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Ecosystems 

Latest Results for Ecosystems
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Shrubs and Degraded Permafrost Pave the Way for Tree Establishment in Subarctic Peatlands
30. Juni 2020
Abstract Arctic and subarctic ecosystems are changing rapidly in species composition and functioning as they warm twice as fast as the global average. It has been suggested that tree-less boreal landscapes may shift abruptly to tree-dominated states as climate warms. Yet, we insufficiently understand the conditions and mechanisms underlying tree establishment in the subarctic and arctic regions to anticipate how climate change may further affect ecosystem structure and functioning. We conducted a field experiment to assess the role of permafrost presence, micro-topography...
Effects of Grazing, Wind Erosion, and Dust Deposition on Plant Community Composition and Structure in a Temperate Steppe
30. Juni 2020
Abstract Grazing can affect plant community composition and structure directly by foraging and indirectly by increasing wind erosion and dust storms and subsequently influence ecosystem functioning and ecological services. However, the combined effects of grazing, wind erosion, and dust deposition have not been explored. As part of a 7-year (2010–2016) field manipulative experiment, this study was conducted to examine the impacts of grazing and simulated aeolian processes (wind erosion and dust deposition) on plant community cover and species richness in a temperate...
Large Infaunal Bivalves Determine Community Uptake of Macroalgal Detritus and Food Web Pathways
30. Juni 2020
Abstract Human activities alter biodiversity, influencing bottom-up and top-down control on food webs which can affect ecosystem functioning. In marine ecosystems, large bivalves play a critical role in benthic–pelagic coupling including nutrient cycling; however, their influence on the uptake of detrital organic matter by benthic communities is less understood. In a replicated factorial field experiment, we examined how the presence or absence (overharvesting scenario) of a large suspension-feeding clam on an intertidal sandflat and the addition of isotopically...
Drivers of N 2 O Emissions from Natural Forests and Grasslands Differ in Space and Time
30. Juni 2020
Abstract Understanding the drivers of greenhouse gas (GHG) emissions is one of the most critical global environmental challenges to mitigate the increasing global temperature. Nitrous oxide (N2O) emissions are highly variable in space and time and are controlled by multiple proximal drivers, that is, those that affect N2O emissions directly and in short timescales, and distal or indirect drivers that influence emissions over long timescales. Here we present a quantification of N2O emissions in grasslands and forests throughout the Pampas and the Semiarid Chaco in...
Nonadditive and Legacy Effects of Spring and Autumn Warming on Soil Respiration in an Old-Field Grassland
30. Juni 2020
Abstract Asymmetrically seasonal warming has been widely observed on the Earth, but great uncertainties remain for its effects on terrestrial carbon (C) cycling. As a part of a 7-year seasonal warming experiment in an old-field grassland in Central China, this study demonstrated that spring and autumn warming reduced soil respiration by 8.3% and 9.8%, respectively. In addition, spring warming decreased soil respiration by 1.0% and 15.9% without and with autumn warming, respectively. Autumn warming suppressed soil respiration by 2.5% and 17.2% without and with spring...
Soil Carbon Stocks Vary Across Geomorphic Settings in Australian Temperate Tidal Marsh Ecosystems
24. Juni 2020
Abstract Tidal marshes rank among the ecosystems with the highest capacity to sequester and store organic carbon (Corg) on earth. To inform conservation of coastal vegetated ecosystems for climate change mitigation, this study investigated the factors driving variability in carbon storage. We estimated soil Corg stocks in tidal marshes across temperate Western Australia and assessed differences among geomorphic settings (marine and fluvial deltas, and mid-estuary) and vegetation type (Sarcocornia quinqueflora and Juncus kraussii) linked to soil biogeochemistry. Soil Corg...
Variation in Vegetation and Ecosystem Carbon Stock Due to the Conversion of Disturbed Forest to Oil Palm Plantation in Peruvian Amazonia
17. Juni 2020
Abstract Peruvian national and regional plans promoting oil palm have prompted a rapid expansion of the crop in the Amazonian region. This expansion has taken place primarily at the expense of forest, both undisturbed and disturbed. Assessments of carbon emissions from forest-to-oil palm conversion have essentially been confined to Southeast Asia, and research on Peruvian Amazonian forests has mainly targeted undisturbed sites. This study characterizes the vegetation structure and composition of disturbed forests and smallholder oil palm plantations and evaluates the...
Tropical Biogeomorphic Seagrass Landscapes for Coastal Protection: Persistence and Wave Attenuation During Major Storms Events
15. Juni 2020
Abstract The intensity of major storm events generated within the Atlantic Basin is projected to rise with the warming of the oceans, which is likely to exacerbate coastal erosion. Nature-based flood defence has been proposed as a sustainable and effective solution to protect coastlines. However, the ability of natural ecosystems to withstand major storms like tropical hurricanes has yet to be thoroughly tested. Seagrass meadows both stabilise sediment and attenuate waves, providing effective coastal protection services for sandy beaches. To examine the tolerance of...
Alternative Biogeochemical States of River Pools Mediated by Hippo Use and Flow Variability
08. Juni 2020
Abstract Hippopotami (hippos) are ecosystem engineers that subsidize aquatic ecosystems through the transfer of organic matter and nutrients from their terrestrial grazing, with potentially profound effects on aquatic biogeochemistry. We examined the influence of hippo subsidies on biogeochemical cycling in pools of varying hydrology and intensity of hippo use in the Mara River of Kenya. We sampled upstream, downstream, and at the surface and bottom of pools of varying volume, discharge, and hippo numbers, both before and after flushing flows. The product of hippo number...
Source Switching Maintains Dissolved Organic Matter Chemostasis Across Discharge Levels in a Large Temperate River Network
04. Juni 2020
Abstract Dissolved organic matter (DOM) helps regulate aquatic ecosystem structure and function. In small streams, DOM concentrations are controlled by transport of terrestrial materials to waterways, and are thus highly variable. As rivers become larger, the River Continuum Concept hypothesizes that internal primary production is an increasingly important DOM source, but direct evidence is limited. Recently, the Pulse-Shunt Concept postulated that terrestrial DOM concentrations in larger rivers increase with flow and temperature, which seemingly contradicts previously...
Key Ecological Function Peaks at the Land–Ocean Transition Zone When Vertebrate Scavengers Concentrate on Ocean Beaches
01. Juni 2020
Abstract Ecotones can form hot spots of biodiversity by containing species from multiple ecosystems. Because biodiversity is often linked to ecological function, we posit that rates of key ecological functions are highest at ecotones and decline away from them. Here we test this hypothesis by measuring spatial decays in the function of carrion scavenging on a gradient ranging from ocean beaches upland into abutting coastal dunes. A large field experiment in Eastern Australia, at the ecotone formed by ocean beaches, employed multiple carrion placements and...
Bottom-Up Forces Drive Increases in the Abundance of Large Daphnids in Four Small Lakes Stocked with Rainbow Trout ( Oncorhynchus mykiss ), Interior British Columbia, Canada
01. Juni 2020
Abstract The introduction of salmonids into lakes of western North America for sport fishing is a widespread phenomenon. While numerous investigations have documented cascading trophic interactions upon the introduction of fish into naturally fishless systems, little research has been done to investigate the importance of natural fish status (fishless vs. fish bearing) in modulating historical food web response to dual forcing by bottom-up (resource regulation from nutrients) and top-down (planktivory from stocked fish) processes. We used the paleolimnological record to...
Effects of Nitrogen Deposition on the Abundance and Metabolism of Lichens: A Meta-analysis
01. Juni 2020
Abstract Lichens are the key to nutrient cycling and trophic networks in many terrestrial ecosystems and are good bioindicators of air pollution, including nitrogen (N) deposition. Experimental studies have shown that N deposition can reduce the abundance of lichens and alter their thallus chemistry and metabolism, but we currently lack information about how widespread this effect is and what are the environmental factors modulating the response of lichens to N. We carried out a meta-analysis of the literature about the effects of experimental N fertilization on lichen...
Mechanisms for the Development of Microform Patterns in Peatlands of the Hudson Bay Lowland
01. Juni 2020
Abstract Spatial surface patterns of hummocks, hollows, ridges, and pools (microtopography) are common features of many northern peatlands and are particularly distinct within the vast peatlands of the Hudson Bay Lowland (HBL), Canada. Hypotheses and models describe how small-scale feedbacks among vegetation, hydrology, and nutrients cause spatial differences in peat accumulation that enable microforms and surface patterns to develop over time. Empirical tests of the predictions from theoretical models of these proposed feedback mechanisms are limited, particularly in...
Varying Vegetation Composition, Respiration and Photosynthesis Decrease Temporal Variability of the CO 2 Sink in a Boreal Bog
01. Juni 2020
Abstract We quantified the role of spatially varying vegetation composition in seasonal and interannual changes in a boreal bog’s CO2 uptake. We divided the spatially heterogeneous site into six microform classes based on plant species composition and measured their net ecosystem exchange (NEE) using chamber method over the growing seasons in 2012–2014. A nonlinear mixed-effects model was applied to assess how the contributions of microforms with different vegetation change temporally, and to upscale NEE to the ecosystem level to be compared with eddy covariance (EC...
Fungi in the Canopy: How Soil Fungi and Extracellular Enzymes Differ Between Canopy and Ground Soils
01. Juni 2020
Abstract Tropical montane cloud forests contain a large abundance and diversity of canopy epiphytes, which depend on canopy soil to retain water and nutrients. We lack an in depth understanding of how these soils contribute to ecosystem processes and soil diversity and how sensitive they may be to projected climate change. We compared canopy and ground soils in Monteverde, Costa Rica, to determine how these two soil types differ in their extracellular enzyme activity (EEA) and fungal communities. Samples were also collected along two elevation gradients to reveal if...
Nitrogen Enrichment Accelerates Mangrove Range Expansion in the Temperate–Tropical Ecotone
01. Juni 2020
Abstract Climate change and nutrient enrichment are two phenomena impacting coastal ecosystems. In coastal wetlands, mangroves in temperate–tropical ecotones are encroaching on adjacent saltmarshes, a pattern that is primarily attributed to warmer winter temperatures. Climate change is also expected to increase the vulnerability of coastal wetlands to eutrophication, and increases in nutrient availability may further mediate the rate of mangrove expansion. We investigated the consequences of nutrient enrichment on coastal wetlands in the mangrove–saltmarsh ecotone...
Cumulative Effects of Disturbances on Soil Nutrients: Predominance of Antagonistic Short-Term Responses to the Salvage Logging of Insect-Killed Stands
01. Juni 2020
Abstract Nutrient cycling generally recovers rapidly following disturbance in forest ecosystems. Concerns have been expressed that the resilience of this function may be altered by enhanced disturbance frequency, and especially by the use of salvage logging. A sudden hemlock looper (Lambdina fiscellaria) outbreak in a boreal forest leading to tree mortality in discrete patches allowed us to evaluate the impact of disturbance type (logging vs insect defoliation) as well as the cumulative effects of both disturbances (that is, salvage logging of defoliated sites) on soil...
Alleviation of Plant Stress Precedes Termination of Rich Fen Stages in Peat Profiles of Lowland Mires
01. Juni 2020
Abstract Mesotrophic rich fens, that is, groundwater-fed mires, may be long-lasting, as well as transient ecosystems, displaced in time by poor fens, bogs, forests or eutrophic reeds. We hypothesized that fen stability is controlled by plant stress caused by waterlogging with calcium-rich and nutrient-poor groundwater, which limits expansion of hummock mosses, tussock sedges and trees. We analysed 32 European Holocene macrofossil profiles of rich fens using plant functional traits (PFTs) which indicate the level of plant stress in the environment: canopy height, clonal...
Interactions Between Physical Template and Self-organization Shape Plant Dynamics in a Stream Ecosystem
01. Juni 2020
Abstract Both internal feedbacks and preexisting heterogeneity of a physical template can produce biological patchiness in ecosystems. The relative importance of the two drivers might change over time, in response to changes in the external environment. This is especially relevant for ecosystems experiencing high environmental variability. We investigated the interaction between these two drivers—internal feedbacks and template heterogeneity (represented by variation in water permanence in this study)—using 9-year data on macrophyte (wetland) patch distribution...