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Increased N2O emission induced by long-term nitrogen fertilization has become an urgent ecological environment issue concerned by more and more scientists with regards to global climate change.The objective of this study was to explore the community dynamics of denitrifiers as well as their response to environmental parameters and plant community along different fertilizer gradients (0, 30, 60, 90, 120 g m2 year-1) on three sampling dates in Tibetan alpine meadow soil, China.The abundance and community structure ofdenitrifiers based on nirK gene were assessed using quantitative polymerase chain reaction (qPCR) and restriction fragment length polymorphism (RFLP), respectively.Our results showed that long-term fertilization did not change the gene copy numbers of nirK gene-bearing denitrifiers (7.43 (± 1.05) × 106 to 2.33 (±0.15) × 107 copies g-1 dry soil) significantly (p > 0.05).However, the community composition of nirK gene-bearing denitrifiers differed in different fertilization treatments.Notably, the community size (only in three unfertilized plots) and composition of nirK gene-bearing denitrifiers varied over the sampling dates, soil moisture、 organic C and N contents were very important in structuring the community composition of nirK gene-bearing denitrifiers (p < 0.05).Furthermore, long term fertilization significantly altered the diversity and community composition of plant (p < 0.05).The changes of nirK community composition was significantly related to plant diversity (p < 0.05), but not plant community (p > 0.05).These results indicated that longterm fertilization changed the community structure of denitrifiers and plant, in addition, the abundance and community composition of denitrifiers had significant seasonal changes (p < 0.05).