冻融对内蒙古温带贝加尔针茅草甸草原N2O通量的影响

Effect of freezing-thawing cycles on N_2O fluxes from temperate Stipa baicalensis meadow grassland soils in Inner Mongolia

本研究以内蒙古呼伦贝尔草甸草原为研究对象,通过室内模拟实验与野外观测实验相结合,分析不同土层、放牧与封育、长期与短期冻融、不同冻融频率与冻融温差强度对草地土壤N2O产生与排放的影响.结果表明：冻融期间,从地表到下层15cm土壤N2O的产生速率随深度的增加而逐渐减少,N2O的产生主要来源于0～9cm的表层土壤；冻融期间温差相同的情况下,冻融次数越多,N2O的产生速率越小；N2O的产生速率随着温差的变小而减少；冻融期间封育样地的N2O排放量大于放牧样地,且封育样地的N2O排放量占全年排放总量的25.09%,大于放牧样地（12.38%）,但从观测年排放总量看,放牧却促进了草地N2O源的功能；草地春融期间的N2O排放量是整个冻融期N2O排放量的最大贡献者.

In this paper we combined the laboratory simulation tests with field experiments of greenhouse gas fluxes, and analyzed the effects of different soil layers, grazing and fencing, long-term and short-term freezing-thawing, different frequency and intensity of freezing-thawing on soil N2O production rate and emission flux in Hulunbuir meadow grassland in Inner Mongolia. During freezing and thawing, the N2O productions mainly came from topsoil of 0to 9cm depth, and gradually reduced from the surface down to depth of 15cm soil. The N2O emissions decreased with lowing temperature differences. Under the situation of the same temperature differences, the N2O emissions decreased with increasing freezing-thawing frequencies. During the freezing-thawing cycle, N2O fluxes of fenced plot were greater than that of grazing plot, contributing to 25.09%of annual N2O emissions, while the contribution is about 12.38%for grazing plot. However from the annual time scale, the grazing increased the annual total N2O emissions. Early spring thawing was the largest contributors to the N2O emission during the whole period of freezing-thawing cycles.