Chin J Plan Ecolo ›› 2004, Vol. 28 ›› Issue (2): 204-209.DOI: 10.17521/cjpe.2004.0030

• Research Articles • Previous Articles     Next Articles

THE EFFECTS OF GAP SIZE AND WITHIN GAP POSITION ON THE SURVIVAL AND GROWTH OF NATURALLY REGENERATED ABIES GEORGEI SEEDLINGS

LIU Qing   

  • Published:2004-02-10
  • Contact: LIU Qing

Abstract:

The survival and growth of Abies georgei seedlings growing in forest canopy gaps was investigated over a 4-year period on the Baima Snow Mountain in northwest Yunnan Province, China. Of the total gaps surveyed in A. georgei forests, 45% were small (gap area <50 m2), 35% were medium sized (50-100 m2) and 20% were large (>100 m2) gaps. Seedling growth rates, survivorship, abundance and size were measured and compared among the three different sized gaps and under the closed forest canopy and within gaps according to their position (north, south and center) in each gap. The seedlings all originated from natural seed rain. The results showed that there were significant differences in the size and number of seedlings among the different sized gaps and understorey. There were 1.5 times more seedlings in larger gaps than in smaller ones and very few seedlings (0.5 ind.·10 m-2) were found in the understory. The survival of A. georgei seedlings within gaps tended to increase from south to north positions within the larger gaps, whereas survivorship did not vary within the small and medium sized gaps. Seedling size, in terms of both height and basal diameter, in the different sized gaps was as follows: medium > small > large > understorey. Relative growth rates showed a similar pattern. The average annual growth in height was (7.8±0.5) cm in medium gaps. Furthermore, size and annual relative height growth of seedlings did not differ significantly among positions within the medium and small gaps, but seedling height peaked in the southern position of large gaps and declined towards the center and north edges. Seedling establishment was greater in gaps than under the closed-canopy. Due to adaptation to light conditions, relative growth rates of seedlings were greatest in medium sized gaps but were relatively low in regions of the large gaps that had greater exposure to direct solar radiation as well as in small gaps that were shaded and received little direct solar radiation. Finally, based on observed changes in survival and growth of seedlings over four growing seasons, the author suggests that medium sized forest canopy gaps provide the best habitat for regeneration of A. georgei seedlings.