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Lessons learned from long-term ecosystem research and monitoring in alpine and subalpine basins of the Colorado Rocky Mountains, USA

Long-term ecosystem research and monitoring was begun in the Loch Vale watershed of Rocky Mountain National Park in 1983, after extensive survey work to identify the best location. Then, as now, our scientific objectives were to understand natural biogeochemical cycles and variability, so that we could differentiate ecosystem changes from human-caused disturbances, such as atmospheric deposition of pollutants and climate change. We have learned many lessons, often through our mistakes, that are worth passing on. Clear scientific objectives, even for long-term monitoring, are essential. Standardized methods, including rigorous quality assurance procedures should be adhered to from the beginning of the program. All data, even those collected routinely for background records, should be scrutinized and summarized at least once a year. Freely share basic information such as weather, hydrologic, chemical, and descriptive records with other researchers who can build upon your efforts. Use many tools when asking complex ecological questions, in order to minimize bias toward specific results. Publish frequently; long-term studies do not imply there are no interim conclusions or interesting findings. Interpret findings frequently to policy makers and citizens; increased understanding of the environment and human-caused changes may improve natural resource management, and build support for ecological research. And finally, be persistent. Long-term ecological research can be frustrating and difficult to maintain, yet is often the best way to observe and understand ecological change on a meaningful time scale.

Colorado↗

Chaparral

One of the most dynamic California ecosystems is chaparral. Dominated by evergreen, sclerophyllous shrubs and small trees, chaparral is the most extensive vegetation type in the state (Figure 1). The nearly impenetrable tangle of stiff branches of this unusual vegetation inhibits exploration, and as a consequence the public know little about its natural history and unique characteristics. This under-valued ecosystem is recognized instead by the threat of its extensive, high-intensity canopy-burning wildfires that characterize the dry summer and fall seasons of the state. Because urban areas frequently share borders or intermix with chaparral, societal interests often conflict with conservation of this ecosystem, and understanding its history and dynamics are a key to appreciating its importance. In this chapter we emphasize the principal structure and dynamics of this important ecosystem. The long summer rainless period has strong impacts on all organisms and, importantly, the droughts influence the fire regime that characterizes chaparral. An ecosystem currently characterized by a specific drought and wildfire regime can expect significant impacts from climate change. Because of its dominance at lower elevations, chaparral also is frequently found at or near the boundaries of urban developments and metropolitan centers. Attempts to suppress fire also affect chaparral dynamics in the long absence of fire. The conflicts between the impacts of chaparral wildfire and human life and structures has been an aspect of California’s history since the beginning, but as development encroaches ever more into chaparral regions, the conflicts have increased. Consequently, understanding this vegetation is important not only because of its significance in understanding ecological evolution and the ecological services provided by chaparral, but also because of its direct impacts on human settlements.

Book chapter↗

Pathways of productivity and influences on top consumers in forested streams

Forested stream ecosystems involve complex physical and biotic pathways that can influence fish in numerous ways. Consequently, the responses of fish communities to disturbance can be difficult to understand. In this study, we employed a food web model that links biotic (e.g., physiology, predator–prey interactions) and abiotic (e.g., temperature, sunlight) attributes to address fish responses to changes in stream-riparian ecosystems. We modeled responses to food web dynamics in four streams, using scenarios that included responses to riparian disturbance, climate change, and shifts in top consumers. The two consumers we focused on were coastal cutthroat trout ( Oncorhynchus clarkii clarkii ) and sculpin ( Cottus spp., collectively treated as a functional group) . We found the responses to environmental changes varied by fish species and among streams, and that responses were not independent due to exploitative interspecific competition. Simulations based on long-term data indicated that coastal cutthroat trout were responsive to changes in allochthonous resources including terrestrial detritus and invertebrates, whereas sculpin were more responsive to changes to autochthonous resources that included, periphyton and aquatic invertebrates. These results may be, in part, a consequence of species-specific foraging behavior. Trout have a higher propensity to drift feed and therefore receive a substantial subsidy from terrestrial invertebrates, whereas sculpin feed mostly on aquatic insects on the streambed. Simulations of changes in summer temperature and stream discharge suggest decreased biomass of both fish species because of physiological constraints on invertebrate prey which reduce fish foraging opportunities. Exploitative competition also may be important in fish responses: when one fish taxon was removed, the other showed increased biomass. Although the pattern of simulation results was consistent across the four streams, the magnitude of change varied among streams. Streams with food webs fueled by multiple energy sources may be more resilient to changes to riparian forests and climate. Through application of a systems model, we gained insights into pathways of productivity for fish in forested stream ecosystems that provide understanding of processes that influence fish and streams, as well as implications for management of both.

Forest Ecology and Management↗

Variable climate-growth relationships of quaking aspen (Populus tremuloides) among Sky Island mountain ranges in the Great Basin, Nevada, USA

The Great Basin is an arid province located in the interior western United States. The region encompasses millions of hectares and quaking aspen ( Populus tremuloides Michx.) forests comprise a minor portion of the total area. However, montane aspen forests play a disproportionately large role in providing ecosystem services in the region, including water retention, biodiversity, wildlife habitat, livestock forage, and recreational uses. With warming temperatures, increasing evaporative demand, and heightened precipitation variability, the future of aspen has become a critical concern. Using dendroecological approaches, we assessed growth patterns of 20 aspen stands across three geographically isolated “sky island” mountain ranges spanning portions of the north-central Great Basin. We anticipated that the growth of Great Basin aspen would be strongly influenced by regional climatic patterns and largely in synchrony. Results revealed a more complex growth dynamic that varied among mountain ranges and across environmental gradients. In particular, aspen climate-growth relationships in the slightly dryer Ruby Mountains were strongly and positively correlated (r > 0.5) with previous fall to winter moisture availability. The Jarbidge Mountains had a positive but modest relationship with previous fall to winter moisture availability (r > 0.3). Climate-growth response in the Santa Rosa Mountains, the wettest range, showed no significant response to moisture availability during any time period examined but had greater tree-ring growth with warmer May temperatures. Although tree-ring centennial (1910 – 2010) growth trends were positive for all three mountain ranges, only the Santa Rosa Mountains maintained a positive recent growth trend (1970 – 2010). Moreover, distinct temporal shifts in tree growth-climate relationships in each mountain range suggest potentially unique aspen population adaptations to climate variability. For instance, in two of the mountain ranges, there was a shift from positive/neutral to negative growth relationships with temperature starting around the 1963 – 1987 time period, while tree growth also began simultaneously responding more positively to moisture availability. These growth shifts and observed enhanced sensitivities to monthly and seasonal climate variables over time may reflect dynamic tree growth responses caused by ongoing global climate change, but that may be tempered by local or regional factors, such as the relative availability and timing of soil moisture provided by spring snowmelt. A better understanding of biogeographic variation and causality in aspen growth could provide multiple management pathways governed by resilience characteristics in the face of future anthropogenic and climatic threats.

Nevada↗

Earlier plant growth helps compensate for reduced carbon fixation after 13 years of warming

1. Drylands play a dominant role in global carbon cycling and are particularly vulnerable to increasing temperatures, but our understanding of how dryland ecosystems will respond to climatic change remains notably poor. Considering that the area of drylands is projected to increase 11–23% by 2100, understanding the impacts of warming on the functions and services furnished by these arid and semiarid ecosystems has numerous implications. 2.In a unique 13‐year ecosystem warming experiment in a southwestern U.S. dryland, we investigated the consequences of rising temperature on Achnatherum hymenoides , a widespread, keystone grass species on the Colorado Plateau. We tracked individual‐ and population‐level responses to identify optimal strategies that may have been masked if considering only one level of plant response. 3.We found several factors combined to affect the timing and magnitude of plant responses during the 13 th year of warming. These included large warming‐induced biomass increases for individual plants, an 8.5‐day advancement in the growing season, and strong reductions in photosynthetic rates and population cover. 4.Importantly, we observed a lack of photosynthetic acclimation and, thus, a warming‐induced down regulation of photosynthetic rates. However, these physiological responses were concurrent with warmed‐plant increases in growing season length and investment in photosynthetic surfaces, demonstrating the species' ability to balance carbon fixation limitations with warming. 5.These results, which bring together ecophysiological, phenological, reproductive, and morphological assessments of plant responses to warming, suggest that the extent of change in A. hymenoides populations will be based upon numerous adaptive responses that vary in their direction and magnitude. Plant population responses to climatic warming remain poorly resolved, particularly for Earth's drylands, and our in situ experiment assessing multiple strategies offers a novel look into a warmer world.

Utah↗

Landscape controls on the distribution and ecohydrology of central Oregon springs

Small springs in semiarid landscapes are essential for maintaining aquatic biodiversity and supporting livestock grazing operations. However, little is known about controls on the distribution and physical characteristics of small springs, the aquatic species they support, or their sensitivity to disturbance. We address this information gap in the Crooked River subbasin, a tributary of the Deschutes River in Oregon. We conducted spatial analyses on 2,519 mapped springs to investigate the influence of landscape controls (precipitation and bedrock permeability) on spring density in the Crooked River subbasin and the adjacent Upper Deschutes subbasin. Spring density was highest in areas of low bedrock permeability ( P < 0.0001) and high annual precipitation ( P < 0.0001). We suggest that the high density of small springs on low‐permeability bedrock indicates that these springs generally have short, shallow flow paths and thus may be susceptible to forecasted climate changes. A survey of 137 springs in the Crooked River subbasin revealed the hydrogeologic setting affects spring discharge type ( P = 0.017), temperature ( P = 0.011), and pH ( P = 0.026). We found a high frequency of anthropogenic impacts on springs: 95% of diffuse‐discharge springs and 79% of discrete‐discharge springs were disturbed by livestock grazing. Species inventories at 10 of the most intact surveyed springs confirm that small springs are biologically diverse, with 151 total species of plants and 135 total taxa of macroinvertebrates. Springs in the Crooked River subbasin are ecologically important habitats but require careful management to protect against livestock disturbance and development.

Oregon↗

Ecological insights from three decades of animal movement tracking across a changing Arctic

The Arctic is entering a new ecological state, with alarming consequences for humanity. Animal-borne sensors offer a window into these changes. Although substantial animal tracking data from the Arctic and subarctic exist, most are difficult to discover and access. Here, we present the new Arctic Animal Movement Archive (AAMA), a growing collection of more than 200 standardized terrestrial and marine animal tracking studies from 1991 to the present. The AAMA supports public data discovery, preserves fundamental baseline data for the future, and facilitates efficient, collaborative data analysis. With AAMA-based case studies, we document climatic influences on the migration phenology of eagles, geographic differences in the adaptive response of caribou reproductive phenology to climate change, and species-specific changes in terrestrial mammal movement rates in response to increasing temperature.

Science↗

Fort Collins Science Center fiscal year 2010 science accomplishments

The scientists and technical professionals at the U.S. Geological Survey (USGS), Fort Collins Science Center (FORT), apply their diverse ecological, socioeconomic, and technological expertise to investigate complicated ecological problems confronting managers of the Nation's biological resources. FORT works closely with U.S. Department of the Interior (DOI) agency scientists, the academic community, other USGS science centers, and many other partners to provide critical information needed to help answer complex natural-resource management questions. In Fiscal Year 2010 (FY10), FORT's scientific and technical professionals conducted ongoing, expanded, and new research vital to the science needs and management goals of DOI, other Federal and State agencies, and nongovernmental organizations in the areas of aquatic systems and fisheries, climate change, data and information integration and management, invasive species, science support, security and technology, status and trends of biological resources (including the socioeconomic aspects), terrestrial and freshwater ecosystems, and wildlife resources, including threatened and endangered species. This report presents selected FORT science accomplishments for FY10 by the specific USGS mission area or science program with which each task is most closely associated, though there is considerable overlap. The report also includes all FORT publications and other products published in FY10, as well as staff accomplishments, appointments, committee assignments, and invited presentations.

Open-File Report↗

Pre‐fire drought and competition mediate post‐fire conifer mortality in western U.S. National Parks

Tree mortality is an important outcome of many forest fires. Extensive tree injuries from fire may lead directly to mortality, but environmental and biological stressors may also contribute to tree death. However, there is little evidence showing how the combined effects of two common stressors, drought and competition, influence post‐fire mortality. Geographically broad observations of three common western coniferous trees subjected to prescribed fire showed the likelihood of post‐fire mortality was related to intermediate‐term (10 yr) pre‐fire average radial growth, an important component of tree vigor. Path analysis showed that indices of competition and drought stress prior to fire can be described in terms of joint effects on growth, indirectly affecting post‐fire mortality. Our results suggest that the conditions that govern the relationship between growth and mortality in unburned stands may also apply to post‐fire environments. Thus, biotic and abiotic changes that affect growth negatively (e.g., drought stress) or positively (e.g., growth releases following thinning treatments) prior to fire may influence expressed fire severity, independent of fire intensity (e.g., heat flux, residence time). These relationships suggest that tree mortality may increase under stressful climatic or stand conditions even if fire behavior remains constant.

Ecological Applications↗

Altitudinal migration and the future of an iconic Hawaiian honeycreeper in response to climate change and management

Altitudinal movement by tropical birds to track seasonally variable resources can move them from protected areas to areas of increased vulnerability. In Hawaiʻi, historical reports suggest that many Hawaiian honeycreepers such as the ‘I‘iwi ( Drepanis coccinea ) once undertook seasonal migrations, but the existence of such movements today is unclear. Because Hawaiian honeycreepers are highly susceptible to avian malaria, currently minimal in high-elevation forests, understanding the degree to which honeycreepers visit lower elevation forests may be critical to predict the current impact of malaria on population dynamics and how susceptible bird populations may respond to climate change and mitigation scenarios. Using radio telemetry data, we demonstrate for the first time that a large fraction of breeding adult and juvenile ‘I‘iwi originating from an upper-elevation (1,920 m) population at Hakalau Forest National Wildlife Refuge exhibit post-breeding movements well below the upper elevational limit for mosquitoes. Bloom data suggest seasonal variation in floral resources is the primary driver of seasonal movement for ‘I‘iwi. To understand the demographic implications of such movement, we developed a spatial individual-based model calibrated using previously published and original data. ʻI‘iwi dynamics were simulated backward in time, to estimate population levels in the absence of avian malaria, and forward in time, to assess the impact of climate warming as well as two potential mitigation actions. Even in disease-free ‘refuge’ populations, we found that breeding densities failed to reach the estimated carrying capacity, suggesting the existence of a seasonal “migration load” as a result of travel to disease-prevalent areas. We predict that ‘I‘iwi may be on the verge of extinction in 2100, with the total number of pairs reaching only ~ 0.2–12.3% of the estimated pre-malaria density, based on an optimistic climate change scenario. The probability of extinction of ‘I‘iwi populations, as measured by population estimates for 2100, is strongly related to their estimated migration propensity. Long-term conservation strategies likely will require a multi-pronged response including a reduction of malaria threats, habitat restoration and continued landscape-level access to seasonally variable nectar resources.

Ecological Monographs↗

Freezing temperatures restrict woody plant recruitment and restoration efforts in abandoned montane pastures

Tropical montane forests are being lost at an alarming rate but harbor some of the globe’s most unique biodiversity. The Hawaiian archipelago is a prime example of the importance of high elevation forests to species conservation and persistence as they serve as the last refugia for Hawaiian birds. Yet these forests have been converted to invasive dominated pastures, and efforts to restore them have been met with limited success. Unsuccessful forest restoration may be due to freezing temperatures acting as a demographic bottleneck by killing seedlings recruiting into pastures. We determined freezing tolerances of eight common native woody plants at a high-elevation forest on Hawaiʻi Island and compared these freezing tolerances to two years of site-specific winter temperatures and 17 years of regional temperature records. Low temperature extremes were more severe and common in pastures than under nearby 30-year-old canopy trees. Freezing temperatures over two years were severe enough to damage leaf tissues of six of eight species tested. Those species that displayed the greatest freezing tolerance were also those found naturally recruiting into open pastures. Temperature trends over the past 17 years show monthly minimum temperatures are not increasing as predicted by climate change. Persistent severe freezing events may limit seedling recruitment in the pasture, slowing native woody plant expansion into these abandoned pastures. The species-level differences in freezing tolerance show that current management actions are using species that are at high risk to freezing damage outside of the forest canopy and that alternative species may warrant consideration.

Global Ecology and Conservation↗

A global ecological signal of extinction risk in marine ray-finned fishes (class Actinopterygii)

Many marine fish species are experiencing population declines, but their extinction risk profiles are largely understudied in comparison to their terrestrial vertebrate counterparts. Selective extinction of marine fish species may result in rapid alteration of the structure and function of ocean ecosystems. In this study, we compiled an ecological trait dataset for 8,185 species of marine ray-finned fishes (class Actinopterygii) from FishBase and used phylogenetic generalized linear models to examine which ecological traits are associated with increased extinction risk, based on the International Union for the Conservation of Nature Red List. We also assessed which threat types may be driving these species toward greater extinction risk and whether threatened species face a greater average number of threat types than non-threatened species. We found that larger body size and/or fishes with life histories involving movement between marine, brackish, and freshwater environments are associated with elevated extinction risk. Commercial harvesting threatens the greatest number of species, followed by pollution, development, and then climate change. We also found that threatened species, on average, face a significantly greater number of threat types than non-threatened species. These results can be used by resource managers to help address the heightened extinction risk patterns we found.

Cambridge Prisms: Extinction↗

Resilience of Alaska’s boreal forest to climatic change

This paper assesses the resilience of Alaska&rsquo;s boreal forest system to rapid climatic change. Recent warming is associated with reduced growth of dominant tree species, plant disease and insect outbreaks, warming and thawing of permafrost, drying of lakes, increased wildfire extent, increased postfire recruitment of deciduous trees, and reduced safety of hunters traveling on river ice. These changes have modified key structural features, feedbacks, and interactions in the boreal forest, including reduced effects of upland permafrost on regional hydrology, expansion of boreal forest into tundra, and amplification of climate warming because of reduced albedo (shorter winter season) and carbon release from wildfires. Other temperature-sensitive processes for which no trends have been detected include composition of plant and microbial communities, long-term landscape-scale change in carbon stocks, stream discharge, mammalian population dynamics, and river access and subsistence opportunities for rural indigenous communities. Projections of continued warming suggest that Alaska&rsquo;s boreal forest will undergo significant functional and structural changes within the next few decades that are unprecedented in the last 6000 years. The impact of these social&ndash;ecological changes will depend in part on the extent of landscape reorganization between uplands and lowlands and on policies regulating subsistence opportunities for rural communities.

Alaska↗

Climate and land change impacts on future managed wetland habitat: A case study from California’s Central Valley

Concept California’s Central Valley provides critical habitat for migratory waterbirds, yet only 10% of naturally occurring wetlands remain. Competition for limited water supplies and climate change will impact the long-term viability of these intensively managed habitats. Objectives Forecast the distribution, abundance, and connectivity of surface water and managed wetland habitats, using 5 spatially explicit (270 m 2 ) climate/land use/water prioritization scenarios. Mapping potential future dynamic flooded habitat used by waterbirds and other wetland-dependent wildlife to inform management decisions. Methods We integrated a climate-driven hydrologic water use model with a spatially explicit land change model, to examine stakeholder-driven scenarios of future land change, climate, and water use and their impacts on future habitat availability. Results Declining water availability is the dominant driver of habitat loss across scenarios. The hot/dry scenarios showed the greatest declines in January flooded area by 2101—an important month for overwintering waterbirds. In contrast, higher water supplies in wet climates drive perennial cropland conversion and loss of potential habitat. Potential flooded cropland declined (25 and 33%) under warmer/wetter climate conditions due to this conversion to perennial crops, exposing habitat vulnerability. Conclusion Climate-driven loss of water availability had a greater impact on flooded habitat availability than land-use change. When combined, climate change and the conversion of potentially flooded cropland to perennial cropland will threaten future waterbird habitat particularly in January, the peak of the migratory bird season, even when habitat restoration goals are met. Stakeholder-informed scenario analysis can identify target areas for potential habitat change, vulnerability, and conservation.

California↗

Mississippi’s resiliency and changing environmental conditions

Mississippi is experiencing shifts in environmental conditions, many of which are expected to intensify in the coming decades, and will have important implications for ecosystems, species, and natural resource management across the state. Historical climate analyses and downscaled projections summarized for the state’s Environmental Protection Agency (EPA) level III Ecoregions show that Mississippi will likely face increases in extremely hot days, more intense heatwaves, greater evapotranspiration, and reductions in cold-season extremes. Temperature trends indicate that while Mississippi has warmed relatively little over the last century, recent years have been among the warmest on record. Projections suggest substantial increases in the number of days with maximum temperatures at or above 95°F across all Ecoregions, particularly under higher warming scenarios. Correspondingly, the number of freezing nights is expected to decline, with statewide decreases of 7–21 days depending on the global warming level and timeframe. These combined patterns are likely to reshape habitat conditions, influence species’ thermal stress, and alter ecological processes such as soil moisture retention and stream temperature regimes. Mississippi’s hydrological systems are also expected to be significantly affected. Extreme rainfall events, particularly the most intense 1% of precipitation days, are projected to increase across the state, raising risks of flooding, erosion, and altered stream flow. Coastal Mississippi faces additional stress from sea‑level rise, which is already contributing to more frequent high‑tide flooding; projections show continued increases in inundation risk throughout the century. These flooding patterns, combined with stronger hurricane rainfall rates and the potential for landfalling storms to stall, pose ongoing threats to coastal ecosystems and communities. The state is also vulnerable to extreme weather hazards such as tornadoes. Recent research shows a geographic shift in tornado activity toward the Southeast, with Mississippi experiencing some of the nation’s greatest increases in favorable tornado days and nighttime tornado frequency—hazards that have direct implications for wildlife, habitat stability, and human safety. Drought conditions may intensify as well: higher temperatures and increased evapotranspiration during dry spells could worsen water stress regardless of uncertainty in average annual precipitation. These changing environmental conditions have important consequences for Mississippi’s Species of Greatest Conservation Need (SGCN). Vulnerability assessments and ecological niche models indicate that several fish, mussel, crayfish, plant, amphibian, bird, and mammal species may face heightened stress due to warming temperatures, shifting hydrology, habitat loss, and increases in extreme events. For example, many cold‑water and moisture‑dependent species in the state’s rivers and wetlands are already near their thermal limits, and further warming could reduce suitable habitat. Birds breeding in bottomland hardwood forests, such as the Prothonotary Warbler, are increasingly susceptible to nest loss from flooding. Similarly, species like the Louisiana Black Bear may encounter higher risks from habitat inundation and shifting food availability. The “A Closer Look” section underscores the vulnerability of the Mississippi Alluvial Plain—one of the state’s most ecologically rich yet heavily altered Ecoregions. Its bottomland hardwood forests, wetlands, and floodplain habitats support diverse wildlife but are increasingly threatened by rising temperatures, hydrological changes, development pressures, and compounded disturbances. These habitats provide critical ecosystem services such as water filtration, flood attenuation, and biodiversity support, making their conservation particularly urgent under future conditions. Collectively, these findings indicate that Mississippi’s ongoing and projected environmental changes present both challenges and opportunities for natural resource management. Incorporating adaptation strategies into the State Wildlife Action Plan will be essential for sustaining habitats, mitigating risks, and supporting the long‑term resilience of Mississippi’s wildlife and ecosystems.

Mississippi↗

Assessment of methods for soil monitoring in the Adirondack region of New York

Repeated sampling to detect changes in forest soils was rarely used before 1990, but the value of soil monitoring in understanding environmental change is becoming well established. The growing number of resampling studies has shown that sampling designs and procedures must be adapted to the objectives of the monitoring program and the soils being monitored. In the Adirondack region, current priorities include the response of soils to large increases, and more recently, large decreases in acidic deposition, and changes driven by trending climate such as altered pools of soil organic carbon, as well as other unforeseen factors that will occur in the future. To improve methods and assess the feasibility of long-term soil monitoring in the Adirondack region, the United States Geological Survey (USGS) conducted a pilot project to evaluate a new sampling method for characterizing soils on a watershed basis. Results obtained with this new approach, referred to as the ADK sampling method, was compared to methods used in previous sampling conducted in 2004 as part of the Western Adirondack Stream Survey (WASS), and also to previous high-replication pit sampling in the North and South Tributary watersheds of Buck Creek (North Buck and South Buck). The number of sampling locations and spatial distribution of sampling points within watersheds differed among the methods, although pit excavation was used to obtain samples in all cases. In addition, this investigation evaluated the use of small diameter corers as a means to measure forest floor mass with greater accuracy and precision than commonly used methods such as pit excavation. Sufficient statistical power to detect ecologically relevant changes in upper profile horizons (Oe, Oa and upper 10 cm of the B) were achieved with the ADK sampling method that utilized 18 pit excavations per watershed. The sampling locations were organized within each watershed into three study areas (six sampling locations per study area) that represented the primary types of landscape within the watershed. Sampling at 18 locations per watershed was found to be nearly as effective at detecting changes as sampling at 28 locations per watershed. Numerous significant changes (P < 0.10) were detected with both 18 and 28 sampling locations at sampling intervals of 12 to 16 years. The relationship between soil data obtained with the ADK method and stream chemistry at the base of the watershed suggested that this approach adequately characterized soil variability within the watershed for the purpose of studying soil-stream linkages. Significant changes in upper B horizon calcium (P < 0.10) and Oa horizon aluminum (P < 0.01) were detected when the data from the four WASS watersheds were combined with the two Buck Creek watersheds, which suggested that there would be value in resampling other WASS watersheds previously sampled in 2004 to support a regional assessment. Study results support small diameter cores as a useful method to monitor changes in the organic matter mass of the forest floor. This method showed high reproducibility in repeated sampling tests and lower spatial variability in sample data than traditional approaches when compared on a watershed basis. Soil coring is also faster and requires less equipment than pit excavation methods, which makes it more conducive to sampling over large areas. However, organic matter mass of the forest floor determined by coring was consistently less than the values obtained by the ADK sampling method that used pit sampling and vertical horizon measurements, and also literature values of a previous Adirondack study that utilized pit sampling in which the entire horizon was collected over a measured area. However, a high correlation (R2 = 0.87) occurred between organic matter content (expressed as Mg ha-1) determined by coring and the ADK sampling method. Differing methods with regard to where sample could be collected, and how organic matter was collected for chemical analysis were the likely reasons for differences in quantification of forest floor organic mass. Collection of forest floor cores in conjunction with the ADK method is recommended to provide improved sensitivity in detecting changes in the forest floor in proximity of where full analyses of the soil profile are being done. This duel sampling approach represents an optimized method for measuring and understanding how Adirondack soils will change in the future.

New York↗

Mismatch-induced growth reductions in a clade of Arctic-breeding shorebirds are rarely mitigated by increasing temperatures

In seasonal environments subject to climate change, organisms typically show phenological changes. As these changes are usually stronger in organisms at lower trophic levels than those at higher trophic levels, mismatches between consumers and their prey may occur during the consumers’ reproduction period. While in some species a trophic mismatch induces reductions in offspring growth, this is not always the case. This variation may be caused by the relative strength of the mismatch, or by mitigating factors like increased temperature-reducing energetic costs. We investigated the response of chick growth rate to arthropod abundance and temperature for six populations of ecologically similar shorebirds breeding in the Arctic and sub-Arctic (four subspecies of Red Knot Calidris canutus , Great Knot C . tenuirostris and Surfbird C . virgata ). In general, chicks experienced growth benefits (measured as a condition index) when hatching before the seasonal peak in arthropod abundance, and growth reductions when hatching after the peak. The moment in the season at which growth reductions occurred varied between populations, likely depending on whether food was limiting growth before or after the peak. Higher temperatures led to faster growth on average, but could only compensate for increasing trophic mismatch for the population experiencing the coldest conditions. We did not find changes in the timing of peaks in arthropod availability across the study years, possibly because our series of observations was relatively short; timing of hatching displayed no change over the years either. Our results suggest that a trend in trophic mismatches may not yet be evident; however, we show Arctic-breeding shorebirds to be vulnerable to this phenomenon and vulnerability to depend on seasonal prey dynamics.

Global Change Biology↗

Evaluating density-weighted connectivity of black bears (Ursus americanus) in Glacier National Park with spatial capture–recapture models

Background Improved understanding of wildlife population connectivity among protected area networks can support effective planning for the persistence of wildlife populations in the face of land use and climate change. Common approaches to estimating connectivity often rely on small samples of individuals without considering the spatial structure of populations, leading to limited understanding of how individual movement links to demography and population connectivity. Recently developed spatial capture-recapture (SCR) models provide a framework to formally connect inference about individual movement, connectivity, and population density, but few studies have applied this approach to empirical data to support connectivity planning. Methods We used mark-recapture data collected from 924 genetic detections of 598 American black bears ( Ursus americanus ) in 2004 with SCR ecological distance models to simultaneously estimate density, landscape resistance to movement, and population connectivity in Glacier National Park northwest Montana, USA. We estimated density and movement parameters separately for males and females and used model estimates to calculate predicted density-weighted connectivity surfaces. Results Model results indicated that landscape structure influences black bear density and space use in Glacier. The mean density estimate was 16.08 bears/100 km 2 (95% CI 12.52–20.6) for females and 9.27 bears/100 km 2 (95% CI 7.70–11.14) for males. Density increased with forest cover for both sexes. For male black bears, density decreased at higher grizzly bear ( Ursus arctos ) densities. Drainages, valley bottoms, and riparian vegetation decreased estimates of landscape resistance to movement for male and female bears. For males, forest cover also decreased estimated resistance to movement, but a transportation corridor bisecting the study area strongly increased resistance to movement presenting a barrier to connectivity. Conclusions Density-weighed connectivity surfaces highlighted areas important for population connectivity that were distinct from areas with high potential connectivity. For black bears in Glacier and surrounding landscapes, consideration of both vegetation and valley topography could inform the placement of underpasses along the transportation corridor in areas characterized by both high population density and potential connectivity. Our study demonstrates that the SCR ecological distance model can provide biologically realistic, spatially explicit predictions to support movement connectivity planning across large landscapes.

Montana↗