The Dynamics And Affecting Factors Of Total Organic Carbon Pool Of Robinia Pseudoacacia Plantation In Loess Gully Region

This study took Robinia pseudoacacia plantation, a typical artificial tree standin loess Gully region as object, discussed vegetation and soil organic carbon storageof it and its influencing factors, investigated whether the artificial afforestation hadthe effect of carbon sink or not in loess Gully region. The growth years of theplantation were9a,17a and30a,the main research items were communitycharacteristics, soil and plant organic carbon content, the main nutrient content, soiland plant organic carbon storage and the effect of soil organic carbon storage. Themain conclusions showed as follows:(1) Locust plantation trees The breast-height diameter, tree height and crowndensity of the communities increased with the increase of locust growth years. Instage of9a to17a,the growth rate of the breast-height diameter, tree height andcrown density was greater the it in the stage of17a to30a. The result showed that thestage of fast growing was in9a-17a.The distribution of breast-height diameter of9a-17a Locust plantation was in4cm-6cm,it of30a Locust plantation was in6-8cm.With the Locust plantation grew, the distribution of breast-height diameterbecame wider. The largest breast-height diameter of9a and17a Locust plantationwas12cm-14cm,this of30a Locust plantation was18cm-20cm. The distribution ofheight of9a,17a and30a was4m-6m,8m-10m and10m-12m respectively.(2)The difference of organic carbon content in every parts of locust plantationwere not obvious. The scope of soil organic carbon content in the litter was402.68g·kg^-1-458.32g·kg^-1, The scope of soil organic carbon content in grass was407.17g·kg^-1-454.50g·kg^-1, The scope of soil organic carbon content in every parts ofLocust was453.28g·kg^-1-483.62g·kg^-1.In the earlier stage of Locust plantation, thesoil organic carbon content in every soil layer of0-100cm were smaller than CK.With the growth of the tree, in the stage of17a and30a, the soil organic carboncontent in every soil layer of0-100cm were larger than CK.(3)Plant organic carbon storage depended mainly on the amount of every parts of the biomass as plant organic carbon content were similar, so the total organiccarbon storage of vegetation was successively30a>17a>9a>CK; the carbon storageof tree root, trunk and branch had a relatively large contribution to the total carbonstorage of vegetation, the sum of three parts accounted for87.73%,85.50%,92.63%in9,17a and30a growth years respectively. So the organic carbon storage ofvegetation concentrated in the part of tree.The soil organic carbon storage concentrated in soil layer0-60cm whichreserved in a larger proportion in the soil organic carbon pool. In the earlier stage ofLocust plantation, the total soil organic carbon storage of0-100cm soil layer wassmaller than CK. With the growth of the community, in the stage of17a and30a, thetotal soil organic carbon storage of soil layer0-100cm was greater than CK.The total organic carbon storage of the ecosystem was increased with thegrowth years. so the total organic carbon storage of ecosystem was successively30a>17a>9a,the result showed that afforestation could effectively increase the totalorganic carbon storage of the ecosystem. Soil organic carbon pool was the majorcomponent of the total organic carbon of the ecosystem.(4)The relationship of total nitrogen and soil organic carbon storage was asignificant positive correlation as the total phosphorus content of soil, The resultshowed that the total nitrogen and total phosphorus of soil had a direct impact on soilorganic carbon, and the increase of their content contributed to the increase of soilcarbon stoCKs. The relationship between the biomass of grass root and soil organiccarbon storage was a significant positive correlation as the biomass of litter, theresult showed that decomposition of the grass and litter made the soil organic carbonstorage of surface layer increased significantly which reserved in a larger proportionin the total soil organic carbon storage. In the stage of17a and30a, Therelationship between the biomass of tree root and soil organic carbon storage was asignificant positive correlation. With the development of community, decompositionof the tree root made the soil organic carbon storage increased significantly.