On the pee! A mechanistic exploration of nitrogen and carbon cycling dynamics in the urine patch.

该项目将实验室和野外实验与数据探索和建模相结合，以提高对尿片中N和C动态控制因素的理解。绘制N和C循环过程的动态图将在实验室将牛尿应用于土壤(旱地和低地)，并将随着时间的推移确定土壤NO3、NH4、DOC、pH和不同区域(中部、中部、外部和扩散区)的氧化还原浓度的同步变化。PH值和O2敏感的光管将被用于可视化和量化土壤环境的变化。将在土壤样本上测定N和C酶的微生物基因表达。尿液成分与N、C循环的联系将从放牧的低地和高地牧场收集尿氨酸，并在将其应用于土壤和评估对N、C循环速率和损失的影响之前确定其组成。15N标记的尿液将用于Denis土壤培养(北威克)，以确定尿液成分对N2O：N2的影响。14C标记的嘌呤衍生物，如马尿酸，将以更快的速度应用于土壤，以确定它们的命运和对N循环的影响。在山坡尿液的不同部位沉积的尿块中的N和C循环将被应用于山坡的不同区域(水文)，以检验土壤化学、物理和生物特性以及气候因素(例如，风速-Redeker等，2015)的差异影响N和C循环以及尿块损失的假设。数据探索和建模学生将探索是否可以使用来自该项目的新数据来改进现有的N和C循环机制模型，例如DNDC，或者统计建模方法是否能更好地反映尿斑不同区域内N和C循环随时间的变化。Redeker等人。(2015)生物地理科学12,7423-7434。

The project combines laboratory and field experimentation with data exploration and modelling to improve the understanding of factors controlling N and C dynamics within urine patches.Mapping the dynamics of N and C cycling processes Cattle urine will be applied to soil (upland and lowland) in the laboratory, and simultaneous changes in soil NO3, NH4, DOC, pH and redox concentrations in different (central, middle, outer and 'diffusive') zones of the patch will be determined through time. pH and O2 sensitive optodes will be used to vizualise and quantify changes in the soil environment. Microbial gene expression of N and C enzymes will be determined on soil samples. Linking urine composition with N and C cyclingUrine will be collected from livestock grazing lowland and upland pastures and its composition determined before applying to soil and assessing effects on rates of N and C cycling and losses. 15N labelled urine will be used in a DENIS soil incubation (North Wyke) to determine effects of urine composition on the N2O:N2. 14C labelled purine derivatives, e.g. hippuric acid, will be applied at increasing rates to soil to determine their fate and effect on N cycling.N and C cycling in urine patches deposited in different parts of a hillslope Urine will be applied to different zones (hydrological) of a hillslope to test the hypothesis that differences in the soil's chemical, physical and biological properties, and climatic factors (e.g. wind speed - Redeker et al., 2015) affect N and C cycling and losses from urine patches.Data exploration and modelling The student will explore if new data from this project can be used to improve existing mechanistic N and C cycling models, e.g. DNDC, or if a statistical modelling approach can better reflect the changes in N and C cycling within different zones of the urine patch through time. Redeker et al. (2015) Biogeosciences 12, 7423-7434.