Late Holocene Accumulation and Environmental Controls of Distichia muscoides Peatlands in the Andes of Colombia
Abstract
The long-term carbon (C) and vegetation dynamics of tropical high Andean peatlands are poorly understood. Here, we present radiocarbon-dated paleoecological records and modern microclimate data from high-elevation peatlands currently dominated by the cushion plant Distichia muscoides in the páramo (alpine tundra) of the Eastern Colombian Andes. Focusing on a well-dated 4300-year-old peat core from the Sierra Nevada del Cocuy, we investigated the response of peatland vegetation to hydroclimate changes and environmental controls on C accumulation. In addition, we carried out a regional synthesis of existing C accumulation data from northern Andean peatlands to place our new results in broad geographic and temporal context over the last 17,000 years. Our results show that the current Distichia-dominated peatlands are a recent landscape feature on El Cocuy occurring only during the last ~150 years. Furthermore, the Distichia peatlands have extremely high accumulation rates of up to 1 cm yr-1 with C accumulation rates between 270 and 900 g C m-2 yr-1 depending on the elevation of the site. This rate is higher than our calculated late Holocene average C accumulation rate of 48.6 g C m-2 yr-1 for northern Andean peatlands as a whole, suggesting that recent Distichia accumulation represents an acceleration of C accumulation at a rate higher than expected by autogenic ecological effects. In addition, before the modern warming period, our record indicates that Distichia cushions have only grown intermittently, often after the peatland flooded with mineral sediments. Mineral sediment depositions at 3290, 2590, 1620, 930, and 860 cal yr BP—which correspond with other lake-derived records of hydroclimate change in the northern Andes—indicate increases in precipitation and subsequent in-wash of mineral sediments. However, within the last 150 years, mineral sediment deposition has increased in frequency, likely due to warming-induced melting of snow and ice. Increased mineral nutrients, rising temperatures, and strong diurnal temperature contrast in the tropical mountains may explain the rapid C accumulation rates. Taken together, we show that Colombian alpine peatlands have experienced the largest shift in vegetation dominance and C accumulation rates in the last 150 years than any other time over the last 4000 years.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B22F..07B
- Keywords:
-
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0475 Permafrost;
- cryosphere;
- and high-latitude processes;
- BIOGEOSCIENCES;
- 4950 Paleoecology;
- PALEOCEANOGRAPHY