Rapid deglacial and early Holocene expansion of peatlands in Alaska
230
Citation
61
Reference
10
Related Paper
Citation Trend
Abstract:
Northern peatlands represent one of the largest biospheric carbon (C) reservoirs; however, the role of peatlands in the global carbon cycle remains intensely debated, owing in part to the paucity of detailed regional datasets and the complexity of the role of climate, ecosystem processes, and environmental factors in controlling peatland C dynamics. Here we used detailed C accumulation data from four peatlands and a compilation of peatland initiation ages across Alaska to examine Holocene peatland dynamics and climate sensitivity. We find that 75% of dated peatlands in Alaska initiated before 8,600 years ago and that early Holocene C accumulation rates were four times higher than the rest of the Holocene. Similar rapid peatland expansion occurred in West Siberia during the Holocene thermal maximum (HTM). Our results suggest that high summer temperature and strong seasonality during the HTM in Alaska might have played a major role in causing the highest rates of C accumulation and peatland expansion. The rapid peatland expansion and C accumulation in these vast regions contributed significantly to the peak of atmospheric methane concentrations in the early Holocene. Furthermore, we find that Alaskan peatlands began expanding much earlier than peatlands in other regions, indicating an important contribution of these peatlands to the pre-Holocene increase in atmospheric methane concentrations.Peatlands provide a widespread terrestrial archive of Holocene environmental change. The taphon omy of peat is relatively simple, the range of evidence and proxies is wide, and dating methods have become more accurate and precise, such that the potential temporal resolution of records is high. Although long estab lished, the use of peatlands as archives of Holocene change has undergone phases of decline and resurgence. Here, the variable exploitation of the peat archive is explored, and recent developments in peatland science as applied to Holocene records are reviewed with reference to the collection of papers in this Special Issue of The Holocene, which are arranged in four key themes: (1) records of Holocene climatic change; (2) peatland dynamics; (3) carbon accumulation; and (4) implications for conservation and management. The changing acceptance of peatlands as archives of Holocene climatic change is attributed to developments in understanding of the peatland system and geographical differences in the history of Holocene research. Recent developments in biological and geochemical proxies combined with improvements in chronological techniques have resulted in renewed interest in peatland palaeoclimate records. Peatlands are an important global carbon pool and it is clear that climate has influenced the efficiency of long-term carbon sequestration by these systems. Climate has also had an impact on the biodiversity and condition of peatlands, which creates problems in discerning cause and effect in sites affected by human activities, and in targeting remedial management. It is concluded that particular strengths of the archive are the current diversity of peat-based palaeoenvironmental research and the potential for multiproxy analyses to be applied to a range of research issues. Mire-based investigations can complement research in other realms, and are deserving of greater attention from researchers of other archives.
Environmental change
Cite
Citations (142)
Abstract A high‐resolution study of bulk properties in a peat sequence from the Xinjiang Altai Mountains of northwestern China has allowed reconstruction of local variations in peat properties and peat C and N accumulation rates (CAR and NAR) during the Holocene. Analyses of peat bulk density, loss on ignition, and concentrations of total organic carbon (TOC) and total nitrogen (TN) and their elemental ratios and stable isotopic values suggest that changes in peat‐forming vegetation types during different parts of this epoch are the major factors responsible for the variations of peat properties in this sequence. The long‐term peat CAR has been 25.4 ± 7.7 (SD) g C/m 2 /yr, with lower values during the early Holocene and higher accumulations during the late Holocene, which is opposite to the Holocene variations in CAR in other northern peatlands. In contrast, the long‐term peat NAR is 1.5 ± 0.5 (SD) g N/m 2 /yr and is higher during the early and middle Holocene and lower during the late Holocene as in other northern peatlands. However, unlike other northern peatlands, long‐term peat NAR does not vary with the CAR, which is influenced by the peat density and accumulation rate. Variations in long‐term peat C and N accumulations in the Altai Mountains can be attributed to changes in primary productivity, in the dominant plant types and in peat decomposition caused by changes in both regional Holocene climate and local conditions.
Cite
Citations (6)
Ombrotrophic
Deposition
Cite
Citations (27)
Carbon fibers
Cite
Citations (24)
Northern peatlands represent one of the largest biospheric carbon (C) reservoirs; however, the role of peatlands in the global carbon cycle remains intensely debated, owing in part to the paucity of detailed regional datasets and the complexity of the role of climate, ecosystem processes, and environmental factors in controlling peatland C dynamics. Here we used detailed C accumulation data from four peatlands and a compilation of peatland initiation ages across Alaska to examine Holocene peatland dynamics and climate sensitivity. We find that 75% of dated peatlands in Alaska initiated before 8,600 years ago and that early Holocene C accumulation rates were four times higher than the rest of the Holocene. Similar rapid peatland expansion occurred in West Siberia during the Holocene thermal maximum (HTM). Our results suggest that high summer temperature and strong seasonality during the HTM in Alaska might have played a major role in causing the highest rates of C accumulation and peatland expansion. The rapid peatland expansion and C accumulation in these vast regions contributed significantly to the peak of atmospheric methane concentrations in the early Holocene. Furthermore, we find that Alaskan peatlands began expanding much earlier than peatlands in other regions, indicating an important contribution of these peatlands to the pre-Holocene increase in atmospheric methane concentrations.
Cite
Citations (230)
Cite
Citations (89)
Cite
Citations (30)
Abstract This paper summarizes the present knowledge on the variation of summer temperatures in the European Alps throughout the Holocene by combining the results of an extraordinary archaeological find with the information gathered from glacier and tree-line movements. As it turns out, there were several distinct periods were the glaciers were smaller than today, allowing in some periods the growth of trees in areas, which even now are still covered with ice. On average, the first half of the Holocene was warmer than the second half, with temperatures starting to decrease around the time of the Iceman some 5000 yr ago. One of the coldest periods during the Holocene, the so-called Little Ice Age (LIA), lasted from about AD 1300 to 1850. It is well known that since then the Alpine glaciers have been receding, most likely amplified by anthropogenic impact. The study of temperature variations before human influence may help to eventually disentangle natural and anthropogenic causes for the global warming of our time.
Tree line
Holocene climatic optimum
Ice core
Little ice age
Cite
Citations (13)
This paper proposes a novel approach using basal peat ages and carbon (C) accumulation profiles from the world’s major peatland regions to decompose C flux terms from time-dependent C pool data observed from peat cores. Our peat-data syntheses show that the total peat C pools are 547 GtC, 50 GtC, and 15 GtC for northern, tropical and southern peatlands, respectively. The modeled net C balance (NCB) has a mean value of 41.8 TgC/yr for northern peatlands during the Holocene, ranging from 83.1 TgC/yr in the early Holocene around 9 ka (1 ka = 1000 cal. yr BP) to 21.5 TgC/yr around 2 ka, a temporal pattern mostly owing to the delayed effect of long-term decay of previously accumulated peat C. NCB from tropical and southern peatlands represents much smaller terms, mostly less than 10 TgC/yr. Northern peatlands represent about 90% of global total peatland C pool of 612 GtC and >90% of global peatland NCB. Our bottom-up global peatland synthesis indicates a decrease in rates of peatland area expansion and reduced CH 4 emissions during the late Holocene, thus lending support for an anthropogenic source of late-Holocene CH 4 rise. The C balance analysis of global peatland data indicates a cumulative net C uptake of 272 GtC in the early Holocene (11–7 ka), 151 GtC at 7–4 ka, and 116 GtC after 4 ka. The large cumulative fluxes and significant variations throughout the Holocene could greatly contribute to the observed atmospheric CO 2 and δ 13 CO 2 patterns derived from Antarctic ice cores. Thus, global mass-balance calculations or climate–carbon cycle simulations have to consider these large net C uptake terms from global peatlands and their variations over the Holocene.
Cite
Citations (253)
Macrofossil
Ombrotrophic
Sphagnum
Testate amoebae
Cite
Citations (34)