Permanent Plot Vegetation Sampling, 2003 Shrub and Vine Data BES ID 414-

Permanent plots are a powerful tool for understanding systems over the long term because of the rigorous quantification of patterns in a spatially refined way and because of the comparability of numerous variables measured in the same place. In 1998, 7 plots were surveyed into 3 forests in the study region of the Baltimore Ecosystem Study (BES): Oregon Ridge Park (4 plots), Hillsdale Park (1 plot), and Leakin Park (2 plots). In 2003, the same seven plots were re-surveyed and one in Hillsdale Park was added, for a total of eight plots. Plots were surveyed in order to correct for slope and to achieve an accuracy of plot side length to within 0.5 cm. Plots are 1600 m2 with the exception of the Hillsdale plots which are 900 m2. The Hillsdale plots are smaller to fit within the confines of the forest patch. Sites were selected 1) to represent urban and non-urban forests, 2) away from obvious habitat boundaries or edges, 3) with consistent drainage lines within the plot, and 4) with at least 80 % continuous tree canopy. All vegetation layers were sampled in order to characterize the structure and composition of the plant community. A variety of sampling methods were used for the different layers but all layers were quantified with a high level of detail to minimize variation and to best characterize the plot.

永久样地是长期解析生态系统动态的有力工具，其核心优势在于能够以空间精细化的方式对生态格局开展严格量化，同时可对同一监测点位测得的多类变量进行跨时空对比。1998年，在巴尔的摩生态研究计划（Baltimore Ecosystem Study, BES）的研究区域内，针对3片森林布设并完成了7个样地的调查：俄勒冈岭公园（4个样地）、希尔斯代尔公园（1个样地）与利金公园（2个样地）。2003年，研究团队对原有7个样地进行了重测，并新增希尔斯代尔公园内的1个样地，样地总数增至8个。开展本次调查的目的在于校正坡度影响，并将样地边长的测量精度控制在0.5 cm以内。除希尔斯代尔公园的样地面积为900 m²外，其余样地面积均为1600 m²。希尔斯代尔公园的样地采用较小面积，以适配该森林斑块的空间边界。样地选址遵循四项核心原则：1）能够代表城市与非城市森林类型；2）远离明显的生境边界或边缘区域；3）样地内部排水条件保持一致；4）林木冠层连续度不低于80%。为全面表征植物群落的结构与组成，研究团队对所有植被层位开展了采样工作。针对不同植被层位采用了多样的采样方法，但所有层位均以高细节度完成量化，以尽可能降低采样变异，实现对样地的最优表征。