EGU General Assembly 2018

MÜNCHBERGER W,; REIMANN N; KNORR K; GALKA M; BORKEN W; BLODAU C,; PANCOTTO V. A,; KLEINEBECKER T

Viena

Congreso; EGU General Assembly 2018; 2018

EGU

South Patagonianpeatlands cover a wide range of the southern terrestrial area and have beenaccumulating organic material since the last deglaciation. These ecosystems are? in contrast to many northern hemisphere bogs ? virtually unaffected by humanactivities. Therefore, they provide excellent examples to study the functioningof undisturbed bog ecosystems. So far, little attention has been given to thesegreat carbon reservoirs. We aimed to investigate the below ground carboncycling patterns in two contrasting bog ecosystems in southern Patagonia,Tierra del Fuego.Sphagnum-dominated bogecosystems in Tierra del Fuego are similar to those on the northern hemisphere,while cushion plant-dominated (e.g. Asteliapumila, Donatia fascicularis) bogsare unique features of southern Patagonia. These cushion plant-dominated bogs arepredominantly located close to the coast while with increasing distance fromthe coast peatlands gradually change into Sphagnum-dominatedbogs. On the basis of 14C dates, up to 10000-year records from differentmicrosites in each bog type are presented. In order to understand the temporaland spatial variations in carbon cycling, we determined peat and carbonaccumulation rates by age-depth modelling and reconstructed the vegetationdevelopment from analyzed plant macrofossils. Further peat properties such as humificationindices obtained from FTIR spectra as well as carbon and nitrogen isotopicsignals were evaluated. While long-term peat accumulation rates were highly different betweenboth bog types, overall carbon accumulation rates were similar due to higher peatdensity under cushion forming vegetation. Initially, the cushion bog accumulated peat in similar ratescompared to the Sphagnum bog, but accumulation rates dropped when thevegetation composition changed about 3000 years ago from Sphagnum-dominated to cushion-dominated. Accordingly, the cushionpeat was much more decomposed and humification indices were higher compared tothe Sphagnum peat. Changes in carbon accumulation rates might be explained bymore labile litter and a dense, deep and aerenchymatic root biomass of A. pumila enhancing (secondary) decompositioneven in deeper Sphagnum peat layers. Ourresults demonstrate that vegetation composition strongly controls carboncycling not only of current surface peat layers but can also mask past dynamicsin buried peat layers composed of a different vegetation type. These resultsmay help to improve our understanding of ecosystem functioning in northern bogsthat are heavily disturbed by human impacts.