Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Filter-Feeding Forests : Epiphytes and Fog in the Self-Organization and Function of Ecosystems

Auteur : Stanton, Daniel E.

Université de soutenance : Princeton University

Grade : Doctor of Philosophy (PhD) 2011

Résumé
The interaction between organisms and their environment is often simplified to a passive view of organisms as primarily subject to their environments, but better understood as a series of feedbacks between organisms and environmental processes. These feedbacks can generate complex spatial patterns of organisms and processes. In this dissertation I explore the mechanisms and consequences of a particularly striking yet understudied feedback, the harvesting of fog-water by vegetation ; and the role of epiphytes, a hallmark of fog-influenced environments, in ecosystem processes. The chapters of this dissertation address a range of scales, from the local effects of individual organisms and their organization into communities to the ecosystem and landscape effects that these local effects can have.

The harvesting of fog water requires the presence of a physical structure to inter cept it. This simple observation leads to powerful predictions about the increased availability of water (and as a result, nutrients) in the near vicinity of plants in foggy places. The results of my field measurements and experiments are the first to ex perimentally show that plant structures (natural or artificial) in Peru´ and Chile can harvest fog water and generate ‘islands of fertility’ at their base. When there is suffi cient overlap of plant canopies, this process can lead to the self-organization of entire forest-patches in arid but foggy locations in coastal Chile. These patches form pre dictable bands that appear to slowly move windwards across the landscape, leaving a soil chemistry ‘footprint’ in their wake. These bands were predicted by theorists for similar sites, but this dissertation provides novel insights into spatial and temporal dynamics of soil properties and organisms across such bands, supported by field data. One of the plant growth-forms most commonly associated with fog is epiphytism (use of other plants as a substrate for growth). Epiphyte morphologies and com munities can change across fog-availability gradients, and I show that morphologies theoretically better adapted to fog water harvesting are more abundant at higher fog availability. This chapter involves the novel application of theory from marine organisms and fractal geometry to epiphytes.

Présentation et version intégrale (ProQuest)