El Yunque Chronosequence Tree Census data

The El Yunque Chronosequence plots consist of four sites, El Verde 1 (EV1), Sabana 1 (SB1), Sabana 2 (SB2), and Sabana 3 (SB3), which are located at the edges of El Yunque National Forest at sites to the south of El Verde and Sabana Field Stations. The plots represent a range of successional stages representing areas in agriculture or recently abandoned in 1936 but reforested after 1950, and areas in agriculture or recently abandoned in 1977 and reforested since that time. They range in size from ~0.5 to 1 ha, vary in elevation from ~150m to 550m a.s.l. and span a wide range of ages and land use histories (Table 1). Plot Name Size Age Elevation EV1 10,000 m2 (1 ha) >62 yrs but < 76 yrs ~ 550m SB1 4,625 m2 (~0.5 ha) >62 yrs but not primary forest ~100-150m SB2 6,400 m2 (~0.6 ha) >35 yrs but < 62 yrs ~100-150m SB3 4,800 m2 (~0.5 ha) Primary forest ~100-150m One of these plots (EV1) is south of El Verde Field Station, on Forest Service land just over the property boundary.  This area was in agriculture in 1936 but appeared forested in a 1950 aerial photograph, and there are differences in forest structure and species composition consistent with the known differences in land use history. The other three Chronosequence sites are just south of the Sabana Field Station on Forest Service Land on the opposite side of the forest from El Verde. One plot (SB2) is located in young secondary forest in an area immediately adjacent to an old teak plantation forest. Another plot (SB1) is located in an area that was sparsely forested in 1936 and which appeared reforested in 1950. The third plot in Sabana (SB3) is located in a patch of primary “tabonuco†(named for the abundance of this tree species) forest on a steep slope on the west side of the Sabana River. 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.

埃尔云盖时间序列样地（El Yunque Chronosequence plots）共包含4个样点，分别为埃尔维德1号（El Verde 1, EV1）、萨瓦纳1号（Sabana 1, SB1）、萨瓦纳2号（Sabana 2, SB2）与萨瓦纳3号（Sabana 3, SB3）。所有样点均坐落于埃尔云盖国家森林公园（El Yunque National Forest）边缘，分别位于埃尔维德野外站（El Verde Field Station）与萨瓦纳野外站（Sabana Field Station）以南区域。
该系列样地涵盖多样的森林演替阶段，其土地利用历史包括1936年仍为农田或于当年新近撂荒、并于1950年后完成人工更新的区域，以及1977年仍为农田或于当年新近撂荒、并于此后逐步完成人工更新的区域。样地面积介于0.5至1公顷之间，海拔范围为150米至550米（a.s.l.），且覆盖跨度极大的林龄与土地利用历史序列（见表1）。
各单样地的详细参数如下：
EV1：面积10000平方米（1公顷），林龄62至76年，海拔约550米；
SB1：面积4625平方米（约0.5公顷），林龄62年以上，非原始林，海拔100至150米；
SB2：面积6400平方米（约0.6公顷），林龄35至62年，海拔100至150米；
SB3：面积4800平方米（约0.5公顷），为原始林，海拔100至150米。
其中EV1样地位于埃尔维德野外站南侧，地处跨越地界的美国林务局管辖林地内。该区域在1936年仍为农田，但在1950年的航空影像中已呈现森林覆盖状态；其森林结构与物种组成的差异，与已知的土地利用历史差异完全吻合。
其余3个时间序列样地均位于萨瓦纳野外站南侧，地处与埃尔维德野外站相对的森林另一侧的美国林务局管辖林地内。其中SB2样地位于一片幼年次生林内，紧邻一处老柚木人工林；SB1样地所在区域在1936年仅为稀疏林地，而在1950年的影像中已完成人工更新；萨瓦纳系列的第三个样地（SB3）位于萨瓦纳河西侧陡坡上的一片原始"tabonuco"林——该林分因该树种占比极高而得名。
本研究的资助来自美国国家科学基金会（National Science Foundation）拨付给波多黎各大学的多项课题经费，包括BSR-8811902、DEB-9411973、DEB-9705814、DEB-0080538、DEB-0218039、DEB-0620910、DEB-1239764、DEB-1546686与DEB-1831952，相关经费属于卢基约长期生态研究计划（Luquillo Long-Term Ecological Research Program）的一部分。额外资助由波多黎各大学以及美国农业部林务局热带林业国际研究所（International Institute of Tropical Forestry, USDA Forest Service）提供。