DOC And DOC Adsorption In Soil By Litter Decomposition During Forest Succession In Great Khingan Mountains

Dissolved organic carbon(DOC)is the most active and moving part of soil organic carbon.The restoration and succession of forest vegetation is a natural process.Studying the dynamic process of DOC release from litter layer under different forest successions and the adsorption of DOC in soil and its influencing factors will help to clarify the cycle and transformation of DOC in forest soil and provide effective data for accurate evaluation of forest material cycle.The litter in L,F and H layers of herbaceous,shrub,birch,Larch and birch forests and soil mineral layers of 0?10cm,10?20cm and 20?30cm were obtained by "space instead of time" method under the succession of forest in Great Khingan Mountains.Three layered litters of herbaceous,shrub,birch,Larch and Larch Forests in five stages of forest succession were cultured at 36?,24? and 12? degrees respectively.The experiment lasted for 195 days.During the experiment,the concentration of DOC precipitated from litter was measured every 15 days,and the residual litter was measured at the end of the experiment.The adsorption equilibrium method was used to compare the changes of soil adsorption intensity with forest succession,and the dynamics of soil adsorption of DOC and the effects of acidity and soil elements on DOC adsorption were analyzed.The main conclusions are as follows:(1)With forest succession,litter decomposition rate and DOC release increased first and then decreased,but with the difference of temperature and litter,the maximum appeared in different succession stages.(2)In addition to SHR stage,litter decomposition rate and DOC release increased with the increase of temperature.The results showed that litter decomposition rate and DOC release rate increased when the litter decomposition rate and DOC release rate were higher than 24? and DOC release rate was higher than 12? at 36?.Under different litter layers,the decomposition rate and DOC release of litter were L>F and H layers.During the whole cultivation process,the concentration of DOC released by litter increased at first,then decreased,and then decreased steadily.(3)The decomposition rate of litter was positively correlated with the amount of DOC released during decomposition.(4)The IM isotherm equation is the best fit for the adsorption of DOC by soil.With the development of forest succession,the amount of DOC adsorbed by soil decreases first,then increases and finally decreases.Exchangeable potassium,calcium,magnesium,total nitrogen and organic matter in soil were positively correlated with DOC adsorption.(5)The first-order kinetic equation is used to describe the best dynamic adsorption of DOC by soil.Soil adsorption of DOC,in the early stage of adsorption,the adsorption rate is faster,with the increase of time,the adsorption rate gradually slows down,to 24 hours,the adsorption state tends to balance.(6)In DOC solution with different acidity,the specific change of soil adsorption strength for DOC is:pH equal to 5.0>pH greater than 3.0>pH equal to 7.0.