【个人简介】Dr. Zak Ratajczak is an ecologsts that has worked at in a range of systems from forests to agroecosystems. His degrees are in Biology and Earth Science at Vassar College, with a PhD in Biology at Kansas State University, and post-Doc experience at the University of Virginia, University of Wiscosin Madison. His is currently an Assistant Professor at Kansas State where, he works on using long-term data and remote to measure changes biodiversity and how local landuse decisions alter the resilience of grasslands to climate change.
【报告题目】Rewilding a Great Plains grassland by returning fire and bison: impacts on resilience and biodiversity
【报告摘要】Two hundred years ago, the Great Plains was one of the most extensive grasslands on earth, but then underwent several rapid and widespread changes, including: 1) shifts in fire regimes after Europeans seized Native Americans, 2) the near extermination of the remaining native megafauna (e.g. bison, elk), and 3) the subsequent conversion of most grasslands to row-crop agriculture. This study reports from a large-scale, long-term experiment in a landscape of tallgrass prairie that escaped agricultural conversion. The experiment uses large-scale manipulations to explore the interactive effects of several different prescribed burning frequencies and grazing by reintroduced native megafauna (Plains bison, Bison bison) versus grazer exclusion or grazing by domestic cattle (Bos taurus). We found that: 1) bison increased plant diversity 85% to 106% compared to the removal of large grazers, which is twice the increase that grazing by non-native cattle caused, and 2) these gains were resilient to the most extreme drought and most extreme wet summer in 40 years. However, bison and cattle have facilitated woody plant encroachment in areas burned very frequently (1 to 2 years), which reduces freshwater recharge and could undermine forage production. Returning natural disturbances, such as fire and grazing, is critical to maintain diverse and resilient Great Plains grasslands. However, novel interventions may be needed to because climate change and the effect of elevated atmospheric CO2 make woody plant encroachment likely in most land-use situations.
【个人简介】马妙君，博士，教授，博士生导师。曾获国家优秀青年科学基金、甘肃省青年科技奖，担任甘南草原生态系统国家野外科学观测研究站站长、甘肃省生态学会副理事长。立足青藏高原高寒地区，从事种子、群落、生态系统生态学方面的研究工作，包括种子（种子库、种子雨）在植物群落更新和物种多样性维持中的作用、高寒植物/群落物候，以及草地生态系统稳态、弹性和恢复机理方面的基础研究工作。以第一/通讯作者身份在Ecology Letters、Ecology、Journal of Ecology等主流生态学期刊发表论文40余篇。担任Ecological Applications和Journal of Plant Ecology等期刊的编委。
【报告题目】青藏高原东部高寒草地生态系统稳态转换及其相关机制
【报告摘要】由于过度放牧和全球气候变化，敏感又脆弱的高寒草地生态系统经历了严重退化，如何生态系统的保护和修复是长期备受关注的问题。越来越多的证据表明，许多生态系统都会呈现出多个稳态，然而，多稳态的识别和正反馈的量化是前沿且重要的科学问题。此外，土壤种子库作为生态系统恢复的重要资源，至今没有探索其在生态系统状态转换和弹性中的作用。我们通过在青藏高原东部地区的长期观测、大尺度调查，以及控制实验，发现了青藏高原高寒草甸、沼泽湿地生态系统存在多稳态并揭示了其反馈机制，初步揭示了种子库在草地生态系统稳态转换过程中的作用，为青藏高原高寒草地生态系统的保护和修复提供了科学依据。
