Mechanisms of Below-Ground Resource Acquisition in Plants: Linking Form and Function

本研究的目的是了解植物细根结构和对养分斑块的动态响应的差异如何影响它们获取土壤资源特别是氮的能力。总体假设是细根形态（长度、宽度、根毛的产生）和生产(出生、死亡、以及伸长率)将决定物种遇到和利用在空间和时间上变化的土壤资源的比率（即它们的觅食能力）。以往的研究表明，一年生植物和多年生植物对土壤养分的响应存在差异。这导致了一种假设，即在演替田中，多年生植物取代一年生植物的部分原因可能是随着时间的推移，土壤资源的斑块性增加，而一年生植物和多年生植物发现和利用这些斑块的能力存在差异。特别令人感兴趣的是对营养斑块的反应时间，这将通过测量物种的人口反应来确定。几个具体的假设将在温室和田间试验中进行检验。通过改变氮的分布，以15n为示踪剂，测定细根形态与动态和资源获取的关系。细根动态（分支、生长、出生和死亡）将通过视频技术就地测量。这项技术可以跟踪单个根系对营养斑块的反应，并与地下形态、生长和获取土壤资源能力的物种差异有关。这些研究结果将有助于对植物获取土壤资源的机制有更深入的了解，并有助于更好地了解资源竞争如何影响陆生植物群落的物种分布。

The objective of the proposed research is to understand how differences among plant species in fine root structure and dynamics in response to nutrient patches affects their ability to acquire soil resources particularly nitrogen. The overall hypothesis is that differences in fine root morphology (length, width, production of root hairs) and production (birth, death, and elongation rate) will determine the rate at which species can encounter and exploit soil resources that vary in space and time (i.e. their foraging ability). Previous work suggests there are difference among annuals and perennials in response to soil nutrients. this has led to the hypothesis that the replacement of annuals by perennials in successional fields may be partially due to the increased patchiness in soil resources over time and difference in the abilities of annuals and perennials to find and exploit these patches. Of particular interest is the timing of responses to nutrient patches which will be determined by measuring the demographic response of species. Several specific hypothesis will be tested in greenhouse and field experiments. By varying the distributions of nitrogen, and using 15 N as a tracer, the relationship between fine root morphology and dynamics and resource acquisition will be measured. Fine root dynamics (branching, growth, birth and mortality) will be measured in situ with video technology. This technology allows the response of individual roots to nutrient patches to be followed and related to species differences in below-ground morphology, growth, and ability to acquire soil resources. The results of these studies will contribute to the development of a more mechanistic understanding of soil resource acquisition by plants and to a better understanding of how competition for resources affects species distributions in terrestrial plant communities.