Does biodiversity restoration enhance the capacity of ecosystem functions to buffer climate extremes?

Abstract

The influence of biodiversity on the stability of ecosystem functions has been a focus of research for several decades. When considering the temporal stability of ecosystem functions, particularly plant productivity, the evidence from experimental studies for a positive effect of biodiversity on stability is strong. However, challenges emerge when attempting to replicate results in natural settings and when examining the stability of ecosystem functions in response to extreme environmental perturbations, such as climate extremes. Under these scenarios, the relationship between diversity and stability often becomes mixed or even undetectable. Of particular importance is stability of ecosystem functions in terms of their capacity to resist and recover from climate extremes, such as drought, which are increasing in their intensity and frequency with climate change. Moreover, combined with more frequent and intense climatic extremes, global change factors, especially the intensification of land use, are reducing biodiversity of ecosystems such as grasslands, causing reductions in ecosystem functioning. To counteract this, the restoration of botanical diversity in grasslands has been a target of European agricultural policy to improve ecosystem functioning and the delivery of the ecosystem services. It is not yet clear, however, how land management practices targeted at promoting plant diversity may influence the stability of those ecosystem functions, especially under climate extremes. The aim of this thesis is to provide insight into diversity-stability relationships, in particular whether restoration practices designed to promote plant diversity buffer the response of ecosystem functions to climate extremes. In order to do this, I assessed the diversity-stability relationship across a range of studies and experimental scales including: (1) experimental work testing how community evenness and dominant species identity impact the stability of CO2 fluxes; (2) long-term intra-annual field assessments evaluating the impact of restoration practices on the stability of a suite of ecosystem functions; and (3) targeted assessment of carbon cycling processes and their response to simulated drought in a plant diversity restoration field experiment. Across these studies I found mixed evidence for the impact of diversity restoration management on the stability of ecosystem functions. When assessing the effect of diversity management on the stability of functions at an individual level, restoration by (1) manipulating evenness and (2, 3) seed addition and cessation of fertiliser addition did not buffer the impacts of extreme drought. However, I found that (1) dominant plant species identity did impact the resilience of CO2 fluxes to drought, and (2) by taking a multifunctional approach to assess a suite of ecosystem functions simultaneously, I identified that diversity restoration by seed addition led to increased multifunctional resilience in response to drought. Overall, our findings lend some support to the positive effect of plant diversity restoration practices on ecosystem stability, but highlighted the need for studies to include multiple aspects of biodiversity and stability as well as assess multiple functions simultaneously in order to detect these relationships, particularly when working in natural environments.

Date of Award	1 Aug 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	David Johnson (Supervisor) & Richard Bardgett (Supervisor)