ROW: A Field Study of the Role of Simulated Grazing and Time of Establishment on the Growth of a Woody Plant

这项研究的目的是通过实验 评估有助于转换的机制 草原到灌木丛 美国西南部木本植物 在受干扰的草原上定居下来，并成为 补充其他木本植物。 假设的理由 过度放牧、草地竞争减少、缺乏 火灾，气候变化，牲畜传播种子，或 综合因素。 虽然许多这些连续的 已经描述了序列，并且假定了机制， 缺乏支持这些机制的实验证据。 历史上，木本植物被认为是入侵无灌木 多产的草原;但最近被认为是 高度扰动草原的殖民者 部分测试 根据这一假设，将进行一系列田间试验 这是一种木本植物，牧豆树 glandulosa（蜜牧豆树）和半干旱地区的原生草 北美洲西南部的热带稀树草原。 有待检验的假设是， 建立，木本植物和禾本科植物获得资源， 来自不同的根区，两者之间的竞争 大幅减少。 采用竞争实验方法，研究了P. glandulosa和原生草，生长在不同深度的花盆中 将进行。 从统计学上讲，H 0是 在所有的植物中，腺牧豆生物量的减少将是相等的。 治疗（深度），而Ha则是减少量 不等长 如果腺牧豆生物量的减少与 与深度相关，这表明竞争更重要， 在木本植物的建立阶段，当 草和木本植物的根都在同一区域。 一旦木本植物的根延伸到草根区以下， 然后竞争减少。 虽然这个实验非常 由于盆栽实验，如果结果仅 外推到P. glandulosa建立，而不是 建立后的竞争相互作用，实验 能提供有价值的信息

The goal of the proposed research is to experimentally evaluate the mechanisms contributing to the conversion of grasslands to shrubland. Woody species in the southwestern USA become established in disturbed grassland and act as foci for the recruitment of other woody species. The reasons postulated for the conversion are overgrazing, reduced grass competition, lack of fires, changes in climate, spread of seeds by livestock, or a combination of factors. Although many of these successional sequences have been described, and mechanisms postulated, experimental evidence supporting ther mechanisms are lacking. Historically, woody plants were thought to invade shrub-free productive grasslands; but more recently have been thought to be colonizers of highly disturbed grasslands. To partially test this postulate, a series of field experiments will be conducted which deal with competition between a woody increaser, Prosopis glandulosa (honey mesquite) and native grasses of the semi-arid savanna of southwestern North America. The hypothesis to be tested is that after woody plant establishment, the woody plants and the grasses obtain resources from different root zones, and competition between the two is significantly reduced. A competion experiment between P. glandulosa and a native grass, grown in different depth pots will be conducted. Statistically, the H0 would be that the reduction of P. glandulosa biomass would be equal across all treatments (depths), while the Ha would be that the reduction is unequal. If the reduction in P. glandulosa biomass is inversely correlated to depth, it would suggest that competition is more intense during the establishment stage of the woody plant, when both the grasses and woody plants have roots in the same zone. Once the woody plant root extends below the grass root zone, competition then decreases. Although this experiment is very restricted due to pot experiments, if results are only extrapolated to P. glandulosa establishment rather than competitive interactions after establishment, the experiment could offer worthwhile information.