Soil organic carbon and nitrogen pools drive soil C-CO2 emissions from selected soils in Maritime Antarctica

摘要

The ongoing trend of increasing air temperatures will potentially affect soil organic matter (SOM) turnover and soil C-CO2 emissions in terrestrial ecosystems of Maritime Antarctica. The effects of SOM quality on this process remain little explored. We evaluated (i) the quantity and quality of soil organic matter and (ii) the potential of C release through CO_2 emissions in lab conditions in different soil types from Maritime Antarctica. Soil samples (0-10 and 10-20 cm) were collected in Keller Peninsula and the vicinity of Arctowski station, to determine the quantity and quality of organic matter and the potential to emit CO_2 under different temperature scenarios (2’ 5’ 8 and 11 °C) in lab. Soil organic matter mineralization is low, especially in soils with low organic C and Ν contents. Recalcitrant C form is predominant, especially in the passive pool, which is correlated with humic substances. Ornithogenic soils had greater C and Ν contents (reaching to 43.15 g kg-1 and 5.22 g kg-1 for total organic carbon and nitrogen, respectively). C and Ν were more present in the humic acid fraction. Lowest C mineralization was recorded from shallow soils on basaltic/andesites. C mineralization rates at 2 °C were significant lower than at higher temperatures. Ornithogenic soils presented the lowest values of C-CO_2 mineralized by g of C On the other hand, shallow soils on basaltic/andesites were the most sensitive sites to emit C-CO_2 by g of C. With permafrost degradation, soils on basaltic/andesites and sulfates are expected to release more C-CO_2 than ornithogenic soils. With greater clay contents, more protection was afforded to soil organic matter, with lower microbial activity and mineralization. The trend of soil temperature increases will favor C-CO_2 emissions, especially in the reduced pool of C stored and protected on permafrost, or in occasional Histosols.