Seasonal Dynamic Changes Of Soil DOM In Minnan-Chinese Fir Mixed Forest

The contents of SOC,TN,TP,DOC,DON and DOP in soil,seasonal dynamics and eco-stoichiometric characteristics of Minnan-Cunninghamia lanceolata plantation,Chinese fir plantation and Minnan plantation were studied.The eco-stoichiometric characteristics of soil DOM and soil C,N and P and their correlation were analyzed.The seasonal dynamics of soil DOM in different forest types were studied.The results are of practical significance to the allocation of plantation species and the selection of management measures in southern China.The main conclusions of this paper are as follows:(1)The contents of SOC,TN and TP in 0-30 cm soil of three forest types decreased with the increase of soil depth.The average contents of SOC,TN and TP in 0-30 cm plantation soil of Minnan were the highest,17.24 g�kg-1,1.56 g�kg-1,0.46 g�kg-1,respectively.The average contents of SOC,TN and TP in Chinese fir plantation soil were the lowest,12.82 g�kg-1,1.06 g�kg-1 and 0.24 g�kg-1,respectively.There were no similar seasonal dynamics of SOC,TN and TP in 0-30 cm soil of three forest types.The SOC content of Minnan-Cunninghamia lanceolata mixed forests changed roughly as follows:spring>autumn>winter>summer,Chinese fir plantations showed autumn>summer>spring>winter,Minnan plantations showed winter>summer>autumn>spring;Minnan-Cunninghamia lanceolata Mixed Forests Soil TN content changed roughly as follows:autumn>spring>winter,Chinese fir plantations.The results showed that:Summer>Autumn>Spring>Winter,Minnan plantation showed as follows:Summer>Spring>Autumn>Winter;The roughly changing law of TP content in Minnan-Chinese fir mixed forest showed as follows:Autumn>Winter>Summer>Spring,Chinese fir plantation showed as follows:Spring>Autumn>Summer>Winter,Minnan plantation showed as follows:Winter>Summer>Spring>Autumn.Soil SOC has a significant negative correlation with water content in Chinese fir plantation and a significant positive correlation with pH in Minnan plantation.(2)The soil DOC and DOP of 0-30 cm plantation of Minnan were the highest,226.44 mg�kg-1 and 1.28 mg�kg-1,respectively.The average value of Chinese fir plantation was the lowest,203.39 mg�kg-1 and 1.22 mg�kg-1,respectively.The soil DON of 0-30cm Minnan-Cunninghamia lanceolata plantation was the highest,59.08 mg�kg-1,and that of Minnan plantation was the lowest,40.50 mg�kg-1.The soil DOC,DON and DOP of three forest types had similar dynamic changes.The soil DOC in 0-30 cm layer showed autumn>winter>summer>spring;the soil DON in 0-10 cm layer showed autumn>winter>summer>spring,and in 10-30 cm layer showed autumn>winter>spring>summer;the soil DOP in 0-30 cm layer showed winter>autumn>spring>summer.Soil DOC has a significant positive correlation with water content in Minnan-Cunninghamia lanceolata plantation and soil SOC in Minnan-Cunninghamia lanceolata plantation.Soil DON has a significant positive correlation with soil SOC in Minnan-Cunninghamia lanceolata plantation,a significant positive correlation with TN,and a significant negative correlation with soil bulk density;Soil DOP has a significant negative correlation with soil SOC in Minnan-Cunninghamia lanceolata plantation.There are significant positive correlations between SOC and TN,soil water content,soil bulk density,soil SOC in Chinese fir plantation,soil SOC in Minnan plantation and soil TN.Principal component analysis showed that the mixed forest of Phoebe fujianensis and Cunninghamia lanceolata had the greatest impact on soil DOC content,the most soil DON content of Chinese fir plantation had the greatest impact,and the most soil DOP content of Phoebe fujianensis plantation had the greatest impact.(3)Soil C/N,CUP and NIP of 0-30 cm of three forest types decreased with the increase of soil depth.The average soil C/N of 0-30 cm Chinese fir plantation was the largest,11.35,Minnan plantation was the smallest,10.17;the average soil C/P and N/P of 0-30 cm Minnan-Chinese fir plantation were the largest,56.77 and 4.95,respectively,and Minnan plantation was the smallest,34.65 and 3.35,respectively.?The average DOC/DON of soil in 30 cm Minnan plantation was the highest,4.88,Minnan-Cunninghamia lanceolata plantation was the lowest,3.79;the average DOC/DOP and DON/DOP of soil in 0-30 cm Minnan-Cunninghamia lanceolata plantation were the highest,198.28 and 52.50,respectively,and that of Chinese fir plantation was the lowest,182.13 and 39.06,respectively.Soil C/N in Minnan-Cunninghamia lanceolata plantation has a significant negative correlation with soil DOC/DOP,and has a significant negative correlation with soil DON/DOP.In Minnan plantation,soil DOC/DOP has a significant negative correlation;soil N/P in Minnan plantation has a significant negative correlation with soil DOC/DON.In a word,Minnan-Cunninghamia lanceolata plantation and Minnan plantation are superior to Chinese fir plantation in maintaining soil nutrients and increasing soil fertility,and Minnan-Cunninghamia lanceolata plantation is superior to Chinese fir plantation and Minnan plantation in retaining soil soluble nutrients.