PARENT SESSION
Thursday, August 10, 8:00-11:30 am
COS 76 - Spatial ecology I
L-2, Lobby Level, Cook Convention Center
Presiders: E Damschen

Self-organized spatial patterns of vegetation in Mediterranean ecosystems along a degradation gradient.

Alados, Concepcion^*,1, ¹ Insituto Pirenaico de Ecología, Zaragoza, Zaragoza, Spain

ABSTRACT- There is evidence that catastrophic shifts can be associated with self-organized spatial patterns of vegetation and that environmental heterogeneity might reduce catastrophic shifts in ecosystems. There is increased interest in vegetation spatial pattern as an indicator of transition shifts associated with catastrophes, although much remains unknown about the mechanisms that underlie spatial pattern formations. In this study, we quantified the spatial distribution patterns of the vegetation by fractal analyses, using the fractal information dimension and long-term spatial autocorrelation (Detrended Fluctuation Analyses, DFA). We compared different scenarios along a gradient of degradation due to grazing disturbance and increased bare soil. We first examined how the spatial heterogeneity of species distributions is associated with plant species diversity and the importance of self-organizing processes in the control of pattern formations in a range of Mediterranean ecosystems from semiarid steppes to sub-humid matorral and to subalpine grasslands. In most of them the spatial heterogeneity of species distributions increased along a habitat degradation gradient defined by an increase in bare soil; however, the processes leading to patchy vegetation differed in the different communities. In Alpha-steppe and subalpine grassland, the increase in heterogeneity was associated with self-organizing vegetated non-vegetated patches, although that relationship also depend on the degree of vegetation preservation. In the semiarid shrubland and in the gypsicola shrubland community the increased heterogeneity of spatial species distribution is related with the self-organized distribution of dominant species. The relationship between increased soil connectivity (alpha of vegetated non-vegetated patches) and the self-organizing capacity of characteristic dominant species that act as nursery plant were also discussed. In the sub-humid matorral the heterogeneity of species distributions is the result of the self-organizing distributions of dominant species, and increases in bare soil is not associated with self-organization of vegetated patches. Finally, we discussed the importance of competition and facilitation processes in the control of spatial pattern formation.

Key words: spatial patterns, fractals, self-organization