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At least 1,333 records · Page 74Linked to original sources
USGS2012

Short seed longevity, variable germination conditions, and infrequent establishment events provide a narrow window for Yucca brevifolia (Agavaceae) recruitment

PREMISE OF THE STUDY: The future of long-lived stand-forming desert plants such as Yucca brevifolia (Joshua tree) has come into question in light of climate variation and landscape-scale disturbances such as wildfire. Understanding plant establishment dynamics is important for mitigating the impacts of disturbances and promoting revegetation. • METHODS: We placed Y. brevifolia seeds in shallow caches and manipulated granivore access, nurse shrub effects, and the season of cache placement to determine conditions for seed germination and seedling establishment. • KEY RESULTS: Greatest seedling emergence occurred during spring and summer, when increased soil moisture was accompanied by warm soil temperatures. Late winter-spring emergence for cached seeds was enhanced beneath shrub canopies, but seedling survival declined beneath shrubs as temperatures increased in spring. Germinability of seed remaining in the soil was reduced from 50-68% after 12 mo residence time in soil and declined to <3% after 40 mo. Following dispersal from parent plants, seeds are either removed by granivores or lose germinability, imposing substantial losses of potential germinants. • CONCLUSIONS: Specific germination and establishment requirements impose stringent limits on recruitment rates for Y. brevifolia. Coupled with infrequent seed availability, the return rates to prefire densities and demographic structure may require decades to centuries, especially in light of potential changes to regional desert climate in combination with the potential for fire recurrence. Demographic patterns are predicted to vary spatially in response to environmental variability that limits recruitment and may already be apparent among extant populations.

American Journal of Botany↗
USGS2018

Historical and projected climate in the northern Rockies Region

Climate influences the ecosystem services we obtain from forest and rangelands. Climate is described by the long-term characteristics of precipitation, temperature, wind, snowfall, and other measures of weather that occur over a long period in a particular place, and is typically expressed as long-term average conditions. Resource management practices are implemented day-to-day in response to weather conditions; resource management strategies and plans are developed using our understanding of climate. With the need to consider climate change in planning and management, an understanding of how climate may change in the future in a resource management planning area is valuable. In this chapter, we present the current understanding of potential changes in climate for the Forest Service, U.S. Department of Agriculture (USFS) Northern Region and the Greater Yellowstone Area (GYA), hereafter called the Northern Rockies region.

Idaho, Montana, Wyoming↗
USGS2014

Lesser prairie-chicken nest site selection, microclimate, and nest survival in association with vegetation response to a grassland restoration program

Climate models predict that the region of the Great Plains Landscape Conservation Cooperative (GPLCC) will experience increased maximum and minimum temperatures, reduced frequency but greater intensity of precipitation events, and earlier springs. These climate changes along with different landscape management techniques may influence the persistence of the lesser prairie-chicken (Tympanuchus pallidicinctus), a candidate for protection under the Endangered Species Act and a priority species under the GPLCC, in positive or negative ways. The objectives of this study were to conduct (1) a literature review of lesser prairie-chicken nesting phenology and ecology, (2) an analysis of thermal aspects of lesser prairie-chicken nest microclimate data, and (3) an analysis of nest site selection, nest survival, and vegetation response to 10 years of tebuthiuron and/or grazing treatments. We found few reports in the literature containing useful data on the nesting phenology of lesser prairie-chickens; therefore, managers must rely on short-term observations and measurements of parameters that provide some predictive insight into climate impacts on nesting ecology. Our field studies showed that prairie-chickens on nests were able to maintain relatively consistent average nest temperature of 31 °C and nest humidities of 56.8 percent whereas average external temperatures (20.3–35.0 °C) and humidities (35.2–74.9 percent) varied widely throughout the 24 hour (hr) cycle. Grazing and herbicide treatments within our experimental areas were designed to be less intensive than in common practice. We determined nest locations by radio-tagging hen lesser prairie-chickens captured at leks, which are display grounds at which male lesser prairie-chickens aggregate and attempt to attract a female for mating. Because nest locations selected by hen lesser prairie-chicken are strongly associated with the lek at which they were captured, we assessed nesting habitat use on the basis of hens captured at individual leks, and then for all leks pooled. There was no clear pattern of selection for treatment type for nest placement among hens associated with individual leks; however, when hens from all leks were pooled, we found nesting lesser prairie-chickens selected control plots for nesting over plots that were grazed, treated with tebuthiuron, or were both grazed and treated with tebuthiuron. Overall, the probability of a nest surviving the incubation period was 0.57 for this study and did not vary significantly among treatment types. In contrast to nesting preference for untreated habitats, lek use exhibited no noticeable selection of treatment type. Over the 10 years of the habitat management study, there was 91 percent less sand shinnery oak (Quercus havardii) in treated areas than untreated areas. The removal of sand shinnery oak made environmental soil moisture more available for grasses and forbs to germinate and grow. Grasses increased by 149 percent and forbs increased by 257 percent in treated areas as compared to untreated areas throughout the study period. Our combined results, including our habitat selection analysis at the individual lek level, indicated that reduced rates of herbicide and short-duration grazing treatments were not detrimental to nesting lesser prairie-chickens and that populations of lesser prairie-chickens in shrub-dominated ecosystems may benefit from reduced rates of herbicide application and short duration of grazing that results in increased habitat heterogeneity.

New Mexico;Texas↗
USGS2019

Soil warming effects on tropical forests with highly weathered soils

The tropics are a region encircling the equator, delineated to the north by the Tropic of Cancer (23°26′14.0″N) and to the south by the Tropic of Capricorn (23°26′14.0″S). While we often think of the tropics as consistently warm and wet throughout the year, in reality, the tropics maintain a myriad of climates. Of the 116 Holdridge life zones (a global bioclimatic classification scheme), the tropics contain more life zones than the sum of all the planet's other geographic regions combined ( Holdridge, 1967 ). In addition to high climatic diversity, the tropics support a wide range of parent materials, landforms, geomorphic characteristics, and soil ages, and maintain all 12 soil types of the USDA soil taxonomy system ( Palm et al., 2007 ; Porder et al., 2007 ; Quesada et al., 2010 ; Richter and Babbar, 1991 ; Sanchez, 1977 ; Soil Survey Staff, 2006 ; Townsend et al., 2008 ). Accordingly, there is no single representative tropical ecosystem. Given the diversity of tropical biomes, this chapter will focus specifically on tropical forested ecosystems and their responses to warming because of their global importance, potential sensitivity to change, and the fact that an improved understanding of how these ecosystems may respond to warmer climate conditions is of significant importance to ecology and society. Furthermore, while generally considering all tropical forest types, emphasis in this chapter is on the humid tropics for which we have most data.

Book chapter↗
USGS2023

Observed and projected functional reorganization of riverine fish assemblages from global change

Climate and land-use/land-cover change (‘global change’) are restructuring biodiversity, globally. Broadly, environmental conditions are expected to become warmer, potentially drier (particularly in arid regions), and more anthropogenically developed in the future, with spatiotemporally complex effects on ecological communities. We used functional traits to inform Chesapeake Bay Watershed fish responses to future climate and land-use scenarios (2030, 2060, and 2090). We modelled the future habitat suitability of focal species representative of key trait axes (substrate, flow, temperature, reproduction, and trophic) and used functional and phylogenetic metrics to assess variable assemblage responses across physiographic regions and habitat sizes (headwaters through large rivers). Our focal species analysis projected future habitat suitability gains for carnivorous species with preferences for warm water, pool habitats, and fine or vegetated substrates. At the assemblage level, models projected decreasing habitat suitability for cold-water, rheophilic, and lithophilic individuals but increasing suitability for carnivores in the future across all regions. Projected responses of functional and phylogenetic diversity and redundancy differed among regions. Lowland regions were projected to become less functionally and phylogenetically diverse and more redundant while upland regions (and smaller habitat sizes) were projected to become more diverse and less redundant. Next, we assessed how this model projected assemblage changes 2005-2030 related to observed time-series trends (1999–2016). Halfway through the initial projecting period (2005–2030), we found observed trends broadly followed modelled patterns of increasing proportions of carnivorous and lithophilic individuals in lowland regions but showed opposing patterns for functional and phylogenetic metrics. Leveraging observed and predicted analyses simultaneously helps elucidate the instances and causes of discrepancies between model predictions and ongoing observed changes. Collectively, results highlight the complexity of global change impacts across broad landscapes that likely relate to differences in assemblages’ intrinsic sensitivities and external exposure to stressors.

Global Change Biology↗
USGS2016

Mechanistic variables can enhance predictive models of endotherm distributions: The American pika under current, past, and future climates

How climate constrains species’ distributions through time and space is an important question in the context of conservation planning for climate change. Despite increasing awareness of the need to incorporate mechanism into species distribution models (SDMs), mechanistic modeling of endotherm distributions remains limited in this literature. Using the American pika ( Ochotona princeps ) as an example, we present a framework whereby mechanism can be incorporated into endotherm SDMs. Pika distribution has repeatedly been found to be constrained by warm temperatures, so we used Niche Mapper, a mechanistic heat-balance model, to convert macroclimate data to pika-specific surface activity time in summer across the western United States. We then explored the difference between using a macroclimate predictor (summer temperature) and using a mechanistic predictor (predicted surface activity time) in SDMs. Both approaches accurately predicted pika presences in current and past climate regimes. However, the activity models predicted 8–19% less habitat loss in response to annual temperature increases of ~3–5 °C predicted in the region by 2070, suggesting that pikas may be able to buffer some climate change effects through behavioral thermoregulation that can be captured by mechanistic modeling. Incorporating mechanism added value to the modeling by providing increased confidence in areas where different modeling approaches agreed and providing a range of outcomes in areas of disagreement. It also provided a more proximate variable relating animal distribution to climate, allowing investigations into how unique habitat characteristics and intraspecific phenotypic variation may allow pikas to exist in areas outside those predicted by generic SDMs. Only a small number of easily obtainable data are required to parameterize this mechanistic model for any endotherm, and its use can improve SDM predictions by explicitly modeling a widely applicable direct physiological effect: climate-imposed restrictions on activity. This more complete understanding is necessary to inform climate adaptation actions, management strategies, and conservation plans.

Global Change Biology↗
USGS2022

The influence of soil development on the depth distribution and structure of soil microbial communities.

Although it has been shown that the interaction of climate and time shape the dynamics of soil organic matter (SOM) storage and preservation in soil, the role of soil microbial communities in this dynamic remains unclear. Microbial communities are present throughout soil profiles and likely play critical roles in SOM and nutrient cycling, however the influence of other factors such as soil development (i.e., age) and the composition SOM on microbial community variation with depth has yet to be quantified. Improving our understanding of the relationship between soil development, soil depth, and microbial communities may provide insight to the critical role they play in cycling and preservation of SOM, as well as more mechanistic predictions of the response of soil communities to change, such as landscape-scale changes in available moisture or temperature regimes. Here we compare soils spanning a soil age by climate gradient (i.e., climo-chronosequence) to better understand the mechanisms which influence soil microbial community structure and the molecular composition of SOM. While we observed little depth-dependence in metrics of microbial community structure (i.e., composition, diversity, dissimilarity) across the range of soil development under a wetter climate, we found significant depth-dependent changes in community metrics under a drier climate, which became more pronounced as soils became older. This shift in bacterial and archaeal community structure and diversity is most apparent below a clay-rich argillic horizon formed in the older, drier soils. The molecular composition of SOM as measured by high resolution mass spectrometry (i.e., FTICR MS) also exhibited similar shifts in composition with soil depth and age. Our results highlight how soil moisture shapes the interaction of soil development, SOM, and microbial community composition. Differences in the moisture regime between our two study sites drives differences in biogeochemical depth gradients and subsequent variation in soil microbes and SOM. This suggests that knowledge of not just the pedogenic trajectory of soil development, but also the spatial position relative to distinct pedogenic features, are important for explaining variations in the depth-dependencies of microbial communities and associated SOM.

California↗
USGS2019

Winter precipitation and summer temperature predict lake water quality at macroscales

Climate change can have strong effects on aquatic ecosystems, including disrupting nutrient cycling and mediating processes that affect primary production. Past studies have been conducted mostly on individual or small groups of ecosystems, making it challenging to predict how future climate change will affect water quality at broad scales. We used a subcontinental-scale database to address three objectives: (1) identify which climate metrics best predict lake water quality, (2) examine whether climate influences different nutrient and productivity measures similarly, and (3) quantify the potential effects of a changing climate on lakes. We used climate data to predict lake water quality in ~11,000 north temperate lakes across 17 U.S. states. We developed a novel machine learning method that jointly models different measures of water quality using 48 climate metrics and accounts for properties inherent in macroscale data (e.g. , spatial autocorrelation). Our results suggest that climate metrics related to winter precipitation and summer temperature were strong predictors of lake nutrients and productivity. However, we found variation in the magnitude and direction of the relationship between climate and water quality. We predict that a likely future climate change scenario of warmer summer temperatures will lead to increased nutrient concentrations and algal biomass across lakes (median ~3%–9% increase), whereas increased winter precipitation will have highly variable effects. Our results emphasize the importance of heterogeneity in the response of individual ecosystems to climate and are a caution to extrapolating relationships across space.

Water Resources Research↗
USGS2017

Octocoral diseases in a changing ocean

Octocorals (Cnidaria, Octocorallia) constitute a geographically widely distributed and common group of marine invertebrates commonly referred to as “soft-corals,” “sea fans,” “horny corals,” “sea feathers,” and “sea plumes.” They are found from shallow coastal habitats to mesophotic and abyssal depths. Octocorals are important members of most Atlantic-Caribbean, Indo-Pacific, and Mediterranean coastal and mesophotic reef communities; however, information about their susceptibility to diseases, predation, and competition, and their relationship with changing environmental conditions is limited. At least 19 diseases have been observed in at least 42 common octocoral species throughout their range. Twelve of these have been reported in the wider Caribbean (CA), one in Brazil (BR), two in the Mediterranean (ME), one in the Eastern Pacific (EP), and three in the western Pacific (WP). Pathogenic and/or environmental causes have been identified for eight diseases, including viruses, terrestrial fungi, protozoans, bacteria and cyanobacteria, filamentous algae, parasitic copepods, and high temperature. Only a few of the suspected pathogens have been tested with Koch’s postulates. At least eight disease outbreaks have led to extensive octocoral mortalities in the CA, ME, BR, and EP with detrimental ecological consequences. The fungal disease Aspergillosis has produced the highest mortalities in the CA and the EP. Other fungi, protozoans, and the bacterium Vibrio coralliilyticus were identified as potential causes of the death of millions of colonies in two Mediterranean disease outbreaks. Bacterial and fungal agents seemed to be responsible for the mass mortalities in Brazil and the WP. Most outbreaks in all regions were linked to high thermal anomalies associated with climate change, which seems to be the major driver. Other biological stressors such as predation and/or competition produce injuries that may contribute to the spread of infections and mortality. Overfishing of common predators could lead to population explosions of octocoral-feeding species that produced mass mortalities in some Caribbean localities. Our lack of knowledge of causes and pathogenesis of octocoral diseases parallels that of hard corals. New diseases are being described almost every year concomitant with increasing seawater temperatures. The ecological and economic consequences could be significant, with drastic changes in the seascape of shallow coral reefs and other coastal marine habitats and reduction of their ecological services. Given our limited knowledge, our best options for recovery of octocorals and coral reefs in general include sound management of coastal fisheries, development and tourism; reduction of land- and sea-based pollution; and abating effects of climate change.

Book chapter↗
USGS2018

Patterns of longer-term climate change effects on CO2 efflux from biocrusted soils differ from those observed in the short term

Biological soil crusts (biocrusts) are predicted to be sensitive to the increased temperature and altered precipitation associated with climate change. We assessed the effects of these factors on soil carbon dioxide (CO 2 ) balance in biocrusted soils using a sequence of manipulations over a 9-year period. We warmed biocrusted soils by 2 and, later, by 4 °C to better capture updated forecasts of future temperature at a site on the Colorado Plateau, USA. We also watered soils to alter monsoon-season precipitation amount and frequency and had plots that received both warming and altered precipitation treatments. Within treatment plots, we used 20 automated flux chambers to monitor net soil exchange (NSE) of CO 2 hourly, first in 2006–2007 and then again in 2013–2014, for a total of 39 months. Net CO 2 efflux from biocrusted soils in the warming treatment increased a year after the experiment began (2006–2007). However, after 9 years and even greater warming (4 °C), results were more mixed, with a reversal of the increase in 2013 (i.e., controls showed higher net CO 2 efflux than treatment plots) and with similarly high rates in all treatments during 2014, a wet year. Over the longer term, we saw evidence of reduced photosynthetic capacity of the biocrusts in response to both the temperature and altered precipitation treatments. Patterns in biocrusted soil CO 2 exchange under experimentally altered climate suggest that (1) warming stimulation of CO 2 efflux was diminished later in the experiment, even in the face of greater warming; and (2) treatment effects on CO 2 flux patterns were likely driven by changes in biocrust species composition and by changes in root respiration due to vascular plant responses.

Biogeosciences↗
USGS2021

Life-history attributes of Arctic-breeding birds drive uneven responses to environmental variability across different phases of the reproductive cycle

Animals exhibit varied life-history traits that reflect adaptive responses to their environments. For Arctic-breeding birds, traits related to diet, egg nutrient allocation, clutch size, and chick growth are predicted to be under increasing selection pressure due to rapid climate change and increasing environmental variability across high-latitude regions. We compared four migratory birds (black brant [ Branta bernicla nigricans ], lesser snow geese [ Chen caerulescens caerulescens ], semipalmated sandpipers [ Calidris pusilla ], and Lapland longspurs [ Calcarius lapponicus ]) with varied life histories at an Arctic site in Alaska, USA, to understand how life-history traits help moderate environmental variability across different phases of the reproductive cycle. We monitored aspects of reproductive performance related to the timing of breeding, reproductive investment, and chick growth from 2011 to 2018. In response to early snowmelt and warm temperatures, semipalmated sandpipers advanced their site arrival and bred in higher numbers, while brant and snow geese increased clutch sizes; all four species advanced their nest initiation dates. During chick rearing, longspur nestlings were relatively resilient to environmental variation, whereas warmer temperatures increased the growth rates of sandpiper chicks but reduced growth rates of snow goose goslings. These responses generally aligned with traits along the capital-income spectrum of nutrient acquisition and altricial–precocial modes of chick growth. Under a warming climate, the ability to mobilize endogenous reserves likely provides geese with relative flexibility to adjust the timing of breeding and the size of clutches. Higher temperatures, however, may negatively affect the quality of herbaceous foods and slow gosling growth. Species may possess traits that are beneficial during one phase of the reproductive cycle and others that may be detrimental at another phase, uneven responses that may be amplified with future climate warming. These results underscore the need to consider multiple phases of the reproductive cycle when assessing the effects of environmental variability on Arctic-breeding birds.

Alaska↗
USGS2017

A synthesis of thresholds for focal species along the U.S. Atlantic and Gulf Coasts: A review of research and applications

The impacts from climate change are increasing the possibility of vulnerable coastal species and habitats crossing critical thresholds that could spur rapid and possibly irreversible changes. For species of high conservation concern, improved knowledge of quantitative thresholds could greatly improve management. To meet this need, we synthesized information pertaining to biological responses as tipping points to sea level rise (SLR) and coastal storms for 45 fish, wildlife, and plant species along the U.S. Atlantic and Gulf Coasts and Caribbean through a literature review and expert elicitation. Although these species were selected based on their ecological, economic, and cultural importance, just over half (56%, n = 25) have quantitative threshold data currently available that can be used to assess the effects of SLR and storms during some aspect of their life history. Birds, reptiles, and plants represent the best studied coastal species. Thirteen of the species (29%) are projected to lose at least 50% of their population or habitat (e.g., foraging, nesting, spawning, or resting habitat) in some areas with a 0.5 m or greater rise in sea levels by 2100. Two species (a bird and reptile) may gain habitat from projected SLR and be resilient to future impacts. Numeric thresholds were not available for the remaining 20 species we searched for. Coastal fishes, mammals, and amphibians were among the groups representing a major information gap in this field of research. In addition, quantitative threshold responses to coastal storms were scarce for all taxa. While vulnerability assessments and qualitative research related to the impacts of SLR and storms on coastal species and habitats are increasing, work that incorporates quantitative thresholds as response and impact metrics remains limited. Additional monitoring, modeling, and research that provides multiple quantitative thresholds across species' life stages and/or latitudinal gradients is ideal to support robust coastal management and decision-making across spatio-temporal scales in the face of climate change.

Ocean and Coastal Management↗
USGS2014

Strategic conservation planning for the Eastern North Carolina/Southeastern Virginia Strategic Habitat Conservation Team

The Eastern North Carolina/Southeastern Virginia Strategic Habitat Conservation Team (ENCSEVA) is a partnership among local federal agencies and programs with a mission to apply Strategic Habitat Conservation to accomplish priority landscape-level conservation within its geographic region. ENCSEVA seeks to further landscape-scale conservation through collaboration with local partners. To accomplish this mission, ENCSEVA is developing a comprehensive Strategic Habitat Conservation Plan (Plan) to provide guidance for its members, partners, and collaborators by establishing mutual conservation goals, objectives, strategies, and metrics to gauge the success of conservation efforts. Identifying common goals allows the ENCSEVA team to develop strategies that leverage joint resources and are more likely to achieve desired impacts across the landscape. The Plan will also provide an approach for ENCSEVA to meet applied research needs (identify knowledge gaps), foster adaptive management principles, identify conservation priorities, prioritize threats (including potential impacts of climate change), and identify the required capacity to implement strategies to create more resilient landscapes. ENCSEVA seeks to support the overarching goals of the South Atlantic Landscape Conservation Cooperative (SALCC) and to provide scientific and technical support for conservation at landscape scales as well as inform the management of natural resources in response to shifts in climate, habitat fragmentation and loss, and other landscape-level challenges (South Atlantic LCC 2012). The ENCSEVA ecoregion encompasses the northern third of the SALCC geography and offers a unique opportunity to apply landscape conservation at multiple scales through the guidance of local conservation and natural resource management efforts and by reporting metrics that reflect the effectiveness of those efforts (Figure 1). The Environmental Decision Analysis Team, housed within the North Carolina Cooperative Fish and Wildlife Research Unit at North Carolina State University, is assisting the ENCSEVA team in developing a scientifically sound basis for the Plan though the elicitation of expert knowledge and the organization of that knowledge using the Open Standards for the Practice of Conservation. The Open Standards for the Practice of Conservation is a framework that is well suited to incorporating decision-making tools such as Structured Decision Making and provides a multi-step process to conceptually organize conservation projects in a manner that enhances the rigor and transparency of expert and knowledge-based plans. It helps define explicit pathways from 2 planned conservation activities and ultimate impact, as well as indicators to measure success (Stem et al. 2005). Specifically, the framework identifies conservation targets, key ecological attributes, threats, and associated indicators to monitor responses given the implementation of a conservation action (Conservation Measures Partnership 2007). This report serves to provide a scientific foundation for the Plan by summarizing the expert opinion of wildlife biologists, ecologists, hydrologists, researchers, natural resource managers, and conservation practitioners regarding five environments (wetlands, riverine systems, estuaries, uplands, and barrier islands) within the ENCSEVA geography. Specifically, this report describes (1) the approach to elicit expert knowledge meant to support the strategic plan, (2) how this knowledge can inform collaborative conservation planning, and (3) a summary of opportunities available for the ENCSEVA team to address threats and impacts associated with climate change within the ecoregion.

Technical Bulletin↗
USGS2024

Climate-smart invasive species management for 21st century global change challenges

Addressing the global challenges of climate change and biotic invasions requires understanding their interactions and implications for natural resource management. To facilitate and support invasive species management in a changing climate, we review how climate change and invasions interact to impact the planning, action, and outcomes of invasive species management. Climate change is affecting which species natural resource managers need to assess, monitor, and target by facilitating the introduction of new potential invasive species and altering pathways of introduction and spread. Climate-driven shifts in seasonal conditions and phenological events disrupt and require more flexible management timelines. Climate change may reduce the efficacy and feasibility of current treatment methods and create a need to shift management goals as native ecosystems become more vulnerable to disturbance. Additionally, extreme climate events can compound the spread and impacts of biological invasions, making invasive species management a necessary part of extreme event preparation and response planning. As a solution to these challenges, we propose climate-smart invasive species management, which we define as the approaches that managers and decision-makers can take to address the interactive effects of climate change and invasions. Climate-smart invasive species management includes considering shifts in species ranges, abundance, and impacts to inform monitoring, treatment, and regulation of potential and new invaders at multiple scales. Managers can also adjust the timing of and approach to treatment as efficacy and feasibility change, promote resilient ecosystems through climate-smart restoration, and consider the effects of climate change when setting management goals. Furthermore, climate adaptation funds could expand avenues of funding and support for invasive species management. Explicitly considering the interactions of climate change and biological invasions within organizational decision-making and policy will lead to more effective management and can promote more resilient landscapes.

Global Change Biology↗
USGS2021

Grand challenges of hydrologic modeling for food-energy-water nexus security in high mountain Asia

Climate-influenced changes in hydrology affect water-food-energy security that may impact up to two billion people downstream of the High Mountain Asia (HMA) region. Changes in water supply affect energy, industry, transportation, and ecosystems (agriculture, fisheries) and as a result, also affect the region's social, environmental, and economic fabrics. Sustaining the highly interconnected food-energy-water nexus (FEWN) will be a fundamental and increasing challenge under a changing climate regime. High variability in topography and distribution of glaciated and snow-covered areas in the HMA region, and scarcity of high resolution ( in-situ ) data make it difficult to model and project climate change impacts on individual watersheds. We lack basic understanding of the spatial and temporal variations in climate, surface impurities in snow and ice such as black carbon and dust that alter surface albedo, and glacier mass balance and dynamics. These knowledge gaps create challenges in predicting where and when the impact of changes in river flow will be the most significant economically and ecologically. In response to these challenges, the United States National Aeronautics and Space Administration (NASA) established the High Mountain Asia Team (HiMAT) in 2016 to conduct research to address knowledge gaps. This paper summarizes some of the advances HiMAT made over the past 5 years, highlights the scientific challenges in improving our understanding of the hydrology of the HMA region, and introduces an integrated assessment framework to assess the impacts of climate changes on the FEWN for the HMA region. The framework, developed under a NASA HMA project, links climate models, hydrology, hydropower, fish biology, and economic analysis. The framework could be applied to develop scientific understanding of spatio-temporal variability in water availability and the resultant downstream impacts on the FEWN to support water resource management under a changing climate regime.

Frontiers in Water↗
USGS2018

Beyond clay: Towards an improved set of variables for predicting soil organic matter content

Improved quantification of the factors controlling soil organic matter (SOM) stabilization at continental to global scales is needed to inform projections of the largest actively cycling terrestrial carbon pool on Earth, and its response to environmental change. Biogeochemical models rely almost exclusively on clay content to modify rates of SOM turnover and fluxes of climate-active CO 2 to the atmosphere. Emerging conceptual understanding, however, suggests other soil physicochemical properties may predict SOM stabilization better than clay content. We addressed this discrepancy by synthesizing data from over 5,500 soil profiles spanning continental scale environmental gradients. Here, we demonstrate that other physicochemical parameters are much stronger predictors of SOM content, with clay content having relatively little explanatory power. We show that exchangeable calcium strongly predicted SOM content in water-limited, alkaline soils, whereas with increasing moisture availability and acidity, iron- and aluminum-oxyhydroxides emerged as better predictors, demonstrating that the relative importance of SOM stabilization mechanisms scales with climate and acidity. These results highlight the urgent need to modify biogeochemical models to better reflect the role of soil physicochemical properties in SOM cycling.

Biogeochemistry↗
USGS2015

Population dynamics of the Cui-ui of Pyramid Lake, Nevada: A Potamodromous catostomid subject to failed reproduction

Fishes of the Truckee River basin (California and Nevada) evolved in an aquatic system that has been episodically diminished by extended drought. For potamodromous species, such as the endangered Cui-ui endemic to Pyramid Lake, Nevada, prehistoric episodic severe drought presumably led to periods of failed reproduction due to restricted access to spawning habitat. The response of the Cui-ui population to more recent failed reproduction caused by anthropogenic activity was studied to learn how to manage this species through periods of spawning disruption. Adult Cui-ui survival averaged 91% and 89% for females and males, respectively, in drought years when spawning migrations were either precluded or few fish migrated because of no or low stream flow. In each of 2 years when stream access was precluded, the adult survival was nearly 100% suggesting that Cui-ui survival is extended in the absence of a spawning migration. Survival averaged 62% and 60% for females and males, respectively, in years of spawning migrations. Strong predominant year-classes developed in the year immediately following a period of failed reproduction, indicating the species’ capacity for population rebound. Year-class predominance persisted for 6–10 years and through years of low survival associated with migration years, and this predominance is probably due, in part, to a diverse age at maturity. Contemporary water diversions from the Truckee River provided the opportunity to study the response of the Cui-ui population to years of failed reproduction. A projected drier Truckee River basin associated with global climate change will test the Cui-ui’s adaptive capacity to endure periods of reproductive failure. This study is aimed at assisting Cui-ui managers in conserving the species in this highly regulated and changing system. The study also adds insight into the prehistoric population dynamics of a potamodromous species in the arid western United States subject to wide fluctuations in annual precipitation and water availability.

California, Nevada↗
USGS2010

Emerging themes in the ecology and management of North American forests

The 7th North American Forest Ecology Workshop, consisting of 149 presentations in 16 oral sessions and a poster session, reflected a broad range of topical areas currently under investigation in forest ecology and management. There was an overarching emphasis on the role of disturbance, both natural and anthropogenic, in the dynamics of forest ecosystems, and the recognition that legacies from past disturbances strongly influence future trajectories. Climate was invoked as a major driver of ecosystem change. An emphasis was placed on application of research findings for predicting system responses to changing forest management initiatives. Several “needs” emerged from the discussions regarding approaches to the study of forest ecosystems, including (1) consideration of variable spatial and temporal scales, (2) long-term monitoring, (3) development of universal databases more encompassing of time and space to facilitate meta-analyses, (4) combining field studies and modeling approaches, (5) standardizing methods of measurement and assessment, (6) guarding against oversimplification or overgeneralization from limited site-specific results, (7) greater emphasis on plant-animal interactions, and (8) better alignment of needs and communication of results between researchers and managers.

International Journal of Forestry Research↗