Research On The Characteristics Of Soil Respiration Of Growing Period In Different Age Populus Tomentosa Plantation From Farmland

In order to research the diurnal,monthly dynamics of soil respiration rate,the effects of temperature-humidity of soil on soil respiration,the proportion of each component of soil respiration and the influences of returning farmland to forest of soil respiration. Soil respiration rates in growing period in 40-year-old Populus tomentosa plantation(sample plotⅠ)and 5-year-old P. tomentosa+84K plantation(sample plotⅡ)after returning farmland to forest were measured by Li-6400 system from May to October in 2014. The results are as follows:(1)The soil respiration rates had a significant monthly dynamic with unimodal curve in sample plot Ⅰand Ⅱ. The average monthly maximum were 5.24μmol/(m2·s)and 4.28μmol/(m2·s),respectively,appearing in July,the average monthly minimum were 1.88μmol/(m2·s)and 1.48μmol/(m2·s),respectively,appearing in October,and the average rate of soil respiration in growing period were 3.34μmol/(m2·s)and 3.08μmol/(m2·s),respectively,soil respiration rate of sample plot Ⅰwas higher than that of sample plot Ⅱ.(2)The relationships between soil respiration and soil temperature could be described by exponential equations in the sample plot Ⅰand Ⅱ,Q10 value was 3.78 at 10 cm soil depth in the sample plotⅠ,and in the sample plotⅡ,it was 3.60. There was no significant correlation between soil respiration and soil moisture in the sample plotⅠ,but in the sample plotⅡ,there was significant negative correlation among them.(3)In the three components of soil respiration of growing period,the average rate of root respiration were 0.85μmol/(m2·s)and 0.76μmol/(m2·s),respectively,in the sample plot Ⅰand Ⅱ,the average rate of microbial respiration were 2.22μmol/(m2·s)and 2.01μmol/(m2·s),respectively,and the average rate of litter respiration were 0.27μmol/(m2·s)and 0.31μmol/(m2·s),respectively. Microbial respiration accounted for more than 60%,root respiration accounted for 20%~30%,and litter respiration accounted for about 10%.(4)Soil respiration rate of 40-year-old plantation was higher than that of 5-year-old plantation,the main impact factor was soil temperature,and 40-year-old plantation was more sensitive to soil temperature than 5-year-old plantation.(5)Root respiration and microbial respiration increased to the highest in summer(in August),the proportion of them were 28.56%、27.38% and 71.03%、72.34%,respectively,in the sample plot Ⅰand Ⅱ. The impact on microbial and root respiration was more than litter respiration after returning farmland to forest,and the impact from 40-year-old plantation was greater than that from 5-year-old plantation.