| Soil acidification directly affects soil nutrients availability,induces soil-borne diseases of crops,and increases the bioavailability of pollutants such as heavy metals,thereby threatening agricultural productivity and food safety.Lei Bamboo(Phyllostachys praecox)forest is one of the important economic forests in the mountainous areas of southern China.Long-term intensive management,however,has caused problems such as soil acidification,fertility decline,and deterioration of the micro-ecological environment in the Lei Bamboo forests,which severely restricted their sustainable development.How to amend soil acidification and restore and imrove soil biological functions in Lei Bamboo forests is a technical problem that plagues local agriculture,forestry management departments and farmers.The application of lime and biochar has been shown to have a positive effect on improving the acidification of farmland soil,enhancing soil quality and crop yield.However,at the field scale,whether the application of lime and biochar can effectively ameliorate the soil acidification,restore and improve soil microbial biomass and function in Lei bamboo forest are still unclear.In view of this,this study performed a field experiment in a Lei bamboo forest allocated in Taihuyuan Town,Lin'an District,Hangzhou City,Zhejiang Province.Field treatments were as follows control(CK);biochar amendment at rates of 10 t ha-1(B1);biochar amendment at rates of 20 t ha-1(B2);a single application of lime at 4 t ha-1(L);co-application of biochar at rates of 10 t ha-1 and lime at rates of 4 t ha-1(B1L);co-application of biochar at rates of 20 t ha-1 and lime at rates of 4 t ha-1(B2L).Changes in soil physical and chemical properties,microbial biomass,soil enzyme activity and basal respiration were determined after 1,3,6,and 12 months to investigate the effects of lime and biochar on the soil chemical and biological improvement of Lei bamboo forest soil.Our main results are as follows(1)The application of lime and biochar alone and in combination significantly increased soil pH,reduced soil exchangeable H+,Al3+ content and total exchangeable acid content,and ameliorated soil acidification in Lei bamboo forest.Compared with the control,lime application significantly(P<0.05)increased soil pH by 1.7?2.0 units in the four periods,while single application of biochar also significantly increased pH(by 0.12?0.51)and reduced exchangeable acid(by 17.62%?44.88%)and exchangeable aluminum(by 21.58%?48.97%).In comparison with lime,biochar had a smaller reduction effect on soil acidity.Lime and biochar have a significant interactive effect on exchangeable acid and exchangeable Al3+ contents(P<0.05),and their combination is more effective to reduce soil potential acidity(2)The single application of lime and biochar and their combined application improved soil physical and chemical properties to varying degrees,and the combined application also promoted the soil carbon content.The application of lime has no significant effect on the soil bulk density but increased the electrical conductivity,while the application of biochar reduced the soil bulk density(by 5.47%?13.34%)with no effect on the electrical conductivity.The application of biochar and lime alone and in combination significantly increased soil moiture(by 5.47%?56.83%).Lime application had no significant effect on soil total N,available K and available P,while biochar application increased soil total N(by 8.61%?14.79%)and available K contents(by 8.79%?70.76%)after 12 months.Single application of lime reduced the soil organic C content(by 0.67%?9.75%),while the single application of biochar significantly increased the soil organic C content(by 15.24%?27.84%)Biochar and lime has a significant interactive effect on soil organic C(P<0.05).During the first 6 months of the experiment,the single application of lime significantly increased the content of easily decomposable C components and promoted the conversion of soil recalcitrant C to easily decomposable C,whereas the application of biochar reduced the content of soil dissolved organic C(DOC)(by 3.37%?30.08%)and increased the content of recalcitrant C(by 53.09%-128.12%)(3)Application of lime and biochar increased soil microbial biomass,but their responses to lime and biochar varied depending on the different groups of microorganisms.The application of lime alone greatly increased soil MBC(by 72.11%?143.28%),MBN(by 76.43%?460.97%),copies of bacterial 16S rRNA(by 43%?266%),fungal ITS(by 41%?145%)and archaeal 16S rRNA(by 115%?289%)genes,while biochar treatment only slightly increased the MBN content and bacterial and fungal gene copy numbers.Changes in soil microbial biomass were significantly correlated with soil moisture content,soil pH,exchangeable acid and DOC content.The decrease in soil acidity and changes in DOC content caused by the application of biochar and lime are key driving factors of microbial biomass(4)The application of lime and biochar significantly changed the activities of soil enzymes involved in C,N and P cycling,but their responses to the application of lime and biochar also also varied depending on the enzymes.The single application of lime greatly increased the activities of?-glucosidase(by 50.97%?209.25%)and ?-N-acetylglucosaminidase(by 20.96%-230.97%),leucine aminophthalase(by 7.59%?59.02%),while reduced the activity of acid phosphatase(by 40.13%?64.10%).In contrast,biochar application had a week effect on the enzyme activities.The combined application of biochar and lime reduced the activities of ?-glucosidase(by 12.37%?25.47%),?-glucosidase(by 23.14%?58.70%),cellobiohydrolase(by 6.15%?55.33%),?-xylanase(by 3.32%?71.70%),leucine aminophthalase(6.90%?23.04%),?-N-acetylglucosaminidase(by 5.02%?111.11%).Biochar and lime had significant interactive effects on soil enzyme activities(except the acid phosphatase).Changes in soil enzyme activity have strong correlations with soil moisture content,pH,DOC and microbial abundances.(5)Soil basal respiration rates were significantly increased by 32.76%?54.15%the application of lime alone during the first 6 months.While the application of biochar alone had no significant effect on the soil respiration rates.Compared with the single lime application,the combined application of biochar and lime significantly reduced soil respiration rates by 9%?27.65%.Therefore,the combined application of biochar can offset the promoting effect of lime on soil respiration rate to a certain extent.In addition,soil respiration rates differed among different sampling periods,and the promoting effect of lime on soil respiration gradually decreased after its soil incorporation.In summary,our study suggests that the application of lime and biochar can ameliorate soil acidification,improve soil nutrients and biological functions in Lei bamboo forests.Compared with biochar,lime had a higher advantage in promoting soil pH,microbial biomass and enzyme activity,but it may not be conducive to the retention of soil organic C;whereas biochar can reduce soil bulk density,improve soil structure and nutrients,and its co-application of lime can significantly increase soil organic C pool and offset the promotion effect of lime on the soil respiration rate.Therefore,the combined application of biomass charcoal and lime can provide a theoretical reference for ameliorating soil acidification and increasing soil C sequestration in Lei bamboo forests. |
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