Ecosystem

About: Ecosystem is a research topic. Over the lifetime, 25460 publications have been published within this topic receiving 1291375 citations. The topic is also known as: ecological system & Ecosystem.

Measuring the Inertia and Resilience of Ecosystems

Abstract: The resilience of natural ecosystems is a property of keen interest to both theoretical and applied ecologists. Resilience, in this context, refers to the degree, manner, and pace of restoration of initial structure and function in an ecosystem after disturbance. It is an important ecological characteristic, reflecting ultimately the nature and complexity of homeostatic processes in an ecosystem. Discussions of the concept of ecosystem resilience are relatively recent, and a variety of terms has been proposed for properties of resilience. The ability of a natural ecosystem to restore its structure following acute or chronic disturbance (natural or human-induced) is here termed resilience, consistent with the use of Clapham (1971). This same set of properties is subsumed under the term stability by May (1973), Holling (1973), and Orians (1975) and termed elasticity by Cairs and Dickson (1977). Given the definition of resilience above, it would seem useful to limit "stability" to the pattern of fluctuations in a relatively unimpacted ecosystem over time, a usage consistent with the first eight properties of stability discussed by Whittaker (1975a). Traditionally, fluctuations in ecosystem structure have referred to variations in population densities of component species, but in theory other measures of ecosystem structure or function (e.g., biomass, net primary production, nutrient stocks, species richness) could be used. Since different properties of ecosystem structure and function will not necessarily vary at parallel rates, however, the ecosystem parameters chosen for study will have a

Ecosystem changes in the North Pacific subtropical gyre attributed to the 1991–92 El Niño

Abstract: SUBTROPICAL ocean gyres are considered to be the marine analogues of terrestrial deserts because of chronic nutrient depletion and low standing stocks of organisms1. Despite their presumed low rates of primary and export production, oligotrophic habitats contribute significantly to global productivity because of their large extent2. Therefore, even small changes in ecosystem production can produce large effects in the global carbon cycle. The North Pacific subtropical gyre has generally been thought to support a homogeneous, stable biological community3,4, but recent investigations have suggested instead that the ecosystem of this gyre is temporally and spatially variable5–7. The causes of this variability are not well understood. Here we present evidence of a major change in the structure and productivity of the pelagic ecosystem in the subtropical North Pacific Ocean, an effect that we attribute to the 1991–92 El Nine–Southern Oscillation (ENSO) event. Decreased upper-ocean mixing and a change in circulation resulted in an increased abundance and activity of nitrogen-fixing micro-organisms and a shift from a primarily nitrogen-limited to a primarily phosphorus-limited habitat with attendant changes in total and export production and in nutrient cycling pathways and rates.

Fungal Biodiversity and Their Role in Soil Health.

Abstract: Soil health, and the closely related terms of soil quality and fertility, is considered as one of the most important characteristics of soil ecosystems. The integrated approach to soil health assumes that soil is a living system and soil health results from the interaction between different processes and properties, with a strong effect on the activity of soil microbiota. All soils can be described using physical, chemical, and biological properties, but adaptation to environmental changes, driven by the processes of natural selection, are unique to the latter one. This mini review focuses on fungal biodiversity and its role in the health of managed soils as well as on the current methods used in soil mycobiome identification and utilization next generation sequencing (NGS) approaches. The authors separately focus on agriculture and horticulture as well as grassland and forest ecosystems. Moreover, this mini review describes the effect of land-use on the biodiversity and succession of fungi. In conclusion, the authors recommend a shift from cataloging fungal species in different soil ecosystems toward a more global analysis based on functions and interactions between organisms.

Links between plant litter chemistry, species diversity, and below-ground ecosystem function

Abstract: Decomposition is a critical source of plant nutrients, and drives the largest flux of terrestrial C to the atmosphere. Decomposing soil organic matter typically contains litter from multiple plant species, yet we lack a mechanistic understanding of how species diversity influences decomposition processes. Here, we show that soil C and N cycling during decomposition are controlled by the composition and diversity of chemical compounds within plant litter mixtures, rather than by simple metrics of plant species diversity. We amended native soils with litter mixtures containing up to 4 alpine plant species, and we used 9 litter chemical traits to evaluate the chemical composition (i.e., the identity and quantity of compounds) and chemical diversity of the litter mixtures. The chemical composition of the litter mixtures was the strongest predictor of soil respiration, net N mineralization, and microbial biomass N. Soil respiration and net N mineralization rates were also significantly correlated with the chemical diversity of the litter mixtures. In contrast, soil C and N cycling rates were poorly correlated with plant species richness, and there was no relationship between species richness and the chemical diversity of the litter mixtures. These results indicate that the composition and diversity of chemical compounds in litter are potentially important functional traits affecting decomposition, and simple metrics like plant species richness may fail to capture variation in these traits. Litter chemical traits therefore provide a mechanistic link between organisms, species diversity, and key components of below-ground ecosystem function.

The Response of Soil Processes to Climate Change: Results from Manipulation Studies of Shrublands Across an Environmental Gradient

Abstract: Predicted changes in climate may affect key soil processes such as respiration and net nitrogen (N) mineralization and thus key ecosystem functions such as carbon (C) storage and nutrient availability. To identify the sensitivity of shrubland soils to predicted climate changes, we have carried out experimental manipulations involving ecosystem warming and prolonged summer drought in ericaceous shrublands across a European climate gradient. We used retractable covers to create artificial nighttime warming and prolonged summer drought to 20-m2 experimental plots. Combining the data from across the environmental gradient with the results from the manipulation experiments provides evidence for strong climate controls on soil respiration, net N mineralization and nitrification, and litter decomposition. Trends of 0%–19% increases of soil respiration in response to warming and decreases of 3%–29% in response to drought were observed. Across the environmental gradient and below soil temperatures of 20°C at a depth of 5–10 cm, a mean Q10 of 4.1 in respiration rates was observed although this varied from 2.4 to 7.0 between sites. Highest Q10 values were observed in Spain and the UK and were therefore not correlated with soil temperature. A trend of increased accumulated surface litter mass loss was observed with experimental warming (2%– 22%) but there was no consistent response to experimental drought. In contrast to soil respiration and decomposition, variability in net N mineralization was best explained by soil moisture rather than temperature. When water was neither limiting or in excess, a Q10 of 1.5 was observed for net N mineralization rates. These data suggest that key soil processes will be differentially affected by predicted changes in rainfall pattern and temperature and the net effect on ecosystem functioning will be difficult to predict without a greater understanding of the controls underlying the sensitivity of soils to climate variables.