Changes In Ecosystem Processes Research Articles

Linking pattern and process in cultural landscapes. An empirical study based on spatially explicit indicators

Landscapes can be seen as the contingent and historically variable outcome of an interplay between socio-economic and biophysical forces. Landscape ecologists use a wealth of indicators based on landscape patterns to evaluate landscape diversity (LD), landscape structure, the naturalness of landscapes, and land-use intensity. Indicators such as the human appropriation of net primary production (HANPP) are increasingly used to evaluate the changes in ecosystem processes induced by land use. Based on a study region in the central part of Lower Austria ( Niederösterreich), this paper explores interrelations between patterns and processes in landscapes by empirically analysing: (1) whether landform affects spatial patterns of HANPP, (2) whether HANPP is correlated with indicators of landscape naturalness, and (3) whether HANPP is correlated with LD and landscape patterns. According to our results, landform influences patterns of HANPP but cannot explain them entirely. We found strong monotonous correlations between HANPP and urbanity, an indicator for the prevalence of human-dominated land-cover classes, as well as between HANPP and the hemerobiotic state, an indicator for landscape naturalness. We found significant unimodal (hump-shaped) correlations between HANPP and the LD. Landscape pattern indicators showed weak but significant relations to HANPP.

Food-web constraints on biodiversity-ecosystem functioning relationships.

The consequences of biodiversity loss for ecosystem functioning and ecosystem services have aroused considerable interest during the past decade. Recent work has focused mainly on the impact of species diversity within single trophic levels, both experimentally and theoretically. Experiments have usually showed increased plant biomass and productivity with increasing plant diversity. Changes in biodiversity, however, may affect ecosystem processes through trophic interactions among species as well. An important current challenge is to understand how these trophic interactions affect the relationship between biodiversity and ecosystem functioning. Here we present a mechanistic model of an ecosystem with multiple trophic levels in which plants compete for a limiting soil nutrient. In contrast to previous studies that focused on single trophic levels, we show that plant biomass does not always increase with plant diversity and that changes in biodiversity can lead to complex if predictable changes in ecosystem processes. Our analysis demonstrates that food-web structure can profoundly influence ecosystem properties.

Changes in ecosystem processes induced by land use: Human appropriation of aboveground NPP and its influence on standing crop in Austria

Human land use influences important properties of terrestrial ecosystems, such as energy flow, standing crop, and biomass turnover. Human interference with ecological energy flows may be studied by calculating the “human appropriation of NPP” (HANPP), defined as the difference between the net primary production (NPP) of potential vegetation and the actual NPP remaining in ecosystems after harvest. Comparing the standing crops of the potential vegetation and actually prevailing vegetation, we demonstrate the human impact on the amount of carbon stored in living vegetation. We discuss these concepts using empirical results for aboveground vegetation in Austria calculated from statistical data and from land use and land cover models derived from remote‐sensing data. According to our calculations the human appropriation of aboveground NPP in Austria today amounts to ∼50%. The aboveground standing crop (biomass stock) of the vegetation prevailing in Austria today is ∼64% lower than that of the potential vegetation.

Assessing Simulated Ecosystem Processes for Climate Variability Research at Glacier National Park, USA

Glacier National Park served as a test site for ecosystem analyses that involved a suite of integrated models embedded within a geographic information system. The goal of the exercise was to provide managers with maps that could illustrate probable shifts in vegetation, net primary production (NPP), and hydrologic responses associated with two selected climatic scenarios. The climatic scenarios were (a) a recent 12-yr record of weather data, and (b) a reconstituted set that sequentially introduced in repeated 3-yr intervals wetter–cooler, drier–warmer, and typical conditions. To extrapolate the implications of changes in ecosystem processes and resulting growth and distribution of vegetation and snowpack, the model incorporated geographic data. With underlying digital elevation maps, soil depth and texture, extrapolated climate, and current information on vegetation types and satellite-derived estimates of leaf area indices, simulations were extended to envision how the park might look after 120 yr. The predictions of change included underlying processes affecting the availability of water and nitrogen. Considerable field data were acquired to compare with model predictions under current climatic conditions. In general, the integrated landscape models of ecosystem processes had good agreement with measured NPP, snowpack, and streamflow, but the exercise revealed the difficulty and necessity of averaging point measurements across landscapes to achieve comparable results with modeled values. Under the extremely variable climate scenario significant changes in vegetation composition and growth as well as hydrologic responses were predicted across the park. In particular, a general rise in both the upper and lower limits of treeline was predicted. These shifts would probably occur along with a variety of disturbances (fire, insect, and disease outbreaks) as predictions of physiological stress (water, nutrients, light) altered competitive relations and hydrologic responses. The use of integrated landscape models applied in this exercise should provide managers with insights into the underlying processes important in maintaining community structure, and at the same time, locate where changes on the landscape are most likely to occur.

ASSESSING SIMULATED ECOSYSTEM PROCESSES FOR CLIMATE VARIABILITY RESEARCH AT GLACIER NATIONAL PARK, USA

Glacier National Park served as a test site for ecosystem analyses that involved a suite of integrated models embedded within a geographic information system. The goal of the exercise was to provide managers with maps that could illustrate probable shifts in vegetation, net primary production (NPP), and hydrologic responses associated with two selected climatic scenarios. The climatic scenarios were (a) a recent 12-yr record of weather data, and (b) a reconstituted set that sequentially introduced in repeated 3-yr intervals wetter–cooler, drier–warmer, and typical conditions. To extrapolate the implications of changes in ecosystem processes and resulting growth and distribution of vegetation and snowpack, the model incorporated geographic data. With underlying digital elevation maps, soil depth and texture, extrapolated climate, and current information on vegetation types and satellite-derived estimates of leaf area indices, simulations were extended to envision how the park might look after 120 yr. The predictions of change included underlying processes affecting the availability of water and nitrogen. Considerable field data were acquired to compare with model predictions under current climatic conditions. In general, the integrated landscape models of ecosystem processes had good agreement with measured NPP, snowpack, and streamflow, but the exercise revealed the difficulty and necessity of averaging point measurements across landscapes to achieve comparable results with modeled values. Under the extremely variable climate scenario significant changes in vegetation composition and growth as well as hydrologic responses were predicted across the park. In particular, a general rise in both the upper and lower limits of treeline was predicted. These shifts would probably occur along with a variety of disturbances (fire, insect, and disease outbreaks) as predictions of physiological stress (water, nutrients, light) altered competitive relations and hydrologic responses. The use of integrated landscape models applied in this exercise should provide managers with insights into the underlying processes important in maintaining community structure, and at the same time, locate where changes on the landscape are most likely to occur.

What Do Species Do in Ecosystems?

Three aspects of the role of species in ecosystems are reviewed. (1) Theoretically, what are the possible relationships between ecosystem processes (Likens' (1992) transformation and flux of energy and matter) and the species richness of communities ? (2) Summaries of two experiments with artificially constructed terrestrial ecosystems in the controlled environment facility known as the Ecotron are described. The first draws attention to the role of earthworms as ecosystem engineers; the second explores changes in ecosystem processes in mesocosms assembled with three different levels of biological diversity