Regeneration characteristics for major tree species of a secondary Pinus tabulaeformis forest in the Ziwu Mountains

Regeneration characteristics of major tree species are very important to forest regeneration and sustainable management of secondary Pinus tabulaeformis forests in the Ziwu Mountains , Gansu Province .The primary objective of this study was to examine the regeneration patterns of major trees in gaps and non-gaps of a secondary P . tabulaeformis forest .Major trees of the shrub layer in 25 gaps and 25 non-gaps were surveyed and classified into four ecological groups of species according to their importance value (IV).Results of regeneration in gaps showed that Group 1 :six tree species that had a strongly positive response ;Group 2 :two tree species that had a strongly negative response ;Group 3 :eight tree species that had a moderately negative response ;and Group 4 :15 tree species that had no response .For Group 1 the average density and average height of the seedlings in the gaps were superior to those in the non-gaps .For the four ecological groups of species , in gaps and non-gaps there were obvious differences , such as tree density , tree height , the major trees' IV in composition .Regeneration of major trees in gaps was also quicker than non-gaps .Thus , gaps provided favorable growth conditions for regeneration of major trees in secondary P .tabulaeformis forests of the Ziwu Mountains .[ Ch , 2 fig .1 tab .14 ref .]