Using geoestatistics for assessing biodiversity of forest reserve areas

Débora Andréia Neves, Fábio Lemos, Antonio Paz González, Sidney Rosa Vieira, Glécio Machado Siqueira
2010 Bragantia  
Protecting natural mosaics as forest reserves poses a challenge, because if they hold significant high levels of biodiversity, they may function as key seed sources for regenerating ecosystems and adjacent reforested areas. Currently, there is lack of information about the spatial organization of native species in core forest fragments remaining between reforested fields. Biodiversity as measured by species and number of individuals was assessed in two forest reserve zones located within
more » ... tations of Eucalyptus sp and Pinus sp in Agudos, São Paulo, Brazil. The main objective was to compare the state of biodiversity within two natural areas with contrasting disturbance levels; a second objective was to investigate recognisable patterns of species and individuals spatial distribution. A grid-like set of plots was set up for data collection over each of the two study areas. Natural species were aggregated onto two groups using height classes, inferior level (< 0.5 m) and superior level (> 1.3 m) layers. Within each natural area the number of species and individuals of the height class > 1.3 m was counted on 50 square plots of 100 m² (10 x 10 m) whereas those of the height class < 0.5 m were counted on 250 subplots of 1 m² (1 x 1 m). Data analysis involved both statistical and geostatistical methods. Experimental semivariograms of number of species and individuals were modelled by a nugget component plus a spherical structure with autocorrelation ranging from approximately 20 to 60 m. Cross-semivariograms could also be computed and modelled in some cases. Nugget effects of both species and individual's count for inferior level were shown to be larger for small sized plots, whereas the spatially structured component increased as the plot size increased. Individual's count showed a higher continuity at close distances than species number in the superior level (> 1.3 m), and the reverse was true for the inferior level (< 0.5 m). Usefulness of kriging maps for comparing patterns of spatial variation between the two studied natural mosaics has been illustrated.
doi:10.1590/s0006-87052010000500014 fatcat:tzgwerzkrbffznfnmjvc4ihyte