塔里木河下游胡杨林根系吸水模型

Root water uptake model of Populus euphratica in the lower reaches of Tarim River

以塔里木河下游河岸带生长良好具有代表性的胡杨为供试植被,利用土壤水分特征曲线的分形结合胡杨根系分布函数的方法,对根区土壤水分和根长根系吸水关系进行了研究,确定了土壤水分特征曲线和非饱和土壤导水率。根据干旱区胡杨根系分布特征建立了干旱区胡杨二维根长密度函数。所建根长密度函数在根层近地表处服从抛物面分布,而在根层下部服从指数面分布,并基于二维改进的Feddes模型,建立了胡杨根系吸水的二维数学模型。结果表明,春季、夏季、秋季、冬季实验区胡杨根区土壤水分模拟值与实测值的平均误差依次分别为4.0%、7.2%、5.9%、4.9%,均低于10%,得到了较好的模拟效果。这进一步提升了干旱区植物根系吸水模型的模拟精度,为干旱区自然植被耗水量的计算提供了新的方法和科学依据。因此,该二维模型在干旱区植物耗水计算中具有广泛的应用价值和现实意义。

Takingthe representative Populus euphratica as the vegetation samples in the lower reaches of the Tarim River,this paper determined the soil-water characteristic curve and the unsaturated soil hydraulic conductivity according to the meteorological elements,transpiration of P. euphratica,and hydrothermal soil profile parameters at the experimental siteobserved through the automatic weather station,sap flow meters,hydra probe and root sampling method.To study the water uptake by P. euphratica root is of significance for the maintenance and regeneration of P. euphratica and other plants in extremely arid region. Therefore,in this study,the root system distribution of P. euphratica and the soil moisture content in P. euphratica root zone were further analyzed by establishingthe two-dimensional root length density function of P. euphratica based on the distribution characteristics of roots of P. euphratica in arid zone and the modified Feddes model. A good result by comparing the simulation value with observation value was achieved. The comparison results show that the average relative errors between the simulated and observed soil water content are 4.0%,7.2%,5.9% and 4.9% in spring,summer,fall and winter,respectively,less than 10% for all seasons. Established root water absorption model is scientific and plays an important role in soil water and atmospheric water exchange in this paper. The new model further increases the simulation accuracy of plant root water uptake and provides a new method and scientific proof for the calculation of natural vegetation consumption in arid area. Root water quantity calculation accuracy will directly affect the calculation accuracy of the water cycle model. The two-dimensional root water uptake model has important practical significance for water resources management,water use efficiency and biological yield simulation in arid areas.