STAND STRUCTURE OF Pinus hartwegii AFFECTED BY FIRE USING NEIGHBOURHOOD PARAMETERS IN THE SIERRA MADRE ORIENTAL, MEXICO.

Abstract

The objective of this research was to characterize the pattern of spatial structure of a Pinus hartwegii forest in the Sierra Madre Oriental, affected by a fire in 1998. Sampling was stratified by fire severity. Three fire severity classes were defined based on the degree of crown consumption (low, medium and high). Three sample plots of 40m x 40m were established for each severity. The variables obtained for all trees with a diameter at breast height (DBH) ≥ 5 cm in each plot were: DBH to 1.30 m (cm), height (m), spatial location by recording the azimuth (°) and distance (m) from center of the plot to each tree. To describe the stand structure three groups of indices were employed: “contagion†and “distances†(Wi and Di), “dominance†(Ui), and “size differentiation†(TDi and THi) for DBH and height respectively. An analysis of variance was performed to detect differences between dasometrics parameters by fire severity. Statistical analysis shows significant differences (p>0.001) in the parameters such as basal area, diameter, and height, along the low, medium, and high fire severities. The characterization of the Pinus hartwegii spatial structure suggests that, with increasing degree of fire severity, the stands showed an increase on the aggregation index, however, the dimensional differentiation and dominance indices decreases as the fire severity increases.