Sabana pasture permanent plot vegetation sampling

Permanent plot data is expected to show these temporal patterns: (1) rapid increases in percent cover and tree stem density, and (2) rapid turnover from early to late successional plant species. Plant-plant competition should show quick increases in intensity with native grass species and exotic as top competitors. These may lead to exclusion of some trees common after landslide disturbance. Spatial patterns of invading trees should include edge effects due to dispersal limitation with clumping of bird-dispersed species before the first five years after cow exclusion. Because of intact soil and low vegetation in the pasture trees should grow, as measured by biomass(productivity), height, and basal diameter increases, significantly faster compared to colonization of landslides. Support for this work was provided by grants BSR-8811902, DEB-9411973, DEB-9705814 , DEB-0080538, DEB-0218039 , DEB-0620910 , DEB-1239764, DEB-1546686, and DEB-1831952 from the National Science Foundation to the University of Puerto Rico as part of the Luquillo Long-Term Ecological Research Program. Additional support provided by the University of Puerto Rico and the International Institute of Tropical Forestry, USDA Forest Service.

永久样地（permanent plot）数据预计将呈现以下时间动态模式：(1) 盖度百分比（percent cover）与树木茎干密度快速上升；(2) 植物群落从早期演替物种向晚期演替物种快速更替。植物种间竞争强度将随本土草本植物与外来物种成为优势竞争者而迅速升高，这一过程可能导致部分在滑坡扰动后常见的树木被排挤。入侵树木的空间分布格局将呈现边缘效应，该效应源于扩散限制（dispersal limitation）；且在禁牧（cow exclusion）后的前五年内，鸟类传播物种（bird-dispersed species）会呈现集群分布。由于牧场生境土壤完整且植被覆盖率较低，牧场中树木的生长情况（通过生物量（productivity）、树高与基径（basal diameter）的增长衡量）将显著快于滑坡生境中的定居树木。本研究得到了美国国家科学基金会（National Science Foundation）拨付给波多黎各大学的多项拨款资助，包括BSR-8811902、DEB-9411973、DEB-9705814、DEB-0080538、DEB-0218039、DEB-0620910、DEB-1239764、DEB-1546686以及DEB-1831952，相关工作属于卢奎略长期生态研究计划（Luquillo Long-Term Ecological Research Program）的一部分。此外，本研究还得到了波多黎各大学与美国农业部林务局（USDA Forest Service）下属国际热带森林研究所（International Institute of Tropical Forestry）的支持。