Biological controls on soil respiration and its climatic response across a large tropical elevation gradient

Lead Research Organisation: University of Edinburgh
Department Name: Sch of Geosciences

Abstract

This project will advance our ability to quantify the influence of climatic warming on the emission of CO2 from soil by investigating how soil biological and functional diversity (roots and microbes), and soil chemical properties, limit respiration processes in soil. This work will be the first of its kind to address this question over a large elevation gradient and in a tropical region where biodiversity and biogeochemical cycling of carbon are very high. The carbon balance of an ecosystem is strongly dependent on the balance between photosynthesis and respiration. Globally, respiration on land is at present very slightly smaller than photosynthesis, meaning that terrestrial ecosystems are thought to be a 'sink' for atmospheric carbon dioxide, slowing the continual rise in carbon dioxide (CO2) concentration in the atmosphere. The largest fraction of total respiration from land comes from the decomposition of organic matter in soil. This decomposition leads to emissions of CO2 to the atmosphere. The rate of decomposition may increase under climatic warming, possibly accelerating climate change over this century, so we need urgently to understand what the risk of this happening is. Our study site is in the tropical rain forests of Peru, ranging in altitude from 3000 m to 220 m above sea level. The soil carbon stock is large, particularly at high elevation and so represents a risk in the sense that this carbon could be broken down and emitted as CO2 under climatic warming. Our preliminary data suggest that there are large differences in the temperature sensitivity of soil CO2 emissions in these forests, with high sensitivity at high elevations. This project aims to understand these differences in sensitivity by examining controls over the decomposition of organic matter that are exerted by the physical environment and also by roots, and by the decomposing microbes in soil. Our study site is ideally suited to address this question because it spans a natural temperature gradient of 12-26 degrees Celsius. We will use this in two ways: (i) to observe natural differences in CO2 emissions at different elevations and temperatures and (ii) to examine the effects of transplanting soil from one elevation and 're-planting' it at another. We have performed part (ii) for 4 sites across our elevation gradient and now haave an exceptional opportunity to study the effects, and to advance our understanding of short- and long-term climatic warming of soil CO2 emissions. Our approach will be to observe the temperature response characteristics of soil CO2 emission in natural and transplanted soil. We will make high temporal resolution measurements over 2.5 years, further manipulating the soil to see the effects of removing roots and mycorrhizal fungi from the decomposing system. We will measure the physical environment and the chemical complexity of the soil carbon. We will also measure the biological diversity of microbes in the soil using leading edge membrane- and DNA-based techniques. Finally we will use a laboratory experiment to trace the types of carbon compound that different microbes use from different sites along the study transect. Here we will 'feed' the soil with a stable (safe) carbon isotope and trace where that carbon is used and emitted - ie how much labeled CO2 is emitted and which organisms use it in their metabolism. This will give us valuable information to inform our analysis of the data we get from field measurements. In our analysis we will statistically examine what microbes/root functions are most important for constraining the response by soil respiration to climatic change and use our laboratory data to provide mechanistic interpretations of our statistical analysis. Combined we will develop a new understanding of the response by soil respiration to climatic warming and we will test how important biological diversity is for controlling and constraining that response, and its effect on climatic change.

Publications

10 25 50

 
Description We have a large range of findings from this work, showing: biogeographical change in diversity and function with elevation; the role of nutrient availability on decompostion processes; the effect of low soil density and equipment design on the accuracty of flux measurements; the temperature sensitivity of soil CO2 emissions. Although some publicatoins are out, there has been a delay of around 12 months for some following a serious illness that the post doctoral research assistant suffered towards the end of his contract. Most recently we have published findings on separating the sources of differences in temperature sensitivity in soil respiration, and our analysis indicates that soil carbon in montane forest systems is likely to be very temperature sensitive. The differences in temperature sensitivity and response to new carbon sources differs by location and by microbial communitiy in the soil. This latter work leads towards the idea that differences in microbial diversity in soil are important for differences in its functional properties. We are also working on new findings that show that microbial diversity follows similar patters to plant and diversity, with changes in elevation; this is new, but consistent with long term understanding of plant biogeography.
Exploitation Route This work is of wide interest within the following science areas: ecology, soil biology, biodiversity, ecosystem function, earth system science.
The understanding it contributes to will be used to inform (improve) earth system models, and thereby influence climate and land use policy.
Sectors Education,Environment

 
Description The results have been linked to the soil ecosystem and earth system modelling communities for use in ecosystem and climate science, and relevant policy formulation. The success of the work has led to a (successful) EU fellowship application, leading to career development. An educational web-site, aimed at mid-high school children, to inform about climate change and provide detailed information on the research work at the University of Edinburgh. Ongoing work aims to translate the web-page into Spanish, which will be a resource for the schools education program (see 'Global Garden school talks' impact). A educational website to engage school children in learning about climate change - in the context of our research work.
First Year Of Impact 2012
Sector Education,Environment
Impact Types Societal,Economic,Policy & public services

 
Description Meeting with Peruvian Ministry for the Environment
Geographic Reach South America 
Policy Influence Type Implementation circular/rapid advice/letter to e.g. Ministry of Health
Impact Meeting with Peruvian Ministry for the Environment, held in Lima, August 2013. Meeting was attended by Patrick Meir and other Principal Investigators involved in ecological research projects in the Manu National Park area in Peru. The aim of the meeting was to raise awareness of current environmental and conservation issues in the Manu National Park-Madre Dios area and engage the Peruvian government in activating their own research agenda and to inform new policies on conservation and ecosystem services. Thus the impact was on approximately 10 government employees within the environment ministry; the informatoin was received positively by the minister.
 
Description Human Modified Tropical Forests Programme
Amount £4,000,000 (GBP)
Funding ID NE/K01627X/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 10/2013 
End 09/2018
 
Description Smithsonian Tropical Research Institute Tupper Fellowship
Amount £30,000 (GBP)
Organisation Smithsonian Institution 
Sector Academic/University
Country United States
Start 04/2014 
End 05/2017
 
Description Smithsonian Tropical Research Institute Tupper Fellowship
Amount £30,000 (GBP)
Organisation Smithsonian Institution 
Sector Academic/University
Country United States
Start 05/2014 
End 05/2017
 
Description Schools interational engagement 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Schools
Results and Impact Building a relationship between Peruvian/Andean schools and Edinburgh schools. Providing some basic inexpensive weather station equipment to log weather data at the schools (they are remote and resource-poor), and then connect with this information with schools in Edinburgh. Increase interest in our research, helped build a 'public licence' to do research, enabled teh students to understand the environment about them and international science
Year(s) Of Engagement Activity 2011,2012,2013,2014