Vegetation - Permanent Plots - Ground Vegetation

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). Plots were surveyed in 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 plot which is 900 m2. The Hillsdale plot is 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.

长期样地是解析长期生态系统动态的有力工具，其核心优势在于可通过空间精细化方式对生态格局开展严谨量化，并能对同一地点测定的多项变量进行跨时间对比。1998年，研究团队在巴尔的摩生态系统研究（Baltimore Ecosystem Study, BES）的区域内，于3片森林中共布设7个样地：俄勒冈岭公园（4个样地）、希尔斯代尔公园（1个样地）以及利金公园（2个样地）。样地布设过程中校正了坡度影响，并将样地边长的测量精度控制在0.5 cm以内。除希尔斯代尔样地外，其余样地面积均为1600 m²；希尔斯代尔样地因需适配所在林块的范围，面积调整为900 m²。样地选址遵循四项标准：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林缘；3）样地内部排水条件均一；4）林木连续盖度不低于80%。为全面表征植物群落的结构与组成，研究对所有植被层开展了系统采样。针对不同植被层采用了多样化的采样方案，但所有层位均以高精度细节进行量化，以尽可能降低采样误差，精准刻画样地的植被特征。