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Browse subject: primary forests
Number of records: 131

Inorganic and organic phosphorus pools in earthworm casts (Glossoscolecidae) and a Brazilian rainforest Oxisol
About this Resource: We compared differences in soil phosphorus fractions between large earthworm casts (Family Glossoscolecidae) and surrounding soils, i.e., Oxisols in 10 year-old upland agroforestry system (AGR), pasture (PAS), and secondary forest (SEC) in the Central Brazilian Amazon. AGR and PAS both received low-input fertilization and SEC received no fertilization. We found that earthworm casts had higher levels of organic hydroxide P than surrounding soils, whereas fertilization increased inorganic hydroxide P. Inorganic P was increased by fertilization, and organic P was increased by earthworm gut passage and/or selection of ingested materials, which increased available P (sum of resin and bicarbonate fractions) and moderately available P (sum of hydroxide and dilute acid fractions), and P fertilizer application and land-use increased available P. The use of a modified sequential P fractionation produced fewer differences between earthworm casts and soils than were expected. We suggest the use of a condensed extraction procedure with three fractions (Available P, Moderately Available P, and Resistant P) that provide an ecologically based understanding of the P availability in soil. Earthworm casts were estimated to constitute 41.0, 38.2, and 26.0 kg ha-1 of total available P stocks (sum of resin and bicarbonate fractions) in the agroforestry system, pasture, and secondary forest, respectively.

Forage evapotranspiration and photosynthetically active radiation interception in proximity to deciduous trees
About this Resource: Practically all of the extensive body of research on evapotranspiration (ET) in agricultural systems has been done for open fields. There is a lack of information on how the microclimate variability within silvopasture systems affects water requirements of forages. Small 26cm diameter, 23cm deep lysimeters planted with either orchardgrass (Dactylis glomerata L.) or tall fescue (Schedonorus phoenix (Scop.) Holub) were placed in the ground along the north and south edge of two 15m widex50m deep notches cleared into a mature second growth hardwood forest. One notch opened to pasture on the east receiving more early day solar radiation and one to pasture on the west receiving more wind and late day solar radiation. There was no significant difference in ET between orchardgrass and tall fescue. North edges, receiving more direct beam radiation, had significantly higher ET (39%) than south edges which received a higher percentage of diffuse radiation. The west notch had significantly higher ET (11%) than the east notch. At the sunniest sites, advection provided 20% of the energy used for ET while at the shadiest sites it provided more than half (56%) with the rest provided by incident solar radiation. Dates where photosynthetically active radiation (PAR) was restricted by clouds resulted in decreased ET relative to PAR compared to more sunny days. However, sites where PAR was restricted by tree shade had higher ET relative to PAR than more open sites. These results indicate tree modification of microclimate does not decrease forage ET to the extent that PAR is decreased.

Secondary Forest Succession and Tree Planting at the Laguna Cartagena and Cabo Rojo Wildlife Refuges in Southwestern Puerto Rico
About this Resource: Secondary forest succession and tree planting are contributing to the recovery of the Cabo Rojo refuge (Headquarters and Salinas tracts) and Laguna Cartagena refuge (Lagoon and Tinaja tracts) of the Fish and Wildlife Service in southwestern Puerto Rico. About 80 species, mainly natives, have been planted on 44 ha during the past 25 y in an effort to reduce the threat of grass fires and to restore wildlife habitat. A 2007 survey of 9-y-old tree plantings on the Lagoon tract showed satisfactory growth rates for 16 native species. Multiple stems from individual trees at ground level were common. A sampling of secondary forest on the entire 109 ha Tinaja tract disclosed 141 native tree species, or 25% of Puerto Rico's native tree flora, along with 20 exotics. Five tree species made up about 58% of the total basal area, and seven species were island endemics. Between 1998 and 2003, tree numbers and basal area, as well as tree heights and diameter at breast height values (diameter at 1.4 m above the ground), increased on the lower 30 ha of the Tinaja tract. In this area, much of it subject to fires and grazing through 1996, exotic trees made up 25% of the species. Dry forest throughout the tropics is an endangered habitat, and its recovery (i.e., in biomass, structure, and species composition) at Tinaja may exceed 500 y. Future forests, however, will likely contain some exotics.

Radiation use efficiency in adjacent hardwood and pine forests in the southern Appalachians
About this Resource: The efficiency with which trees convert photosynthetically active radiation (PAR) to biomass has been shown to be consistent within stands of an individual species, which is useful for estimating biomass production and carbon accumulation. However, radiation use efficiency (ε) has rarely been measured in mixed-species forests, and it is unclear how species diversity may affect the consistency of ε, particularly across environmental gradients. We compared aboveground net primary productivity (ANPP), intercepted photosynthetically active solar radiation (IPAR), and radiation use efficiency (ε =ANPP/IPAR) between a mixed deciduous forest and a 50-year-old white pine (Pinus strobus L.) plantation in the southern Appalachian Mountains. Average ANPP was similar in the deciduous forest (11.5Mgha⁻¹ y⁻¹) and pine plantation (10.2Mgha⁻¹ y⁻¹), while ε was significantly greater in the deciduous forest (1.25gMJ⁻¹) than in the white pine plantation (0.63gMJ⁻¹). Our results demonstrate that late-secondary hardwood forests can attain similar ANPP as mature P. strobus plantations in the southern Appalachians, despite substantially less annual IPAR and mineral-nitrogen availability, suggesting greater resource-use efficiency and potential for long-term carbon accumulation in biomass. Along a 260m elevation gradient within each forest there was not significant variation in ε. Radiation use efficiency may be stable for specific forest types across a range of environmental conditions in the southern Appalachian Mountains, and thus useful for generating estimates of ANPP at the scale of individual watersheds.

Long-term development of above- and below-ground carbon stocks following land-use change in subalpine ecosystems of the Swiss National Park
About this Resource: Vegetation changes following agricultural land abandonment at high elevation --- which is frequent in Europe --- could have a major impact on carbon (C) sequestration. However, most information on the effects of vegetation changes on ecosystem C stocks originates from low-elevation studies on reforestation or early successional forests, and little is known about how these stocks change during long-term secondary forest succession and at high elevation. We assessed aboveground, belowground, and ecosystem organic matter and C stocks in high-elevation ecosystems that represent the long-term development (centuries) following land abandonment: short- and tall-grass pastures, Swiss mountain pine (Pinus mugo Turra), mixed-conifer, and Swiss stone pine (Pinus cembra L.) -- European larch (Larix decidua P. Mill.) forests. Aboveground C stocks were lowest in the short-grass pastures (0.1 Mg C·ha-1) and reached a maximum in the mixed-conifer and stone pine - larch forests (166 Mg C·ha-1). Belowground C stocks did not differ among the ecosystems studied. We only detected ecosystem C sequestration during reforestation; whereas no significant differences in ecosystem C stocks were found during long-term secondary forest development. Our calculations showed that only an additional 1733-3032 Mg C·year-1 would be sequestered owing to natural reforestation in high-elevation Switzerland, which likely can be considered negligible compared with total annual C sequestration calculated for Swiss forests in other studies.

Influence of Forest Management and Previous Herbivory on Cattle Diets
About this Resource: Grazing cattle and timber harvest are common practices associated with forested rangelands. Therefore, the objective was to document the effects of timber harvest and herbivory on nutritional quality and botanical composition of steer diets in grand fir (Abies grandis [Dougl. ex D. Don] Lindl.) and ponderosa pine (Pinus ponderosa P. & C. Lawson) forests. Three replicated grand fir sites were arranged as a split-plot design; timber harvest treatments--1) no harvest (CON), 2) thinning (TH), 3) clearcut (CL)--were whole plots, and herbivory treatments--1) large ungulate grazing (Graze), 2) wild ungulate grazing (CExc), and 3) exclusion of large ungulate grazing (TExc)--were the subplots. Three replicated ponderosa pine sites were arranged as a split-plot design; timber harvest treatments--1) CON and 2) TH--were whole plots, and herbivory treatments--1) GR, 2) BG, and 3) EX--were subplots. Diet samples were collected in June and August of 2001 and 2002. Crude protein, in vitro organic matter digestibility, acid detergent fiber, and neutral detergent fiber of the diets were only affected by season of use and were higher (P<0.05) quality during the June grazing period. Botanical composition of diets was determined with the use of microhistological analysis of ruminal masticate. Within grand fir sites, graminoids were the major constituent in the diet (65%-91%), forbs intermediate (8%-31%), and shrubs least (0.2%-3.5%). Within ponderosa pine sites graminoids were the major constituent in the diet (83%-88%), forbs intermediate (10%-14%), and shrubs least (2%-3%). Season of use did not affect (P>0.10) botanical composition in either grand fir or ponderosa pine sites. Timing of grazing had a greater influence on diet quality; however, previous herbivory and(or) timber harvest had a greater influence on composition of diets than did timing of grazing.

Land Application of Carbonatic Lake-Dredged Materials: Effects on Soil Quality and Forage Productivity
About this Resource: The ability to reuse carbonatic lake-dredged materials (CLDM) for agricultural purposes is important because it reduces offshore disposal and provides an alternative to disposal of the materials in landfills that are already overtaxed. A four-year (2001 to 2005) study on land application of CLDM as an option for disposal was conducted on a beef cattle pasture in south central Florida. The objectives of this study were (i) to assess CLDM as a soil amendment to improve quality of sandy soils in most subtropical beef cattle pastures and (ii) to determine the effect of CLDM on productivity and nutritive values of bahiagrass (BG, Paspalum notatum Flugge) in subtropical beef cattle pasture. The five treatment combinations arranged in randomized complete block design were represented by plots with different ratios (R) of natural soil (NS) to CLDM: R1 (1000 g kg-1:0 g kg-1); R2 (750 g kg-1:250 g kg-1); R3 (500 g kg-1:500 g kg-1); R4 (250 g kg-1:750 g kg-1); and R5 (0 g kg-1:1000 g kg-1). Addition of CLDM had significant (p < or = 0.001) effects on soil quality and favorable influence on forage establishment and nutritive values. Compared with the control plots (0 g kg-1), the soils in plots amended with CLDM exhibited (i) lower penetration resistance, (ii) an increase in soil pH and exchangeable cations (Ca and Mg), and (iii) decrease in the levels of soil trace metals (Mn, Cu, Fe, Zn, and Si). Results disclosed consistently and significantly (p < or = 0.001) higher BG biomass production (forage yield = -106.3x2 + 1015.8x - 39.2; R2 = 0.99**) and crude protein content (CP = 1.24x + 6.48; R2 = 0.94**) from plots amended with CLDM than those of BG planted on plots with no CLDM treatment.

Nitrogen drives the growth of secondary forests in the Amazon: what analogies with temperate and boreal forests?
About this Resource: Nitrogen drives the growth of secondary forests in the Amazon: what analogies with temperate and boreal forests? A comment is made on a recent paper published on Nature (Davidson et al. 2007), in which the authors demonstrate that in the young secondary forests in the Amazon a conservative nitrogen cycle prevails and nitrogen is a key factor driving forest growth. Analogies are also discussed with recent findings on the role of nitrogen deposition on the carbon balance of temperate and boreal forests (Magnani et al. 2007).

A NOTE ON HIGH DISCOUNT RATES AND DEPLETION OF PRIMARY FORESTS
About this Resource: Conventional wisdom implies that high discount rates accelerate depletion of tropical forests. As shown in this article, this result does not necessarily hold in a two-state variable model that distinguishes between primary and secondary forest stocks. In the context of a fixed concession period and imperfect government control, logging of primary forests may be both accelerated and depressed as discount rates increase.

Distribution of sandflies (Diptera: Phlebotominae) in forest remnants and adjacent matrix habitats in Brazilian Amazonia
About this Resource: We studied the distribution of sandflies (Diptera: Phlebotominae) - insect vectors of several diseases, including leishmaniasis - at the interface between primary forest and cattle pasture and between primary forest and secondary forest (< 15 yr old) in Southern Brazilian Amazonia. Sandflies were collected by using a combination of light traps and traps having vertebrates as baits. Strong differences in abundance and species richness were found between primary forests and pastures. Very few sandfly species were found in the pastures, and those that were found generally occurred at lower densities when compared to the adjacent forest. At least one species (Lutzomyia lainsoni), however, can become extremely abundant in pastures, possibly depending on the presence of cattle and water bodies. Differences between primary forests and secondary forests were not so strong, although the latter usually had fewer species and lower population abundances. No species were exclusively found in pastures or secondary forests; the species present in these two habitats were a subset of those found in primary forests. The distance to the edge did not affect the abundance, richness and composition of sandfly species in primary forests. The abundance and richness of sandflies, however, was greater in forest edges facing pastures than those facing secondary forests. This pattern could not be explained by an influx of species and individuals from the adjacent pasture, suggesting the existence of in situ differences between the different types of forest edges studied.

ECONOMIC VALUE OF THE CARBON SINK SERVICES OF TROPICAL SECONDARY FORESTS AND ITS MANAGEMENT IMPLICATIONS
About this Resource: This paper explores the economic feasibility secondary forest regeneration and conservation as an alternative to help address global warming. Detailed measurements of tropical secondary forests through time, in different ecological zones of Costa Rica, are used for estimating carbon storage models. The paper addresses key issues in the international discussion about cross- and within-country compensation for carbon storage services and illustrates a method to compute/predict their economic value through time under a variety of scenarios. The procedure is applicable to other developing countries where secondary forest growth is increasingly important.

Ancient Forest International
About this Resource: AFI works to protect primary forests around the world by helping to coordinate the purchase of ecologically critical forested land, primarily along the Pacific coast of North and South America. The site provides information about forest protection strategies, forest types, and their programs in California, Chile, and Ecuador.

Identification of protein functions using a machine-learning approach based on sequence-derived properties
About this Resource: Abstract Background Predicting the function of an unknown protein is an essential goal in bioinformatics. Sequence similarity-based approaches are widely used for function prediction; however, they are often inadequate in the absence of similar sequences or when the sequence similarity among known protein sequences is statistically weak. This study aimed to develop an accurate prediction method for identifying protein function, irrespective of sequence and structural similarities. Results A highly accurate prediction method capable of identifying protein function, based solely on protein sequence properties, is described. This method analyses and identifies specific features of the protein sequence that are highly correlated with certain protein functions and determines the combination of protein sequence features that best characterises protein function. Thirty-three features that represent subtle differences in local regions and full regions of the protein sequences were introduced. On the basis of 484 features extracted solely from the protein sequence, models were built to predict the functions of 11 different proteins from a broad range of cellular components, molecular functions, and biological processes. The accuracy of protein function prediction using random forests with feature selection ranged from 94.23% to 100%. The local sequence information was found to have a broad range of applicability in predicting protein function. Conclusion We present an accurate prediction method using a machine-learning approach based solely on protein sequence properties. The primary contribution of this paper is to propose new PNPRD features representing global and/or local differences in sequences, based on positively and/or negatively charged residues, to assist in predicting protein function. In addition, we identified a compact and useful feature subset for predicting the function of various proteins. Our results indicate that sequence-based classifiers can provide good results among a broad range of proteins, that the proposed features are useful in predicting several functions, and that the combination of our and traditional features may support the creation of a discriminative feature set for specific protein functions.

New records of Uroderma magnirostrum Davis (Mammalia, Chiroptera) from southeastern Brazil, with comments on its natural history
About this Resource: Uroderma magnirostrum Davis, 1968 is reported from four new localities in southeastern Brazil, significantly extending its geographical distribution south and westward. A total of 12 adult specimens collected in areas of Caatinga and Atlantic Forest in the states of Minas Gerais, Espírito Santo, and Rio de Janeiro, including specimens from the new localities and museum specimens were examined. Females from southeastern Brazil were larger than males in all external measurements analyzed, but after univariate statistical analyses using corrected p values for multiple tests no significant sexual dimorphism was detected. Mean values obtained from this sample fall within the known range documented for the species in both external and cranial measurements, and are similar to those found in specimens from north and northeastern Brazil. The habitats of the new localities of U. magnirostrum in southeastern Brazil ranged from pristine and secondary forests to a small urban park. Uroderma magnirostrum is apparently a rare species in southeast Brazil, which corroborates most previous reports of populations of this bat at other localities.

Large-scale prediction of long disordered regions in proteins using random forests
About this Resource: Abstract Background Many proteins contain disordered regions that lack fixed three-dimensional (3D) structure under physiological conditions but have important biological functions. Prediction of disordered regions in protein sequences is important for understanding protein function and in high-throughput determination of protein structures. Machine learning techniques, including neural networks and support vector machines have been widely used in such predictions. Predictors designed for long disordered regions are usually less successful in predicting short disordered regions. Combining prediction of short and long disordered regions will dramatically increase the complexity of the prediction algorithm and make the predictor unsuitable for large-scale applications. Efficient batch prediction of long disordered regions alone is of greater interest in large-scale proteome studies. Results A new algorithm, IUPforest-L, for predicting long disordered regions using the random forest learning model is proposed in this paper. IUPforest-L is based on the Moreau-Broto auto-correlation function of amino acid indices (AAIs) and other physicochemical features of the primary sequences. In 10-fold cross validation tests, IUPforest-L can achieve an area of 89.5% under the receiver operating characteristic (ROC) curve. Compared with existing disorder predictors, IUPforest-L has high prediction accuracy and is efficient for predicting long disordered regions in large-scale proteomes. Conclusion The random forest model based on the auto-correlation functions of the AAIs within a protein fragment and other physicochemical features could effectively detect long disordered regions in proteins. A new predictor, IUPforest-L, was developed to batch predict long disordered regions in proteins, and the server can be accessed from http://dmg.cs.rmit.edu.au/IUPforest/IUPforest-L.php

Rapid formation of isoprene photo-oxidation products observed in Amazonia
About this Resource: Isoprene represents the single most important reactive hydrocarbon for atmospheric chemistry in the tropical atmosphere. It plays a central role in global and regional atmospheric chemistry and possible climate feedbacks. Photo-oxidation of primary hydrocarbons (e.g. isoprene) leads to the formation of oxygenated VOCs (OVOCs). The evolution of these intermediates affects the oxidative capacity of the atmosphere (by reacting with OH) and can contribute to secondary aerosol formation, a poorly understood process. An accurate and quantitative understanding of VOC oxidation processes is needed for model simulations of regional air quality and global climate. Based on field measurements conducted during the Amazonian aerosol characterization experiment (AMAZE-08) we show that the production of certain OVOCs (e.g. hydroxyacetone) from isoprene photo-oxidation in the lower atmosphere is significantly underpredicted by standard chemistry schemes. A recently suggested novel pathway for isoprene peroxy radicals could explain the observed discrepancy and reconcile the rapid formation of these VOCs. Furthermore, if generalized our observations suggest that prompt photochemical formation of OVOCs and other uncertainties in VOC oxidation schemes could result in substantial underestimates of modelled OH reactivity that could explain a major fraction of the missing OH sink over forests which has previously been attributed to a missing source of primary biogenic VOCs.

Potential non-target risks from strychnine-containing rodent carcasses
About this Resource: Underground strychnine baiting is a common technique used to suppress pocket gopher (Thomomys sp.) populations until seedlings are established. Non-target risks from underground baiting can still occur if strychnine-baited animals die aboveground. Accordingly, the fate of strychnine-baited carcasses of four small mammal species, Thomomys, Mus, Microtus, and Peromyscus, were documented during four trials on the Rogue River National Forest. We found no difference among species and type of damage, either insect or predator, during the four trials. However, survival differed between species in two trials where fewer Thomomys carcasses survived until completion of the study. We also examined the risk to tertiary non-targets from insects collected at the sites. Strychnine concentration among insect groups from treated carcasses differed with Diptera larvae and ants consistently containing higher concentrations. Even with high strychnine concentrations (0.2756 microgram/g), risk assessments showed negligible tertiary risks from consuming strychnine-laced insects.

TREE COMMUNITY OF AN ALLUVIAL LOWLAND FOREST IN THE MUNICIPALITY OF CAMPOS DOS GOYTACAZES, RJ, BRAZIL
About this Resource: This study evaluated tree community structure and floristic composition of an alluvial lowland forest at Campos dosGoytacazes, north of Rio de Janeiro State, Brazil. Tree community (DBH 3.2 cm) was sampled using the Point Centered-Quarter(84 points, 336 trees). 105 species of 35 families were found. The richest families were Leguminosae (18 species), Euphorbiaceae (7),Lauraceae (6) and Rubiaceae (6). The values of basal area (17.3 m2.ha-1) and Shannon s species diversity (H = 4.02 nats.ind-1) weresimilar to others secondary forests in the region. When compared to other forest at the region, the Bom Jesus forest showed strongerfloristic relationships with semideciduous forests (Tabuleiro forests), especially those under the same climate and disturbanceconditions. Considering the extensively fragmented landscape and the ecological importance of this remnant for the maintenance of thetree species diversity in this region, this forest renmant should be among the priorities for conservation and management programs.

Western equatorial African forest-savanna mosaics: a legacy of late Holocene climatic change?
About this Resource: Past vegetation and climate changes reconstructed using two pollen records from Lakes Maridor and Nguène, Gabon, provide new insights into the environmental history of western equatorial African rainforests during the last 4500 cal yr BP. The Lake Maridor pollen record indicates that the coastal savannas of western equatorial Africa did not exist during the mid-Holocene and instead the region was covered by evergreen rainforests. In the Lake Nguène pollen record, a rapid decline of hygrophilous evergreen rainforest occurred around 4000 cal yr BP, synchronously with grassland expansion around Lake Maridor. The establishment of coastal savannas in Gabon suggests decreasing humidity at the onset of the late Holocene. The marked reduction in evergreen rainforest and subsequent savanna expansion was associated with the colonization of secondary forests dominated by the palm, &lt;i&gt;Elaeis guineensis&lt;/i&gt;, in the coastal region and the shrub, &lt;i&gt;Alchornea cordifolia&lt;/i&gt;, further inland. A return to wetter climatic conditions from about 1400 cal yr BP led to the renewed spread of evergreen rainforest inland, whereas a forest-savanna mosaic still persists in the coastal region. There is no evidence to suggest that the major environmental changes observed are driven by human impact.

Regional and temporal patterns of litterfall in tropical South America
About this Resource: The production of aboveground soft tissue represents an important share of total net primary production in tropical rain forests. Here we draw from a large number of published and unpublished datasets (&lt;i&gt;n&lt;/i&gt;=81 sites) to assess the determinants of litterfall variation across South American tropical forests. We show that across old-growth tropical rainforests, litterfall averages 8.61&plusmn;1.91Mg/ha/yr. Secondary forests have a lower annual litterfall than old-growth tropical forests with a mean of 8.01&plusmn;3.41 Mg/ha/yr. Annual litterfall shows no significant variation with total annual rainfall, either globally or within forest types. It does not vary consistently with soil type, except in the poorest soils (white sand soils), where litterfall is significantly lower than in other soil types (5.42&plusmn;1.91Mg/ha/yr). Litterfall declines significantly with increasing N:P. We also study the determinants of litterfall seasonality, and find that it does not depend on annual rainfall or on soil type. However, litterfall seasonality is significantly positively correlated with rainfall seasonality. Finally, we assess how much carbon is stored in reproductive organs relative to photosynthetic organs. Mean leaf fall is 5.74&plusmn;1.83 Mg/ha/yr (71% of total litterfall). Mean allocation into reproductive organs is 0.69&plusmn;0.40Mg/ha/yr (9% of total litterfall). The investment into reproductive organs divided by leaf litterfall is negatively related to the N:P ratio, suggesting that on poor soils, the allocation to photosynthetic organs is prioritized over that to reproduction. Finally, we discuss the ecological and biogeochemical implications of these results.

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.

Louisiana forest industries, 1973
About this Resource: Louisiana forests supplied more than 561 million cubic feet of roundwood to forest industries in 1973. Pulpwood and saw logs were the major products, accounting for 79 percent of the harvest. A total of 207 primary wood-using plants were in operation in 1973.

Mississippi forest industries, 1972
About this Resource: Mississippi forests supplied more than 559 million cubic feet of roundwood to forest industries in 1072. Pulpwood and saw logs were the major products, accounting for 85 percent of the harvest. A total of 315 primary wood-using plants were in operation in 1972.

Influence of the Forest Canopy on Total and Methyl Mercury Deposition in the Boreal Forest
About this Resource: Atmospheric mercury deposition by wet and dry processes contributes mercury to terrestrial and aquatic systems. Factors influencing the amount of mercury deposited to boreal forests were identified in this study. Throughfall and open canopy precipitation samples were collected in 2005 and 2006 using passive precipitation collectors from pristine sites located across the Superior National Forest in northern Minnesota, USA. Samples were collected approximately every 2 weeks and analyzed for total (THg) and methyl mercury (MeHg). Forest canopy type and density were the primary influences on THg and MeHg deposition. Highest THg and MeHg concentrations were measured beneath conifer canopies (THg mean = 19.02 ng L⁻¹; MeHg mean = 0.28 ng L⁻¹) followed by deciduous throughfall (THg mean = 12.53 ng L⁻¹; MeHg mean = 0.19 ng L⁻¹) then open precipitation (THg mean = 8.19 ng L⁻¹; MeHg mean = 0.12 ng L⁻¹). The greater efficiency of conifers at scavenging THg and MeHg from the atmosphere may increase the risk of mercury related water quality issues in conifer-dominated systems.

Prediction of DNA-binding residues from protein sequence information using random forests
About this Resource: Abstract Background Protein-DNA interactions are involved in many biological processes essential for cellular function. To understand the molecular mechanism of protein-DNA recognition, it is necessary to identify the DNA-binding residues in DNA-binding proteins. However, structural data are available for only a few hundreds of protein-DNA complexes. With the rapid accumulation of sequence data, it becomes an important but challenging task to accurately predict DNA-binding residues directly from amino acid sequence data. Results A new machine learning approach has been developed in this study for predicting DNA-binding residues from amino acid sequence data. The approach used both the labelled data instances collected from the available structures of protein-DNA complexes and the abundant unlabeled data found in protein sequence databases. The evolutionary information contained in the unlabeled sequence data was represented as position-specific scoring matrices (PSSMs) and several new descriptors. The sequence-derived features were then used to train random forests (RFs), which could handle a large number of input variables and avoid model overfitting. The use of evolutionary information was found to significantly improve classifier performance. The RF classifier was further evaluated using a separate test dataset, and the predicted DNA-binding residues were examined in the context of three-dimensional structures. Conclusion The results suggest that the RF-based approach gives rise to more accurate prediction of DNA-binding residues than previous studies. A new web server called BindN-RF http://bioinfo.ggc.org/bindn-rf/ has thus been developed to make the RF classifier accessible to the biological research community.

Modelling carbon cycle of agro-forest ecosystems in Lombardy (Italy)
About this Resource: In this paper we present a methodology for the estimation of Gross Primary Production (GPP), Net Primary Production (NPP) and Net Ecosystem Production (NEP) for the main agricultural and forest ecosystems of the Lombardia Region (Italy). The MOD17 model was parameterized according to the different agro-forestry ecosystems and applied at regional scale by using satellite data with a spatial resolution of 250m. The high spatial resolution along with fine classification agro-forestry ecosystems has allowed to accurately analyze the carbon budget of an extremely fragmented and complex environment such as the Lombardia Region. Modeling results showed the role of the forests in the carbon budget at regional scale and represent important information layer for the spatial analysis and for inferring the inter-annual variability of carbon sequestration due to impacts of extreme events and recent climate change (e.g., drought, heat wave, flooding, fires).

Scaling Gross Primary Production (GPP) over boreal and deciduous forest landscapes in support of MODIS GPP product validation
About this Resource: The Moderate Resolution Imaging Radiometer (MODIS) is the primary instrument in the NASA Earth Observing System for monitoring the seasonality of global terrestrial vegetation. Estimates of 8-day mean daily gross primary production (GPP) at the 1 km spatial resolution are now operationally produced by the MODIS Land Science Team for the global terrestrial surface using a production efficiency approach. In this study, the 2001 MODIS GPP product was compared with scaled GPP estimates (25 km2) based on ground measurements at two forested sites. The ground-based GPP scaling approach relied on a carbon cycle process model run in a spatially distributed mode. Land cover classification and maximum annual leaf area index, as derived from Landsat ETM+ imagery, were used in model initiation. The model was driven by daily meteorological observations from an eddy covariance flux tower situated at the center of each site. Model simulated GPPs were corroborated with daily GPP estimates from the flux tower. At the hardwood forest site, the MODIS GPP phenology started earlier than was indicated by the scaled GPP, and the summertime GPP from MODIS was generally lower than the scaled GPP values. The fall-off in production at the end of the growing season was similar to the validation data. At the boreal forest site, the GPP phenologies generally agreed because both responded to the strong signal associated with minimum temperature. The midsummer MODIS GPP there was generally higher than the ground-based GPP. The differences between the MODIS GPP products and the ground-based GPPs were driven by differences in the timing of FPAR and the magnitude of light use efficiency as well as by differences in other inputs to the MODIS GPP algorithm---daily incident PAR, minimum temperature, and vapor pressure deficit. Ground-based scaling of GPP has the potential to improve the parameterization of light use efficiency in satellite-based GPP monitoring algorithms.

Simulating the carbon balance of a temperate larch forest under various meteorological conditions
About this Resource: Abstract Background Changes in the timing of phenological events may cause the annual carbon budget of deciduous forests to change. Therefore, one should take such events into account when evaluating the effects of global warming on deciduous forests. In this article, we report on the results of numerical experiments done with a model that includes a phenological module simulating the timing of bud burst and other phenological events and estimating maximum leaf area index. Results This study suggests that the negative effects of warming on tree productivity (net primary production) outweigh the positive effects of a prolonged growing season. An increase in air temperature by 3&#176;C (5&#176;C) reduces cumulative net primary production by 21.3% (34.2%). Similarly, cumulative net ecosystem production (the difference between cumulative net primary production and heterotrophic respiration) decreases by 43.5% (64.5%) when temperatures are increased by 3&#176;C (5&#176;C). However, the positive effects of CO2 enrichment (2 &#215; CO2) outweigh the negative effects of warming (&lt;5&#176;C). Conclusion Although the model was calibrated and validated for a specific forest ecosystem, the implications of the study may be extrapolated to deciduous forests in cool-temperate zones. These forests share common features, and it can be conjectured that carbon stocks would increase in such forests in the face of doubled CO2 and increased temperatures as long as the increase in temperature does not exceed 5&#176;C.

Strengthening Conservation in the Tropics: The Water Canon of Costa Rica
About this Resource: Problem statement: The tropics contain primary forests with a significant value for society, as they provide services such as carbon sequestration, soil conservation, bio-prospecting, water storage and others. Competing land uses have not favored conservation during the last several decades and therefore the need for an effective public policy instrument to curtail forest loss is evident. Approach: This article analyzed a policy intended to augment the funds for subsidizing forest conservation in Costa Rica through a tax on the consumption of potable water. This potable water canon was compared on the basis of legitimacy criteria to the alternative of imposing a tax on the exploitation of marginal lands. The analysis was based on comparing the perceptions different stakeholders have toward deforestation and its potential solutions, which result into different frames, or views regarding the problem. The perceptions were obtained from semi-structured interviews of individuals representing the central and local governments, national and local non-governmental organizations, the private sector, academia and political parties. Results: Overall, the water canon is a superior policy from the point of view of technical implementability and political feasibility. The regulation was expected to increase the forest cover in private hands in a more effective way than the tax on marginal lands, while keeping government expenditures to a minimum. The policy context is one of high expert and social trust and low government trust, requiring substantive stakeholder education and the creation of feedback mechanisms to increase acceptability during the implementation period. Conclusion: If approved by the Costa Rican Congress, the water canon will become an innovative conservation policy from which other developing countries will be able to obtain valuable lessons.

Alabama forest industries
About this Resource: Alabama forests supplied 718 million cubic feet of roundwood to forest industries during 1971. Softwoods, mainly pine, made up over seven-tenths of the total. In terms of volume harvested, pulpwood was the leading product, with saw logs second. The two combined accounted for 91 percent of the roundwood produced. These are some of the major findings of a 1971 canvass of all primary forest industries using wood from Alabama.

Tropical Forest Foundation
About this Resource: The TFF is dedicated to the conservation of tropical forests through sustainable forestry. The primary focus of the Tropical Forest Foundation is to demonstrate and teach sustainable forest management through Reduced-impact Logging. This website offers users information about the Foundation as well as publications such as newsletters, bulletins, and other reports. The site also gives information about how the industry can help, Reduced-impact Logging, forestry in the future, and their sponsors.

Production of Total Potentially Soluble Organic C, N, and P Across an Ecosystem Chronosequence: Root versus Leaf Litter
About this Resource: Dissolved organic matter (DOM) plays several important roles in forest ecosystem development, undergoing chemical, physical and/or biological reactions that affect ecosystem nutrient retention. Very few studies have focused on gross rates of DOM production, and we know of no study that has directly measured DOM production from root litter. Our objectives were to quantify major sources of total potentially water-soluble organic matter (DOMtps) production, with an emphasis on production from root litter, to quantify and compare total potentially soluble organic C, N, and P (DOCtps, DONtps, and DOPtps) production, and to quantify changes in their production during forest primary succession and ecosystem development at the Mt. Shasta Mudflows ecosystem chronosequence. To do so, we exhaustively extracted freshly senesced root and leaf and other aboveground litter for DOCtps, DONtps, and DOPtps by vegetation category, and we calculated DOMtps production (g m⁻² y⁻¹) at the ecosystem level using data for annual production of fine root and aboveground litter. DOM production from throughfall was calculated by measuring throughfall volume and concentration over 2 years. Results showed that DOMtps production from root litter was a very important source of DOMtps in the Mount Shasta mudflow ecosystems, in some cases comparable to production from leaf litter for DONtps and larger than production from leaf litter for DOPtps. Total DOCtps and DONtps production from all sources increased early in succession from the 77- to the 255-year-old ecosystem. However, total DOPtps production across the ecosystem chronosequence showed a unique pattern. Generally, the relative importance of root litter for total fine detrital DOCtps and DONtps production increased significantly during ecosystem development. Furthermore, DOCtps and DONtps production were predominantly driven by changes in biomass production during ecosystem development, whereas changes in litter solubility due to changes in species composition had a smaller effect. We suggest that DOMtps production from root litter may be an important source of organic matter for the accumulation of SOM during forest ecosystem development.

Geographical variation in the periodicity of gypsy moth outbreaks
About this Resource: The existence of periodic oscillations in populations of forest Lepidoptera is well known. While information exists on how the periods of oscillations vary among different species, there is little prior evidence of variation in periodicity within the range of a single Lepidopteran species. The exotic gypsy moth is an introduced foliage-feeding insect in North America. Its populations are characterized by high amplitude oscillations between innocuously low densities and outbreak levels during which large regions of forests are defoliated. These outbreaks are recognized to arise periodically with considerable synchrony across much of the gypsy moth's North American range. Our analysis indicates that gypsy moth outbreaks in North America are periodic but they exhibit two dominant periodicities: a primary period of 8-10 yr (as previously reported) and a secondary period of 4-5 yr (a new finding in this study). The outbreak periodicity varied geographically and this variation was associated with forest type. We found that in the most susceptible forest types, those on xeric sites where oak is often mixed with pines, outbreak periodicity had a more dominant 5-yr period while in forest types characteristic of more mesic sites where oak was mixed with maples and other species, cycles were clearly operating on a 10-yr period.

Oak Ridge National Laboratory - Distributed Active Archive Center
About this Resource: A NASA-sponsored resource, this website provides biogeochemical and ecological data that may prove helpful in complementing environmental research. Includes field data, remote-sensing data, imagery results from ecosystem modeling. The ORNL-DAAC archives both regional and global data on: climate, environmental processes, nutrient cycles, stream and water discharges, soil properties, canopy chemistry, net primary production, land use change, and vegetation. This service can improve, and validate, output for researchers engaged in the production of ecosystem models. Makes an extensive use of popup screens, intended to aid with site navigation.

Leaffall Phenology in a Subtropical Wet Forest in Puerto Rico: From Species to Community Patterns
About this Resource: Leaffall phenology is an important periodical event in forests, contributing to mobilization of organic matter from primary producers to soil. For seasonal forests, leaffall periodicity has been related to rainfall regime and dry season length. In weakly seasonal forests, where there is no marked dry season, other climatic factors could trigger leaf shed. In this study, we aimed to determine if other climatic variables (wind speed, solar radiation, photosynthetic photon flux density [PPFD], day length, temperature, and relative humidity) could be better correlated with patterns of litter and leaffall in a weakly seasonal subtropical wet forest in Puerto Rico. Leaffall patterns were correlated mainly with solar radiation, PPFD, day length, and temperature; and secondarily with rainfall. Two main peaks of leaffall were observed: April-June and August-September, coinciding with the periods of major solar radiation at this latitude. Community leaffall patterns were the result of overlapping peaks of individual species. Of the 32 species analyzed, 21 showed phenological patterns, either unimodal (16 species), bimodal (three species), or multimodal (two species). Lianas also presented leaffall seasonality, suggesting that they are subject to the same constraints and triggering factors affecting trees. In addition to solar radiation as a main determinant of leaffall timing in tropical forests, our findings highlight the importance of interannual variation and asynchrony, suggesting that leaffall is the result of a complex interaction between environmental and physiological factors.

Protecting Soil and Water in Forest Road Management
About this Resource: The National Forest road system is the network that supports public recreation, which has become the primary use of the public lands. The pattern of use of National Forest roads for recreation has increased dramatically since the late 1940s and is expected to continue to increase beyond the rates observed today. However, research over the past 60 years clearly presents forest roads as a major source of sediment and soil erosion from forest watersheds. Threats to healthy forests have received increased attention in the past decade. In particular, roads, road management, and travel management will likely be critical to addressing the four threats to the health of the nation's forests and grasslands that were identified by USDA Forest Service. Road management is an important component in preserving and maintaining healthy forests throughout the nation. Sediment export from the existing forest road network is an issue of great concern in forest management. The objective of this article is to provide an overview of issues involved in managing the nation's public forest roads for the protection of soil and water. This article explores the benefit and efficacy of erosion mitigation, sediment control, and road BMPs in protecting soil and water. This article also suggests areas requiring additional research and development to satisfy the goals of protecting forest soil and water.

Effects of Off-Highway Vehicle Use on the American Marten
About this Resource: Motorized recreation in North American wildlands is increasing, and technological developments in the power and range of vehicles has increased access to high-elevation habitats. The American marten (Martes americana) is vulnerable to this disturbance because martens, like other residents of high-elevation forests, are associated with remote wilderness conditions where the presence of motorized vehicles is a recent phenomenon. We evaluated the effects of vehicles at 2 study sites in California, USA, by comparing marten occupancy rates and probabilities of detection in areas where recreational vehicle use is legal and encouraged (use areas) with wilderness areas where vehicles are prohibited (non-use areas). We sampled vehicle occurrence in nearby use and non-use areas using sound level meters and determined marten occurrence using track and camera stations. We also included 2 secondary measures of potential effects of vehicles on martens: sex ratio and circadian pattern of activity. Martens were ubiquitous in use and non-use areas in both study sites, and there was no effect of vehicle use on marten occupancy or probability of detection. We predicted that females might be less common and martens more nocturnal in use than in nonuse areas, but neither occurred. Martens were exposed to low levels of disturbance in our study sites. We estimated that a marten might be exposed to 0.5 vehicle passes/hour and that this exposure had the greatest effect on ,20% of a typical home range area. Furthermore, vehicle use usually occurred when martens were inactive. We did not measure behavioral, physiological, or demographic responses, so it is possible that vehicles may have effects, alone or in concert with other threats (e.g., timber harvest), that we did not quantify. We encourage additional studies to determine whether other montane species that are year-round residents demonstrate the same response to motorized vehicles.

Aboveground sink strength in forests controls the allocation of carbon below ground and its [CO₂]-induced enhancement
About this Resource: The partitioning among carbon (C) pools of the extra C captured under elevated atmospheric CO₂ concentration ([CO₂]) determines the enhancement in C sequestration, yet no clear partitioning rules exist. Here, we used first principles and published data from four free-air CO₂ enrichment (FACE) experiments on forest tree species to conceptualize the total allocation of C to below ground (TBCA) under current [CO₂] and to predict the likely effect of elevated [CO₂]. We show that at a FACE site where leaf area index (L) of Pinus taeda L. was altered through nitrogen fertilization, ice-storm damage, and droughts, changes in L, reflecting the aboveground sink for net primary productivity, were accompanied by opposite changes in TBCA. A similar pattern emerged when data were combined from the four FACE experiments, using leaf area duration (L(D)) to account for differences in growing-season length. Moreover, elevated [CO₂]-induced enhancement of TBCA in the combined data decreased from approximately equal to 50% (700 g C m⁻² y⁻¹) at the lowest L(D) to approximately equal to 30% (200 g C m⁻² y⁻¹) at the highest L(D). The consistency of the trend in TBCA with L and its response to [CO₂] across the sites provides a norm for predictions of ecosystem C cycling, and is particularly useful for models that use L to estimate components of the terrestrial C balance.

Assessment of Forest Fuel Loadings in Puerto Rico and the US Virgin Islands
About this Resource: Quantification of the downed woody materials that comprise forest fuels has gained importance in Caribbean forest ecosystems due to the increasing incidence and severity of wildfires on island ecosystems. Because large-scale assessments of forest fuels have rarely been conducted for these ecosystems, forest fuels were assessed at 121 US Department of Agriculture forest service inventory plots on Puerto Rico, Vieques, and the US Virgin Islands. Results indicated that fuel loadings averaged 24.05 Mg ha-1 in 2004-2006. Forest litter decreased from wetter to drier forest life zones. These island forests showed a paucity of coarse woody fuels (CWD) (2.91 Mg ha-1) and relatively greater quantities of smaller-sized fine woody fuels (FWD) (10.18 Mg ha-1 for FWD and 10.82 Mg ha-1 for duff/litter) when compared to continental tropical forests. Between 2001 and 2006, CWD fuel loads decreased, while fine fuels and litter increased, such that total fuel loads remained constant on a subset of plots on Puerto Rico. This trend indicates that continued decomposition of CWD deposited by the last severe hurricane is balanced by increasing inputs of FWD from recovering and maturing secondary forests. Forest disturbance cycles and successional development must be taken into account by agencies charged with fire protection and risk assessment.

Current problems of close-to-nature silviculture in Italy
About this Resource: The main problems of Italian forests are critically reviewed, considering the ecological as well the socio-economic factors that have been responsable of the main evolutionary processes, i.e., the secondary succession under artificial conifer stands, the ageing of the coppice forest, the post-cultivation evolution on abandoned fields and the increase of wild ungulates, which currently represents one of the most dramatic problems to be faced in forest management. Concepts as biodiversity, multifunctionality and sustainable management are the foundations, nowadays, of forest management. The main elements traditionally characterizing the close-to-nature silviculture are discussed and critically examined, warning against ideology and rigidity. Two concepts are more carefully discussed: natural vegetation dynamics and mixed uneven aged forest. An analysis of the priorities of silviculture in Italy concludes the paper, namely: the importance to take advantage of the “natural opportunities” in the cheapest way (the cost of the thinnings is a first rate problem, nowadays); to consider forests ecosystems in the context of surrounding natural and cultural landscape; to define proper management strategies for secondary successions on abandoned fields and pastures; to aim at re-naturalizing artificial conifer stands and increasing/maintaining forest biodiversity; to tackle effectively the wild ungulates problem.

Polar organic tracers in PM2.5 aerosols from forests in eastern China
About this Resource: Photooxidation products of biogenic volatile organic compounds, mainly isoprene and monoterpenes, are significant sources of atmospheric particulate matter in forested regions. The objectives of this study were to examine time series and diel variations of polar organic tracers for the photooxidation of isoprene and &alpha;-pinene to investigate whether they are linked with meteorological parameters or trace gases, and to determine their carbon contributions. In addition, the biogenic secondary organic carbon contributions from isoprene were estimated. PM2.5 (particulate matter with an aerodynamic diameter &lt;2.5 &mu;m) aerosol samples were collected from forests in eastern China and compared with data from forested sites in Europe and America. Aerosol sampling was conducted at four sites located along a gradient of ecological succession in four different regions, i.e. Changbai Mountain Nature Reserve (boreal-temperate), Chongming National Forest Park (temperate), Dinghu Mountain Nature Reserve (subtropical) and Jianfengling Nature Reserve in Hainan (tropical) during summer periods when the meteorological conditions are believed to be favorable for photochemical processes. Fifty PM2.5 samples were collected; eighteen organic compounds, organic carbon (OC), elemental carbon and trace gases were measured. Results indicate that the concentration trends of the secondary organic compounds reflected those of the trace gases and meteorological parameters. Very good correlations between the sum concentrations of isoprene oxidation products and atmospheric SO2, O3, NO2, NOx, as well as CO2, at the Changbai site were found. The secondary OC due to isoprene was relatively high in tropical Hainan (0.27 μgC/m3) where isoprene-emitting broadleaf species are dominant, but was comparable in boreal Changbai (0.32 &mu;gC/m3) where coniferous species are prevalent. The contribution of malic acid, which may have both biogenic and anthropogenic sources, to the OC mass was comparable at the four sites.

Microhabitat Associations of Northern Flying Squirrels in Burned and Thinned Forest Stands of the Sierra Nevada
About this Resource: Prescribed burning and mechanical thinning are used to manage fuels within many western North American forest ecosystems, but few studies have examined the relative impacts of these treatments on forest wildlife. We sampled northern flying squirrels (Glaucomys sabrinus) and microhabitat variables in burned, thinned and control stands of mixed-conifer forest of the southern Sierra Nevada at the Teakettle Experimental Forest. We used this information to determine the effects of burning and thinning on the microhabitat associations of flying squirrels. Across pretreatment stands, the probability of flying squirrel capture increased with decreasing distance to a perennial creek and increasing litter depth. The probability of flying squirrel capture also was greater with increased canopy cover in thinned stands and increased litter depth in burned stands. Greater canopy cover may provide protection from predators, thicker litter layers may harbor a greater abundance of truffles, a primary food of northern flying squirrels, and creeks may provide squirrels with food sources, drinking water and nest trees. Results from this study underscore the need for more information on the effects of forest management on northern flying squirrels near the southern extent of the species' geographic range.

The effect of HNO₃ gas on the lichen Ramalina menziesii
About this Resource: Nitric acid (HNO₃) and ozone (O₃), secondary products of photochemical reactions of nitrogen oxides (NO(x)) and volatile organic compounds, are important pollutants in arid regions with large outputs from petrol combustion. In the Los Angeles (LA) air basin, nitrogen dry deposition rates in forests downwind of the urban areas can reach 35-40 kg ha-1 year-1, roughly equivalent to the amount of N used to fertilize agricultural fields. The marked decline in the lichen population of the LA air basin has previously been attributed to local O₃ concentration gradients, which overlaid the patterns of species extirpation. Recent research in the air basin has shown that nitrate (NO₃⁻) deposition gradients run parallel to the O₃ concentration gradient, and that deposition of NO₃⁻ and HNO₃ can have significant effects on forest health. Our research examines the effects of HNO₃ dry deposition on the lichen Ramalina menziesii Tayl. in an effort to understand the loss of lichen species in southern California, and increase the usefulness of lichens as biomonitors of nitrogen pollutants. We transplanted healthy R. menziesii thalli from a “pristine” location into fumigation chambers and exposed them to HNO₃ under humid and dry conditions, and moderate and high HNO₃ fumigations. R. menziesii thalli treated with HNO₃ in month-long fumigations experienced a significant decline in chlorophyll content and carbon exchange capacity compared to thalli in control chambers. Leachate conductivity, NO₃⁻ and K⁺ concentrations increased with HNO₃ fumigation levels and time. We conclude that R. menziesii has an unequivocally negative response to HNO₃ gas concentrations common to ambient summer conditions in the LA air basin.

Record high peaks in PCB concentrations in the Arctic atmosphere due to long-range transport of biomass burning emissions
About this Resource: Soils and forests in the boreal region of the Northern Hemisphere are recognised as having a large capacity for storing air-borne Persistent Organic Pollutants (POPs), such as the polychlorinated biphenyls (PCBs). Following reductions of primary emissions of various legacy POPs, there is an increasing interest and debate about the relative importance of secondary re-emissions on the atmospheric levels of POPs. In spring of 2006, biomass burning emissions from agricultural fires in Eastern Europe were transported to the Zeppelin station on Svalbard, where record-high levels of many air pollutants were recorded (Stohl et al., 2007). Here we report on the extremely high concentrations of PCBs that were also measured during this period. 21 out of 32 PCB congeners were enhanced by more than two standard deviations above the long-term mean concentrations. In July 2004, about 5.8 million hectare of boreal forest burned in North America, emitting a pollution plume which reached the Zeppelin station after a travel time of 3&ndash;4 weeks (Stohl et al., 2006). Again, 12 PCB congeners were elevated above the long-term mean by more than two standard deviations, with the less chlorinated congeners being most strongly affected. We propose that these abnormally high concentrations were caused by biomass burning emissions. Based on enhancement ratios with carbon monoxide and known emissions factors for this species, we estimate that 130 and 66 μg PCBs were released per kilogram dry matter burned, respectively. To our knowledge, this is the first study relating atmospheric PCB enhancements with biomass burning. The strong effects on observed concentrations far away from the sources, suggest that biomass burning is an important source of PCBs for the atmosphere.

Record high peaks in PCB concentrations in the Arctic atmosphere due to long-range transport of biomass burning emissions
About this Resource: Soils and forests in the boreal region of the northern hemisphere are recognised as having a large capacity for storing air-borne Persistent Organic Pollutants (POPs), such as the polychlorinated biphenyls (PCBs). Following reductions of primary emissions of various legacy POPs, there is an increasing interest and debate about the relative importance of secondary re-emissions on the atmospheric levels of POPs. In spring of 2006, biomass burning emissions from agricultural fires in Eastern Europe were transported to the Zeppelin station on Svalbard, where record-high levels of many air pollutants were recorded (Stohl et al., 2007). Here we report on the extremely high concentrations of PCBs that were also measured during this period. 21 out of 32 PCB congeners were enhanced by more than two standard deviations above the long-term mean concentrations. In July 2004, about 5.8 million hectare of boreal forest burned in North America, emitting a pollution plume which reached the Zeppelin station after a travel time of 3&ndash;4 weeks (Stohl et al., 2006). Again, 12 PCB congeners were elevated above the long-term mean by more than two standard deviations, with the less chlorinated congeners being most strongly affected. We propose that these abnormally high concentrations were caused by biomass burning emissions. Based on enhancement ratios with carbon monoxide and known emissions factors for this species, we estimate that 130 and 66 μg PCBs were released per kilogram dry matter burned, respectively. To our knowledge, this is the first study relating atmospheric PCB enhancements with biomass burning. The strong effects on observed concentrations far away from the sources, suggest that biomass burning is an important source of PCBs for the atmosphere.

Comprehensive comparison of gap-filling techniques for eddy covariance net carbon fluxes
About this Resource: We review 15 techniques for estimating missing values of net ecosystem CO2 exchange (NEE) in eddy covariance time series and evaluate their performance for different artificial gap scenarios based on a set of 10 benchmark datasets from six forested sites in Europe. The goal of gap filling is the reproduction of the NEE time series and hence this present work focuses on estimating missing NEE values, not on editing or the removal of suspect values in these time series due to systematic errors in the measurements (e.g., nighttime flux, advection). The gap filling was examined by generating 50 secondary datasets with artificial gaps (ranging in length from single half-hours to 12 consecutive days) for each benchmark dataset and evaluating the performance with a variety of statistical metrics. The performance of the gap filling varied among sites and depended on the level of aggregation (native half-hourly time step versus daily), long gaps were more difficult to fill than short gaps, and differences among the techniques were more pronounced during the day than at night. The non-linear regression techniques (NLRs), the look-up table (LUT), marginal distribution sampling (MDS), and the semi-parametric model (SPM) generally showed good overall performance. The artificial neural network based techniques (ANNs) were generally, if only slightly, superior to the other techniques. The simple interpolation technique of mean diurnal variation (MDV) showed a moderate but consistent performance. Several sophisticated techniques, the dual unscented Kalman filter (UKF), the multiple imputation method (MIM), the terrestrial biosphere model (BETHY), but also one of the ANNs and one of the NLRs showed high biases which resulted in a low reliability of the annual sums, indicating that additional development might be needed. An uncertainty analysis comparing the estimated random error in the 10 benchmark datasets with the artificial gap residuals suggested that the techniques are already at or very close to the noise limit of the measurements. Based on the techniques and site data examined here, the effect of gap filling on the annual sums of NEE is modest, with most techniques falling within a range of ±25 g C m-2 year-1.

Heterotrophic components of soil respiration in pastures and forests in southwestern Amazonia, Acre, Brazil
About this Resource: In this paper we present data on soil microbial biomass and heterotrophic respiration in pastures, mature and secondary forests, in order to elucidate their contribution to total CO2 flux from soil to atmosphere. The research was conducted in Southwestern Amazonia, Acre State, Brazil. Microbial biomass was estimated using a variation of the traditional fumigation-extraction method and heterotrophic respiration was measured using respirometry flasks attached to an infrared gas analyzer. Soil microbial biomass and heterotrophic respiration did not differ statistically among pastures, mature and secondary forests. These laboratory results indicate that higher CO2 fluxes from pasture soils measured in situ are probably due to higher root respiration by pasture grasses.

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.

Arkansas forest industries, 1971
About this Resource: Arkansas forests supplied more than 451 million cubic feet of roundwood to forest industries in 1971. Softwoods, mainly pine, made up more than two-thirds of the total. The timber harvest increased 15 percent during the years 1969-1971, while the number of primary wood-using plants decreased. Saw logs and pulpwood comprised 83 percent of the roundwood. Veneer logs made up over 9 percent, with more than half of the remainder going into poles and charcoal wood. Figure 1 shows recent trends in output of these products.

The effects of prescribed fire and silvicultural thinning on the aboveground carbon stocks and net primary production of overstory trees in an oak-hickory ecosystem in southern Ohio
About this Resource: More than 70 years of fire suppression has influenced forest dynamics and led to the accumulation of fuels in many forests of the United States. To address these changes, forest managers increasingly seek to restore historical ecosystem structure and function through the reintroduction of fire and disturbance processes that mimic fire such as silvicultural thinning. In oak forests of eastern North America, prescribed fire and thinning are important tools used to facilitate oak (Quercus spp.) regeneration and recruitment. The global scientific community is increasingly raising concerns about the accumulation of atmospheric CO₂, and its potential to impact global climate; therefore, activities such as prescribed fire and thinning that can influence the carbon balance of terrestrial ecosystems should be evaluated. We used field measurements and modeling with the PnET-II carbon balance model in oak forests of southern Ohio, USA, to (1) assess the efficacy of prescribed fire and silvicultural thinning in facilitating oak recruitment and regeneration, and (2) quantify the impacts of these treatments on aboveground carbon stocks and net primary production. Silvicultural thinning increased recruitment of maples, but oak recruitment was minimal. Prescribed burning caused an increase in the mortality rate of oaks' major competitor (Acer rubrum L.) in the overstory (stems >=10cm DBH), but oak mortality also increased following the burn treatments. Our measurements of stem growth suggest that the timing of the prescribed fires coincided with the initiation of growth in oaks, which may have created vulnerability in these species that are generally considered fire-resistant. The pre-treatment aboveground biomass of overstory trees was approximately 233Mg/ha (Mg=1x10⁶ g). Prescribed burning had significant impacts on the mortality of stems; however, it had no significant effects on the aboveground net primary production (ANPP). Thinning removed approximately 30% of the aboveground biomass and resulted in significant but transient (1 year) reduction of ANPP (386 and 560gCm⁻² year⁻¹ for thinned and non-thinned stands, respectively). In sum, thinning created recruitment opportunities in our study area, but these opportunities were captured by maples, and oak recruitment was minimal. Prescribed fire caused mortality in oaks and maples, and the oak mortality may have been related to the coincidence of the burn treatment and the initiation of oak stem growth. Finally, our data suggest that there is a transient impact of thinning on ANPP, but that there is no long-term effect of thinning and/or burning treatments on the aboveground carbon uptake in oak forests.