Plant diversity is crucial for successful ecosystem

Ecosystems can only function well if there is a diverse mixture of plants across the landscape. That is concluded after doing fieldwork in 15 different countries on 5 continents. The results of the study are published in Nature Ecology and Evolution.

A new study from a large, global collaboration of plant ecologists shows that for ecosystems to function well, it is important to conserve both diverse mixtures of species at single locations and to preserve a diverse variety of species across landscapes. It is known from small scale experiments that low diversity communities and monocultures often function more poorly (they are less productive and less stable) than more diverse alternatives that contain more species. But small scale experiments do not exactly replicate real world conditions. This publication is the first to prove that the same principles apply to landscapes at a bigger, more realistic scale.

Global network
The study used an international network of grassland sites called the Nutrient Network (NutNet), maintained and monitored by plant scientists across the globe. At each site, researchers counted the number of plant species in local areas (local diversity) as well as the species composition across the landscape (landscape diversity) and related these to the functioning of grassland ecosystems. They found that diversity at both local and landscape scale is necessary for the ecosystems to function well, and that ecosystems function best when diversity is high at both scales simultaneously.

“The effects of one boost those of the other probably due to a greater range of ecological traits of plants including height, leaf area and rooting depth, that complement one another when diversity is high both locally and across the landscape”, says Yann Hautier, lead author and assistant professor at Utrecht University.

Forest Isbell, associate director of Cedar Creek Ecosystem Science Reserve at the University of Minnesota, one of the field sites included in the study, says “Our results are general and robust because data from 65 sites worldwide and many different types of analyses all indicated the importance of biodiversity at local and landscape scales.”

Grassland management
Andy Hector, professor at the University of Oxford adds: “These new results show the danger that short-term and small scale research may underestimate the importance of biodiversity for keeping our ecosystems stable and functioning as we’d like them too”.

The results have implication for grassland management and restoration. For example, rather than seeding an entire field with a single mixture (high local diversity, low landscape diversity), these results suggest that it would be valuable to use different seed mixtures in different parts of the field (high local and landscape diversity).

This article, entitled "Local loss and spatial homogenization of plant diversity reduce ecosystem multifunctionality", is co-authored by the CEF research Maria C. Caldeira.

Link to the article: 

Abstract: Biodiversity is declining in many local communities while also becoming increasingly homogenized across space. Experiments show that local plant species loss reduces ecosystem functioning and services, but the role of spatial homogenization of community composition and the potential interaction between diversity at different scales in maintaining ecosystem functioning remains unclear, especially when many functions are considered (ecosystem multifunctionality). We present an analysis of eight ecosystem functions measured in 65 grasslands worldwide. We find that more diverse grasslands—those with both species-rich local communities (α-diversity) and large compositional differences among localities (β-diversity)—had higher levels of multifunctionality. Moreover, α- and β-diversity synergistically affected multifunctionality, with higher levels of diversity at one scale amplifying the contribution to ecological functions at the other scale. The identity of species influencing ecosystem functioning differed among functions and across local communities, explaining why more diverse grasslands maintained greater functionality when more functions and localities were considered. These results were robust to variation in environmental drivers. Our findings reveal that plant diversity, at both local and landscape scales, contributes to the maintenance of multiple ecosystem services provided by grasslands. Preserving ecosystem functioning therefore requires conservation of biodiversity both within and among ecological communities.