珍贵固氮树种降香黄檀与二代巨尾桉混交种植对土壤微生物群落结构和功能的影响

Effects of mixture of valuable nitrogen-fixing tree species Dalbergia odorifera and second-generation Eucalyptus urophylla on structure and function of soil microbial community in subtropical China

关键词:  桉树人工林, 固氮树种, 土壤养分, 土壤微生物群落结构, 土壤酶活性, 南亚热带

Key words:  Eucalyptus plantation, N-fixing species, soil nutrient, soil microbial community structure, soil enzyme activity, south subtropical

摘要:

该研究以二代巨尾桉/降香黄檀混交林(MP)作为研究对象,并以邻接的二代巨尾桉纯林(PP)作为对照(CK),采用磷脂脂肪酸(PLFAs)和土壤酶活性分别表征土壤微生物群落结构和功能,重点探究南亚热带PP引入降香黄檀混交种植对土壤微生物群落结构和功能的影响。结果表明:(1)与PP相比,MP的土壤有机碳(SOC)、总氮(TN)、铵态氮(NH₄⁺-N)、硝态氮(NO₃^--N)和pH值分别显著或极显著增加了61.92%(P<0.05)、60.12%(P<0.05)、72.87%(P<0.01)、488.49%(P<0.01)和15.97%(P<0.05);(2)MP的真菌/细菌(F/B)显著降低,但总微生物生物量、革兰氏阴性菌/阳性菌(G^-/G⁺)并无显著变化;(3)MP的土壤微生物群落组成发生了显著变化,而pH值、NH₄⁺-N和凋落物质量(C/N_litter)是驱动其微生物群落组成发生变异的最显著性因子;(4)MP的β-葡萄糖苷酶(BG)和N-乙酰-葡萄糖苷酶(NAG)活性显著提高,而过氧化物酶(PER)活性显著降低,酚氧化酶(PO)和酸性磷酸酶(ACP)活性没有显著变化。该研究说明在连续短周期经营的桉树林中套种固氮树种降香黄檀,将可能是提高桉树林土壤质量的一种有效的经营管理措施。

Abstract:

In this study, the mixed second-generation Eucalyptus urophylla and Dalbergia odorifera plantation(MP)was taken as our object, and the adjacent pure second-generation E. urophylla plantation(PP)was taken as the control(CK). We used phospholipid fatty acids(PLFAs)as biomarkers to assess soil microbial community composition and measured soil enzyme activity as an indicator of soil microbial function. We focused on the effects of mixing N-fixing species with E. urophylla on soil microbial community composition and function in subtropical China. The results were as follows:(1)Soil organic carbon(SOC), total nitrogen(TN), ammonium nitrogen(NH₄⁺-N), nitrate nitrogen(NO₃^--N)and pH in MP were significantly or extremely significantly increased by 61.92%(P<0.05), 60.12%(P<0.05), 72.87%(P<0.01), 488.49%(P<0.01)and 15.97%(P<0.05)compared with that in PP, respectively.(2)The ratios of fungal-to-bacterial biomass(F/B)were significantly lower in MP than that in PP. However, there were no significant differences between the PP and the MP in total PLFAs and the ratios of gram-negative bacteria to gram-positive bacteria(G^-/G⁺).(3)The soil microbial community structure was significantly differed between MP and PP, and we found that the soil microbial community structure is strongly influenced by the variations of pH, NH₄⁺-N and ratios of organic carbon to total nitrogen in litter(C/N_litter).(4)The activities of β-glucosidase(BG)and N-acetyl-glucosidase(NAG)involved in soil carbon and nitrogen transformation were significantly higher, but the activities of peroxidase(PER)were lower in MP than that in PP. Nevertheless, the differences in phenoloxidase(PO)and acid phosphatase(ACP)activities were not significant between MP and PP. The results indicate that interplanting of nitrogen-fixing species in Eucalyptus plantations may be an effective management measure to improve soil quality in subtropical region.