Avalos Gerardo, Bermúdez Esteban
Rev Biol Trop. 2016 Dec;64(4):1383-99.
Roads immersed in conservation areas will increase in number, size, and traffic over the next decade, and thus, understanding their effects on forest-dependent wildlife is crucial for improving current management practices and reducing the negative impacts of roads on sensitive species. We examined the influence of route 32 (a.k.a. Guápiles Highway) on temporal and spatial changes in the structure of the avifauna of Braulio Carrillo National Park, Costa Rica, a site crossed by this road along 25 km. The highway connects the capital city of San José with the Harbor of Limón in the Caribbean Sea (142 km). Although the road is narrow (12 m in width and comprised by two lanes along most of the route) it services over 1.5 million motor vehicles per year, 12 % are heavy trucks and trailers. We expected the highway to divide the avifauna, and thus to observe significant differences in species structure on opposite sides of the road. We described changes in bird diversity between wet and dry seasons at Las Palmas and Ceibo trails located on opposite sides of the highway (14 point counts per trail), and evaluated how abundance and diversity varied with road distance. Censuses took place during wet and dry seasons from 2002 to 2005. We listed 245 species and 6 035 observations during the 4-yr survey. Rare species dominated the avifauna (65 % of species < 5 observations), and species overlap between trails was high (Sorensen= 71 %; Morisita= 0.96). Species accumulation curves varied little among trails, yielding 190 species. Resident species represented 70 % of observations, followed by elevational (15 %) and long-distance migrants (1-2 %). Understory species were the most abundant (60 %) followed by canopy birds (30 %). Species turnover rate was 55 % between seasons, but species composition between trails remained homogeneous. Overall, birds were avoiding the road (abundance increased away from the road) although other diversity parameters (richness, dominance, Shannon index, and equitability) were not influenced by road proximity. Although the avifauna remained homogeneous on both sides of the road, which did not support the fragmentation hypothesis, the highway reduced the abundance and diversity of specialized understory insectivores associated with primary forests near the road. This highway will expand outside the National Park (from 2 to 4 lanes along 107 km from Río Frío to Limón) in the next years, which will increase traffic volume and road impacts within the Park. Roads are increasing across highly diverse tropical areas justifying the need for management practices based on the identification of sensitive groups.
未来十年，位于保护区内的道路数量、规模和交通流量将会增加。因此，了解这些道路对依赖森林的野生动物的影响，对于改进当前的管理措施以及减少道路对敏感物种的负面影响至关重要。我们研究了32号公路（又称瓜皮莱斯高速公路）对哥斯达黎加布劳利奥·卡里略国家公园鸟类群落结构时空变化的影响，该公路横穿该公园25公里。这条高速公路连接首都圣何塞和加勒比海的利蒙港（142公里）。尽管道路狭窄（宽12米，大部分路段为双车道），但每年的机动车流量超过150万辆，其中12%是重型卡车和拖车。我们预计这条高速公路会将鸟类群落分隔开来，因此预计在道路两侧观察到物种结构的显著差异。我们描述了位于高速公路两侧的拉斯帕尔马斯和塞沃小径在干湿季之间鸟类多样性的变化（每条小径14个样点统计），并评估了丰度和多样性如何随与道路的距离而变化。普查在2002年至2005年的干湿季进行。在为期4年的调查中，我们记录了245个物种和6035次观察。珍稀物种在鸟类群落中占主导地位（65%的物种观察次数少于5次），小径之间的物种重叠度很高（索伦森指数=71%；森下指数=0.96）。各小径间的物种累积曲线变化不大，共记录到190个物种。留鸟占观察次数的70%，其次是垂直迁徙鸟（15%）和长距离迁徙鸟（1 - 2%）。林下物种最为丰富（60%），其次是林冠层鸟类（30%）。季节间的物种周转率为55%，但小径间的物种组成保持均匀。总体而言，鸟类避开道路（丰度远离道路增加），尽管其他多样性参数（丰富度、优势度、香农指数和均匀度）不受与道路距离的影响。尽管道路两侧的鸟类群落保持均匀，这并不支持破碎化假说，但这条高速公路减少了与道路附近原始森林相关的特化林下食虫鸟类的丰度和多样性。未来几年，这条高速公路将在国家公园外扩建（从里奥弗里奥到利蒙的107公里路段从2车道扩至4车道），这将增加公园内的交通流量和道路影响。在高度多样化的热带地区，道路在不断增加，这证明了基于识别敏感群体的管理措施的必要性。
