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Browse subject: forest trees
Number of records: 477

Proceedings, U. S. Department of Agriculture interagency gypsy moth research review 1990; 1990 January 22-25; East Windsor, CT. : Population Dynamics
About this Resource: The techniques and methodology for sampling gypsy moth, Lymantria dispar L., at low densities less than 100 egg masses/ha (EM/ha), are compared. Forest managers have constraints of time and cost, and need a useful, simple predictable means to assist them in sampling gypsy moth populations. A comparison of various techniques coupled with results of recent habitat research studies indicates that a series of burlap banded trees can be utilized to monitor egg-mass desity change over time. Egg masses eneath bands accurately reflect densities on unbanded trees, yet does not seem to be a mojor factor indetermining the distribution of gypsy moth egg masses; however, forest stands selected for banding should have a major oak component. Predicting a 2-year lead time to outbreak is possible based upon two consecutive years with an increase of one order of magnitude or greater of egg-mass density beneath bands.

Upper Peninsula Tree Identification Key
About this Resource: The identification key is a tool to help people identify trees. It's purpose is to identify the commonly encountered tree and shrub species of the Upper Peninsula of Michigan. The site also provides lists of identifying characteristics, species, most common trees by county, and a taxonomy list. There is a link to a tree identification glossary, and information about Michigan forest history.

USDA Forest Service: Tree List
About this Resource: The Tree list provides a list of over 300 tree species. For each tree, the common name is provided as well as an introduction, the distribution and occurrence, management considerations, botanical and ecological characterisitcs, fire ecology, fire effects, and references.

Macrohabitat factors affect day roost selection by eastern red bats and eastern pipistrelles in the southern Appalachian Mountains, USA
About this Resource: Although roost sites are critically important to bats, we have few data on macrohabitat factors that affect roost selection by foliage-roosting bats. Such data are needed so that forest managers can make informed decisions regarding conservation of bat roosts. Our objective was to examine roost selection by non-reproductive eastern pipistrelles (Perimyotis subflavus) and red bats (Lasiurus borealis) in a dense deciduous forest undergoing low-intensity timber management in the southern Appalachian Mountains of western North Carolina, USA. During May to August 2004-2006, we radiotracked eight red bats and seven pipistrelles to roosts for 1-14 days (red bats, mean = 4.11 days, n =19 roosts; pipistrelles, mean = 7 days, n =15 roosts). We compared roost and random trees or points using paired-sample t-tests for tree and microhabitat characters and logistic regression models of one to three variables for macrohabitat characters. Neither red bats nor pipistrelles selected roosts based on tree or microhabitat characteristics. Red bats used a wide range of stand ages and conditions and, based on our most plausible models for macrohabitat variables, roosted closer than expected (mean = 70.6 m ) to linear openings such as gated roads. Pipistrelles only used stands >=72 years in age and roosted closer than expected (mean = 185.6 m) to non-linear openings and at elevations lower than expected (mean = 882 m) . Combined evidence of multiple variables indicated that pipistrelles preferred to roost close to streams. Our results indicate that land managers in the southern Appalachians should maintain a diversity of age classes to provide roosting habitat for both species, and that pipistrelles in particular may benefit from retention of mature stands or buffer zones near perennial streams. Furthermore, non-reproductive red bats and pipistrelles may prefer to roost near openings to minimize commuting costs when openings comprise a small proportion of a densely forested landscape.

Effects of forest cover, topography, and sampling extent on the measured density of shallow, translational landslides
About this Resource: We use regionally available digital elevation models and land cover data, calibrated with ground- and photo-based landslide inventories, to produce spatially distributed estimates of shallow, translational landslide density (number/unit area). To discern effects of land use, we focus on resolving landslide density relationships with forest cover. We account for topographic variability between sites and landslide detection bias in air photo mapping. Even so, for sites in the Oregon Coast Range, we find great variability in the ratios of landslide density in forest classes among sites. We present strategies for subsampling available data to quantify this variability. For these data, we find that older forests, when sampled over tens of square kilometers, commonly exhibited the highest landslide densities but over hundreds of square kilometers always exhibited the lowest densities, averaging 30% of that in recently harvested areas and 79% of that in younger, managed forests.

Newer Classification and Regression Tree Techniques: Bagging and Random Forests for Ecological Prediction
About this Resource: The task of modeling the distribution of a large number of tree species under future climate scenarios presents unique challenges. First, the model must be robust enough to handle climate data outside the current range without producing unacceptable instability in the output. In addition, the technique should have automatic search mechanisms built in to select the most appropriate values for input model parameters for each species so that minimal effort is required when these parameters are fine-tuned for individual tree species. We evaluated four statistical models--Regression Tree Analysis (RTA), Bagging Trees (BT), Random Forests (RF), and Multivariate Adaptive Regression Splines (MARS)--for predictive vegetation mapping under current and future climate scenarios according to the Canadian Climate Centre global circulation model. To test, we applied these techniques to four tree species common in the eastern United States: loblolly pine (Pinus taeda), sugar maple (Acer saccharum), American beech (Fagus grandifolia), and white oak (Quercus alba). When the four techniques were assessed with Kappa and fuzzy Kappa statistics, RF and BT were superior in reproducing current importance value (a measure of basal area in addition to abundance) distributions for the four tree species, as derived from approximately 100,000 USDA Forest Service's Forest Inventory and Analysis plots. Future estimates of suitable habitat after climate change were visually more reasonable with BT and RF, with slightly better performance by RF as assessed by Kappa statistics, correlation estimates, and spatial distribution of importance values. Although RTA did not perform as well as BT and RF, it provided interpretive models for species whose distributions were captured well by our current set of predictors. MARS was adequate for predicting current distributions but unacceptable for future climate. We consider RTA, BT, and RF modeling approaches, especially when used together to take advantage of their individual strengths, to be robust for predictive mapping and recommend their inclusion in the ecological toolbox.

Effectiveness of Permethrin Plus-C (Masterline) and Carbaryl (Sevin SL) for Protecting Individual, High-Value Pines (Pinus) From Bark Beetle Attack
About this Resource: Bark beetles (Coleoptera: Scolytidae) are commonly recognized as the most important mortality agent in western North American coniferous forests. High-value trees such as those located in residential, recreational, or administrative sites are particularly susceptible to attack. Regardless of landowner objectives, tree losses in these unique environments generally have a catastrophic impact. The value of these individual trees, the cost of removal, and the loss of aesthetics may justify protection until the main thrust of a bark beetle infestation subsides. This situation emphasizes the need for assuring that effective insecticides are available for individual tree protection. In this study, we assessed the efficacy of permethrin plus-C (Masterline) and carbaryl (Sevin SL) for protecting ponderosa, Pinus ponderosa Dougl. ex. Laws., lodgepole, P. contorta Dougl. ex Loud., and pinyon, P. edulis Engelm., pines from bark beetle attack during two field seasons. Masterline was effective for protecting P. contorta from mountain pine beetle, Dendroctonus ponderosae Hopkins, attack for one field season. However, Sevin SL was efficacious for two field seasons. An insufficient number of P. ponderosa and P. edulis control trees were killed to make definitive conclusions regarding efficacy in those systems. The data reported here regarding Masterline is the first published report on its effectiveness for preventing bark beetle attack on standing trees. Masterline appears to be an effective individual tree protection tool, but repeated applications will be necessary if multiyear control is desired.

Deer Impact on Vegetation in Natural Areas in Southeastern Nebraska
About this Resource: We studied the effect of browsing by white-tailed deer (Odocoileus virginianus Zimmerman) on vegetation at three sites with high densities of deer and six sites with low densities of deer along the Missouri and Platte Rivers in southeastern Nebraska in 1995-1996. Vegetation volume from 0-1 m high was similar between sites with high and low deer densities (P > 0.05). From 1-2 m high, vegetation volume was less at sites with more deer in both years (P < 0.05). Densities for eight of 11 small woody plant categories (< 3 cm dbh) were less common at sites with high densities of deer (P < 0.05). Overall densities of small trees (3-15 cm dbh) were similar between sites with high and low densities of deer. However, small hackberry trees (Celtis occidentalis L.) were more common (P = 0.03), while all other small trees were less common (P = 0.038), at sites with more deer. Frequencies of ground cover plants were not randomly distributed (χ2 = 588.2, P < 0.001, df = 12). Shrubs were less common and grasses more common than expected at sites with more deer. Forests at sites with high densities of deer are in the process of succeeding to a state dominated by hackberry in the overstory with reduced woody vegetation and increased grasses in the understory due to intensive browsing by deer.

Forestry Images : Forest Health, Natural Resources & Silviculture Images
About this Resource: A link to over 22,000 digital images devoted to forestry, natural resources, silviculture, incluing: forest pests, trees, understory and rangeland plants, wildlife, people, places and scenes. A substantial number of photos are public sector images; the downloading and use of which simply requires a registration. Availability results from a joint project involving The Bugwood Network, USDA's Forest Service, and the University of Georgia (engaging the Warnell School of Forest Resources and the College of Agricultural and Environmental Sciences).

Predicting the potential distribution of Sirex noctilio (Hymenoptera: Siricidae), a significant exotic pest of Pinus plantations
About this Resource: The potential distribution of sirex wood wasp (Sirex noctilio) in Australia, South America and Africa (where the insect is known to occur and is spreading) and North America and China (where sirex has not established) was assessed from a study of the insect's current distribution and host range. Sirex noctilio has a wide host range, mainly in Pinus, including many important commercial species planted as exotics in the Southern Hemisphere as well as native stands in North America. Using the climate-matching program CLIMEX the potential distribution range of S. noctilio was predicted across the globe based on climatic conditions in Eurasia and northern Africa, where the insect is endemic. Sirex noctilio is predicted to establish in the majority of commercial Pinus plantations in Australia. Many countries with commercial Pinus plantations in South America (Uruguay, Brazil, Argentina, Chile and Paraguay) as well as South Africa are predicted to be colonised by S. noctilio by natural migration. Countries that are a long distance from S. noctilio-infested areas, such as Ecuador, Colombia, Venezuela, Zimbabwe, Tanzania, Uganda, Ethiopia and plantations in southern Chile, western Australia and north-western Brazil, are only likely to be colonised by S. noctilio via human-assisted transport of infested wood. Sirex noctilio was predicted to be able to persist in many areas in North America. In China, S. noctilio is predicted to be able to persist in many areas where large-scale afforestation of susceptible hosts has occurred and is planned. However, S. noctilio is endemic in neighbouring countries of China, indicating that something other than climate and host is restricting S. noctilio establishing in China, or that it has not been detected yet. The Sirex Management Strategy will help reduce the spread and impact of S. noctilio.

National Register of Big Trees
About this Resource: This site provides information about the National Register of Big Trees. There is a search engine where users can search the Register, a list of species without champs, FAQs, big tree trivia, and state registers. There is also information on how to measure a big tree, hunting for big trees, and nominating a tree. Other resources include urban forest information, forest policy, sprawl information, a link to the Historic Tree Nursery, and resources for kids.

Forestry Images: The Source for Forest Health, Natural Resources and Silviculture Images
About this Resource: Forestry Images provides an archive of images related to forest health and silviculture, with particular emphasis on educational applications. The image categories are: Insects; Diseases; Other Damage Agents; Trees; Understory and Rangeland Plants; Silvicultural Practices; Wildlife; and People, Places, and Scenes.

Sacramento Tree Foundation
About this Resource: The Sacramento Tree Foundation strives to educate people in Sacramento about the importance of trees and the importance of planting and caring for trees in an effort to create the best urban forest for the Sacramento region. Their site provides information about volunteering and about both the Sacramento Shade Program and the Greenprint Program. The site offers information about the benefits of trees and access to several tree related games. There are also links to the Tree Foundation News, publications and videos.

What Tree is That?
About this Resource: This site was designed to help people plant and care for trees and to enhance the extent, health, and care of the urban and community forests. There are links to aid in eastern, central, and western tree identification by asking questions about the look and characteristics of the tree. There is a tree ID animation to help teach identification skills and information about the tree ID booklets that are for sale. There are links to a tree store, tree forums, tree resources, Arbor Day dates by state, and information about Arbor Day. There are also links to the Arbor Day Farm, a kids corner, Kids Explore Club, rain forest information, and information about conferences and seminars.

Biomass partitioning in red pine (Pinus resinosa) along a chronosequence in the Upper Peninsula of Michigan
About this Resource: Carbon (C) allocation to the perennial coarse-root system of trees contributes to ecosystem C sequestration through formation of long-lived live wood biomass and, following senescence, by providing a large source of nutrient-poor detrital C. Our understanding of the controls on C allocation to coarse-root growth is rudimentary, but it has important implications for projecting belowground net primary production responses to global change. Age-related changes in C allocation to coarse roots represent a critical uncertainty for modeling landscape-scale C storage and cycling. We used a 55 year chronosequence approach with complete above- and below-ground harvests to assess the effects of stand development on biomass partitioning in red pine (Pinus resinosa Ait.), a commercially important pine species. Averaged within site, individual-tree root/shoot ratios were dynamic across stand development, changing from 0.17 at 2-, 3-, and 5-year-old sites, to 0.80 at the 8-year-old site, to 0.29 at the 55-year-old site. The results of our study suggest that a current research challenge is to determine the generality of patterns of root-shoot biomass partitioning through stand development for both coniferous and hardwood forest types, and to document how these patterns change as a function of stand age, tree size, environment, and management.

Presettlement and modern disturbance regimes in coast redwood forests: Implications for the conservation of old-growth stands
About this Resource: Coast redwood (Sequoia sempervirens), a western North American conifer of ancient lineage, has a paradoxical combination of late-successional characteristics and strong adaptations to disturbance. Despite its shade tolerance and heavy dominance of the canopy on many sites, redwood saplings are uncommon in upland old-growth stands. Information needed to ensure the conservation of old-growth redwood forests has been limited. In this review paper, we integrate evidence on redwood biology with data on the historic and modern disturbance regimes to help clarify the degree to which key attributes of redwood forests may have been dependent upon periodic disturbance. Available evidence suggests that episodes of fire, flooding, and slope failure prior to European settlement were frequent but predominantly of low to moderate severity and extent, resulting in broadly uneven-aged forests. The majority of fires prior to European settlement were apparently of human origin. Frequency and severity of the major disturbance agents have been radically changed in modern times. Fires have been largely excluded, and flooding has been altered in ways that have often been detrimental to old-growth redwoods on alluvial terraces. However, because of the apparent anthropogenic origin of most presettlement fires, the long-term evolutionary role of fire for coast redwood is ecologically ambiguous. With fire exclusion, redwood possibly could be displaced to some extent on upland sites by increasing abundance of fire-sensitive competitors. Alternatively, redwood may be able to maintain dominance by vegetative sprouting and new seedling establishment on root-wad mounds, fallen logs, and on soil exposed by slope failure. Future research priorities are suggested that will help resolve some of the current ambiguities.

Trees Virginia (Virginia Urban Forest Council)
About this Resource: Trees Virginia works to encourage and aid the stewardship of Virginia's urban and community trees. Their website provides links to news and newsletters, publications, and links of interest, including government sites, organizations in Virginia, and urban forestry organizations. There is information about tree stewards and several tree care tips. There is also a photo gallery slide show and information about membership.

A comparison of thinning methods in red pine: consequences for stand-level growth and tree diameter
About this Resource: Long-term replicated experiments that contrast thinning method (dominant thinning, thinning from below) while controlling stocking level are rare. Stand growth and tree size responses to thinning method can be useful for making decisions to achieve desired objectives, whether these are timber or wildlife habitat related. We examined data from two long-term (>50 year old) silvicultural experiments in red pine to understand how alternative thinning prescriptions influence stand-level basal area, volume, and biomass growth, as well as quadratic mean tree diameter. We found that gross growth in stands treated with dominant thinning was often, although not always, greater than growth in stands treated with thinning from below. However, the differences in growth between thinning methods are smallest at stocking levels and stand ages typical for red pine management. We found that biomass growth increases with dominant thinning were generally less than basal area or volume growth increase. Furthermore, greater gross growth associated with dominant thinning versus thinning from below must be weighed against the significantly smaller average tree sizes that result from repeated dominant thinning.

Male Kirtland's Warblers' patch-level response to landscape structure during periods of varying population size and habitat amounts
About this Resource: Forest planners must evaluate how spatiotemporal changes in habitat amount and configuration across the landscape as a result of timber management will affect species' persistence. However, there are few long-term programs available for evaluation. We investigated the response of male Kirtland's Warbler (Dendroica kirtlandii) to 26 years of changing patch and landscape structure during a large, 26-year forestry-habitat restoration program within the warbler's primary breeding range. We found that the average density of male Kirtland's Warblers was related to a different combination of patch and landscape attributes depending on the species' regional population level and habitat amounts on the landscape (early succession jack pine (Pinus banksiana) forests; 15-42% habitat cover). Specifically, patch age and habitat regeneration type were important at low male population and total habitat amounts, while patch age and distance to an occupied patch were important at relatively high population and habitat amounts. Patch age and size were more important at increasing population levels and an intermediate amount of habitat. The importance of patch age to average male density during all periods reflects the temporal buildup and decline of male numbers as habitat suitability within the patch changed with succession. Habitat selection (i.e., preference for wildfire-regenerated habitat) and availability may explain the importance of habitat type and patch size during lower population and habitat levels. The relationship between male density and distance when there was the most habitat on the landscape and the male population was large and still increasing may be explained by the widening spatial dispersion of the increasing male population at the regional scale. Because creating or preserving habitat is not a random process, management efforts would benefit from more investigations of managed population responses to changes in spatial structure that occur through habitat gain rather than habitat loss to further our empirical understanding of general principles of the fragmentation process and habitat cover threshold effects within dynamic landscapes.

Forest Carbon Dynamics in the Pacific Northwest (USA) and the St. Petersburg Region of Russia: Comparisons and Policy Implications
About this Resource: Forests of the United States and Russia can play a positive role in reducing the extent of global warming caused by greenhouse gases, especially carbon dioxide. To determine the extent of carbon sequestration, physical, ecological, economic, and social issues need to be considered, including different forest management objectives across major forest ownership groups. Private timberlands in the U.S. Pacific Northwest are relatively young, well stocked, and sequestering carbon at relatively high rates. Forests in northwestern Russia are generally less productive than those in the Northwestern U.S. but cover extensive areas. A large increase in carbon storage per hectare in live tree biomass is projected on National Forest timberlands in the U.S. Pacific Northwest for all selected scenarios, with an increase of between 157-175 Mg by 2050 and a near doubling of 1970s levels. On private timberlands in the Pacific Northwest, average carbon in live tree biomass per hectare has been declining historically but began to level off near 65 Mg in 2000; projected levels by 2050 are roughly what they were in 1970 at approximately 80 Mg. In the St. Petersburg region, average carbon stores were similar to those on private lands in the Pacific Northwest: 57 Mg per hectare in 2000 and ranging from 40 to 64 Mg by 2050. Although the projected futures reflect a broad range of policy options, larger differences in projected carbon stores result from the starting conditions determined by ownership, regional environmental conditions, and past changes in forest management. However, an important change of forest management objective, such as the end of all timber harvest on National Forests in the Pacific Northwest or complete elimination of mature timber in the St. Petersburg region, can lead to substantial change in carbon stores over the next 50 years.

Using Airborne Lidar to Discern Age Classes of Cottonwood Trees in a Riparian Area
About this Resource: Airborne lidar (light detecting and ranging) is a useful tool for probing the structure of forest canopies. Such information is not readily available from other remote sensing methods and is essential for modern forest inventories. In this study, small-footprint lidar data were used to estimate biophysical properties of young, mature, and old cottonwood trees in the San Pedro River basin near Benson, Arizona. The lidar data were acquired in June 2004, using Optech's 1233 ALTM during flyovers conducted at an altitude of 600 m. Canopy height, crown diameter, stem dbh, canopy cover, and mean intensity of return laser pulses from the canopy surface were estimated for the cottonwood trees from the data. Linear regression models were used to develop equations relating lidar-derived tree characteristics with corresponding field acquired data for each age class of cottonwoods. The lidar estimates show a good degree of correlation with ground-based measurements. This study also shows that other parameters of young, mature, and old cottonwood trees such as height and canopy cover, when derived from lidar, are significantly different (P < 0.05). Additionally, mean crown diameters of mature and young trees are not statistically different at the study site (P = 0.31). The results illustrate the potential of airborne lidar data to differentiate different age classes of cottonwood trees for riparian areas quickly and quantitatively.

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.

Historical disturbance regimes as a reference for forest policy in a multiowner province: a simulation experiment
About this Resource: Using a landscape simulation model, we examined ecological and economic implications of forest policies designed to emulate the historical fire regime across the 2 x 10⁶ ha Oregon Coast Range. Simulated policies included two variants of the current policy and three policies reflecting aspects of the historical fire regime. Policy development was guided by the management intentions of four owner groups: forest industry, nonindustrial private, state, and federal. Fire severity was emulated with green-tree retention standards; fire frequency was emulated with annual harvestable area restrictions; and fire extent was emulated with harvest-unit size regulations. Simulated disturbance-based policies produced age-class distributions closer to the estimated historical range than those created by the current policy. Within 100 years, proportions of younger forests were within the historical range, while older forests moved closer to, but remained below, historical conditions. In the near term, disturbance-based policies produced annual harvest volumes 20%-60% lower than those produced by the current policy. However, relative costs of disturbance-based policies diminished over time. Our results suggest that if expediting a return to historical age-class distributions at a provincial-scale was a goal, then public lands would be needed to provide large patches of old forest. In addition, this experiment illustrated that distributing costs and benefits of conservation policies equitably across multiple private landowners is a significant challenge.

Regional Assessment of N Saturation using Foliar and Root delta15N
About this Resource: N saturation induced by atmospheric N deposition can have serious consequences for forest health in many regions. In order to evaluate whether foliar delta15N may be a robust, regional-scale measure of the onset of N saturation in forest ecosystems, we assembled a large dataset on atmospheric N deposition, foliar and root delta15N and N concentration, soil C:N, mineralization and nitrification. The dataset included sites in northeastern North America, Colorado, Alaska, southern Chile and Europe. Local drivers of N cycling (net nitrification and mineralization, and forest floor and soil C:N) were more closely coupled with foliar delta15N than the regional driver of N deposition. Foliar delta15N increased non-linearly with nitrification:mineralization ratio and decreased with forest floor C:N. Foliar delta15N was more strongly related to nitrification rates than was foliar N concentration, but concentration was more strongly correlated with N deposition. Root delta15N was more tightly coupled to forest floor properties than was foliar delta15N. We observed a pattern of decreasing foliar delta15N values across the following species: American beech>yellow birch>sugar maple. Other factors that affected foliar [graphic removed] included species composition and climate. Relationships between foliar delta15N and soil variables were stronger when analyzed on a species by species basis than when many species were lumped. European sites showed distinct patterns of lower foliar delta15N, due to the importance of ammonium deposition in this region. Our results suggest that examining delta15N values of foliage may improve understanding of how forests respond to the cascading effects of N deposition.

Western gall rust - a threat to Pinus radiata in New Zealand
About this Resource: Western gall rust (Peridermium harknessii J. P. Moore (syn. Endocronartium harknessii (J. P. Moore) Y.Hiratsuka) is potentially a serious threat to exotic Pinus radiata D. Don plantations of New Zealand although the pathogen has not been recorded here. Mechanisms that may have prevented invasion of the pathogen include geographic isolation, biological characteristics of the fungus, stand management, and regulatory mechanisms affecting transport and establishment. Major factors may include a low probability of importation of infected seedlings, unlikely spore transport in the atmosphere across the tropics, and asynchrony of rust sporulation and pine susceptibility in North America and New Zealand. The outbreak or “wave year” phenomenon in the native range of western gall rust demonstrates that both biological and microclimatic conditions must be suitable for establishment to occur. We conclude that the probability of invasion of New Zealand by western gall rust is very low; however, if the pathogen were to become established in New Zealand, the long-term effects may be large.

A bioeconomic approach to assess the impact of an alien invasive insect on timber supply and harvesting: a case study with Sirex noctilio in eastern Canada
About this Resource: This study presents a model that assesses the potential impact of a new alien insect species, Sirex noctilio Fabricius, on pine timber supply and harvest activities in eastern Canada. We integrate the spread of S. noctilio with a broad-scale growth and harvest allocation model. Projections of pine mortality range between 25 x 10(6) and 115 x 10(6) m3 over 20 years depending on S. noctilio spread and impact assumptions. Our model suggests Ontario could experience the highest, most immediate losses (78% of the potential losses across eastern Canada), with Quebec sustaining most of the rest of the losses over the next 20 years. Potential losses of $86 to $254 million per year are simulated after 20 years. The net present value of total harvest losses after 28 years of outbreak ranges between $0.7 to $2.1 billion. Adaptation policies decrease short-term losses by 46%-55% and delay larger harvest failures by 9-11 years. Without harvest adaptation, failures to maintain annual allowable cut levels may occur once the total area infested exceeds 15 x 106 ha. While better understanding and representing S. noctilio behaviour will involve a significant effort, there is a strong demand by policy makers for this kind of information.

Sycamore and sweetgum plantation productivity on former agricultural land in South Carolina
About this Resource: Former agricultural lands in the southern US comprise a significant land base to support short rotation woody crop (SRWC) plantations. This study presents the seven-year response of productivity and biomass allocation in operational-scale, first rotation sycamore (Plantanus occidentalis L.) and sweetgum (Liquidambar styraciflua L.) plantations that were established on drained Ultisols which were historically planted in cotton and soybeans. Three plantation systems, sycamore open drainage, sycamore plus water management, and sweetgum open drainage were established on replicate 3.5-5.5 ha catchments. Height, diameter, and mortality were measured annually. Allometric equations, based on three, five, and seven year-old trees, were used to estimate aboveground biomass. Below-ground biomass was measured in year-five. Water management did not affect sycamore productivity, probably a result of a 5 year drought. The sycamore plantations were more productive after seven growing seasons than the sweetgum. Sycamore were twice the height (11.6 vs. 5.5 m); fifty percent larger in diameter (10.9 vs. 7.0 cm); and accrued more than twice the biomass (38-42 vs. 17 Mg ha-1) of the sweetgum. Sweetgum plantation productivity was constrained by localized areas of high mortality (up to 88%) and vegetative competition. Mean annual height increment has not culminated for either species. Diameter growth slowed in the sycamore during growing seasons five through seven, but was still increasing in the sweetgum. Both species had similar partitioning of above-ground (60% of total) and below-ground biomass (40% of total).

Invasive plants transform the three-dimensional structure of rain forests
About this Resource: Biological invasions contribute to global environmental change, but the dynamics and consequences of most invasions are difficult to assess at regional scales. We deployed an airborne remote sensing system that mapped the location and impacts of five highly invasive plant species across 221,875 ha of Hawaiian ecosystems, identifying four distinct ways that these species transform the three-dimensional (3D) structure of native rain forests. In lowland to montane forests, three invasive tree species replace native midcanopy and understory plants, whereas one understory invader excludes native species at the ground level. A fifth invasive nitrogen-fixing tree, in combination with a midcanopy alien tree, replaces native plants at all canopy levels in lowland forests. We conclude that this diverse array of alien plant species, each representing a different growth form or functional type, is changing the fundamental 3D structure of native Hawaiian rain forests. Our work also demonstrates how an airborne mapping strategy can identify and track the spread of certain invasive plant species, determine ecological consequences of their proliferation, and provide detailed geographic information to conservation and management efforts.

Post-establishment fertilization of Minnesota hybrid poplar plantations
About this Resource: Experimental plantings were installed at five sites in three locations in western Minnesota. Aboveground biomass production increased 43-82% as a result of three annual applications of urea or balanced nutrient blend fertilizer beginning near canopy closure. There were no production differences between the type of fertilizer used, indicating that N was the major limiting nutrient. Responses were consistent from site to site, indicating that hybrid poplar stands in this region at this stage of development would be very responsive to fertilization. Leaf tissue N, P, and K concentrations increased in response to both fertilizer treatments; P and K increased more frequently in response to the blend treatment compared to the N-only urea treatment. The diagnosis and recommendation integrated system (DRIS) indices indicated that the stands were near optimal nutritional balance prior to fertilization. Treatments increased individual leaf area and leaf litter production up to 33% and 37%, respectively. Canopy leaf area, leaf N concentration and the sum of DRIS indices were correlated with aboveground production. Growth efficiency, the ratio of production to canopy leaf area, increased with both fertilizer treatment and successive years of treatment, indicating improved stand vigor due to nutrient amendments. Stand production increased more in response to changes in leaf N concentration as stands aged. Plantation production continued to increase with increased internal N concentration even when deficiency levels or levels defined as sufficient for fast growth were exceeded. The correlation between aboveground production and the sum of DRIS indices shows that optimal nutrition at canopy closure may result in current aboveground dry matter production exceeding 13 Mg ha-1 yr-1. Multiple small-dose amendments appear to be effective in increasing production by maintaining high internal N concentrations.

Douglas-Fir Beetle Response to Artificial Creation of Down Wood in the Oregon Coast Range.
About this Resource: Douglas-fir beetle populations were monitored before and after thinning and felling of trees to create down wood in an 88-year-old Douglas-fir plantation in the Oregon Coast Range. Treatments included an unthinned control, thinning to a target of 75 trees/ha, and thinning to a target of 150 trees/ha. Actual mean tree densities on the plots after thinning were 406, 102, and 154, for the control, 75 trees/ha, and 150 trees/ha treatments, respectively. Fifty trees/ha were felled and left on all thinned plots to create down wood for ecological values. Catches in pheromone-baited traps indicated that the local beetle population increased for 1 year in response to felling and leaving large diameter trees in partial shade. Douglas-fir beetle entrance holes and brood were significantly more abundant on the sides of felled trees and wood borers were significantly more abundant on the upper surface suggesting that treatments that provide maximum exposure of felled trees will create the least favorable habitat for Douglas-fir beetles. However, there were no differences in Douglas-fir beetle entrance holes or brood densities in felled trees between the two thinning intensities. Douglas-fir beetle-caused tree mortality was significantly higher on thinned plots with residual felled trees compared with unthinned controls, although infestation levels were low on all plots (<2 trees/ha). The small increase in beetle-caused tree mortality associated with leaving felled trees would be unlikely to interfere with resource management objectives. These results are applicable to mature, managed forests west of the Cascades with relatively low Douglas-fir beetle populations. In different regions and stand types, or under different environmental conditions, beetle populations could increase to higher densities, remain at high densities longer, and cause higher levels of tree mortality.

Using airborne lidar to predict Leaf Area Index in cottonwood trees and refine riparian water-use estimates
About this Resource: Estimation of riparian forest structural attributes, such as the Leaf Area Index (LAI), is an important step in identifying the amount of water use in riparian forest areas. In this study, small-footprint lidar data were used to estimate biophysical properties of young, mature, and old cottonwood trees in the Upper San Pedro River Basin, Arizona, USA. Canopy height and maximum and mean laser heights were derived for the cottonwood trees from lidar data. Linear regression models were used to develop equations relating lidar height metrics with corresponding field-measured LAI for each age class of cottonwoods. Four metrics (tree height, height of median energy, ground return ratio, and canopy return ratio) were derived by synthetically constructing a large-footprint lidar waveform from small-footprint lidar data which were compared to ground-based high-resolution Intelligent Laser Ranging and Imaging System (ILRIS) scanner images. These four metrics were incorporated into a stepwise regression procedure to predict field-derived LAI for different age classes of cottonwoods. This research applied the Penman-Monteith model to estimate transpiration of the cottonwoods using lidar-derived canopy metrics. These transpiration estimates compared very well to ground-based sap flux transpiration estimates indicating lidar-derived LAI can be used to improve riparian cottonwood water-use estimates.

Guidelines for Developing and Evaluating Tree Ordinances
About this Resource: This site provides guidelines for developing and evaluating tree ordinances by offering examples of effective tree ordinance provisions and descriptions of methods used to monitor things like community tree resources, tree management activities, and community attitudes. There is information about planning for an ordinance, drafting an ordinance, evaluating the urban forest and ordinance performance, and links to a few special topics. Special topics include information on defining special trees, information about tree banks, and mitigating for tree loss.

Pennsylvania Bureau of Forestry
About this Resource: The site provides information about the Pennsylvania Bureau of Forestry. There is information about recreation, forest health, private forest landowners, forest fire protection, education and information, and state forest management. Quick links include: common trees of Pennsylvania; Hemlock Woolly Adelgid; search and rescue; Pennsylvania Natural Heritage Program; state forest regulations; Pennsylvania urban and Community Forestry Council; research guidelines, and leased forest campsites. There is also a state forest index and information about outdoor activities.

Field efficiency and bias of snag inventory methods.
About this Resource: Snags and cavity trees are important components of forests, but can be difficult to inventory precisely and are not always included in inventories because of limited resources. We tested the application of N-tree distance sampling as a time-saving snag sampling method and compared N-tree distance sampling to fixed-area sampling and modified horizontal line sampling in mixed pine-hardwood forests of southern Maine and New Hampshire. We also present a novel modification of N-tree distance sampling that limits the distance from plot center that an observer must search to find tally trees. A field test shows N-tree to be quick, but generally biased and characterized by high variability. Distance-limited N-tree sampling mitigates these problems, but not completely. We give recommendations for operational snag inventory in similar forest types.

Fates of live trees retained in forest cutting units, western Cascade Range, Oregon
About this Resource: Live trees, standing dead trees, and downed logs have been retained in some forest harvest sites in the Pacific Northwest to fulfill various ecological objectives. To assess the fates of retained trees following partial cutting of mature forests in the central western Cascade Range in Oregon, we inventoried standing live and dead trees and toppled trees in 21 cutting units in 1993 and 2001. In 1993, 1-10 years after cutting, an average of 65% of the initially retained trees (average of counts for all sites) were alive and standing, 12% had been toppled or topped by wind, 13% had become snags by natural processes, and 10% were converted to snags by management action, including cutting, blasting, girdling, and inoculation with fungi. By 2001, when cutting-unit ages ranged from 9 to 18 years, 54% of the retained trees were alive and standing, 10%-21% had been toppled or topped by wind, 11%-22% had become snags by natural processes, and 14% had been converted to snags by management action. The highest levels of mortality occurred at sites with abundant intentional snag creation and (or) prescribed fire following harvest. The rate of mortality due to windthrow declined over time, possibly because the remaining trees were more windfirm.

Integrated analysis of landscape management scenarios using state and transition models in the upper Grande Ronde River Subbasin, Oregon, USA
About this Resource: We modeled the integrated effects of natural disturbances and management activities for three disturbance scenarios on a 178,000 ha landscape in the upper Grande Ronde Subbasin of northeast Oregon. The landscape included three forest environments (warm-dry, cool-moist, and cold) as well as a mixture of publicly and privately owned lands. Our models were state and transition formulations that treat vegetation change as probabilistic transitions among structure and cover types. We simulated background natural disturbance (i.e., historical), active fuel treatment, and fire suppression only disturbance scenarios for 200 or 500 years, depending on scenario. Several interesting landscape hypotheses emerge from our scenario simulations: (1) changes in management approach in landscapes the size of our study area may take decades to play out owing to the time required to grow large trees and the feedback loops among disturbances, (2) the current landscape is considerably different from that which might exist under a natural disturbance regime, (3) fire suppression alone does not mimic background natural disturbances and does not produce abundant large tree structure, and (4) dense, multi-layered large tree forests may be particularly difficult to maintain in abundance in this and similar landscapes owing to wildfire and insect disturbances.

Temporal and Spatial Epidemiology of Phytophthora Root Rot in Fraser Fir Plantations
About this Resource: In 1999, 19 plots of Fraser fir (Abies fraseri) with a disease focus were established in commercial plantings grown for Christmas tree production in the mountains of five western North Carolina counties. Progress of Phytophthora root rot caused by Phytophthora cinnamomi as estimated by mortality was followed in each plot over 3 to 4 years in an attempt to understand dispersal of inoculum. Slope, aspect, and field production age at the time plots were established were recorded. Rainfall estimated from National Weather Service stations each growing season also was recorded. The relationship of site parameters and rainfall to dispersal and disease was investigated. Disease incidence and mortality were assessed in June and September each year for 3 or 4 years depending on plot. Phytophthora root rot as estimated by mortality counts over time in a logistic regression model progressed in only five of 19 plots over 3 years. None of the site parameters correlated with mortality data, although slightly more disease was found in plots with a north aspect. Rainfall was below normal in the 3 years of the study and did not correlate with mortality in any year. Lack of disease progress in the majority of plots was attributed to drought conditions in the region. In the five plots where mortality increased over time, spatial analysis suggested an aggregated pattern of diseased plants. Aggregation was apparent but not very strong among nearest neighbors, but was considerably stronger among groups of trees within a local area. This aggregation within groups was stronger when larger group sizes were examined by beta-binomial analysis. A spatial analysis by distance indices method (SADIE) indicated the presence of secondary clusters occurring several meters away from the main focus. A stochastic model also was employed that indicated a combination of spatial processes were likely involved, specifically a tendency toward spread within a local area, but not necessarily to the nearest neighboring trees, combined with an influence of background inoculum that could not be accounted for within local areas and may have come from external sources. Thus, all sources of inoculum including infected planting stock, inoculum in soil, infected trees, and contaminated equipment were equally important in epidemics of Phytophthora root rot in Fraser fir and dispersal of P. cinnamomi. Additional keywords: disease management, inoculum dispersal, soil moisture.

Forest development following mudflow deposition, Mount St. Helens, Washington
About this Resource: Volcanic mudflows are locally important disturbance agents in the Pacific Northwest rarely studied within the context of forest succession. We describe 18 years (1981-1999) of forest development on the Muddy River mudflow deposit following the 1980 eruption of Mount St. Helens using permanent plot data collected along two transects traversing the Cedar Flats river terrace. We analyze changing forest structure over the study period and compare results with mudflow deposition using correlation and pairwise comparisons, as well as ordination (detrended correspondence analysis) and cluster analysis. Our results show a statistically significant relationship between mudflow deposition and forest change. Following mudflow deposition, the site consisted of patches of high tree mortality caused by deep mudflow deposits in abandoned river channels as well as patches of accelerated regeneration of surviving understory trees in areas of more shallow mudflow deposition and partial overstory mortality. Mudflow deposition at the site initiated multiple stages of stand development with (1) early-colonizing red alder (Alnus rubra Bong.) dominating deep deposition sites with fewer surviving trees, (2) gap recruitment and establishment by western hemlock (Tsuga heterophylla (Raf.) Sarg.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) on intermediate to deep deposition sites with more postburial surviving trees, and (3) late-seral conditions and accelerated succession on shallow burial sites, where tree mortality was low. The initiation of differing succession trajectories, as well as variability in the extent and timing of tree mortality following mudflow deposition, demonstrates a dynamic response to disturbance in relation to small-scale gradients of mudflow deposition.

Nursery Production Publications : Florida Extension Service
About this Resource: A link to the Florida Cooperative Extension publications on the topic of nursery production and nursery crops. A listing from the Electronic Data Information Source (EDIS), supported by the University of Florida's Institute of Food and Agricultural Sciences (UF/IFAS).

Measurement variability error for estimates of volume change
About this Resource: Using quality assurance data, measurement variability distributions were developed for attributes that affect tree volume prediction. Random deviations from the measurement variability distributions were applied to 19 381 remeasured sample trees in Maine. The additional error due to measurement variation and measurement bias was estimated via a simulation study for various components of volume change. In comparison with sampling error, the error due to measurement variation was relatively small. When biases in measurements had contradictory effects on the calculation of individual tree volume, there was little additional error, however, systematic biases produced substantial error increases. The proportion of measurement variation error attributable to diameter at breast height and tree species classification was small relative to that attributable to bole (merchantable) height and percent cull attributes, which composed the preponderance of uncertainty due to measurement variation. The greatest impacts were associated with the accretion component, which was subject to measurement variation and bias at both the initial and subsequent measurements.

Relationships between urbanization and the oak resource of the Minneapolis/St. Paul Metropolitan area from 1991 to 1998
About this Resource: Urbanization was associated with loss and transformation of the oak forest in the Twin Cities (Minneapolis and St. Paul) metropolitan area (TCMA) over a recent 7-year interval. Between 1991 and 1998, urbanization increased based on several indicators: population density, area of developed land, and area of impervious surface---total impervious area and area within three classes of increasing degree of imperviousness (protected, affected, and degraded). We quantified relationships between changes in urbanization and changes in several parameters describing the oak forest at the scale of ecological subsection. Increased total and affected impervious area were strongly correlated with decreased area of oak forest when changes of the urbanization indicators and oak were expressed as percentages of the subsection area. Relationships were reversed when changes were expressed as percentages of the 1991 values. Increased population density was strongly correlated with increased loss in numbers and increased isolation of oak patches, but weakly correlated with loss of oak forest area. This is the first study to quantify relationships between changes in urbanization and changes in a specific forest cover type. Our results demonstrate complexities of urbanization impacts on a metropolitan forest resource, and highlight the importance of selected variables, spatial and temporal scales, and expressions of change when quantifying these relationships.

Simulation of the Consequences of Different Fire Regimes to Support Wildland Fire Use Decisions
About this Resource: The strategy known as wildland fire use, in which lightning-ignited fires are allowed to burn, is rapidly gaining momentum in the fire management community. Managers need to know the consequences of an increase in area burned that might result from an increase in wildland fire use. One concern of land managers as they consider implementing wildland fire use is whether they can meet the goals in the land management plan for the desired distribution of forest structural stages across the landscape with further increases in fire. These questions were explored for a 49,532 ha landscape on the Boise National Forest in Idaho that typically experiences mixed-severity and stand-replacing fires. The landscape simulation model TELSA was used to evaluate how increases in fire frequency and area burned might affect landscape composition and structure. Information about frequency, annual area burned, and size-class distributions of fires derived from a fire atlas for the northern Rocky Mountains were used to define the fire regime parameters for five different simulation scenarios. Scenarios with higher fire frequency and area burned resulted in landscapes dominated by earlier successional forest stages and only small patches occupied by large trees. Simulated variability in area occupied by different tree-size classes on this landscape was much greater than the desired ranges defined in the land management plan for the forest at large. A measure of dissimilarity (Euclidean Distance) from desired composition was used to evaluate scenarios for their relative ability to achieve long term land management goals. The lowest values of Euclidean Distance were for a scenario that represents a substantial increase in fire over 20th century fire regimes. Euclidean Distance increased for scenarios with very high rates of burning, implying an upper limit to the desired amount of fire for this landscape. These findings could be used to develop guidance for achieving desired conditions with wildland fire use.

Historical range of variability in live and dead wood biomass: a regional-scale simulation study
About this Resource: The historical range of variability (HRV) in landscape structure and composition created by natural disturbance can serve as a general guide for evaluating ecological conditions of managed landscapes. HRV approaches to evaluating landscapes have been based on age-classes or developmental stages, which may obscure variation in live and dead stand structure. Developing the HRV of stand structural characteristics would improve the ecological resolution of this coarse-filter approach to ecosystem assessment. We investigated HRV in live and dead wood biomass in the regional landscape of the Oregon Coast Range by integrating stand-level biomass models and a spatially explicit fire simulation model. We simulated historical landscapes of the region for 1000 years under pre-Euro-American settlement fire regimes and calculated biomass as a function of disturbance history. The simulation showed that live and dead wood biomass historically varied widely in time and space. The majority of the forests historically contained 500-700 Mg·ha-1 (50-70 kg·m-2) of live wood and 50-200 Mg·ha-1 (5-20 kg·m-2) of dead wood. The current distributions are more concentrated in much smaller amounts for both biomass types. Although restoring the HRV of forest structure is not necessarily a management goal for most landowners and managing agencies, departure from the reference condition can provide relative measure to evaluate habitat conditions for managers seeking to use forest structure as a means to maintain or restore ecosystem and species diversity.

Regional Height-Diameter Equations for Major Tree Species of Southwest Oregon.
About this Resource: Selected tree height and diameter functions were evaluated for their predictive abilities for major tree species of southwest Oregon. Two sets of equations were evaluated. The first set included four base equations for estimating height as a function of individual tree diameter, and the remaining 16 equations enhanced the four base equations with alternative measures of stand density and relative position. The inclusion of the crown competition factor in larger trees (CCFL) and basal area (BA), which simultaneously indicates the relative position of a tree and stand density, into the base height-diameter equations increased the accuracy of prediction for all species. On the average, root mean square error values were reduced by 45 cm (15% improvement). On the basis of the residual plots and fit statistics, two equations are recommended for estimating tree heights for major tree species in southwest Oregon. The equation coefficients are documented for future use.

Composition and carbon dynamics of forests in northeastern North America in a future, warmer world
About this Resource: Increasing temperatures, precipitation extremes, and other anthropogenic influences (pollutant deposition, increasing carbon dioxide) will influence future forest composition and productivity in the northeastern United States and eastern Canada. This synthesis of empirical and modeling studies includes tree DNA evidence suggesting tree migrations since the last glaciation were much slower, at least under postglacial conditions, than is needed to keep up with current and future climate warming. Exceedances of US and Canadian ozone air quality standards are apparent and offset CO2-induced gains in biomass and predispose trees to other stresses. The deposition of nitrogen and sulfate in the northeastern United States changes forest nutrient availability and retention, reduces reproductive success and frost hardiness, causes physical damage to leaf surfaces, and alters performance of forest pests and diseases. These interacting stresses may increase future tree declines and ecosystem disturbances during transition to a warmer climate. Recent modeling work predicts warmer climates will increase suitable habitat (not necessarily actual distribution) for most tree species in the northeastern United States. Species whose habitat is declining in the northeastern United States currently occur in Canadian forests and may expand northward with warming. Paleoecological studies suggest local factors may interact with, even overwhelm, climatic effects, causing lags and thresholds leading to sudden large shifts in vegetation.

New Hampshire Division of Forests and Lands
About this Resource: The Division of Forests and Lands works to protect and promote the values provided by trees and forests by providing forest resource information and education to the public. The site provides links to news, events, a reference library, employment information, FAQs, and related links. There are also links to the following bureaus: Forest Management Bureau; Forest Protection Bureau; Community Forestry & Stewardship Bureau; Land Management Bureau; and National Heritage Bureau.

Differential impacts of the southern pine beetle, Dendroctonus frontalis, on Pinus palustris and Pinus taeda
About this Resource: Patterns of host use by herbivore pests can have serious consequences for natural and managed ecosystems but are often poorly understood. Here, we provide the first quantification of large differential impacts of the southern pine beetle, Dendroctonus frontalis Zimmermann, on loblolly pine, Pinus taeda L., and longleaf pine, Pinus palustris P. Mill., and evaluate putative mechanisms for the disparity. Spatially extensive survey data from recent epidemics indicate that, per square kilometre, stands of loblolly versus longleaf pine in four forests (380-1273 km2) sustained 3-18 times more local infestations and 3-116 times more tree mortality. Differences were not attributable to size or age structure of pine stands. Using pheromone-baited traps, we found no differences in the abundance of dispersing D. frontalis or its predator Thanasimus dubius Fabricius between loblolly and longleaf stands. Trapping triggered numerous attacks on trees, but the pine species did not differ in the probability of attack initiation or in the surface area of bark attacked by growing aggregations. We found no evidence for postaggregation mechanisms of discrimination or differential success on the two hosts, suggesting that early colonizers discriminate between host species before a pheromone plume is present.

The relative uptake of Ca and Sr into tree foliage using a whole-watershed calcium addition
About this Resource: The use of strontium isotopes and ratios of alkaline earth elements (i.e., ⁸⁷Sr/⁸⁶Sr and Ca/Sr) to trace Ca sources to plants has become common in ecosystem studies. Here we examine the relative uptake of Ca and Sr in trees and subsequent accumulation in foliage. Using a whole-watershed Ca addition experiment at the Hubbard Brook Experimental Forest in N.H., we measured the uptake of Ca relative to Sr in foliage and roots of sugar maple (Acer saccharum), yellow birch (Betula alleghaniensis), American beech (Fagus grandifolia), and red spruce (Picea rubens). Vegetation was analyzed for Ca and Sr concentrations and the ⁸⁷Sr/⁸⁶Sr ratio. A comparison of the Ca/Sr ratio in the vegetation and the Ca/Sr ratio of the applied mineral allows for the calculation of a discrimination factor, which defines whether Ca and Sr are incorporated and allocated in the same ratio as that which is available. A discrimination factor greater than unity indicates preferential uptake of Ca over Sr; a factor less than unity reflects preferential uptake of Sr over Ca. We demonstrate that sugar maple (SM) and yellow birch (YB) have similar and small discrimination factors (1.14 ± 0.12,1σ and 1.16 ± 0.09,1σ) in foliage formation and discrimination factors of less than 1 in root formation (0.55-0.70). Uptake into beech suggests a larger discrimination factor (1.9 ± 1.2) in foliage but a similar root discrimination factor to SM and YB (0.66 ± 0.06,1σ). Incorporation into spruce foliage occurs at a much slower rate than in these other tree species and precludes evaluation of Ca and Sr discrimination in spruce foliage at this time. Understanding the degree to which Ca is fractionated from Sr in different species allows for refinement in the use of ⁸⁷Sr/⁸⁶Sr and Ca/Sr ratios to trace Ca sources to foliage. Methods from this study can be applied to natural environments in which various soil cation pools have different ⁸⁷Sr/⁸⁶Sr and Ca/Sr ratios. The results reported herein have implications for re-evaluating Ca sources and fluxes in forest ecosystems.

Poplar plantation has the potential to alter the water balance in semiarid Inner Mongolia
About this Resource: Poplar plantation is the most dominant broadleaf forest type in northern China. Since the mid-1990s plantation was intensified to combat desertification along China's northwestern border, i.e., within Inner Mongolia (IM). This evoked much concern regarding the ecological and environmental effects on areas that naturally grow grass or shrub vegetation. To highlight potential consequences of large-scale poplar plantations on the water budget within semiarid IM, we compared the growing season water balance (evapotranspiration (ET) and precipitation (PPT)) of a 3-yr old poplar plantation (Kp₃) and a natural shrubland (Ks) in the Kubuqi Desert in western IM, and a 6-yr old poplar plantation (Bp₆) growing under sub-humid climate near Beijing. The results showed that, despite 33% lower PPT at Kp₃, ET was 2% higher at Kp₃ (228 mm) as compared with Ks (223 mm) in May-September 2006. The difference derived mainly from higher ET at the plantation during drier periods of the growing season, which also indicated that the poplars must have partly transpired groundwater. Estimated growing season ET at Bp6 was about 550 mm and more than 100% higher than at Kp₃. It is estimated that increases in leaf area index and net radiation at Kp₃ provide future potential for the poplars in Kubuqi to exceed the present ET and ET of the natural shrubland by 100-200%. These increases in ET are only possible through the permanent use of groundwater either directly by the trees or through increased irrigation. This may significantly change the water balance in the area (e.g., high ET at the cost of a reduction in the water table), which renders large-scale plantations a questionable tool in sustainable arid-land management.

Simulation of the Hydrologic Effects of Afforestation in the Tacuarembver Basin, Uruguay
About this Resource: The Soil and Water Assessment Tool (SWAT) was used to simulate the hydrology of two small paired catchments in northern Uruguay. The control and treatment catchments (69 and 108 ha, respectively) were monitored for a three-year pretreatment period during which the land use was grassland with livestock grazing. Subsequently, the treatment catchment was planted (57% afforested) with loblolly pine ( Pinus taeda ). The objectives of the modeling study were to simulate the hydrologic response of the two catchments during the pretreatment period and predict the hydrologic effects of converting the native pasture to pine plantation. SWAT models of the two catchments were calibrated and validated using data measured during the pretreatment period. The model predicted outflows from the catchments reasonably well as compared to observed outflows during the years with above average rainfall (5% to -13% error). Model efficiency (E) for daily outflow volumes was greater than 0.71, indicating a good fit between simulated and observed results. A 33-year continuous simulation was performed on three land uses: grassland with livestock grazing, grassland without grazing, and pine treatment. The conversion of the catchments from the baseline pasture condition with grazing resulted in a predicted reduction in average annual water yield from the catchments of 15% for native grassland without grazing, and 23% for pine trees. A maximum predicted hydrologic effect was estimated by maximizing the model parameter that increases the ability of pine trees to withdraw water from the ground. For this condition, the model predicted a 30% reduction in mean annual water yield from the afforested catchment.