Cushion bog plant community responses to passive warming in southern Patagonia

PANCOTTO V. A,; HOLL, DAVID; ESCOBAR, J; CASTAGNANI, FLORENCIA; KUTZBACH, LARS

BIOGEOSCIENCES

COPERNICUS PUBLICATIONS

Lugar: Gottingen; Año: 2021

1726-4170

Vascular plant-dominated cushion bogs, which are exclusive to the southern hemisphere, are highly productive and constitute large sinks for atmospheric carbon dioxide compared to their moss-dominated counterparts around the globe. In this study, we experimentally investigated how a cushion bog plant community responded to elevated surface temperature conditions as they are predicted to occur in a future climate. We conducted the study in a cushion bog dominated by Astelia pumila on Tierra del Fuego, Argentina. We installed a year-round passive warming experiment using semicircular plastic walls that raised average near-surface air temperatures between 0.4 °C and 0.7 °C (n = 3). We focused on characterizing differences in morphological cushion plant traits and in carbon dioxide exchange dynamics using chamber gas flux measurements. We used a mechanistic modeling approach to quantify physiological plant traits and to partition the net carbon dioxide flux into its two components photosynthesis and total ecosystem respiration. We found that A. pumila reduced its photosynthetic activity under elevated temperatures. At the same time, we observed enhanced respiration which we largely attribute, due to the limited effect of our passive warming on soil temperatures, to an increase in autotrophic respiration. Passively warmed A. pumila cushions sequestered between 55 % and 85 % less carbon dioxide than untreated control cushions over the main growing season. These results suggest that future warming could decrease the carbon sink function of austral cushion bogs.