Effect Of Acidic And Alkaline Substances Addition On Decomposition Of Different Types Of Litters In Pinus Tabulaeformis In Taiyue Mountain

Over the past four decades,forest ecosystems in the Northern Hemisphere have been subjected to severe atmospheric deposition of acidic compounds due to human activities.Decades of increasing input and leaching of SO₄^-2 and NO₃ have result in the loss of exchangeable base cation in soil and retention of S and N,which slows the recovery rate of forest ecosystem.Lime is often used to alleviate soil acidification.In this study,ammonium nitrate and alkali lime were added to the soil in Taiyue Mountain to change the soil environment.The effects of acidic and alkaline substances addition on decomposition rate,nutrient change and enzyme activity of litters were investigated,for purpose to provide basic data for the effect of acidic and alkaline substances addition on litter decomposition in boreal forest of China.Acid and alkaline substances had been added to the soil once a year since 2015.We set 4 levels of acidic and alkaline substances addition respectively.And there were 4 repetitions for CK and each treatment.Litter bags are arranged in the plot and samples are collected every 3 months.Dry matter mass,nutrient concentration of litters,and activity of related enzymes were measured.The results are as follows:?1?Types and initial mass of litters are the main factors affecting the decomposition rate of litters.The decomposition rate order of the three litter types was:Quercus wutaishansea>Mix>Pinus tabulaeformis.The addition of acidic substances inhibited the decomposition of litters,and the inhibition depended on the type of litters and the concentration of nitrogen addition.The effect of alkaline substance addition on litter decomposition varies with different litter types.?2?The migration mode of organic carbon was direct release.Types and season of litters could affect the release rate of organic carbon.In sites with alkaline substances addition,the release rate of organic carbon was higher than that with acidic substances addition.The migration mode of total nitrogen was leaching-enrichment-release,litter type affects the total nitrogen release,and nitrogen addition might promote nitrogen fixation.Therefore,the release of total nitrogen in sites with acidic substances addition is lower than that with alkaline treatments.The migration mode of total phosphorus was affected by litter type and initial phosphorus content of litters.At the initial stage of decomposition,the total phosphorus content of Quercus wutaishansea leaves Mix added with acid was about 2.5 times of the initial value.The addition of alkaline substances affected the release of total phosphorus from litters.?3?At the later stage of decomposition,litters types significantly affected the activity of enzymes related to the C,N and P cycles.The types of litters that were decomposed quickly had higher enzyme activity,the activities of?-1,4-glucosidase,?-1,4-glucosidase,cellobiohydrolase and acid phosphatase in Quercus wutaishansea leaves were 1.21 times higher than those in Mix.The activity of?-1,4-glucosidase and cellobiohydrolase in the litters of Quercus wutaishansea was 2.43 times as much as that of Pinus tabulaeformis,and the activity of other enzymes in Quercus wutaishansea was 1.48 times as much as that of Pinus tabulaeformis on average.The addition of acidic substances mainly promoted the hydrolysis of cellulose,chitosan oligosaccharide and the activity of related enzymes in phosphorous organic compounds.The inhibiting effect strengthened as the amount of lime addition increased,but it was not significant and even shown the reverse trend when the addition amount was low.