Indirect plant-trait mediated effects of tree diversity on herbivores

混合植物物种中的食草性水平通常低于单一植物，建议将林分多样化作为减少农业和林业害虫损害的一项战略。几种机制可以解释这种混合物中的联合抗性现象，例如宿主植物稀释和天敌增加。但对于一些食草动物来说，植物混合物代表了首选的栖息地，它们在混合林中的损害高于单一种植（联合易感性）。为了有效地利用植物多样化作为减少虫害的策略，我们需要能够预测何时可能出现联合抗性或联合易感性。该项目将探索一种新的机制，可能解释害虫反应的变化-由于与种内邻居的相互作用（例如，通过阴影），物种混合物中叶片质量的变化。该项目将利用几个树木多样性实验（芬兰的萨塔昆塔实验和英国的ClimateMatch实验），探索物种混合和单一栽培中重点树木的叶子特征，包括化学和物理防御以及营养水平。也将测量相关的食草动物水平以及非生物变量，如光照水平。还将对已发表的研究进行荟萃分析，这些研究探讨了树木多样性对食草动物植物质量的影响。该项目将使概括的条件下，植物质量的树木混合物可能会增加导致联想的敏感性，而不是联想的阻力。该项目将为学生提供元分析和实地工作技能。

Levels of herbivory in plant species mixtures are often lower than in plant monocultures and stand diversification is recommended as a strategy to reduce pest damage in agriculture and forestry. Several mechanisms can explain this associational resistance phenomenon in mixtures, e.g. host plant dilution and increase in natural enemies. But for some herbivores plant mixtures represent preferred habitats and their damage is higher in mixed stands than in monocultures (associational susceptibility). In order to use plant diversification effectively as a strategy to reduce insect pests, we need to be able to predict when associational resistance or associational susceptibility is likely to arise. This project will explore a novel mechanism which might potentially explain variation in pest responses - variation in leaf quality in species mixtures due to interactions with intraspecific neighbours (e.g. through shading). This project will explore leaf traits, including chemical and physical defences, as well as nutrient levels, on focal trees in species mixtures and monocultures using several tree diversity experiments (Satakunta experiment in Finland and ClimateMatch experiment in the UK). Associated levels of herbivory as well abiotic variables such as light levels will also be measured. A meta-analysis of published studies which explored the effects of tree diversity on plant quality for herbivores will also be conducted. The project will enable generalisations as to the conditions when plant quality in tree mixtures is likely to increase causing associational susceptibility instead of associational resistance. The project will provide student with meta-analysis and field work skills.