综述了畜尿特征及其对草地植被和家畜选择采食的作用。畜尿主要成分为尿素,尿斑N浓度一般为20-80 g N/m2。家畜排尿量和尿斑大小与家畜种类、饮水次数和放牧季节有关。畜尿空间分布表现为数量和浓度的不同,常呈线形函数形式随机分布于家畜采食路线周围,尿斑中心与边缘的尿N浓度差别很大。通常,畜尿对草地植物的影响限于尿斑区域,约为尿斑面积的2倍,作用时间可持续6-12个月;对草地植物生长具长期促进和短期灼烧作用,其效应大小与尿N浓度和施尿时期有关。一般畜尿促进禾草生长,抑制豆科草的生长和固氮作用。尿斑处植物的N成分比非施尿斑块高,植物吸收的N量随家畜年排泄N不同而异,尿排泄对植物生长的正效应发生于≤250 kg N/（hm^2·a）情况下。畜尿排泄增加草地植物多度、丰富度和群落多样性,并受放牧、培育措施的影响。不同植物对畜尿的响应不同,放牧家畜对尿斑不同植物的选食性和补偿性生长差异,是引起和维持草地异质性的重要因素之一。放牧家畜具优先选食和反复采食尿斑植物或高营养斑块的特点,亦经常在远离高营养植被斑块的地方采食。具体草地管理与生产实践中,可通过在草地采食不足的地方设置饮水点、补饲料及搭荫棚等措施,提高家畜对整个草地的利用,以降低家畜对尿排泄物密集区高N植被斑块的过度采食。
Trampling is one of the three impact activities(trampling,defoliation,and excretion) performed by a grazing animal on grassland and also the major reason for range degradation.Little is known about the result of trampling-induced feedback among the soil environment,grass,and their interrelationship.In addition, more information is needed about the effects of animal trampling on the managed grazing ecosystems.In typical steppe of loess plateau regions,where the management objective is to maintain the grassland ecosystem structure and function,the impacts of grazing trampling could be a serious problem.The object of the study was to separately evaluate the effect of trampling on the typical steppe in Huanxian County,eastern Gansu Province,China.A series of field experiments were conducted for two years including the tailing-up observation of trampling intensity of Tan-sheep in summer rotational grazing trail,trampling homogeneity trial,two-factor trail of simulated precipitation and experimental trampling.The results are as follows.1.Trampling intensity(TI) was proposed by this paper as the trampling area or trampling pressure created by a single or multiple grazing livestock per hectare during a unit time under free or rotational grazing.It had three expression methods: trampling pressure method,trampling area method,trampling frequency method.The trampling unit and Trampling Equivalent Unit(TEU) were put forward for the first time in order to define the calculation and conversion standard of TI.2.By tailing-up observation of the flocks on typical steppe of Huanxian County in Eastern Gansu Province,China,the regression analysis shows that livestock trampling intensity was increased by the power function of grazing intensity.This fully demonstrated that the trampling effects played a key role in the wholesomeness maintenance of grassland and the adjustment and control of the trampling effects of grazing livestock should be an important aspect of grazing management.3.Trampler was manufactured to imitate the mechanic
