摘要
冠层气孔导度(Gs)是量化气孔在冠层尺度水平上表现的参数,能够表征森林冠层表面水汽和能量交换的动态。本研究利用Granier树干液流测定系统,连续监测华南地区荷木林的树干液流,通过尺度转换和扩展获得冠层蒸腾速率,结合微气象观测值,以Pen-man-Monteith公式计算了Gs,并比较不同土壤水分条件下Gs对水汽压亏缺的响应。结果显示,Gs与气孔气体交换方法实测的叶片气孔导度(gs)日变化相似,单位转换数值大小与实测gs数量级一致。Gs对水汽压亏缺的响应在干季和湿季有明显差别:(1)在土壤水分充足的湿季(土壤含水量θ>33%),Gs对水汽压亏缺的响应更敏感(偏相关系数-0.316),而在干季(θ<23%)则对光合有效辐射的响应更敏感(偏相关系数0.885)。(2)荷木林冠层-大气脱耦联系数(Ω)在湿季接近1,干季则较湿季小,说明湿季叶片的界面层较厚,水汽压亏缺对Gs影响较小,而光合有效辐射是控制Gs的主要环境因子。
Canopy stomatal conductance （Gs） is an important parameter quantifying the stomatal performance at canopy level, being able to characterize the exchange dynamics of vapor and energy of forest canopy. In this paper, the sap flow in a Schima superba stand in southern China was continuously monitored with Granier＇s thermal dissipation probes, and the canopy transpiration of the stand was obtained through data upscaling methodology. In combining with the microclimatic observations, the Gs was estimated by using PenmanMonteith equation, and the responses of the Gs to vapor pressure deficit under different soil water conditions （wet season vs. dry season） were compared. The estimated Gs based on the sap flow measurement was in the same order of magnitude as that of the leaf stomatal conductance （gs） determined by gaseous exchange method, and similar patterns of the diurnal variations of both Gs and gs were observed. The responses of the Gs to vapor pressure deficit in wet and dry seasons had obvious difference. In wet season （soil water content θ〉 33%）, the Gs was more sensitive to vapor pressure deficit （partial coefficient -0.316）; in dry season （θ〈 23%）, the Gs was more sensitive to photosynthetically active radiation （PAR） （partial coefficient 0.885）. The decoupling coefficient （Ω） of stand canopyatmosphere was close to 1 （maximum value） in wet season but substantially smaller in dry season, indicating that vapor pressure deficit had little effects on Gsin wet season probably due to the thicker boundary layers on leaves, while PAR was the main environmental factor controlling Gs.
出处
《生态学杂志》
CAS
CSCD
北大核心
2013年第7期1770-1779,共10页
Chinese Journal of Ecology
基金
国家自然科学基金项目(41030638
31170673
41275169)
广东省自然科学基金项目(S2012020010933)资助
关键词
荷木
树干液流
冠层气孔导度
脱耦联系数
Schima superba
sap flow
canopy stomatal conductance
decoupling coefficient.
