The Experts below are selected from a list of 110715 Experts worldwide ranked by ideXlab platform
Virginia Massara - One of the best experts on this subject based on the ideXlab platform.
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aridity and overgrazing have convergent effects on Ecosystem Structure and functioning in patagonian rangelands
Land Degradation & Development, 2018Co-Authors: Juan J. Gaitán, Donaldo Bran, Gabriel Oliva, Georgina Ciari, Viviana Nakamatsu, Jorge Salomone, Daniela Ferrante, Gustavo Gabriel Buono, Martin R Aguiar, Virginia MassaraAbstract:Over 65% of drylands are used for grazing of managed livestock. Understanding what drives grazing effects on the Structure and functioning of rangelands is critical for achieving their sustainability. We studied a network of 239 sites across Patagonian rangelands (Argentina), which constitute one of the world's largest rangeland area. We aimed to (i) evaluate how aridity and grazing affect Ecosystem Structure and functioning and (ii) test the usefulness of the landscape function analysis (LFA) indices (stability, infiltration and nutrient cycling) as surrogates of soil functioning. Aridity decreased species richness and the cover of palatable grasses but increased the cover of palatable shrubs. Grazing pressure negatively impacted the cover of palatable grasses and species richness but did not affect the cover of shrubs. Aridity had direct and indirect negative relationships with the LFA indices. Grazing pressure had no direct effects on the LFA indices but had an indirect negative effect on them by affecting vegetation Structure. The LFA indices were positively and negatively correlated with soil organic carbon and sand contents, respectively, suggesting that these indices are useful proxies of soil functional processes in Patagonian rangelands. Our findings indicate that aridity and overgrazing have convergent effects on the Structure and functioning of Ecosystems, as both promoted reductions in species richness, the cover of palatable grasses and soil functioning. Rangeland management activities should aim to enhance species richness and the cover of palatable grasses, as these actions could contribute to offset adverse effects of ongoing increases in aridity on drylands. Copyright © 2017 John Wiley & Sons, Ltd.
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evaluating the performance of multiple remote sensing indices to predict the spatial variability of Ecosystem Structure and functioning in patagonian steppes
Ecological Indicators, 2013Co-Authors: Donaldo Bran, Gabriel Oliva, Georgina Ciari, Viviana Nakamatsu, Jorge Salomone, Daniela Ferrante, Gustavo Gabriel Buono, Virginia Massara, Gervasio HumanoAbstract:Abstract Assessing the spatial variability of Ecosystem Structure and functioning is an important step towards developing monitoring systems to detect changes in Ecosystem attributes that could be linked to desertification processes in drylands. Methods based on ground-collected soil and plant indicators are being increasingly used for this aim, but they have limitations regarding the extent of the area that can be measured using them. Approaches based on remote sensing data can successfully assess large areas, but it is largely unknown how the different indices that can be derived from such data relate to ground-based indicators of Ecosystem health. We tested whether we can predict Ecosystem Structure and functioning, as measured with a field methodology based on indicators of Ecosystem functioning (the landscape function analysis, LFA), over a large area using spectral vegetation indices (VIs), and evaluated which VIs are the best predictors of these Ecosystem attributes. For doing this, we assessed the relationship between vegetation attributes (cover and species richness), LFA indices (stability, infiltration and nutrient cycling) and nine VIs obtained from satellite images of the MODIS sensor in 194 sites located across the Patagonian steppe. We found that NDVI was the VI best predictor of Ecosystem attributes. This VI showed a significant positive linear relationship with both vegetation basal cover ( R 2 = 0.39) and plant species richness ( R 2 = 0.31). NDVI was also significantly and linearly related to the infiltration and nutrient cycling indices ( R 2 = 0.36 and 0.49, respectively), but the relationship with the stability index was weak ( R 2 = 0.13). Our results indicate that VIs obtained from MODIS, and NDVI in particular, are a suitable tool for estimate the spatial variability of functional and structural Ecosystem attributes in the Patagonian steppe at the regional scale.
Heike K. Lotze - One of the best experts on this subject based on the ideXlab platform.
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Twenty-first-century climate change impacts on marine animal biomass and Ecosystem Structure across ocean basins.
Global change biology, 2018Co-Authors: Andrea Bryndum-buchholz, Derek P. Tittensor, Julia L. Blanchard, William W. L. Cheung, Marta Coll, Eric D. Galbraith, Simon Jennings, Olivier Maury, Heike K. LotzeAbstract:Climate change effects on marine Ecosystems include impacts on primary production, ocean temperature, species distributions, and abundance at local to global scales. These changes will significantly alter marine Ecosystem Structure and function with associated socio‐economic impacts on Ecosystem services, marine fisheries, and fishery‐dependent societies. Yet how these changes may play out among ocean basins over the 21st century remains unclear, with most projections coming from single Ecosystem models that do not adequately capture the range of model uncertainty. We address this by using six marine Ecosystem models within the Fisheries and Marine Ecosystem Model Intercomparison Project (Fish‐MIP) to analyze responses of marine animal biomass in all major ocean basins to contrasting climate change scenarios. Under a high emissions scenario (RCP8.5), total marine animal biomass declined by an ensemble mean of 15%–30% (±12%–17%) in the North and South Atlantic and Pacific, and the Indian Ocean by 2100, whereas polar ocean basins experienced a 20%–80% (±35%–200%) increase. Uncertainty and model disagreement were greatest in the Arctic and smallest in the South Pacific Ocean. Projected changes were reduced under a low (RCP2.6) emissions scenario. Under RCP2.6 and RCP8.5, biomass projections were highly correlated with changes in net primary production and negatively correlated with projected sea surface temperature increases across all ocean basins except the polar oceans. Ecosystem Structure was projected to shift as animal biomass concentrated in different size‐classes across ocean basins and emissions scenarios. We highlight that climate change mitigation measures could moderate the impacts on marine animal biomass by reducing biomass declines in the Pacific, Atlantic, and Indian Ocean basins. The range of individual model projections emphasizes the importance of using an ensemble approach in assessing uncertainty of future change.
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Ecosystem Structure and services in eelgrass zostera marina and rockweed ascophyllum nodosum habitats
Marine Ecology Progress Series, 2011Co-Authors: Allison L Schmidt, Marta Coll, Tamara N Romanuk, Heike K. LotzeAbstract:Marine vegetated habitats provide essential functions and services to ocean ecosys- tems and human well-being. It is unclear, however, how different habitat types compare. Using large-scale field surveys, we compared the canopy and community Structure between eelgrass and rockweed beds in Atlantic Canada and assessed their nitrogen retention, carbon storage, and habitat services. We then used binary network models of predator-prey interactions to determine food-web Structure and its robustness to species loss. Despite disparate 3-dimensional canopy Structure, both habitats significantly enhanced overall abundance and diversity of associated flora and fauna, including several commercially important species. Significant differences occurred in the species assemblages within and between habitats and were attributed to different settlement opportunities, food availability, predation risk, and maneuverability. While eelgrass plants had higher nitrogen content, rockweed canopies maintained 8-fold greater biomass and, thus, 14-fold greater nitrogen and 8-fold greater carbon retention per unit area. Both rockweed and eelgrass food webs showed similarities to other temperate and tropical seagrass webs, yet their robustness to the loss of most connected species including primary producers was among the lowest; under- scoring their vulnerability to disturbances affecting the functionally dominant primary producers. The present study demonstrates that marine vegetation provides important habitat, nitrogen, and carbon storage services, yet the extent of these services depends on the foundation species and its architecture. Changes in canopy Structure will therefore have profound effects on associated food webs and Ecosystem services. Thus, as increasing human pressures on coastal Ecosystems threaten the continued supply of essential functions and services, the protection of marine vegetated habitats should be a management priority.
Michael M Douglas - One of the best experts on this subject based on the ideXlab platform.
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the wet dry in the wet dry tropics drives river Ecosystem Structure and processes in northern australia
Freshwater Biology, 2011Co-Authors: Danielle M Warfe, Neil E Pettit, Peter Davies, Bradley James Pusey, Stephen K Hamilton, Mark J Kennard, Simon A Townsend, Peter Bayliss, Douglas Ward, Michael M DouglasAbstract:Summary 1. Northern Australia is characterised by a tropical wet–dry climate that regulates the distinctive character of river flow regimes across the region. There is marked hydrological seasonality, with most flow occurring over only a few months of the year during the wet season. Flow is also characterised by high variability between years, and in the degree of flow cessation, or intermittency, over the dry season. 2. At present, the relatively low human population density and demand for water in the region means that most rivers have largely unmodified flow regimes. These rivers therefore provide a good opportunity to understand the role of natural flow variability in river Ecosystem Structure and processes. 3. This review describes the major flow regime classes characterising northern Australian rivers, from perennial to seasonally intermittent to extremely intermittent, and how these regimes give rise to marked differences in the ecological character of these tropical rivers, particularly their floodplains. 4. We describe the key features of these flow regimes, namely the wet and dry seasons and the transitions between these seasons, and how they regulate the biophysical heterogeneity, primary productivity and movement of biota in Australia’s wet–dry tropical rivers. 5. We develop a conceptual model that predicts the likely hydrological and ecological consequences of future increases in water abstraction (e.g. for agriculture), and suggest how such impacts can be managed so that the distinctive ecological character of these rivers is maintained.
Lirong Song - One of the best experts on this subject based on the ideXlab platform.
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modelling Ecosystem Structure and trophic interactions in a typical cyanobacterial bloom dominated shallow lake dianchi china
Ecological Modelling, 2014Co-Authors: Kun Shan, Lin Li, Xiaoxiao Wang, Yanlong Wu, Lili Hu, Gongliang Yu, Lirong SongAbstract:Lake Dianchi is the largest shallow lake in Yunnan-Guizhou plateau and the sixth largest one in China. The lake has been experiencing cyanobacterial blooms in the last two decades. Although a few studies have investigated the tempo-spatial dynamics of cyanobacterial blooms and their underlying mechanisms, knowledge regarding the food web Structure and trophic interactions in bloom-dominated Ecosystems is scarce. In the present study, an Ecopath model was developed to assess the entire lake Ecosystem on the basis of historical and survey data obtained between 2009 and 2010 at Lake Dianchi. The results showed that the aggregation of flows sensu Lindeman refers to six trophic levels (TLs), and most biomasses and trophic flows were primarily concentrated at the first three levels. About 77.5% of the trophic flows from TLI to TLII originated from detritus, whereas high proportions of under-utilised zooplankton biomass returned to the detritus because of low transfer efficiencies (2.9%) in TLII. The microbial loop was considered to be involved in linking the transfer between detritus and TLII. In addition, low values of connectance index and average mutual information implied that the food web tended to be lost in information diversity and had a less complicated Structure. High cycling flows concentrated in the microbial loop reflected that the Ecosystem enhanced recycling to forms positive feedback by which Ecosystem locked the nutrients and promoted the inflation of biomass in plankton communities. Thus, Dianchi Lake was clearly thought to be a bottom-up control Ecosystem. These characteristics of the food web partly explained why cyanobacterial blooms were exceptionally heavy and durable in this lake. Finally, the implications of artificially stocking filter-feeding fish (bighead and silver fish) and exotic zooplantivorous icefish on the Ecosystem Structure and function are discussed herein. (C) 2014 Published by Elsevier B.V.
Kevin Leleu - One of the best experts on this subject based on the ideXlab platform.
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mapping habitats in a marine reserve showed how a 30 year trophic cascade altered Ecosystem Structure
Biological Conservation, 2012Co-Authors: Kevin Leleu, Brice Remyzephir, Roger Grace, Mark J CostelloAbstract:Abstract Time-series studies have reported trophic cascades in land, freshwater and marine environments in many geographic areas. However, the spatial extent of habitats, a key metric of Ecosystem Structure, has not been mapped in these studies. Marine reserves can provide experimental, before–after and inside–outside (control-impacted), situations for assessing the impact of fishing on Ecosystems. We mapped seabed habitats and their associated communities (biotopes) in New Zealand’s oldest marine reserve for comparison with pre-reserve maps created about 30 years previously. Areas grazed bare by sea urchins were entirely replaced in the centre of the reserve by kelp, or alga turf, an intermediate biotope between heavily grazed encrusting algae and lightly grazed kelp. Urchins declined following increased abundance and body size of spiny (rock) lobsters and fish (especially snapper) in the reserve but maintained bare rock outside. While this gradient in habitat change matched the gradient of predator abundance, it also matched the extent of reef habitat area. Thus the trophic cascade may be influenced by the effect of habitat on the abundance and behavioural interactions of urchins and their predators. Further Ecosystem changes may arise should the abundance of mega-predators, such as seals, cetaceans and large sharks, increase in the region; if parasites become pathogenic; and/or when invasive species reach the reserve. No-take marine reserves provide real-world experiments that show the importance of species in food webs, and the consequences of fishing for Ecosystems. Because these changes in Ecosystem Structure may continue, and will vary with environment, climate and species distributions, reserves need to be permanent and replicated geographically. Habitat maps should be produced for all reserves to enable ecological changes in the Ecosystem to be spatially quantified.
