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Accueil du site → Doctorat → États-Unis → 1974 → A comparative modelling study of plant growth systems in a desert ecosystem

New Mexico State University (1974)

A comparative modelling study of plant growth systems in a desert ecosystem

Reynolds, James F.,

Titre : A comparative modelling study of plant growth systems in a desert ecosystem

Auteur : Reynolds, James F.,

Université de soutenance : New Mexico State University

Grade : Doctor of Philosophy (PhD) 1974

The use of modelling as a tool In ecosystem analysis has mushroomed In recent years. However, few guidelines are currently available. Thus, the selection of a modelling approach must Involve both the model goals and constraints Imposed by a limited data base. Two possible modelling approaches are within quantitative and a qualitative formats. The quantitative • approach In ecology usually Incorporates the level-rate paradigm of Forrester, utilizing systems of differential equations to describe component relationships. A high level of model precision is one of the objectives. The qualitative approach, as used here, Incorporated the pulse-reserve paradigm of Bridges, utilizing blocks of logic statements to test for the presence or absence of specific driving variables. A high level of model realism Is one of the goals using this technique. These two approaches were used to model plant growth systems In a desert ecosystem. Both the level-rate and the pulse-reserve paradigms were useful for abstracting the system and forcing clarification of specific hypotheses about the functioning of desert plants. The pulse-reserve paradigm Is probably best suited for water-controlled ecosystems, since many responses are threshold related. The level-rate paradigm Is a more general scheme, although generally more complex. In the level-rate model, plant growth was modelled by dividing the plant Into various compartments for tracing carbon allocation. However, most of the necessary biological mechanisms were described by "fuzzy laws" resulting In loss of precision and realism. The model did exhibit reasonable stability over a four year simulation. Although void of functional relationships or mechanisms, the pulse-reserve model did offer long-term stability. The reservetrigger-pulse sequence of the model Is biologically real and represents an adaptive strategy for organisms in arid environments. The possibility of expanding this approach for an entire system Is discussed. A model Is proposed that Incorporates the more precise level-rate formulation for primary producers and the pulse-reserve paradigm for higher trophic levels.

Sujets : Growth (Plants)—Mathematical models. Plant ecology. Desert plants.

Annonce (NMSU Library)

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Page publiée le 27 janvier 2018, mise à jour le 11 novembre 2018