柴达木地区沙棘冠层导度特征及模拟

为了揭示沙棘冠层导度对环境因子的响应规律,评价Jarvis模型在沙棘冠层尺度上的适用性,利用Granier热消散式探针连续测定了青海省柴达木盆地实验站内的沙棘灌丛树干液流,并同步观测气象因子,利用Penman-Monteith方程反推方法,获得了长期连续的冠层导度。在分析沙棘冠层导度动态变化规律的基础上,采用十字交叉法对Jarvis模型进行参数率定和误差分析。结果表明:研究区沙棘冠层导度日变化呈“单峰型”曲线,冠层导度随饱和水汽压差的增加呈负指数关系下降,并与太阳辐射强度呈正相关。基于饱和水汽压差、太阳辐射强度和气温这3个环境变量的Jarvis模型可解释gc变化的81%,且最低相对误差仅11.01%。环境因子对冠层导度(gc)模型精度的影响依次为饱和水汽压差(VPD)>太阳辐射强度(Rs)>气温(T)。 

Characteristics and simulation of the canopy conductance of Hippophae rhamnoides in Qaidam Region of northwestern China

The aim of this study was to explain the response of canopy conductance of sea buckthorn ( Hippophae rhamnoides ) to different environmental conditions so as to evaluate the feasibility of application of Jarvis model in sea buckthorn at the canopy scale. By using Granier’ s thermal dissipation probe, the sap flow of sea buckthorn in Qaidam Basin in Qinghai Province, northwestern China was continuously measured,and as well,the environmental factors such as incoming solar radiation intensity (Rs), air temperature (T), relative humidity (RH), wind speed (u) and rainfall were synchronically measured. Based on sap flow, canopy conductance ( gc ) was continuously simulated by back-calculated Penman-Monteith model. By analysis of gc of sea buckthorn, Jarvis stomatal model was simulated and analyzed with cross-validation. The results indicated that the diurnal variation in canopy conductance of sea buckthorn showed a single-peaked curve. There was a negative logarithm relationship between canopy conductance and vapor pressure deficit (ⅤPD ) under different radiation conditions. And the canopy conductance had a positive relationship with solar radiation intensity. The three variables, ⅤPD, T and Rs, explained 81% of the variation in conductance in Jarvis-type mode, with the lowest average relative error of only 11. 01%. And the degree of the environmental factors affecting the simulation accuracy of the model is ranked as ⅤPD>Rs>T.