Amount Of Forest Edge Research Articles

Using Landscape Analysis to Test Hypotheses about Drivers of Tick Abundance and Infection Prevalence with Borrelia burgdorferi.

Patterns of vector-borne disease risk are changing globally in space and time and elevated disease risk of vector-borne infection can be driven by anthropogenic modification of the environment. Incidence of Lyme disease, caused by the bacterium Borrelia burgdorferi sensu stricto, has risen in a number of locations in North America and this increase may be driven by spatially or numerically expanding populations of the primary tick vector, Ixodes scapularis. We used a model selection approach to identify habitat fragmentation and land-use/land cover variables to test the hypothesis that the amount and configuration of forest cover at spatial scales relevant to deer, the primary hosts of adult ticks, would be the predominant determinants of tick abundance. We expected that land cover heterogeneity and amount of forest edge, a habitat thought to facilitate deer foraging and survival, would be the strongest driver of tick density and that larger spatial scales (5–10 km) would be more important than smaller scales (1 km). We generated metrics of deciduous and mixed forest fragmentation using Fragstats 4.4 implemented in ArcMap 10.3 and found, after adjusting for multicollinearity, that total forest edge within a 5 km buffer had a significant negative effect on tick density and that the proportion of forested land cover within a 10 km buffer was positively associated with density of I. scapularis nymphs. None of the 1 km fragmentation metrics were found to significantly improve the fit of the model. Elevation, previously associated with increased density of I. scapularis nymphs in Virginia, while significantly predictive in univariate analysis, was not an important driver of nymph density relative to fragmentation metrics. Our results suggest that amount of forest cover (i.e., lack of fragmentation) is the most important driver of I. scapularis density in our study system.

Patterns of Bat Distribution and Foraging Activity in a Highly Urbanized Temperate Environment.

Understanding how to manage biodiversity in urban areas will become increasingly important as density of humans residing in urban centers increases and urban areas expand. While considerable research has documented the shifts in biodiversity along urbanization gradients, much less work has focused on how characteristics of dense urban centers, effectively novel environments, influence behavior and biodiversity. Urban bats in San Francisco provide an opportunity to document changes in behavior and biodiversity to very high-density development. We studied (1) the distribution and abundance of bat foraging activity in natural areas; and (2) characteristics of natural areas that influence the observed patterns of distribution and foraging activity. We conducted acoustic surveys of twenty-two parks during 2008–2009. We confirmed the presence of four species of bats (Tadarida brasiliensis, Myotis yumanensis, Lasiurus blossevillii, and M. lucifugus). T. brasiliensis were found in all parks, while M. yumanensis occurred in 36% of parks. Results indicate that proximity to water, park size, and amount of forest edge best explained overall foraging activity. Proximity to water best explained species richness. M. yumanensis activity was best explained by reduced proportion of native vegetation as well as proximity to water. Activity was year round but diminished in December. We show that although bats are present even in very densely populated urban centers, there is a large reduction in species richness compared to that of outlying areas, and that most habitat factors explaining their community composition and activity patterns are similar to those documented in less urbanized environments.

The Role of Phragmites australis in Mediating Inland Salt Marsh Migration in a Mid-Atlantic Estuary

Many sea level rise adaptation plans emphasize the protection of adjacent uplands to allow for inland salt marsh migration, but little empirical information exists on this process. Using aerial photos from 1930 and 2006 of Delaware Estuary coastal habitats in New Jersey, I documented the rate of coastal forest retreat and the rate of inland salt marsh migration across 101.1 km of undeveloped salt marsh and forest ecotone. Over this time, the amount of forest edge at this ecotone nearly doubled. In addition, the average amount of forest retreat was 141.2 m while the amount of salt marsh inland migration was 41.9 m. Variation in forest retreat within the study area was influenced by variation in slope. The lag between the amount of forest retreat and salt marsh migration is accounted for by the presence of Phragmites australis which occupies the forest and salt marsh ecotone. Phragmites expands from this edge into forest dieback areas, and the ability of salt marsh to move inland and displace Phragmites is likely influenced by salinity at both an estuary-wide scale and at the scale of local subwatersheds. Inland movement of salt marsh is lowest at lower salinity areas further away from the mouth of the estuary and closer to local heads of tide. These results allow for better prediction of salt marsh migration in estuarine landscapes and provide guidance for adaptation planners seeking to prioritize those places with the highest likelihood of inland salt marsh migration in the near-term.

A synthesis of outcomes from the Warra Silvicultural Systems Trial, Tasmania: safety, timber production, economics, biodiversity, silviculture and social acceptability

Summary The Warra Silvicultural Systems Trial was established in southern Tasmania from 1998 to 2007 in tall wet Eucalyptus obliqua forest to compare seven alternatives to the traditional clear-fell, burn and sow (CBS) harvesting method. The alternatives included CBS with understorey islands, patch-fell, strip-fell, dispersed retention, aggregated retention, single-tree/small-group selection and group selection. The effects of the treatments were compared at age three years against six criteria: safety for harvesting crews, rate of timber recovery, economic returns to the forest owner, old-growth biodiversity, regeneration and growth of eucalypts (silviculture), and social acceptability. Combining all criteria, aggregated retention performed best, and is suggested to be the most suitable alternative for routine use in wet eucalypt forests if a management objective is to maintain old-growth structures and biodiversity at the stand (coupe) level. Aggregated retention presented no novel safety issues even though coupes contained a relatively greater amount of forest edge; harvesting was relatively productive, although total forest management costs increased by about $5 per tonne or cubic metre compared to clear-felling. Biodiversity outcomes were much superior to clear—felling, both at three years of age and (predicted) at rotation age, and the system had greater visual appeal and social acceptability than clear-felling. Regeneration burns in the aggregated retention treatments were operationally more difficult than with clear-felling and were somewhat less effective in creating a suitable seedbed, resulting in lower densities of eucalypt stems in the regenerating forest although stocking standards were still attained. Old-growth biodiversity in commercial forests can be managed at the landscape level, through retention between coupes and through wildlife habitat strips that connect larger ecological reserves. However, internationally there is increasing recognition that maintaining old-growth elements at the coupe level is a worthwhile complementary practice for maintaining biodiversity in commercially-managed native forests. Managers of tall wet eucalypt forests need to balance the difficulties of regeneration burning and costs of aggregated retention against its ecological and social acceptability benefits.

Modeling wildlife damage to crops in northern Indiana

Comprehensive information on crop damage by wildlife species is critical if effective strategies for controlling wildlife damage are to be formulated. Discriminating how landscape composition and configuration attributes influence crop damage is important for implementing landscape management techniques to resolve human-wildlife conflicts. We analyzed crop damage data from 100 corn fields and 60 soybean fields located in the Upper Wabash River Basin of northern Indiana during 2003 and 2004. We used negative binomial regression to model the rate of damage to corn and soybean crops in response to local and landscape variables. Rate of crop damage was best predicted by a combination of local and landscape variables for both corn and soybeans. Models with landscape configuration variables were better able to explain patterns of corn damage, and models with landscape composition variables (specifically, amount of wooded areas) were better able to explain patterns of soybean damage. In general, rate of crop damage was negatively related to size of the crop field and positively related to proportion of a field's perimeter that was adjacent to wooded areas, amount of wooded areas, amount of forest edge, and mean size of forest patches. Specific associations between local and landscape variables and rates of crop damage may serve as a guide to planting strategies and landscape management to minimize wildlife damage to crops.

Spatial simulation of forest succession and timber harvesting using LANDIS

The LANDIS model simulates ecological dynamics, including forest succession, disturbance, seed dispersal and establishment, fire and wind disturbance, and their interactions. We describe the addition to LANDIS of capabilities to simulate forest vegetation management, including harvest. Stands (groups of cells) are prioritized for harvest using one of four ranking algorithms that use criteria related to forest management objectives. Cells within a selected stand are harvested according to the species and age cohort removal rules specified in a prescription. These flexible removal rules allow simulation of a wide range of prescriptions such as prescribed burning, thinning, single-tree selection, and clear-cutting. We present a case study of the application of LANDIS to a managed watershed in the Missouri (U.S.A.) Ozark Mountains to illustrate the utility of this approach to simulate succession as a response to forest management and other disturbance. The different cutting practices produced differences in species and size-class composition, average patch sizes (for patches defined by forest type or by size class), and amount of forest edge across the landscape. The capabilities of LANDIS provide a modeling tool to investigate questions of how timber management changes forest composition and spatial pattern, providing insight into ecological response to forest management.

Predation in heterogeneous forests: A comparison at natural and anthropogenic edges

The boreal mixed-wood forest is a naturally heterogenous system that has an extensive amount of forest edge. Recent increases in timber harvesting as well as oil and gas exploration have imposed an abundance of anthropogenic forest edges across this landscape. Because past research has indicated that songbirds nesting near forest edges can suffer increased nest predation, we conducted an artificial nest experiment to compare predation pressure on songbird populations along natural and anthropogenic edges. Artificial nests were placed in shrubs and on the ground in aspen stands adjacent to: (i) white spruce stands, (ii) clearcuts, (iii) seismic lines, and, (iv) in the interior of aspen stands. In 1995, predation on shrub nests was higher at aspen/seismic line edges, whereas in 1996 it was higher at aspen/white spruce edges. In both years, predation on ground nests was not significantly different among sites. We also examined vegetation at the nest, stand, and landscape scale to determine if these factors affected the probability of predation. Vegetation was not a strong or consistent predictor of predation events at these scales. Predation tended to be higher where there was preferred habitat for nest predators such as red squirrels (Tamiasciurus hudsonius). We encountered a large degree of temporal and spatial variation with this study and we emphasize the importance of long-term studies to separate true effects from stochastic processes. In the short term, the creation of anthropogenic edges in the boreal mixed-wood forest does not appear to cause any relative increase in predator pressure on artificial nests when compared with natural edges or the forest interior.

Simulating Spatial and Temporal Context of Forest Management Using Hypothetical Landscapes

/ Spatially explicit models that combine remote sensing with geographic information systems (GIS) offer great promise to land managers because they consider the arrangement of landscape elements in time and space. Their visual and geographic nature facilitate the comparison of alternative landscape designs. Among various activities associated with forest management, none cause greater concern than the impacts of timber harvesting on the composition, structure, and function of landscape ecosystems. A timber harvest allocation model (HARVEST) was used to simulate different intensities of timber harvest on 23,592-ha hypothetical landscapes with varying sizes of timber production areas and different initial stand age distributions. Our objectives were to: (1) determine the relative effects of the size of timber production areas, harvest intensity, method used to extract timber, and past timber harvest activity on the production of forest interior and edge; and (2) evaluate how past management (in the form of different initial stand age distributions) constrains future timber production options. Our simulations indicated that the total area of forest interior and the amount of forest edge were primarily influenced by the intensity of timber harvest and the size of openings created by harvest. The size of the largest block of interior forest was influenced most by the size of timber harvests, but the intensity of harvest was also significant, and the size of nontimber production areas was important when harvests were numerous and widely dispersed within timber management areas, as is often the case in managed forests. Stand age-class distributions produced by past harvest activity limited the amount of timber production primarily when group selection was used, but also limited clear-cutting when recent harvest levels were high.KEY WORDS: Simulation modeling; Timber harvest; Historical context; Spatial context; Landscape pattern; Forest interior; Forest edge

Effects of landscape patterns on biotic communities

A comparative evaluation was performed using descriptors oflandscape and land cover patterns as to how they relate tovarying levels of anthropogenic disturbance and the structure ofbiotic communities. A spatial analysis program (a modifiedversion of SPAN) was used to compute measures of land coverdiversity, dominance, contagion, scaled dominance and contagion,fractal dimension of land cover patches, mean forest-wetlandpatch size, amount of forest edge, clustering of selected foresttypes, and the largest cover patches within two 100-km2watersheds of the Ridge and Valley province of centralPennsylvania. Landscape pattern analysis was conducted on asubwatershed basis, emphasizing different levels ofresidential-agricultural versus forest land cover, the majordifference between the two watersheds. Bird and vascular plantguilds were chosen to represent the overall biotic community. Thegeneral descriptors of diversity, contagion, mean forest-wetlandpatch size, proportion of forest cover, and the amount of forestedge were most effective in reflecting the disturbance levelswithin the watersheds and changes in guild composition for bothbirds and plants.

Expanding the scale of forest management: allocating timber harvests in time and space

This study examined the effect of clustering timber harvest zones and of changing the land use categories of zones (dynamic zoning) over varying temporal and spatial scales. Focusing on the Hoosier National Forest (HNF) in Indiana, USA as a study area, I used a timber harvest allocation nodel to simulate four management altermatives. In the static zoning alternative, harvests were dispersed throughout the timber harvest land base (65% of HNF) for 15 decades. The three dynamic zoning alternatives varied in the degree to which harvests were clustered in time and space. Two levels of harvest intensity were simulated, and at each level of harvest intensity, the area harvested was held constant among all four zoning alternatives. The dynamic zoning strategies resulted in substantial increases in the amount of forest interior and reductions in the amount of forest edge across the landscape, as well as an increase in the average age of stands when harvested. The greatest reduction in fragmentation was produced by the alternative that most tightly clustered harvests in time and space (i.e. intensive harvesting of small blocks in a relatively short time). When harvest intensity was high, this alternative produced amounts of forest interior and edge comparable to those of the dispersed alternative with half the rate of harvest. The results suggest that the injection of dynamics in specifying disturbance regimes, and the clustering of disturbance in time and space, can be used to sustain larger blocks of mature forest than can static zoning. Dynamic zoning encourages explicit specification of the disturbance regimes that will be imposed across the land base over long periods of time.

Modeling the effects of forest harvesting on landscape structure and the spatial distribution of cowbird brood parasitism

Timber harvesting affects both composition and structure of the landscape and has important consequences for organisms using forest habitats. A timber harvest allocation model was constructed that allows the input of specific rules to allocate forest stands for clearcutting to generate landscape patterns reflecting the “look and feel” of managed landscapes. Various harvest strategies were simulated on four 237 km2 study areas in Indiana, USA. For each study area, the model was applied to simulate 80 years of management activity. The resulting landscape spatial patterns were quantified using a suite of landscape pattern metrics and plotted as a function of mean harvest size and total area of forest harvested per decade to produce response surfaces. When the mean clearcut size was 1 ha, the area of forest interior remaining on the landscape was dramatically reduced and the amount of forest edge on the landscape increased dramatically. The potential consequences of the patterns produced by the model were assessed for a generalized neotropical migrant forest bird using a GIS model that generates maps showing the spatial distribution of the relative vulnerability of forest birds to brood parasitism by brown-headed cowbirds. The model incorporates the location and relative quality of cowbird feeding sites, and the relation between parasitism rates and distance of forest from edge. The response surface relating mean harvest size and total area harvested to the mean value of vulnerability to cowbird brood parasitism had a shape similar to the response surfaces showing forest edge. The results of our study suggest that it is more difficult to maintain large contiguous blocks of undisturbed forest interior when harvests are small and dispersed, especially when producing high timber volumes is a management goal. The application of the cowbird model to landscapes managed under different strategies could help managers in deciding where harvest activity will produce the least negative impact on breeding forest birds.

Large-scale forest fragmentation increases the duration of tent caterpillar outbreak.

I examined historical data (1950-1984) on the duration of outbreaks of the forest tent caterpillar (Malacosoma disstria) in northern Ontario, Canada. Outbreak duration was compared to host tree species dominance and forest structure over large areas of boreal forest partially cleared for agriculture. Abundance of the principal host tree species Populus tremuloides had no consistent effect on duration of outbreak within forest districts, and was negatively correlated with duration of outbreaks among the eight forest districts examined. The amount of forest edge per km2 was the best, and most consistent, predictor of the duration of tent caterpillar outbreaks both within individual forest districts and among forest districts. Because forest tent caterpillar populations are driven largely by the impact of parasitoids and pathogens, results here suggest that large-scale increase in forest fragmentation affects the interaction between these natural enemies and forest tent caterpillar. Increased clearing and fragmentation of boreal forests, by agriculture and forestry, may be exacerbating outbreaks of this forest defoliator.