Deforestation for agriculture leads to soil warming and enhanced litter decomposition in subarctic soils

[摘要] The climate-change-induced poleward shift of agriculture could lead toenforced deforestation of subarctic forest. Deforestation alters themicroclimate and, thus, soil temperature, which is an important driver ofdecomposition. The consequences of land-use change on soil temperature anddecomposition in temperature-limited ecosystems are not well understood. Inthis study, we buried tea bags together with soil temperature loggers at twodepths (10 and 50 cm) in native subarctic forest soils and adjacentagricultural land in the Yukon Territory, Canada. A total of 37 plots wasestablished on a wide range of different soils and resampled after 2 yearsto quantify the land-use effect on soil temperature and decomposition offresh organic matter. Average soil temperature over the whole soil profilewas 2.1  ±  1.0 and 2.0  ±  0.8  ∘ C higher incropland and grassland soils compared to forest soils. Cumulative degreedays (the annual sum of daily mean temperatures >  0  ∘ C)increased significantly by 773  ±  243 (cropland) and 670  ±  285(grassland). Litter decomposition was enhanced by 2.0  ±  10.4 % and7.5  ±  8.6  % in cropland topsoil and subsoil compared to forestsoils, but no significant difference in decomposition was found betweengrassland and forest soils. Increased litter decomposition may be attributed not onlyto increased temperature but also to management effects,such as irrigation of croplands. The results suggest thatdeforestation-driven temperature changes exceed the soil temperatureincrease that has already been observed in Canada due to climate change. Deforestationthus amplifies the climate–carbon feedback by increasing soil warming andorganic matter decomposition.

[学科分类] 大气科学