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

Project: Research

Project participants

History matters in ecology
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.