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.

永久样地数据应呈现如下时间动态模式：(1) 植被盖度与树木茎干密度快速提升；(2) 植物群落从早期演替物种向晚期演替物种发生快速更替。植物间竞争强度应快速增强，此时本土草本植物与外来物种将成为优势竞争者，这或会导致部分在滑坡扰动后常见的树木被排挤。在牛群移除后的前五年内，受扩散限制作用，鸟类传播的入侵树木物种会呈现集群分布，其空间分布模式应包含边缘效应。由于牧场土壤完整且植被覆盖度较低，树木的生长——以生物量（生产力）、株高与基径的增长为衡量指标——应显著快于滑坡生境中的树木定植过程。本研究得到美国国家科学基金会（National Science Foundation）拨付的多项资助（BSR-8811902、DEB-9411973、DEB-9705814、DEB-0080538、DEB-0218039、DEB-0620910、DEB-1239764、DEB-1546686及DEB-1831952），由波多黎各大学作为卢奎略长期生态研究计划（Luquillo Long-Term Ecological Research Program）的一部分承接。此外，本研究还得到波多黎各大学与美国农业部林业局国际热带森林研究所的支持。