Demography of scrub plum (Prunus geniculata) at Carter Creek, Lake Wales Ridge National Wildlife Refuge, 2001-2013, in relation to fire and felling

At the Carter Creek unit of the Lake Wales Ridge National Wildlife Refuge, we collected demographic data annually on scrub plum (Prunus geniculata), a federally endangered shrub. We initially selected 903 plants (tagged and GPS'd) distributed among 12 management units in February 2001, a minimum of 65 plants per management unit. We worked with United States Fish and Wildlife Service (USFWS) staff and a crew from The Nature Conservancy (TNC) to impose three management treatments on a unit basis (4 replicate units) in 2001 (finishing in August): control, chain-saw felling of large oaks, and chain-saw felling followed by prescribed burns. The treatments also served as the basis for vegetation sampling and demographic research on other species (Rickey et al. 2013). Beginning in 2001 and continuing through 2008, we collected annual data (in February) on each marked plant, including survival status, life history stage, height, maximum crown diameter, and reproductive structures. We also scoured areas near plants for new seedlings. We subsampled plants from 2009-2012, and then re-censused all plants in 2013. We also noted fire severity in 2001, 2007, and 2009 in four categories for each plant. Analyses through 2007 (Menges and Weekley 2013) showed that scrub plum had extremely high annual survival (98%) but minimal seedling recruitment. Scrub plum had high survival in all four burn treatments, although severely burned plants were more likely to die. Fire benefited scrub plum as plants resprouted vigorously, increased stem numbers post-fire, and had higher flower production 2-3 years after fires. Between fires, plants increased in height and diameter but retained fewer stems. We concluded that chainsaw felling of oaks did not have strong effects on scrub plum and could be a useful management tool, but we also emphasized the primacy of fire as an ecological disturbance and management treatment in this sandhill ecosystem.本数据集采集自沃兹湖脊国家野生动物保护区（Lake Wales Ridge National Wildlife Refuge）卡特溪管护单元，针对联邦濒危灌木灌丛李（*Prunus geniculata*）开展年度种群动态监测。研究团队于2001年2月完成初始植株选定工作，共标记并通过全球定位系统（GPS）定位903株个体，这些植株分布于12个管护单元中，每个管护单元至少包含65株植株。本研究与美国鱼类及野生动物管理局（United States Fish and Wildlife Service, USFWS）工作人员以及自然保护协会（The Nature Conservancy, TNC）的野外团队合作，于2001年（全部作业于当年8月完成）在管护单元尺度下设置3种管控处理，每种处理设置4个重复单元：对照组、大型栎树链锯砍伐组，以及链锯砍伐后开展计划火烧组。上述处理同时为其他物种的植被采样与种群生态学研究提供了实验基础（Rickey等，2013）。2001年至2008年期间，研究团队于每年2月对每株标记植株开展年度数据采集，记录内容包括存活状态、生活史阶段、株高、冠幅最大直径以及生殖结构。同时，团队会对植株周边区域进行巡查以记录新萌发的实生苗。2009年至2012年期间，研究团队仅对部分植株进行抽样监测，并于2013年对全部植株开展全面普查。此外，研究人员针对2001年、2007年及2009年的火烧烈度，为每株植株划分了4个等级。截至2007年的分析结果（Menges与Weekley，2013）显示，灌丛李的年存活率极高（达98%），但实生苗补充率极低。尽管受严重火烧的植株死亡率更高，但所有火烧处理组内的灌丛李存活率均维持在较高水平。火烧可使灌丛李通过萌蘖实现旺盛的营养繁殖，火烧后茎秆数量显著增加，且在火烧后2至3年的开花量更高，因此对灌丛李具有正向效益。在两次火烧间隔期内，灌丛李的株高与冠幅会持续增长，但茎秆数量会有所减少。研究结论表明，对栎树实施链锯砍伐对灌丛李未产生显著影响，该手段可作为一项有效的管护工具；但研究同时强调，在该沙丘丘陵生态系统中，火烧作为生态干扰与管控措施仍处于核心地位。