OSCAR ALBERTO AGUIRRE CALDERON, JAVIER JIMENEZ PEREZ
University of Nuevo Leon, Departament of Silviculture, Mexico
The structure of a forest may be defined by the spatial distribution of the tree positions, by the spatial mingling of the different tree species and by the spatial arrangement of the tree dimensions. The spatial structure is one of the characteristic attributes of a forest, the problem is to characterise and describe forests with different spatial characteristics more accurately, using affordable assessment techniques.
Characterisation of forest ecosystems structure must be based on quantitative indices that allow objective analysis of human influences or natural succession processes. The objective of this study is the compilation and assessment of diverse quantitative variables to describe structural attributes and diversity from the arboreal stratum of the ecosystem, as well as different methods of forest inventory to obtain such indices. For the evaluation of the species structure and diversity the Indices of Shannon H', Species Profile A, Segregation S of Pielou and the Species Mingling Index Mi are discussed. The Aggregation Index R of CLARK & EVANS and the Contagion Index Wi, were include in order to describe the horizontal structure of the ecosystem. Finally, for the characterisation of the dimensional structure, the Homogeneity Coefficient H, and the Indices of Diameter Differentiation TDi, Height Differentiation THi and the tree attribute Dominance of Neighbours Ui were analysed.
Case studies of detailed analysis of forest spatial structure and diversity in the Federal States of Durango and Nuevo León, Mexico, are presented. The selected variables describe the distributions of spatial mingling, size differentiation and contagion, which can be easily interpreted allowing quantitative comparisons between complex forest structures. The application of such indices in an integral method of forest inventory allows a better description and reproduction of the ecosystems, as well as the development of indicators of sustainability of forest resource management.
Keywords: Biodiversity, contagion, diameter differentiation, mixed stands, species mingling