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

以前的工作已经表明，土地利用强度强烈地改变了草原植物的元素浓度(化学计量)(“BioComp”项目)。在这里，我们继续监测群落生物量质量，并将这种化学计量分析扩展到食草动物，不仅侧重于大量营养素，而且还侧重于微量营养素和微量元素。植物和食草动物种群在土地利用梯度上的种内化学计量差异将使我们深入了解专门化和通用化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性能。群落生物量和单一植物物种的元素组成将与植物多样性、土地利用，特别是肥料和土壤资源有关。我们预计这是一种强烈依赖元素的反应，与群落生物量相比，单个物种的化学计量失配程度更高，物种之间的变异性更高，特别是在低产量、物种丰富的草原上。同样，食草动物的组成将与它们的寄主植物的变异有关。我们假设，除了次生代谢物外，与寄主植物营养特性相关的限制因素有助于草食动物性能、寄主植物选择和草食动物组合组成的变化。基于饲养试验，我们比较了目标草食动物(如蝗虫、毛虫)对沿土地利用梯度采样的叶片材料的消耗及其表现。我们预计，那些主要出现在未施肥草原的物种在生长在施肥地点的植物上表现较差，反之亦然，因为它们的饮食中各自的营养和微量元素失衡。此外，我们将分析土地利用强度、植物物种丰富度和生产力梯度上植物生物量大量营养素组成的年际变异性，从而解决有助于更好地理解生物多样性与生态系统稳定性关系的重要化学计量学问题。

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.