Trace Gas Fluxes and Soil N Dynamics in Simulated Hurricane Experiment at Harvard Forest 1989-1991

This study examined the fluxes of greenhouse gases between soils and the atmosphere in the Simulated Hurricane Experiment. The abstract from the published paper (see Methods) is reproduced below. "Fluxes of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) between soils and the atmosphere were measured monthly for one year in a 77-year-old temperate hardwood forest following a simulated hurricane blowdown. Emissions of CO2 and uptake of CH4 for the control plot were 4.92 MT C ha-1 y-1 and 3.87 kg C ha-1 y-1, respectively, and were not significantly different from the blowdown plot. Annual N2O emissions in the control plot (0.23 kg N ha-1 y-1) were low and were reduced 78% by the blowdown. Net N mineralization was not affected by the blowdown. Net nitrification was greater in the blowdown than in the control, however, the absolute rate of net nitrification, as well as the proportion of mineralized N that was nitrified, remained low. Fluxes of CO2 and CH4 were correlated positively to soil temperature, and CH4 uptake showed a negative relationship to soil moisture. Substantial resprouting and leafing out of downed or damaged trees, and increased growth of understory vegetation following the blowdown, were probably responsible for the relatively small differences in soil temperature, moisture, N availability, and net N mineralization and net nitrification between the control and blowdown plots, thus resulting in no change in CO2 or CH4 fluxes, and no increase in N2O emission."

本研究围绕模拟飓风试验中的土壤-大气温室气体通量展开了调研。以下复刻自已发表论文的摘要（详见方法部分）：“本研究于一处林龄77年的温带硬木林中，针对模拟飓风倒伏事件后的土壤与大气间一氧化二氮（nitrous oxide, N₂O）、二氧化碳（carbon dioxide, CO₂）及甲烷（methane, CH₄）通量开展了为期一年的月度监测。对照样地的CO₂排放量与CH₄吸收量分别为4.92吨碳·公顷⁻¹·年⁻¹与3.87千克碳·公顷⁻¹·年⁻¹，二者与倒伏样地的对应数值均无显著差异。对照样地的年一氧化二氮排放量为0.23千克氮·公顷⁻¹·年⁻¹，处于较低水平，而飓风倒伏事件使其排放量降低了78%。净氮矿化速率未受飓风倒伏事件的显著影响。倒伏样地的净硝化速率高于对照样地，但净硝化的绝对速率以及矿化氮的硝化占比仍处于较低水平。CO₂与CH₄的通量与土壤温度呈正相关，而CH₄吸收量与土壤含水量呈负相关。倒伏事件后，倒伏或受损林木出现了大量萌蘖与展叶，同时林下植被生长量有所提升，这大概率是导致对照样地与倒伏样地间土壤温度、含水量、氮有效性、净氮矿化速率及净硝化速率仅存在小幅差异的原因，最终使得CO₂与CH₄通量未发生变化，一氧化二氮排放量也未出现上升。”