Questions: Human activities are increasing the density of domestic grazers and global nutrient loads, modifying the main determinants of vegetation community dynamics. Grazing (top-down control) and nutrient availability (bottom-up control) may interactively modify plant biomass, which is particularly important in grasslands devoted to livestock production. Here, we aim to understand the interactive effects of grazing and fertilization on grassland plant biomass. We hypothesized that the joint effects of nutrient addition and domestic grazing on above-ground plant biomass are not additive, but they modify each other through changes in ground-level light, leaf nutritional quality, above-ground net primary productivity (ANPP), and below-ground plant allocation.

中文翻译：

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植物质量和初级生产力调节植物生物量对中等草原放牧和施肥联合效应的响应

问题：人类活动增加了家养食草动物的密度和全球养分负荷，改变了植被群落动态的主要决定因素。放牧（自上而下控制）和养分可用性（自下而上控制）可以交互改变植物生物量，这在专门用于畜牧生产的草地中尤为重要。在这里，我们旨在了解放牧和施肥对草地植物生物量的交互影响。我们假设养分添加和家养放牧对地上植物生物量的联合影响不是相加的，但它们通过地面光照、叶片营养质量、地上净初级生产力 (ANPP) 和地下植物分配。