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Ecosystems 

Latest Results for Ecosystems
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Broad-Scale Patterns of Soil Carbon (C) Pools and Fluxes Across Semiarid Ecosystems are Linked to Climate and Soil Texture
20. September 2018
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 environmental...
Effects of Bark Beetle Disturbance on Soil Nutrient Retention and Lake Chemistry in Glacial Catchment
11. September 2018
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...
Long-term Nutrient Fertilization Increased Soil Carbon Storage in California Grasslands
11. September 2018
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
11. September 2018
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 estimates...
At What Scales and Why Does Forest Structure Vary in Naturally Dynamic Boreal Forests? An Analysis of Forest Landscapes on Two Continents
11. September 2018
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 in...
Recovery Debts Can Be Revealed by Ecosystem Network-Based Approaches
10. September 2018
Abstract Ecosystems are increasingly disturbed by natural disturbances and human stressors. Understanding how a disturbance can propagate through an entire ecosystem and how induced changes can last after apparent recovery is key to guide management and ecosystem restoration strategies. Monitoring programs and impact assessment studies rely mostly on indicators based only on species relative abundance and biomass, potentially misinforming management efforts. Impacts on ecosystem structure and functioning, and subsequent delivery of ecosystem services, are too often...
Evidence for the Role of Subterranean Termites ( Reticulitermes spp.) in Temperate Forest Soil Nutrient Cycling
05. September 2018
Abstract Termites are ecosystem engineers in tropical systems, constructing visible biogenic structures (mounds) that influence soil characteristics, decomposition, nutrient cycling, vegetative growth, and biodiversity. Subterranean termites (Reticulitermes spp.) likely influence nutrient cycling within their endemic range in the temperate Holarctic through the translocation of elements from wood to soil by lining their below-ground biogenic structures with frass (feces). We designed a study to ‘follow the frass’ by comparing concentrations of 18 elements (Al, B, Ba...
Quantifying the Uncertainty in Modeled Water Drainage and Nutrient Leaching Fluxes in Forest Ecosystems
04. September 2018
Abstract In terrestrial ecosystem studies, water drainage and nutrient leaching in the soil profile are estimated with hydrological models. Comparing modeled results to empirical data or comparing data from different models is, however, difficult because the uncertainty of input–output budget predictions is often unknown. In this study, we developed a procedure combining a Generalized Likelihood Uncertainty Estimation and a Monte-Carlo modeling approach to estimate uncertainty in model parameter estimates and model outputs water drainage and nutrient leaching fluxes for...
Effects of Terrestrial Organic Matter on Aquatic Primary Production as Mediated by Pelagic–Benthic Resource Fluxes
01. September 2018
Abstract Flows of energy and matter across habitat boundaries can be major determinants of the functioning of recipient ecosystems. It is currently debated whether terrestrial dissolved organic matter (tDOM) is a resource subsidy or a resource subtraction in recipient lakes. We present data from a long-term field experiment in which pelagic phosphorus concentration and whole-ecosystem primary production increased with increasing tDOM input, suggesting that tDOM acted primarily as a direct nutrient subsidy. Piecewise structural equation modeling supports, however, a...
Large Plankton Enhance Heterotrophy Under Experimental Warming in a Temperate Coastal Ecosystem
01. September 2018
Abstract Microbes are key players in oceanic carbon fluxes. Temperate ecosystems are seasonally variable and thus suitable for testing the effect of warming on microbial carbon fluxes at contrasting oceanographic conditions. In four experiments conducted in February, April, August and October 2013 in coastal NE Atlantic waters, we monitored microbial plankton stocks and daily rates of primary production, bacterial heterotrophic production and respiration at in situ temperature and at 2 and 4°C over ambient values during 4-day incubations. Ambient total primary...
Carbon Storage Declines in Old Boreal Forests Irrespective of Succession Pathway
01. September 2018
Abstract The boreal forest plays a critical role in regulating global atmospheric carbon dioxide and is highly influenced by wildfire. However, the long-term recovery of forest carbon (C) storage following wildfire remains unclear, especially during late succession. Uncertainty surrounding C storage in old forests largely stems from both a lack of repeated measurements in forest stands older than the longevity of the pioneer cohort and a lack of consideration of multiple succession pathways. In this study, we constructed a replicated chronosequence, which covered a wide...
Decadal Response of Arctic Freshwaters to Burgeoning Goose Populations
01. September 2018
Abstract The Arctic is faced with rapid climatic changes, but in some areas, drastic changes in the abundance of herbivores represent an even greater agent of change. Increasing goose populations, especially midcontinent lesser snow geese (Chen caerulescens), have led to an extensive loss of vegetation in terrestrial habitats in the Arctic through heavy grazing and destructive foraging. Our aim was to evaluate the effect of geese on the freshwater systems in their Arctic breeding grounds. We sampled the water chemistry of lakes and ponds across a major goose breeding...
Low Levels of Allochthony in Consumers Across Three High-Elevation Lake Types
01. September 2018
Abstract The integration of lakes into watershed-scale energy budgets remains a major goal of aquatic ecosystem ecology. However, this enterprise has focused almost exclusively on temperate and boreal systems and on zooplankton as representatives of system-wide energy flow. We investigated the proportion of consumer biomass derived from terrestrial sources, allochthony, in three classes of high-elevation lakes—alpine, large and small montane—of varying geometry and watershed ecosystem development, and across five taxa, including macrobenthic invertebrates and fish...
Biotic and Abiotic Drivers of Peatland Growth and Microtopography: A Model Demonstration
01. September 2018
Abstract Peatlands are important carbon reserves in terrestrial ecosystems. The microtopography of a peatland area has a strong influence on its carbon balance, determining carbon fluxes at a range of spatial scales. These patterned surfaces are very sensitive to changing climatic conditions. There are open research questions concerning the stability, behaviour and transformation of these microstructures, and the implications of these changes for the long-term accumulation of organic matter in peatlands. A simple two-dimensional peat microtopographical model was...
Biological Nitrogen Fixation Prevents the Response of a Eutrophic Lake to Reduced Loading of Nitrogen: Evidence from a 46-Year Whole-Lake Experiment
01. September 2018
Abstract A whole-ecosystem experiment in Lake 227 (L227) at the Experimental Lakes Area, ongoing since 1969, examined the roles of carbon (C), nitrogen (N), and phosphorus (P) in controlling eutrophication. During 2011, we conducted a series of sub-experiments and more intensive monitoring to improve estimates of N fixation and its ability to meet algal growth demands in the decades following the cessation of artificial N loading, while maintaining long-term high artificial P loading. Stoichiometric nutrient ratios indicated both moderate N and P limitation of the...
Phosphorus Availability Determines the Response of Tundra Ecosystem Carbon Stocks to Nitrogen Enrichment
01. September 2018
Abstract Northern permafrost soils contain important carbon stocks. Here we report the long-term response of carbon stocks in high Arctic dwarf shrub tundra to short-term, low-level nutrient enrichment. Twenty years after experimental nitrogen addition, carbon stocks in vegetation and organic soil had almost halved. In contrast, where phosphorus was added with nitrogen, carbon storage increased by more than 50%. These responses were explained by changes in the depths of the moss and organic soil layers. Nitrogen apparently stimulated decomposition, reducing carbon...
Macrocharcoal-Based Chronosequences Reveal Shifting Dominance of Conifer Boreal Forests Under Changing Fire Regime
01. September 2018
Abstract Balsam fir (Abies balsamea) and black spruce (Picea mariana) forests are the main conifer forest types in the North American boreal zone. The coexistence of the two species as well as their respective canopy dominance in distinct stands raises questions about the long-term evolution from one forest type to the other in relation to environmental factors including climate and stand disturbance. We tested the hypothesis that repetitive fire events promote the succession of balsam fir forest to black spruce forest and vice versa. Postfire chronosequences of one...
Linking Biodiversity, the Environment and Ecosystem Functioning: Ecological Functions of Dung Beetles Along a Tropical Elevational Gradient
01. September 2018
Abstract Biodiversity loss and anthropogenic environmental changes are known to impact ecosystem functions and services. However, there are still some uncertainties such as confounding environmental factors other than community attributes that affect ecosystem functioning. Our goal was to understand what factors influence the performance of Scarabaeinae dung beetle functions, testing the hypothesis that both community attributes and environmental variables influence the performance. Toward this aim, we collected dung beetles along an elevational gradient (800–1400 m...
Know Your Neighbours: Drought Response of Norway Spruce, Silver Fir and Douglas Fir in Mixed Forests Depends on Species Identity and Diversity of Tree Neighbourhoods
01. September 2018
Abstract Norway spruce is a widely cultivated species in Central Europe; however, it is highly susceptible to droughts, which are predicted to become more frequent in the future. A solution to adapt spruce forests to droughts could be the conversion to mixed-species stands containing species which are less sensitive to drought and do not increase the drought stress in spruce. Here we assessed the drought response of spruce and the presumably more drought-tolerant silver fir and Douglas fir in mixed-conifer stands. We measured tree ring widths of 270 target trees, which...
Drivers of Sediment Accumulation and Nutrient Burial in Coastal Stormwater Detention Ponds, South Carolina, USA
01. September 2018
Abstract Stormwater detention ponds are widely utilized as control structures to manage runoff during storm events. These ponds also represent biogeochemical hotspots, where carbon (C) and nutrients can be processed and buried in sediments. This study quantified C and nutrient [nitrogen (N) and phosphorus (P)] sources and burial rates in 14 stormwater detention ponds representative of typical residential development in coastal South Carolina. Bulk sediment accumulation was directly correlated with catchment impervious surface coverage (R2 = 0.90) with sediment...