Community assembly history alters relationships between biodiversity and ecosystem functions during restoration.

Relationships between biodiversity and ecosystem functioning depend on the processes structuring community assembly. However, predicting biodiversity-ecosystem functioning (BEF) relationships based on community assembly remains challenging because assembly outcomes are often contingent on history and the consequences of history for ecosystem functions are poorly understood. In a grassland restoration experiment, we isolated the role of history for the relationships between plant biodiversity and multiple ecosystem functions by initiating assembly in three different years, while controlling for all other aspects of community assembly.

Year effects: Interannual variation as a driver of community assembly dynamics.

Environmental conditions that vary from year to year can be strong drivers of ecological dynamics, including the composition of newly assembled communities. However, ecologists often chalk such dynamics up to "noise" in ecological experiments. Our lack of attention to such "year effects" hampers our understanding of contingencies in ecological assembly mechanisms and limits the generalizability of research findings.

Lasting signature of planting year weather on restored grasslands.

Ecological restoration - the rebuilding of damaged or destroyed ecosystems - is a critical component of conservation efforts, but is hindered by inconsistent, unpredictable outcomes. We investigated a source of this variation that is anecdotally suggested by practitioners, but for which empirical evidence is rare: the weather conditions during the first growing season after planting. The idea of whether natural communities face long-term consequences from conditions even many years in the past, called historical contingency, is a debated idea in ecological research.