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Latest Results for Ecosystems
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Long-Term Responses of Nutrient Budgets to Concurrent Climate-Related Stressors in a Boreal Watershed
20. Juni 2018
Abstract The climate of the circumpolar Boreal forest is changing rapidly, resulting in a growing frequency of wildfires and changing precipitation patterns. These climate-related stressors may influence the cycling of nutrients within, and overall ecosystem condition of, Boreal watersheds. However, long-term perspectives of concurrent climate-related impacts on the cycling of nutrients in watersheds are rare. We present multi-decadal terrestrial and lake mass budgets of nitrogen, phosphorus and carbon within a headwater Boreal Shield watershed that was recovering from an...
Transient Grazing and the Dynamics of an Unanticipated Coral–Algal Phase Shift
20. Juni 2018
Abstract Extreme disturbances often lead to community reorganisations, yet sometimes ecosystems unexpectedly fail to recover. Such surprising outcomes may pinpoint important yet overlooked mechanisms that drive ecosystems into undesirable states. Using long-term field observations, experimental manipulations and mechanistic modelling, we document the drivers of an unexpected phase shift from coral to macroalgal dominance following typhoon disturbance on reefs in Palau (Micronesia). After extensive coral mortality, an ephemeral bloom of a canopy-forming macroalga (Liagora...
Temporal Variability of Primary Production Explains Marine Ecosystem Structure and Function
18. Juni 2018
Abstract Understanding drivers of ecosystem structure and function is a pervasive goal in academic and applied research. We used 24 synthetic ecosystem-level indices derived from trophic models, and independently derived data for Net Primary Productivity, to investigate drivers of ecosystem structure and function for 43 marine ecosystems distributed in all oceans of the world and including coastal, estuaries, mid-ocean islands, open-ocean, coral reef, continental shelf, and upwelling ecosystems. Of these indices, ecosystem Biomass, Primary Production, Respiration, the...
Feeding Aquatic Ecosystems: Whole-Lake Experimental Addition of Angler’s Ground Bait Strongly Affects Omnivorous Fish Despite Low Contribution to Lake Carbon Budget
15. Juni 2018
Abstract It is well documented that aquatic ecosystems may be subsidized by naturally derived terrestrial carbon sources. In contrast, the intentional or unintentional subsidy of animal populations by human-derived feed resources and their ecosystem effects are poorly studied. We added ground baits of the type, amount and temporal duration commonly applied by anglers targeting cyprinid fishes to a small lake, and studied behavior, diet composition and annual growth rate of the lake fish community in response to the bait addition. Based on recordings by a...
Long-Term Effects of Fire on Vegetation Structure and Predicted Fire Behavior in Wyoming Big Sagebrush Ecosystems
08. Juni 2018
Abstract Fire historically occurred across the sagebrush steppe, but little is known about how patterns of post-fire fuel accumulation influence future fire in Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) communities. To quantify change in fuel composition and structure in intact sagebrush ecosystems, we sampled 17 years following prescribed fire in eight approximately 400 ha plots (4 burned, 4 unburned control) at Hart Mountain National Antelope Refuge, OR, USA. Fuels data were used to model potential fire behavior in burn and control plots across...
Ecological Role of an Apex Predator Revealed by a Reintroduction Experiment and Bayesian Statistics
08. Juni 2018
Abstract Recent studies suggest that apex predators play a pivotal role in maintaining healthy, balanced ecosystems. However, a criticism of studies investigating the ecological role of apex predators is that understanding does not come from manipulative experiments. Here, we use a before-after-control-impact-paired design to test predictions generated from trophic cascade theory (TCT) and mesopredator release hypothesis (MRH) by experimentally introducing dingoes into a 37-km2 paddock and measuring the resultant effects on mammal assemblages. To increase precision of...
Notice of Disputed Authorship
06. Juni 2018
Bird Diversity in Urban Ecosystems: The Role of the Biome and Land Use Along Urbanization Gradients
05. Juni 2018
Abstract Urbanization is an expanding process worldwide, causing major threats to biodiversity through both species extinction and biotic homogenization. Most studies focusing on urban ecosystems have been conducted in temperate forests of the Northern hemisphere; the ecological and socioeconomic contexts, however, may influence biodiversity responses to urbanization. We ask whether the biomes (here, the humid subtropical forest and the semiarid shrubland) where human settlements and land uses are developed determine bird diversity along urbanization gradients in...
Impact of the Urbanisation Process in the Availability of Ecosystem Services in a Tropical Ecotone Area
05. Juni 2018
Abstract Urbanisation has been a main cause of land use land cover (LULC) change worldwide, often with irreparable consequences to the provision of ecosystem services. Despite an increase in quantitative assessments of ecosystem service values (ESV) related to LULC changes, data are scarce for ecotones, such as the agreste in northeast Brazil (a transitional area between the Atlantic Forest and the Caatinga biomes). The benefit transfer method was used to quantify changes in ESV between 1989, 2007 and 2014 due to urbanisation in the microwatershed Riacho das Piabas...
The Role of Biological Soil Crusts in Nitrogen Cycling and Soil Stabilization in Kangerlussuaq, West Greenland
04. Juni 2018
Abstract Biological soil crusts (biocrusts) naturally coexist with vascular plants in many dryland ecosystems. Although most studies of dryland biocrusts have been conducted in warm deserts, dryland biocrusts also exist in the Arctic, where they may be an important source of nitrogen (N) and carbon (C) to nutrient-limited environments. In Kangerlussuaq, Greenland, wind-driven soil erosion has created a heterogeneous landscape where biocrusts dominate distinct patches of soil but are absent from the surrounding shrub and graminoid tundra. Prior to this study, little was...
Evaluating Stocking Efficacy in an Ecosystem Undergoing Oligotrophication
01. Juni 2018
Abstract 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...
Aboveground Carbon Storage and Its Links to Stand Structure, Tree Diversity and Floristic Composition in South-Eastern Tanzania
01. Juni 2018
Abstract African savannas and dry forests represent a large, but poorly quantified store of biomass carbon and biodiversity. Improving this information is hindered by a lack of recent forest inventories, which are necessary for calibrating earth observation data and for evaluating the relationship between carbon stocks and tree diversity in the context of forest conservation (for example, REDD+). Here, we present new inventory data from south-eastern Tanzania, comprising more than 15,000 trees at 25 locations located across a gradient of aboveground woody carbon (AGC...
Effects of an Experimental Water-level Drawdown on Methane Emissions from a Eutrophic Reservoir
01. Juni 2018
Abstract Reservoirs are a globally significant source of methane (CH4) to the atmosphere. However, emission rate estimates may be biased low due to inadequate monitoring during brief periods of elevated emission rates (that is, hot moments). Here we investigate CH4 bubbling (that is, ebullition) during periods of falling water levels in a eutrophic reservoir in the Midwestern USA. We hypothesized that periods of water-level decline trigger the release of CH4-rich bubbles from the sediments and that these emissions constitute a substantial fraction of the annual...
Stream Resource Gradients Drive Consumption Rates of Supplemental Prey in the Adjacent Riparian Zone
01. Juni 2018
Abstract Decades of research have revealed the crucial roles of cross-system energy flows (spatial subsidies) in mediating trophic interactions in recipient systems. Food web theory predicts that the responses of subsidized consumers are a key to understanding the net impacts of spatial subsidies on in situ prey/resources of recipient systems. However, less is known about the factors triggering the cascading biotic interactions across coupled ecosystems. Here, we quantify how riverine productivity (donor system) mediates terrestrial food web interactions through spatial...
Productivity and Temperature as Drivers of Seasonal and Spatial Variations of Dissolved Methane in the Southern Bight of the North Sea
01. Juni 2018
Abstract Dissolved CH4 concentrations in the Belgian coastal zone (North Sea) ranged between 670 nmol l−1 nearshore and 4 nmol l−1 offshore. Spatial variations of CH4 were related to sediment organic matter (OM) content and gassy sediments. In nearshore stations with fine sand or muddy sediments, the CH4 seasonal cycle followed water temperature, suggesting methanogenesis control by temperature in these OM-rich sediments. In offshore stations with permeable sediments, the CH4 seasonal cycle showed a yearly peak following the chlorophyll-a spring peak, suggesting...
Soil Base Saturation Combines with Beech Bark Disease to Influence Composition and Structure of Sugar Maple-Beech Forests in an Acid Rain-Impacted Region
01. Juni 2018
Abstract Sugar maple, an abundant and highly valued tree species in eastern North America, has experienced decline from soil calcium (Ca) depletion by acidic deposition, while beech, which often coexists with sugar maple, has been afflicted with beech bark disease (BBD) over the same period. To investigate how variations in soil base saturation combine with effects of BBD in influencing stand composition and structure, measurements of soils, canopy, subcanopy, and seedlings were taken in 21 watersheds in the Adirondack region of NY (USA), where sugar maple and beech...
Experimental Detritus Manipulations Unite Surface and Cave Stream Ecosystems Along a Common Energy Gradient
01. Juni 2018
Abstract Subsidies of detritus from donor habitats are important energy sources for many ecosystems, but understanding their role in structuring recipient food webs requires comparative experimental studies along the full spectrum of detrital fluxes. Here we report results from an experimental addition of maize (Zea mays L.) litter to a detritus-poor cave stream ecosystem, which we then compare with analogous, past experiments using detritus-rich surface stream ecosystems that similarly have detritus-based food webs and extremely low in situ primary production...
Biomass Stock and Productivity of Primeval and Production Beech Forests: Greater Canopy Structural Diversity Promotes Productivity
01. Juni 2018
Abstract Our knowledge of temperate broadleaf forest ecology is based mostly on the study of production forests, which lack the terminal stage of forest development and have a simpler stand structure than old-growth and primeval forests. How primeval and production forests differ in net primary production (NPP) is not well known. In three primeval and three nearby production forests of European beech (Fagus sylvatica) in the Slovakian Carpathians, we measured aboveground biomass stocks (live and dead), aboveground NPP (ANPP) and parameters characterizing canopy...
Overstorey–Understorey Interactions Intensify After Drought-Induced Forest Die-Off: Long-Term Effects for Forest Structure and Composition
01. Juni 2018
Abstract Severe drought events increasingly affect forests worldwide, but little is known about their long-term effects at the ecosystem level. Competition between trees and herbs (‘overstorey–understorey competition’) for soil water can reduce tree growth and regeneration success and may thereby alter forest structure and composition. However, these effects are typically ignored in modelling studies. To test the long-term impact of water competition by the herbaceous understorey on forest dynamics, we incorporated this process in the dynamic forest landscape...
Phosphorus Enhances Uptake of Dissolved Organic Matter in Boreal Streams
01. Juni 2018
Abstract Retention of carbon (C), either by physical mechanisms or microbial uptake, is a key driver of the transformation and storage of C and nutrients within ecosystems. Both the molecular composition and nutrient content of organic matter influence the rate at which it is retained in streams, but the relative influence of these characteristics remains unclear. We estimated the effects of nutrient content and molecular composition of dissolved organic C (DOC) on uptake in boreal streams by measuring rates of C retention, in situ, following introduction of leachates...