Revision and application of the LINKAGES model to simulate forest growth in central hardwood landscapes in response to climate change

Context

Global climate change impacts forest growth and methods of modeling those impacts at the landscape scale are needed to forecast future forest species composition change and abundance. Changes in forest landscapes will affect ecosystem processes and services such as succession and disturbance, wildlife habitat, and production of forest products at regional, landscape and global scales.

Objectives

LINKAGES 2.2 was revised to create LINKAGES 3.0 and used it to evaluate tree species growth potential and total biomass production under alternative climate scenarios. This information is needed to understand species potential under future climate and to parameterize forest landscape models (FLMs) used to evaluate forest succession under climate change.

Methods

We simulated total tree biomass and responses of individual tree species in each of the 74 ecological subsections across the central hardwood region of the United States under current climate and projected climate at the end of the century from two general circulation models and two representative greenhouse gas concentration pathways.

Results

Forest composition and abundance varied by ecological subsection with more dramatic changes occurring with greater changes in temperature and precipitation and on soils with lower water holding capacity. Biomass production across the region followed patterns of soil quality.

Conclusions

Linkages 3.0 predicted realistic responses to soil and climate gradients and its application was a useful approach for considering growth potential and maximum growing space under future climates. We suggest Linkages 3.0 can also can used to inform parameter estimates in FLMs such as species establishment and maximum growing space.

     

Modeling and mapping forest diversity in the boreal forest of interior Alaska

Context

Patterns of forest diversity are less well known in the boreal forest of interior Alaska than in most ecosystems of North America. Proactive forest planning requires spatially accurate information about forest diversity. Modeling is a cost-efficient way of predicting key forest diversity measures as a function of human and environmental factors.

Objectives

Investigate and predict the patterns and processes in tree species and tree size-class diversity within the boreal forest of Alaska for a first mapped quantitative baseline.

Methods

For the boreal forest of Alaska, USA, we employed Random Forest Analysis (machine learning) and the Boruta algorithm in R to predict tree species and tree size-class diversity for the entire region using a combination of forest inventory data and a suite of 30 predictors from public open-access data archives that included climatic, distance, and topographic variables. We developed prediction maps in a GIS for the current levels (Year 2012) of tree size-class and species diversity.

Results

The method employed here yielded good accuracy for the huge Alaskan landscape despite the exclusion of spectral reflectance data. It’s the first quantified GIS prediction baseline. The results indicate that the geographic pattern of tree species diversity differs from the pattern of tree size-class diversity across this forest type.

Conclusions

The results suggest that human factors combined with topographical factors had a large impact on predicting the patterns of diversity in the boreal forest of interior Alaska.

     

Topographic variation in the climatic change response of a larch forest in Northeastern China

Context

Due to the spatial heterogeneity of the disturbance regimes and community assemblages along topoclimatic gradients, the response of forest ecosystem to climate change varies at the landscape scale.

Objectives

Our objective was to quantify the possible changes in forest ecosystems and the relative effects of climate warming and fire regime changes in different topographic positions.

Methods

We used a spatially explicit model (LANDIS PRO) combined with a gap model (LINKAGES) to predict the possible response of boreal larch forests to climate and fire regime changes, and examined how this response would vary in different topographic positions.

Results

The result showed that the proportion of landscape occupied by broadleaf species increased under warming climate and frequent fires scenarios. Shifts in species composition were strongly influenced by both climate warming and more frequent fires, while changes in age structure were mainly controlled by shifts in fire regime. These responses varied in the different topographic positions, with forests in valley bottoms being most resilient to climate-fire changes and forests in uplands being more likely to shift their composition from larch-dominant to mixed forests. Such variation in the topographic response may be induced by the heterogeneities of the environmental conditions and fire regime.

Conclusions

Fire disturbance could alter the equilibrium of ecosystems and accelerate the response of forests to climate warming. These effects are largely modulated by topographic variations. Our findings suggest that it is imperative to consider topographic complexities when developing appropriate fire management policies for mitigating the effects of climate change.

     

Bird response to future climate and forest management focused on mitigating climate change

Context

Global temperatures are projected to increase and affect forests and wildlife populations. Forest management can potentially mitigate climate-induced changes through promoting carbon sequestration, forest resilience, and facilitated change.

Objectives

We modeled direct and indirect effects of climate change on avian abundance through changes in forest landscapes and assessed impacts on bird abundances of forest management strategies designed to mitigate climate change effects.

Methods

We coupled a Bayesian hierarchical model with a spatially explicit landscape simulation model (LANDIS PRO) to predict avian relative abundance. We considered multiple climate scenarios and forest management scenarios focused on carbon sequestration, forest resilience, and facilitated change over 100 years.

Results

Management had a greater impact on avian abundance (almost 50% change under some scenarios) than climate (<3% change) and only early successional and coniferous forest showed significant change in percent cover across time. The northern bobwhite was the only species that changed in abundance due to climate-induced changes in vegetation. Northern bobwhite, prairie warbler, and blue-winged warbler generally increased in response to warming temperatures but prairie warbler exhibited a non-linear response and began to decline as summer maximum temperatures exceeded 36 °C at the end of the century.

Conclusion

Linking empirical models with process-based landscape change models can be an effective way to predict climate change and management impacts on wildlife, but time frames greater than 100 years may be required to see climate related effects. We suggest that future research carefully consider species-specific effects and interactions between management and climate.

     

Changes in forest biomass and tree species distribution under climate change in the northeastern United States

Context

Forests in the northeastern United States are currently in early- and mid-successional stages recovering from historical land use. Climate change will affect forest distribution and structure and have important implications for biodiversity, carbon dynamics, and human well-being.

Objective

We addressed how aboveground biomass (AGB) and tree species distribution changed under multiple climate change scenarios (PCM B1, CGCM A2, and GFDL A1FI) in northeastern forests.

Methods

We used the LANDIS PRO forest landscape model to simulate forest succession and tree harvest under current climate and three climate change scenarios from 2000 to 2300. We analyzed the effects of climate change on AGB and tree species distribution.

Results

AGB increased from 2000 to 2120 irrespective of climate scenario, followed by slight decline, but then increased again to 2300. AGB averaged 10 % greater in the CGCM A2 and GFDL A1FI scenarios than the PCM B1 and current climate scenarios. Climate change effects on tree species distribution were not evident from 2000 to 2100 but by 2300 some northern hardwood and conifer species decreased in occurrence and some central hardwood and southern tree species increased in occurrence.

Conclusions

Climate change had positive effects on forest biomass under the two climate scenarios with greatest warming but the patterns in AGB over time were similar among climate scenarios because succession was the primary driver of AGB dynamics. Our approach, which simulated stand dynamics and dispersal, demonstrated that a northward shift in tree species distributions may take 300 or more years.

     

Divergent effects of tropical forest fragmentation and conversion on leaf litter decomposition

Context

In tropical landscapes, dominant land-use changes involve conversion of intact forest to an agricultural matrix with embedded fragments of remnant forest. However, most research to date has focused on how these land-use changes affect species within the fragmented ecosystem, rather than the flux of energy and nutrients within these different landscape elements.

Objectives

We examined how forest fragmentation and conversion to orange fields impact the potential for litter decomposition in a Costa Rican landscape, in particular via effects on macroinvertebrates (MIs) and microclimate.

Methods

We measured mass losses of a standard leaf litter in four habitats: orange fields, small forest fragments, large forest fragments and intact forest. Litter bags were constructed of mesh that either excluded or allowed MIs. Decomposition rates were measured in wet and dry seasons, and at different distances from the forest edge.

Results

Forest fragmentation and forest conversion had divergent effects on decomposition rates. Decomposition rates were 7 % slower in forest fragments during the dry season than in intact forest, and this result was mediated by forest fragmentation effects on MIs. Decomposition rates were 9 % higher in orange fields during the wet season, relative to intact forest, and this pattern was explained by effects of the litter microenvironment on leaching rates or smaller invertebrates. Fragment area and distance from forest edge had minor or undetectable effects on decomposition in fragments.

Conclusions

We conclude that land-use changes affect decomposition processes in both forest and agroecosystems, and these effects can vary in mechanism and direction across disturbed landscapes.

     

The influence of matrix quality on species richness in remnant forest

Context

Habitat destruction is the leading threat to terrestrial biodiversity, isolating remnant habitat in a matrix of modified vegetation.

Objectives

Our goal was to determine how species richness in several broad taxonomic groups from remnant forest was influenced by matrix quality, which we characterized by comparing plant biomass in forest and the surrounding matrix.

Methods

We coupled data on species-area relationships (SARs) in forest remnants from 45 previously published studies with an index of matrix quality calculated using new estimates of plant biomass derived from satellite imagery.

Results

The effect size of SARs was greatest in landscapes with low matrix quality and little forest cover. SARs were generally stronger for volant than for non-volant species. For the terrestrial taxa included in our analysis, matrix quality decreased as the proportion of water, ice, or urbanization in a landscape increased.

Conclusions

We clearly demonstrate that matrix quality plays a major role in determining patterns of species richness in remnant forest. A key implication of our work is that activities that increase matrix quality, such as active and passive habitat restoration, may be important conservation measure for maintaining and restoring biodiversity in modified landscapes.

     

Recovery dynamics and climate change effects to future New England forests

Context

Forests throughout eastern North America continue to recover from broad-scale intensive land use that peaked in the nineteenth century. These forests provide essential goods and services at local to global scales. It is uncertain how recovery dynamics, the processes by which forests respond to past forest land use, will continue to influence future forest conditions. Climate change compounds this uncertainty.

Objectives

We explored how continued forest recovery dynamics affect forest biomass and species composition and how climate change may alter this trajectory.

Methods

Using a spatially explicit landscape simulation model incorporating an ecophysiological model, we simulated forest processes in New England from 2010 to 2110. We compared forest biomass and composition from simulations that used a continuation of the current climate to those from four separate global circulation models forced by a high emission scenario (RCP 8.5).

Results

Simulated forest change in New England was driven by continued recovery dynamics; without the influence of climate change forests accumulated 34 % more biomass and succeed to more shade tolerant species; Climate change resulted in 82 % more biomass but just nominal shifts in community composition. Most tree species increased AGB under climate change.

Conclusions

Continued recovery dynamics will have larger impacts than climate change on forest composition in New England. The large increases in biomass simulated under all climate scenarios suggest that climate regulation provided by the eastern forest carbon sink has potential to continue for at least a century.

     

A disturbance-induced increase in tree species diversity facilitates forest productivity

Context

Natural disturbances can have a considerable negative impact on the productivity of forest landscapes. Yet, disturbances are also important drivers of diversity, with diversity generally contributing positively to forest productivity. While the direct effects of disturbance have been investigated extensively it remains unclear how disturbance-mediated changes in diversity influence landscape productivity. Considering that disturbances are increasing in many ecosystems a better understanding of disturbance impacts is of growing importance for ecosystem management.

Objectives

Here, our objectives were to study the effect of disturbance on tree species diversity at different spatial scales (α and β diversity), and to analyze how a disturbance-mediated variation in tree species diversity affects forest productivity.

Methods

To account for long-term interactions between disturbance, diversity, and productivity and test a range of disturbance scenarios we used simulation modeling, focusing on a temperate forest landscape in Central Europe.

Results

We found an overall positive effect of disturbance on tree species diversity both with regard to α and β diversity, persisting under elevated disturbance frequencies. Productivity was enhanced by within- and between-stand diversity, with the effect of α diversity decreasing and that of β diversity increasing through the successional development. Positive diversity effects were found to be strongly contingent on the available species pool, with landscapes containing species with different life-history strategies responding most strongly to disturbance-mediated diversity.

Conclusions

We conclude that, rather than homogenizing disturbed areas, forest managers should incorporate the diversity created by disturbances into stand development to capitalize on a positive diversity effect on productivity.

     

Linking macrodetritivore distribution to desiccation resistance in small forest fragments embedded in agricultural landscapes in Europe

Purpose

Most of the agricultural landscape in Europe, and elsewhere, consists of mosaics with scattered fragments of semi-natural habitat like small forest fragments. Mutual interactions between forest fragments and agricultural areas influence ecosystem processes such as nutrient cycling, a process strongly mediated by the macrodetritivore community, which is however, poorly studied. We investigated macrodetritivore distribution patterns at local and landscape-level and used a key functional trait (desiccation resistance) to gain mechanistic insights of the putative drivers.

Methods

Macrodetritivores were sampled in forest edges-centres of 224 European forest fragments across 14 landscapes opposing in land use intensity. We used a multilevel analysis of variance to assess the relative contribution of different spatial scales in explaining activity-density and Shannon-diversity of woodlice and millipedes, together with a model-based analysis of the multivariate activity-density data testing the effect on species composition. Secondly, we tested if desiccation resistance of macrodetritivores varied across communities at different spatial scales using linear mixed effect models.

Results

Forest edge-centre and landscape use intensity determined activity-density and community composition of macrodetritivores in forest fragments, while fragment characteristics like size and continuity were relatively unimportant. Forest edges and higher intensity landscapes supported higher activity-density of macrodetritivores and determined species composition. Forest edges sustained woodlouse communities dominated by more drought tolerant species.

Conclusions

Landscape use intensity and forest edges are main drivers in macrodetritivore distribution in forest fragments with desiccation resistance a good predictor of macrodetritivore distribution. Key functional traits can help us to predict changes in community structure in changing landscapes.

     

Spatial dynamics of coastal forest bird assemblages: the influence of landscape context,forest type,and structural connectivity

Context

Complex structural connectivity patterns can influence the distribution of animals in coastal landscapes, particularly those with relatively large home ranges, such as birds. To understand the nuanced nature of coastal forest avifauna, where there may be considerable overlap in assemblages of adjacent forest types, the concerted influence of regional landscape context and vegetative structural connectivity at multiple spatial scales warrants investigation.

Objectives

This study determined whether species compositions of coastal forest bird assemblages differ with regional landscape context or with forest type, and if this is influenced by structural connectivity patterns measured at multiple spatial scales.

Methods

Three replicate bird surveys were conducted in four coastal forest types at ten survey locations across two regional landscape contexts in northeast Australia. Structural connectivity patterns of 11 vegetation types were quantified at 3, 6, and 12 km spatial scales surrounding each survey location, and differences in bird species composition were evaluated using multivariate ordination analysis.

Results

Bird assemblages differed between regional landscape contexts and most coastal forest types, although Melaleuca woodland bird assemblages were similar to those of eucalypt woodlands and rainforests. Structural connectivity was primarily correlated with differences in bird species composition between regional landscape contexts, and correlation depended on vegetation type and spatial scale.

Conclusions

Spatial scale, landscape context, and structural connectivity have a combined influence on bird species composition. This suggests that effective management of coastal landscapes requires a holistic strategy that considers the size, shape, and configuration of all vegetative components at multiple spatial scales.

     

Interactions of landscape disturbances and climate change dictate ecological pattern and process: spatial modeling of wildfire,insect, and disease dynamics under future climates

Context

Interactions among disturbances, climate, and vegetation influence landscape patterns and ecosystem processes. Climate changes, exotic invasions, beetle outbreaks, altered fire regimes, and human activities may interact to produce landscapes that appear and function beyond historical analogs.

Objectives

We used the mechanistic ecosystem-fire process model FireBGCv2 to model interactions of wildland fire, mountain pine beetle (Dendroctonus ponderosae), and white pine blister rust (Cronartium ribicola) under current and future climates, across three diverse study areas.

Methods

We assessed changes in tree basal area as a measure of landscape response over a 300-year simulation period for the Crown of the Continent in north-central Montana, East Fork of the Bitterroot River in western Montana, and Yellowstone Central Plateau in western Wyoming, USA.

Results

Interacting disturbances reduced overall basal area via increased tree mortality of host species. Wildfire decreased basal area more than beetles or rust, and disturbance interactions modeled under future climate significantly altered landscape basal area as compared with no-disturbance and current climate scenarios. Responses varied among landscapes depending on species composition, sensitivity to fire, and pathogen and beetle suitability and susceptibility.

Conclusions

Understanding disturbance interactions is critical for managing landscapes because forest responses to wildfires, pathogens, and beetle attacks may offset or exacerbate climate influences, with consequences for wildlife, carbon, and biodiversity.

     

A multistage decision support framework to guide tree species management under climate change via habitat suitability and colonization models,and a knowledge-based scoring system

Context

No single model can capture the complex species range dynamics under changing climates—hence the need for a combination approach that addresses management concerns.

Objective

A multistage approach is illustrated to manage forested landscapes under climate change. We combine a tree species habitat model—DISTRIB II, a species colonization model—SHIFT, and knowledge-based scoring system—MODFACs, to illustrate a decision support framework.

Methods

Using shortleaf pine (Pinus echinata) and sugar maple (Acer saccharum) as examples, we project suitable habitats under two future climate change scenarios (harsh, Hadley RCP8.5 and mild CCSM RCP4.5 at ~2100) at a resolution of 10 km and assess the colonization likelihood of the projected suitable habitats at a 1 km resolution; and score biological and disturbance factors for interpreting modeled outcomes.

Results

Shortleaf pine shows increased habitat northward by 2100, especially under the harsh scenario of climate change, and with higher possibility of natural migration confined to a narrow region close to the current species range boundary. Sugar maple shows decreased habitat and has negligible possibility of migration within the US due to a large portion of its range being north of the US border. Combination of suitable habitats with colonization likelihoods also allows for identification of potential locations appropriate for assisted migration, should that be deemed feasible.

Conclusion

The combination of these multiple components using diverse approaches leads to tools and products that may help managers make management decisions in the face of a changing climate.

     

Assessing landscape functional connectivity in a forest carnivore using path selection functions

Context

Understanding connectivity patterns in relation to habitat fragmentation is essential to landscape management. However, connectivity is often judged from expert opinion or species occurrence patterns, with very few studies considering the actual movements of individuals. Path selection functions provide a promising tool to infer functional connectivity from animal movement data, but its practical application remains scanty.

Objectives

We aimed to describe functional connectivity patterns in a forest carnivore using path-level analysis, and to explore how connectivity is affected by land cover patterns and road networks.

Methods

We radiotracked 22 common genets in a mixed forest-agricultural landscape of southern Portugal. We developed path selection functions discriminating between observed and random paths in relation to landscape variables. These functions were used together with land cover information to map conductance surfaces.

Results

Genets moved preferentially within forest patches and close to riparian habitats. Functional connectivity declined with increasing road density, but increased with the proximity of culverts, viaducts and bridges. Functional connectivity was favoured by large forest patches, and by the presence of riparian areas providing corridors within open agricultural land. Roads reduced connectivity by dissecting forest patches, but had less effect on riparian corridors due to the presence of crossing structures.

Conclusions

Genet movements were jointly affected by the spatial distribution of suitable habitats, and the presence of a road network dissecting such habitats and creating obstacles in areas otherwise permeable to animal movement. Overall, the study showed the value of path-level analysis to assess functional connectivity patterns in human-modified landscapes.

     

Loss and fragmentation of mature woodland reduce the habitat niche breadth of forest birds

Context

Habitat loss and fragmentation may alter habitat occupancy patterns, for example through a reduction in regional abundance or in functional connectivity, which in turn may reduce the number of dispersers or their ability to prospect for territories. Yet, the relationship between landscape structure and habitat niche remains poorly known.

Objectives

We hypothesized that changes in landscape structure associated with habitat loss and fragmentation will reduce the habitat niche breadth of forest birds, either through a reduction in density-dependent spillover from optimal habitat or by impeding the colonization of patches.

Methods

We surveyed forest birds with point counts in eastern Ontario, Canada, and analyzed their response to loss and fragmentation of mature woodland. We selected 62 landscapes varying in both forest cover (15–45%) and its degree of fragmentation, and classified them into two categories (high versus low levels of loss and fragmentation). We determined the habitat niche breadth of 12 focal species as a function of 8 habitat structure variables for each landscape category.

Results

Habitat niche breadth was narrower in landscapes with high versus low levels of loss and fragmentation of forest cover. The relative occupancy of marginal habitat appeared to drive this relationship. Species sensitivity to mature forest cover had no apparent influence on relative niche breadth.

Conclusions

Regional abundance and, in turn, density-dependent spillover into suboptimal habitat appeared to be determinants of habitat niche breadth. For a given proportion of forest cover, fragmentation also appeared to alter habitat use, which could exacerbate its other negative effects unless functional connectivity is high enough to allow individuals to saturate optimal habitat.

     

Occupancy pattern of a long-horned beetle in a variegated forest landscape: linkages between tree quality and forest cover across spatial scales

Context

Interactions between landscape-scale processes and fine-grained habitat heterogeneity are usually invoked to explain species occupancy in fragmented landscapes. In variegated landscapes, however, organisms face continuous variation in micro-habitat features, which makes necessary to consider ecologically meaningful estimates of habitat quality at different spatial scales.

Objectives

We evaluated the spatial scales at which forest cover and tree quality make the greatest contribution to the occupancy of the long-horned beetle Microplophorus magellanicus (Coleoptera: Cerambycidae) in a variegated forest landscape.

Methods

We used averaged data of tree quality (as derived from remote sensing estimates of the decay stage of single trees) and spatially independent pheromone-baited traps to model the occurrence probability as a function of multiple cross-scale combinations between forest cover and tree quality (with scales ranging between 50 and 400 m).

Results

Model support and performance increased monotonically with the increasing scale at which tree quality was measured. Forest cover was not significant, and did not exhibit scale-specific effects on the occurrence probability of M. magellanicus. The interactive effect between tree quality and forest cover was stronger than the independent (additive) effects of tree quality and particularly forest cover. Significant interactions included tree quality measured at spatial scales ≥200 m, but cross-scale interactions occurred only in four of the seven best-supported models.

Conclusions

M. magellanicus respond to the high-quality trees available in the landscape rather than to the amount of forest per se. Conservation of viable metapopulations of M. magellanicus should consider the quality of trees at spatial scales >200 m.

     

The formulations of site-scale processes affect landscape-scale forest change predictions: a comparison between LANDIS PRO and LANDIS-II forest landscape models

Context

Forest landscape models (FLMs) are important tools for simulating forest changes over broad spatial and temporal scales. The ability of FLMs to accurately predict forest changes may be significantly influenced by the formulations of site-scale processes including seedling establishment, tree growth, competition, and mortality.

Objective

The objectives of this study were to investigate the effects of site-scale processes and interaction effects of site-scale processes and harvest on landscape-scale forest change predictions.

Methods

We compared the differences in species’ distribution (quantified by species’ percent area), total aboveground biomass, and species’ biomass derived from two FLMs: (1) a model that explicitly incorporates stand density and size for each species age cohort (LANDIS PRO), and (2) a model that explicitly tracks biomass for each species age cohort (LANDIS-II with biomass succession extension), which are variants from the LANDIS FLM family with different formulations of site-scale processes.

Results

For early successional species, the differences in simulated distribution and biomass were small (mostly less than 5 %). For mid- to late-successional species, the differences in simulated distribution and biomass were relatively large (10–30 %). The differences in species’ biomass predictions were generally larger than those for species’ distribution predictions. Harvest mediated the differences on landscape-scale predictions.

Conclusions

The effects of site-scale processes on landscape-scale forest change predictions are dependent on species’ ecological traits such as shade tolerance, seed dispersal, and growth rates.

     

Anuran responses to spatial patterns of agricultural landscapes in Argentina

Context

Amphibians are declining worldwide and land use change to agriculture is recognized as a leading cause. Argentina is undergoing an agriculturalization process with rapid changes in landscape structure.

Objectives

We evaluated anuran response to landscape composition and configuration in two landscapes of east-central Argentina with different degrees of agriculturalization. We identified sensitive species and evaluated landscape influence on communities and individual species at two spatial scales.

Methods

We compared anuran richness, frequency of occurrence, and activity between landscapes using call surveys data from 120 sampling points from 2007 to 2009. We evaluated anuran responses to landscape structure variables estimated within 250 and 500-m radius buffers using canonical correspondence analysis and multimodel inference from a set of candidate models.

Results

Anuran richness was lower in the landscape with greater level of agriculturalization with reduced amount of forest cover and stream length. This pattern was driven by the lower occurrence and calling activity of seven out of the sixteen recorded species. Four species responded positively to the amount of forest cover and stream habitat. Three species responded positively to forest cohesion and negatively to rural housing. Two responded negatively to crop area and diversity of cover classes.

Conclusions

Anurans within agricultural landscapes of east-central Argentina are responding to landscape structure. Responses varied depending on species and study scale. Life-history traits contribute to responses differences. Our study offers a better understanding of landscape effects on anurans and can be used for land management in other areas experiencing a similar agriculturalization process.

     

Genetic consequences of forest fragmentation by agricultural land in an arboreal marsupial

Context

Increasing demands on land for agriculture have resulted in large-scale clearance and fragmentation of forests globally. In fragmented landscapes, species that tolerate or exploit the matrix will persist, while those that do not, frequently decline. Knowledge of matrix use is therefore critical to predicting extinction proneness of species in modified landscapes and defining the value of land for conservation management.

Objectives

In a fragmented landscape consisting of seven remnant patches surrounded by agricultural land and a large Eucalyptus forest, we explored (i) population connectivity of common ringtail possums, Pseudocheirus peregrinus, to determine the permeability of the agricultural matrix, and (ii) genetic consequences of forest fragmentation.

Methods

238 common ringtail possums were screened at 14 microsatellite markers and analysed using a range of genetic techniques.

Results

We observed significant genetic differentiation among all patches and limited dispersal through the agricultural matrix, even between neighbouring patches. Consequences of this were a six- to ten-fold increase in genetic dissimilarity over an equivalent geographic distance across patches compared with sites in the continuous forest and a significant reduction in genetic diversity, particularly in patches that were geographically more isolated from their neighbours.

Conclusions

We conclude that the agricultural matrix has a number of characteristics that make it unsuitable for facilitating movement of possums through this landscape, and recommend several management strategies to mitigate the impacts of fragmentation on this and other arboreal species for their conservation.

     

Diversity–disturbance relationship in forest landscapes

Context

Despite decades of research, there is an intense debate about the consistency of the hump-shaped pattern describing the relationship between diversity and disturbance as predicted by the intermediate disturbance hypothesis (IDH). Previous meta-analyses have not explicitly considered interactive effects of disturbance frequency and intensity of disturbance on plant species diversity in terrestrial landscapes.

Objective

We conducted meta-analyses to test the applicability of IDH by simultaneously examining the relationship between species richness, disturbance frequency (quantified as time since last disturbance as originally proposed) and intensity of disturbance in forest landscapes.

Methods

The effects of disturbance frequency, intensity, and their interaction on species richness was evaluated using a mixed-effects model.

Results

We found that species richness peaks at intermediate frequency after both high and intermediate disturbance intensities, but the richness-frequency relationship differed between intensity classes.

Conclusions

Our study highlights the need to measure multiple disturbance components that could help reconcile conflicting empirical results on the effect of disturbance on plant species diversity.