Soil organic carbon storage in periglacial landforms of the Patagonian Andes

CHRISTINA I. FRÖJD; PETER KUHRY; IVANNA PECKER MARCOSIG; CHRISTOPHER R. SCHEER; DARIO TROMBOTTO L.

Wellington

Congreso; SouthCOP, Queenstown, 2019; 2019

University of Waikato

This study is part of a project thatinvestigates soil organic carbon (SOC) storage in the periglacial zone of theAndes of South America, in order to assess whether this region will represent asource or sink of carbon (positive or negative feedback) under conditions offuture global warming. In January 2019 we conducted field SOC inventories in twostudy areas located at latitudes 43-44 °S in the Patagonian Andes (Argentina). In total 27 soil profileswere collected along altitudinal and landscape gradients, which are in theprocess of being analysed for geochemical properties (dry bulk density, coarsefraction, %C, C/N ratios, and stable isotopes). The two mountain areas show asimilar altitudinal zonation, with the Nothofagus treeline located at c.1400-1500 m, and patches of alpine dwarfshrub and grassland extending up to c.1700-1800 m. Above these elevations, plant cover becomes very sparse, withpeaks at c.1900 and c. 2100 m having barren surfaces. Stabilized solifluctionterraces on gentle slopes between c. 1500-1700 m are most often characterizedby high plant cover, relatively deep soil profiles and (in some cases) evidenceof buried organic layers. At higher elevations small but active solifluctionlobes, sorted circles and stripes become prominent, with plant cover becomingsparse and soil profiles shallow. Permafrost terrain is restricted to active rockglaciers (with predominantly southern aspects) and the highest peaks (>2000m), with very sparse or no vegetation/soil development. Once geochemicalanalyses are completed (summer 2019), the SOC storage for each profile, themean SOC storage for each of the major land cover and landform classes, and themean SOC storage for the study areas as a whole, will be calculated. Upscalingfrom point observations to study area will be based on remotely sensed landcover and landform classifications corroborated by ground-truth pointscollected during the field season. Finally, we will evaluate the consequencesof an upward shift of vegetation/soil belts under global warming. Preliminaryobservations suggest that the periglacial and permafrost zones in thesemountain areas are characterized by very sparse plant cover with very low SOCstorage. A future upward shift of plant life zones will most likely represent anet total ecosystem carbon sink and, therefore, a negative feedback on globalwarming.