Fire threatens the diversity and structure of tropical gallery forests
Fire threatens the diversity and structure of tropical gallery forests
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DOI：
10.1002/ecs2.3347
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发表时间：
2021-01-01
期刊：
影响因子：
2.7
通讯作者：
Retana, Javier
中科院分区：
文献类型：
--
作者：
Armenteras, Dolors;Meza, Maria Constanza;Retana, Javier
画廊森林在大多数热带稀树草原景观中广泛存在，形成了以草为主的系统、树木和森林斑块的马赛克。水、养分供应和野火之间的相互作用影响了这些景观系统的结构、模式和过程，并塑造了哥伦比亚和委内瑞拉奥里诺科盆地稀树草原-森林过渡区当今的生物多样性。然而，这些地区的稀树草原火灾变得更大、更频繁。为了调查火灾对廊道森林的影响，我们在三种不同的火灾暴露范围内建立了 18 个 0.1 公顷的森林地块：（1）沿边缘（距离边缘 100 m）受火灾影响的森林，以及（3）没有火灾证据（未燃烧）。我们通过分析最丰富树种的成分和结构变化并量化与火灾相关的功能特征，确定了植被对火灾的反应（通过自然更新）。我们调查了128种，对应35科77属。未烧毁的森林中的树高超过 10.70 m (+/- 2.72)。烧毁边缘的死树数量 (21.76% +/- 24.3) 几乎是烧毁内部的两倍 (13.08% +/- 15.73)。未烧毁森林的地上生物量（AGB）（176.9 毫克/公顷）是内部烧毁森林（74.4 毫克/公顷）的两倍多，是边缘烧毁地点的地上生物量（41.3 毫克/公顷）的四倍多。在最丰富的物种中，62% 被归类为对火灾敏感的物种，14% 是火灾幸存者，24% 能够抵抗火灾，并且大多存在于多样性较低的群落中。尽管耐火物种通常具有较厚的树皮、较高的木材密度和较高的叶片干物质含量，但没有明确的火灾反应模式仅与功能性状相关。因此，整体火灾导致了强烈的成分变化，耐火物种增多，这些物种在受干扰的地区生长并鼓励草丛生长，导致稀树草原侵入廊道森林。应监测长期后果。
Gallery forests are widespread in most tropical savanna landscapes creating a mosaic of grass-dominated systems with tree components and forest patches. Interactions among water, nutrient availability, and wildfires have influenced the structure, patterns, and processes of these landscape systems and have shaped today's biodiversity in the savanna-forest transitions of the Orinoco basin in Colombia and Venezuela. However, savanna fires have become larger and more frequent in these areas. In order to investigate the impacts of fire on gallery forests, we established 18 forest plots of 0.1 ha within three different fire exposures: (1) fire affected forests along the edge (100 m from the edge), and (3) no evidence of fire (unburned). We identified responses of the vegetation to fire (through natural regeneration) by analyzing the compositional and structural changes and quantifying fire-related functional traits for the most abundant tree species. We surveyed 128 species, corresponding to 77 genera and 35 families. Tree height is over 10.70 m (+/- 2.72) in unburnt forests. Dead tree presence in burnt edges (21.76% +/- 24.3) almost doubles that of burnt interior (13.08% +/- 15.73). The aboveground biomass (AGB) of unburnt forests (176.9 Mg/ha) was more than double that of the interior burnt forests (74.4 Mg/ha) and four times higher that AGB in the edge burnt sites (41.3 Mg/ha). Of the most abundant species, 62% were classified as fire-sensitive species, 14% were fire survivors and 24% were resistant to fires and mostly present in communities with lower diversity. Although fire-tolerant species in general presented thicker barks, higher wood densities, and higher leaf dry matter content, no clear pattern of fire response was associated only with functional traits. Thus, overall fire is resulting in strong compositional changes, with more fire-resistant species, which are species that establish in disturbed areas and encouraging grasses, resulting in savanna encroachment into gallery forests. Consequences on the long-term should be monitored.