Spatial and Temporal Heterogeneity of Resource Availability in the Sagebrush-steppe Ecosystem: Perception and Exploitation by Plants

将在天到周和分米到米的尺度上描述资源在空间（斑块）和时间（脉冲）上的异质性。除了对资源异质性进行化学和物理测量外，还将对植物如何感知这种资源可变性进行评估，包括：根系和叶片特征反映了当地资源的可用性、资源的获取、与其他植物和微生物对资源的竞争，以及从斑块和豆类中收集的资源转化为适合度和幼苗招募。植物对资源不一致性的反应和可能平滑异质性的因素（菌根和根部的水分流出）也将进行研究。要测量的参数包括养分库、氮库通量率、微生物生物量、土壤水势、植物养分获取、光合作用、根系吸收动力学、呼吸和生长、生物量和种子产量。稳定同位素将在工作中占据突出地位，包括新的同位素稀释程序。在21个假设中收集的数据也将用于生态场理论和克里格插值的新建模应用。本研究以灌木、多年生禾本科和外来一年生禾本科两种植物为研究对象。本文还讨论了目前山艾草草原从多年生系统向外来一年生系统的转变。该研究将对干旱区总体生态学和生态系统功能的研究以及放牧资源的管理具有重要意义。

Characterization of resource heterogeneity in space (patches) and time (pulses) at scales of days to weeks and decimeters to meters will be undertaken. In addition to chemical and physical measures of resource heterogeneity, assessments of how this resource variability is perceived by plants will be pursued, including: Root and foliage characteristics that reflect local resource availability, acquisition of resources, competition with other plants and microbes for resources, and translation of resources gleaned from patches and pulses into fitness and seedling recruitment. Plant response to incongruity of resources and factors that might smoothe heterogeneity (mycorrhizae and water efflux from roots) will also be investigated. Parameters to be measured include nutrient pools, flux rates through nitrogen pools, microbial biomass, soil water potential, plant nutrient acquisition, photosynthesis, root uptake kinetics, respiration and growth, and biomass and seed production. Stable isotopes will feature prominently in the work including new isotopic dilution procedures. Data collected in addressing 21 hypotheses will also be applied in a new modeling application of Ecological Field Theory and kriging interpolation. The study features two species each of shrubs, perennial grasses and exotic annual grasses. The current conversion of the sagebrush steppe from a perennial system to exotic annuals is also addressed. This research will produce findings of importance to the general ecology and ecosystem function of arid lands as well as to the management of grazing land resources.