放牧对若尔盖高寒草甸土壤氮矿化及其温度敏感性的影响  

Effect of grazing intensity on temperature sensitivity of soil nitrogen mineralization in Zoigё alpine meadow

作　　者：赵宁[1,2] 张洪轩[3] 王若梦[4] 杨满业[3] 张艳[5] 赵小宁[1] 于贵瑞[1] 何念鹏[1] 

机构地区：[1]中国科学院地理科学与资源研究所,生态系统网络观测与模拟重点实验室,北京100101 [2]中国科学院研究生院,北京100049 [3]四川省草原科学研究院,成都611731 [4]山西农业大学动物科技学院,太谷030801 [5]北京林业大学林学院,北京100083

出　　处：《生态学报》2014年第15期4234-4241,共8页Acta Ecologica Sinica

基　　金：国家公益性行业(农业)科技专项(200903060);国家自然科学基金资助项目(31270519;31070431)

摘　　要：过度放牧和气候暖干化是若尔盖高寒草甸面临的严峻生态问题,它对土壤氮矿化过程的影响将在某种程度上决定高寒草甸生态系统的氮素利用状况。基于野外放牧实验,(禁牧(CK)、轻度放牧(L)、中度放牧(M)、重度放牧(H)),通过室内培养方法(5、10、15、20、25℃),探讨了不同放牧强度对若尔盖高寒草甸土壤氮矿化及其温度敏感性的影响。实验结果表明:放牧增加了土壤硝化速率和净氮矿化速率,其整体趋势为L>M>H>CK。培养温度较低时(5—10℃),温度升高对硝化和净氮矿化速率无显著影响,而培养温度较高时(15—25℃),温度升高显著增加了硝化和净氮矿化速率。土壤硝态氮和无机氮积累量随培养时间增长显著增加,而铵态氮无显著增长。此外,放牧显著提高了土壤氮矿化的温度敏感性,重度放牧样地的土壤具有最高的氮矿化温度敏感性(Q10=2.72)。上述结果预示着在未来温度升高情景下,重度放牧将使土壤氮矿化速率的增速更快,短期内将通过提高氮的可利用性促进植物生长,但长远而言可能加速土壤氮素流失,从而对植物生长和高寒草甸生态系统结构与功能造成负反馈效应。Overgrazing, climate changes, and drainage are the important disturbances and critical environmental problems for Zoige alpine meadow. These factors play an important role in regulating the soil nitrogen （N） cycle and to some extent influence alpine meadow ecosystem structure and function. In this study, we investigated the effect of grazing intensity on soil N mineralization and its temperature sensitivity （Q10）, by incubating soil samples collected during field grazing experiments in the Zoige alpine meadow. The results showed that grazing significantly influenced soil nitrification and net N mineralization rates, which followed the order of light grazing （L） 〉 moderate grazing （M） 〉 heavy grazing （H） 〉 no grazing （CK）. No differences were observed in the nitrification and net N mineralization rates at low temperatures （5- 10℃ ） ; however, significant differences were observed at high temperatures （ 15-25℃ ）. The accumulations of NO3-N and total inorganic N increased with increasing incubation time, whereas no significant differences were observed in the accumulations of soil NH4＋-N. Moreover, we found that the Q10 value for soil N mineralization significantly increased with increase in grazing intensity. Further, the Q10value in heavily grazed grasslands （ Q10 = 2.72） was significantly higher than that in other areas with lower grazing intensities. Thus, our results highlighted that grazing intensity has an important effect on the Q10 value in the Zoige alpine meadow, which is important for the N cycles in the area when considering heavy grazing and future scenarios on climate change. Further, we showed that the high acceleration of N mineralization rates in heavily grazed grasslands under the tendency of increasing temperatures in Zoige would be in favor of plant growth in a short-term view. However, in a long-term view, the situation would accelerate nitrogen loss in the Zoige alpine meadow and may negatively affect plant growth and maintenance of the ecosystem

关 键 词：放牧 温度 硝化速率 净氮矿化速率 高寒草甸 Q10 

分 类 号：S812.2[农业科学—草业科学]