Collaborative research: Effects of herbivores and mycorrhizas on N-fixers across soil and climate gradients in the Serengeti

合作研究：食草动物和菌根对塞伦盖蒂土壤和气候梯度固氮剂的影响

• 批准号: 0842327
• 负责人: Nancy Johnson
• 金额: $ 28.25万
• 依托单位: Northern Arizona University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-03-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0842327&HistoricalAwards=false
• 关键词: Collaborative; research; Effects; herbivores; mycorrhizas

Shortages of plant-available forms of soil nitrogen and phosphorus frequently limit plant production in natural and agricultural ecosystems. Microorganisms in the soil can help relieve this limitation, as nitrogen-fixing bacteria convert atmospheric nitrogen-gas into forms of nitrogen that plants can use, and mycorrhizal fungi help plants acquire phosphorus. These microorganisms are suspected to be important regulators of ecosystem productivity, but surprisingly little is known about what controls their abundance and activities. Research in the Serengeti grassland in East Africa provides an unprecedented opportunity to learn how herbivorous animals, the plants they consume, and soil microorganisms all interact together to generate a remarkably stable ecosystem. This research will apply cutting-edge molecular methods in two new manipulative experiments plus an ongoing long-term grazer exclosure experiment to assess how strongly herbivores and mycorrhizal fungi stimulate or limit the abundance and N-fixing activity of soil microbes, and whether these effects are mediated by rainfall and soil minerals. Human reliance on chemical fertilizers could be reduced if nitrogen-fixing bacteria and mycorrhizal fungi could be more effectively managed. This work will provide the scientific basis for developing management strategies to maximize the benefits of these soil organisms for sustainable production of food and fiber in semi-arid grasslands, savannas and other tropical ecosystems. The results will also make it possible to estimate more closely the contribution of natural nitrogen inputs, relative to elevated human-induced nitrogen deposition across the globe. The research will build scientific capacity in Tanzania.

植物可利用的土壤氮和磷的短缺常常限制了自然和农业生态系统中的植物生产。土壤中的微生物可以帮助缓解这一限制，因为固氮菌将大气中的氮气转化为植物可以利用的氮气，菌根真菌帮助植物获得磷。这些微生物被怀疑是生态系统生产力的重要调节者，但令人惊讶的是，人们对是什么控制了它们的丰度和活动知之甚少。对东非塞伦盖蒂草原的研究提供了一个前所未有的机会，让我们了解食草动物、它们所消耗的植物和土壤微生物如何相互作用，产生一个非常稳定的生态系统。这项研究将在两个新的操纵实验和一个正在进行的长期放牧封闭实验中应用尖端分子方法，以评估草食动物和菌根真菌对土壤微生物丰度和固氮活性的刺激或限制程度，以及这些影响是否由降雨和土壤矿物质介导。如果能更有效地管理固氮菌和菌根真菌，人类对化肥的依赖就会减少。这项工作将为制定管理战略提供科学依据，以最大限度地发挥这些土壤生物在半干旱草原、稀树草原和其他热带生态系统中可持续生产粮食和纤维的效益。这一结果还将使人们有可能更准确地估计自然氮输入相对于全球人类诱导的氮沉积增加的贡献。这项研究将在坦桑尼亚建立科学能力。