Data from: Landscape pivot points and responses to water balance in national parks of the southwest U.S.

1. A recent drying trend that is expected to continue in the southwestern U.S. underscores the need for site-specific and near real-time understanding of vegetation vulnerability so that land management actions can be implemented at the right time and place. 2. We related the annual integrated normalized difference vegetation index (iNDVI), a proxy for vegetation production, to water balance across landscapes of the Colorado Plateau. We determined how changes in production per unit of water (vegetation responses), and the water balance amounts at which production shifted from above to below average values (pivot points), varied across dominant vegetation and soil types. 3. Precipitation (PRCP), actual evapotranspiration (AET), water deficit (D), and soil moisture (SM) explained 13 – 82% of variation in vegetation production. Along an increasing water availability gradient, vegetation responses to PRCP and AET increased, responses to SM decreased, and responses to D became more negative. We found tradeoffs between vegetation responses and pivot points within and across all vegetation types that were mediated by soil properties. 4. Synthesis and applications. The water needed by native vegetation to maintain production depends on plant traits. The water available to vegetation depends on climate and soil properties that change along environmental gradients. Tracking this biologically-relevant water availability in relation to water need provides an indicator of vegetation growth or stress that can help guide the time and place for management actions.

1. 美国西南部近期出现且预计将持续的干旱化趋势，凸显了针对特定场地开展近实时植被脆弱性评估的迫切需求，从而能够在适宜的时机与地点落实土地管理行动。2. 本研究将表征植被生产力的替代指标——年度整合归一化差值植被指数（integrated Normalized Difference Vegetation Index, iNDVI），与科罗拉多高原（Colorado Plateau）各景观的水量平衡进行关联分析。本研究明确了：单位水量对应的生产力变化（即植被响应），以及生产力从高于平均值转为低于平均值的水量平衡阈值（枢轴点（pivot points））在不同优势植被与土壤类型间的差异。3. 降水（Precipitation, PRCP）、实际蒸散发（Actual Evapotranspiration, AET）、水分亏缺（Water Deficit, D）与土壤水分（Soil Moisture, SM）可解释13%至82%的植被生产力变异。随着水分可利用性梯度升高，植被对PRCP与AET的响应增强，对SM的响应减弱，而对D的响应则愈发负向。本研究发现，在所有植被类型内部及跨植被类型之间，植被响应与枢轴点（pivot points）之间存在权衡关系，且该关系受土壤属性调控。4. 综合与应用。本土植被维持生产力所需的水量取决于植物性状。植被可利用的水量则取决于随环境梯度变化的气候与土壤属性。追踪与水分需求相关的、具有生物学意义的水分可利用性，可作为植被生长或胁迫状态的指示因子，从而辅助确定土地管理行动的适宜时机与地点。