氮添加对不同退化程度高寒草地生态系统的影响
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摘要
为促进退化草地生态系统快速恢复,本研究以若尔盖高原未退化、轻度、中度、重度退化草地为研究对象,进行了0(N0)、50(N1)、100(N2)、200(N3)kg·hm-24种不同浓度的氮素添加试验,探讨不同退化草地土壤碳氮含量、植被群落结构及功能对氮添加的响应差异。结果表明,1)氮添加对土壤碳、可利用氮的影响与退化程度有关;N2水平主要促进了未退化、轻度退化草地的碳和可利用氮含量的累积,N1水平主要促进了中度、重度退化草地土壤碳和可利用氮含量的累积,继续施氮则降低。2)氮添加增加了不同退化程度草地莎草科、禾本科植物的功能群重要值,降低了杂类草重要值,显著影响了中度、重度退化草地的功能群重要值(P<0.05),N3水平下莎草科、禾本科植物功能群重要值最大,杂类草功能群重要值最小;氮添加除显著降低了重度退化草地的Shannon-Wiener多样性指数、Pielou均匀度(P<0.05)外对其他样地均无显著影响(P>0.05)。3)氮添加均增加了不同退化程度草地的地上总生物量、莎草科与禾本科植物功能群的生物量,N2水平显著增加了未退化、轻度退化草地的莎草科、禾本科功能群的生物量(P<0.05),继续施氮则降低;N3水平显著增加了中度、重度退化草地的地上总生物量以及莎草科、禾本科功能群生物量(P<0.05),不同退化程度草地在氮添加后杂类草生物量均显著降低(P<0.05)。综上可知,N2水平的氮处理有利于防止未退化、轻度退化草地的进一步退化,为确保草地可持续发展并防止土壤养分的过分流失,应对中度和重度退化草地先进行低水平(N1)的氮添加处理。
In order to promote the rapid recovery of degraded grassland ecosystems,the effects of different levels of nitrogen application 0(N0),50(N1),100(N2),and 200(N3)kg·ha-1 were tested in different habitats in the Zoige Plateau,including an undegraded grassland,a lightly degraded grassland,a moderately degraded grassland,and a severely degraded grassland.The differences in soil carbon and nitrogen content,and vegetation community structure and function in response to nitrogen addition were investigated.The results showed that:1)the effect of nitrogen addition on soil carbon and available nitrogen is related to the degree of degradation.The N2 level mainly promoted the accumulation of carbon and available nitrogen in the undegraded grassland and lightly degraded grassland.The N1 level mainly promoted the accumulation of soil carbon and available nitrogen in moderately and severely degraded grasslands,and continued nitrogen application decreased.2)Nitrogen addition increased the important value of sedge and grass functional groups under different degrees of degeneration and reduced the important value of the weeds(P<0.05).In the N3 level,the important values of sedge and grass functional groups were the largest,whereas those of the functional groups of weeds were the lowest.The addition of nitrogen decreased the Shannon-Wiener diversity index and Pielou evenness significantly(P<0.05)in the severely degraded grassland,and it had no significant effect on the other plots.3)Nitrogen addition increased the total aboveground biomass of grasslands with different degrees of degradation.The N2 level significantly increased the biomass of the sedge and grass functional groups in the undegraded and lightly degraded grasslands with a decrease in nitrogen application.The N3 level significantly increased the aboveground biomass of sedges and grass functional groups in moderately and severely degraded grasslands,whereas the biomass of weeds became significantly lower.In conclusion,nitrogen treatment at N2 level is conducive to preventing further degradation of undegraded and lightly degraded grassland.In order to ensure sustainable development and prevent excessive loss of soil nutrients,moderately and severely degraded grasslands should be treated with a low level(N1)of nitrogen.
In order to promote the rapid recovery of degraded grassland ecosystems,the effects of different levels of nitrogen application 0(N0),50(N1),100(N2),and 200(N3)kg·ha-1 were tested in different habitats in the Zoige Plateau,including an undegraded grassland,a lightly degraded grassland,a moderately degraded grassland,and a severely degraded grassland.The differences in soil carbon and nitrogen content,and vegetation community structure and function in response to nitrogen addition were investigated.The results showed that:1)the effect of nitrogen addition on soil carbon and available nitrogen is related to the degree of degradation.The N2 level mainly promoted the accumulation of carbon and available nitrogen in the undegraded grassland and lightly degraded grassland.The N1 level mainly promoted the accumulation of soil carbon and available nitrogen in moderately and severely degraded grasslands,and continued nitrogen application decreased.2)Nitrogen addition increased the important value of sedge and grass functional groups under different degrees of degeneration and reduced the important value of the weeds(P<0.05).In the N3 level,the important values of sedge and grass functional groups were the largest,whereas those of the functional groups of weeds were the lowest.The addition of nitrogen decreased the Shannon-Wiener diversity index and Pielou evenness significantly(P<0.05)in the severely degraded grassland,and it had no significant effect on the other plots.3)Nitrogen addition increased the total aboveground biomass of grasslands with different degrees of degradation.The N2 level significantly increased the biomass of the sedge and grass functional groups in the undegraded and lightly degraded grasslands with a decrease in nitrogen application.The N3 level significantly increased the aboveground biomass of sedges and grass functional groups in moderately and severely degraded grasslands,whereas the biomass of weeds became significantly lower.In conclusion,nitrogen treatment at N2 level is conducive to preventing further degradation of undegraded and lightly degraded grassland.In order to ensure sustainable development and prevent excessive loss of soil nutrients,moderately and severely degraded grasslands should be treated with a low level(N1)of nitrogen.
引文
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