18 research outputs found
Technical note: Skirt chamber â an open dynamic method for the rapid and minimally intrusive measurement of greenhouse gas emissions from peatlands
We present a reliable and robust open dynamic chamber for
measuring greenhouse gas exchange in peatlands with minimal disturbance of
the ground. This chamber, called the âskirt chamberâ, is based on a
transparent plastic film placed above an open frame made of sparse
interwoven wires and expanded around the base of the chamber below a steel
chain that ensures contact to the ground, avoiding damage, trenching, and
cutting vegetation. Gas exchange is determined using a portable gas analyzer
from a mass balance in which the imperfect sealing of the chamber to the
ground is quantified through the injection of a methane pulse. The method was
tested on a pristine peatland dominated by Sphagnum magellanicum located on Navarino Island in
the subantarctic Magellanic ecoregion in Chile. Our results indicate that
the skirt chamber allowed the determination of methane fluxes and ecosystem
respiration in about 20âmin, with a limit of detection of 0.185âmg
CH4âmâ2âhâ1 and 173âmg CO2âmâ2âhâ1,
respectively. We conclude that the skirt chamber is a minimally intrusive,
fast, portable, and inexpensive method that allows the quantification of
greenhouse gas emissions with high spatial resolution in remote locations
and without delay.</p
Tropical wetlands: A missing link in the global carbon cycle?
Tropical wetlands are not included in Earth system models, despite being an important source of methane (CH4) and contributing a large fraction of carbon dioxide (CO2) emissions from land use, land use change, and forestry in the tropics. This review identifies a remarkable lack of data on the carbon balance and gas fluxes from undisturbed tropical wetlands, which limits the ability of global change models to make accurate predictions about future climate. We show that the available data on in situ carbon gas fluxes in undisturbed forested tropical wetlands indicate marked spatial and temporal variability in CO2 and CH4 emissions, with exceptionally large fluxes in Southeast Asia and the Neotropics. By upscaling short-term measurements, we calculate that approximately 90â±â77 Tg CH4 yearâ1 and 4540â±â1480 Tg CO2 yearâ1 are released from tropical wetlands globally. CH4 fluxes are greater from mineral than organic soils, whereas CO2 fluxes do not differ between soil types. The high CO2 and CH4 emissions are mirrored by high rates of net primary productivity and litter decay. Net ecosystem productivity was estimated to be greater in peat-forming wetlands than on mineral soils, but the available data are insufficient to construct reliable carbon balances or estimate gas fluxes at regional scales. We conclude that there is an urgent need for systematic data on carbon dynamics in tropical wetlands to provide a robust understanding of how they differ from well-studied northern wetlands and allow incorporation of tropical wetlands into global climate change models
Greenhouse gas emissions resulting from conversion of peat swamp forest to oil palm plantation.
Conversion of tropical peat swamp forest to drainage-based agriculture alters greenhouse gas (GHG) production, but the magnitude of these changes remains highly uncertain. Current emissions factors for oil palm grown on drained peat do not account for temporal variation over the plantation cycle and only consider CO2 emissions. Here, we present direct measurements of GHGs emitted during the conversion from peat swamp forest to oil palm plantation, accounting for CH4 and N2O as well as CO2. Our results demonstrate that emissions factors for converted peat swamp forest is in the range 70-117 t CO2 eq ha-1 yr-1 (95% confidence interval, CI), with CO2 and N2O responsible for ca. 60 and ca. 40% of this value, respectively. These GHG emissions suggest that conversion of Southeast Asian peat swamp forest is contributing between 16.6 and 27.9% (95% CI) of combined total national GHG emissions from Malaysia and Indonesia or 0.44 and 0.74% (95% CI) of annual global emissions
Improving estimates of tropical peatland area, carbon storage, and greenhouse gas fluxes
The workshops that led to this article were supported financially by the Universities of Leicester and Nottingham, and the Natural Environment Research Council-funded âEarth Observation Technology Clusterâ knowledge exchange initiativeOur limited knowledge of the size of the carbon pool and exchange fluxes in forested lowland tropical peatlands represents a major gap in our understanding of the global carbon cycle. Peat deposits in several regions (e.g. the Congo Basin, much of Amazonia) are only just beginning to be mapped and characterised. Here we consider the extent to which methodological improvements and improved coordination between researchers could help to fill this gap. We review the literature on measurement of the key parameters required to calculate carbon pools and fluxes, including peatland area, peat bulk density, carbon concentration, above-ground carbon stocks, litter inputs to the peat, gaseous carbon exchange, and waterborne carbon fluxes. We identify areas where further research and better coordination are particularly needed in order to reduce the uncertainties in estimates of tropical peatland carbon pools and fluxes, thereby facilitating better-informed management of these exceptionally carbon-rich ecosystems.PostprintPeer reviewe
Climateâdriven spatial and temporal patterns in peatland pool biogeochemistry
Peatland pools are freshwater bodies that are highly dynamic aquatic ecosystems because of their small size and their development in organic-rich sediments. However, our ability to understand and predict their contribution to both local and global biogeochemical cycles under rapidly occurring environmental change is limited because the spatiotemporal drivers of their biogeochemical patterns and processes are poorly understood. We used (1) pool biogeochemical data from 20 peatlands in eastern Canada, the United Kingdom, and southern Patagonia and (2) multi-year data from an undisturbed peatland of eastern Canada, to determine how climate and terrain features drive the production, delivering and processing of carbon (C), nitrogen (N), and phosphorus (P) in peatland pools. Across sites, climate (24%) and terrain (13%) explained distinct portions of the variation in pool biogeochemistry, with climate driving spatial differences in pool dissolved organic C (DOC) concentration and aromaticity. Within the multi-year dataset, DOC, carbon dioxide (CO2), total N concentrations, and DOC aromaticity were highest in the shallowest pools and at the end of the growing seasons, and increased gradually from 2016 to 2021 in relation to a combination of increases in summer precipitation, mean air temperature for the previous fall, and number of extreme summer heat days. Given the contrasting effects of terrain and climate, broad-scale terrain characteristics may offer a baseline for the prediction of small-scale pool biogeochemistry, while broad-scale climate gradients and relatively small year-to-year variations in local climate induce a noticeable response in pool biogeochemistry. These findings emphasize the reactivity of peatland pools to both local and global environmental change and highlight their potential to act as widely distributed climate sentinels within historically relatively stable peatland ecosystems
Root exudate analogues accelerate CO 2 and CH 4 production in tropical peat
Root exudates represent a large and labile carbon input in tropical peatlands, but their contribution to carbon dioxide (CO2) and methane (CH4) production remains poorly understood. Changes in species composition and productivity of peatland plant communities in response to global change could alter both inputs of exudates and associated greenhouse gas emissions. We used manipulative laboratory incubations to assess the extent to which root exudate quantity and chemical composition drives greenhouse gas emissions from tropical peatlands. Peat was sampled from beneath canopy palms (Raphia taedigera) and broadleaved evergreen trees (Campnosperma panamensis) in an ombrotrophic wetland in Panama. Root exudate analogues comprising a mixture of sugars and organic acids were added in solution to peats derived from both species, with CO2 and CH4 measured over time. CO2 and CH4 production increased under most treatments, but the magnitude and duration of the response depended on the composition of the added labile carbon mixture rather than the quantity of carbon added or the botanical origin of the peat. Treatments containing organic acids increased soil pH and altered other soil properties including redox potential but did not affect the activities of extracellular hydrolytic enzymes. CO2 but not CH4 production was found to be linearly related to microbial activity and redox potential. Our findings demonstrate the importance of root exudate composition in regulating greenhouse gas fluxes and propose that in situ plant species changes, particularly those associated with land use change, may account for small scale spatial variation in CO2 and CH4 fluxes due to species specific root exudate compositions
Impacts of conversion of tropical peat swamp forest to oil palm plantation on peat organic chemistry, physical properties and carbon stocks
Ecosystem services provided by tropical peat swamp forests, such as carbon (C) storage and water regulation, are under threat due to encroachment and replacement of these natural forests by drainage-based agriculture, commonly oil palm plantation. This study aims to quantify how the chemical and physical properties of peat change during land conversion to oil palm. This will be addressed by comparing four separate stages of conversion; namely, secondary peat swamp forests, recently deeply drained secondary forests, cleared and recently planted oil palm, and mature oil palm plantation in North Selangor, Malaysia. Results indicate accelerated peat decomposition in surface peats of mature oil palm plantations due to the lowered water table and altered litter inputs associated with this land-use change. Surface organic matter content and peat C stocks at secondary forest sites were higher than at mature oil palm sites (e.g. C stocks were 975 ± 151 and 497 ± 157 Mg haâ 1 at secondary forest and mature oil palm sites, respectively). Land conversion altered peat physical properties such as shear strength, bulk density and porosity, with mirrored changes above and below the water table. Our findings suggest close links between the organic matter and C content and peat physical properties through the entire depth of the peat profile. We have demonstrated that conversion from secondary peat swamp forest to mature oil palm plantation may seriously compromise C storage and, through its impact on peat physical properties, the water holding capacity in these peatlands
Data from: Evaluation of vegetation communities, water table, and peat composition as drivers of greenhouse gas emissions in lowland tropical peatlands
The data set contains CH4 and CO2 fluxes from the surface of six peatlands inhabited by two distinct vegetation communities (i.e., Raphia taedigera and Campnosperma panamensis). The data set also includes the water table position for all the monitoring events that were conducted throughout one year period. An additional data set includes CH4, CO2, and N2O fluxes from the surface of two peatlands with two distinct vegetation communities (i.e., Raphia taedigera and Campnosperma panamensis) under a nutrient addition experiment (i.e., Control (C), Nitrogen (N), Phosphorus (P), and Nitrogen + Phosphorus (N+P))
The impact of anthropogenic pollution on limnological characteristics of a subtropical highland reservoir â
âLago de Guadalupeâ is an important freshwater ecosystem located in the
northern part of the metropolitan area surrounding Mexico City, under high demographic
pressure. It receives approximately 15 hm3·y-1 of untreated
municipal wastewater from the surrounding municipalities. In order to develop a
comparative assessment of the pollution effect over the limnological characteristics of
Lago de Guadalupe, this lake was characterised from February 2006 to
July 2009, and the results were compared with those obtained from a non-polluted lake
âLago el Llanoâ located in the same drainage area. Lago de
Guadalupe was hypereutrophic with anoxic conditions throughout most of the
water column. In contrast, Lago el Llano was mesotrophic with high
dissolved oxygen concentrations throughout the entire water column with a clinograde
profile. Both reservoirs had a monomictic mixing regime. The longitudinal zonation of
physicochemical and biological variables were investigated in order to better understand
the processes controlling the water quality across the reservoir during its residence
time. This study shows the impact of anthropogenic pollution on the limnological
characteristics of a subtropical reservoir and confirms that under adequate management
schemes, namely avoiding pollution and wastewater discharges, subtropical reservoirs can
be prevented from developing eutrophic conditions
The impact of anthropogenic pollution on limnological characteristics of a subtropical highland reservoir âLago de Guadalupeâ, Mexico
âLago de Guadalupeâ is an important freshwater ecosystem located in the
northern part of the metropolitan area surrounding Mexico City, under high demographic
pressure. It receives approximately 15 hm3·y-1 of untreated
municipal wastewater from the surrounding municipalities. In order to develop a
comparative assessment of the pollution effect over the limnological characteristics of
Lago de Guadalupe, this lake was characterised from February 2006 to
July 2009, and the results were compared with those obtained from a non-polluted lake
âLago el Llanoâ located in the same drainage area. Lago de
Guadalupe was hypereutrophic with anoxic conditions throughout most of the
water column. In contrast, Lago el Llano was mesotrophic with high
dissolved oxygen concentrations throughout the entire water column with a clinograde
profile. Both reservoirs had a monomictic mixing regime. The longitudinal zonation of
physicochemical and biological variables were investigated in order to better understand
the processes controlling the water quality across the reservoir during its residence
time. This study shows the impact of anthropogenic pollution on the limnological
characteristics of a subtropical reservoir and confirms that under adequate management
schemes, namely avoiding pollution and wastewater discharges, subtropical reservoirs can
be prevented from developing eutrophic conditions