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

生物多样性丧失是全球变化的一个关键组成部分，这要求我们提高生态知识的预测能力，以恢复自然系统中的生物多样性。生物多样性-生态系统功能实验已经清楚地表明，植物多样性是温带草原生态系统功能的重要驱动力，但现在有一个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）在“真实的世界”生态系统中的相关性如何。近年来的研究表明，植物功能群的聚集历史，特别是功能群不同到达顺序所产生的优先效应，不仅影响群落结构，而且影响地下和地上生产力等生态系统功能。尽管他们的重要性，了解社区大会，优先级的影响得到了比系统发育或性状的方法少得多的关注，可能是由于方法上的挑战。然而，我们知道，历史很重要，它使人们更好地了解优先效应，特别是其机制，我们的项目旨在通过以下方式填补这一知识空白：（1）将优先效应产生和持续背后的机制研究联系起来，生态位抢占和修改）与更常见的植物物种共存的理论（和（2）调查如何在植物建立过程中的天气条件调节的创建和在干燥的酸性草原优先效应的轨迹。我们的主要假设是，早到物种对植物土壤微生物组环境的影响将取决于首先到达某个地点的功能组，从而影响稍后到达的物种，导致群落结构和功能不同，这反过来又会受到植物建立期间天气条件的调节。不同植物功能组到达顺序（豆类，草，杂类草播种第一）的田间实验将连续几年启动，并与温室实验测试植物土壤反馈的相对作用，解释植物到达顺序的反应。根研究的最先进的方法将使我们能够研究根生态位划分在物种（下一代测序为基础的方法），以及社区水平（minirabetrons）。此外，还将使用分子条形码方法研究实验处理对土壤细菌和真菌多样性以及与植物相关的微生物的影响。该项目的附加价值在于将不同的生态学知识联系起来并进行整合，以更好地了解优先效应的产生、持续和轨迹。这样做，我们的目标是获得一个更好的了解植物物种如何共存于社区随着时间的推移。

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.