Tests of the Equiv#aence of Competitors and Asymmetry of Competition Hypotheses in Multispecies Woody Communities

尽管竞争在生态学理论中具有核心重要性，但对植物竞争假说的实地测试却很少。目前的两个主要假说是竞争对等假说和不对称竞争假说。还没有人尝试将这些假说应用于木本植物群落。P.I.提出的实验将检验竞争等价性假说和不对称竞争假说，使用白桦和大叶水杉的个体。这项研究基于三个工作假设：1)地上对光的竞争与地下对土壤资源的竞争对幼苗的生长和存活具有同等或更大的重要性。这是其余两个假设的基本假设。2)不同树种大小相近的相邻树种的密度相同时，目标苗的反应也是一样的。这就是竞争性对等假说。3)目标苗的生长减慢与不同大小邻居等密度的大小成正比。这是不对称竞争假说的零形式。研究人员将在中心目标个体周围创建重复的社区，方法是将现有的高密度区域变薄，以留下所需密度、物种和大小的邻居。目标苗木的响应将被测量为树高和茎粗的生长，并分析为相对生长速率。反应将在治疗后的两年内进行评估。结果将决定上述假设是否准确地描述了这些木本植物之间的竞争相互作用，以及这些物种之间的竞争效应是如何不同的。

Despite the central importance of competition in ecological theory, field tests of hypotheses about plant competition are rare. Two current major hypotheses are the Competitive Equivalence Hypothesis and the Asymmetrical Competition Hypothesis. No attempts have been made to apply these hypotheses to woody plant communities. The P.I.s propose experiments that will test both the Competitive Equivalence Hypothesis and the Asymmetrical Competition Hypothesis using individuals of Betula alleghaniensis and Fagus grandifolia. The proposed research is based on three working hypotheses: 1) Aboveground competition for light is of equal or greater importance to the growth and survival of seedlings than belowground competition for soil resources. This is an underlying assumption of the remaining two hypotheses. 2) Target seedlings will respond equally to equal densities of similar-sized neighbors of different species. This is the Competitive Equivalence Hypothesis. 3) Target seedlings will show reductions in growth directly proportional to the sizes of equal densities of different-sized neighbors. This is the null form of the Asymmetrical Competition Hypothesis. The investigators will create replicated neighborhoods around central target individuals by thinning existing high-density areas to leave neighbors of the desired density, species, and size. Response of target seedlings will be measured as growth in height and stem diameter, and analyzed as relative growth rate. Responses will be measured over two years from the time of treatment. Results will determine whether the above hypotheses accurately describe the competitive interactions among these woody species and how the species differ in their competitive effects on one another.