Scale-dependent effects of plant and animal functional characteristics on nutrient cycling in pastures

在低投入管理的牧场和大型食草动物放牧的自然生态系统中，放牧动物粪便和尿液中排泄的营养物质在营养循环中发挥着重要作用。这些营养流涉及的排泄物补丁的规模的主要矿物营养物质的空间集中和空间分离。动物和植物的功能特性影响这种空间异质性的粒度和程度，以及植被和放牧动物的生物量摄入的养分通过排泄物输入的斑块尺度响应。生态学研究主要集中在食草动物在养分循环速度和化学计量方面的大规模效应，而农业研究主要关注小规模的排泄物斑块效应，并与它们发生的大规模系统分离。植物和动物的功能特性对养分循环有重要的影响，在排泄物斑块尺度上，生态学或农业研究尚未明确解决。该项目打算将生态学和农业研究中关于食草动物对养分循环影响的方法和概念联合收割机结合起来。它将研究动物排泄物对地上营养流和植物生物量营养化学计量的影响如何受到植物功能群和放牧动物功能特征的影响。研究系统将是一个长期的不施肥放牧实验，有两个实验因素：草地类型（多样性和以草为主）和放牧动物物种（牛和羊，体型、排泄物斑块大小和放牧选择性不同）。数据将收集在三个层次上：围场规模和斑块规模的数据在放牧系统和斑块规模的数据在模拟放牧。在围场规模，生物量生产力和营养浓度（氮，磷和钾），生物量和矿物营养物质的摄入量的放牧动物和粪便和尿液中的营养排泄物将被量化，并将被用来扩大规模的排泄物补丁的围场规模的影响。在斑块规模下，将在放牧牧场标记粪便、尿液和未受影响的对照斑块，以评估植物和食草动物对排泄物斑块的反应。切割实验模拟粪便和尿液补丁将被用来验证这些数据在受控条件下，并延长观察期和测量参数超出放牧可行的方案。过程参数，如脱叶间隔和脱叶严重程度将被选择来模拟放牧研究system.The项目预计推进大型草食动物对养分循环的影响的基础知识，解决通过草食动物排泄物的数量上重要的养分流量的小尺度异质性和功能特性的植物和草食动物，在这个尺度上的过程相关。

Both in low-input managed pastures and in natural ecosystems grazed by large herbivores, nutrients excreted in dung and urine of the grazing animals play an important part in the nutrient cycle. These nutrient flows involve spatial concentration and spatial separation of the main mineral nutrients at the scale of the excreta patch. Animal and plant functional characteristics influence the grain size and degree of this spatial heterogeneity, as well as the patch-scale responses of vegetation and grazing animal biomass intake to the nutrient input through excreta. While ecological research has strongly focused on large-scale effects of herbivory in terms of speed and stoichiometry of nutrient cycling, agricultural research has mostly regarded excreta-patch effects on a small scale and detached from the large-scale systems in which they occur. Plant and animal functional characteristics have important effects on nutrient cycling at the excreta-patch scale that have not yet been explicitly addressed in either ecological or agricultural research. The project intends to combine approaches and concepts from both ecological and agricultural research about herbivory effects on nutrient cycling. It will investigate how the effect of animal excreta on above-ground nutrient flows and on plant biomass nutrient stoichiometry is influenced by plant functional groups and grazing animal functional characteristics.The study system will be a long-term unfertilized grazing experiment with two experimental factors: sward type (diverse and grass-dominated) and grazing animal species (cattle and sheep, differing in body size, excreta patch size and grazing selectivity). Data will be gathered on three levels: paddock-scale and patch-scale data in the grazed system and patch-scale data under simulated grazing. At the paddock scale, biomass productivity and nutrient concentrations (nitrogen, phosphorus and potassium), biomass and mineral nutrient ingestion by the grazing animals and nutrient excretion in dung and urine will be quantified, and will be used to up-scale excreta patch effects to the paddock scale. At the patch scale, dung, urine and unaffected control patches will be marked in the grazed pasture to assess plant and herbivory responses to excreta patches. A cutting experiment with simulated dung and urine patches will be used to validate these data under controlled conditions and to extend observation period and measured parameters beyond the programme feasible under grazing. Process parameters such as defoliation interval and defoliation severity will be chosen to simulate those of the grazed study system.The project is expected to advance the basic knowledge about large-herbivore effects on nutrient cycling by addressing the small-scale heterogeneity of the quantitatively important nutrient flows through herbivore excreta and the functional characteristics of plants and herbivores that are process-relevant at this scale.