DISSERTATION RESEARCH: Vegetation structure constraints on ANPP in arid ecosystems: Assessing the meristem limitation hypothesis

虽然年降水量被认为是干旱和半干旱生态系统中植物生产的主要控制因素，但它仅占植物生产年际变化的20-40%。这个博士论文项目是基于这样的假设，即降水确实是一个重要的控制，但有滞后的生态系统响应的变化，降水掩盖了降水生产力的关系。学生将探讨分生组织（植物组织能够分裂，并产生新的器官）的限制，在创建这些滞后的作用与使用被动防雨庇护所和灌溉在新墨西哥州的奇瓦瓦沙漠相结合的降雨量的操纵实验。实验设计创建序列的干旱和潮湿的年份，并将阐明是否有分生组织的限制，是否限制的幅度是成比例的降雨偏差，最后是否以前的干旱年的影响是类似的，但相反的标志的影响潮湿的年份。 该项目的结果将有助于了解气候变化对固碳、初级生产、畜牧生产和灌木入侵过程的影响，这些问题对从养牛场主到关心供水的市政府的每个人都很重要。这些利益攸关方有兴趣了解预期的气候变化（气温升高、降水减少和年际变化增加）对其土地提供其福祉所依赖的生态系统服务的能力的影响。

Although annual precipitation is considered the major control of plant production in arid and semiarid ecosystems it accounts for only 20-40% of the interannual variability of plant production. This doctoral dissertation project is based on the hypothesis that precipitation is indeed an important control but that there are lags in the ecosystem response to changes in precipitation that mask the precipitation-productivity relationship. The student will explore the role of meristem (plant tissue capable of dividing and giving rise to new organs) limitation in creating those lags with a manipulative experiment of incoming precipitation using a combination of passive rainout shelters and irrigation in the Chihuahuan Desert in New Mexico. The experimental design creates sequences of dry and wet years and will elucidate whether there is meristem limitation, whether the magnitude of the limitation is proportional to the rainfall deviation and finally whether the effects of preceding dry years are similar but of opposite sign of the effect of wet years. Results from this project will contribute to the understanding of the effect of climate variability on carbon sequestration, primary production, cattle production and the process of shrub encroachment, issues important to everyone from cattle ranchers to city governments concerned about water supplies. Such stakeholders are interested in understanding the consequences of expected climate change (increased temperature, decreased precipitation, and increased interannual variability) on the ability of their land to provide ecosystem services on which their well-being depends.