Response Of Soil Respiration In Larch Plantations In North China To Thinning Intensity

This article takes north China larch density control sample as investigation object,in May 2015-the beginning and the end of October,the LI-8100 soil carbon flux measurement system of 12 samples to "the same breath,removal of litter respiration,removal of litter to cut off the root" and 5 cm below the soil temperature and humidity measurement,2018 on the basis of the original measure adding"double litter breathing" measurement.The purpose of this study is to study the changing rules of soil respiration and its components and the influencing mechanism of environmental factors in the growing season under different thinning intensities,which is of great significance for rational and effective forest management in the future,and to provide scientific basis for further discussion on forest carbon cycle and global climate change.The main experimental results are as follows:(1)in the growing season of 2018,the total soil respiration rate(Rs)of larch plantations in north China was the highest in July and August,and the lowest in October.The seasonal variation trend of total soil respiration rate was the same under different thinning intensities,and both showed a trend of gradual increase and then decrease.The total respiration rate of medium and moderate thinning was higher than that of control,light thinning and heavy thinning.There was a significant correlation between temperature and soil total respiration rate of stands after thinning,and it had a direct effect on soil total respiration rate.There was a significant correlation between temperature and total soil respiration rate of uncut stands,and temperature and humidity had direct and indirect negative effects on total soil respiration rate.(2)in the growth season of 2018,the soil autotrophic respiration rate(Ra)was the highest in July and the lowest in May under the stand without thinning of larch plantations in north China.Under the stand after thinning,the soil autotrophic respiration rate was the highest in July and August,and the lowest in September and October.In July and August,the rate of soil autotrophic respiration under mild thinning was significantly higher than that under severe thinning(P<0.05),and in October,the rate of soil autotrophic respiration under moderate thinning was significantly higher than that under severe thinning(P<0.05).There was a significant correlation between soil temperature and autotrophic respiration rate in the control and mild treatments.(3)in the growing season of 2018,the seasonal dynamic law of soil heterotrophic respiration rate(Rh)of larch plantations in north China is the same as the total soil respiration rate.In may,the rate of soil heterotrophic respiration under mild thinning was significantly higher than that under moderate thinning(P<0.05).In June and August,the rate of soil heterotrophic respiration under mild thinning was significantly lower than that under moderate thinning(P<0.05).There was a significant correlation between soil temperature and heterotrophic respiration rate under different thinning conditions.(4)in the growing season of 2018,the rate and carbon flux of litter-removal respiration and litter-doubling respiration in larch plantations in north China were the highest in July and August.In July and August,soil respiration rate of double litters under interthinning treatment was significantly higher than that of the control group(P<0.05).(5)of north China larch plantation under different thinning intensity of soil respiration rate in 2018,carbon,temperature and humidity are higher than in 2015,the highest percentage of the contribution of heterotrophic respiration rate,the thinning of the forest soil respiration of 4 a total rate between different thinning intensity still exist significant difference(P<0.05),but not a 7 after thinning.