Impact of climate change on the diversity and functioning of soil microbial communities
Figure 1. Main ridge of study site, Mount Cardrona. Image - BJA.
Microorganisms comprise the majority of soil biomass and diversity and provide vital ecosystem services such as the breakdown of soil organic matter and cycling of available nitrogen. However, despite the importance of microbial communities for soil health and fertility, we know remarkably little about their response to changing climatic conditions.
In partnership with researchers at the University of Auckland and the University of Otago, scientists at Landcare Research are exploring attributes of soil microbial communities within the tussock grasslands of New Zealand’s Southern Alps. Across this varied landscape, fine-scale gradients in microclimate conditions are detectable across short distances, caused by variability in site elevation or aspect. These steep temperature gradients along and around the mountain ridge are used to provide valuable insights as to the importance of thermal microclimates on various soil microbial attributes.
An extensive network of 405 sampling locations has been established at Mount Cardrona in Central Otago, and soil collected to cover the varied landscape topology, which includes a gradient in elevation from 500 to over 1900 metres above sea level (a.s.l.; corresponding to an average temperature change of ~8.5°C). Using advanced next-generation DNA sequence analysis, researchers are identifying tens of thousands of the most dominant bacterial and fungal species in each soil sample. Fine-scale differences in microbial community composition can then be mapped across the microclimate gradient. By comparing this microbial community data with temperature data collected at each sampling location, Landcare Research scientists hope to provide better predictions of future microbial community composition under a range of climate scenarios.
Modern molecular methods are also being used to quantify the abundance of key functional genes (e.g. nitrogen-cycling genes) and their relationship to variation in microclimate conditions across all study sites. This information will shed new light on how variations in climatic conditions may impact key indicators of soil health and fertility, and even alter the balance of CO2, N2O and CH4 production and degradation, processes that could further exacerbate future rates of climate change.
The outcomes of this project will increase understanding of (1) the likely resilience/fragility of indigenous tussock grassland ecosystems to the threat of climate change, (2) the likely impact of climate change on nitrogen cycling by soil microbes in tussock grasslands and its potential to affect concentrations of plant available N and soil N2O emissions, and (3) the importance of the relationship between grassland plants and the microorganisms that surround them.
This work was part-funded by the Miss EL Hellaby Indigenous Grasslands Trust.
Barbara J. Anderson — Landcare Research
Gavin Lear, Jieyun Wu — Auckland University
P: 09 373 7599 E: g.lear@auckland.ac.nz
Ralf Ohlemüller — University Of Otago
P: 03 479 8784 E: rso@geography.otago.ac.nz