| Plantation has been increasingly important in soil and water conservation, and carbon fixing under the background of natural forest area reduced and global warming. Consequently, studies of plantation carbon sinks,and soil and water conservation based on plantation productivity and biomass have been a new hotspot. The evaporation and transpiration per unit area increase with tree growth and productivity after planting a few years. Plantation carbon sinks and carbon source are determined by productivity, biomass, the decomposition and accumulation of litter. Plantation productivity, biomass and litter are affected by distribution pattern, planting density and seeding size inequality. An effective thinning can not only improve plantation environment, but it also promote the growth of plantation individuals and communities.Therefore, we use the computer simulation to study the effect of different planting methods (distribution pattern, planting density, the seeding size inequality) and thinning (the beginning time of thinning, thinning intensity) on plantation productivity, biomass and litter. We also analyze the changes of carbon sinks, vegetation restoration processes and forestland evapotranspiration. The simulation results showed:(1) Plantation productivity, standing biomass and accumulated biomass under uniform distribution were more than under random distribution. Therefore, uniform distribution pattern is more appropriate than random distribution;(2) Although plantation productivity increased with planting density, standing and accumulated biomass did not show a simple increseaing trend with planting density. Moreover, litter increased gradually with planting increasing density. Consequently, it is not true that largest planting density is the best.(3) Seeding size inequality played an important role under uniform distribution but not random distribution. The role of seeding size inequality under uniform distribution decreased with planting density. Therefore, the role of seeding size inequality was limited by distribution pattern and planting density. The thinning simulation results showed:(1) Appropriate beginning time of thinning and thinning intensity could not only improve the productivity, standing and accumulated biomass, and plantation carbon sinks, but it could also alleviated the contradiction between forest evapotranspiration and vegetation restoration progresses.(2) Computer simulation approach was an effective method to determine the beginning time of thinning and thinning intensity. The beginning time of thinning could be determined by simulating the time of self-thinning without thinning. The initial density which did not lead to self-thinning by simulatiuon and frequency of thining could be used to determine the thinning intensity.Consequently, we conclude that planting method and thinning play an important role in plantation productivity and carbon sinks. Computer simulation is an effective method to determine appropriate planting and thinning method. |
