Summer drought reduces total and litter-derived soil CO2 effluxes in temperate grassland - clues from a 13C litter addition experiment
Summer drought reduces total and litter-derived soil CO2 effluxes in temperate grassland - clues from a 13C litter addition experiment
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DOI：
10.5194/bg-7-1031-2010
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发表时间：
2010-01-01
期刊：
影响因子：
4.9
通讯作者：
Buchmann, N.
中科院分区：
文献类型：
--
作者：
Joos, O.;Hagedorn, F.;Buchmann, N.
目前的气候变化模型预测，整个欧洲的降雨模式将发生重大变化。为了探索干旱对土壤二氧化碳排放(F土)的影响以及凋落物对F土的贡献，我们使用雨棚模拟了瑞士集约化管理草原上的一次夏季干旱(2007年5月至7月)，与2003年中欧炎热干燥的年份相似，年降雨量减少了约30%。我们添加了C-13耗竭的以及未标记的草/三叶草凋落物来量化凋落物产生的二氧化碳外流(F-凋落物)。在2007年生长季测定了土壤CO2流出量和添加凋落物后呼吸的CO2的C-13/C-12同位素比值(C-13)。在枯落物添加试验中，干旱显著降低了枯枝落叶59%的F-土壤和81%的F-凋落物，表明干旱对凋落物CO2释放的影响大于对地下CO2排放(F-BG，即土壤有机质和根系呼吸)的影响。在整个C-13测量期间(4月至10月)，尽管长期干旱后的复湿导致呼吸二氧化碳的大量爆发，但干旱也使F-土壤和F-凋落物分别减少了26%和37%。总体而言，我们的研究结果表明，干旱减少了F-土壤，改变了其季节性和来源。因此，温带草原土壤的碳平衡对降水的变化非常敏感，这是预测气候变化对生态系统碳平衡影响的区域模型中需要考虑的一个因素。
Current climate change models predict significant changes in rainfall patterns across Europe. To explore the effect of drought on soil CO2 efflux (F-Soil) and on the contribution of litter to F-Soil we used rain shelters to simulate a summer drought (May to July 2007) in an intensively managed grassland in Switzerland by reducing annual precipitation by around 30% similar to the hot and dry year 2003 in Central Europe. We added C-13-depleted as well as unlabelled grass/clover litter to quantify the litter-derived CO2 efflux (F-Litter). Soil CO2 efflux and the C-13/C-12 isotope ratio (delta C-13) of the respired CO2 after litter addition were measured during the growing season 2007. Drought significantly decreased F-Soil in our litter addition experiment by 59% and F-Litter by 81% during the drought period itself (May to July), indicating that drought had a stronger effect on the CO2 release from litter than on the belowground-derived CO2 efflux (F-BG, i.e. soil organic matter (SOM) and root respiration). Despite large bursts in respired CO2 induced by the rewetting after prolonged drought, drought also reduced F-Soil and F-Litter during the entire C-13 measurement period (April to October) by 26% and 37%, respectively. Overall, our findings show that drought decreased F-Soil and altered its seasonality and its sources. Thus, the C balance of temperate grassland soils respond sensitively to changes in precipitation, a factor that needs to be considered in regional models predicting the impact of climate change on ecosystems C balance.