The new TOC-loss-ometer!

This week, Sarah Cook, a member of the UK TPWG and PhD student at the University of Leicester, published an exciting paper documenting a new, low cost and easy-to-use methodology for measuring DOC losses from tropical peatlands.  Here she describes this important work.

My research is focused on investigating fluvial organic carbon (TOC) losses from tropical peatland oil palm plantations, within Southeast Asia. However, when I first started developing my research methodology I found limited guidance for analysing tropical TOC water samples. Tropical work is often undertaken in remote field sites with limited on-site laboratory facilities (if any), with any flat stable surface (i.e. the dinner table, car boot and concrete floors) quickly becoming a state of the art workbench. In addition, temperature also plays a significant role, with the hot sticky heat quickly degrading anything remotely organic. In my case this could mean the breakdown, and loss, of significant proportions of organic carbon from my water samples. This also meant the need to ship large, heavy and expensive boxes of samples back to the UK for analysis on specialised analytical equipment.

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Collection of fluvial organic carbon from an oil palm plantation drainage channel.

This prompted us to develop better guidance for tropical researchers for TOC analysis, and lead to the publication of a water storage paper (https://doi.org/10.19189/MaP.2016.OMB.249) in 2016 and a recent paper in Water Research (February, 2017; http://dx.doi.org/10.1016/j.watres.2017.02.059). In this most recent paper we investigated the suitability of UV-visible spectrometry to determine dissolved organic carbon (DOC) concentrations in tropical water samples, building on an original methodology developed by (Carter et al.2012; http://dx.doi.org/10.1016/j.watres.2012.05.021) on temperate peat. Overall UV-visible spectroscopy (using both a single and two-wavelength approach) was able to accurately predict tropical DOC concentrations. This offers research groups working in remote field locations the ability to rapidly analyse water samples post-collection, negating the need to store degradable samples for lengthy periods of time, helping improve spatial and temporal DOC measurements. In addition, the equipment required for this analysis can be set up at a field base, valuable for researchers in remote locations with limited access to specialised (and often expensive) analytical equipment. This in turn can help reduce the number of samples that need to be shipped back, further helping to reduce research costs. Full details of both papers can be found at:

https://doi.org/10.19189/MaP.2016.OMB.249

http://dx.doi.org/10.1016/j.watres.2017.02.059

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Graphical abstract from the Water Research paper, showing an example of a plantation drainage channel and predictive ability of the UV model.

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Panamanian peats

In order to understand and appreciate the breadth and importance of the fieldwork carried out by members of the UK Tropical Peatland Working Group, we welcome posts on this blog from anyone with a story to tell.  Here, Nick Girkin, a PhD student from the University of Nottingham, describes the fieldwork he carried out last year in the relatively understudied peatlands of Panama.

In January 2016 I started the second stage of my fieldwork in San San Pond Sak wetland in Bocas del Toro Province, Panama. During my first visit in 2015 I trialled a range of fieldwork techniques investigating how below-ground plant inputs, particularly plant roots and root release of exudates and oxygen, can regulate surface greenhouse gas emissions and the extent to which this differs between plants of contrasting physiologies (i.e. palms vs broadleaved evergreen trees). This time I had developed a range of experimental approaches including plans for in situ mesocosms to exclude roots and root inputs, phloem labelling with natural abundance and 13C labels and a 13CO2 labelling experiment. The results of this work are important in terms of broadening our understanding of how regulation of greenhouse gas emissions may differ between different plant groups, with implications across forested peatland ecosystems.

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Access to San San Pond Sak Wetland

The site itself is dominated by two plant species: Campnosperma panamensis, a broadleaved evergreen tree, and Raphia taedigera, a palm, and I aimed to assess whether differences in greenhouse gas fluxes between these species previously observed could be linked to differences in below ground release of root exudates, oxygen and decaying root material.

During both field campaigns I was based at the Smithsonian Tropical Research Institute research station on Isla Colon, a short boat ride away from my field sites on the mainland. On sampling days I, together with Erick Brown my field guide, would take a boat across the short stretch of the Caribbean to reach the wetland, before a short 1 km trek through the swamp forest to the field sites. The first week was particularly long and laborious, involving clearing a trail to the field site, making and then installing mesocosms into the soil. The average day of fieldwork involved collecting surface gas samples from the mesocosms and measuring a range of soil properties known to regulate gas fluxes (e.g. the height of the water table). CO2 and CH4 fluxes from these sites broadly match those measured in South East Asian Peatlands (400 – 800 mg CO2 m2 h-1 and 0.1 – 2 mg CH4 m2 h-1).

Work at the station involved tending to transplanted Campnosperma, Raphia and Symphonia globulifera saplings which towards the end of my fieldwork I labelled with 13CO2 with the aim of tracing recent photoassimilates into plant tissues, the soil microbial community and the production of CH4 through microbial use of plant derived carbon.

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Reaching field sites in San San Pond Sak