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

将在几天到几周以及从分米到米的尺度上对资源在空间(斑块)和时间(脉冲)上的异质性进行表征。除了对资源异质性的化学和物理措施外，还将对植物如何感知这种资源变异性进行评估，包括：反映当地资源可获得性的根和叶特征，资源的获取，与其他植物和微生物竞争资源，以及将从斑块和豆类收集的资源转化为适合性和幼苗招募。还将调查植物对资源不协调和可能消除异质性的因素(菌根和根部水分外流)的反应。需要测量的参数包括营养库、通过氮库的通量、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、呼吸作用和生长，以及生物量和种子产量。稳定的同位素将在这项工作中占重要地位，包括新的同位素稀释程序。在解决21个假设中收集的数据也将被应用于生态场理论和克里格法内插法的新的建模应用。这项研究以灌木、多年生草本植物和外来一年生草本植物各两种为特色。还讨论了目前鼠尾草草原从多年生系统到稀有一年生植物的转换。这项研究将对干旱区的一般生态和生态系统功能以及牧地资源的管理具有重要的意义。

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.