红壤侵蚀区芒萁对土壤微生物群落结构的影响

土壤微生物是反映土壤质量状况的重要指标,研究侵蚀地植被恢复后土壤微生物群落结构的变化对深入认识土壤质量的演变具有重要意义。对比分析了未治理地(Y0)、治理13年(Y13)和31年(Y31)的马尾松林(Pinus massoniana)林下芒萁(Dicranopteris dichotoma)覆盖地(NRd)、去除芒萁覆盖地(Rd)与林下裸地(CK)土壤微生物生物量和群落结构差异,结果表明:林下裸地土壤微生物生物量碳(MBC)、微生物生物量氮(MBN)和总微生物磷脂脂肪酸量(总PLFAs)的含量均显著低于芒萁覆盖地,且去除芒萁4个月后,MBC和总PLFAs均有降低趋势,表明芒萁覆盖对土壤微生物生物量具有重要影响;林下芒萁覆盖地土壤革兰氏阳性菌(GP)、革兰氏阴性菌(GN)、丛植菌根真菌(VAM)、真菌(Fungi)、放线菌(ACT)的PLFAs含量显著高于林下裸地(Y13例外),去除芒萁4个月后,各值均有有接近林下裸地的趋势;芒萁覆盖地真菌/细菌的比值(F/B)均显著高于林下裸地(P0.05),芒萁覆盖地革兰氏阳性菌/革兰氏阴性菌的比值(GP/GN)、饱和直链脂肪酸/单不饱和脂肪酸的比值(sat/mono)和(cy17:0+cy19:0ω8c)/(16:1ω7c+18:1ω7c)(cy/pre)显著小于林下裸地(P0.05),去除芒萁4个月后,芒萁覆盖地土壤cy/pre显著升高(P0.05)(Y13例外),意味着芒萁覆盖地土壤生态系统更稳定,土壤的养分可利用性更高,微生物生物量和群落结构更丰富,活性更强;皮尔逊相关分析和冗余分析发现,土壤理化性质与土壤微生物生物量和群落结构关系密切,土壤C/N、p H和氮素水平是调控芒萁覆盖下土壤微生物生物量和群落结构的主要生态因子。

Effect of Dicranopteris dichotoma on soil microbial community structure in red soil erosion area

Soil microorganisms play a key role on soil carbon (C) and nutrient cycling, which can serve as an indicator of the status of soil quality. Therefore, it is crucial to study the soil microbial community composition to understand the evolvement in soil quality owing to vegetation restoration. The aim of the study was to investigate the effect of the fern species Dicranopteris dichotoma on the soil microbial biomass and community structure. The typical sequence of vegetation restoration (Y0, without measures of ecological restoration; Y13, restoration for 13 years; Y31, restoration for 31 years) was selected as the research object in Hetian town, Changting county, Fujian province. At each experimental site, the soil was subjected to three treatments-NRd, not removed D. dichotoma; Rd, removed D. dichotoma; and CK, control. Our results indicated that soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and total phospholipid fatty acid(PLFAs) under CK treatment were significantly higher than those under NRd and Rd treatments. Soil MBC and total PLFAs decreased significantly (P < 0.05) after Rd treatment for 4 months, indicating that D. dichotoma had a significant effect on soil microbial biomass. PLFAs of Gram-positive and Gram-negative bacteria, arbuscular mycorrhizal fungi, fungi, actinomycetes under NRd treatment were significantly lower than those under CK treatment (except for Y13). The ratios of soil Gram-positive bacteria to Gram-negative bacteria, cyclopropyl to cyclopropyl precursor, and saturated straight chain fatty acid to monounsaturated fatty acids were significantly decreased under NRd treatment compared to those under CK treatment; however, the fungi to bacteria ratio was significantly increased under NRd treatment (P < 0.05), indicating that the soil microbial biomass and community structure was much more abundant under NRd treatment, and high microbial activity was also noted. The results of Pearson correlation analysis and Redundancy analysis suggested that the soil chemical and physical properties were significantly and positive related to the soil microbial biomass and community structure. Therefore, soil C:N ratio, pH, and N status are key factors that affect the soil microbial community in the red soil erosion area.