Landscape-scale maps of tree species densities are important tools for managing ecosystems threatened by forest pests. Eastern hemlock dominates riparian forests throughout its range. As a conifer in a deciduous landscape, hemlock plays an ecohydrological role, especially when other species are dormant. The nonnative, hemlock woolly adelgid has caused widespread hemlock decline and mortality. We used two existing basal area raster layers first to identify Chesapeake Bay subwatersheds with ≥6 percent hemlock basal area and second to quantify hemlock basal area densities within fixed-width riparian buffers of 50 m, 100 m, 250 m, and 500 m. Hemlock densities were higher in riparian zones compared with entire subwatersheds. In five subwatersheds, 50 m and 100 m zones had higher percentages of pixels with ≥25 percent hemlock basal area. We produced maps identifying hemlock riparian densities in the Pine Creek Watershed, which managers can use to prioritize sites for supplemental conifer planting under anticipated hemlock decline.

中文翻译：

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受铁杉羊毛 Adelgid 威胁的切萨皮克湾河岸铁杉林的空间分布

树种密度的景观尺度图是管理受森林害虫威胁的生态系统的重要工具。东部铁杉在其整个范围内占主导地位的河岸森林。作为落叶景观中的针叶树，铁杉发挥着生态水文作用，尤其是在其他物种处于休眠状态时。非本地的铁杉羊毛 adelgid 导致了广泛的铁杉衰退和死亡率。我们首先使用两个现有的基底区域栅格图层来识别具有 ≥ 6% 铁杉基底面积的切萨皮克湾亚流域，然后在 50 m、100 m、250 m 和 500 m 的固定宽度河岸缓冲区内量化铁杉基底面积密度。与整个子流域相比，河岸带的铁杉密度更高。在 5 个子流域中，50 m 和 100 m 区域的铁杉基底面积≥25% 的像素百分比较高。