Effect of Amazonian tree species on soil and pasture quality in silvopastoral systems

ABSTRACT With the expansion of livestock in the Amazon region, a high percentage of pasture areas are degraded and unproductive. Novel strategies are needed, including the use of native tree species, to simultaneously achieve economic and ecosystem benefits. This study aimed at assessing the effects of five multipurpose native tree species on soil fertility and forage quality of Urochloa brizantha pastures in the southern Amazon. Soil and forage samples were collected under the crown and adjacent to 25 isolated trees belonging to five species during a dry and a rainy season. The presence of native trees positively affected the level of potassium, calcium and manganese in the soil, as well as the mineral matter and crude protein of the forage, especially in the dry season, suggesting a protective effect against the seasonal drought. The tree species had variable effects on soil fertility and forage quality. Soil under Apeiba tibourbou had higher potassium levels, while the forage under Handroanthus serratifolius had higher protein and fiber content. Our results indicate that it is important to diversify silvopastoral systems in the Amazon through the use of native tree species, contributing to the design of novel silvopastoral strategies in the region. Common multipurpose tree species with widespread natural distribution could be used as a complementary aspect of pasture management to provide a protective effect against drought, contribute to enhanced nutrient cycling and even increase forage quality.

摘要
伴随亚马逊地区畜牧产业的扩张，超大面积牧场出现退化且生产力低下的困境。亟需研发兼顾经济效益与生态效益的新型牧场管理方案，其中乡土树种（native tree species）的应用是可行路径之一。本研究以亚马逊南部的布氏臂形草（Urochloa brizantha）牧场为研究载体，评估5种多功能乡土树种对该牧场土壤肥力与饲草品质的影响。研究人员于旱季与雨季两个时段，分别在5个树种的25株孤立树木的冠幅下及其邻近区域采集土壤与饲草样本。研究发现，乡土树种的存在可显著提升土壤中钾、钙、锰元素的含量，同时改善饲草的矿物质与粗蛋白水平，该效应在旱季尤为显著，表明乡土树种可缓解季节性干旱带来的负面影响。不同树种对土壤肥力与饲草品质的调控效果存在显著差异：阿佩巴椴（Apeiba tibourbou）冠下土壤的钾元素含量更高，而锯齿叶黄钟木（Handroanthus serratifolius）冠下饲草的蛋白与纤维含量更为优异。本研究结果证实，通过乡土树种的应用优化亚马逊地区的林牧复合系统（silvopastoral systems）多样性具有重要价值，可为该区域新型林牧复合管理策略的设计提供科学参考。自然分布广泛的多功能乡土树种可作为牧场管理的补充手段，用以缓解干旱胁迫、促进养分循环，甚至提升饲草品质。