毛乌素沙地油蒿群落冠层导度及影响因素  

Temporal variation and controlling factors of canopy conductance in Artemisia ordosica community

作　　者：王珊[1] 查天山[1,2,3] 贾昕[1,2,3] 吴雅娟[1] 白玉洁[1] 冯薇[1,2,3] 

机构地区：[1]北京林业大学水土保持学院 [2]北京林业大学林业生态工程教育部工程研究中心 [3]宁夏盐池毛乌素沙地生态系统国家定位观测研究站

出　　处：《北京林业大学学报》2017年第3期65-73,共9页Journal of Beijing Forestry University

基　　金：国家自然科学基金项目(31670708;31670710;31270755);中央高校基本科研业务费专项资金(2015ZCQ-SB-02)

摘　　要：冠层导度(g_c)是影响植物蒸腾和光合作用的重要参数,对环境变化敏感。本研究利用涡度相关法于2015年5—10月对毛乌素沙地油蒿群落的潜热和显热通量进行连续观测,并同步观测空气温度(T_a)、相对湿度(RH)、光合有效辐射(PAR)、土壤含水量(VWC)、降雨(PP)等气象因子,结合Penman-Monteith的冠层导度逆转方程,了解g_c时间动态与变异机制。结果表明:研究区油蒿群落g_c日变化具有明显的季节差异,夏季(5—8月)g_c达到峰值的时间比秋季(9—10月)早约2 h,约在10:00左右达到峰值,比水汽压亏缺(VPD)和PAR的峰值分别提前3~4 h和1~2 h,秋季g_c在中午12:00达到峰值后直接下降。PAR、VPD均对g_c有显著的调控作用,PAR和VPD对g_c的调控阈值分别是1 200μmol/(m^2·s)和1.5 kPa,小于阈值呈正相关,大于阈值呈负相关。30 cm土壤含水量(VWC_30)是调控g_c的重要因子,当VWC_30大于0.16 m^3/m^3时,g_c与VWC_30呈正线性关系。在高的土壤含水量条件(VWC_30≥0.16 m^3/m^3)下,g_c对PAR和VPD的敏感性高于低土壤含水量(VWC_30<0.16 m^3/m^3)条件。结果表明,土壤水分是调节荒漠生态系统冠层导度的关键因子,研究结果为荒漠生态系统水文过程模型的建立提供重要参考。Canopy conductance（gc） is an important factor influencing plant transpiration and photosynthesis,and it is sensitive to environmental factors. Evapotranspiration and environmental factors of a shrub ecosystem,which was dominated by Artemisia ordosica in northwestern China, were continuously measured using eddy covariance technique in growing season（May-October） in 2015. Meteorological variables including air temperature（Ta）,relative humidity（RH）,photosynthetic active radiation（ PAR）,soil volumetric water content（ VWC）,and precipitation（PP） were also measured. gc was calculated using the inverted Penman-Monteith equation. Diurnal pattern in gc revealed a clear seasonal trend,with gc peaking 2 hours earlier in summer（ from May to August） than autumn（ from September to October）（10： 00,3-4 hours and 1-2 hours before VPD and PAR）. During growing season,gc increased positively with vapor pressure deficit（VPD） and PAR,respectively,saturating at 1. 5 kPa and 1 200 μmol/（ m^2·s）,then decreasing with these variables when greater than their respective threshold.The gc values had positive relationship with soil volumetric water content at 30 cm depth（VWC_30） under high VWC_30（ ≥0. 16 m^3/m^3） during the whole growing season. gc was more responsive to PAR and VPD when VWC30 was high. It was concluded that VWC played a critical role in regulating canopy conductance in desert ecosystems. Our results could potentially provide important baseline information towards hydrological model creation of arid and semi-arid ecosystems.

关 键 词：冠层导度 土壤含水量 半干旱区 蒸腾 光合作用 

分 类 号：S717.193[农业科学—林学]