Abstract Forage grass canopies may be affected by the shaded microclimate in silvopastoral (SP) systems throughout the year. This in turn may affect forage plant characteristics. Our objective was to assess microclimate effects on the responses of Marandu palisadegrass {Urochloa brizantha (Hochst. ex A. Rich.) R. D. Webster [syn. Brachiaria brizantha (Hochst. ex A. Rich.) Stapf.]} under continuous stocking in an SP system with Eucalyptus urograndis (hybrid of Eucalyptus grandis W. Hill ex Maiden and Eucalyptus urophylla S. T. Blake). Trees were planted in triple rows (grove), with three groves per 2-ha silvopasture experimental unit (11° 51′ S, 55° 35′ W). The spacing between groves was 30 m, and tree density was 135 ha–1, in East-West orientation. Microclimate and forage plant variables were evaluated from December 2016 to March 2018 in the treatments consisting of “full sun” (FS) grass monoculture pasture and at three distances from the grove: 7.5 m North (7.5 N), 15 m (15), and 7.5 m South (7.5S). Photosynthetically active radiation (PAR) was greatly affected and positively associated with most of the responses of Marandu palisadegrass. On average, PAR reduction in relation to FS was 8, 24, and 40 % for 15, 7.5 N, and 7.5S, respectively. The greatest maximum temperatures (35.8 °C) and the least minimum temperatures (15.8 °C) were registered during the Winter. Both forage accumulation rate (∼ 45 kg ha−1 d-1) and leaf accumulation rate (∼ 19 kg ha-1 d-1) were similar between FS and 7.5S (most shaded distance). Shade tolerance mechanisms of palisadegrass under grazing were associated with increases in specific leaf area and leaf proportion, allowing shaded pastures to sustain productivity at levels equivalent to those of pastures without shade.

中文翻译：

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小气候对巴西中部亚马逊生物群落林牧系统中遮荫栅栏草场冠层特征的影响

摘要 牧草树冠可能全年受到林牧系统中阴凉小气候的影响。这反过来可能会影响牧草植物的特性。我们的目标是评估小气候对 Marandu palisadegrass {Urochloa brizantha (Hochst. ex A. Rich.) RD Webster [syn. Brachiaria brizantha (Hochst. ex A. Rich.) Stapf.]} 与 Eucalyptus urograndis（Eucalyptus grandis W. Hill ex Maiden 和 Eucalyptus urophylla ST Blake 的杂交种）在 SP 系统中连续放养。树木种植成三行（树林），每 2 公顷林场试验单元（11° 51' S，55° 35' W）种植三个树林。林间间距为 30 m，树木密度为 135 ha-1，呈东西向。2016 年 12 月至 2018 年 3 月，在“全日照”(FS) 草单一栽培牧场和距树林三个距离的处理中评估了微气候和饲料植物变量：北 7.5 m (7.5 N)、15 m (15)和 7.5 m 南 (7.5S)。光合有效辐射 (PAR) 受到很大影响，并与 Marandu palisadegrass 的大多数反应呈正相关。平均而言，对于 15、7.5 N 和 7.5S，与 FS 相关的 PAR 降低分别为 8%、24% 和 40%。最高最高温度 (35.8 °C) 和最低最低温度 (15.8 °C) 记录在冬季。FS 和 7.5S（最阴影距离）之间的草料积累率（~ 45 kg ha-1 d-1）和叶片积累率（~ 19 kg ha-1 d-1）相似。