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

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.

Mountain Peatlands and Drought: Carbon Cycling in the Pyrenees Amidst Global Climate Change

“…The Bernadouze peatland has been, on average, a modest carbon sink in the past millennium. The LORCA value reported for this site is lower than the average value reported for temperate peatlands, 26.1 ± 1.47 gCm −2 .yr −1 (Charman et al., 2013), or more recently for several peatlands in central‐Eastern Europe with an average of 21 gCm −2 .yr −1 (Longman et al., 2021). This mountain peatland show similar LORCA to boreal peatlands, that exhibit values ranging from 13 to 35 gCm −2 .yr −1 (Loisel et al., 2014; Loisel & Yu, 2013; Primeau & Garneau, 2021; Ratcliffe et al., 2018; Turunen, 2003).…”

“…The Bernadouze peatland has been, on average, a modest carbon sink in the past millennium. The LORCA value reported for this site is lower than the average value reported for temperate peatlands, 26.1 ± 1.47 gCm 2 .yr 1 (Charman et al, 2013), or more recently for several peatlands in central-Eastern Europe with an average of 21 gCm 2 .yr 1 (Longman et al, 2021) Garneau, 2021;Ratcliffe et al, 2018;Turunen, 2003). In contrast to LORCA, the RERCA values for Bernadouze reveal much higher rates of C accumulation, ranging from 48.5 to 72.1 gCm 2 .yr 1 .…”