Instability of insular tree communities in an Amazonian mega-dam is driven by impaired recruitment and altered species composition
Instability of insular tree communities in an Amazonian mega-dam is driven by impaired recruitment and altered species composition
复制标题
亚马逊巨型水坝中岛屿树木群落的不稳定是由补充受损和物种组成改变造成的
DOI：
10.1111/1365-2664.13313
复制
发表时间：
2019
影响因子：
5.7
通讯作者：
Jones I
中科院分区：
文献类型：
--
作者：
Jones I
巨型水坝造成了高度分散的群岛，影响了残留森林隔离区的生物多样性和生态系统功能。这项研究评估了大坝引起的破碎化对岛屿热带树木群落的长期影响，旨在提出强有力的建议，以减轻与未来大坝开发相关的一些有害生物多样性影响。我们对位于巴西亚马逊巴尔比纳大坝36个岛屿和三个大陆连续森林地点的89个永久地块的成年树和树苗进行了清点。我们研究了幼树和成年树群落在补充、结构和组成方面的差异，以及与地块、斑块和景观尺度属性（包括面积、隔离和火灾严重程度）的关系。（平均值± 95% CI 48.6 ± 3.8）和成年树（5 ± 0.2）株/0.01公顷，比邻近的大陆连成林（幼树65.7 ± 7.5株，成年树5.6 ± 0.3株）要高。岛屿幼树和成年树群落比大陆站点更不相似，物种组成显示出从大陆森林的方向性转移，引起火灾的严重性，岛屿面积，和isolation.Insular幼树补充下降，随着火灾的严重性增加，具有较高的社区加权平均木材密度的树木群落表现出最大的招聘下降。我们的研究结果表明，岛屿上的树木群落是不稳定的，由于岛屿上树木补充和密度的减少，稀有物种容易灭绝，可能导致巴尔比纳3,500多个水库岛屿未来生物多样性和生态系统功能的丧失。在巴尔比纳，火灾和栖息地面积和连通性的减少是树木群落衰退的驱动因素，尽管有94万公顷的Uatumã生物保护区提供了严格的保护，但经过28年的孤立化。考虑到许多水坝计划建在低地、中度起伏的亚马逊河流域，我们建议水坝开发战略明确考虑：（a）水坝位置，旨在尽量减少形成小岛屿（<10公顷）和孤立岛屿;（B）在干旱期间保持水库水位，以减少火灾风险;（c）在环境影响和抵消计算中包括岛屿总面积。理想情况下，我们建议在低地热带地区寻找水电的替代方案，因为河流蓄水会造成深远的生物多样性损失和生态系统破坏。
Mega‐dams create highly fragmented archipelagos, affecting biodiversity and ecosystem functioning in remnant forest isolates. This study assessed the long‐term impact of dam‐induced fragmentation on insular tropical tree communities, with the aim of generating robust recommendations to mitigate some of the detrimental biodiversity impacts associated with future dam development.We inventoried adult and sapling trees across 89 permanent plots, located on 36 islands and in three mainland continuous forest sites in the Balbina Dam, Brazilian Amazon. We examined differences in recruitment, structure, and composition of sapling and adult tree communities, in relation to plot‐, patch‐ and landscape‐scale attributes including area, isolation, and fire severity.Islands harboured significantly lower sapling (mean ± 95% CI 48.6 ± 3.8) and adult (5 ± 0.2) tree densities per 0.01 ha, than nearby mainland continuous forest (saplings, 65.7 ± 7.5; adults, 5.6 ± 0.3). Insular sapling and adult tree communities were more dissimilar than in mainland sites, and species compositions showed a directional shift away from mainland forests, induced by fire severity, island area, and isolation.Insular sapling recruitment declined with increasing fire severity; tree communities with higher community‐weighted mean wood density showed the greatest recruitment declines. Our results suggest that insular tree communities are unstable, with rare species becoming extinction‐prone due to reduced tree recruitment and density on islands, potentially leading to future losses in biodiversity and ecosystem functioning across Balbina's >3,500 reservoir islands.Policy implications. In Balbina, fire and reduced habitat area and connectivity were drivers of tree community decay after only 28 years of insularization, despite strict protection provided by the ~940,000 ha Uatumã Biological Reserve. Given that many dams are planned for lowland, moderately undulating Amazonia, we recommend that dam development strategy explicitly considers (a) dam location, aiming to minimize creation of small (<10 ha) and isolated islands, (b) maintaining reservoir water levels during droughts to reduce fire risk, and (c) including aggregate island area in environmental impact and offset calculations. Ideally, we recommend that alternatives to hydropower be sought in lowland tropical regions, due to the far‐reaching biodiversity losses and ecosystem disruption caused by river impoundment.