摘要
考虑植物阴叶和阳叶对环境的反应、植物叶片丛聚特性以及叶片氮素水平的垂直差异,建立了黑云杉林与大气之间物质输送和能量交换的一维完全多层模式。模式中对阳叶和阴叶的叶面积指数借用Chen J M等提出的方法,并经过修改以适用于多层模拟。叶水平的光合作用c运用Farq uhar方程并与CO2传导方程联列获得。模式验证的资料取自BOREAS(Boreal Ecosystem-fAtmosphere Study)研究计划中加拿大Saskatchewan的南试验区,属于温带气候。通过对冠o层上方的显热、感热和CO2通量、以及植物光合作用、蒸腾作用和气孔传导等生理作用t过程的实测值进行了计算结果的验证,结果表明:计算的显热通量比实测值偏低,潜热通量则略高于实测值,而CO2通量只有在较高水平时偏高,3个通量的计算值与实测值比较接近,R2分别为0.71,0.78和0.65,取得了较好的效果。气孔导度、光合作用和蒸腾作用的模拟结果表明,三者的实测与模拟值之间的R2分别达到0.57,0.69和0.66,均通过0.01显著度检验,且无显著的系统偏差。因此,可以认为在多层模拟中充分考虑叶片不同受光状况,不同氮素水平以及叶片丛聚特性的影响有助于更好地研究植被与大气的交换过程。
A complete multilayer model of vegetation-atmosphere ex spruce stand, taking into account response of sunlit and shaded change has been developed for a boreal black leaves to ambient conditions respectively, leaf clumping and nitrogen level in the leaves at different layers. The established model consists of one dimensional air diffuse meteorological equation for transfer of water, heat, CO2 within and above the forest canopy, a twoleaf submodel for leaf-air exchange, and an exponential function for distribution of nitrogen level in leaves with height of canopy. Estimation of sunlit and shaded leaf area index was borrowed from Chen＇s method, modified for layer-by-layer by the authors of this paper. Photosynthesis at leaf level was computed by combining Farquhar＇s equations and CO2 conductance equation. Soil temperature, moisture, and thermal and water fluxes between adjacent soil layers, obtained from ESES, were used for calculating exchanges of radiation, latent and sensible heat between soil surface and its immediately overlying canopy air. Data for model validation came from a southern study area （53° 59＇ N, 105° 07＇ W） of BOREAS （Boreal Ecosystem-Atmosphere Study） located in Saskatchewan, Canada and beloging to temperate climatic zone. The involved data, just covering main growing season in 1994, were sensible heat flux, latent heat flux, CO2 flux which were all measured by eddy correlation method, and soil heat flux measured by thermal flow plate, CO2 concentration profile by LI 6262 IRGA, net radiation and other regular meteorological elements such as air temperature, humidity, wind speed, and air pressure. Measurements of leaf photosynthesis, transpiration and stomata conductivity to CO2 were made by LI6200 portable photosynthesis system. The validation for physiological progresses of the leaf stomata conductance, photosynthesis and transpiration shows that there were good agreements and no marked systematic discrepancies between the measurements and the estimates. The flux modeling indicates that sensible heat fluxes were slightly overestimated in comparison with observed ones, and between them a squared correlation coefficient （R2） amounted to 0.71 but the difference fluctuated from time to time. In contrast to the sensible heat flux, estimates of latent thermal flux were a little lower than observed ones and R2 reached 0.78. CO2 flux simulation had the lowest R^2 of 0.65 and slightly underestimated when it goes over 7μmol/（m^2. s）. CO2 concentration was of the biggest R^2 of 0.90 although there were larger errors in the canopy air close to the forest floor, rising from omitting moss respiration. Analysis of these flux simulations leads to conclude that the complete multilayer model of vegetation-atmosphereresented achieves good results and is helpful to better investigation into vegetationtmo- sphere exchange process because of its well dealing with the leaf radiance absorption, nitrogen level and clumpinst.
出处
《气象学报》
CAS
CSCD
北大核心
2005年第6期969-979,共11页
Acta Meteorologica Sinica
基金
国家自然科学基金项目(B29200)
关键词
黑云杉
CO2通量
完全多层模式
二叶模型
叶片丛聚
CO2 flux, Complete multiplayer model, Two-leaf submodel, Leaf clumping, Black spruce
