Recent significant decline of strong carbon peat accumulation rates in tropical Andes related to climate change and glacier retreat [preprint]

2022

Littérature grise

Llanos Romina, Moreira-Turcq Patricia, Turcq Bruno, Espinoza Villar Raúl, Huaman Yizet, Condom Thomas, Willems Bram

Biogeosciences Discussions, 2022, 22 février, bg-2022-47 [19 p.]

Climate change has altered precipitation and temperature patterns in the tropical Andes. As a result, tropical glaciers have retreated significantly over the past 50 years and have even disappeared in some areas. Andean peatlands, one of the most important Andean carbon reservoirs, also seem to be affected by these climate changes, since glaciers have been recognized as one of their vital water sources. Here, we point out the important role of Andean peatlands on carbon accumulation rates (CAR), one of the highest in the world, and the impact of climate on carbon storage over the last 65 years, using four peat cores. The peat cores were radiocarbon-dated and ages were post-bomb calibrated and chronological models indicated basal ages (30 cm depth) ranging from 1957 to 1972 CE, where accumulation rates reached up 1.7 cm yr?1. For both peatlands, carbon accumulation rates are high (mean of 470 and 220 g C m?2 yr?1 at APA 1 and APA 2 sites, respectively) and can reach up to 1010 g C m?2 yr?1. Distichia muscoides is the dominant species in the Peruvian Central Andes peatlands and the high CAR, among other factors, is a characteristic of this species. Our results point out that a marked decrease of CAR after the early 1980s at both peatlands is likely related to an increase in annual temperature, which is responsible for the retreat of glaciers. We use a new high-resolution proxy (Skrzypek et al., 2011) based on the ?13C of Distichia along the cores to evaluate the temperature variability at the site. We observed a general trend of increase in the reconstructed temperature from both studied peatlands from 1.9 to 2 ºC for the period 1970-2015 CE. Comparison with air temperature data from the NCEP-NCAR reanalysis for the higher resolution cores shows a good relationship and an increase of 2.15 °C for the same period. Temperature increase may directly affect CAR by an increase in organic matter degradation rates. The decrease in CAR during the period of study may also be due to a decrease in melt water inflow generated by the retreat of glaciers that have almost disappeared today in the catchments as a consequence of regional warming. Our findings emphasize that marked changes in carbon accumulation rates demonstrate the high ecological sensitivity of tropical high-Andean peatlands, endangering their outstanding role in the regional (and even global) C cycle as large C sinks that contribute to the mitigation of global climate change.

Sciences du milieu [021] ; Ecologie, systèmes aquatiques [036] ; Géologie et formations superficielles [064]

Fonds IRD [F B010085050]

fdi:010085050