Regeneration characteristics of gaps and their effect on Abies fargesii forests in the Shennongjia National Nature Reserve, China

Abstract

Abies fargesii is an evergreen tree species of the Pinaceae family, one of the most important cultivated timber species, endemic to China. It is of great importance for the maintenance of vegetation landscape and the preservation of endangered animal species. Community regeneration of forest gaps and their effect on A. fargesii forests in the Shennongjia National Nature Reserve were studied based on two-year field survey data. The results show that 1) forest gap regeneration is an important approach for the regeneration of A. fargesii communities; regeneration characteristics in the gaps of the broad-leaved species Betula albo-sinensis Burk. and the shade-tolerant species A. fargesii differed from those of understory species. 2) A. fargesii is most predominant in early gap regeneration but, over time, is gradually replaced by other species. Seedlings less than three years old accounted for 45.7% of all seedlings and only 6.3% of saplings older than seven years. 3) In terms of height and basal diameter in different sized gaps, size of seedlings showed the following trend: medium > small > large > understory; the relative growth rate appeared in the same order. 4) The size of seedlings did not appear different between within-gap positions in medium and small gaps, but the tallest seedlings grew in the south of the large gaps and declined towards the center and north edges. 5) Principal component analysis suggests that the most important factors for the growth and distribution of A. fargesii seedlings decreased in order of gap size, slope direction, gap microenvironment and tree-shrub-grass cover.