Showing papers by "Donald L. DeAngelis published in 1989"
TL;DR: In this article, the authors summarize the current understanding of several important types of stability in the food web and describe the theoretical and empirical evidence relating them to nutrient limitation and nutrient cycling.
Abstract: The importance of nutrient limitation and recycling in ecosystems is widely recognized. Nutrients, defined in the broad sense as all material elements vital to biological functions, are in such small supply that they limit production in many ecosystems. Such limitation can affect ecosystem properties, including the structure and dynamics of the food webs that link species through their feeding relationships. What are the effects of limiting nutrients on the stability of ecosystem food webs Most of the literature on food web stability centers around the dynamics of population numbers and/or biomasses. Nevertheless, a growing body of theoretical and empirical research considers the role that both nutrient limitation and recycling can play in stability. In this paper, it is the authors objective to summarize the current understanding of several important types of stability. The theoretical and empirical evidence relating these types of stability and nutrient cycling is described. A central generalization is produced in each case.
182 citations
TL;DR: A new functional form, the Additive model, is selected as the most general function based on available data and a general theoretical framework is presented that illustrates the commonalities and differences among the functions.
146 citations
TL;DR: In this paper, Monte Carlo simulation is used to integrate solutions of a tundra model and a coniferous forest model across within-biome heterogeneity in the models' climatic driving variables.
Abstract: Ecologically sound models of the terrestrial biosphere are needed in the investigation of the Earth system and global change. Traditional ecosystem models simulate many processes and dynamics relevant to the functioning of the Earth system, but their application is limited by their local, small-scale, often site-specific nature. We address this limitation by deriving a method for predicting regional biosphere dynamics by extrapolation from smaller-scale ecosystem models. We use models of local ecosystem carbon dynamics to predict the seasonal exchange of CO2 between the atmosphere and terrestrial ecosystems of 64°N to 90°N latitude. Monte Carlo simulation is used to integrate solutions of a tundra model and a coniferous forest model across within-biome heterogeneity in the models' climatic driving variables. The product of the expected value of each model's output and the area of the region occupied by that biome or ecosystem type is an estimate of biome-scale CO2 exchange. Regional CO2 exchange is the sum of the biome exchanges. Comparisons of the extrapolation's results with independent estimates of seasonal CO2 exchange and annual net primary production support the proposition that extrapolation of ecosystem models can be used to simulate regional biosphere dynamics.
40 citations
TL;DR: The time-scale dependent approach is important because it emphasizes how local (transient) solutions may be more ecologically relevant to stability calculations than overall (global) solutions.
Abstract: The study of freshwater pelagic communities is entering an exciting and controversial phase. Recent efforts to clarify how food web interactions differ from food chain interactions have emphasized the various, often subtle, repercussions of top predators on communities. Predators can modify community structure not only through directly imposed death rates, but also through direct and indirect effects on prey interactions, behavior, life-styles and morphology (e.g. induction of defenses). In some cases, the effects influence ecosystem properties (material fluxes, turnover rates and primary production). Attempts to trace food web impacts in enclosure and lake studies have revealed important time-dependent system properties. Severe resource limitation of fast variables (phytoplankton and small zooplankton) stabilizes lower trophic levels, whereas the potentially destabilizing effects of fish population oscillations are long compared to the growing season and subject to year-to-year climatic vagaries. The time-scale dependent approach is important because it emphasizes how local (transient) solutions may be more ecologically relevant to stability calculations than overall (global) solutions.
32 citations
TL;DR: In this paper, a black and white video camera and an image analyzer were used to measure the length of oak roots from which soil had been washed and arranged within a 13.5 × 19 cm rectangle on clear plastic sheets and photocopied (dry process).
Abstract: A black and white video camera and an image analyzer were used to measure the length of oak roots from which soil had been washed. The image analyzer is an automated intersect counter which uses the same basis for length estimation as the modified line intersect method. The roots were arranged within a 13.5 × 19 cm rectangle on clear plastic sheets and photocopied (dry process), then the lengths of the photocopied root images were measured with the video system. Two measurements were made on each photocopy, with a 90° rotation of the photocopy made between the two measurements. The two measurements were summed to obtain an index of root length. The automated system tested had insufficient resolution to detect very fine roots (<0.3 mm); however, the video method was found to be linearly correlated (R2 = 0.92) with the modified line intersect method. Other root samples may require enhanced system resolution to achieve adequate correlation between methods. Once the video method has been calibrated, length of...
16 citations
TL;DR: It is shown that increasing nutrient input may at first lead to increased resilience and that resilience decreases sharply only immediately before the Hopf bifurcation is reached.
13 citations