| Soil respiration,the second largest site of carbon flow in the forest ecosystem carbon budget,plays an important role in the global carbon(C)cycle and climate change.A thinning manipulation experiment was conducted in a Larix.principis-rupprechtii plantations in Shanxi province,China,with the following treatments:heavy thinning,moderate thinning,low thinning and no thinning.In addition,three treatments—litterfall and root removal,litterfall removal and control—were analyze the relationship between differences in litter output and soil respiration.Rates of soil respiration were measured twice a month using the LI-8100 Automated Soil CO2 Flux System during the growing season(May-October)of 2015-2017.To evaluated the impact of the change litter input and throughfall reduction on soil respiration under the Larix.principis-rupprechtii plantations.Three treatments—litter addition,30%throughfall reduction,60%throughfall reduction—were applied to determine the contribution of litter and throughfall to soil respiration.The rates of soil respiration were measured twice a month from May to October 2016-2017 by using the LI-8100,while soil temperature and moisture at a depth of 5 cm were measured using temperature and moisture probes and data loggers.The main results showed:(1)During the observation period,the soil respiration had significant seasonal variation in the growing season.The maximum value of soil respiration appeared in July or August,which not changed by thinning,litterfall change and throughfall reduction.Under thinning conditions,the soil respiration was significantly enhanced by moderate thinning(P<0.05);Low thinning had no significantly influence on soil respiration(P>0.05).Under litterfall change conditions,the soil respiration rate was lower by 37.88%with litterfall removal than that of the control(P<0.05);however,Soil respiration rate was higher by 12.19%with litter addition than that of the control(P<0.05).Under throughfall reduction conditions,the treatment of 60%throughfall reduction increased soil respiration rate during the growing season by 15.79%from that of the control;whereas,the treatment of 30%throughfall reduction had no significant effect on soil respiration(P>0.05).(2)The results indicated that the interaction between thinning treatments and litter changes has a significant effect on the soil respiration in Larix.principis-rupprechtii plantations.The interaction between low thinning,heavy thinning and litterfall removal alleviated soil respiration.Low thinning,heavy thinning and litterfall removal had synergistic effect,while low thinning,heavy thinning and litter addition had antagonism.The interaction between moderate thinning and litter addition promoted soil respiration.Moderate thinning and litterfall removal had antagonistic effect,while moderate thinning and litter addition had synergy.The throughfall reduction had a certain antagonistic effect on soil respiration.Meanwhile the degree of antagonism increases with the time and the level of throughfall reduction.(3)During the growing season,Soil temperature had a significant effect on soil respiration in Larix.principis-rupprechtii plantations.The relationships between soil respiration and soil temperature at 5 cm depth could be described by an exponential equation(P<0.05),while there were no significant differences in soil moisture among the various treatments.The best fitting model with temperature explained 59.1%?82.8%of the variation in soil respiration in the growing season.Temperature sensitivity(Qio)values of soil respiration ranged from 2.03 to 3.16 in the various treatments.The minimum value of Q10 was 2.03 in the litter addition and heavy thinning stand,with the highest Qio value in the 60%throughfall reduction.The Q10 values were decreased in the treatments of thinning and litterfall changes relative to the control,and that with throughfall reductions were higher than the control. |
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