The objective of this paper was to investigate the sensitivity to degradation of semiarid plant communities in terms of plant cover and fragmentation, quantifying relationships between landscape characteristic (physical, socio-economical and historical) and vegetation degradation. The degradation of vegetation was measured as the degree of coverage of the two dominant vegetation types (i.e. tall arid brush and tall grass steppe), while fragmentation was measured as patch size and isolation. Data were obtained using GIS tools, and analyzed by logistic regression and linear multivariate regression. Results showed denser coverage at more elevated, gradual slopes that were not sea-oriented. Historical elements of the landscape had a significant effect on current natural vegetation. According to the fragmentation patterns, the vegetation is in fairly good condition (medium coverage had the largest patches but dense coverage was less isolated) but attention must be given to preserve vegetation, due to the relationships between fragmentation and human activities. Moreover, the protection plan under way in the area appeared to favour denser vegetation cover, while human activities had a measurable effect on vegetation degradation.

The work was supported by the EU under its INCO-DC Program, contract number ERBIC18-CT98-0392: DRASME (Desertification risk Assessment in Silvopastoral Mediterranean Ecosystems) and by Spanish CICYT program, project number REN2002-04668/GLO (Efectos de la fragmentación y uso del suelo en la conservación y dinámica de las zonas esteparias Mediterráneas). ‘Gobierno de Aragón’ has also supported this work by a grant to Y.P. The support from both programs and grant is gratefully acknowledged.

18 páginas, 2 figuras, 4 tablas.

Peer reviewed