Abstract Ecosystem services provided by silvopastoral systems are mediated by specific management practices, environmental conditions, and overall design of the system. We hypothesized that selection of tree species affects understory forage nutritive value and productivity, light/shade environment, and microclimate. The silvopastoral system was located at the Center for Environmental Farming Systems in Goldsboro, North Carolina, USA. Three overstory tree-species were Pinus palustris (PP; longleaf pine), Pinus taeda (PT; lobloblly pine), and Quercus pagoda (QP; cherrybark oak). The understory forage component consisted of a four-way mixture of native warm-season grasses [big bluestem (Andropogon gerardii, ‘Eastern’, KY origin), eastern gamagrass (Tripsacum dactyloides, MO origin), indiangrass (Sorghastrum nutans, ‘NC ecotype’), and switchgrass (Panicum virgatum, ‘Alamo’)]. The experimental design was an RCBD with 3 replicates. There was no effect of seedbed preparation (till versus no-till) on forage establishment. Understory dry matter yield, crude protein and total digestible nutrient concentrations of the harvested forage were not affected by tree species, with the exception at the 3.5 south sampling point. Overstory effects on microclimate variables were not different among tree-species, but were more noticeable during the daytime of the summer months, and were at the most 1-degree point for temperature and temperature-humidity index and 3 points for relative humidity. The silvopasture design in our study provided year-round shade by the tree-component, with varying levels of shade (ranging from 90 to 6% of incident photosynthetic active radiation) due to geographic location, tree species, and season. Our results describe and highlight the potential of trees in a silvopasture design in the southeastern USA to mitigate changes in temperature, humidity, the temperature-humidity index, and forage productivity and as a function of tree species and at different distance from the trees.

中文翻译：

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树种对美国东南部林场林下牧草生产力和小气候的影响

摘要 林牧系统提供的生态系统服务受特定管理实践、环境条件和系统总体设计的影响。我们假设树种的选择会影响林下草料的营养价值和生产力、光照/阴影环境和小气候。林牧系统位于美国北卡罗来纳州戈尔兹伯勒的环境农业系统中心。三种上层树种是沼泽松（PP；长叶松）、火炬松（PT；火炬松）和栎树（QP；樱桃皮栎）。林下草料成分由本地暖季草 [big bluestem (Andropogon gerardii, 'Eastern', KY 起源), 东部 gamagrass (Tripsacum dactyloides, MO 起源), 印度草 (Sorghastrum nutans, 'NC '), 和柳枝稷（Panicum virgatum，'Alamo'）]。实验设计是具有 3 个重复的 RCBD。苗床准备（耕作与免耕）对牧草建立没有影响。收获草料的林下干物质产量、粗蛋白和总可消化营养浓度不受树种的影响，3.5 南采样点除外。盖层对小气候变量的影响在树种之间没有差异，但在夏季的白天更为明显，温度和温湿度指数最高为 1 度，相对湿度为 3 点。我们研究中的林场设计通过树木组件提供全年遮荫，由于地理位置、树种和季节而具有不同程度的阴影（范围为入射光合有效辐射的 90% 到 6%）。我们的结果描述并强调了美国东南部林场设计中树木的潜力，以减轻温度、湿度、温湿指数和饲料生产力的变化，以及作为树种和距离树木不同距离的函数。