COS 125-2 - Ecosystem properties self organize in response to a directional fog-vegetation feedback

Friday, August 12, 2011: 8:20 AM
5, Austin Convention Center
Daniel E. Stanton1, Beatriz Salgado-Negrete2, Lars O. Hedin1 and Juan J. Armesto3, (1)Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, (2)Ecology, CASEB, Pontificia Universidad Católica de Chile and Instituto de Ecologia y Biodiversidad, Santiago, Chile, (3)Ecology, Universidad Católica de Chile, Institute of Ecology and Biodiversity, Santiago, Chile

Feedbacks between vegetation and resource inputs can lead to the local self-organization of ecosystem properties.  In particular, feedbacks in response to directional resources can create complex spatial patterns, such as vegetation banding. Fog-water inputs in northern Chile have led to the persistence of relict temperate rainforests under extremely low rainfall conditions. We conducted transects across forest patches to document change in various ecosystem properties that have the potential to generate internal feedbacks in plant, water and nutrient distributions (soil moisture, soil C & N, species composition, light availability). A self-organizing response to directional inputs predicts strong assymmetries in many of the properties, with abrupt changes at the windward and gradual changes at the leeward edges


Our results show that spatial patterns of the patches are not driven by underlying soil differences, but rather by positive feedbacks between forest structure and fog interception. These positive feedbacks caused strongly assymetrical patterns in moisture, carbon and nitrogen of soils within and between patches, but not of other non-fog driven ecosystem characteristics such as average plant height. We also show that these asymmetries, in turn, lead to asymmetrical patterns of plant species composition and recruitment, Ccausing individual patches to advance windward across the landscape over time. Soil properties reveal a leeward “footprint” of the former location of patches. This study provides strong support for the self-organization of numerous ecosystem properties in response to directional resource inputs.

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