Forest Hydrological Characteristics And The Biogeochemical Processes Of Major Nutrients In Shaoshan Subtropical Forest, Central-south China

Shaoshan forest (Caijiatang catchment) is situated in Xiantan city of Hunan province in central-south China, which is with subtropics and hills and coniferous-deciduous mixed forests. There is an annual mean precipitation of 1200~1700 mm and distinct four seasons in a year in Shaoshan. Monitoring and sampling of atmosphere, soil, surface water and soil water were conducted in Caijiatang catchment in Shaoshan forest from January 2000 to December 2003. The field design and sampling methods and data quality controlling were performed according to the EMEP (European Monitoring and Evaluation Program) manual.Forest hydrology has the important impact on the forest productivity and the nutrient cycling. Canopy interception loss is significant in the evapotranspiration in forests, which, sometimes, is the dominant part in water losses in forests. The Shaoshan forest canopy is of two-layer structure, namely the top-canopy and the sub-canopy. The top-canopy coverage is 82 % and the sub-canopy coverage is about 41 %. It is difficult for Shaoshan forest to simulate the canopy interception losses by using the Gash's analytical model, which is successfully used in temperate and tropical forests. The original Gash model was used to predict the top-cnaopy interception loss and the sparse Gash model was used to simulate the sub-canopy loss for the nature of the original and the sparse Gash models and the coverage and structure of Shaoshan forest.The top-canopy interception loss accounted for about 15.0 % of the annual precipitation and the sub-canopy loss amounted to 9.0 % of the precipitation, indicating that the total interception losses were about 24.0 %. Average evaporation rate from top-canopy layer per ground unit was calcultaed to be 0.79 mm·h-1 and that from sub-canopy was 0.32 mm·h-1 using the Penman-Monteith equation. Top-canopy interception loss was 215.6 mm by the original Gash model with an 17.2 % overestimation and the sub-canopy loss was 118.5 mm with an 7.0 % overestimation. The evaporation from trunks and stems was not signative. Although the analytical interception model was used with worldwide success, the key parameters as evaporation rate and aerodynamic resistance usually were assumed without calculation and measurement and the aerodynamic resistance was assumed to be zero. The aerodynamic resistance was calculated by seven different methods and the...