基于Hydrus-1D模型的玉米根系吸水影响因素分析

为探索土壤质地、植物生长状况和气象条件对不同土壤水分条件下根系吸水速率的影响机理，该文以相对根吸水速率与土壤含水率的关系衡量土壤水分有效性，利用Hydrus-1D模型模拟了3种土壤（壤黏土、黏壤土和砂壤土）中不同玉米生长状况（包括叶面积指数、根系深度和根系剖面分布）或蒸发力条件下根系吸水速率随含水率的动态变化，确定了不同条件下根系吸水速率开始降低的临界含水率。结果表明：土壤质地、植物的叶面积指数和根系分布及大气蒸发力都对根系吸水动态曲线的临界含水率有一定影响，其中根系深度和根系分布形状还影响根系吸水速率与含水率关系曲线的形状，但在3种土壤中，根系吸水速率的动态变化对植物生长和大气蒸发力的响应不同。总体而言，3种土壤临界含水率的大小是壤黏土＞黏壤土＞砂壤土；临界含水率随大气蒸发力的升高而升高，随根系深度和深层根系分布的增加而降低；各因子对玉米根系吸水影响程度的大小是土壤质地＞根系分布形状＞根系深度＞大气蒸发力＞叶面积指数。

Analysis of influential factors for maize root water uptake based on Hydrus-1D model

In order to investigate the mechanism of the influence of soil texture, growing state and weather conditions on the root water uptake under various soil moisture conditions, the relationship between root water uptake rate and soil moisture content was used to evaluate soil moisture availability and a Hydrus-1D model was used to analyzed the dynamic changes of root water uptake with various water content with maize growing with different leaf area index, root depth and root density distribution in three soil textural types (loam clay, clay loam and sandy loam) under three weather conditions. Results showed that the root water uptake rate in various conditions remained constant until soil moisture content decreased below a critical value and then declined in a different way under different conditions with further soil moisture depletion. The critical values were different for different soil texture, plant leaf area index and evaporative demand, among which root depth and root density distribution also had significant influence on the relationship between root water uptake and soil moisture content. However, the dynamic change of root water uptake for maize to plant growing state and weather condition was different in the three soils. In general, the critical soil moisture content declined with soil texture in the order: loam clay > clay loam > sandy loam, increased as evaporative demand increasing and decreased as root depth and root density distributed in the deep depth increasing. The effects of various factors on maize root water uptake decreased in the order: soil texture > root density distribution > root depth > evaporative demand > leaf area index.