高寒草甸连续围封与施肥对土壤微生物群落结构的影响

Effects of continuous enclosure and fertilization on soil microbial community structure in alpine meadow

以放牧为对照,应用PLFA法分析研究了放牧、连续6年围封及围封内连续6年施肥后高寒草甸土壤微生物群落结构的变化.结果表明:围封和围封内施肥对不同土层各菌群和微生物总量均有显著影响,其对0～10cm土层微生物的影响大于10～20cm土层,不同土层的PLFA种类发生显著变化.围封和围封内施肥处理不同土层的革兰氏阴性菌(G-)含量均低于放牧;放牧0～10cm土层中细菌、真菌、革兰氏阳性菌(G+)、微生物总量大于围封和围封内施肥处理,但其放线菌生物量均低于围封和围封内施肥处理;在10～20cm土层中,各样地土壤中的G+无显著差异,围封土壤中的细菌、真菌、放线菌、微生物总量显著高于放牧,而围封内施肥后各菌群生物量及微生物总量明显下降.围封和围封内施肥不同土层的细菌/真菌均高于放牧;一般饱和脂肪酸/单烯不饱和脂肪酸(SAT/MONO)和革兰氏阳性菌/革兰氏阴性菌(G+/G-),围封处理均低于放牧,围封内施肥处理均高于放牧.连续围封和围封内施肥后降低了土壤微生物活性和土壤生态系统的稳定性.

By using phospholipid microbial community structure in fatty acid （PLFA） method, this paper studied the changes of soil an alpine meadow under six years continuous enclosure and its combination with fertilization, taking grazing area as the control. Both continuous enclosure and its combination with fertilization had significant effects on the microbial flora and total PLFA in differ- ent soil layers, and the effects were greater for 0-10 cm than for 10-20 cm soil layer. The species of PLFA in different soil layers also changed significantly. Under enclosure and its combination with fertilization, the number of gram-negative bacteria in different soil layers was lower than that of the control, and the numbers of bacteria, fungi, and gram-positive bacteria and the total PLFA in 0- 10 cm soil layer were also lower, but the number of actinomycetes was higher than that of the con- trol. In 10-20 cm soil layer, the number of gram-positive bacteria had no significant differences among different treatments, whereas the numbers of bacteria, fungi, and actinomycetes and the total PLFA were notably higher under enclosure but decreased markedly after fertilization. As compared with that of the control, the ratio of bacteria and fungi in different soil layers under enclosure and its combination with fertilization increased, the ratios of saturated fatty acid to monounsaturated fatty acid （SAT/MONO） and of gram-positive bacteria to gram-negative bacteria （ G＋/G- ） under enclo- sure were all lower, but those after fertilization were in adverse. It was suggested that continuousenclosure and its combination with fertilization led to the decline of soil microbial diversity and ac- tivity and soil ecosystem stability.