Spatial Analysis of Historical Fire Regimes and Landscape Structure in Sagebrush Ecosystems of the United States

重建历史火灾的证据很困难，因为需要在很大的空间范围内才能理解最近的大型野火，比如2007年在爱达荷州和内华达州的山艾树发生的65.2358英亩的墨菲综合体火灾，是史无前例的，还是在欧美广泛使用土地之前发生的。这一限制在覆盖美国西部约4700万公顷的山艾树生态系统中尤其成问题，因为历史火灾的树轮证据仅限于这些生态系统边缘的森林和林地。因此，人们对历史上的鼠尾草景观的结构或这些景观中历史野火的比率和模式知之甚少。怀俄明大学的威廉·贝克教授将利用19世纪末的土地办公室调查重建美国鼠尾草生态系统中历史上的火灾制度和景观结构。勘测员在布置剖面线时记录了野火和火灾早期演替后植被的位置。剖面线信息可以被计算机化，并转换成历史植被地图，以便对历史火灾和景观结构进行空间分析。这项研究将获取、处理和分析美国四个主要植物区系省份约2,223,900英亩的山艾树景观样本的调查记录，并利用这些记录重建历史火灾和景观结构。这项研究将解决关于鼠尾草历史火灾制度和景观结构的九个具体假说。这些假设集中在(1)历史火灾规模分布，(2)历史火灾的斑块，(3)历史火灾在景观中燃烧的频率，(4)历史景观的结构和大小，以及(5)历史火灾制度和景观结构的地理变化。鼠尾草是许多鼠尾草专属物种的唯一栖息地，其中一些物种正在衰落，或者已经被列为濒危物种，例如鼠尾草松鸡。鼠尾草也是主要的本土有蹄类动物种群的主要饲料，如鹿和麋鹿，在它们的冬季活动范围。这项研究将大大加强对一个关键的自然野火干扰的空间变化及其对代表西部主要生态系统的大型景观结构的历史影响的基本了解。有关历史野火的改进信息将有助于理解野火是否对物种减少有贡献，以及如何在关键的冬季范围内管理野火和山艾树。

Reconstructing evidence of historical fires is difficult at the large spatial extent required to understand whether recent large wildfires like the 652,358 acre Murphy Complex fires of 2007 in Idaho and Nevada sagebrush, are unprecedented or also occurred historically, prior to widespread EuroAmerican land uses. This limitation is particularly problematic in sagebrush ecosystems, which cover about 47 million ha of the western United States, as tree-ring evidence of historical fires is limited to forests and woodlands on the margin of these ecosystems. As a consequence, little is known about the structure of historical sagebrush landscapes or the rates and patterns of historical wildfires in these landscapes. Professor William Baker at the University of Wyoming will reconstruct historical fire regimes and landscape structure in sagebrush ecosystems in the United States using the General Land Office Surveys of the late 1800s. Surveyors recorded the location of wildfires and early-successional postfire vegetation as they laid out section lines. Section-line information can be computerized and converted into maps of historical vegetation to allow spatial analysis of historical fires and landscape structure. The study will acquire, process, and analyze survey records for sample sagebrush landscapes of about 2,223,900 acres in each of four major floristic provinces spanning the range of sagebrush in the United States, and use these records to reconstruct historical fires and landscape structure. The research will address nine specific hypotheses about historical fire regimes and landscape structure in sagebrush. These hypotheses center on (1) historical fire-size distributions, (2) the patchiness of historical fires, (3) the frequency at which fire historically burned across landscapes, (4) the structure and size of historical landscapes, and (5) geographical variation in historical fire regimes and landscape structure. Sagebrush is the sole habitat for a host of sagebrush-obligate species, some that are declining or are already listed as threatened or endangered, for example Sage Grouse. Sagebrush is also key forage for major populations of native ungulates, such as deer and elk, on their winter ranges. This study will substantially enhance basic understanding of spatial variation in a key natural wildfire disturbance and its historical influence on the structure of large landscapes representing a major western ecosystem. Improved information on historical wildfires will help understand if there is a wildfire contribution to declining species and how to manage wildfires and sagebrush on key winter ranges.