Collaborative Research: WCR: Ecohydrology of semiarid woodlands: Role of woody plants in the water cycle

0233584斯特恩大面积的半干旱草原和稀树草原已经变成灌木丛。 有一个普遍但未经检验的假设，即减少灌木覆盖将对径流和地下水补给产生切实和大规模的影响。 我们的研究区域是得克萨斯州的爱德华兹高原，那里的杜松覆盖范围很广，山坡由高渗透性和破碎的石灰岩组成。我们的研究将回答有关这些石灰岩山坡上多尺度流动过程的基本问题，并更好地定义灌木控制可能导致的水量增加（如果有的话）。 将在树冠上方进行大面积（3米宽，12米长）降雨模拟，以了解一些降雨情况下的水通量。 在模拟过程中，我们将持续监测地表径流、侧向地下径流、林冠截留、土壤水分和蒸腾作用。 将选择三个地块位置进行模拟实验：一个在陡峭的岩石山坡上，一个在土壤较深的平坦斜坡上，第三个地点在洞穴上方。 洞穴的位置特别重要，因为我们应该能够得到一个很好的估计补给率。 此外，还将在山坡、集水区和集水区范围内进行一系列同位素研究，目的是：（1）区分蒸发和蒸腾造成的土壤水分流失;（2）利用天然存在的锶和氧同位素以及微量元素浓度和比率进行水文线分离（3）确定了灌木对降雨、表层土壤水和深层蓄水的利用。拟议中的研究是一个高度跨学科的考试，并有望成为最全面的考试半干旱灌木林的生态水文学。

0233584SternExtensive areas of semiarid grasslands and savannas have been converted into shrublands. There is a common, but untested, assumption that reducing shrub cover will have tangible and large-scale effects on streamflow and ground water recharge. Our study area is the Edwards Plateau of Texas, where coverage by juniper is extensive and hillslopes are composed of highly permeable and fractured limestone. Our research will answer basic questions about flow processes at multiple scales on these limestone hillslopes and better define how much, if any, of an increased water yield could result from shrub control. Large plot (3 m wide, 12 m long) rainfall simulation will be applied above the tree canopy to develop an understanding of water fluxes for a number of rainfall regimes. During a simulation event, we will continuously monitor overland flow, lateral subsurface flow, canopy interception, soil water, and transpiration. Three plot locations will be selected for simulation experiments: one on a steep rocky hillslope, one on flatter slopes with deeper soils, and a third site above a cavern. The cavern site is especially significant because we should be able to obtain a good estimate of recharge rates. In addition, a series of isotopic studies at the hillslope, catchment and watershed scale will be conducted with the goals of (1) differentiating soil water loss via evaporation versus transpiration (2) conducting hydrograph separation using naturally occurring strontium (Sr) and O isotopes and trace element concentrations and ratios (Sr/Ca and Mg/Ca), and (3) determining shrub water use of rainfall, surficial soil water, and deep storage, both seasonally and spatially. The proposed study is a highly interdisciplinary examination and promises to be the most comprehensive examination of the ecohydrology of semiarid scrublands.