雪被去除对川西高山冷杉林冬季土壤微生物生物量碳氮和可培养微生物数量的影响

Effects of snow pack removal on soil microbial biomass carbon and nitrogen and the number of soil culturable microorganisms during wintertime in alpine Abies faxoniana forest of western Sichuan,Southwest China

为了解气候变暖情景下雪被减少对冬季土壤微生物特征的影响,采用人工遮雪的方法,研究了雪被去除对原始冷杉林土壤微生物生物量和可培养微生物数量的影响.结果表明:雪被去除显著影响土壤微生物生物量碳(MBC)和氮(MBN)以及可培养细菌和真菌数量,但土壤微生物在雪被覆盖不同阶段具有不同的响应特征.在雪被去除处理下,土壤有机层MBC和MBN在雪被形成初期和雪被融化前期显著降低,而在雪被覆盖期和雪被融化后期显著增加;在雪被形成初期至雪被覆盖期,可培养细菌数量都显著降低,但可培养真菌数量都显著增加.雪被融化后,雪被去除显著降低土壤有机层MBC和可培养真菌数量,显著增加可培养细菌数量,对MBN无显著影响.矿质土壤层MBC、MBN和可培养微生物数量在雪被去除下的变化趋势与土壤有机层基本一致,但波动较小.雪被去除还改变了川西高山冷杉林冬季土壤微生物类群比,提高了土壤可培养真菌数量的冬季优势.

To understand the effects of the lack of snow pack under global warming on the characteristics of soil microorganisms during wintertime,a snow-shading experiment was conducted in a primary fir（Abies faxoniana） forest after snow pack removal,with the soil microbial biomass carbon（MBC） and nitrogen（MBN） and soil culturable microorganisms（bacteria and fungi） at the stages of snow forming,snow covering,and snow melting investigated.Snow pack removal had significant effects on the soil MBC and MBN and the number of soil culturable bacteria and fungi,but the responses of the culturable microorganisms differed with the stages of snow-shading.Under the condition of snow pack removal,the MBC and MBN in soil organic layer decreased significantly at the early stages of snow forming and snow melting but increased significantly at snow covering stage and at the later stage of snow melting,and the number of culturable bacteria decreased significantly from the early stage of snow forming to the stage of snow covering while that of culturable fungi had a significant increase from the early stage of snow forming to the stage of snow melting.After snow melting,the MBC and the number of culturable fungi in soil organic layer had a significant decrease,the number of cultural bacteria was in adverse,but the MBN had less change.The MBC and MBN and the number of culturable microorganisms in soil mineral layer had the similar variation trends as those in soil organic layer,but the fluctuations were smaller.It was suggested that snow pack removal changed the ratio of culturable bacteria to culturable fungi,showing positive effects on the number of soil culturable fungi during wintertime in alpine Abies faxoniana forest of western Sichuan.