Response Of Soil Organic Carbon Character And Correlative Factor To Kinds Of Vegetations Changing From Farmlands

As the main components of terrestrial ecosystem carbon stock, soil organiccarbon (SOC) play an important rule in the global carbon cycle. Under thebackground of global atmosphere warm, how to management terrestrialecosystems so as to keeps the carbon pool stabilization and sequestrated moreatmosphere carbon are the new challenge we have to face today. Presently,researches about mechanism of soil organic carbon sequestrating have beenpaying more sight on.Sequestrating and turnover dynamics of SOC have impact relationship withland use change and managements, generally, afforest is thought to be a progressof carbon sequestrates, the reverse progress cause carbon loss. Actually, duringthe progress of vegetation changing, SOC pool sequestrate or loss carbon and howmuch there are depended not only on the vegetation types before or after thevegetation change, but also depended on the history or status in quo of land useand management intensity.In southwest of China, there is the secondary big Areas of forest of the country.Like northeast China, in this region, soil organic matter decomposing at a very lowrate, so is favor for atmosphere carbon stock. In Recent years, there was largeareas of forest has been planting, but most of this forest types has caused soilnutrition loss. So these types of forest lack the potential of growth and renew andare bad at atmosphere carbon sequestrated. Otherwise, there is mass ofpopulation and with low economy level in this region, reduce of agriculture landsarea destine to cause stress to inhabitant living. So, farmland as the contrast, 1)thisresearch study soil carbon pool characters, soil layer distribution and seasonaldynamics of SOC of kinds of woods pattern established from the farmlands. 5 year ago. 2) Beside this, elated factor was studied the layer distribution and seasonaldynamics too. Result indicated:1. the farmland has the highest carbon density value of 7.2kg/m², compared toBetula luminifera 6.7kg/m², Pleioblastus amarus 5.2kg/m², Pleioblastus amarus mixwith Betula luminifera 4.9 kg/m², and Hemarthria compressa grassland 4.2 kg/m²was the lowest at the 0～40cm layer. This result contravention with the normallyknowledge that farmland usually has lower soil organic carbon stack. At the0～20cm depth, Betula luminifera forest has highest carbon density of 3.8 kg/m².Which suggest that investigate depth has a significant influence on estimation ofsoil carbon storage. In all vegetation types investigated this study, carbon densitydecrease in the deeper soil layer, which agree with most of study.2. Afforest reduced content of ROC (readily oxidation carbon), Increased soildepth reduce ROC content too. There are positive relationship between theContent of ROC and SOC, maybe reduce of SOC content caused ROC loss. FromMarch to September, the seasonal dynamic of ROC content is synchronization withatmosphere temperature increase, so atmosphere temperature maybe the mainfactor that effect dynamic of ROC contents. At each soil profile layer, contents ofROC has three peak values, it would be cause by change of precipitation.3. Afforest reduced content of POCp (particle soil organic carbon per particlesoil fraction), Increased soil depth reduce ROC content too. At each soil profilelayer POCs (particle organic carbon per soil) have two peak values (one is higherthan the other) during investigate period. The seasonal dynamic of POCs maybeimpact by dynamic of PSR (particle soil rate)4. Afforest reduced content of N. Hemarthria compressa grassland has thelowest N content among several vegetation types. Seasonal dynamic of N at thetop 0-20cm surface layer of soil fluctuation during the period of form March toNovember. From March to July, soil N reduce, while at the period of July toSeptember, content of soil N has a distinctively increase.5. Afforest reduced content of PNp (particle soil N per particle soil). At all thestudied vegetation types, content of PNp and PNs decrease with soil depth. At the direct of soil profile, the decrease of PNs (particle soil N per soil) mainly caused byPNp decrease.6. After afforest from the farmland, soilδ¹³C increase or decrease dependedon vegetation types new cultivated. Butδ¹³C increase with soil depth, agree withmost of the relative study. At all vegetation types,δ¹³C of particle soil fraction isless than whole soil, suggest that particle soil sequestrate more newly formedcarbon.7. The Urease Activity of farmland is higher than other vegetation types, andurease activity of all kinds of vegetation types we studied decrease with soildepth increase, but increase from March to November.8. The value of pH increase with soil depth at all the studied vegetation types,but vegetation types have significant impact to the pH values of each layer. Thedynamic of pH values is divided to three period, (1) increase period, mainly atspring. The value of pH increase with atmosphere and precipitation increase, (2)rapidly decrease period. Mainly summer, period with heavy precipitation whichcause salt ion be eluviated, (3) stabilization period. Period belong autumn andwinter, at which with low precipitation and biological activity.