Review of soil water models with respect to savanna hydrology
Derry, Julian F
Liedloff, Adam C
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Effective management leading towards sustainable rangeland production in arid and semi-arid regions will stem from effective soil water management and comprehension of the hydrological properties of the soil in relation to pastoralism. However, in such areas, there is great complexity of interaction between the soil, climate and vegetation. Highly variable climates can give rise to extended dry periods in which the majority of rain that does fall is lost to surface evaporation. Soil water dynamics are a function of soil physical processes and the competition between plant species and individuals for soil water and space. Spatial distribution of canopy and rooting patterns dictate the outcome of this competition, and the subsequent stability of the vegetation structure, although soil nutrients may be more important in determining vegetation composition. However, rainfall infiltration and the spatial redistribution of runoff water are the predominant factors determining patterns in semi-arid vegetation, with grazing impacts and fire also contributing to the generation and maintenance of spatial heterogeneity. Despite soil water content being the net result of climatic input, soil surface and subterranean characteristics, the extraction of water by plants and it’s return to the atmosphere, the integrated approach needed to comprehend the complete cycle is rarely adopted. Systems models assist us in identifying the gaps in our knowledge by integrating mathematical representations of processes operating at local scales in order to simulate larger scale natural phenomena. However, because of the differences between scientific disciplines, and the bias on investigation that different interests support, true fusion of knowledge is hard to achieve. Hydrologists and ecologists are historically ingrained in their view of soil water dynamics. It is difficult to make comparisons between the approaches taken by hydrologists and ecologists, as they are so dissimilar, despite their mutual aim to predict the water content of the soil profile. This review aims to present these different approaches and identifies the similarities that actually harmonizes them beyond expectation.