Dissertation Research: The influence of rainfall pulses and disturbance on the invasion of coastal sage scrub

气候变化模型预测，在中纬度地区，降雨量将增加，风暴频率将减少。这些变化可能会强烈影响外来物种是否可以入侵原生栖息地，特别是在同时受到干扰的系统中。在半干旱的沿海鼠尾草灌丛（CSS），外来的一年生草威胁着高度多样化的本地社区。此外，火灾干扰的频率正在增加。拟议的研究将测试预测，较大的，不太频繁的降雨事件增加火灾后的本地灌木的相对竞争力，减缓转换CSS每年异国情调的草地。 这些规模更大、频率更低的事件应该有利于像灌木这样根系更深、对干旱期有更大耐受力的物种。为了测试这些预测，将在燃烧和未燃烧的CSS中操纵降雨分布（增加事件大小和降低频率）。种植CSS、草或竞争性混合物的子区将用于评估降雨控制下物种的相对表现。对物种土壤水分需求的温室测量将补充实地实验，为生态理论提供强有力的检验，并为预测群落对多种全球变化因素的反应奠定基础。研究结果将被用来通知CSS和其他系统的保护和恢复决策受到入侵压力的增加，改变干扰制度，并改变降水模式。除了影响自然区域管理，该项目将通过独立研究培训本科生，并通过会议，演讲和出版物提高社区意识。

Climate change models predict that, in mid-latitude regions, rainfall event size will increase and storm frequency will decrease. These changes may strongly influence whether exotic species can invade native habitats, particularly in systems that are simultaneously impacted by disturbance. In semi-arid coastal sage scrub (CSS), exotic annual grasses threaten the highly diverse native community. In addition, fire disturbance is increasing in frequency. The proposed research will test the prediction that larger, less frequent, rainfall events increase the relative competitive ability of the native shrubs after fire, slowing the conversion of CSS to annual exotic grassland. These larger, less frequent events should favor species like the shrubs with deeper roots and greater tolerance to dry periods. To test these predictions, rainfall distribution will be manipulated (increasing event size and decreasing frequency) in burned and unburned CSS. Subplots planted with CSS, grasses, or a competitive mixture will be used to evaluate species' relative performance under the rainfall manipulations. Greenhouse measurements of species' soil moisture requirements will supplement field experiments to provide a strong test of ecological theory and a base for predictions of community response to multiple global change factors. The results will be used to inform conservation and restoration decisions in CSS and other systems subjected to increased invasion pressure, altered disturbance regimes, and changed precipitation patterns. In addition to influencing natural area management, the project will train undergraduate students though independent research and promote community awareness through meetings, presentations, and publications.