Of Plants, Microbes and Ecology
Feb 2014
For more than 450 million years, plants and microbes have evolved and co-habited together. This relationship involves beneficial effects and harmful interactions, both significant and at the same time intriguing as a research perspective. These plant and microbial interactions affect the functioning of the biosphere as well as food production to support human life.
And how these interactions occur drives Prof. Sanjay Swarup on his work in plant improvement and ecological functioning. That same interest has also compelled him to pursue working in Tropical Peatlands, one of the most significant ecosystems influencing climate change.
How it all began
Prof. Swarup’s work on peatlands started when he was coordinating a project on freshwater systems for the Singapore-Delft Water Alliance (SDWA). Peatlands are formed by the accumulation of partially decayed vegetation matter over thousands of years in low-lying areas that are frequently waterlogged due to heavy rainfall or periodic inundation. Prof. Swarup began to realise a huge scientific gap – while the basis of peat oxidation and loss seemed to involve microbes, there was no clear understanding of the microbiological and metabolic processes involved.
In his mind, intact peat is largely “pickled” plant biomass. If microbes are the ones responsible for oxidation, then this process may lead to further emissions of greenhouse gases (GHGs). For him, this is something worth looking into.
Journey to peatlands
Prof. Swarup has been well-trained in plants and microbial dynamics. Holding two PhDs – one from the Indian Agricultural Research Institute (IARI) and another from the University of Florida (UF), he has a vast experience investigating microbes attacking plants and how plants defend themselves. His post-doc years dwelled in further understanding plant dynamics as host organisms.
Working with peatlands was a perfect opportunity to further pursue his fascination with plants and microbes interacting together.
Painting a picture of degradation
In recent years, the rapid development of land-use has changed the face of peatlands. Not only did it alter the ecological nature of these ecosystems, it has also triggered the release of carbon from peat, thereby influencing transboundary pollution and climate change. Documenting phase shifts in the peatland ecosystems has always been a challenge. There were very few available scientific accounts on tropical peatlands. A report has been established on peat sources many years back, emphasizing the lack of scientific studies especially on tropical peatlands found mostly in Indonesia and its neighbouring countries in Southeast Asia (Shier, 1985)a. Twenty years later, much progress has been made, but large gaps still remain in understanding peatlands formation and functioning.
Since these peatlands are rich in carbon, the actual ground scenario of peatland conversion to agricultural lands is alarming if not managed in a sustainable manner. The process of conversion involves clearing the forest by fires and logging, and further draining the water from peat.
“The moisture content and the water table is generally high in natural conditions. Whenever plantation workers mechanically remove water through drains, a drastic decrease in peatland water tables exposes the biomass sequestered in the peat to aerobic microbial oxidation. For better yield, these plantation owners add chemicals (i.e. fertilizers, pesticides, etc.) that have adverse effects not only in plantations but also in canals and drainage systems where these nutrients and dissolved carbon are being washed out.” says Prof. Swarup.
“As peat subsides through drainage, outcomes will affect livelihoods. First, the usable life of agricultural lands will be shortened. Second, the low-lying regions of peatlands will subside even more, thus, increasing flooding risks. In fact during my field visits, I see how local folks are adapting to the subsiding peat and its increased duration of flooding. Local folks try temporary measures to hold the plant by accumulating peat surrounding it (as shown in Figure 1). However, crop sustainability is highly affected, in my opinion.” he adds. The accompanying photo (Figure 2) shows how villagers have adapted with flooding in their areas.
The changing climate patterns may even exacerbate the impacts to the human communities, making them more vulnerable to the risks posed by flooding.
Finding solutions through the microbial perspective
To further investigate the critical role of microbes in the life and survival of peatlands, Prof. Swarup pooled experts from NERI and SCELSE to further dig into the topic. He has been leading a group of researchers in NUS, working together for almost seven years now.
Metabolomics – the systematic way of studying metabolites (small molecules that are products of metabolism) – has greatly influenced Prof. Swarup’s work. Together with his team, they have been identifying the enzymes found in the root region (called the rhizosphere) that can utilize chemicals by microbes for food purposes.
The research team has recently shown that the beneficial “rhizosphere effect” is also evident in peat plantations (Mishra et al., 2014)b. One rather infrequently used practice is mixed crop plantations (i.e. growing fruit crops such as, tapioca, pineapple, papaya or banana within oil palm plantations). Both microbial and chemical (metabolic) diversity are high in these sites, most likely arising due to the root exudates from the diverse plants found on the peat surface. Most importantly, the rate of peat loss is minimal in these mixed crop plantations. These may lead to possible solutions in managing plantations and reducing GHGs from peat.
The fate of peat’s carbon
In order to effectively manage GHG emissions coming from peat, having a good estimate of the carbon budget is of utmost importance.
“When I started, there were scattered reports on the extent of carbon sequestered in the peat. In our part of the world, peat can be very deep and extensive. It’s up to 20m deep and extends in millions of hectares. So, there were no real estimates of what is the total amount of carbon there.” tells Prof. Swarup.
“In the last few years, there has been some sort of a consensus among scientists from different parts of the world working on peatlands for more than two decades, of what the general numbers are.”
In Southeast Asia, peatlands cover an area of nearly 25 million ha and store approximately 69 Gt of carbon, which is 77% of all the tropical peatland carbon pool (88.6 Gt), of which 65% (57.4 Gt of carbon) is in Indonesia itself, distributed within 23.4 million ha of peatland (Page et al., 2011)c. Tropical peatlands contribute about 8% of the global GHG emissions due to fossil fuels, making sustainable practices and management schemes extremely important and necessary.
Carbon dynamics change the air and contribute to the water system. Waters are being lost through drainage and so does fluvial carbon. These are called “fluvial losses” since they are released through rivers or canal systems. These losses need to be properly accounted in order to come up with better carbon budgets for peatlands.
“I believe at this point, a lot of interest and attention has come to peatlands research. If we can keep this research going with people in the region by doing good science and providing data, together with international experts in the International Panel on Climate Change (IPCC), then it will raise the amount of awareness of how we can manage peatlands ecosystems balanced with development. Science and technology have to provide solutions that will be implemented together with the policy-makers.”
Peatlands research moving forward
NUS has been supporting research in peatlands for several years now. However, there are more things needed to be done so that activities on peatlands will continue in a sustainable way.
“What we are hoping to contribute from NERI is to bring some continuity to the research efforts. We are going to find ways in which dispersed expertise may be brought together. Once they are brought together, I think working with our Indonesian partners in Java and Sumatra will build on that. We will bring advisers - top scientists who know peat from a larger timescale and understand the bigger picture for us to be directed in the right way.”
“The strength of NUS lies in looking at the details of the mechanisms as to how and why things happen in a particular way and how human activities affect these mechanisms. Researchers at NUS are in a very good position to contribute to the fundamental science.”
Peatlands research has been attracting so much interest because by nature, it is a big environmental issue in the region. Even the IPCC has also embraced this as an international issue. Therefore, NUS can play a very strong role in doing good science to help understand environmental issues that impact us all in this region.
“This is very much in line with what NUS wants in moving forward with environmental and water research under the umbrella of NERI – to look at issues of this nature. It is stimulating enough. It is a challenging thing and it is the right thing to do.”
And so for Prof. Sanjay Swarup and the rest of his research team, there are more substantial things to pursue in peatlands research.
“I think we will be doing this for some time because it is a difficult challenge and it won’t be solved so easily. We will be working on this for a while.” he says.
(Edited by Prof. Sanjay Swarup and Shailendra Mishra)
References:
- Shier, C.W. (1985), Tropical peat resources - an overview, in Symp. Tropical Peat Resources - Prospects and potential, pp. 29-46, International Peat Society, Kingston, Jamaica.
- Mishra, S. W. A. Lee, A. Hooijer, S. Reuben, I.M. Sudiana, A. Idris, and S. Swarup (in press, 2014),“Microbial and metabolic profiling reveal strong influence of water table and land-use patterns on classification of degraded tropical peatlands, Biogeosciences.
- Page, S E., J.O. Rieley and C.J. Banks (2011). Global and Regional Importance of the Tropical Peatland Carbon Pool. Global Change Biology, 17: 798–818.
For more details, please contact:
Associate Professor Sanjay Swarup
Email: dbsss@nus.edu.sg