Data for: Sierra Nevada mixed-conifer regeneration response to repeated burning varies by species

Fire-exclusion has acted as a major perturbation on dry conifer forests in the western U.S., increasing tree density and, in mixed-conifer forests, the dominance of shade-tolerant species. Restoration efforts aim to reverse these effects by reducing stand density, restoring relative proportions of tree species, and reintroducing recurrent fire, but there are limited long-term data on the effects of repeated burning on tree regeneration. We analyzed two decades of seedling and overstory data from the Teakettle Experimental Forest in the southern Sierra Nevada, California, USA to determine how thinning and repeated burning affect seedling establishment and overstory recruitment. The treatments included three levels of thinning (no thin, understory thin, overstory thin) crossed with two levels of burning (burn, no burn). Treatments were replicated three times in 4 ha treatment units. Seedlings were surveyed at gridpoints within the treatment units for the pre-treatment period (1999-2000), ..., These data were collected using a gridded treatment unit system where seedling data within treatments were collected using circular plots. Thinning treatments were implemented in 2000 and 2001 and the original burn treatment in 2001. The second-entry burn was implemented in 2017.,

林火抑制措施已成为美国西部干旱针叶林的主要干扰因子，会提升林分密度，在混交针叶林中还会增加耐荫树种的优势度。森林恢复工作旨在通过降低林分密度、恢复树种相对占比、重新引入周期性林火来逆转上述效应，但目前关于重复火烧对树木更新影响的长期数据仍较为匮乏。本研究基于美国加利福尼亚州内华达山脉南部茶壶试验林（Teakettle Experimental Forest）长达二十年的幼苗与林上层植被监测数据开展分析，以明确疏伐与重复火烧如何影响幼苗定植与林上层植被更新补充。试验设置了3个疏伐梯度（无疏伐、林下疏伐、上层疏伐）与2个火烧梯度（火烧、未火烧）的交叉处理方案，每种处理在4公顷的试验单元中重复3次。研究人员于预处理阶段（1999-2000年）在试验单元内的网格点开展幼苗调查，……本研究采用网格化试验单元系统进行数据采集，处理组内的幼苗数据通过圆形样方收集。疏伐处理于2000至2001年间实施，首次火烧处理于2001年开展，第二次火烧处理则于2017年实施。