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Ecosystems 

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Rapid Recovery of Gross Production and Respiration in a Mesic Mountain Big Sagebrush Ecosystem Following Prescribed Fire
19. Januar 2018
Abstract The impact of land management actions such as prescribed fire remains a key uncertainty in understanding the spatiotemporal patterns of carbon cycling in the Western USA. We therefore quantified carbon exchange and aboveground carbon stocks following a prescribed fire in a mountain big sagebrush ecosystem located in the northern Great Basin, USA. Specifically, we examined the changes in plant functional type, leaf area index, standing aboveground carbon stocks, net ecosystem production (NEP), gross ecosystem production (GEP), and ecosystem-level respiration (Reco...
Biotic and Abiotic Drivers of Peatland Growth and Microtopography: A Model Demonstration
19. Januar 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 developed...
Effects of Terrestrial Organic Matter on Aquatic Primary Production as Mediated by Pelagic–Benthic Resource Fluxes
17. Januar 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...
Long-Term Grazing Accelerated Litter Decomposition in Northern Temperate Grasslands
17. Januar 2018
Abstract Livestock grazing affects plant community composition, diversity, and carbon (C) and nutrient cycling in grasslands. Grazing leads to plant communities that have higher relative abundance of grazing-tolerant species, which in turn may alter the chemical composition of biomass and subsequent litter decomposition rates. To better understand the effects of long-term grazing and associated vegetation shifts on biogeochemical cycling in northern temperate grasslands of western Canada, we studied litter decomposition over 18 months at 15 locations, stratified across...
Decadal Response of Arctic Freshwaters to Burgeoning Goose Populations
16. Januar 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 area...
Aridity Induces Nonlinear Effects of Human Disturbance on Precipitation-Use Efficiency of Iberian Woodlands
16. Januar 2018
Abstract The effects of ecosystem degradation are pervasive worldwide and increasingly concerning under the present context of global changes in climate and land use. Theoretical studies and empirical evidence increasingly suggest that drylands are particularly prone to develop nonlinear functional changes in response to climate variations and human disturbance. Precipitation-use efficiency (PUE) represents the ratio of vegetation production to precipitation and provides a tool for evaluating human and climate impacts on landscape functionality. Holm oak (Quercus ilex...
Phenological Sensitivity of Early and Late Flowering Species Under Seasonal Warming and Altered Precipitation in a Seminatural Temperate Grassland Ecosystem
16. Januar 2018
Abstract Shifts in flowering phenology of plants are indicators of climate change. The great majority of existing phenological studies refer solely to gradual warming. However, knowledge on how flowering phenology responds to changes in seasonal variation of warming and precipitation regimes is missing. We report the onset of 22 early (flowering before/within May) and 23 late flowering (flowering after May) species in response to manipulated seasonal warming (equal to + 1.2°C; last 100-year summer/winter warming), additional winter rainfall, and modified precipitation...
Drivers of Sediment Accumulation and Nutrient Burial in Coastal Stormwater Detention Ponds, South Carolina, USA
16. Januar 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...
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
04. Januar 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...
Does Nutrient Availability Regulate Seagrass Response to Elevated CO 2 ?
22. Dezember 2017
Abstract Future increases in oceanic carbon dioxide concentrations (CO2(aq)) may provide a benefit to submerged plants by alleviating photosynthetic carbon limitation. However, other environmental factors (for example, nutrient availability) may alter how seagrasses respond to CO2(aq) by regulating the supply of additional resources required to support growth. Thus, questions remain in regard to how other factors influence CO2(aq) effects on submerged vegetation. This study factorially manipulated CO2(aq) and nutrient availability, in situ, within a subtropical seagrass...
Macrocharcoal-Based Chronosequences Reveal Shifting Dominance of Conifer Boreal Forests Under Changing Fire Regime
22. Dezember 2017
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 black...
Phosphorus Availability Determines the Response of Tundra Ecosystem Carbon Stocks to Nitrogen Enrichment
18. Dezember 2017
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 stocks...
Large Plankton Enhance Heterotrophy Under Experimental Warming in a Temperate Coastal Ecosystem
15. Dezember 2017
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 production...
Carbon Storage Declines in Old Boreal Forests Irrespective of Succession Pathway
15. Dezember 2017
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...
Low Levels of Allochthony in Consumers Across Three High-Elevation Lake Types
11. Dezember 2017
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. We...
The Influence of Legacy P on Lake Water Quality in a Midwestern Agricultural Watershed
01. Dezember 2017
Abstract Decades of fertilizer and manure applications have led to a buildup of phosphorus (P) in agricultural soils and sediments, commonly referred to as legacy P. Legacy P can provide a long-term source of P to surface waters where it causes eutrophication. Using a suite of numerical models, we investigated the influence of legacy P on water quality in the Yahara Watershed of southern Wisconsin, USA. The suite included Agro-IBIS, a terrestrial ecosystem model; THMB, a hydrologic and nutrient routing model; and the Yahara Water Quality Model which estimates water...
Influence of Land-Use Intensification on Vegetation C-Stocks in an Alpine Valley from 1865 to 2003
01. Dezember 2017
Abstract The role of ecosystems as carbon (C) sinks or sources is intrinsically related to land-use intensity, which determines the land required for biomass production. Here, we systematically investigate the role of different land-use types including their land-use intensities on vegetation C-stocks (SCact) in the Stubai valley, located in the Austrian central Alps. After a period of high land-use impacts until 1954, indicated by massive C-depletion, land-use shifted to completely new courses. Polarization into high-intensity low-land areas and extensification at...
Land Surface Phenology in the Tropics: The Role of Climate and Topography in a Snow-Free Mountain
01. Dezember 2017
Abstract Leaf phenology represents a major temporal component of ecosystem functioning, and understanding the drivers of seasonal variation in phenology is essential to understand plant responses to climate change. We assessed the patterns and drivers of land surface phenology, a proxy for leafing phenology, for the meridional Espinhaço Range, a South American tropical mountain comprising a mosaic of savannas, dry woodlands, montane vegetation and moist forests. We used a 14-year time series of MODIS/NDVI satellite images, acquired between 2001 and 2015, and extracted...
Reconstruction of Historic Forest Cover Changes Indicates Minor Effects on Carbon Stocks in Swiss Forest Soils
01. Dezember 2017
Abstract Forest cover in Switzerland and other European countries has gradually increased in the past century. Our knowledge of the impacts of forest expansion and development on soil organic carbon (SOC) storage is, however, limited due to uncertainties in land-use history and lack of historical soil samples. We investigated the effect of forest age on current SOC storage in Switzerland. For 857 sites, we analysed SOC stocks and determined the minimal forest age for all presently forested sites using digitized historical maps, classifying all sites into three...
Recent Climate Warming-Related Growth Decline Impairs European Beech in the Center of Its Distribution Range
01. Dezember 2017
Abstract Increasing summer droughts represent a major threat for the vitality and productivity of forests in the temperate zone. European beech, the most important tree species of Central Europe’s natural forest vegetation, is known to suffer from increased drought intensity at its southern distribution limits, but it is not well known how this species is affected in the center of its distribution range in a sub-oceanic climate. We compared tree-ring chronologies and the climate sensitivity of growth (MS) in 11 mature beech stands along a precipitation gradient...

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