Land-use effects on plant-herbivore stoichiometry: micro- and macronutrients

先前的研究表明，土地利用强度强烈地改变了草地植物的元素浓度（化学计量学）（“Biocomp”项目）。在此，我们将继续监测群落生物量质量，并将这种化学计量学分析扩展到食草动物，不仅关注宏量营养素，而且关注微量营养素和微量元素。沿着土地利用梯度，植物和食草动物种群的化学计量学种内变化将使我们深入了解特化和一般物种的可塑性或动态平衡的程度，这可能会限制它们的分布和表现。群落生物量和单一植物物种的元素组成与植物多样性、土地利用，特别是施肥和土壤资源有关。我们预计，与群落生物量相比，单个物种的化学计量不匹配程度更高，物种之间的变异性更高，特别是在低生产力的物种丰富的草原上，这是一种强烈的元素依赖反应。同样，草食动物的组成将与其寄主植物的变异有关。我们推测，除了次生代谢物外，与寄主植物营养特性相关的限制因素也导致了食草动物性能、寄主植物选择和食草动物组合组成的变化。在饲养试验的基础上，我们比较了目标食草动物（如蚱蜢、毛毛虫）对土地利用梯度取样的叶片材料的消耗及其性能。我们预计，那些主要生长在未施肥草地上的物种在受精地点生长的植物上表现不佳，反之亦然，因为它们各自的营养和微量元素在饮食中不平衡。此外，我们将在土地利用强度、植物物种丰富度和生产力梯度上分析植物生物量常量养分组成的年际变化，从而解决重要的化学计量学方面的问题，这将有助于更好地理解生物多样性-生态系统稳定性的关系。

Previous work has shown that land-use intensity strongly alters element concentrations (stoichiometry) of grassland plants (project 'Biocomp'). Here we continue the monitoring of the community biomass quality and will extend this stoichiometric analysis to herbivores, focusing not only on macronutrients but on micronutrients and trace elements as well. Intraspecific variation in stoichiometry across plant and herbivore populations along the land use gradient will give us insights into the extent of plasticity or homeostasis of specialised and generalised species, which may constrain their distribution and performance. Elemental composition of community biomass and single plant species will be related to plant diversity, land use, particularly fertilization and soil resources. We expect a strongly element-dependent response with a higher level of stoichiometric mismatch for single species compared to community biomass and higher variability among species particularly in low productive species-rich grasslands. Similarly, composition of herbivores will be related to variation in their host plants. We hypothesize that apart from secondary metabolites, constraints related to nutritional characteristics of host plants contribute to changes in herbivore performance, host plant choices and herbivore assemblage composition. Based on feeding trials, we compare the consumption by target herbivores (e.g. grasshoppers, caterpillars) and their performance on leaf material sampled along the land use gradient. We expect that those species that predominantly occur in unfertilized grasslands perform less well on plants grown in fertilized sites and vice versa, due to respective nutrient and trace element imbalances in their diet. Additionally, we will analyse the inter-annual variability in plant biomass macronutrient composition across the gradients of land-use intensity, plant species richness and productivity and will thereby address important stoichiometric aspects that will contribute to a better understanding of the biodiversity - ecosystem stability relationship.