| 英文摘要: | Increasing temperatures are expected to increase decomposition rates in soils, potentially reducing ecosystem carbon storage. Research now indicates that — in a tropical montane forest — soil carbon stocks are unaffected by higher temperatures despite substantially increased rates of CO2 release from the soil. Soils contain more carbon than the atmosphere and all plant biomass combined. In short-term experiments (~1–10 years duration), warming has been shown to increase the rate at which this carbon is released from soils to the atmosphere. Therefore, as global temperatures increase, there are fears that more CO2 may be released to the atmosphere, further increasing temperatures, which in turn could result in more CO2 being released from soils, and so on. Writing in Nature Climate Change, Giardina et al.1 report that they have tested this important theory by investigating how soil carbon stocks changed with temperature along an altitudinal gradient on the eastern slope of the Mauna Kea volcano in Hawaii. Across this gradient, the tree species and soil type were relatively constant, providing an excellent opportunity to investigate how temperature affects soil carbon storage. Their results suggest that, while the initial stages of decomposition do indeed proceed faster in the warmer sites, this does not translate to any clear reduction in soil carbon stocks (Fig. 1). Furthermore, based on radiocarbon dating, Giardina et al.1 suggest that the lack of a change in soil carbon stocks is not simply caused by greater rates of soil organic matter decomposition in warmer soils being balanced out by greater soil carbon inputs from these more productive forests. The average age of the organic matter — which provides an indication of how quickly carbon cycles through a soil, referred to as its residence time — was not related to either temperature or forest productivity. Therefore, it seems that, across this altitudinal gradient, another factor is playing a more important role in controlling the amount of carbon stored in the soil.
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