Trophic interactions across tree regeneration stages

更广泛的研究背景：Janzen-Connell假说指出，在物种丰富的森林生态系统中，树木多样性是由营养相互作用维持的，营养相互作用对树木补充产生不利影响，与同种补充物的密度呈正相关，与母树的距离呈负相关。在这一过程中重要的相互作用是种子捕食和幼苗植食。虽然许多研究测试的Janzen-Connell假说昆虫介导的营养相互作用集中在单一的树种，它最终是一个社区水平的hypothesis.Hypotheses：在这里，我们建议研究植物-捕食者和植物-草食动物的相互作用在树木更新阶段与昆虫中心的观点Janzen-Connell假说沿着一个树的多样性梯度在BEF-中国的实验。我们假设（i）树木补充，（ii）传播前和传播后种子捕食以及幼苗食草的相关功能，（iii）通才和专家对这些功能的贡献将沿着树木多样性的梯度变化，（iv）Janzen-Connell效应在这些功能中将取决于树木和昆虫种子捕食者和食草动物的群落组成。我们将量化再生阶段，以及前和后扩散种子捕食和幼苗草食性的选择果树品种与不同的果实性状的观察和实验方法。在所有的核心地块，我们将研究前扩散种子捕食与种子陷阱的帮助下，选定的树种的个人。对早熟和成熟果实进行套袋有助于在传播前阶段识别昆虫捕食者和捕食水平。将使用所选树种的种子卡，在笼子里，排除脊椎动物或脊椎动物和无脊椎动物或允许种子捕食者不受阻碍的访问后，分散的种子捕食进行研究。在所有VIP地块中，我们将评估自然招募成功率。对于选定的树种，我们还将评估由于昆虫植食性和真菌感染对后代造成的叶片损害。发芽和幼苗草食性也将实验评估我们所选择的树种，通过添加种子和幼苗在无脊椎动物的围栏和控制在家里和远离的情况沿着树的多样性梯度。提供这些功能的昆虫代理商的鉴定将得到分子技术的支持。创新：我们将研究Janzen-Connell效应的捕食种子，以及发芽和植食性的幼苗在树木繁殖的关键生命阶段与昆虫中心的观点。通过试图确定种子捕食和草食性的代理人，我们将增加一个决定性的组成部分，在亚热带森林生态系统的营养网络。在一致，我们的方法将补充我们的基本知识，物种如何在这个系统中相互作用，跨营养级，从而如何保持树木的多样性。

Wider research context: The Janzen-Connell hypothesis states that tree diversity in species-rich forest ecosystems is maintained by trophic interactions that adversely affect tree recruitment and are positively related to density of conspecific recruits and negatively to distance from mother trees. Important interactions in this process are seed predation and seedling herbivory. While many studies testing the Janzen-Connell hypothesis on insect-mediated trophic interactions focused on single tree species, it is ultimately a community-level hypothesis.Hypotheses: Here we propose to study plant-predator and plant-herbivore interactions across tree regeneration stages with an entomocentric view of the Janzen-Connell hypothesis along a tree diversity gradient in the BEF-China experiment. We hypothesize that (i) tree recruitment, (ii) the associated function of pre- and post-dispersal seed predation as well as seedling herbivory and (iii) the contribution of generalists and specialists to these functions will vary along the gradient of tree diversity, (iv) Janzen-Connell effects in these functions will depend on community composition of trees and insect seed predators and herbivores.Methods: We will quantify regeneration stages as well as pre- and post-dispersal seed predation and seedling herbivory of selected fruiting tree species with differing fruit traits with observational and experimental approaches. In all core plots, we will study pre-dispersal seed predation with the help of seed traps under individuals of selected tree species. Bagging of premature and ripe fruits will help to identify insect predators and predation levels at the pre-dispersal stage. Post-dispersal seed predation will be studied using seed cards of the selected tree species in cages that exclude vertebrates or vertebrates and invertebrates or allow unhindered access of seed predators. In all VIP plots, we will assess natural recruitment success. For selected tree species, we will also assess leaf damage due to insect herbivory and fungal infection on the offspring. Germination and seedling herbivory will also experimentally be assessed for our selected tree species by adding seeds and seedlings in invertebrates exclosures and controls in home and away situations along the tree diversity gradient. Identification of insect agents delivering these functions will be supported by molecular techniques.Innovation: We will study Janzen-Connell effects for predation of seeds as well as germination of and herbivory on seedling as crucial life stages during tree reproduction with an entomocentric view. By trying to identify agents of seed predation and herbivory, we will add a decisive component of the trophic network in subtropical forest ecosystems. In concert, our approaches will complement our basic knowledge of how species interact in this system across trophic levels and thus how tree diversity is maintained.