SGER: Ecosystem Recovery Following Three Centuries of Livestock Grazing in Central New Mexico

Sevilleta LTER研究中心已成为一个区域联络点， 争论集中在是否完全从放牧（避难所）释放 对多样性和初级生产力是有害的。 而 详细的研究正在发生在塞维利亚，有几个 相邻放牧地与近期放牧地的比较研究 从放牧压力中释放出来 目前的塞维利亚LTER 该计划正在一个本身可能正在经历 三个多世纪以来的连续变化 密集的牲畜放牧。 必须隔离和 了解放牧后塞维利亚景观的变化， 确定未来长期生态系统变化的来源; 如果不分离放牧的影响， 将可观察到的生态系统变化归因于其他原因，例如 气候变化或人为因素，将被混淆。 塞维利亚国家野生动物保护区成立于1973年， 并在该年设置了牲畜隔离栏。 的 1972年的夏天，也就是牲畜迁移的前一年， 异常潮湿的时期，随后是一个强大的厄尔尼诺现象， 1972 - 1973年的冬、春。 一个非常潮湿的 夏季之后是潮湿的春季，可能只有20年的频率 格局 鉴于水分状况对干旱地区的重要性， 生态系统功能，塞维利亚的先决条件 1973年的选举可能促成了一种不寻常的"继任轨迹" 如果不是不可能的话， 在实地进行实验。 然而，有机会进行这样的实验， 由于异常潮湿的天气模式， 1991 - 92年发生在新墨西哥州中部。 塞维利亚 1991年经历了一个极度潮湿的夏天。 塞维利亚是 目前正处于一个强大的厄尔尼诺现象， 冬春滋润。 目前的天气状况 为模拟过渡期的研究奠定了基础， 发生在1973年之后的塞维利亚号上 的这种组合 气候事件可能很少发生（每隔几年发生一次 因此，立即开展研究非常重要。 利用这种不寻常的情况 该SGER项目基于（1）现场的基本需求- 关于牲畜迁移对生态系统影响的具体信息， 加上（2）天气条件的巧合发生 与近20年前的情况非常相似

Sevilleta LTER study site has become a regional focal point in a debate centered on whether total release from grazing (a refuge) is detrimental to diversity and primary productivity. While detailed studies are occurring on the Sevilleta, there are few comparative studies on adjoining grazed land or land recently released from grazing pressure. The current Sevilleta LTER Program is being conducted on a site that may itself be undergoing successional changes following release from over three centuries of intensive livestock grazing. It is imperative to isolate and understand the post-grazing changes on the Sevilleta landscape in order to identify future sources of long-term ecosystem changes; without a separation of grazing influences, efforts to attribute observable ecosystem changes to other causes, such as climate change or anthropogenic factors, will be confounded. The Sevilleta National Wildlife Refuge was established in 1973, and livestock exclusion fences were erected in that year. The summer of 1972, one year prior to livestock removal, was an unusually wet period, and was followed by a strong El Nino during the winter-spring of 1972-73. The combination of a very wet summer followed by a wet spring may have only a 20 year frequency pattern. In view of the importance of moisture regimes on arid ecosystem functioning, the antecedent conditions on the Sevilleta in 1973 may have fostered an unusual "successional trajectory" that would be difficult, if not impossible, to simulate experimentally in the field. However, an opportunity to perform just such an experiment has arisen as a result of the unusually wet weather patterns that have occurred in central New Mexico in 1991-92. The Sevilleta experienced an extremely wet summer in 1991. The Sevilleta is presently in the midst of a strong El Nino that is producing late winter and spring moisture. The current weather conditions have set the stage for studies that could simulate the transition that occurred on the Sevilleta after 1973. This combination of climatological events may occur only rarely (once every few decades) and it is important to initiate studies immediately to take advantage of these unusual circumstances. This SGER project is based on (1) the fundamental need for site- specific information on ecosystem effects of livestock removal, coupled with (2) the coincidental occurrence of weather conditions that are very similar to those of nearly 20 years ago.