PriOrity Effect Mechanisms (POEM): mechanisms of priority effects and their persistence over time in dry acidic grasslands

历史的重要性：生物多样性的丧失作为全球变化的一个关键组成部分，要求我们增加生态知识对恢复自然系统中的生物多样性的预测能力。生物多样性-生态系统功能实验清楚地表明，植物多样性是温带草原生态系统功能的重要驱动力，但现在一项有争议的讨论提出了这样一个问题：这种“人工”群落(在不允许自然组装的实验中)与“真实世界”生态系统有多大关系。最近的研究表明，装配历史，特别是植物功能群不同到达顺序引起的所谓优先效应，不仅影响群落结构，还影响地下和地上生产力等生态系统功能。尽管优先效应对于理解群落集合很重要，但与系统发育或性状方法相比，优先效应受到的关注要少得多，这可能是因为方法学上的挑战。然而，我们知道历史很重要，使关于优先效应的更好的知识，特别是其机制，对于提高我们对植物群落聚集的整体理解和提高对自然生物多样性的预测能力至关重要。我们的项目旨在通过(1)将关于优先效应(生态位抢占和修改)背后的机制的研究与更常见的植物物种共存理论联系起来(2)调查植物建立过程中的天气条件如何调节干燥酸性草原优先效应的产生和轨迹。我们的主要假设是，较早到达的物种对植物-土壤-微生物群落环境的影响将根据最先到达某个地点的功能基团的不同而不同，从而影响较晚到达的物种，导致群落结构和功能的不同，这反过来将受到植物建立过程中天气条件的调节。将在连续几年启动不同植物功能组到达顺序(豆类、牧草、杂草)的田间试验，并与温室试验配对，测试植物-土壤反馈在解释植物到达顺序反应方面的相对作用。最先进的根研究方法将使我们能够在物种(基于下一代测序的方法)和群落水平(微型加速器)研究根生态位划分。还将使用分子条形码方法研究实验处理对土壤和植物相关微生物群细菌和真菌多样性的影响。该项目的附加值在于将不同的生态知识联系和整合，以更好地了解优先影响的产生、持续和轨迹。这样做，我们的目标是更好地了解随着时间的推移，植物物种如何在群落中共存。

History matters:Biodiversity loss as a key component of global change requires us to increase the predictive power of ecological knowledge for restoring biodiversity in natural systems. Biodiversity-ecosystem functioning experiments have clearly demonstrated that plant diversity is an important driver of ecosystem functioning in temperate grasslands, but a controversial discussion now asks the question how relevant such “artificial” communities (in experiments that do not allow natural assembly) are in “real world” ecosystems. Recent work has shown that assembly history, in particular so-called priority effects caused by different order of arrival of plant functional groups not only affects community structure, but also influences ecosystem functions such as belowground and aboveground productivity. Despite their importance for understanding community assembly, priority effects have received much less attention than phylogenetic or trait approaches, probably due to methodological challenges. Yet we know that history matters, making improved knowledge on priority effects, in particular their mechanisms, essential to improve our overall understanding of plant community assembly and the improve predictive power for natural biodiversity.Our project aims to fill this gap in knowledge by (1) linking research on the mechanisms behind the creation and persistence of priority effects (niche preemption and modification) with more common theories of plant species coexistence (and (2) investigating how weather conditions during plant establishment modulate the creation and trajectory of priority effects in dry acidic grasslands. Our main hypothesis is that the effect of early-arriving species on the plant-soil-microbiome environment will differ depending on the functional group that arrives first at a site, thus affecting the species arriving later, leading to communities differing in structure and functioning, and this will in turn be modulated by weather conditions during plant establishment. A field experiment with different plant functional group order of arrival (legumes, grasses, forbs sown first) will be initiated over consecutive years and paired with a greenhouse experiment testing the relative role of plant-soil feedback in explaining responses to the plant order of arrival. State of the art methods in root research will allow us to study root niche partitioning at the species (next generation sequencing-based method) as well as the community level (minirhizotrons). The effect of experimental treatments on the bacterial and fungal diversity of the soil and plant-associated microbiomes will also be studied using a molecular barcoding approach.The added value of this project lies in the linking and integration of different ecological knowledge to better understand the creation, persistence, and trajectory of priority effects. Doing so, we aim at gaining a much-improved understanding of how plant species coexist in communities over time.