Fifteen-year Changes of Tree Layer in Secondary Castanopsis-schima Humid Evergreen Broad- Biomass and Dynamics of Soil Environment During the Early Stage of Vegetation Restoration in a Degraded Dry-hot Mountain Area of Nanjian, Yunnan
Abstract:This paper presents the results of a study on above ground biomass of the major artificial (revegetation) communities at early stage (3-5 years). It also describes the fluctuation of soil moisture and soil nutrients during vegetation recovery in a degraded dry-hot mountain area of Nanjian county, in western Yunnan. It shows that, 1) many introduced plant species (Tephrosia candida, Pueraria wallichii, Eucalyptus robusta, Acacia richii, A. mearnsii, etc. ) were strongly adapted to the dry-hot climate: they grew rapidly during early stages, with a fast canopy closure occurring in 3-4 years; the total biomass of these artificial communities were higher than that of the local secondary shrub (Dodonaea viscosa) community; the above ground biomass and gross average productivity of the introduced plants were 3-16 times and 5-20 times, respectively, as much as those of Dodonaea viscosa; their growth was also faster than that of the native species Pinus yunnanensis; 2) the soil moisture under the artificial community was twice that of bare slopes; topsoil moisture increased by more than 200% during the rainy season, but in the dry season the soil moisture under the introduced vegetation was close to or even lower than that of bare slopes; 3) soil nutrient cycling also improved after vegetation recovery; while organic matter and available K increased, there was no significant change in total N (it dropped slightly); available P and soil pH decreased. Changes of soil nutrients occurred mainly in the topsoil. These results show that restoration of this artificial vegetation community and the associated soil ecosystem was still unstable.