Dissertation Research: Spatial Interactions and the Role of Facilitation in a Colorado Desert Plant Community

[9412117] Howe本研究的目的是通过实验验证约书亚树国家纪念地26个物种的7500个木本多年生植物的普查和五年最近调查得出的假设。这些物种大多表现出很强的种内和种间聚集性，且食草性作用未知。实验结果将根据定于1994年3月进行的十年重新人口普查加以解释。通过在优势木本多年生植物周围和附近的开阔区域进行封闭，我们提出区分种内和种间竞争、花岗岩、草食、干燥和促进对两年内新幼苗的建立、生长和/或死亡率的影响，以及对幼苗和已经存在的幼苗的生长和死亡率的影响。通过保护和不保护的幼苗移植，我们希望测试一种不被脊椎动物食草动物啃食的长寿命多年生植物和一种被大野兔啃食的短寿命多年生植物对照样本与一种受中度到重度脊椎动物食草动物啃食的优势灌木标准幼苗的竞争和促进效果。封闭和移植将区分该站点常见的主要多年生木本植物广泛的裸地和聚集的空间分散过程。本论文的研究为荒漠群落空间格局和植物关联的一些重要决定因素提供了一个很好的综合地图数据和实地试验。

9412117 Howe The purpose of this research is to experimentally test hypotheses derived from a census and five-year recensus of 7500 mapped woody perennials of 26 species in Joshua Tree National Monument. Most of these species show strong intraspecific and interspecific aggregation, and herbivory of unknown effect. Experimental results will be interpreted in light of a 10-year re-census, scheduled for March 1994. Using exclosures around members of the dominant woody perennial and in open areas nearby, we propose to distinguish effects of intra- and interspecific competition, granivory, herbivory, desiccation, and facilitation in establishment, growth, and/or mortality of new seedlings over two years, and in growth and mortality of seedlings, and juveniles already present. Using protected and unprotected transplants of seedlings, we expect to test effects of competition and facilitation of controlled samples of a long-lived perennial that is not browsed by vertebrate herbivores, a short-lived perennial that is heavily browsed by jackrabbits, against a standard seedlings of the dominant shrub, which suffer moderate to heavy vertebrate herbivory. Exclosures and transplants will distinguish processes that account for extensive bare ground and aggregated spatial dispersions of key woody perennials common at this site. %%% This dissertation research provides a nice integrate map data from permanent plots with field experiments to assess some of the important determinants of spatial pattern and plant associations in a desert community.