| This project aims to evaluate the differences in carbon sequestration,soil organic carbon storage and its stability,as well as soil nutrients of two different stands?or vegetation restoration patterns?in Nanjing Zijin Mountain;and to find the causes of differences in soil organic carbon pool.We analysed carbon storage,soil nutrients contents and their distributions of two 70-year forests in different types,i.e.deciduous broad-leaved?DBL?forest mainly mixed by Celtis sinensis and Aphananthe aspera,and conifer-broadleaf?CBL?forest mainly mixed by Pinus massoniana and Liquidambar formosana.We also compared the differences in soil organic carbon pool and its stability,and interpreted their causes basing on common significantly correlated factors found in pearson correlation analyses.Our objective is to provide suggestions for evaluating ecosystem service value of urban landscape soil conservation forest,and to provide scientific bases for its construction.The main results are as follows:?1?The DBL forest performed better in soil nutrient reservation and available nutrients release than CBL forest.The contents of soil organic matter?SOM?,total nitrogen?TN?,total phosphorus?TP?and total potassium?TK?respectively were 66.89,3.07,0.31 and 3.28 g·kg?1 in0-40 cm soil depth of DBL forest,and the contents of ammonium nitrogen,nitrate nitrogen,available phosphorus and available potassium were 2.52,11.17,5.23 and 11.88 mg·kg?1,respectively.Those soil properties in CBL forest were 60.20,2.57,0.25,3.20 g·kg?1,and 2.05,12.32,5.24,11.60 mg·kg?1,respectively.Compared to the CBL forest,DBL forest had 11.11%,19.46%,24%,2.5%,22.93%and 2.41%more SOM,TN,TP,TK,ammonium nitrogen and available potassium,respectively,but 9.33%and 0.19%less nitrate nitrogen and available phosphorus,respectively.?2?The DBL forest had larger capacities in carbon storage and soil carbon sequestration,and also performed better in long-term organic carbon sequestration than CBL forest.The organic carbon storage of CBL forest and its soil were 229.44 and 107.06 t·hm?2 respectively.On the other hand,the corresponding storage in DBL forest increased by 2.89%and 21.9%,were 236.28and 130.49 t·hm?2 respectively.The proportion of soil organic carbon storage also was increased by 8.56%in DBL forest carbon storage.?3?The DBL forest was a more stable soil organic carbon pool than CBL forest.The contents of soil dissolved organic carbon?SDOC?,soil microbial biomass carbon?SMBC?,soil readily oxidizable organic carbon?SROC?,coarse soil particulate organic carbon?CSPOC?,fine soil particulate organic carbon?FSPOC?,soil heavy-fraction organic carbon?HFOC?were 0.12,0.26,12.08,18.32,12.31 and 36.94 g·kg?1 in 0-40 cm soil depth in DBL forest,and those were0.14,0.17,9.49,13.98,8.51 and 27.68 g·kg?1 in CBL forest,respectively.The contents of SMBC,SROC,CSPOC,FSPOC,HFOC increased by 52.9%,27.3%,31.04%,44.65%and33.45%,and their proportions also increased by 0.07%,1.1%,31.04%,44.65%and 33.45%in the SOC content of DBL forest,as compared to those in the SOC content of CBL forest.In the SOC content of DBL forest,the content and proportion of SDOC decreased by 14.3%and 0.17%,respectively.According to the correlation analyses,the changes of active organic carbon fractions,such as SDOC,SMBC and SROC,were not significant?p>0.05?;while the changes of slow organic carbon fractions,such as CSPOC,FSPOC and HFOC,were significant?p<0.05?.In addition,the active fractions only accounted for a small part of SOC,and the slow fractions accounted for the major part.?4?The difference in soil carbon pool between DBL and CBL forests was mainly due to the contents and stability of soil organic carbon.In other words,it was caused by the differences in SOC,TN,SROC,CSPOC,FSPOC and HFOC.In conclusion,the climax community such as deciduous broad-leaved mixed forest,which was made up of native tree species,was more conducive to carbon sequestration and soil nutrient conservation in Nanjing hilly and mountainous areas.Therefore,the deciduous broad-leaved forest type is more suitable for urban forest construction in Nanjing. |
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