Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation state and resulting recalcitrance. This recalcitrance allows peat to persist in the (sub)tropics despite warm temperatures. Because we observed similar declines in carbohydrate content with depth in high-latitude peat, our data explain recent field-scale deep peat warming experiments in which catotelm (deeper) peat remained stable despite temperature increases up to 9 °C. We suggest that high-latitude deep peat reservoirs may be stabilized in the face of climate change by their ultimately lower carbohydrate and higher aromatic composition, similar to tropical peats.
Bibliographical noteFunding Information:
This work was primarily funded by the US Department of Energy Office of Biological and Environmental Research under the Terrestrial Ecosystem Sciences program, under award DE-SC0012272 to Duke University and Florida State University. S.B.H. received additional funding from the NASA Interdisciplinary Studies in Earth Science program (Award # NNX17AK10G) and the US Department of Energy Office of Biological and Environmental Research under the Genomic Science program (Award DE-SC0016440). R.D. acknowledges financial support by Geo.X, the Research Network for Geosciences in Berlin and Potsdam. Funding for the sample collection and analysis at Stordalen was provided by the US Department of Energy Office of Biological and Environmental Research under the Genomic Science program (Awards DE-SC0004632 and DESC0010580). The S1 Bog was sampled and analyzed as part of the Spruce and Peatland Responses Under Climatic and Environmental Change (SPRUCE) experiment funded by the US Department of Energy, Office of Science, Office of Biological and Environmental Research, contract # DE-SC0012088. Collection of the Red Lake II cores was funded by NSF Award 0628647. Mer Bleue core collection was funded by the Natural Sciences and Engineering Research Council of Canada. Sample collection and radiocarbon dating of the Ulu Mendaram Conservation Area cores was supported by the National Research Foundation Singapore through the Singapore-MIT Alliance for Research and Technology’s Center for Environmental Sensing and Modeling interdisciplinary research program, and by the USA National Science Foundation under Grant Nos. 1114155 and 1114161 to C.F.H. We thank the Brunei Darussalam Heart of Borneo Center and the Brunei Darussalam Forestry Department for facilitation of field work and release of staff. Rahayu Sukmaria binti Haji Sukri, Watu bin Awok, Azlan Pandai, Rosaidi Mureh, Muhammad Wafiuddin Zainal Ariffin, Laure Gandois, Jangarun Eri, Fuu Ming Kai, Kamariah Abu Salim, Nur Salihah Haji Su’ut, Amy Chua, Jeffery Muli Incham, Haji Bohari bin Idi, and Ramasamy Zulkiflee assisted with collection of the Ulu Mendaram cores. We acknowledge the LacCore facility for their support and permanent core storage. We also thank the Abisko Scientific Research Station near Stordalen Mire, the USDA Forest Service at Marcell Experimental Forest, staff at the Pocosin Lakes National Wildlife Refuge, and the USFWS at Arthur R. Marshall Loxahatchee National Wildlife Refuge for access to these field sites and logistic support. Eun-Hae Kim, Tyler Logan, Carmody McCalley, and Kristina Solheim assisted with collection of the CPP core. Malak Tfaily provided FTIR data for the Zim Bog, S1 Bog, and Bog Lake Fen cores. Joseph Portio and Penn Carnice assisted with sample preparation and FTIR analysis, and Samantha Bosman assisted with radiocarbon analysis. Rachel Wilson provided helpful suggestions on the text. We thank Annika Kristoffersson for providing the temperature data from Abisko, Sweden. Earth surface temperature data in Fig. 1 were obtained from the NASA Langley Research Center Atmospheric Science Data Center Surface meteorological and Solar Energy (SSE) web portal supported by the NASA LaRC POWER Project.