Carbon accumulation rates of Holocene peatlands in central–eastern Europe document the driving role of human impact over the past 4000 years

Jack Longman,Daniel Veres,Aritina Haliuc,Walter Finsinger,Tiberiu Sava,Daniela Pascal,Robert Begy,Vasile Ersek

doi:10.5194/cp-17-2633-2021

Abstract

Abstract. Peatlands are one of the largest terrestrial carbon sinks on the planet, yet little is known about the carbon accumulation rates (CARs) of mountainous peatlands. The long-term variability in the size of the associated carbon sink and its drivers remain largely unconstrained, especially when the long-term anthropogenic impact is also considered. Here, we present a composite CAR record of nine peatlands from central–eastern Europe (Romania and Serbia) detailing variability in the rates of carbon accumulation during the Holocene. We show examples of extremely high long-term rates of carbon accumulation (LORCA>120 gCm-2yr-1), indicating that mountain peatlands constitute an efficient regional carbon sink at times. By comparing our data to modelled palaeoclimatic indices and to measures of anthropogenic impact we disentangle the drivers of peat carbon accumulation in the area. Variability in early- and mid-Holocene CARs is linked to hydroclimatic controls, with high CARs occurring during the early Holocene and lower CARs associated with the transition to cooler and moister mid-Holocene conditions. By contrast, after 4000 years (calibrated) before present (years BP), the trends in CARs indicate a divergence from hydroclimate proxies, suggesting that other processes became the dominant drivers of peat CARs. We propose that enhanced erosion following tree cover reduction as well as increased rates of long-distance atmospheric dust fallout might have played a role, as both processes would result in enhanced mineral and nutrient supply to bog surfaces, stimulating peatland productivity. Surprisingly though, for the last 1000 years, reconstructed temperature is significantly correlated with CARs, with rising temperatures linked to higher CARs. Under future climate conditions, which are predicted to be warmer in the region, we predict that peat growth may expand but that this is entirely dependent upon the scale of human impact directly affecting the sensitive hydrological budget of these peatlands.

Highlights

Peatlands are some of the most proficient mediums for longterm carbon (C) sequestration in the terrestrial environment (Loisel et al, 2014), with the C sink in globally distributed peatlands estimated to be as high as ca. 600 Gt C
Using nine peatbog records from the Carpathians, we compiled a detailed record of changing carbon accumulation rates (CARs) through the Holocene
Our CAR data indicate that bogs located in the Carpathian Mountains are potentially very efficient carbon sinks, with long-term apparent CAR values that are amongst the highest in the published literature and that are comparable to high mountain bogs in South America

Summary

Introduction

Peatlands are some of the most proficient mediums for longterm carbon (C) sequestration in the terrestrial environment (Loisel et al, 2014), with the C sink in globally distributed peatlands estimated to be as high as ca. 600 Gt C Model-derived estimates of future climatic change suggest that peatlands will act as an efficient carbon sink as climate warms (GallegoSala et al, 2018), as observed in reconstructions of warm periods in Earth’s past (Treat et al, 2019). This conclusion is far from certain, as land-use-driven degradation of peat since the 1960s has led to peatlands acting as a net source of carbon (Leifeld et al, 2019). Greater land exploitation leads to enhanced carbon release, so this trend will likely continue as human pressure on land use is expected to increase (Kaplan et al, 2011; Ruddiman and Ellis, 2009)

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