Data for: Abundance of invasive grasses is dependent on fire regime and climatic conditions in tropical savannas

Data associated with the homonymous manuscript published in Journal of Environmental Management.

ABSTRACT
Invasive grasses are a threat to some tropical savannas, but despite being fire-prone ecosystems, little is known about the relationships between the fire season. The climatic conditions and the invasive species on these systems. We evaluated the response of the perennial invasive grasses Melinis minutiflora and Urochloa brizantha to three fire seasons in an open tropical savanna in South America: Early-Dry (May), Mid-Dry (July) and Late-Dry (October). Moreover, we investigated how these responses were influenced by precipitation and extreme air temperatures. We hypothesized that biomass of both species would be reduced by fires during their reproductive period and that climatic conditions would affect them equally. We conducted prescribed burns on 15 x 15 m plots (4 plots x 4 treatment x 2 invasive species = 32 plots) in 2014. We sampled the biomass before the burn experiments and for the next two years (five 0.25 m2 samples/plot). Our experiments revealed that the fire season did not influence the abundance of either species. However, the two species responded differently to fire occurrence: M. minutiflora decreased whereas U. brizantha was not affected by fires. Early-Dry and Late-Dry fire treatments enhanced the replacement of M. minutiflora by U. brizantha. We found that the influence of precipitation depended on the species: it reduced M. minutiflora but increased U. brizantha abundance. Lower monthly minimum temperatures decreased the abundance of both species. It directly reduced live M. minutiflora and increased dead U. brizantha biomass. Monthly maximum temperatures affected the invasive grasses by reducing live M. minutiflora. Since tropical savannas are predicted to face climatic instability and that climate influences the differential response of invasive species, the management of invaders should consider both the identity of the target species and the possible interactions with other invasive species. Moreover, it is essential to keep an adaptive management approach to face the uncertainties that climate change may pose to biodiversity conservation.

本数据集关联发表于《Journal of Environmental Management》（环境管理期刊）的同名研究论文。

摘要：入侵草本植物对部分热带稀树草原构成生态威胁。尽管该类生态系统属于火灾频发的生态系统，但目前学界对火灾季节、气候条件与该生态系统中入侵物种之间的关联机制仍缺乏深入了解。本研究以南美洲一处开阔型热带稀树草原为研究区域，评估了多年生入侵草本毛颖草（Melinis minutiflora）和布氏臂形草（Urochloa brizantha）对三个不同火灾季节的响应：旱季早期（5月）、旱季中期（7月）与旱季晚期（10月）。此外，本研究还探讨了降水与极端气温如何调控这两种入侵草本的响应特征。我们提出两项研究假说：其一，两种入侵草本的生物量均会在其生殖期遭遇火烧后显著降低；其二，气候条件对二者的影响程度相当。本研究于2014年在15 m × 15 m的样地中开展控制性火烧实验（4个重复样地 × 4种处理 × 2种入侵植物 = 共计32个样地），分别在火烧实验开展前以及后续两年内进行生物量采样（每个样地采集5个0.25 m²的样本）。实验结果显示，火灾季节并未对两种入侵草本的种群丰度产生显著影响。但两种草本对火烧事件的响应存在显著分化：毛颖草的生物量显著下降，而布氏臂形草的种群丰度未受火烧影响。旱季早期与晚期的火烧处理加剧了布氏臂形草对毛颖草的替代效应。研究发现，降水对两种入侵草本的影响因物种而异：降水抑制了毛颖草的种群丰度，却提升了布氏臂形草的种群数量；月度最低气温降低会导致两种草本的丰度均出现下降，其直接作用表现为减少活毛颖草生物量，并增加枯死的布氏臂形草生物量；月度最高气温升高则通过降低活毛颖草生物量对入侵草本产生负面影响。鉴于热带稀树草原预计将面临气候不稳定问题，且气候会影响入侵物种的差异化响应，因此入侵物种管理应同时考虑目标物种的特性，以及与其他入侵物种间的潜在相互作用。此外，采用适应性管理策略以应对气候变化对生物多样性保护带来的不确定性，亦是十分必要的。