Abstract Sustainable intensification of livestock production systems has become a global demand. In silvopastoral systems, contrasting shading levels caused by the presence of trees interferes in the productive responses of the pasture under grazing. The environment in which plants develop in a pasture canopy is dynamic and complex due to the nature of soil-plant-animal interactions. These dynamic aspects can be rationalized, evaluated, and explained using mathematical modeling. The objective of the present study was to parameterize the APSIM-Tropical Pasture model to simulate palisadegrass [Brachiaria brizantha (Hochst A Rich) Stapf, syn. Urochloa brizantha] growth under continuous stocking and variable stocking rate, in a full sun system and in contrasting shading conditions of a silvopastoral setting with eucalyptus (Eucalyptus grandis W. Hill ex Maiden × Eucalyptus urophylla S. T. Blake). Trees were planted in triple-row groves, with three groves per 2-ha silvopasture area. The spacing between groves was 30 m, and tree density was 135 ha−1, in East-West orientation. The data used to calibrate and validate the model were collected in a 36-month experiment with full sun and shade treatments of the silvopastoral setting in Sinop, MT, Brazil. Live forage mass estimates had coefficient of determination varying between 0.76 and 0.94, Willmott agreement index ranged from 0.93 to 0.96, and root mean square error between 275 and 610 kg DM ha−1. The APSIM-Tropical Pasture model can simulate Marandu palisadegrass growth under continuous stocking with variable stocking rate, but improvements are needed to better simulate the effect of N fertilizations in different periods on growth. The model can simulate pasture growth under shading levels but our simulations did not consider competition for soil moisture, which should be considered in the future, since it can be an important factor for other silvopastoral designs or microclimatic conditions.

中文翻译：

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用于模拟单一栽培和林牧系统连续放养条件下栅栏草生长的 APSIM 模型的参数化

摘要 畜牧生产系统的可持续集约化已成为全球需求。在林牧系统中，由树木的存在引起的对比阴影水平会干扰放牧牧场的生产反应。由于土壤-植物-动物相互作用的性质，植物在牧场冠层中发育的环境是动态和复杂的。可以使用数学建模对这些动态方面进行合理化、评估和解释。本研究的目的是参数化 APSIM-Tropical Pasture 模型以模拟栅栏草 [Brachiaria brizantha (Hochst A Rich) Stapf，syn。Urochloa brizantha] 在连续放养和可变放养率、全日照系统和林牧环境与桉树（Eucalyptus grandis W. Hill ex Maiden × Eucalyptus urophylla ST Blake)。树木种植在三行小树林中，每 2 公顷林场种植三棵小树林。林间间距为 30 m，树木密度为 135 ha-1，呈东西向。用于校准和验证模型的数据是在巴西锡诺普林牧环境的 36 个月全日照和遮荫处理实验中收集的。活草料质量估计的决定系数介于 0.76 和 0.94 之间，威尔莫特一致性指数介于 0.93 到 0.96 之间，均方根误差介于 275 和 610 kg DM ha-1 之间。APSIM-Tropical Pasture模型可以模拟连续放养条件下马兰杜栅栏草的生长，放养率可变，但需要改进以更好地模拟不同时期施氮对生长的影响。