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At least 721 records · Page 40Linked to original sources

USGS2012

N 2 -fixing red alder indirectly accelerates ecosystem nitrogen cycling

Symbiotic N 2 -fixing tree species can accelerate ecosystem N dynamics through decomposition via direct pathways by producing readily decomposed leaf litter and increasing N supply to decomposers, as well as via indirect pathways by increasing tissue and detrital N in non-fixing vegetation. To evaluate the relative importance of these pathways, we compared three-year decomposition and N dynamics of N 2 -fixing red alder leaf litter (2.34 %N) to both low-N (0.68 %N) and high-N (1.21 %N) litter of non-fixing Douglas-fir, and decomposed each litter source in four forests dominated by either red alder or Douglas-fir. We also used experimental N fertilization of decomposition plots to assess elevated N availability as a potential mechanism of N 2 -fixer effects on litter mass loss and N dynamics. Direct effects of N 2 -fixing red alder on decomposition occurred primarily as faster N release from red alder than Douglas-fir litter, but direct increases in N supply to decomposers via fertilization did not stimulate decomposition of any litter. Fixed N indirectly influenced detrital dynamics by increasing Douglas-fir tissue and litter N concentrations, which accelerated litter N release without accelerating mass loss. By increasing soil N, tissue N, and the rate of N release from litter of non-fixers, we conclude that N 2 -fixing vegetation can indirectly foster plant-soil feedbacks that contribute to the persistence of elevated N availability in terrestrial ecosystems.

Ecosystems↗

USGS2017

Evaluating stocking efficacy in an ecosystem undergoing oligotrophication

Oligotrophication has negatively affected fisheries production in many freshwater ecosystems and could conceivably reduce the efficacy of stockings used to enhance fisheries. In Lake Michigan, offshore oligotrophication has occurred since the 1970s, owing to reductions in total phosphorus (TP) inputs and nearshore sequestration of TP by nonindigenous dreissenid mussels. We evaluated simultaneous effects of stock enhancement and oligotrophication on salmonine species (Chinook salmon Oncorhynchus tshawytscha , lake trout Salvelinus namaycush , and steelhead O. mykiss ) that support valuable recreational fisheries. We employed a novel application of an Ecopath with Ecosim model by conducting a full factorial simulation experiment. Our design included multiple levels of salmonine stocking, consumption by invasive quagga mussels ( Dreissena bugensis ), and TP that were informed by manager interests. Under all levels of TP and quagga mussel consumption, our results showed that stock enhancement could still increase salmonine biomass, but positive responses were stronger for lake trout and steelhead than Chinook salmon. Simulations showed that quagga mussel consumption has deleterious effects on pelagic-oriented prey fishes and Chinook salmon, which feed almost exclusively on the pelagic-oriented alewife ( Alosa pseudoharengus ). In summary, results from our simulation experiment suggested that lake trout and steelhead are better suited to the current ecosystem than Chinook salmon, and therefore, stock enhancement provides the highest gains for these two species. Furthermore, simulated biomass of all recreational salmonine species increased with increasing TP, indicating the need for managers to consider how potential future oligotrophication will limit the carrying capacity of salmonine biomass in Lake Michigan

Lake Michigan↗

USGS2017

Historical cover trends in a sagebrush steppe ecosystem from 1985 to 2013: Links with climate, disturbance, and management

Understanding the causes and consequences of component change in sagebrush steppe is crucial for evaluating ecosystem sustainability. The sagebrush ( Artemisia spp.) steppe ecosystem of the northwest USA has been impacted by the invasion of exotic grasses, increasing fire return intervals, changing land management practices, and fragmentation, often lowering the overall resilience to change. We utilized contemporary and historical Landsat imagery, field data, and regression tree models to produce fractional cover maps of rangeland components (shrub, sagebrush, herbaceous, bare ground, and litter) through the last 30 years. Our main goals were to (1) investigate rangeland component trends over 30 years, (2) evaluate the magnitude and direction of trends in components and climate drivers and their relationship, and (3) assess component trends influenced by climate. Results indicated that over the study period, shrub, sage, herbaceous, and litter cover decreased, while bare ground cover increased. Measured rates of change ranged from − 0.14% decade −1 for shrub cover to 0.05% decade −1 for bare ground, whereas herbaceous and litter cover trends were negligible. Net landscape cover changes were consistent with expectations of climate change and disturbance producing a loss of biotic cover, and converting a portion of shrub and sagebrush to herbaceous cover. Overall, fire and related successional recovery was the greatest change agent for all components in terms of area and cover change, while increasing minimum temperature, at a rate of 0.66°C decade −1 , was found to be the most significant climate driver.

California, Nevada, Oregon↗

USGS2024

Intrinsic and extrinsic regulation of water clarity in a large, floodplain-river ecosystem

Ecosystem processes in rivers are thought to be controlled more by extrinsic than intrinsic factors, that is, the result of processes that occur upstream or within their watersheds. However, large floodplain rivers have a diverse assemblage of aquatic areas spanning gradients of connectivity with the main channel and internal controls may at times regulate long-term dynamics. When and where internal controls are important has not been widely explored in rivers. The Upper Mississippi River System (UMRS) provides a unique opportunity to assess regulation of ecosystem processes in a large floodplain river as water clarity has increased in several reaches over the last two decades. To better understand when and where intrinsic variables (for example , aquatic vegetation and common carp) and extrinsic variables (for example , upstream main channel total suspended solids (TSS) concentration and discharge) regulate water clarity, we describe 24-year trends of TSS in six study reaches of the UMRS. We evaluated the degree to which trends were shared across aquatic areas within each study reach and identified potential drivers of long-term TSS dynamics. Results varied across and within UMRS reaches, but common carp abundance was the strongest predictor in nearly all study reaches. Several models indicated associations with both intrinsic and extrinsic factors, and the marginal model r 2 values (0.26–0.61) suggest that additional environmental factors may have influenced water clarity. Knowledge of the degree to which intrinsic and extrinsic processes regulate water clarity is important for understanding and managing large, floodplain rivers worldwide.

Ecosystems↗

USGS2025

Quantifying benthic flux of Mysis biomass through diel vertical migration at the ecosystem scale

Mysis diluviana is a macroinvertebrate that couples benthic and pelagic habitats on a daily timescale through diel vertical migration (DVM). However, quantifying how much Mysis biomass is exchanged between benthic and pelagic habitats at an ecosystem scale is difficult because of sampling limitations and variability in Mysis DVM behavior related to light and depth. Although Mysis are benthic-pelagic migrators, a portion remains pelagic during the day offshore in Lake Ontario, partially contradicting the assumption of population-level DVM over deep areas. To estimate the amount of biomass transferred from benthic to pelagic habitat via DVM in Lake Ontario, we estimated the portion of pelagic biomass at night originating from benthic habitat as the difference between night and day pelagic estimates from net tows along a bathymetric depth gradient. We then modeled the portion as a function of depth, extrapolated these depth-dependent estimates to an existing lake wide night-pelagic dataset, and summed amounts across depth strata. We estimated more biomass was transferred from benthic to pelagic habitat at intermediate lake depths (100–160 m) despite greater offshore (> 180 m) night-pelagic biomass. Our results suggest ways to improve estimates of Mysis habitat coupling and how to account for important factors such as depth and light for modeling Mysis DVM behavior at the population- and ecosystem-levels.

Lake Ontario↗

USGS2021

The influence of floral resources and microclimate on pollinator visitation in an agro-ecosystem

As agriculture expands to meet the needs of a growing global population, natural ecosystems are threatened by deforestation and habitat fragmentation. Tropical agroforestry systems offer a sustainable alternative to traditional agriculture by providing food for production while also supporting biodiversity and ecosystem services. Previous studies have shown that these systems may even improve crop pollination, but the mechanisms of how these improvements occur are still poorly understood. Using coffee as a focal crop, we explored how microclimatic conditions affected nectar traits (sugar and caffeine concentration) important for pollinator visitation. We also studied how microclimate, floral traits, floral availability at the coffee plant level, availability of floral resources provided by other plant species in the agroecosystem (neighborhood floral availability), and the presence of other bees affected the amount of time bees spent foraging on coffee flowers and the proportion of coffee pollen carried on their bodies. We explored these factors using the two dominant coffee species farmed on Puerto Rico, Coffea canephora and C. arabica , under sun and shade management. We found that high nectar sugar concentration and temperature were important predictors of short floral visits (<15 seconds), while increased number of bees and open coffee flowers were important predictors of longer floral visits (16-180 seconds). High nectar caffeine concentration was an important predictor of longer visits on C. arabica flowers while the opposite was observed for C. canephora flowers. For both species, high coffee floral availability was the main predicting factor for the proportion of coffee pollen on the bees bodies. Surprisingly, neither neighborhood floral availability nor the type of coffee plantation (agroforest/shade or sun) were important predictors of bee visitation. These results suggest non-coffee flowering plants in coffee plantations were neither competitors nor facilitators of coffee plantes for pollinators. Additionally, most of the bees surveyed were carrying 80% pollen from one species ( C. arabica or C. canephora ), likely resulting in little heterospecific pollen deposition between Coffea and non-Coffea flowers. Shade trees in coffee plantations do not detract from pollinator visitation to coffee flowers, suggesting that the provision of multiple ecological and wildlife conservation benefits by shade trees is not in conflict with a growers ability to maximize the benefits of insect pollination on fruit production.

Adjuntas Lares,Las Marias, Maricao, Puerto Rico Ut↗

USGS2018

Quantifying the visual-sensory landscape qualities that contribute to cultural ecosystem services using social media and LiDAR

Landscapes are increasingly recognized for providing valuable cultural ecosystem services with numer- ous non-material benefits by serving as places of rest, relaxation, and inspiration that ultimately improve overall mental health and physical well-being. Maintaining and enhancing these valuable benefits through targeted management and conservation measures requires understanding the spatial and tem- poral determinants of perceived landscape values. Content contributed through mobile technologies and the web are emerging globally, providing a promising data source for localizing and assessing these land- scape benefits. These georeferenced data offer rich in situ qualitative information through photos and comments that capture valued and special locations across large geographic areas. We present a novel method for mapping and modeling landscape values and perceptions that leverages viewshed analysis of georeferenced social media data. Using a high resolution LiDAR (Light Detection and Ranging) derived digital surface model, we are able to evaluate landscape characteristics associated with the visual- sensory qualities of outdoor recreationalists. Our results show the importance of historical monuments and attractions in addition to specific environmental features which are appreciated by the public. Evaluation of photo-image content highlights the opportunity of including temporally and spatially vari- able visual-sensory qualities in cultural ecosystem services (CES) evaluation like the sights, sounds and smells of wildlife and weather phenomena.

North Carolina↗

USGS2018

Machine learning for ecosystem services

Recent developments in machine learning have expanded data-driven modelling (DDM) capabilities, allowing artificial intelligence to infer the behaviour of a system by computing and exploiting correlations between observed variables within it. Machine learning algorithms may enable the use of increasingly available ‘big data’ and assist applying ecosystem service models across scales, analysing and predicting the flows of these services to disaggregated beneficiaries. We use the Weka and ARIES software to produce two examples of DDM: firewood use in South Africa and biodiversity value in Sicily, respectively. Our South African example demonstrates that DDM (64–91% accuracy) can identify the areas where firewood use is within the top quartile with comparable accuracy as conventional modelling techniques (54–77% accuracy). The Sicilian example highlights how DDM can be made more accessible to decision makers, who show both capacity and willingness to engage with uncertainty information. Uncertainty estimates, produced as part of the DDM process, allow decision makers to determine what level of uncertainty is acceptable to them and to use their own expertise for potentially contentious decisions. We conclude that DDM has a clear role to play when modelling ecosystem services, helping produce interdisciplinary models and holistic solutions to complex socio-ecological issues.

Ecosystem Services↗

USGS2022

Analysis of provisioning ecosystem services and perceptions of climate change for indigenous communities in the Western Himalayan Gurez Valley, Pakistan

Climate change is a significant threat to people living in mountainous regions. It is essential to understand how montane communities currently depend especially on the provisioning ecosystem services (ES) and the ways in which climate change will impact these services, so that people can develop relevant adaptation strategies. The ES in the Gurez Valley, in the Western Himalayas of Pakistan, provide a unique opportunity to explore these questions. This understudied area is increasingly exposed not only to climate change but also to the overexploitation of resources. Hence, this study aimed to (a) identify and value provisioning ES in the region; (b) delineate indigenous communities’ reliance on ES based on valuation; and (c) measure the perceptions of indigenous communities of the impact of climate change on the ES in Gurez Valley. Semi-structured interviews and focus group discussions were used to classify the provisioning ES by using the ‘Common International Classification on Ecosystem Services’ (CICES) table and applying the ‘Total Economic Valuation (TEV)’ Framework. Results indicate that the indigenous communities are highly dependent on ES, worth 6730 ± 520 USD/Household (HH)/yr, and perceive climate change as a looming threat to water, crops, and rearing livestock ESS in the Gurez Valley. The total economic value of the provisioning ES is 3.1 times higher than a household’s average income. Medicinal plant collection is a significant source of revenue in the Valley for some households, i.e., worth 766 ± 134.8 USD/HH/yr. The benefits of the sustainable use of ES and of climate change adaptation and mitigation, are culturally, economically, and ecologically substantial for the Western Himalayans.

Gurez Valley, Himalaya↗

USGS2026

The influence of tree canopy cover data choices on urban ecosystem accounting

Because urban landscapes are heterogeneous, the methods and spatial resolution used to depict the land surface greatly influence the representation of urban features. Land cover products such as tree canopy cover (TCC) are particularly sensitive to the methodology and resolution used in their creation. Differences in TCC mapping have implications on the outcomes of ecosystem service (ES) models, including those underlying natural capital accounting. Here, we quantify the sensitivity of physical rainfall interception and local climate regulation ES models for 189 U.S. cities to TCC inputs from four TCC products: a) National Land Cover Database (NLCD), b) Enhanced NLCD TCC, c) aggregated city-specific composite, and d) global tree canopy height dataset. We find both city-level and aggregate differences in TCC estimates, from a 38% decrease to a 3% increase relative to an aggregated high-resolution product. These differences result in up to 3% overestimations and 27% underestimation of rainfall interception and 2–56% underestimation of local climate regulation ES. City size, population, and greenness in addition to climatic variation drove differences between TCC products, and this variation requires users to carefully consider the choice of input data for any planned analysis. Though high-resolution data can offer greater nuance and accuracy, more limited spatiotemporal availability can hinder their usefulness for long-term monitoring applications such as natural capital accounting. The differences found in this study provide valuable insights for making informed decisions on data inputs for use in urban ecosystem research and for contextualizing model outcomes.

Contiguous United States↗

USGS2024

The Ecosystem Approach in the 21st century: Guiding science and management – A synthesis

Maintaining the integrity and health of aquatic ecosystems is critical to sustaining the many valued services that they provide society. Unfortunately, achieving this goal has proven challenging in most of the world's large ecosystems owing to rampant environmental change caused by human-driven stress, including accelerating climate change, pollution of waterways, habitat modification and destruction, and the continued spread of non-native species (He and Silliman, 2019; Jenny et al., 2020; Smith et al., 2015; Steffen et al., 2007). These stressors, which can also include purposeful management actions (e.g. nutrient and fisheries management), are presenting a grave challenge globally to efforts aimed at securing a sustainable future for nature, society, and the economy.

Aquatic Ecosystem Health & Management↗

USGS1997

Potential effects of climate change on freshwater ecosystems of the New England/Mid-Atlantic Region

Numerous freshwater ecosystems, dense concentrations of humans along the eastern seaboard, extensive forests and a history of intensive land use distinguish the New England/Mid-Atlantic Region. Human population densities are forecast to increase in portions of the region at the same time that climate is expected to be changing. Consequently, the effects of humans and climatic change are likely to affect freshwater ecosystems within the region interactively. The general climate, at present, is humid continental, and the region receives abundant precipitation. Climatic projections for a 2 × CO 2 atmosphere, however, suggest warmer and drier conditions for much of this region. Annual temperature increases ranging from 3–5°C are projected, with the greatest increases occurring in autumn or winter. According to a water balance model, the projected increase in temperature will result in greater rates of evaporation and evapotranspiration. This could cause a 21 and 31% reduction in annual stream flow in the southern and northern sections of the region, respectively, with greatest reductions occurring in autumn and winter. The amount and duration of snow cover is also projected to decrease across the region, and summer convective thunderstorms are likely to decrease in frequency but increase in intensity.

Hydrological Processes↗

USGS2016

Climate regulates alpine lake ice cover phenology and aquatic ecosystem structure

High-elevation aquatic ecosystems are highly vulnerable to climate change, yet relatively few records are available to characterize shifts in ecosystem structure or their underlying mechanisms. Using a long-term dataset on seven alpine lakes (3126 to 3620 m) in Colorado, USA, we show that ice-off dates have shifted seven days earlier over the past 33 years and that spring weather conditions – especially snowfall – drive yearly variation in ice-off timing. In the most well-studied lake, earlier ice-off associated with increases in water residence times, thermal stratification, ion concentrations, dissolved nitrogen, pH, and chlorophyll-a. Mechanistically, low spring snowfall and warm temperatures reduce summer stream flow (increasing lake residence times) but enhance melting of glacial and permafrost ice (increasing lake solute inputs). The observed links among hydrological, chemical, and biological responses to climate factors highlight the potential for major shifts in the functioning of alpine lakes due to forecasted climate change.

Colorado↗

USGS2017

Thermal effect of climate change on groundwater-fed ecosystems

Groundwater temperature changes will lag surface temperature changes from a changing climate. Steady state solutions of the heat-transport equations are used to identify key processes that control the long-term thermal response of springs and other groundwater discharge to climate change, in particular changes in (1) groundwater recharge rate and temperature and (2) land-surface temperature transmitted through the vadose zone. Transient solutions are developed to estimate the time required for new thermal signals to arrive at ecosystems. The solution is applied to the volcanic Medicine Lake highlands, California, USA, and associated springs complexes that host groundwater-dependent ecosystems. In this system, upper basin groundwater temperatures are strongly affected only by recharge conditions. However, as the vadose zone thins away from the highlands, changes in the average annual land-surface temperature also influence groundwater temperatures. Transient response to temperature change depends on both the conductive time scale and the rate at which recharge delivers heat. Most of the thermal response of groundwater at high elevations will occur within 20 years of a shift in recharge temperatures, but the large lower elevation springs will respond more slowly, with about half of the conductive response occurring within the first 20 years and about half of the advective response to higher recharge temperatures occurring in approximately 60 years.

California↗

USGS2024

Scale‐dependent population drivers inform avian management in a declining saline lake ecosystem

Shrinking saline lakes provide irreplaceable habitat for waterbird species globally. Disentangling the effects of wetland habitat loss from other drivers of waterbird population dynamics is critical for protecting these species in the face of unprecedented changes to saline lake ecosystems, ideally through decision-making frameworks that identify effective management options and their potential outcomes. Here, we develop a framework to assess the effects of hypothesized population drivers and identify potential future outcomes of plausible management scenarios on a saline lake-reliant waterbird species. We use 36 years of monitoring data to quantify the effects of environmental conditions on the population size of a regionally important breeding colony of American white pelicans ( Pelecanus erythrorhynchos ) at Great Salt Lake, Utah, US, then forecast colony abundance under various management scenarios. We found that low lake levels, which allow terrestrial predators access to the colony, are probable drivers of recent colony declines. Without local management efforts, we predicted colony abundance could likely decline approximately 37.3% by 2040, although recent colony observations suggest population declines may be more extreme than predicted. Results from our population projection scenarios suggested that proactive approaches to preventing predator colony access and reversing saline lake declines are crucial for the persistence of the Great Salt Lake pelican colony. Increasing wetland habitat and preventing predator access to the colony together provided the most effective protection, increasing abundance 145.4% above projections where no management actions are taken, according to our population projection scenarios. Given the importance of water levels to the persistence of island-nesting colonial species, proactive approaches to reversing saline lake declines could likely benefit pelicans as well as other avian species reliant on these unique ecosystems.

Utah↗

USGS2025

Quantifying landscape-level biodiversity change in an island ecosystem: A 50-year assessment of shifts in the Hawaiian avian community

Hawaii has experienced profound declines in native avifauna alongside the introduction of numerous bird species. While site-specific population studies are common, landscape-level analyses of avian population dynamics are rare, particularly in island ecosystems. To address this gap, we used a density surface model to create a spatio-temporal projection of population densities and distributions across the Island of Hawai‘i, spanning nearly five decades (1976–2023). We incorporated environmental covariates of habitat, precipitation, and elevation, to further refine our projections. Our analysis encompassed nine native and six non-native bird species, inhabiting a range of ecological niches. We found five out of nine native species have declined in density and range size while four were stable. For non-native species, two were stable, one was decreasing, and three were increasing in density and range size. Our landscape projections can inform management by suggesting areas critical for habitat preservation and land acquisition for conservation, identifying where range fragmentation is occurring, and pinpointing locations of multi-species declines that are likely driven by a common cause. Our study demonstrates how long-term, landscape-level monitoring and analyses can advance understanding and addressing biodiversity loss, particularly in vulnerable tropical island ecosystems.

Hawaii↗

USGS2017

Macroscale patterns of synchrony identify complex relationships among spatial and temporal ecosystem drivers

Ecology has a rich history of studying ecosystem dynamics across time and space that has been motivated by both practical management needs and the need to develop basic ideas about pattern and process in nature. In situations in which both spatial and temporal observations are available, similarities in temporal behavior among sites (i.e., synchrony) provide a means of understanding underlying processes that create patterns over space and time. We used pattern analysis algorithms and data spanning 22–25 yr from 601 lakes to ask three questions: What are the temporal patterns of lake water clarity at sub‐continental scales? What are the spatial patterns (i.e., geography) of synchrony for lake water clarity? And, what are the drivers of spatial and temporal patterns in lake water clarity? We found that the synchrony of water clarity among lakes is not spatially structured at sub‐continental scales. Our results also provide strong evidence that the drivers related to spatial patterns in water clarity are not related to the temporal patterns of water clarity. This analysis of long‐term patterns of water clarity and possible drivers contributes to understanding of broad‐scale spatial patterns in the geography of synchrony and complex relationships between spatial and temporal patterns across ecosystems.

Ecosphere↗

USGS2019

Pre‐fire vegetation drives post‐fire outcomes in sagebrush ecosystems: Evidence from field and remote sensing data

Understanding the factors that influence vegetation responses to disturbance is important because vegetation is the foundation of food resources, wildlife habitat, and ecosystem properties and processes. We integrated vegetation cover data derived from field plots and remotely sensed Landsat images in two focal areas over a 37‐yr period (1979–2016) to investigate how historical changes to community composition influence contemporary responses of vegetation to fire in sagebrush ecosystems in the Great Basin. Our objectives were (1) to quantify the magnitude and direction of change in the cover of native and exotic plant functional groups in relation to their exposure to fire; (2) to relate plant community changes to their historical composition, exposure to fire, and environmental conditions; and (3) to test for consistency of trends revealed by vegetation cover data derived from field plots and Landsat images. Historical (1979–1981) field data originated from 298 locations, Landsat‐derived data and contemporary (2011–2016) field data originated from 448 locations, and an expanded set of locations were included in some analyses of Landsat‐derived data. We found that areas burned by fire since the 1980s had higher annual herbaceous cover than unburned areas both historically and contemporarily. Models revealed a significant interaction between historical community composition and exposure to fire, which suggests that plots with historically high herbaceous cover were more susceptible to burning. Trends revealed by field and Landsat‐derived cover data were only partially consistent, potentially due in part to methods used to predict cover values from Landsat images, and the time period over which each data set was collected. Our results suggest that burned areas historically occupied by sagebrush‐dominated plant communities may have been invaded by exotic annuals prior to burning, possibly because of prior land uses, and after burning, have now transitioned to a persistent herbaceous‐dominated state. This type of state transition has important consequences for forage quality, wildlife habitat, soil nutrients, and future disturbances, such as drought and wildfire.

Oregon, Nevada↗