早竹林生态系统湍流动态特性的研究

A STUDY OF TURBULENT DYNAMICS OF A BAMBOO (PHYLLOSTACHYS PRAECOX) ECOSYSTEM

Based on the theory of ecoboundary system, the authors considered the dense canopy of a bamboo stand as a "ecological body" working as a unit, the interface layers between the canopy and its surrounding as an ecoboundary system complex and the distributional density of leaves and branches within the canopy as a compositional structure of the "ecological body". All these play an important role collectively in material exchange and energy flow of a bamboo ecosystem. The turbilent fluxes are calculated by using the method of aerial dynamics in the atmospheric boundary layer. The results obtained indicate that, after sunrise, the upper part of the canopy is heated first, so the heat transfer is downward from the upper part of the canopy. It is also influenced by the temperature inversion layer near the floor, which causes the weak upward flux from the inversion layer to the lower part of the canopy and downward flux to the floor. At the pick of photosynthesis in the morning about 10 a. m. the canopy serves as a sink of CO2 which comes from the atmosphere above the upper ecoboundary of the canopy and from the respiration of soil underneath; while at the "nap" period of photosynthesis at 2 p. m. the canopy becomes the source of CO2, the excess CO2 mainly goes downward. The transpiration of bamboo leaves and branches is very active in the afternoon. Water vapor and CO2 fluxes are 1-3 times greater than those in the morning, and heat flux even greater than before. In addition, the turbulence is always developed after 11 a. m. outside the forest and gradually disappears after 4 p. m.; while within the forest, turbulence can not be developed all day long except at those moments when the thunder storm occurs.