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."

本研究针对模拟飓风试验中土壤与大气间的温室气体通量展开了考察。下文转载了已发表论文的摘要（详见方法部分）："本研究在一片林龄77年的温带硬木林中开展，在该林实施模拟飓风风倒处理后，持续1年按月测定了土壤与大气间的一氧化二氮（N₂O）、二氧化碳（CO₂）与甲烷（CH₄）通量。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，且与风倒处理样地无显著差异。对照样地的年一氧化二氮排放量较低（0.23千克氮·公顷⁻¹·年⁻¹），经风倒处理后其排放量下降了78%。净氮矿化作用未受风倒处理的影响。风倒处理样地的净硝化作用强于对照样地，但净硝化的绝对速率以及矿化氮中被硝化的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吸收量与土壤含水率呈负相关。风倒事件后，倒伏或受损的林木大量萌蘖展叶，且林下植被生长加快。这或许是对照样地与风倒处理样地在土壤温度、含水率、氮有效性、净氮矿化与净硝化作用间仅存在较小差异的原因，进而使得CO₂与CH₄通量未发生变化，一氧化二氮排放量也未出现增加。"