Structure of Plant-Arthropod Associations: Impact of Herbivores on Community Composition and Host Performance

9527536从废弃农田清除昆虫的长期试验所创造的条件，为检验植物演替模型中的关键假设提供了一个难得的机会。在之前的一次实验中，对以植物为食的昆虫的抑制释放了对黄花种群的控制。在这种情况下，黄花成为强大的竞争优势，抑制了许多在正常植物演替中突出的植物物种。这项研究将衡量停用杀虫剂治疗后的变化，以揭示草食动物如何解释由具有强烈抑制影响的植物主导的群落中的植被变化。这项实验的结果还将证明，昆虫是大多数陆地生态系统的主要组成部分，它的消失只是倒退了正常的演替变化顺序，还是导致群落沿着一条全新的轨道发展，从而产生了一种持久的、以前未知的植物联系。在另一组实验中，将研究导致黄花优势的属性。以前的研究表明，黄花对食草动物的损害是通过降低它们的繁殖力来回应的，但不会降低它们的种子质量。正如我们对大多数植物种群生物学的理解一样，人们对种子离开亲本后的命运知之甚少。发芽地点的可用性、老化种子的活力丧失、种子库的大小以及种子的传播将在隔离的花园中进行田间试验，在那里种子的密度和年龄受到控制。这次调查将进一步加深我们对长期休耕田地管理策略的理解。对种子传播和种子库动态的研究将更好地深入了解杂草种群的建立过程。

9527536 Root The conditions created by a long-term experiment involving the removal of insects from abandoned agricultural fields provide an exceptional opportunity to examine key assumptions in models of plant succession. In a previous experiment, the suppression of plant-feeding insects released the controls on goldenrod populations. Under these circumstances, goldenrods became strong competitive dominants that suppressed many plant species that are prominent in normal plant succession. This study will measure the changes that follow the withdrawal of insecticide treatments to reveal how herbivores can account for vegetational change in communities that are dominated by plants with strong inhibitory influences. The results of this experiment will also demonstrate whether the removal of insects, a major component in most terrestrial ecosystems, merely sets back the normal sequence of successional changes or if it causes the community to develop along an entirely new trajectory that produces a persistent and previously unknown plant association. In another set of experiments, the attributes that are responsible for the dominance of goldenrods will be examined. Previous work has shown that goldenrods respond to herbivore damage by reducing their fecundity, but not the quality of their seeds. As is the case with our understanding of the population biology of most plants, little is known about the fate of the seeds after they leave the parent. The availability of germination sites, loss of viability in aging seeds, size of the seed bank, and dispersal of seeds will be addressed in field experiments in isolated gardens where the density and age of seeds are controlled. This investigation will further our understanding of management strategies for fields in long-term fallow. The studies on seed dispersal and the dynamics of seed banks will provide better insight into the processes involved in the establishment of weed populations.