The Influence Factors of Sub-Alpine Forest Restoration in Miyaluo, West Sichuan
Zhang Yuandong Zhao Changming Liu Shirong(Institute of Forest Ecology,Environment and Protection,CAF Beijing100091)
Western Sichuan sub-alpine is an extension of Qinghai-Tibet Plateau to southeastern China and is covered with forests in the valleys, mainly dark coniferous ones. As a result of long-term over-logging on a large scale, they have been greatly reduced and degraded. In this paper, in order to analyse the influences of forest management and topography factors on sub-alpine forest restoration in west Sichuan, Miyaluo was selected as a case study area. The cutting volume, artificial regeneration area and tending area from 1953 to 2000 were collected, forest survey and plot investigation were taken in 7 watersheds. The results showed that sub-alpine forest restoration in west Sichuan was influenced by both forest management and natural regeneration. Taking Miyaluo as an example, forest management could be divided into two stages, cutting period (1953—1978) and restoration period (1978—now), and cutting period also could be divided into period Ⅰ (1953—1965) and period Ⅱ (1966—1978). In cutting period with logging on a large scale and fast regeneration, artificial regeneration could not catch up with cutting, tending could not catch up with regeneration, the young growth tending was worse and survival rate was low, especially in period Ⅰ. That resulted in the mosaic patch of plantations, natural secondary forests and ones from both artificial and natural regeneration in cutting area. The pattern was influenced by aspect. Spruce from artificial regeneration was dominant on half-sunny and sunny slope; birch and firs from natural regeneration were on half-shady and shady slopes. In restoration period, cutting was little and stopped at last, artificial regeneration was little; survival rate was high from well tending to young growth. Spruce regenerated artificially in 1980s and at the beginning of 1990s had closed to young forests after successive tending with many years. In sub-alpine forest regions, the regeneration methods and species should be selected according to the habitat types that changed with altitude and aspect. In the sites that restoration can be go on naturally, natural regeneration should be promoted to ensure the persistence and stability of forests.