Kirtland's warbler occupancy and plantation density

Early studies into the habitat preferences of the Kirtland’s warbler (KW; Setophaga kirtlandii) suggested that these birds exhibited a preference for areas with high jack pine stem densities; therefore, jack pine plantations established as part of the KW recovery and conservation programs have been planted using a 1.5 x 1.8 m spacing (3,588 trees ha-1). In contrast, traditional pine plantations in the Lake States established for roundwood production are typically planted on a 2.1 x 2.4 m spacing that equates to 1,922 trees ha-1. Over more than 40 years, tree spacing in KW habitat plantations has gone largely unchanged, and until very recently there has never been an attempt to verify that these tighter spacings actually provide better KW habitat than would a traditional forestry spacing. We used a retrospective approach to assess the impacts of tree density on KW occupancy and observed an unexpected negative relationship between realized plantation density and maximum occupancy by KW si..., We took advantage of unintended variability in plantation spacing to conduct a retrospective assessment of KW usage of plantations across a range of realized plantation densities. Our approach was to use MDNR regeneration survey data to determine realized plantation density and then to relate this to KW occupancy using KW census data. We used digital 3-year post-planting surveys from 2004 - 2010. The maximum density of KW (males ha-1) was used as the metric for analyses and was calculated for each stand by taking the number of singing males from the peak year of occupancy and dividing that by the size (ha) of the stand. In addition to jack pine stem density, we attempted to account for other factors known to influence local KW density, including stand age, stand size, geographic location, and the amount of occupiable habitat in the surrounding landscape. Therefore, for each stand in our analysis we also considered the following as covariates: stand size (ha), functional unit size (ha), ..., , # Kirtland's warbler occupancy and plantation density This dataset has Kirtland's warbler census data for dedicated jack pine plantations on Michigan DNR forest land in relation to the realized stem density of those plantations ## Description of the data and file structure Functional Unit: We defined functional unit as a group of adjacent KW stands that were within 8 years of age of each other, representing available KW habitat on a broader scope than a single stand. This parameter identifies which functional unit each stand belongs to. Functional_Unit_Ha: This parameter defines the area in hectares of each functional unit FCS-Key: This represents the unique MDNR stand identifier number. Stand_Origin_Year: This represents the year in which the plantation was established Age: Age of the stand in 2022 Stand_Hectares: Area of the stand in hectares KWMU_Mgmt_Block: KW Management Unit represents which one of 16 unique areas on MDNR land designated for KW management and is a proxy ...早期关于科克伯氏林莺（Kirtland’s warbler, KW；Setophaga kirtlandii）栖息地偏好的研究表明，该类鸟类偏好短叶松（jack pine）茎密度较高的生境。因此，作为KW恢复与保护计划组成部分营造的短叶松人工林，采用了1.5×1.8米的株行距（每公顷3588株）。与之相对，五大湖地区传统的圆材生产用松树人工林，通常采用2.1×2.4米的株行距，即每公顷1922株。四十余年来，KW生境人工林的株行距基本未作调整，且直至近期，从未有研究验证过这种更密的株行距确实比传统林业株行距能提供更优质的KW生境。我们采用回顾性研究方法评估了树木密度对KW栖息占用的影响，观测到人工林实际密度与KW最大栖息占用率之间存在出乎意料的负相关关系……我们利用人工林株行距的意外差异，对不同实际密度人工林的KW利用情况开展了回顾性评估。我们的研究方法为：借助密歇根州自然资源部（Michigan Department of Natural Resources, MDNR）的更新调查数据确定人工林的实际密度，随后结合KW普查数据，将其与KW栖息占用情况建立关联。我们使用了2004至2010年的造林后3年数字调查数据。本研究以每公顷雄性KW个体数作为分析指标，通过计算各林分在栖息占用峰值年份的鸣唱雄性个体数除以林分面积（公顷）得到该指标。除短叶松茎密度外，我们还尝试纳入其他已知影响局域KW种群密度的因素，包括林分年龄、林分面积、地理位置，以及周边景观中可栖息生境的占比。因此，本分析中的每个林分，我们均纳入以下协变量：林分面积（公顷）、功能单元面积（公顷）…… # 科克伯氏林莺栖息占用与人工林密度 本数据集包含密歇根州自然资源部（MDNR）管辖林地内专属短叶松人工林的科克伯氏林莺普查数据，与这些人工林的实际茎密度相关联。 ## 数据与文件结构说明 功能单元（Functional Unit）：我们将功能单元定义为一组相邻的KW林分，且彼此林龄差距不超过8年，代表比单个林分更宏观尺度的可用KW生境。该参数用于标识每个林分所属的功能单元。 功能单元面积（Functional_Unit_Ha）：该参数定义了每个功能单元的面积，单位为公顷。 FCS标识号（FCS-Key）：即密歇根州自然资源部（MDNR）唯一的林分识别编号。 林分营造年份（Stand_Origin_Year）：该人工林的营造年份。 林分年龄（Age）：截至2022年的林分年龄。 林分面积（Stand_Hectares）：林分的面积，单位为公顷。 KW管理单元（KWMU_Mgmt_Block）：KW管理单元指密歇根州自然资源部（MDNR）土地上为KW管理划定的16个独特区域之一，可作为……的替代指标。