106 research outputs found
Impact of deforestation on solid and dissolved organic matter characteristics of tropical peat forests: implications for carbon release
This study compares the organic chemistry of peat beneath one of last remaining pristine tropical peat forests in Southeast Asia with a neighbouring peat dome that has been deforested, but not intentionally drained, in the Belait district of Brunei Darussalam, Borneo. We characterized the solid and dissolved organic matter collected from the two domes, through a combination of methods including elemental analysis, phenolic content and Fourier transform infrared spectroscopy (FTIR) investigation of solid peat, as well as optical characterisation (absorbance, fluorescence) of dissolved organic matter (DOM). The peat had a high content of lignin, consistent with its origin from the Shorea albida trees on the domes. Dissolved organic carbon (DOC) concentration in the pore water was significantly greater in the deforested site (79.9 ± 5.5 mg l[superscript â1]) than the pristine site (62.2 ± 2.2 mg l[superscript â1]). The dissolved organic matter was richer in nitrogen and phenolics in the deforested site. The optical properties (Fluorescence Index) indicated a modification of DOM cycling in the deforested site (enhanced decomposition of the peat and fresh litter). Comparison of the solid peat composition between the two sites also suggests effects of deforestation: sulphur, nitrogen and phenolic contents were higher in the deforested site. Taken together, these observations are consistent with peat enhanced decomposition in the deforested site, even without engineered drainage.Singapore-MIT Alliance for Research and Technology. Center for Environmental Sensing and Modelin
Introducing global peat-specific temperature and pH calibrations based on brGDGT bacterial lipids
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Glycerol dialkyl glycerol tetraethers (GDGTs) are membrane-spanning lipids from
Bacteria and Archaea that are ubiquitous in a range of natural archives and especially
abundant in peat. Previous work demonstrated that the distribution of bacterial
branched GDGTs (brGDGTs) in mineral soils is correlated to environmental factors
such as mean annual air temperature (MAAT) and soil pH. However, the influence of
these parameters on brGDGT distributions in peat is largely unknown. Here we
investigate the distribution of brGDGTs in 470 samples from 96 peatlands around the
world with a broad mean annual air temperature (â8 to 27 °C) and pH (3â8) range and
present the first peat-specific brGDGT-based temperature and pH calibrations. Our
results demonstrate that the degree of cyclisation of brGDGTs in peat is positively
correlated with pH, pH = 2.49 x CBTpeat + 8.07 (n = 51, R2 65 = 0.58, RMSE = 0.8) and
the degree of methylation of brGDGTs is positively correlated with MAAT,
MAATpeat (°C) = 52.18 x MBT5meâ â 23.05 (n = 96, R2 67 = 0.76, RMSE = 4.7 °C).
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These peat-specific calibrations are distinct from the available mineral soil
calibrations. In light of the error in the temperature calibration (~ 4.7 °C), we urge
caution in any application to reconstruct late Holocene climate variability, where the
climatic signals are relatively small, and the duration of excursions could be brief.
Instead, these proxies are well-suited to reconstruct large amplitude, longer-term
shifts in climate such as deglacial transitions. Indeed, when applied to a peat deposit
spanning the late glacial period (~15.2 kyr), we demonstrate that MAATpeat yields
absolute temperatures and relative temperature changes that are consistent with those
from other proxies. In addition, the application of MAATpeat to fossil peat (i.e.
lignites) has the potential to reconstruct terrestrial climate during the Cenozoic. We
conclude that there is clear potential to use brGDGTs in peats and lignites to
reconstruct past terrestrial climateThis research was funded through the advanced ERC grant âthe greenhouse earth
systemâ (T-GRES, project reference 340923), awarded to RDP. All authors are part of
the âT-GRES Peat Database collaboratorsâ collective. RDP also acknowledges the
Royal Society Wolfson Research Merit Award. We thank D. Atkinson for help with
the sample preparation. We acknowledge support from Labex VOLTAIRE (ANR-10-
22
LABX-100-01). Peat from Patagonia and Tierra del Fuego were collected thanks to a
Young Researcher Grant of the Agence National de la Recherche (ANR) to FDV,
project ANR-2011-JS56-006-01 âPARADâ and with the help of Ramiro Lopez,
Andrea Coronato and Veronica Pancotto (CADIC-CONICET, Ushuaia). Peat from
Brazil was collected with the context of CNPq project 482815/2011-6. Samples from
France (Frasne and La Guette) were collected thanks to the French Observatory of
Peatlands. The Canadian peat was collected in the context of the NSERC-Discovery
grant of L. Rochefort. Peats from China were obtained under a National Natural
Science Foundation of China grant (No. 41372033), awarded to Y. Zheng
Introducing global peat-specific temperature and pH calibrations based on brGDGT bacterial lipids
Glycerol dialkyl glycerol tetraethers (GDGTs) are membrane-spanning lipids from Bacteria and Archaea that are ubiquitous in a range of natural archives and especially abundant in peat. Previous work demonstrated that the distribution of bacterial branched GDGTs (brGDGTs) in mineral soils is correlated to environmental factors such as mean annual air temperature (MAAT) and soil pH. However, the influence of these parameters on brGDGT distributions in peat is largely unknown. Here we investigate the distribution of brGDGTs in 470 samples from 96 peatlands around the world with a broad mean annual air temperature (-8 to 27 degrees C) and pH (3-8) range and present the first peat-specific brGDGT-based temperature and pH calibrations. Our results demonstrate that the degree of cyclisation of brGDGTs in peat is positively correlated with pH, pH = 2.49 x CBTpeat + 8.07 (n = 51, R-2 = 0.58, RMSE = 0.8) and the degree of methylation of brGDGTs is positively correlated with MAAT, MAAT(peat) (degrees C) = 52.18 x MBT'(5me) - 23.05 (n = 96, R-2 = 0.76, RMSE = 4.7 degrees C). These peat-specific calibrations are distinct from the available mineral soil calibrations. In light of the error in the temperature calibration (similar to 4.7 degrees C), we urge caution in any application to reconstruct late Holocene climate variability, where the climatic signals are relatively small, and the duration of excursions could be brief. Instead, these proxies are well-suited to reconstruct large amplitude, longer-term shifts in climate such as deglacial transitions. Indeed, when applied to a peat deposit spanning the late glacial period (similar to 15.2 kyr), we demonstrate that MAAT(peat) yields absolute temperatures and relative temperature changes that are consistent with those from other proxies. In addition, the application of MAAT(peat) to fossil peat (i.e. lignites) has the potential to reconstruct terrestrial climate during the Cenozoic. We conclude that there is clear potential to use brGDGTs in peats and lignites to reconstruct past terrestrial climate. (C) 2017 The Authors. Published by Elsevier Ltd
C mobilisation in disturbed tropical peat swamps: old DOC can fuel the fluvial efflux of old carbon dioxide, but site recovery can occur
Southeast-Asian peat swamp forests have been significantly logged and converted to plantation. Recently, to mitigate land degradation and C losses, some areas have been left to regenerate. Understanding how such complex land use change affects greenhouse gas emissions is essential for modelling climate feedbacks and supporting land management decisions. We carried out field research in a Malaysian swamp forest and an oil palm plantation to understand how clear-felling, drainage, and illegal and authorized conversion to oil palm impacted the C cycle, and how the C cycle may change if such logging and conversion stopped. We found that both the swamp forest and the plantation emit centuries-old CO2 from their drainage systems in the managed areas, releasing sequestered C to the atmosphere. Oil palm plantations are an iconic symbol of tropical peatland degradation, but CO2 efflux from the recently-burnt, cleared swamp forest was as old as from the oil palm plantation. However, in the swamp forest site, where logging had ceased approximately 30 years ago, the age of the CO2 efflux was modern, indicating recovery of the system can occur. 14C dating of the C pool acted as a tracer of recovery as well as degradation and offers a new tool to assess efficacy of restoration management. Methane was present in many sites, and in higher concentrations in slow-flowing anoxic systems as degassing mechanisms are not strong. Methane loading in freshwaters is rarely considered, but this may be an important C pool in restored drainage channels and should be considered in C budgets and losses
Impact of Local Human Activities on Dissolved Organic Carbon Export from Peatlands-a Global Review
International audienc
Impact of Local Human Activities on Dissolved Organic Carbon Export from Peatlands-a Global Review
International audienc
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