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Modeling soil-root water transport and competition for single and mixed crops

机译：模拟单一和混合作物的土壤根水运移和竞争

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摘要

Root water potential dynamics and water uptake partitioning were compared between single crops and intercrops, using a simulation model. Four root maps having 498, 364, 431 and 431 soil-root contacts were used. In the first and second cases, singlecrops with 'deep' and 'surface' roots were considered, whereas in the third and fourth cases, roots of two mixed crops were simultaneously considered with different row spacing (40 and 60 cm). Two soils corresponding to a clay and a silty clay loam wereused in the calculations. A total maximum evapotranspiration of 6 mm d-1 for both single or mixed crops was considered, for the mixed crops however, two transpiration distributions between the crops were analysed (3:3 mm/d, or 4:2 mm/d for each crop, respectively). The model was based on a previous theoretical framework applied to single or intercropped plants having spatially distributed roots in a two-dimensional domain. Although water stress occurred more rapidly in the loam than in the clay, due tothe rapid decrease of the soil water reserve in the loam, the role of the root arrangement appeared to be crucial for water availability. Interactions between the distribution of transpiration among mixed crops and the architecture of the root systems which were in competition led to water movements from zones with one plant to another, or vice versa, which corresponded to specific competition or facilitation effects. Decreasing the distances between roots may increase competition for water, although itmay determine greater water potential gradients in the soil that increase lateral or vertical water fluxes in the soil profile. The effects of the root competition on water uptake were quite complicated, depending on both environmental conditions, soilhydrodynamic properties, and time scales. Although some biological adaptive mechanisms were disregarded in the analysis, the physically 2-D based model may be considered as a tool to study the exploitation of environmental heterogeneity at microsite scales.
机译：使用模拟模型比较了单作和间作之间的根系水势动态和水分吸收分配。使用了四个具有498、364、431和431土壤-根接触的根图。在第一种和第二种情况下，考虑具有“深”和“表层”根的单作，而在第三种和第四种情况下，同时考虑两种混合作物的根，行距不同（40和60 cm）。计算中使用了对应于粘土和粉质粘土壤土的两种土壤。单个或混合作物的最大蒸散量被认为是6 mm d-1，但是对于混合作物，分析了两个作物之间的蒸腾量分布（3：3 mm / d或每个4：2 mm / d分别）。该模型基于先前的理论框架，该理论框架适用于在二维域中具有空间分布根的单个或间作植物。尽管在壤土中水分胁迫比在粘土中发生更快，但由于壤土中土壤水分储备的迅速减少，根系排列的作用似乎对水分利用至关重要。混合作物之间蒸腾作用的分布与竞争中的根系结构之间的相互作用导致水分从一种植物生长到另一种植物的运动，反之亦然，这对应于特定的竞争或促进作用。减小根部之间的距离可能会增加对水的竞争，尽管这可能会确定土壤中较大的水势梯度，从而增加土壤剖面中的横向或垂直水通量。根系竞争对水分吸收的影响非常复杂，这取决于环境条件，土壤水动力特性和时间尺度。尽管在分析中没有考虑某些生物学适应机制，但是基于物理二维的模型仍可被视为研究在微场所尺度上利用环境异质性的工具。

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