Demographics of E. californica and exotic grass species in the San Joaquin Desert: a field survey and greenhouse experiment

Shrubs facilitate the abundance and productive of annual plants in desert ecosystems.However, these shrub microhabitats favour plant species with competitive life histories. Ephedra californica is a dominant shrub in the San Joaquin desert that has been identified as a facilitator. Here, we explore the factors that limit the Ephedra californica recruitment into the San Joaquin desert including substrate, water availability, and herbivory. We also explore the role of the invasive grass Bromus madritensis on limiting establishment of E. californica. Vegetation surveys were conducted in the field during 2013 and collected seed was then used to conduct two greenhouse trials. The first explore germination and establishment techniques for E. california and the optimal substrate. The second examined E. californica establishment in present of the invasive B. madritensis responding to different water levels and herbivory. These results can have implications for land managers in the San Joaquin Valley to maintain native shrub biodiversity in the region.The study available with further details of methods and results can be found in Applied Vegetation Science荒漠生态系统中，灌木可促进一年生植物的种群丰度与生产力。然而，这类灌木微生境更青睐具有竞争型生活史策略的植物物种。加州麻黄（Ephedra californica）是圣华金荒漠（San Joaquin desert）的优势灌木，已被证实为促进物种。本研究旨在探究限制加州麻黄在圣华金荒漠定植的各类因素，包括基质条件、水分有效性与植食性压力；同时还探讨了入侵禾草马德里雀麦（Bromus madritensis）对加州麻黄定植的限制作用。研究团队于2013年开展野外植被调查，并将采集得到的种子用于开展两项温室试验：第一项试验旨在明确加州麻黄的萌发与定植技术，以及其最适生长基质；第二项试验则针对不同水分梯度与植食性压力条件，探究入侵种马德里雀麦存在时加州麻黄的定植情况。本研究结果可为圣华金谷的土地管理者维护区域原生灌木生物多样性提供参考。有关本研究方法与结果的更多细节，可查阅《Applied Vegetation Science》期刊。