增温对南亚热带季风常绿阔叶林土壤微生物群落的影响

Effects of Warming on Soil Microbial Communities of A Subtropical Monsoon Evergreen Broad-leaved Forest in Southern China

土壤微生物是森林生态系统中重要的分解者,参与生物圈的物质循环和能量流动,对温度变化响应较为敏感。以鼎湖山南亚热带季风常绿阔叶林为研究对象,基于野外增温实验平台,采集0-10 cm和10-20 cm土层的土壤样品,采用磷脂脂肪酸(PLFA)方法并结合土壤理化性质的监测,探究气温上升对土壤微生物群落的影响。结果表明:(1)增温处理使0-10 cm和10-20 cm土层月均温分别显著上升1.24℃和1.17℃,土层湿度变化不显著;(2)增温显著增加了土壤硝氮含量,但对其他理化性质作用不明显;(3)增温组土壤微生物生物量碳(MBC)、微生物生物量氮(MBN)、微生物生物量碳氮比(C/N)以及微生物总磷脂脂肪酸含量与对照组差异不显著;(4)增温显著改变了土壤微生物群落结构,使细菌相对丰度、细菌真菌之比(B/F)以及革兰氏阳性菌革兰氏阴性菌之比(G^+/G^-)显著增加,降低了真菌和丛枝菌根真菌的相对丰度;(5)进一步分析表明,土壤硝态氮和有机碳是影响土壤微生物群落结构变异的主要因子,两者共同解释了微生物群落结构60.5%的变异度。以上研究结果表明,尽管增温对南亚热带季风常绿阔叶林土壤微生物生物量作用不明显,但可通过对土壤硝氮和土壤有机碳含量的影响引起土壤微生物群落结构及其相对丰度的改变,微生物群落结构和相对丰度的变化又将通过影响微生物对土壤碳氮的同化作用,最终影响土壤的碳氮过程。

Soil microorganism,as an important decomposer,plays critical roles in the nutrient cycling and energy flow in forest ecosystem,which is often dependence of temperature.We established a field warming experiment to explore the effects of warming on soil microbial communities of the monsoon evergreen broad-leaved forest in Dinghushan National Nature Reserve in south subtropical region of China.Soil samples were collected in layers of 0 10 cm and 10 20 cm to monitor structure of soil microbial community by using the phospholipid fatty acids(PLFA)as biomarkers.The results showed that:(1)The warming treatment did not significantly alter soil moisture in both soil layers,while averagely increased soil temperature by 1.24℃in 0 10 cm and 1.17℃in 10 20 cm soil layers,respectively.(2)The warming treatment significantly increased soil nitrate content,but no significant effect was found on other soil physical and chemical properties.(3)The warming treatment has no significant effect on soil microbial biomass carbon(MBC),microbial biomass nitrogen(MBN),the ratio of MBC to MBN or microbial total PLFAs content.(4)The warming treatment significantly changed soil microbial community structure,with increases in the relative abundance of bacteria,the ratio of bacteria to fungi and the ratio of Gram-positive bacteria to Gram-negative bacteria but decreases in the relative abundance of fungi and arbuscular mycorrhizal fungi.And(5)further analysis showed that soil nitrate nitrogen and soil organic carbon was the most important influencing factors,explaining 60.5% variability of microbial community structure under the warming treatment.These findings indicate that climate warming may alter soil microbial community structure instead of soil microbial biomass by influencing soil nitrate nitrogen and soil organic carbon in the southern subtropical monsoon evergreen broad-leaved forest,in turn resulting in an effect on soil carbon and nitrogen processes by microbial assimilation.