Cara R. Nelson

Managing the whole landscape: historical, hybrid, and novel ecosystems

The reality confronting ecosystem managers today is one of heterogeneous, rapidly transforming landscapes, particularly in the areas more affected by urban and agricultural development. A landscape management framework that incorporates all systems, across the spectrum of degrees of alteration, provides a fuller set of options for how and when to intervene, uses limited resources more effectively, and increases the chances of achieving management goals. That many ecosystems have departed so substantially from their historical trajectory that they defy conventional restoration is not in dispute. Acknowledging novel ecosystems need not constitute a threat to existing policy and management approaches. Rather, the development of an integrated approach to management interventions can provide options that are in tune with the current reality of rapid ecosystem change.

Conservation science: a 20‐year report card

We conducted an intensive review of conservation science to find out whether the field has tracked priorities over the past 20 years. A total of 628 papers from the literature, for the years 1984, 1994, and 2004, were surveyed. For each paper, we recorded where conservation research was done and what was studied. We found geographic gaps in conservation research, with marine, tundra, and desert biomes being studied less than other systems. We also found taxonomic gaps, with amphibians being understudied as compared to other, less threatened, taxonomic groups. Finally, we discovered that studies of invasive species are still lacking, despite the magnitude of the threat they pose to global biodiversity. Although there was a weak trend towards filling these gaps between 1984 and 2004, progress has been slow. To be more effective, the research community must quickly redirect research to better match conservation priorities.

Implementation of National Fire Plan treatments near the wildland–urban interface in the western United States

Because of increasing concern about the effects of catastrophic wildland fires throughout the western United States, federal land managers have been engaged in efforts to restore historical fire behavior and mitigate wildfire risk. During the last 5 years (2004–2008), 44,000 fuels treatments were implemented across the western United States under the National Fire Plan (NFP). We assessed the extent to which these treatments were conducted in and near the wildland–urban interface (WUI), where they would have the greatest potential to reduce fire risk in neighboring homes and communities. Although federal policies stipulate that significant resources should be invested in the WUI, we found that only 3% of the area treated was within the WUI, and another 8% was in an additional 2.5-km buffer around the WUI, totaling 11%. Only 17% of this buffered WUI is under federal ownership, which significantly limits the ability of federal agencies to implement fire-risk reduction treatments near communities. Although treatments far from the WUI may have some fire mitigation benefits, our findings suggest that greater priority must be given to locating treatments in and near the WUI, rather than in more remote settings, to satisfy NFP goals of reducing fire risk to communities. However, this may require shifting management and policy emphasis from public to private lands.

EDGE‐RELATED RESPONSES OF UNDERSTORY PLANTS TO AGGREGATED RETENTION HARVEST IN THE PACIFIC NORTHWEST

Aggregated retention of overstory trees is now a standard component of timber harvest prescriptions on federal lands in the Pacific Northwest. Patches of remnant forest retained during harvest are thought to enhance the structural and biological diversity of managed forests, but the extent to which they maintain components of the original understory or promote recovery in adjacent harvest areas has not been tested. We examined short-term (1- and 2-yr) responses of understory plants to disturbance and creation of edges in structural retention harvest units at two sites in the western Cascade Range of Washington. Pre- and post-treatment abundance of vascular plants was measured in four (two at each site) 1-ha aggregates (patches of intact forest) and in surrounding harvest areas along sixteen 81 m long transects placed perpendicular to the edges of these aggregates. Two years after treatment, aggregates had gained an average of two forest species (vs. a loss of two in adjacent areas of harvest) and less than one early-seral species (vs. a gain of nine in adjacent areas of harvest). Aggregates supported populations of late-seral species that disappeared from or declined substantially in harvested areas. However, aggregates showed edge-related changes in plant abundance: one third of common understory herbs declined significantly in cover toward the edge, and changes in community composition were distinctly higher withi n5mo f theedge than in the aggregate center. Early-seral species established infre- quently within the aggregates, and only within 10 m of the edge. Herbaceous species generally showed larger declines in abundance with proximity to edge than did shrubs, with declines becoming more prominent over time. Our results suggest that, over short time frames, forest aggregates of one or more hectares may play an important role in maintaining plant species richness and composition in forests managed for timber harvest. Assessing the longer term stability of forest aggregates and the degree to which they influence recovery in adjacent areas of harvest will require continued observation.

Spatial variability in wildfire probability across the western United States

Despitegrowingknowledgeoffire-environmentlinkagesinthewesternUSA,obtainingreliableestimatesof relativewildfirelikelihoodremainsaworkinprogress.Thepurposeofthisstudyistouseupdatedfireobservationsduring a 25-year period and a wide array of environmental variables in a statistical framework to produce high-resolution estimatesofwildfireprobability.UsingtheMaxEntmodellingtechnique,point-sourcefireobservationsthatweresampled from area burned during the 1984-2008 time period were related to explanatory variables representing ignitions, flammable vegetation (i.e. fuels), climate and topography. Model results were used to produce spatially explicit predictions of wildfire probability. To assess the effect of humans on the spatial patterns of wildfire likelihood, we built an alternative model that excluded all variables having a strong anthropogenic imprint. Results showed that wildfire probabilityinthewesternUSAisfarfromuniform,withdifferentareasrespondingtodifferentenvironmentaldrivers.The effect of anthropogenic factors on wildfire probability varied by region but, on the whole, humans appear to inhibit fire activity in the western USA. Our results not only provide what appear to be robust predictions of wildfire likelihood, but also enhance understanding of long-term controls on wildfire activity. In addition, our wildfire probability maps provide betterinformationforstrategicplanningofland-managementactivities,especiallywherefireregimeknowledgeissparse. Additional keywords: climate, fuels, ignitions, MaxEnt algorithm, spatial modelling, topography.

Wildland fire as a self-regulating mechanism: the role of previous burns and weather in limiting fire progression

Theory suggests that natural fire regimes can result in landscapes that are both self-regulating and resilient to fire. For example, because fires consume fuel, they may create barriers to the spread of future fires, thereby regulating fire size. Top-down controls such as weather, however, can weaken this effect. While empirical examples demonstrating this pattern-process feedback between vegetation and fire exist, they have been geographically limited or did not consider the influence of time between fires and weather. The availability of remotely sensed data identifying fire activity over the last four decades provides an opportunity to explicitly quantify-the ability of wildland fire to limit the progression of subsequent fire. Furthermore, advances in fire progression mapping now allow an evaluation of how daily weather as a top-down control modifies this effect. In this study, we evaluated the ability of wildland fire to create barriers that limit the spread of subsequent fire along a gradient representing time between fires in four large study areas in the western United States. Using fire progression maps in conjunction with weather station data, we also evaluated the influence of daily weather. Results indicate that wildland fire does limit subsequent fire spread in all four study areas, but this effect decays over time; wildland fire no longer limits subsequent fire spread 6-18 years after fire, depending on the study area. We also found that the ability of fire to regulate, subsequent fire progression was substantially reduced under extreme conditions compared to moderate weather conditions in all four study areas. This study increases understanding of the spatial feedbacks that can lead to self-regulating landscapes as well as the effects of top-down controls, such as weather, on these feedbacks. Our results will be useful to managers who seek to restore natural fire regimes or to exploit recent burns when managing fire.

Restoration relevance of recent National Fire Plan treatments in forests of the western United States

The US National Fire Plan (NFP) is among the largest forest-restoration initiatives worldwide, removing wild-land fuels on about 11 million hectares and costing over

THINNING AND BURNING RESULT IN LOW-LEVEL INVASION BY NONNATIVE PLANTS BUT NEUTRAL EFFECTS ON NATIVES

6 billion. We evaluated the extent to which areas treated under the NFP – from 2004 to 2008, in forest ecosystems outside the wildland–urban interface in 11 western states (“West”) – were predicted to need restoration, due to disruption of fire regimes and expected fuels buildup. Fuel-reduction treatments were implemented on about 1% of the Wests forested areas. Forty-three percent of the treated area was predicted to have high-restoration need – almost twice as much as expected, given the distribution of these forests. However, an equal amount was in mixed- or uncertain-need forests, and 14% occurred in low-need forests, suggesting that managers need additional information on fire-regime disruptions in some forest ecosystems to help prioritize restoration activities. Only one-quarter of the Wests forested area shows strong evidence of uncharacteristic fuels buildup, which is often emphasized as the primary cause of current wildfire problems, potentially directing attention away from other important drivers such as climate change and an expanding wildland–urban interface.

Gravel-bed river floodplains are the ecological nexus of glaciated mountain landscapes

Many historically fire-adapted forests are now highly susceptible to damage from insects, pathogens, and stand-replacing fires. As a result, managers are employing treatments to reduce fuel loadings and to restore the structure, species, and processes that characterized these forests prior to widespread fire suppression, logging, and grazing. However, the consequences of these activities for understory plant communities are not well understood. We examined the effects of thinning and prescribed fire on plant composition and diversity in Pinus ponderosa forests of eastern Washington (USA). Data on abundance and richness of native and nonnative plants were collected in 70 stands in the Colville, Okanogan, and Wenatchee National Forests. Stands represented one of four treatments: thinning, burning, thinning followed by burning, or control; treatments had been conducted 3-19 years before sampling. Multi-response permutation procedures revealed no significant effect of thinning or burning on understory plant composition. Similarly, there were no significant differences among treatments in cover or richness of native plants. In contrast, nonnative plants showed small, but highly significant, increases in cover and richness in response to both thinning and burning. In the combined treatment, cover of nonnative plants averaged 2% (5% of total plant cover) but did not exceed 7% (16% of total cover) at any site. Cover and richness of nonnative herbs showed small increases with intensity of disturbance and time since treatment. Nonnative plants were significantly less abundant in treated stands than on adjacent roadsides or skid trails, and cover within these potential source areas explained little of the variation in abundance within treated stands. Although thinning and burning may promote invasion of nonnative plants in these forests, our data suggest that their abundance is limited and relatively stable on most sites.

VARIATION IN RESPONSES OF LATE‐SERAL HERBS TO DISTURBANCE AND ENVIRONMENTAL STRESS

Gravel-bed rivers are disproportionately important to regional biodiversity, species interactions, connectivity, and conservation. Gravel-bed river floodplains in mountain landscapes disproportionately concentrate diverse habitats, nutrient cycling, productivity of biota, and species interactions. Although stream ecologists know that river channel and floodplain habitats used by aquatic organisms are maintained by hydrologic regimes that mobilize gravel-bed sediments, terrestrial ecologists have largely been unaware of the importance of floodplain structures and processes to the life requirements of a wide variety of species. We provide insight into gravel-bed rivers as the ecological nexus of glaciated mountain landscapes. We show why gravel-bed river floodplains are the primary arena where interactions take place among aquatic, avian, and terrestrial species from microbes to grizzly bears and provide essential connectivity as corridors for movement for both aquatic and terrestrial species. Paradoxically, gravel-bed river floodplains are also disproportionately unprotected where human developments are concentrated. Structural modifications to floodplains such as roads, railways, and housing and hydrologic-altering hydroelectric or water storage dams have severe impacts to floodplain habitat diversity and productivity, restrict local and regional connectivity, and reduce the resilience of both aquatic and terrestrial species, including adaptation to climate change. To be effective, conservation efforts in glaciated mountain landscapes intended to benefit the widest variety of organisms need a paradigm shift that has gravel-bed rivers and their floodplains as the central focus and that prioritizes the maintenance or restoration of the intact structure and processes of these critically important systems throughout their length and breadth.