Local and landscape characteristics shape amphibian communities across production landscapes in the Western Ghats

Global tropical forests have been modified and fragmented by commodity agroforests, leading to significant alterations in ecological communities. Nevertheless, these production landscapes offer secondary habitats that support and sustain local biodiversity. In this study, we assess community level and species-specific responses of amphibians to land management in areca, coffee and rubber, three of the largest commodity agroforests in the Western Ghats. A total of 106 agroforests across a 30,000 km2 landscape were surveyed for amphibians using a combination of visual and auditory encounter surveys. We used a Bayesian multi-species occupancy modeling framework to examine patterns of species richness, beta diversity, dominance structure and individual species occupancies. The influence of biogeographic variables such as elevation and latitude as well as microhabitat availability of streams, ponds and unpaved plantation roads were tested on amphibian species occupancy. Coffee agroforests had the highest species richness and lowest dominance when compared to areca and rubber. Beta diversity was highest in areca for within agroforest measures. Compared across agroforests, coffee had highest beta diversity with areca and rubber. Both elevation and latitude showed an overall positive association with amphibian occupancy although species-specific responses varied considerably. Microhabitat availability was one of the strongest predictors of amphibian occupancy, with mean community response being positive with presence of water bodies and roads. Pond presence increased species richness per site by 37% (species-specific responses in occupancy ranged from -2.7% to 327%). Stream presence alone did not change species richness but species-specific response ranged from -59% to 273%). Presence of plantation roads also increased species richness by 21.5% (species-specific response range -82% to 656%). Being unpaved with little vehicular traffic, plantation roads seem to provide additional habitats for amphibians. Presence of all three microhabitats at a site increased species richness by 75%. Our study highlights the importance of land management strategies that maintain diverse native canopy and freshwater bodies and other microhabitats in sustaining amphibian fauna. Market driven land-use change from coffee to other agroforest types will have detrimental effects on amphibian communities and their long-term sustainability in the Western Ghats.

全球热带森林已被商品农林复合系统改造并碎片化，导致生态群落发生显著改变。尽管如此，这类生产性景观仍可提供次生栖息地，支撑并维持当地生物多样性。
本研究针对西高止山脉（Western Ghats）三大商品农林复合系统——槟榔（areca）、咖啡（coffee）与橡胶（rubber）园，评估两栖动物的群落级与物种特异性响应，以解析其对土地管理措施的响应模式。
研究团队在面积达30000平方千米的区域内，共调查了106处农林复合系统，采用目视与声学偶遇调查相结合的方法开展两栖动物普查。
本研究采用贝叶斯多物种占用模型（Bayesian multi-species occupancy modeling）框架，分析物种丰富度、β多样性（beta diversity）、优势类群结构以及单一物种占用率的分布模式。
研究还检验了生物地理变量（如海拔、纬度）以及溪流、池塘、未铺装种植园道路等微生境可获得性对两栖动物物种占用率的影响。
相较于槟榔园与橡胶园，咖啡农林复合系统的物种丰富度最高，优势度最低。
就农林复合系统内部的β多样性（beta diversity）而言，槟榔园的β多样性最高；跨系统对比时，咖啡园与槟榔园、橡胶园之间的β多样性均为最高。
尽管物种特异性响应存在显著差异，但海拔与纬度整体上与两栖动物占用率呈正相关关系。
微生境可获得性是影响两栖动物占用率的最强预测因子之一，群落平均响应显示，水体与道路的存在对两栖动物具有正向作用。
池塘的存在可使单样地的物种丰富度提升37%（物种特异性占用率响应范围为-2.7%至327%）；仅溪流的存在未对物种丰富度产生显著影响，但物种特异性响应范围为-59%至273%。
种植园道路的存在同样可使物种丰富度提升21.5%（物种特异性响应范围为-82%至656%）。由于种植园道路为未铺装路面且车流量极低，其可为两栖动物提供额外的栖息空间。
若样地同时存在上述三类微生境，物种丰富度可提升75%。
本研究强调，维持多样的原生冠层、淡水生境及其他微生境的土地管理策略，对维持两栖动物群落至关重要。
以市场为导向的土地利用转型（将咖啡园转换为其他农林复合系统类型），将对西高止山脉的两栖动物群落及其长期存续产生不利影响。