Agroforestry systems can minimize heat stress and improve cattle welfare, but the influence of the forest component in microclimatic changes in the southern Amazon remains unclear. This study aimed to compare the thermal comfort indices in grass monoculture and integrated systems. The three systems were pasture under full sunlight (PFS), integrated (triple-row) livestock-forestry (ILFT), and integrated (single-row) livestock-forestry (ILFs), across four seasons, for two years, from June 2017 to June 2019. We assessed photosynthetically active radiation (PAR), air temperature, relative humidity, black globe temperature, and wind speed. Thermal comfort indices such as temperature-humidity index (THI), black globe temperature-humidity index (BGHI), and radiant thermal load (RTL) were calculated based on microclimate data daily-collected from 8:00 to 16:00. The ILFT mean THI (76.8) was slightly lower than ILFS and PFS. The BGHI and RTL values decreased as shading increased (PFS > ILFs > ILFT). The most challenging heat stress conditions for grazing animals occurred predominately during winter and autumn. In conclusion, the presence of trees in pastures of the southern Amazon improved the microclimate and, consequently, the thermal comfort indices. Agroforestry systems can foster an environment with a more suitable thermal comfort or less restrictive to animal performance, which contribute to mitigating global climate change for forage-livestock systems in Brazilian Amazon.

中文翻译：

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巴西亚马逊南部农林业系统热舒适指数的改进

农林业系统可以最大限度地减少热应激并改善牛的福利，但森林成分对亚马逊南部小气候变化的影响仍不清楚。本研究旨在比较草单一栽培系统和综合系统的热舒适指数。从 2017 年 6 月起，这三个系统是全日照下的牧场（PFS）、综合（三行）畜林（ILFT）和综合（单行）畜林（ILF），跨越四个季节，为期两年到 2019 年 6 月。我们评估了光合有效辐射 (PAR)、气温、相对湿度、黑球温度和风速。温湿度指数（THI）、黑球温湿度指数（BGHI）、辐射热负荷（RTL）等热舒适指数是根据每天收集的8个小气候数据计算得出的：00 至 16:00。ILFT 平均 THI (76.8) 略低于 ILFS 和 PFS。BGHI 和 RTL 值随着阴影的增加而降低（PFS > ILFs > ILFT）。放牧动物最具挑战性的热应激条件主要发生在冬季和秋季。总之，亚马逊南部牧场中树木的存在改善了小气候，从而改善了热舒适指数。农林业系统可以营造一个具有更合适的热舒适度或对动物性能限制更少的环境，这有助于缓解巴西亚马逊地区牧草-畜牧系统的全球气候变化。放牧动物最具挑战性的热应激条件主要发生在冬季和秋季。总之，亚马逊南部牧场中树木的存在改善了小气候，从而改善了热舒适指数。农林业系统可以营造一个具有更合适的热舒适度或对动物性能限制更少的环境，这有助于缓解巴西亚马逊地区牧草-畜牧系统的全球气候变化。放牧动物最具挑战性的热应激条件主要发生在冬季和秋季。总之，亚马逊南部牧场中树木的存在改善了小气候，从而改善了热舒适指数。农林业系统可以营造一个具有更合适的热舒适度或对动物性能限制更少的环境，这有助于缓解巴西亚马逊地区牧草-畜牧系统的全球气候变化。