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Ecosystems 

Latest Results for Ecosystems
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Land–Ocean Connectivity Through Subsidies of Terrestrially Derived Organic Matter to a Nearshore Marine Consumer
01. Juni 2019
Abstract Land–ocean coupling in the form of riverine inputs of terrestrial matter can constitute an energetic subsidy to food webs in nearshore coastal areas. In regions with distinctly seasonal rainfall patterns, the strength and spatial footprint of any terrestrial signal in receiving marine food webs is predicted to mirror seasonal changes in fluvial forcing. Here, we test this prediction in a subtropical bay by isotopically (δ13C and δ15N) characterizing the main primary producers and reconstructing (using a Bayesian stable isotope mixing model) their...
Effects of Bark Beetle Disturbance on Soil Nutrient Retention and Lake Chemistry in Glacial Catchment
01. Juni 2019
Abstract Forest ecosystems worldwide are subjected to human-induced stressors, including eutrophication and acidification, and to natural disturbances (for example, insect infestation, windstorms, fires). The occurrence of the later is expected to increase due to the ongoing climate change. These multi-stressor forcings modify ecosystem biogeochemistry, including the retention of limiting nutrients, with implications for terrestrial and aquatic biodiversity. Here we present whole ecosystem nutrient (N, Ca, Mg, K) mass balances in the forested catchment of Plešné Lake...
Litter Decomposition in Yellowstone Grasslands: The Roles of Large Herbivores, Litter Quality, and Climate
01. Juni 2019
Abstract Plant litter decomposition is a key process that influences carbon and nutrient cycling in terrestrial ecosystems. Litter decomposition is controlled by a number of factors such as temperature, moisture, litter quality, and the composition of soil microbial communities. Large herbivores can affect litter decomposition by modifying each of these factors. The goal of this study was to examine the contribution of herbivores in determining decomposition rates across an ecosystem with a steep climatic gradient. We examined the effect of migratory grazing ungulates...
Spatial Variability of Organic Carbon, CaCO 3 and Nutrient Burial Rates Spanning a Mangrove Productivity Gradient in the Coastal Everglades
01. Juni 2019
Abstract Mangrove wetlands are some of the most important locations of organic carbon (OC) sequestration and storage in the world on a per area basis. The high stocks of soil OC are driven by generally high burial rates and efficient preservation of organic material over past millennia of relatively slow and consistent sea level rise. Although the global average rate of OC burial in mangrove wetlands is relatively high, the range in the literature varies by up to two orders of magnitude. The objective of this research was to measure burial rates of OC, CaCO3, and...
Disentangling Climate and Disturbance Effects on Regional Vegetation Greening Trends
01. Juni 2019
Abstract Productivity of northern latitude forests is an important driver of the terrestrial carbon cycle and is already responding to climate change. Studies of the satellite-derived Normalized Difference Vegetation Index (NDVI) for northern latitudes indicate recent changes in plant productivity. These detected greening and browning trends are often attributed to a lengthening of the growing season from warming temperatures. Yet, disturbance-recovery dynamics are strong drivers of productivity and can mask direct effects of climate change. Here, we analyze 1-km...
Long-term Nutrient Fertilization Increased Soil Carbon Storage in California Grasslands
01. Juni 2019
Abstract Elevated nutrient deposition often increases primary productivity in terrestrial ecosystems and thus has the potential to increase the flux of carbon (C) into soils. An important step toward greater understanding of nutrient effects on C storage involves assessing effects on different fractions of the soil C pool across a range of soil types. We quantified the combined effects of 8 years of nitrogen (N), phosphorus (P), potassium (K), and micronutrient fertilization on the C storage in bulk soil and in density fractions at four grassland sites in California...
Plant Production Responses to Precipitation Differ Along an Elevation Gradient and Are Enhanced Under Extremes
01. Juni 2019
Abstract The sensitivity of plant production to precipitation underlies the functioning of ecosystems. Studies that relate long-term mean annual precipitation and production across multiple sites (spatial relationship) or examine interannual linkages within a site (temporal relationship) can reveal biophysical controls over ecosystem function but have limited ability to infer responses to extreme changes in precipitation that may become more common under climate change. To overcome limitations of using a single approach, we integrated satellite- and ground-based...
Drainage Ratio as a Strong Predictor of Allochthonous Carbon Budget in Hemiboreal Lakes
01. Juni 2019
Abstract We assessed the allochthonous organic carbon (OC) budgets for thirteen hemiboreal lakes using a simple equilibrium model coupled with a Bayesian framework for estimating parameter distribution and uncertainty. Model inputs consisted of hydrological, bathymetric and chemical data that are easily measurable at the lake and basin scale. Among the model outputs were mean OC loads (5–123 g m−2 y−1), exports (1.10−3–108 g m−2 y−1), mineralization (3–12 g m−2 y−1), and sedimentation (2–6 g m−2 y−1). “Active” lake-catchment...
Broad-Scale Patterns of Soil Carbon (C) Pools and Fluxes Across Semiarid Ecosystems are Linked to Climate and Soil Texture
01. Juni 2019
Abstract Dryland (semiarid and arid) ecosystems are responsible for most of the interannual variation in atmospheric CO2 concentrations and contain a considerable fraction of the globe’s soil carbon (C) stock. Despite their important contribution to the global land C sink, we have a poor mechanistic understanding of the processes that drive C cycling patterns in drylands. In this study in eastern Utah, we examined the natural variation of soil C pools and fluxes along semiorthogonal gradients of climate and soil texture in order to determine the pertinent...
Estimating Ecosystem Metabolism to Entire River Networks
01. Juni 2019
Abstract River ecosystem metabolism (REM) is a promising cost-effective measure of ecosystem functioning, as it integrates many different ecosystem processes and is affected by both rapid (primary productivity) and slow (organic matter decomposition) energy channels of the riverine food web. We estimated REM in 41 river reaches in Deva-Cares catchment (northern Spain) during the summer period. We used oxygen mass-balance techniques in which primary production and ecosystem respiration were calculated from oxygen concentration daily curves. Then, we used recently...
Herbivore Effects on Ecosystem Process Rates in a Low-Productive System
01. Juni 2019
Abstract Mammalian herbivores shape the structure and function of many nutrient-limited or low-productive terrestrial ecosystems through modification of plant communities and plant–soil feedbacks. In the tundra biome, mammalian herbivores may both accelerate and decelerate plant biomass growth, microbial activity and nutrient cycling, that is, ecosystem process rates. Selective foraging and associated declines of palatable species are known to be major drivers of plant–soil feedbacks. However, declines in dominant plants of low palatability often linked with high...
Context-Dependency of Agricultural Legacies in Temperate Forest Soils
01. Juni 2019
Abstract Anthropogenic activities have affected forests for centuries, leading to persistent legacies. Observations of agricultural legacies on forest soil properties have been site specific and contrasting. Sites and regions vary along gradients in intrinsic soil characteristics, phosphorus (P) management and nitrogen (N) deposition which could affect the magnitude of soil property responses to past cultivation. A single investigation along these gradients could reconcile contradictions and elucidate context-dependency in agricultural legacies. We analysed soil from 24...
Burrowing Crabs Weaken Mutualism Between Foundation Species
01. Juni 2019
Abstract Foundation species often interact with each other and co-create habitat upon which other species depend. Whether the presence of these facilitated species feeds back to mediate the growth and resilience of the foundation species themselves, and influence the strength of their interactions, remains poorly understood. In a 16-month field experiment in a southeastern US salt marsh, we tested how the overlapping presence of two foundation species, cordgrass (Spartina alterniflora) and ribbed mussels (Geukensia demissa), influences the abundance of facilitated...
At What Scales and Why Does Forest Structure Vary in Naturally Dynamic Boreal Forests? An Analysis of Forest Landscapes on Two Continents
01. Juni 2019
Abstract Identifying the scales of variation in forest structures and the underlying processes are fundamental for understanding forest dynamics. Here, we studied these scale-dependencies in forest structure in naturally dynamic boreal forests on two continents. We identified the spatial scales at which forest structures varied, and analyzed how the scales of variation and the underlying drivers differed among the regions and at particular scales. We studied three 2 km × 2 km landscapes in northeastern Finland and two in eastern Canada. We estimated canopy cover...
Free-living N 2 Fixation in Three Karst Shrublands, Southwest China
01. Juni 2019
Abstract Free-living N2 fixation is an important pathway of external nitrogen input to natural terrestrial ecosystems. However, few measurements of N2 fixation have been conducted in shrublands. Here, free-living N2 fixation in soil (or soil N2 fixation) and litter (or litter N2 fixation) in three shrublands was measured in a karst catchment, southwest China. The three shrublands were dominated by Pterolobium punctatum Hemsl., Vitex negundo Linn. and Rhus chinensis Mill., respectively. Field measurements were carried out in January and July 2016, respectively, using...
Saltwater Intrusion Modifies Microbial Community Structure and Decreases Denitrification in Tidal Freshwater Marshes
01. Juni 2019
Abstract Environmental changes can alter the interactions between biotic and abiotic ecosystem components in tidal wetlands and therefore impact important ecosystem functions. The objective of this study was to determine how saltwater intrusion affects wetland nutrient biogeochemistry, with a specific focus on the soil microbial communities and physicochemical parameters that control nitrate removal. Our work took place in a tidal freshwater marsh in South Carolina, USA, where a 3.5-year saltwater intrusion experiment increased porewater salinities from freshwater to...
Linking Improvement of Soil Structure to Soil Carbon Storage Following Invasion by a C 4 Plant Spartina alterniflora
01. Juni 2019
Abstract Coastal wetlands are increasingly recognized as important ecosystems for long-term carbon (C) storage. However, how soil aggregation mediates C accumulation and sequestration in these ecosystems remains unclear. Using the 13C isotope tracer from the invasion of a C4 plant, Spartina alterniflora, into the native ecosystem originally covered by C3 plants across Eastern Chinese coastal wetlands, we investigated a potential C stabilization process via soil structural protection. We quantified changes in soil aggregates, soil organic carbon (SOC), soil total...
Applying Climate Change Risk Management Tools to Integrate Streamflow Projections and Social Vulnerability
15. Mai 2019
Abstract Shifts in streamflow, due to future climate and land use change, may pose risks to nearby human communities. Projecting the spatial distribution and impacts of these risks requires consideration of biophysical and socioeconomic factors. Models like the Soil and Water Assessment Tool (SWAT) can project spatial distributions of hydrologic risk due to shifting biophysical factors like climate and land use, but cannot account for socioeconomic factors influencing a community’s capacity to adapt to future streamflow changes. To address this limitation, we used a...
Projecting Forest Dynamics Across Europe: Potentials and Pitfalls of Empirical Mortality Algorithms
15. Mai 2019
Abstract Mortality is a key process of forest ecosystem dynamics and functioning strongly altering biomass stocks and carbon residence times. Dynamic vegetation models (DVMs) used to predict forest dynamics are typically based on simple, largely data-free (‘theoretical’) mortality algorithms (MAs). To improve DVM projections, the use of empirically based MAs has been suggested, but little is known about their impact on DVM behavior. A systematic comparison of eight MAs (seven inventory-based, one ‘theoretical’) for the pan-European tree species Pinus sylvestris L...
Risks of Neglecting Phenology When Assessing Climatic Controls of Primary Production
14. Mai 2019
Abstract We evaluated the effect that integrating annual aboveground net primary production (ANPP) along different 12-month periods has on temporal models of productivity (ANPP as a linear function of annual precipitation). We studied Argentinean Patagonia, which encompasses a variety of climates and biomes. Using MODIS normalized difference vegetation index (NDVI) to estimate green biomass, we assessed the date of maximum annual NDVI for 2000–2016. One quarter of Patagonia (West/South region) exhibited a well-defined seasonality, with maximum NDVI during...