The Soil Respiration And Microbial Biomass Carbon Of Typical Coastal Shelter Forests, Northern Jiangsu Province

There is large area of coastal shelter forests in China and few studies had been carried out on their effects as net carbon sink or source to the atmosphere.As one of the most important part of the carbon cycle,therefore,the study of soil respiration had great sense.Two typical shelter forests,the poplar plantation and water fir plantation,had been chosen to study the soil respiration in silting coast,northern Jiangsu Province.At the same time,soil microbial biomass carbon and aggregate-associated organic carbon that were tightly correlated with soil respiration had been studied.The results showed that:(1) The annual soi CO₂ efflux was 3792.2gm^-2 and 3610.2gm^-2 for the poplar and water fir plantation respectively.The soil respiration of both two plantations had significantly seasonal dynamics,which were greater in warmer months and less in cold months.And they were both mainly controlled by temperature,and less controlled by the soil water content.The soil respiration of water fir plantation had greater sensitivity to temperature than poplar plantation.(2) Both of the two components,the root respiration and the heterotrophic respiration,had the similar seasonal dynamics as the total soil respiration.The annual root respiration efflux was 767.5gm^-2 and 902.8gm^-2 for the poplar and water fir plantation,respectively.The contribution of root respiration to the total was 20.2%and 25.0%for poplar plantation and water fir plantation, respectively.Therefore,the contribution of the heterotrophic portion contributed more to the total than the root respiration.They were 3.9 and 3.0 times as large as the root respiration contribution for the Poplar plantation and Water fir plantation,respectively.(3) The results of the simulated soil mineralization experiments showed that the mineralization of the soil sampled from both plantations can be accelerated by temperature increase.Water content also had effects on soil mineralization rate:when it was at low level,its rose would increase the mineralization rate abruptly;when it was at higher,its rose would slightly increase the mineralization rate,and we could conclude with our results that when it was bigger than a critical value,its rose would decrease the mineralization rate.(4) Soil microbial biomass carbon decreased with the soil depth.And it was significantly correlated positively with SOC,C:N ratio and total N content and negatively with pH and soil bulk density.And it was more correlated with SOC content than other factors,which indicated that the soil microbial biomass carbon content was mostly depended on SOC content.