Effects of soil moisture on soil respiration in Populus tremula plantations in Southeast Shandong

【Objective】 The objective was to clarify the effects of soil moisture on soil respiration in Populus tremula plantations in Southeast Shandong.【Method】 Soil respiration,heterotrophic respiration and autotrophic respiration had been measured with portable infrared CO2 gas analyzer(GXH-3051) combined with homemade closed chamber in middle-aged Populus tremuloides plantation and mature Populus tremuloides plantation in Benghe Forest Farm for two years(2010-2011).Soil temperature and soil moisture were also measured simultaneously.【Result】 The soil respiration in middle-aged Populus tremuloides plantation and mature Populus tremuloides plantation showed distinct seasonal dynamics with unimodal curve.Soil respiration was highest in July and lowest in January.The maximum rates of soil respiration in middle-aged Populus tremuloides plantation and mature Populus tremuloides plantation were 4.43 and 3.55 μmol/(m2·s),respectively while the minimum rates were 0.72 and 0.54 μmol/(m2·s),respectively.Similar to soil respiration dynamics,autotrophic respiration showed remarkable fluctuation.In contrast with soil respiration,soil heterotrophic respiration and soil moisture showed more complex variation.Correlations between soil respiration,autotrophic respiration,soil heterotrophic respiration and soil moisture were all linear.The correlation between soil respiration and soil moisture was highest for the middle-aged Populus tremuloides plantation(r2=0.750 3).【Conclusion】 Correlations between soil respiration,heterotrophic respiration,autotrophic respiration and soil moisture were linear.However,the influencing mechanism was complex.