Data from: Burning for enhanced non-timber forest product yield may jeopardize the resource base through interactive effects

1. Non-timber forest product (NTFP) harvest is frequently accompanied by resource management practices that interact with the harvesting itself, other disturbances and abiotic conditions. These interactions, in turn, lead to diverse environmental effects. Few studies focus on these practices in the context of harvesting NTFPs, product properties and environmental impacts, including biological invasions.

2. In Pine woodlands in Eastern Bhutan, Cymbopogon flexuosus East Indian Lemon Grass is harvested and distilled to obtain essential oil, an economically important NTFP. Prescribed fires are applied in late winter (before annual harvest in summer) to induce regeneration of new tillers with increased essential oil content. This practice is based on local ecological knowledge and renders the utilization of C. flexuosus economically viable. On two sites with contrasting stand structure, we evaluated the effects of different prescribed burning regimes (no burning vs. burning with two levels of frequency and intensity) on the sustainability of annually harvested C. flexuosus, regarding cover, biomass yield, essential oil yield and quality. At the same time, we evaluated the effects of prescribed burning on the spread of the invasive shrub Chromolaena odorata.

3. Cymbopogon flexuosus biomass declined over time, likely as a result of harvesting. In more closed stands it was moreover marginally negatively influenced by fire. We confirmed local ecological knowledge regarding significantly higher essential oil yield on burned plots, without differences between fire regimes.

4. In open stands, fire led to rapid expansion of C. odorata, specifically with frequently applied, higher intensity fires. Additionally, the spread of C. odorata showed adverse effects on C. flexuosus cover.

5. Synthesis and applications. Our results highlight the importance of studying the wider impacts of non-timber forest product (NTFP) harvest. We confirmed local ecological knowledge that fire increases lemon grass essential oil yield, making prescribed burning an attractive land management tool for farmers. Nevertheless, the practice of annual harvesting may lead to resource decline that may be exacerbated by fire in closed stands. Caution needs to be practiced on open sites where invasive C. odorata may spread rapidly after fires. Management needs to focus on preventing concentration of annual harvesting and associated prescribed burning in the same areas. Amending national forestry rules to legalize fire as a land management tool can support local economies and potentially prevent wildfires that regularly devastate human infrastructure across eastern Bhutan.

1. 非木材林产品（Non-timber forest product, NTFP）的采收活动往往伴随一系列与之相互作用的资源管理措施，这些措施同时还会与采收行为本身、其他干扰因子及非生物环境条件产生联动，进而引发多样的环境效应。目前鲜有研究聚焦于非木材林产品采收、产品特性与环境影响（涵盖生物入侵）背景下的这类管理实践。
2. 在不丹东部的松林生态系统中，人们采收香茅（Cymbopogon flexuosus，东印度柠檬草）并经蒸馏获取精油——这是一类极具经济价值的非木材林产品。当地通常在每年夏季采收前的晚冬时节实施计划火烧，以诱导新分蘖生成并提升精油含量。该实践基于本土生态知识，让香茅的开发利用具备了经济可行性。本研究选取两个林分结构存在显著差异的样地，评估了不同计划火烧制度（无火烧、两种频率与强度梯度的火烧）对年度采收香茅的可持续性的影响，评估指标包括盖度、生物量产量、精油产量与品质；同时探讨了计划火烧对入侵灌木紫茎泽兰（Chromolaena odorata）扩散的影响。
3. 随时间推移，香茅的生物量呈下降趋势，这大概率源于持续采收的影响；在林分更为郁闭的样地中，火烧还会对其产生微弱的负面影响。本研究验证了本土生态知识：火烧样地的精油产量显著更高，但不同火烧制度间并无显著差异。
4. 在林分开阔的样地中，火烧会加速紫茎泽兰的扩散，尤其是在高频率、高强度火烧处理下。此外，紫茎泽兰的扩散会对香茅的盖度产生不利影响。
5. 总结与应用。本研究结果凸显了开展非木材林产品采收全链条影响研究的重要性。我们验证了本土生态知识：火烧可提升柠檬草精油产量，这使得计划火烧成为极具吸引力的农户土地管理工具。然而，年度采收行为可能导致资源衰减，而在郁闭林分中火烧会进一步加剧这一问题。在开阔样地需格外谨慎，因为火烧后入侵物种紫茎泽兰可能快速扩散。管理实践需避免在同一区域同时开展年度采收与配套的计划火烧。修订国家林业法规，将火烧合法化作为土地管理手段，可助力地方经济发展，同时有望遏制长期以来摧毁不丹东部多地人居设施的野火频发问题。