Effects Of Litter Decomposition Of Pinus Sylvestris Var. Mongolica Mature Forest On Soil Organic Carbon,Nitrogen And Phosphorus

In this study,the response of soil organic carbon,alkaline nitrogen,total nitrogen,fast-acting phosphorus and total phosphorus to stand density,stand age and root growth in each layer of soil in the vertical profile under the conditions of decomposition of apoplastic matter was analysed by means of sample plot survey,apoplastic matter collection and determination of soil carbon,nitrogen and phosphorus content,based on computer statistical analysis of the amount of variation.The main findings of the study are as follows.(1)The vertical pattern of soil organic carbon showed that the content and variation of soil organic carbon decreased with the increase of soil depth.The variation of soil organic carbon in the upper 0～20 cm was positively correlated with stand density;soil organic carbon was positively correlated with stand age,but the variation was not significant;the variation of soil organic carbon caused by root growth was significantly different in each soil layer and different growth time periods,and the variation of soil organic carbon in the 10～20 cm soil layer and T2 decomposition time was the most significant,which was highly consistent with the vertical distribution and growth period of Sphagnum pine hairy root density.The most significant variation in soil organic carbon was found in the 10～20 cm soil layer and at T2 decomposition time,which coincided highly with the vertical distribution of sphagnum root density and the growing period.(2)Soil alkaline nitrogen content and variation also had a general trend of decreasing with increasing soil depth;the variation of soil alkaline nitrogen and stand density were highly significantly correlated at T1 and T2 during the pre-decomposition period in the 0～20cm soil layer,and the significance and correlation of the variation of soil alkaline nitrogen in each layer decreased with the depth of soil layer and decomposition time.The variation in soil alkaline nitrogen in the deepest 40～60 cm soil layer was not significantly different from the stand density,and the correlation between the two was not significant;soil alkaline nitrogen content and variation were positively correlated with stand age,but the variation in soil alkaline nitrogen between stand ages was not significant;the variation in soil alkaline nitrogen was significantly different in each soil layer and at different growth times,and the variation in soil organic carbon was greatest in the 10～20 cm soil layer and during T2 decomposition.(3)There is a general trend that the content and variation of soil fast-acting phosphorus decreases with increasing soil depth.0-20 cm soil fast-acting phosphorus variation is positively correlated with stand density from T1 to T2,while 20-60 cm soil fast-acting phosphorus variation has a complex and non-significant relationship with stand density;the response of soil fast-acting phosphorus variation to stand age is not significant in all layers,and there is no significant correlation between soil fast-acting phosphorus and stand age The variation of soil fast-acting phosphorus due to root growth was significantly different among soil layers and different growth periods,with the highest variation in soil fast-acting phosphorus in the 10-20 cm soil layer and during the T2 decomposition period in the growing season.(4)Soil total nitrogen and phosphorus content and the amount of variation varied slightly throughout the experimental cycle of one year(T1～T4),and the variability and correlation with stand age and stand density were poor.The thesis has 25 figures,10 tables and 74 references.