merganser), great blue herons, green herons (Butorides striatus), and mallards were more abundant in larger, 6th-orderstreams than in smaller, 4th-order streams (P < 0.05). Dippers used step channel units disproportionally more and riffles disproportionately less than expected (P < 0.5). Similarly, kingfishers used fewer riffles and more pool channel units than was expected (P < 0.5). Key habitat components that were predictive of use were species specific. Most notably, the presence of a forested riparian area, streamside trees, and valley walls that constrain the stream were important predictors of use by the three most abundant species; dippers, kingfishers, and great blue herons. Monitoring programs to assess populations of these species in mountainous habitat must be sensitive to the potential effects of stream order, basin, and season and encompass a large spatial and temporal extent

Use of small streams and forest gaps for breeding habitats by winter wrens in Coastal British Columbia
About this Resource: Few studies have examined the value of riparian areas adjacent to streams <=10-m wide as habitat for forest birds. In mature (80-120 years) and young (40-60 years) coastal forests of southern British Columbia, Canada, we examined the habitat values for male winter wrens [Troglodytes troglodytes] of riparian areas adjacent to small streams and areas upslope of these streams. In both riparian and upslope areas, wrens preferentially located nests (n=47) and song perches (n=77) in disturbed sites with fewer trees than randomly located sites. Hydrological processes associated with streams, mortality of dominant canopy trees or uprooted trees can produce these disturbed sites. In mature forest, winter wrens chose stream banks and upturned root masses when available for building their nests with most nest substrates located within 5 m of small streams. In both young and mature forests, they also chose areas near small streams as locations for song perches. Winter wrens may use areas closer to streams when available because channel morphology, the associated heterogeneous forest structure, and microclimate likely provide optimal nesting and foraging habitat. Our research supports operational efforts by forest managers to conserve structures near small streams and in upslope areas because these structures maintain long-term habitat values for wildlife such as winter wrens.

Forestry and the aquatic environment: studies in an Irish context
About this Resource: Research on the interaction between plantation forestry and aquatic environments is essential to develop environmentally compatible and sustainable management further. Given, in Ireland, the generally low levels of atmospheric pollution, its geology and maritime climate, and the unique fauna and flora due to its island history, such studies are important not only in the regional context, but also internationally, as they provide an opportunity to examine the effect of forestry and forest management practices on aquatic systems per se, without the complications of acidification. Here, some of the major findings of forestry and water research in Ireland have been reviewed and compared with those from the UK and elsewhere. Plantation forests do not exacerbate acidification in the south of Ireland (Munster) as a whole so that the influence of forestry on water chemistry is far less important than in other parts of the country (such as Wicklow and Mayo). The main forestry influence on streams in Munster is more likely through physical factors, but their nature is unclear. In a few catchments some negative effects are evident, but in many others apparently positive forest effects occur. In this context, smaller scale catchment-level effects appear to be more important in explaining the various relationships between plantation forests and stream ecology than larger scale regional factors. The management of riparian zones, particularly in forested catchments, is of major importance for the structure and functioning of aquatic communities and further work is needed on best management practices. It is suggested that it is unreasonable to base forest management on national Forest-Fisheries guidelines since regions vary too much and the signal from local conditions is too strong. The approach for environmentally benign, scientifically sound forestry management has to be at the catchment scale. Trees in the right places may be beneficial ecologically but further work is needed to identify these locations. The introduction of new forest management practices such as adoption of new species mixes and continuous forest cover are at an early stage in Ireland and their influence on aquatic systems is unknown. Keywords: forest-stream interactions, Irish plantation forestry, hydrochemistry, macroinvertebrates, salmonids, forest management

Landscape elements and river chemistry as affected by river regulation – a 3-D perspective
About this Resource: We tested the hypothesis whether individual land classes within a river catchment contribute equally to river loading with dissolved constituents or whether some land classes act as &quot;hot spots&quot; to river loading and if so, are these land classes especially affected by hydrological alterations. The amount of land covered by forests and wetlands and the average soil depth of a river catchment explain 58–93% of the variability in total organic carbon (TOC) and dissolved silicate (DSi) concentrations for 22 river catchments in Northern Sweden. Whereas only 3% of the headwater areas of the Luleälven have been inundated by the creation of reservoirs, some 10% of the soils and aggregated forest and wetland areas have been lost due to damming and further hydrological alteration such as bypassing entire sub-catchments by headrace tunnels. However, looking at individual forest classes, our estimates indicate that some 37% of the deciduous forests have been inundated by the four major reservoirs built in the Luleälven headwaters. These deciduous forest and wetlands formerly growing on top of alluvial deposits along the river corridors forming the riparian zone play a vital role in loading river water with dissolved constituents, especially DSi. A digital elevation model draped with land classes and soil depths which highlights that topography of various land classes acting as hot spots is critical in determining water residence time in soils and biogeochemical fluxes. Thus, headwater areas of the Luleälven appear to be most sensitive to hydrological alterations due to the thin soil cover (on average 2.7–4.5 m) and only patchy appearance of forest and wetlands that were significantly perturbed. Moreover, since these headwater areas are characterized often by high specific discharge, this relatively minor change in the landscape when compared to the entire river catchment may indeed explain the significant lower fluxes at the river mouth.

Distributions of rare mollusks relative to reserved lands in Northern California
About this Resource: In 1994 the Northwest Forest Plan identified several hundred relatively rare plant and animal species as "Survey and Manage" based in part on their presumed association with late-successional/old-growth forests. Other such species were given protection from grazing. However, broad-scale surveys for few of these species existed at that time. In 1999-2000 we evaluated the relationship of nine terrestrial molluscs (Ancotrema voyanum, Helminthoglypta herleini, H. talmadgei, Monadenia chaceana, M. churchi, M. fidelis klamathica, M. fidelis ochromphalus, Prophysaon dubium and Trilobopsis tehamana) to US Forest Service reserves in four National Forests in northern California. The nine molluscs were well distributed among reserved and non-reserved lands and showed no association with Late Successional Reserves, Congressionally Reserved, Administratively Withdrawn, or Matrix land allocations. However, the molluscs occurred more frequently than expected in Riparian Reserves when all other land allocations were combined. Our results are a step toward evaluating the protection that the Northwest Forest Plan affords these molluscs in northern California.

Forest Practices Code Guidebooks | Ministry of Forests - Government of British Columbia
About this Resource: The Ministry of Forests (Government of British Columbia) provides a series of practical forestry related guidebooks. Offerings are categorized: bark beetle management; biodiversity; boundary marking; channel assessment procedures;community watersheds; defoliator management; and dwarf mistletoe management. There are guidebooks for specific forest regions; the rest involve: fish streams; forest development; forest roads; generic forest health; wildlife management; landscape units; terminal weevils; pine stem rust; pruning; riparian management; root disease management; seed and vegetative material; silviculture prescription; soil conservation; soil rehabilitation; stand management; trails; tree wounding and decay; visual imapct assessment and watershed assessment.

Bird communities in oak woodlands of Southcentral Washington
About this Resource: This study was initiated because there was a perception that oak woodlands are unique habitats for birds, particularly Neotropical migrants. The objectives of this study were to determine the species composition and relative abundance of bird populations in oak [Quercus] and oak-conifer woodlands; and to evaluate the importance of these habitats to nesting birds. This study was undertaken near the northern limit of the Garry oak (Q. garryana) habitat in North America. The study design consisted of three replicates each of five upland habitats (large pine-large oak, small pine-small oak, large Douglas fir-large oak, mostly pure large oak, and mostly pure small oak) and three riparian habitats (White Salmon River, Klickitat River and areas near Goldendale) in Washington, USA. Seventy-two bird species (53 Neotropical migrants and 19 permanent residents) were found at least twice on the 18 study sites. There were no significant differences in species richness among upland habitats. An average of 12 neotropical migrant species were detected per study site in both upland and riparian areas. Neotropical species comprised 62% of all birds detected. Bird abundance was highest in study sites with large amounts of small oak and small pine; it was lowest in riparian study sites. The most abundant species was the Nashville warbler (Vermivora ruficapilla). Bird species composition in the Washington Garry oak habitat was different from those previously reported from Oregon and California.

Landscape elements and river chemistry as affected by river regulation – a 3-D perspective
About this Resource: We tested the hypothesis whether individual land classes within a river catchment contribute equally to river loading with dissolved constituents or whether some land classes act as "hot spots" to river loading and if so, are these land classes especially affected by hydrological alterations. The amount of land covered by forests and wetlands and the average soil depth (throughout this paper soil refers to everything overlying bedrock i.e. regolith) of a river catchment explain 58–93% of the variability in total organic carbon (TOC) and dissolved silicate (DSi) concentrations for 22 river catchments in Northern Sweden. For the heavily regulated Luleälven, with 7 studied sub-catchments, only 3% of the headwater areas have been inundated by reservoirs, some 10% of the soils and aggregated forest and wetland areas have been lost due to damming and further hydrological alteration such as bypassing entire sub-catchments by headrace tunnels. However, looking at individual forest classes, our estimates indicate that some 37% of the deciduous forests have been inundated by the four major reservoirs built in the Luleälven headwaters. These deciduous forest and wetlands formerly growing on top of alluvial deposits along the river corridors forming the riparian zone play a vital role in loading river water with dissolved constituents, especially DSi. A digital elevation model draped with land classes and soil depths which highlights that topography of various land classes acting as hot spots is critical in determining water residence time in soils and biogeochemical fluxes. Thus, headwater areas of the Luleälven appear to be most sensitive to hydrological alterations due to the thin soil cover (on average 2.7–4.5 m) and only patchy appearance of forest and wetlands that were significantly perturbed. Hydrological alterations of these relatively small headwater areas significantly impacts downstream flux of dissolved constituents and their delivery to receiving water bodies.

Nitrogen uptake in riparian plant communities across a sharp ecological boundary of salmon density
About this Resource: Abstract Background Recent studies of anadromous salmon (Oncorhynchus spp.) on the Pacific Coast of North America indicate an important and previously unrecognized role of salmonid nutrients to terrestrial biota. However, the extent of this uptake by primary producers and consumers and the influences on community structure remain poorly described. We examine here the contribution of salmon nutrients to multiple taxa of riparian vegetation (Blechnum spicant, Menziesii ferruginea, Oplopanax horridus, Rubus spectabilis, Vaccinium alaskaense, V. parvifolium, Tsuga heterophylla) and measure foliar &#948;15N, total %N and plant community structure at two geographically separated watersheds in coastal British Columbia. To reduce potentially confounding effects of precipitation, substrate and other abiotic variables, we made comparisons across a sharp ecological boundary of salmon density that resulted from a waterfall barrier to salmon migration. Results &#948;15N and %N in foliage, and %cover of soil nitrogen indicators differed across the waterfall barrier to salmon at each watershed. &#948;15N values were enriched by 1.4&#8240; to 9.0&#8240; below the falls depending on species and watershed, providing a relative contribution of marine-derived nitrogen (MDN) to vegetation of 10% to 60%. %N in foliar tissues was slightly higher below the falls, with the majority of variance occurring between vegetation species. Community structure also differed with higher incidence of nitrogen-rich soil indicator species below the waterfalls. Conclusions Measures of &#948;15N, %N and vegetation cover indicate a consistent difference in the riparian community across a sharp ecological boundary of salmon density. The additional N source that salmon provide to nitrogen-limited habitats appears to have significant impacts on the N budget of riparian vegetation, which may increase primary productivity, and result in community shifts between sites with and without salmon access. This, in turn, may have cascading ecosystem effects in forests adjacent to salmon streams.

Influence of forest age on densities of Cope's and Pacific giant salamanders
About this Resource: We surveyed first-order streams in forest stands 0-94 yr old on industrial timberlands in the Cascade Mountains of southern Washington, USA, during the summer of 1998 and 1999 to determine how short-term changes in forest age can affect the abundance of the stream-breeding Cope's (Dicamptodon copei) and Pacific giant (D. tenebrosus) salamanders. Based on results from cross-validated regression trees, densities of both species were unrelated to changes in forest age or any other habitat variable measured. There was also no difference in any of the measured habitat variables between streams in which a species was present and streams in which it was not detected. However, densities of the Pacific giant salamander were negatively correlated to percent of riparian canopy cover in one of the years.

Ecología y distribución de Senecio pterophorus (Compositae) en la Península Ibérica
About this Resource: Field survey in Catalonia (Spain) has increased the known distribution and the number of populations of the South African daisy Senecio pterophorus DC. in the Iberian Peninsula and mainland Europe. The species colonizes relatively disturbed habitats such as river beds, road borders and disturbed helm-oak communities with no limitation in light and water. The analysis of population structure related to habitat type has revealed that in riparian and ruderal areas populations are large and well-established, with a large number of members per age class. However, in disturbed forests populations have only a few scattered adults. Senecio pterophorus also shows great morphological plasticity related with habitat type: in open environments plants are shorter, adopt a spherical habit, and have smaller leaves than in forests, where they are taller and have leaves twice in size. This species may be considered as invasive in the Iberian Peninsula and mainland Europe, where it has rapidly spread in recent years. Furthermore, we suggest that S. pterophorus may be a threat to native species and habitat diversity as occurs in Australia, where the species displaces the native plants and hybridizes with some native Senecio species.En este trabajo se describen el área de distribución y el número de poblaciones de la especie sudafricana Senecio pterophorus DC. en Cataluña, única área de la Europa continental de donde hasta ahora se conoce. Esta especie coloniza ambientes perturbados, como lechos de ríos, márgenes de carreteras y áreas forestales perturbadas, siempre que no haya limitación por la luz y la humedad. En los hábitats riparios y ruderales las poblaciones son más estables y densas, con un gran número de individuos de diversas clases de edad, mientras que en ambientes forestales las poblaciones suelen contar con pocos individuos adultos distribuidos de forma dispersa. Senecio pterophorus presenta, además, una acusada plasticidad morfológica en relación con el hábitat, de modo que en ambientes riparios y ruderales los individuos desarrollan un porte esférico, de menor tamaño, y unas hojas más pequeñas que en ambientes forestales, donde el porte de las plantas es más alargado y el tamaño de las hojas mucho mayor. Esta especie, en creciente expansión, debe ser considerada una planta invasora en la Península Ibérica, ya que ha aumentado considerablemente el número de sus poblaciones en un período relativamente corto. Además, se sugiere que S. pterophorus puede llegar a ser una amenaza para la conservación de la diversidad de especies y de hábitats naturales autóctonos, como ocurre en Australia, donde desplaza a las especies nativas e incluso se hibrida con otras especies de Senecio.

Historical trends in willow cover along streams in a Southwestern Montana cattle allotment
About this Resource: Concern over the apparent scarcity of tall willows [Salix sp.] prompted changes in livestock grazing management in a southwestern Montana mountain valley to avoid degradation of riparian and aquatic habitats. We assessed potential improvement in the abundance of tall willows following implementation of a new management strategy by determining the effect of historic grazing patterns on willow canopy along streams within the USDA Forest Service Long Creek cattle grazing allotment. The study area was dominated by Salix geyerana, S. boothii, Carex spp., and Poa pratensis. Willow canopy cover by stream reach was measured from aerial photos taken in 1942, 1965, and 1987. Cover from each year was compared for change over the 46-year record. Willow canopy cover fluctuated along the streams in the allotment, but the general trend was upward from 1942 to 1987. Willow stem population demography was evaluated to ascertain whether historic grazing patterns had affected stem replacement. Stem age classes were normally distributed with a replacement cycle similar to those reported in other areas of the western USA and Canada. These data sets suggest that extended periods of rest (>3 years) are not necessary for willow recovery if livestock or wildlife use is closely controlled.

Developing a Methodology to Prioritize Texas Watersheds for Environmental Restoration Efforts
About this Resource: During the past 150 years, several Texas watersheds have undergone significant changes that affect land use, the amount of water flowing through these systems, water quality, and the numbers and types of fish and aquatic species that live in rivers and lakes (McKinney, 2002). For the most part, these changes can be attributed to human activities such as dam building and reservoir management, population growth and resulting increased water use, increased runoff from paved surfaces, the introduction of non-native plant species, and others (Jensen, 2003a). As a consequence, competition for waters between human uses and environmental purposes has now increased to such an extent that some habitats and ecosystems that rely on water may be in peril, especially in semiarid and arid regions of Texas (TWDB, 2002). Recently, there has been increased public interest in investigating whether policies and management strategies could be implemented to restore watersheds, riparian zones, and other natural areas critically important to support wildlife, fisheries, and forests (Brown, 2000 and Alnwick, 2003). Often, the goal is to restore these sites to conditions that approximate conditions that existed prior to intensive human settlement in the 1800s. Interest in restoring watersheds and ecosystems has been expressed by several agencies including the U.S. EPA (2000 and 2001) and the U.S. Fish and Wildlife Service (2000). At a local or regional level, efforts have been undertaken to identify restoration opportunities along the Texas Gulf Coast by General Land Office Natural Resources Inventory program (1998). In addition, organizations including the Nature Conservancy (2000), the National Wildlife Federation (1998), and the Galveston Bay Foundation (19980 have also examined the need to set priorities for environmental restoration. For example, the Nature Conservancy published a report, Designing a Geography of Hope (Groves et al, 2000), that describes one method of assessing restoration opportunities across ecosystems and watersheds. A special challenge facing restoration efforts is in developing management strategies that will benefit ecological conditions in watersheds while, at the same time, preserving existing land uses (including homes and businesses) as well as dams and other infrastructure. Activities to identify estuaries and other watersheds that may be in need of restoration efforts have been initiated by the U.S. Army Corps of Engineers (2000) and the National Oceanic and Atmospheric Administration (2002). To deal with these public concerns, the U.S. Army Corps of Engineers Fort Worth District Office has expressed interest in determining how watershed restoration programs could be designed and implemented. One of the primary needs in this regard is to develop a science-based process that could objectively evaluate, prioritize, and identify watersheds that most need restoration efforts as well as regions where these measures are most likely to succeed. If such a methodology were developed, the Corps could use these recommendations, in conjunction with non-Federal sponsors, to develop full-fledged feasibility studies within targeted watersheds. Obviously, such a method could potentially be used by other natural resources agencies and organizations in Texas and elsewhere. It should be noted that the Corps is already engaged in ecosystem restoration studies and projects in some parts of Texas, though these efforts are developed as a part of comprehensive Corps projects. Some of these Texas projects include efforts in San Antonio (Salado Creek), Dallas, Houston, the North Bosque River watershed, and other regions. This project seeks to create a methodology that can be used to prioritize watersheds throughout Texas for possible restoration projects, the feasibility of which would be determined in subsequent detailed studies. Environmental operating principles that should guide the Corps in its public works and water resources projects were identified in a March 2002 speech in Louisiana by Lt. General Robert Flowers (Corps of Engineers, 2002). Some of the main points he addressed include the following: * The Corps should strive to achieve environmental sustainability, * Balance should be sought between human activities and natural systems * Potential problems should be resolved by designing environmental and economic solutions that complement one another. * The Corps should seek ways to assess and mitigate potential adverse affects caused by Corps of Engineers projects on the environment.

Water table dynamics and soil texture of three riparian plant communities
About this Resource: Restoration of degraded riparian plant communities must consider relationships among water table dynamics, soil texture, and plant species. Water table dynamics, soil texture, and slope were compared among riparian plant communities dominated by: (1) beaked sedge (Carex rostrata), (2) Geyer's willow (Salix geyeriana [S. geyerana]), and (3) black cottonwood (Populus trichocarpa [Populus balsamifera subsp. trichocarpa]) occurring on recent alluvial bars. Six sites in western Montana (USA) were examined for each plant community type. Mean bimonthly fluctuation in water table depth did not differ among the 3 plant communities (P=0.67), but mean depth to water table was greatest (P=0.004) in the cottonwood community (62.8 cm), intermediate for the willow (32.0 cm) and least for sedge communities (20.7 cm). Soil texture differed among the 3 plant communities for sand (P=0.0004), silt (P=0.0002), and clay (P=0.003). Cottonwood communities occurred on soils that averaged 78% sand, whereas sedge and willow sites averaged 47% sand and 35% sand, respectively. Silt content was 40% beneath willow, 35% beneath sedge and 15% beneath cottonwood communities. Soils of the willow sites averaged 25% clay compared with 18% and 7% for sedge and cottonwood communities, respectively. Soils beneath all 3 plant communities differed in coarse fragment percentage (P=0.01), averaging 46% in cottonwood, 22% in willow, and 15% in sedge sites. No differences were found in slope among the 3 plant communities, either parallel to the stream (P=0.76) or perpendicular to the stream (P=0.29). Thus, these plant species exhibit a more narrow affinity for soil texture, coarse fragment content and water table depth than previously reported.

Vegetation patterns and abundances of amphibians and small mammals along small streams in a Northwestern California watershed
About this Resource: Our goal was to describe and evaluate patterns of association between stream size and abundances of amphibians and small mammals in a watershed in northwestern California, USA. We sampled populations at 42 stream sites and eight upland sites within a 100-km2 watershed in 1995 and 1996. Stream reaches sampled ranged from poorly defined channels that rarely flowed to 10-m-wide channels with perennial flow. The majority of reaches flowed only intermittently. Aquatic vertebrates were sampled by conducting area-constrained surveys, and terrestrial vertebrates were sampled along three 45-m-long transects using cover boards, drift fence/pitfall trap arrays, and two types of live trap. Vegetation characteristics (including basal area of live trees by species, ground cover, shrub cover and numbers of logs) were strongly associated with measures of stream size, especially channel width. Compared to upland sites, mean numbers of plant species in the herbaceous layer were significantly greater along streams with active channel widths as small as 0.9-1.3 m. Larval Pacific giant salamanders (Dicamptodon tenebrosus) were found only in stream reaches with continuous flow or in channels >=2.4-m wide, and larval tailed frogs (Ascaphus truei) were found only at sites with continuous or nearly continuous flow. Allen's chipmunks (Tamias senex) and deer mice (Peromyscus maniculatus) occurred at nearly every site sampled but were more abundant at reaches along larger streams than at reaches along smaller streams or at upland sites. None of the vertebrate species evaluated was significantly associated with intermittent streams having channels less than about 2-m wide and drainage areas less than about 10 ha. Our results provide additional information on the ecological role of small, intermittent streams.

Influence of partial harvesting on stream temperatures, chemistry, and turbidity in forests on the Western Olympic Peninsula, Washington
About this Resource: Stream temperatures, chemistry and turbidity were monitored in two partially harvested (7-33%) watersheds, Rock and Tower creeks, and an uncut old-growth watershed, West Twin Creek in the Hoh River Valley on the Olympic Peninsula, Washington. Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) was replanted in the harvested areas and red alder (Alnus rubra Bong.), a nitrogen fixer, dominated the riparian areas in the sampling sites on Rock and Tower creeks. We collected grab stream water samples monthly, from May 1996 to June 1998 and analyzed them for pH, electrical conductivity, total N and P, and major cations and anions. Stream temperatures were monitored continuously and turbidity was monitored monthly from May 1997 to June 1998. Partial harvesting had little influence on stream temperature, chemistry and turbidity 11-15 years after harvesting. Stream temperatures were more seasonally variable in the harvested streams compared to the unharvested old-growth site with an average summertime maximum elevated by 3.5degreeC. Maximum stream temperatures did not exceed 16degreeC in any stream and therefore salmonid species are not likely to be affected. There were significant differences in concentrations of some cations, anions and EC between the old-growth and the partially harvested watershed streams, but in most cases concentrations were actually higher in the unharvested watershed. Nitrate concentrations and stream turbidity were not significantly higher in the harvested watersheds