Response of Chinese pine regeneration density to forest gap and slope aspect in northern China: A meta-analysis

Abstract

Chinese pine is a Chinese endemic species with important ecological functions. Forest gaps and slope aspect are important factors in the regeneration of Chinese pine by influencing light and moisture, but what these effects are is still up for debate. Meanwhile, the effects of forest gaps and slope aspect are poorly studied in response to different forest types and ages, as well as temperature and precipitation. We established literature selection criteria that finally identified 101 and 69 pairs of study cases on forest gaps and slope aspect, respectively. The overall effect values were obtained by meta-analysis and found that gap and shady slope habitats had significant positive effects on the regeneration density of Chinese pine (P < 0.05). The gap most enhanced the regeneration density in a plantation setting (P < 0.05). In pure stands of Chinese pine, shady slopes can significantly increase regeneration density (P < 0.05). Forest gaps and shady slopes contributed most to Chinese pine regeneration density in mature stands compared to near mature stands, and over mature stands (P < 0.05). There was no significant effect of stand gap size on regeneration density (P > 0.05). In particular, the edges of the gap appeared to be well-suited for regeneration (P < 0.05). In our study area, mean annual precipitation resulted in a significant increase in the effects of the gap and shady slope as precipitation declined (P < 0.05). This meta-analysis helps elucidate the effects of forest gap (position or area) and slope aspect on Chinese pine regeneration. With global climate change, Chinese pine regeneration may prefer the edge of forest gaps and shady slopes.