退化马尾松林恢复过程中芒萁覆盖对土壤微生物生物量碳氮及其周转的影响

Effects of Dicranopteris Dichotoma Covered on Soil Microbial Biomass Carbon and Nitrogen and Their Turnover During Restoration of Degraded Pinus Massoniana Forest

为探究侵蚀退化红壤马尾松林恢复过程中林下芒萁对土壤微生物生物量碳氮月动态及其周转的影响,以不同恢复年限的马尾松林为研究对象,对比分析马尾松林恢复过程中林下保留芒萁、去除芒萁处理和林下裸地土壤中12个月的土壤微生物生物量碳(MBC)和微生物量氮(MBN)含量及其周转速率、周转时间和流通量,并分析其与土壤理化性状的关系。结果表明:(1)保留芒萁覆盖处理的MBC和MBN平均含量分布比林下裸地提高26.99%~277.31%和13.54%~173.39%,而去除芒萁处理分布比保留芒萁处理降低12.29%~27.01%和5.02%~28.45%,差异均随恢复年限呈先降低后增加的趋势。(2)所有处理的土壤微生物量碳氮季节动态均表现为春夏季较高,秋冬季较低的趋势,进入生长季前的土壤微生物量碳氮含量更能反映该地区的平均水平。(3)在退化马尾松林恢复过程中,芒萁覆盖降低土壤微生物生物量碳氮周转速率,增加周转时间,提高土壤微生物生物量碳氮含量和流通量,促进土壤有机质的积累和养分释放。相关分析和逐步回归分析表明,MBC、MBN流通量分别与DOC、DON呈显著正相关,周转速率分别与铵态氮(NH_(4)^(+)-N)和TN呈显著负相关,表明土壤碳和氮及其有效性是影响土壤微生物量周转的关键因素。

In order to explore the effects of Dicranopteris dichotoma on the monthly dynamics and turnover of soil microbial biomass carbon and nitrogen in the restoration process of Pinus massoniana forest in eroded degraded red soil,the P.massoniana forests with different restoration years were used as the research object.The contents of soil microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN),turnover rate,turnover time and flux in the soil of 12 months in the soil of P.massoniana forest with D.dichotoma,removal of D.dichotoma and bare land were compared and analyzed,and their relationships with soil physical and chemical properties were analyzed.The results showed that:(1)The average content of MBC and MBN in the treatment of retaining D.dichotoma was 26.99%~277.31% and 13.54%~173.39% higher than that in the bare land,while the distribution of the treatment of removing D.dichotoma was 12.29%~27.01% and 5.02%~28.45% lower than that of retaining D.dichotoma.(2)The seasonal dynamics of soil microbial biomass carbon and nitrogen in all treatments showed a trend of higher in spring and summer and lower in autumn and winter,the soil microbial biomass carbon and nitrogen content before entering the growing season can better reflect the average level of the region;(3)In the restoration process of degraded P.massoniana forest,D.dichotoma coverage decreased soil microbial biomass carbon and nitrogen turnover rate,increased turnover time,increased soil microbial biomass carbon and nitrogen content and flux,and promoted soil organic matter accumulation and nutrient release.Correlation analysis and stepwise regression analysis showed that MBC and MBN flux were significantly positively correlated with DOC and DON,respectively,and turnover rate was significantly negatively correlated with NH_(4)^(+)-N and TN,respectively,indicating that soil carbon and nitrogen and their availability were key factors affecting soil microbial biomass turnover.