Northern Grasshopper Mouse Predicted Habitat - CWHR M121 [ds2575]

CWHR Predicted Habitat Models represent areas of predicted suitable habitat for each species within its range. These models are built from the following principal inputs: 1) a statewide, best-available vegetation map (FVEG); 2) GIS data representing a species’ range; 3) the CWHR database of habitat suitability values for over 700 terrestrial vertebrate species. Habitat suitability ranks of Low (non-zero values less than 0.34), Medium (0.34-0.66), and High (greater than 0.66) are based on the maximum suitability value across the 3 species life requisites: reproduction, feeding, and cover. Note that previous versions of these Predicted Habitat Models used an average across the 3 life requisites in order to obtain an overall suitability score for each habitat type and stage class. Habitat suitability scores were developed based on habitat patch sizes greater than 40 acres in size and are best interpreted for habitat patches greater than 200 acres in size. The FVEG landcover dataset is an aggregation of multiple statewide landcover and regional vegetation mapping efforts, conducted at different points in time (approximately 1990 up to time of publishing) and at various resolutions, compiled by the California Department of Forestry and Fire Protection (CALFIRE). FVEG uses the most current and consistent data available for each region of the state. Decision rules were developed that controlled which layers were given priority in areas of overlap. Crosswalks were used to attribute the various data sources according to the CWHR habitat-type classification system. Attributing FVEG with CWHR habitat types allows for the extraction of areas with non-zero suitability values for each species within the bounds of its range, creating a series of maps of predicted suitable habitat which are species-specific. Because FVEG is an amalgam of disparate landcover assessment efforts across the state, the predictive power for determining suitable habitat will vary between species, and possibly even regionally for species which are widely distributed. While these maps represent CDFW’s best estimate of the presence of suitable habitat for any given species in the CWHR system, these maps are also limited by several factors: 1) the accuracy and resolution of vegetation maps in a given region; 2) the dynamic nature of the landscape in which fire and other disturbance events alter conditions at a greater frequency than mapping efforts can track; 3) the currency of expert knowledge, particularly as species adapt to changing land and climate conditions and the shifting of other species’ ranges; 4) the frequency of species-specific surveys across a representative sample of a species’ entire range; 5) metapopulation dynamics, which describes the shifting of populations within their environment as result of numerous types of interactions and responses. CWHR GIS data representing predicted suitable habitat should not be used to indicate the presence or absence of a particular species at any specific site. CWHR predicted habitat models are named according to the 4-character alpha-numeric CWHR ID assigned to each species (5 characters in the case of subspecies or other sub-taxa). There is also a “CWHR Revision Tracking Table” containing a record for each species, its CWHR ID, scientific name, common name, and range and habitat model data revision history. CWHR species range models, predicted habitat models, and GIS data of the statewide distribution of all CWHR habitat types, along with the CWHR revision tracking table, are available for download at https://www.wildlife.ca.gov/Data/CWHR.CWHR预测生境模型（CWHR Predicted Habitat Models）指在各物种种群分布范围内，预测其适宜生境分布区域的模型。此类模型基于以下三类核心输入构建：1）全州范围内可获取的最优植被地图（FVEG）；2）表征物种种群分布范围的地理信息系统（Geographic Information System, GIS）数据；3）涵盖700余种陆生脊椎动物生境适宜性分值的CWHR数据库。 生境适宜性等级划分为低（非零分值小于0.34）、中（0.34至0.66）、高（大于0.66），该分级依据物种繁殖、觅食与隐蔽这三类生存必需条件的最大适宜性分值确定。需注意，此前版本的预测生境模型采用三类生存必需条件的平均分值，以获取每类生境类型与阶段类别的整体适宜性评分。 生境适宜性分值的生成基于面积大于40英亩的生境斑块，其最优解读场景为面积大于200英亩的生境斑块。 FVEG土地覆盖数据集是多项全州土地覆盖与区域植被测绘工作的整合成果，这些测绘工作于不同时段（大致为1990年至发布当日）开展，分辨率各异，由加州林业与消防局（California Department of Forestry and Fire Protection, CALFIRE）编制。FVEG采用加州各区域当前可获取的最新且一致的数据，并制定了决策规则以处理重叠区域中图层的优先级问题。同时通过跨映射对照表（Crosswalks），依据CWHR生境类型分类系统为各类数据源赋予属性。 将FVEG数据集与CWHR生境类型进行属性关联后，即可提取各物种种群分布范围内具有非零适宜性分值的区域，进而生成一系列物种种群专属的预测适宜生境地图。由于FVEG是全州范围内多项不同土地覆盖评估工作的整合产物，其判定适宜生境的预测能力会因物种而异，对于分布范围广泛的物种，甚至可能因区域不同而存在差异。 尽管此类地图代表了加州鱼类与野生动物部（California Department of Fish and Wildlife, CDFW）对CWHR体系中任意物种种群适宜生境存在情况的最优估算，但仍受多项因素限制：1）特定区域内植被地图的精度与分辨率；2）景观的动态特性——火灾与其他干扰事件改变生境条件的频率高于测绘工作的更新频率；3）专家知识的时效性，尤其是在物种适应土地与气候条件变化、其他物种种群分布范围发生转移的背景下；4）针对物种种群完整分布范围的代表性样本开展物种专属调查的频次；5）集合种群动态——即各类交互作用与响应导致种群在其生存环境中发生转移的现象。 CWHR预测生境模型不得用于判定任意特定地点是否存在某一物种。 CWHR预测生境模型按照为每个物种分配的4位字母数字组合CWHR ID命名（亚种或其他亚分类单元的物种则使用5位ID）。此外还有一份“CWHR修订追踪表”，其中包含每个物种的相关记录，包括其CWHR ID、学名、通用名、种群分布范围与生境模型数据的修订历史。 CWHR物种种群分布模型、预测生境模型、涵盖全州所有CWHR生境类型分布的GIS数据，以及CWHR修订追踪表，均可从https://www.wildlife.ca.gov/Data/CWHR 下载获取。