Evaluation of the Abundance, Form of Establishment, and the Causes of Variation of Pine Regeneration in Coniferous Stands of the Western Sierra Madre of Durango, Mexico

2001

S. 175-179

31 Lit. Ang.

Unselbständiges Werk

200091292

This study has investigated the effect of regeneration cuts on the abundance, the patterns of establishment, and the sources of variation of the spatial establishment of natural regeneration. In total twenty forest stands under this silvicultural treatment, conducted in 1989, were evaluated. The methodology consisted in isolating quadrats of one hectare inside the forest stand and diving this area into smaller quadrats of 5 x 5 m, where seedling density, age, height, and diameter, the dasometric characteristics of seed trees, as well as the depth of litter layer were evaluated. Ecological site classification variables at the quadrat scale such as slope, aspect, site index, degree of grazing, degree of forest fires, pine species, tree cover, and number of remaining trees were also measured. The data were collected from June through November of 1996. The results showed that geometric average seedling density, age, diameter and height were 2780 seedlings ha®Ü, 2.2 years, 1.0 cm, and 0.20 m, repectively, indicating a chronic deficit of seedlings and that 4 years of site growth potential had been lost. Although seed trees distributed randomly on each quadarat (p > X¬ >/gleich 0.25, ..., 0.99), seedling established in clusters at all spatial scales tested (5 x 5 m; 10 x 10 m; 20 x 20 m; and 50 x 50 m; p > X¬ </gleich 0.0001). Clusters of seedlings were less obvious at larger spatial scales stressing the relative importance on the spatial distributed of seed trees. The sources of spatial variation in regeneration density were statistically associated to: 1) at the quadrat scale to depth of litter layer (r = 0.52, p < 0.01), degree of grazing (r = -0.62, p < 0.01), and 2) at the subquadrat scale to diameter (r = 0.18, p < 0.01) and height (r = 0.20, p < 0.01) of seed trees, as well as to depth of litter layer (r = 0.26, p < 0.01). Therefore, this report stresses the need to improve silvicultural methods with the aim of promoting the quick establishment, with the sufficient abundance, of plant regeneration, to control human disturbances such as grazing and fires to enhance seedling survival, and to further carry out studies on plant regeneration dynamics with the major objective of conducting sustainable forest management practices on the coniferous forest of the western Sierra Madre of Durango, Mexico.