地下变水位条件下塔里木河下游河岸胡杨林蒸腾模型

Transpiration model of Populous euphratica in the lower reaches of Tarim River under groundwater fluctuation

选择在塔里木河下游普遍生长的胡杨林(Populus euphratica)为供试植被(3种不同大小胡杨),以大气温度、太阳净辐射、大气相对湿度、冠层顶风速、地下水位和胡杨树茎横截面积等6个影响因子作为影响胡杨林蒸腾量的自变量,基于最小二乘法建立了多元线性回归模型与非线性模型相结合的多元非线性回归耦合模型,并应用模型对地下变水位条件下塔里木河下游河岸胡杨林的耗水过程分别进行了时尺度和日尺度上的模拟研究。结果表明:在日内变化(时尺度)方面,大气温度、相对湿度、辐射、地下水位和树茎横截面积等5个因子是影响胡杨林蒸腾量的主要因素,在不同地下水位条件(Hg=1.0 m、1.2 m、2.5 m、3.0 m)条件下,胡杨蒸腾量观测与模拟的平均确定系数分别为0.69、0.87、0.82和0.88;而在日均变化(日尺度)方面,大气温度、地下水位和树茎横截面积等3个因子是影响胡杨林蒸腾量的主要因素,胡杨林的蒸腾量观测值与模拟值表现出较好的相关性,其确定系数与决定系数分别为R=0.73、R2=0.532,平均相对误差为19.6%,其显著性水平均通过p=0.05,表现出较好的拟合性。总之,模拟结果与试验观测结果比较吻合,该回归耦合模型具有使用简便、影响因子易测定,能够更好刻画植被腾发量的复杂非线性特性,为干旱区自然植被耗水量的估算提供了计算方法和科学依据。

The article taking the representative natural vegetation （populus euphratica） in the lower reaches of Tarim River as the test vegetation, the air temperature, net solar radiation, atmospheric humidity, wind speed on the canopy top edge, groundwater level and cross sectional area of the populus euphratica, as an initial influence factors of model based on the field test. Multiple linear regression models and multiple nonlinear regression models were es- tablished based on the least square method, transpiration of the populous euphratica in the lower reaches of Tarim River was simulated by using the model under groundwater fluctuation. Results showed that In terms of hours scale： the air temperature, net solar radiation, atmospheric humidity, groundwater level and cross sectional areas of the populus euphratica are the main factors affecting the transpiration of populus euphratica forest. The coefficients of determination of observed and simulated hourly values are 0.69,0.87,0.82 and 0.88 for the 1.0, 1.2,2.5 and 3.0 m groundwater depths, respectively. In terms of days scale： the air temperature, groundwater level and cross sectional areas of the populus euphratica are the main factors affecting the transpiration of populus euphratica forest. The coef- ficient of correlation and determination between observed and simulated transpiration are 0.73 and 0.53. The average relative error of simulated value with observed value for transpiration is 26.1%. Significance level reached p=0.05, consequently, the coupled model test against experimental data shows a good agreement between observed and simu- lated transpiration of the populous euphratica. The simulated results showed that the prediction precision of the mod- el is high than other conventional model. This model provides a new method and scientific proof for the calculation of natural vegetation consumption in arid area.