New composition patterns of dominant tree species in high elevation forest gaps of JuiZhaiGou National Park, China in a changing environment
This study examines 29 forest gaps in JuiZhaiGou National Nature Reserve (JNNR), Sichuan, China, between 2900m and 3200 m. Our study examined, if tree species establishment and growth in high elevation gaps is changing and if so, why; and the potential for future changes. Historically, Abies faxoniana (fir) and Picea purpurea (spruce) both conifer species have dominated the canopy of sub-alpine, montane forests in JNP. Gap trees were cored and measured for tree species numbers, age and growth parameters and gaps were measured for size and environmental conditions.
Results indicate: the numbers of Betula albo sinensis, a broadleaf, hardwood tree species, have increased in the canopy level; B. albo-sinensis have most significantly increased their numbers in gaps, 1. with steep slopes (>30 degrees), small area (< 300 m2 ) with thin soil (<5cm depth) or 2. large area (>600 m2) with deep soil (>12 cm depth). For Abies and Picea spp. establishment is inversely correlated with soil depth ; soil >10 cm depth, on slopes < 30 degrees needed for dependable seedling establishment. Changing climate, regarding temperature, cloud cover and precipitation patterns favor establishment and growth of B. albo sinensis and inhibit the Abies and Picea spp. Results indicate historically, subclimax B. albo-sinensis is becoming a more important member of the high elevation forests potentially changing slope stability and runoff water characteristics.