CAREER: An ecohydrological framework for understanding land degradation in dryland ecosystems

职业：了解旱地生态系统土地退化的生态水文学框架

• 批准号: 0847368
• 负责人: Kelly Caylor
• 金额: $ 150万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-15 至 2014-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0847368&HistoricalAwards=false
• 关键词: CAREER; ecohydrological; framework; understanding; land

This proposal will provide a novel perspective regarding how factors that impact dryland vegetation structure govern spatial and temporal patterns of plant water use and water use efficiency from individual to landscape scales. To accomplish this goal, an ecohydrological observatory will be created at the Princeton-affiliated Mpala Research Centre & Conservancy (MRCC), located in the Laikipia District of central Kenya. The observatory will be capable of resolving landscape-scale evaporation and transpiration separately using an integrated off-axis cavity spectrometer (ICOS) to measure the isotopic composition of water vapor fluxes between the land surface and the atmosphere. Prior calibration and validation activities have demonstrated the utility of this sensor for E/T partitioning, and the possibility of direct flux characterization using ICOS laser absorption methods at sampling frequencies of 0.5 Hz.Three specific hypotheses form the heart of the research and educational plans: (1) The structural/functional organization of water-limited vegetation may be described according to a constrained optimization that seeks to both maximize water use (maintain high transpiration) and also minimize water stress (prevent low water use efficiency) across a range of scales and settings; (2) Ecosystem-scale functional diversity in plant water use and water use efficiency (e.g. differing tree/grass water use in time and space) are critical to the maintenance of ecological and hydrological function in dryland ecosystems; and (3) Shifts in the relative magnitude of various water balance components (e.g. transpiration/ evaporation) may be used as diagnostic signatures of land degradation in dryland ecosystems. To address these hypotheses, the proposed research program will combine continuous ecohydrological measurements at a core site with simultaneous intensive shorter-term observations in both managed and experimentally manipulated plots. The combination of continuous data as well as targeted measurements will allow for direct tests of ecosystem response to water availability in landscapes differentially impacted by herbivory and land use intensity. The results of this research provide a unique quantitative framework for the development of land use strategies that seek to prevent land degradation and sustain pastoralist societies that depend on dryland ecosystems.

这一提议将提供一个新的视角，探讨影响旱地植被结构的因素如何支配植物用水的时空格局和从个体到景观尺度的用水效率。为了实现这一目标，将在 位于肯尼亚中部莱基皮亚区的肯尼亚附属姆帕拉研究中心保护协会（MRCC）。该观测站将能够使用一个综合离轴腔光谱仪来测量陆地表面和大气之间的水蒸气通量的同位素组成，从而分别解决蒸发和蒸腾的问题。先前的校准和验证活动已经证明了该传感器用于E/T划分的实用性，以及在0.5 Hz的采样频率下使用ICOS激光吸收方法进行直接通量表征的可能性。三个具体假设构成了研究和教育计划的核心：（1）水的结构/功能组织-有限的植被可以根据约束优化来描述，该约束优化寻求最大化水利用，（保持高蒸腾），并尽量减少水分胁迫（防止水利用效率低下）;（2）植物水分利用和水分利用效率的生态系统规模功能多样性（如树木/草地在时间和空间上的不同用水）对维持旱地生态系统的生态和水文功能至关重要;（3）各种水平衡组成部分（如蒸腾/蒸发）的相对幅度的变化可用作旱地生态系统土地退化的诊断标志。为了解决这些假设，拟议的研究计划将结合联合收割机连续生态水文测量在一个核心网站，同时密集的短期观测管理和实验操作的地块。连续的数据以及有针对性的测量相结合，将允许直接测试生态系统对水的可用性在不同的影响，草食动物和土地利用强度的景观。这项研究的结果为制定土地利用战略提供了一个独特的量化框架，这些战略力求防止土地退化，维持依赖旱地生态系统的畜牧社会。