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华南荷木林冠层气孔导度对水汽压亏缺的响应

曹庆平1,2,赵平1**,倪广艳1,朱丽薇1,牛俊峰1,曾小平1   

  1. 1中国科学院华南植物园, 广州 510650; 2中国科学院大学, 北京 100049)
  • 出版日期:2013-07-10 发布日期:2013-07-10

Responses of canopy stomatal conductance of Schima superba stand to vapor pressure deficient in southern China.

CAO Qing-ping1,2, ZHAO Ping1**, NI Guang-yan1, ZHU Li-wei1, NIU Jun-feng1, ZENG Xiao-ping1     

  1. (1South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650; 2University of Chinese Academy of Sciences, Beijing 100049)
  • Online:2013-07-10 Published:2013-07-10

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Penman-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。

关键词: 生物学特征, 时空分布, 莱州湾, 三疣梭子蟹, 环境因子

Abstract: 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 PenmanMonteith 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 canopyatmosphere was close to 1 (maximum value) in wet season but substantially smaller in dry season, indicating that vapor pressure deficit had little effects on Gs in wet season probably due to the thicker boundary layers on leaves, while PAR was the main environmental factor controlling Gs.

Key words: temporal and spatial distribution, environmental factors, Portunus trituberculatus, biological characteristics, Laizhou Bay.