Fire regimes and forest resilience: alternative vegetation states in the West African tropics

Context

Terrestrial ecosystems, including tropical forests, are hypothesized to have tipping points beyond which environmental change triggers rapid and radical shifts to novel alternative states.

Objective

We explored the overarching hypothesis that fire-mediated alternative stable states exist in the semi-deciduous tropical forest zone of Ghana, and that increased fire activity has pushed some forests to a new state in which a novel ecosystem with low tree density is maintained by fire.

Methods

We combined a 30-year time series of remotely-sensed data with field measurements to assess land cover trends, the effects of fire on forest vegetation, and the reciprocal effects of vegetation change on fire regimes, in four forest reserves. We analyzed precipitation trends to determine if shifts in vegetation and fire regime reflected a shift to a drier climate.

Results

Two of the reserves experienced forest loss, were impacted by frequent fires, and transitioned to a vegetation community dominated by shrubs and grasses, which was maintained by fire–vegetation feedbacks. The other two reserves experienced less fire, retained higher levels of forest cover, and resisted fire encroachment from surrounding agricultural areas. Precipitation remained relatively stable, suggesting a hysteresis effect in which different vegetation states and fire regimes coexist within a similar climate.

Conclusion

There is potential for human land use and fire to create novel and persistent non-forest vegetation communities in areas that are climatically suitable for tropical forests. These disturbance-mediated regime shifts should be taken into account when assessing future trajectories of forest landscape change in West Africa.

     

Characterizing combined fire and insect outbreak disturbance regimes in British Columbia,Canada

Context

Fires and insect outbreaks are important agents of forest landscape change, but the classification and distribution of these combined processes remain unstudied aspects of forest disturbance regimes.

Objectives

We sought to map areas of land characterized by homogenous fire regime (HFR) attributes and by distinctive combinations of fire, bark beetles and defoliating insect outbreaks, and how their distribution might change should current climatic trends continue.

Methods

We used a 41-year history of mapped fires and forest insect outbreaks to classify HFRs and combined fire and insect disturbance regimes (HDRs). Spatially constrained cluster analysis of 2524 20-km grid cells used mean annual area burned, ignition Julian date, fire size and fire frequency to delineate HFR zones. Mean annual areas burned, affected by bark beetles, and affected by defoliators were used to delineate HDR zones. Random forests classification used climate associations of HDRs to project likely changes in their distribution.

Results

Eighteen HFR zones accounted for 30% of variance, compared to 27 HDR zones accounting for 59% of variance. Fire regime designation had low predictive power in explaining 23 homogenous insect outbreak regimes or the 27 HDRs. Climate change projections indicate a northward migration of current HDR zones. Conditions suitable for defoliator outbreaks are projected to increase, resulting in a projected increase in the total rate of forest disturbance.

Conclusions

When describing forest disturbance regimes, it is important to consider the combined and possibly interacting agents of tree mortality, which can result in emergent properties not predictable from any single agent.

     

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.

     

Fire legacies impact conifer regeneration across environmental gradients in the U.S. northern Rockies

Context

An increase in the incidence of large wildfires worldwide has prompted concerns about the resilience of forest ecosystems, particularly in the western U.S., where recent changes are linked with climate warming and 20th-century land management practices.

Objectives

To study forest resilience to recent wildfires, we examined relationships among fire legacies, landscape features, ecological conditions, and patterns of post-fire conifer regeneration.

Methods

We quantified regeneration across 182 sites in 21 recent large fires in dry mixed-conifer forests of the U.S. northern Rockies. We used logistic and negative binomial regression to predict the probability of establishment and abundance of conifers 5–13 years post-fire.

Results

Seedling densities varied widely across all sites (0–127,500 seedlings ha^?1) and were best explained by variability in distance to live seed sources (β = ?0.014, p = 0.002) and pre-fire tree basal area (β = 0.072, p = 0.008). Beyond 95 m from the nearest live seed source, the probability of seedling establishment was low. Across all the fires we studied, 75 % of the burned area with high tree mortality was within this 95-m threshold, suggesting the presence of live seed trees to facilitate natural regeneration.  

Conclusions

Combined with the mix of species present within the burn mosaic, dry mixed-conifer forests will be resilient to large fires across our study region, provided that seedlings survive, fire do not become more frequent, high-severity patches do not get significantly larger, and post-fire climate conditions remain suitable for seedling establishment and survival.

     

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.

     

The changing landscape of wildfire: burn pattern trends and implications for California’s yellow pine and mixed conifer forests

Purpose

Wildfire spatial patterns drive ecological processes including vegetation succession and wildlife community dynamics. Such patterns may be changing due to fire suppression policies and climate change, making characterization of trends in post-fire mosaics important for understanding and managing fire-prone ecosystems.

Methods

For wildfires in California’s yellow pine and mixed-conifer forests, spatial pattern trends of two components of the post-fire severity matrix were assessed for 1984–2015: (1) unchanged or very low-severity and (2) high-severity, which represent remnant forest and stand-replacing fire, respectively. Trends were evaluated for metrics of total and proportional burned area, shape complexity, aggregation, and core area. Additionally, comparisons were made between management units where fire suppression is commonly practiced and those with a history of managing wildfire for ecological/resource benefits.

Results

Unchanged or very low-severity area per fire decreased proportionally through time, and became increasingly fragmented. High-severity area and core area increased on average across most of California, with the high-severity component also becoming simpler in shape in the Sierra Nevada. Compared to suppression units, managed wildfire units lack an increase in high-severity area, have less aggregated post-fire mosaics, and more high-severity spatial complexity.

Conclusions

Documented changes in severity patterns have cascading ecological effects including increased vegetation type conversion risk, habitat availability shifts, and remnant forest fragmentation. These changes likely benefit early-seral-associated species at the expense of mature closed-canopy forest-associated species. Managed wildfire appears to moderate some effects of fire suppression, and may help buy time for ecosystems and managers to respond to a changing climate.

     

Bending the carbon curve: fire management for carbon resilience under climate change

Context

Forest landscapes are increasingly managed for fire resilience, particularly in the western US which has recently experienced drought and widespread, high-severity wildfires. Fuel reduction treatments have been effective where fires coincide with treated areas. Fuel treatments also have the potential to reduce drought-mortality if tree density is uncharacteristically high, and to increase long-term carbon storage by reducing high-severity fire probability.

Objective

Assess whether fuel treatments reduce fire intensity and spread and increase carbon storage under climate change.

Methods

We used a simulation modeling approach that couples a landscape model of forest disturbance and succession with an ecosystem model of carbon dynamics (Century), to quantify the interacting effects of climate change, fuel treatments and wildfire for carbon storage potential in a mixed-conifer forest in the western USA.

Results

Our results suggest that fuel treatments have the potential to ‘bend the C curve’, maintaining carbon resilience despite climate change and climate-related changes to the fire regime. Simulated fuel treatments resulted in reduced fire spread and severity. There was partial compensation of C lost during fuel treatments with increased growth of residual stock due to greater available soil water, as well as a shift in species composition to more drought- and fire-tolerant Pinus jeffreyi at the expense of shade-tolerant, fire-susceptible Abies concolor.

Conclusions

Forest resilience to global change can be achieved through management that reduces drought stress and supports the establishment and dominance of tree species that are more fire- and drought-resistant, however, achieving a net C gain from fuel treatments may take decades.

     

Microhabitat conditions and landscape pattern explain nocturnal rodent activity,but not seed removal,in burned and unburned lodgepole pine forests

Context

Disturbances create spatial variation in environments that may influence animal foraging. Granivory by rodents can influence seed supply and thus plant establishment. However, effects of disturbance patterns on rodent seed removal in western North American conifer forests are generally unknown.

Objectives

We conducted a study in lodgepole pine (Pinus contorta var. latifolia) forests of Greater Yellowstone (Wyoming, USA) to answer: (1) How do seed removal and rodent activity vary between recently burned and adjacent unburned forests and with distance from fire perimeter? (2) Which microhabitat conditions explain variability in seed removal and rodent activity?

Methods

One or two years after wildfires, we established transects (n = 23) with four stations each: at 10 and 40 m from the fire perimeter in both burned and unburned forest. At stations, we deployed trays with lodgepole pine seeds and cameras pointed at trays for 28 days and quantified habitat structure and seed abundance.

Results

Seed removal, which averaged 85%, and diurnal rodent activity did not differ between burned and unburned forests or with distance from the fire perimeter; however, nocturnal rodent activity was lower in burned forests. Seed removal and diurnal rodent activity were not associated with any microhabitat conditions we measured. However, nocturnal rodent activity was associated with microhabitat in both burned and unburned forests.

Conclusions

High seed removal rates suggested that rodent foraging was not reduced by high-severity wildfire. If observed seed removal represents natural conditions, post-dispersal seed predation could influence post-fire recruitment of a widespread foundation tree species.

     

Divergent rates of change between tree cover types in a tropical pastoral region

Context

Forest cover change analyses have revealed net forest gain in many tropical regions. While most analyses have focused solely on forest cover, trees outside forests are vital components of landscape integrity. Quantifying regional-scale patterns of tree cover change, including non-forest trees, could benefit forest and landscape restoration (FLR) efforts.

Objectives

We analyzed tree cover change in Southwestern Panama to quantify: (1) patterns of change from 1998 to 2014, (2) differences in rates of change between forest and non-forest classes, and (3) the relative importance of social-ecological predictors of tree cover change between classes.

Methods

We digitized tree cover classes, including dispersed trees, live fences, riparian forest, and forest, in very high resolution images from 1998 to 2014. We then applied hurdle models to relate social-ecological predictors to the probability and amount of tree cover gain.

Results

All tree cover classes increased in extent, but gains were highly variable between classes. Non-forest tree cover accounted for 21% of tree cover gains, while riparian trees constituted 31% of forest cover gains. Drivers of tree cover change varied widely between classes, with opposite impacts of some social-ecological predictors on non-forest and forest cover.

Conclusions

We demonstrate that key drivers of forest cover change, including topography, road distance and historical forest cover, do not explain rates of non-forest tree cover change. Consequently, predictions from medium-resolution forest cover change analyses may not apply to finer-scale patterns of tree cover. We highlight the opportunity for FLR projects to target tree cover classes adapted to local social and ecological conditions.

     

Drivers and trends in landscape patterns of stand-replacing fire in forests of the US Northern Rocky Mountains (1984–2010)

Context

Resilience in fire-prone forests is strongly affected by landscape burn-severity patterns, in part by governing propagule availability around stand-replacing patches in which all or most vegetation is killed. However, little is known about drivers of landscape patterns of stand-replacing fire, or whether such patterns are changing during an era of increased wildfire activity.

Objectives

(a) Identify key direct/indirect drivers of landscape patterns of stand-replacing fire (e.g., size, shape of patches), (b) test for temporal trends in these patterns, and (c) anticipate thresholds beyond which landscape patterns of burn severity may change fundamentally.

Methods

We applied structural equation modeling to satellite burn-severity maps of fires in the US Northern Rocky Mountains (1984–2010) to test for direct and indirect (via influence on fire size and proportion stand-replacing) effects of climate/weather, vegetation, and topography on landscape patterns of stand-replacing fire. We also tested for temporal trends in landscape patterns.

Results

Landscape patterns of stand-replacing fire were strongly controlled by fire size and proportion stand-replacing, which were, in turn, controlled by climate/weather and vegetation/topography, respectively. From 1984 to 2010, the proportion of stand-replacing fire within burn perimeters increased from 0.22 to 0.27. Trends for other landscape metrics were not significant, but may respond to further increases proportion stand-replacing fire.

Conclusions

Fires from 1984 to 2010 exhibited tremendous heterogeneity in landscape patterns of stand-replacing fire, likely promoting resilience in burned areas. If trends continue on the current trajectory, however, fires may produce larger and simpler shaped patches of stand-replacing fire with more burned area far from seed sources.

     

The relative impacts of vegetation,topography and spatial arrangement on building loss to wildfires in case studies of California and Colorado

Context

Wildfires destroy thousands of buildings every year in the wildland urban interface. However, fire typically only destroys a fraction of the buildings within a given fire perimeter, suggesting more could be done to mitigate risk if we understood how to configure residential landscapes so that both people and buildings could survive fire.

Objectives

Our goal was to understand the relative importance of vegetation, topography and spatial arrangement of buildings on building loss, within the fire’s landscape context.

Methods

We analyzed two fires: one in San Diego, CA and another in Boulder, CO. We analyzed Google Earth historical imagery to digitize buildings exposed to the fires, a geographic information system to measure some of the explanatory variables, and FRAGSTATS to quantify landscape metrics. Using logistic regression we conducted an exhaustive model search to select the best models.

Results

The type of variables that were important varied across communities. We found complex spatial effects and no single model explained building loss everywhere, but topography and the spatial arrangement of buildings explained most of the variability in building losses. Vegetation connectivity was more important than vegetation type.

Conclusions

Location and spatial arrangement of buildings affect which buildings burn in a wildfire, which is important for urban planning, building siting, landscape design of future development, and to target fire prevention, fuel reduction, and homeowner education efforts in existing communities. Landscape context of buildings and communities is an important aspect of building loss, and if taken into consideration, could help communities adapt to fire.

     

Spatial and temporal variability of fragmentation effects in a long term,eucalypt forest fragmentation experiment

Context

Although forest fragmentation is generally thought to impact tree growth and mortality negatively, recent work suggests some forests are resilient. Experimental forests provide an opportunity to examine the timing and extent of forest tree resilience to disturbance from fragmentation.

Objectives

We used the Wog Wog Habitat Fragmentation Experiment in southeastern Australia to test Eucalyptus growth and survivorship responses to forest fragmentation over a 26 year period.

Methods

We measured 2418 tree diameters and used spline-regression techniques to examine non-monotonic fragmentation effect over two time periods.

Results

Over the first 4 years after fragmentation, individual eucalypt tree growth was greater than in continuous forest for large trees and mortality rates were higher only within 10 m of edges. Over the following 22 years only the effects on tree growth remained and on average all fragments rebounded so that their biomass and mortality rates were equivalent to continuous forest. Importantly non-monotonic patterns were observed in growth and mortality with respect to area and distance from edge in both study periods, demonstrating that fragmentation impacts on trees can be strong in localized areas (greatest in 3 ha fragments and 0–30 m edges) and over short time periods.

Conclusions

Dry-sclerophyll eucalypt forests join the set of forest types that display resilient growth dynamics post fragmentation. Moreover, persistent non-monotonic impacts on tree growth with respect to tree size, fragment area, and fragment distance from edge, highlighting landscape fragmentation as a driver of habitat heterogeneity within remnant forest fragments.

     

Measuring and managing resistance and resilience under climate change in northern Great Lake forests (USA)

Context

Climate change will have diverse and interacting effects on forests over the next century. One of the most pronounced effects may be a decline in resistance to chronic change and resilience to acute disturbances. The capacity for forests to persist and/or adapt to climate change remains largely unknown, in part because there is not broad agreement how to measure and apply resilience concepts.

Objectives

We assessed the interactions of climate change, resistance, resilience, diversity, and alternative management of northern Great Lake forests.

Methods

We simulated two landscapes (northern Minnesota and northern lower Michigan), three climate futures (current climate, a low emissions trajectory, and a high emissions trajectory), and four management regimes [business as usual, expanded forest reserves, modified silviculture, and climate suitable planting (CSP)]. We simulated each scenario with a forest landscape simulation model. We assessed resistance as the change in species composition over time. We assessed resilience and calculated an index of resilience that incorporated both recovery of pre-fire tree species composition and aboveground biomass within simulated burned areas.

Results

Results indicate a positive relationship between diversity and resistance within low diversity areas. Simulations of the high emission climate future resulted in a decline in both resistance and resilience.

Conclusions

Of the management regimes, the CSP regime resulted in some of the greatest resilience under climate change although our results suggest that differences in forest management are largely outweighed by the effects of climate change. Our results provide a framework for assessing resistance and resilience relevant and valuable to a broad array of ecological systems.

     

Role of past and present landscape structure in determining epiphyte richness in fragmented Mediterranean forests

Context

The anthropocene is characterised by global landscape modification, and the structure of remnant habitats can explain different patterns of species richness. The most pervasive processes of degradation include habitat loss and fragmentation. However, a recovery of modified landscape is occurring in some areas.

Objectives

The main goal is to know how lichen and bryophyte epiphytic richness growing on Mediterranean forests is influenced not only by fragments characteristics but also by the structure of the landscape. We introduce a temporal dimension in order to evaluate if the historical landscape structure is relevant for current epiphytic communities.

Methods

40 well-preserved forest fragments were selected in a landscape with a large habitat loss over decades, but with a recovery of forest surface in the last 55 years. The most relevant fragment and landscape-scale attributes were considered. Some of the variables were measured in three different years to incorporate a temporal framework.

Results

The results showed that variables at fragment scale had a higher influence, whereas variables at the landscape scale were irrelevant. Among all the historical variables analyzed, only the shift in forest fragment size had influence on species richness.

Conclusions

Mediterranean forests had suffered fragmentation along centuries. Their epiphytic communities also suffer the hard conditions of Mediterranean climate. Our results indicate that Mediterranean epiphytic communities may be in a threshold since it they will never be similar to those communities existing previous fragmentation process even a recovery habitat occur or, they may require more time to response to this habitat recovery.

     

Landscape,fire and habitat: which features of recently burned heathland influence site occupancy of an early successional specialist?

Context

Multiple ecological drivers generate spatial patterns in species’ distributions. Changes to natural disturbance regimes can place early successional habitat specialists at an increased risk of extinction by altering landscape patterns of habitat suitability.

Objectives

We developed a series of hypotheses to evaluate the effects of landscape structure, fire history, and site-level habitat quality on site occupancy by an early successional specialist, the eastern chestnut mouse (Pseudomys gracilicaudatus).

Methods

We obtained eight years of monitoring data from 26 sites in recently burned heathland in southeast Australia. We used generalised linear models to determine which explanatory variables were related to occupancy. We also explored predictability in patterns of small mammal species co-occurrence.

Results

Landscape structure (patch area, landscape heterogeneity) was strongly related to site occupancy. Site occupancy was associated with dead shrubs in the understory and rock cover on ground layer, but was not directly influenced by recent or historical fire. Contrary to contemporary ecological theory, we found no predictable species associations in our early successional community.

Conclusions

We recommend surveys take account of landscape configuration and proximity to suitable habitat for optimal results. Fire regimes expected to promote eastern chestnut mouse population growth should encourage the retention of critical habitat features rather than be based on temporal rates of successional stages. For management to adequately account for post-disturbance patterns in early successional communities, a species-by-species, multi-scaled approach to research is necessary.

     

Cumulative patterns of logging and fire (1940–2009): consequences on the structure of the eastern Canadian boreal forest

Context

Although logging has affected circumboreal forest dynamics for nearly a century, very few studies have reconstructed its influence on landscape structure at the subcontinental scale.

Objectives

This study aims to document spatiotemporal patterns of logging and fire since the introduction of logging in the early twentieth-century, and to evaluate the effects of these disturbances on landscape structure.

Methods

We used historical (1940–2009) logging and fire maps to document disturbance patterns across a 195,000-km² boreal forest landscape of eastern Canada. We produced multitemporal (1970s–2010s) mosaics providing land cover status using Landsat imagery.

Results

Logging significantly increased the rate of disturbance (+74 %) in the study area. The area affected by logging increased linearly with time resulting in a significant rejuvenation of the landscape along the harvesting pattern (south–north progression). From 1940 to 2009, fire was the dominant disturbance and showed a more random spatial distribution than logging. The recent increase of fire influence and the expansion of the proportion of area classified as unproductive terrestrial land suggest that regeneration failures occurred.

Conclusions

This study reveals how logging has modified the disturbances dynamics, following the progression of the logging frontier. Future management practices should aim for a dispersed spatial distribution of harvests to generate landscape structures that are closer to natural conditions, in line with ecosystem-based management. The challenges of defining sustainable practices will remain complex with the predicted increase in fire frequency, since this factor, in combination with logging, can alter both the structure and potentially the resilience of boreal forest.

     

Land cover influences boreal-forest fire responses to climate change: geospatial analysis of historical records from Alaska

Context

Wildfire activity in boreal forests is projected to increase dramatically in response to anthropogenic climate change. By altering the spatial arrangement of fuels, land-cover configuration may interact with climate change to influence fire-regime dynamics at landscape and regional scales.

Objectives

We evaluate how land cover interacts with weather conditions to influence boreal-forest burning from 2012 to 2014 in Alaska.

Methods

Using geospatial fire and land-cover data, we quantify relationships between area burned and land cover, and test whether observed patterns of burning differ from random under varying weather conditions and fire sizes.

Results

Mean summer moisture index was correlated with annual area burned (ρ = ?0.78, p < 0.01), the total number of fires (ρ = ?0.68, p = 0.01), and the number of large fires (>500 km²; ρ = ?0.58, p = 0.04). Area burned was related positively to percent cover of coniferous forest and woody wetlands, and negatively to percent cover of shrub scrub, dwarf scrub, and open water and barren areas. Fires preferentially burned coniferous forest, which represented 50.1 % of the area burned in warmer/drier summers and 40.3 % of area burned in cooler/wetter summers, compared to the 34.5 % (±4.2 %) expected by random selection of land-cover classes. Overall vegetation tended to burn more similarly to random in warmer/drier than cooler/wetter years.

Conclusions

Land cover exerted greater influences on boreal fire regimes when weather conditions were less favorable for forest burning. Reliable projections of boreal fire-regime change thus require consideration of the interactions between climate and land cover, as well as feedbacks from land-cover change.

     

The efficacy of protected areas and private land for plant conservation in a fragmented landscape

Context

Protected areas are a cornerstone of the global strategy for conserving biodiversity, and yet their efficacy in comparison to unprotected areas is rarely tested. In the highly fragmented forests of temperate regions, landscape context and forest history may be more important than protection status for plant species diversity.

Objectives

To determine whether there are differences in plant diversity between protected areas and private lands while controlling for landscape context, forest age, and other important factors.

Methods

We used a database of 156 one-hectare forest plots distributed over 120,000 km² in the fragmented forests of southern Ontario to test whether protected areas and private forests differed in native species richness, relative abundance of exotic species, and the probability of finding species of conservation concern.

Results

Plots with more forest on the surrounding landscape had higher native species richness, lower abundance of exotic species, and greater probability of supporting at least one species of conservation concern. Young forests tended to have higher abundance of exotics, and were less likely to support species of conservation concern. Surprisingly, privately owned forests had greater native species richness and were more likely to support species of conservation concern once these other factors were accounted for. In addition, there were significant interactions between ownership type, forest history, and landscape context.

Conclusions

Our results highlight the importance of privately owned forests in this region, and the need to consider forest history and landscape context when comparing the efficacy of protected areas versus private land for sustaining biodiversity.