THE RELATIONSHIP BETWEEN SPECIES DIVERSITY AND NITROGEN CYCLING IN PASTURE

生物多样性的研究不仅对群落生态学，而且对应用生态学都具有重要意义。我们想知道生物多样性的程度是否会影响牧草氮循环的效率。许多科学家认为，生物多样性与生产之间有着密切的关系。如果生物多样性与生产力之间存在正相关关系，那么高生物多样性的生态系统具有较高的母体循环能力，如氮循环能力，因此，我们从管理对生物多样性的影响、生物多样性与氮循环的关系两个方面来了解草地生物多样性的作用，并通过对各草地的采样数据，测定了植物和土壤蜱类的物种多样性。氮素损失量由牛奶、肥料和饲料粮中的氮素含量计算，以考虑环境影响。为了测定从牛尿中回收氮到牧草生产中的效率，我们在另一个实验中使用了15 N标记的尿。 关于我们 部分奶农低投入牧场的植物生长量高于高投入牧场。植物和土壤蜱类多样性之间有很强的相关性。单位牧场产奶量的成本效益分析结果表明，奶牛产奶量存在最优投入。许多农民将达到最佳点，这意味着牛奶生产的高效率。20年来，牧草氮素损失率从80%以上下降到50%，单位牧草产奶效率与牧草生物多样性呈正相关，用15 N标记法估算了牧草氮素从牛尿中的回收率为37.37%~ 78.51%。因此，氮素损失在20%至60%之间.约20%的氮素损失来自于少量的尿施.约60%的氮素损失来自于大量的尿施.说明氮素损失速率受氮素输入量的影响，物种多样性高的草地具有较高的氮素回收能力。少

The study of bio-diversity is very important for not only community ecology but also applied ecology. We want to know whether degree of bio-diversity affects efficiency of nitrogen recycling in a pasture or not. Many scientists said that there are close relationship between bio-diversity and production. If there are positive relationships between bio-diversity and production then the ecosystem of high bio-diversity have high ability of maternal recycling such as nitrogen recycling.Then we tried to know the roll of bio-diversity in pasture by two aspects such as effects of management on biodiversity, relation between bio-diversity and nitrogen recycling.Species diversities of plant and soil tick were measured by sampling data from each pasture. Nitrogen losses were calculated by nitrogen amount in milk, fertilizer and feed grains for environmental impact. To measure the efficiency of nitrogen recovery from cattle urine to grass production we used 15N marked urine in another experiment.T … More he plant diversities of low-input pastures of were higher than high-input pastures in some dairy farmers. There is strong relationship between plant and soil tick diversity. Results of Cost-benefit analysis for milk production per unit pasture show the presence of optimal-input for milk production. Many farmers will arrive to optimal point that means high efficiency of milk production. The nitrogen losses were decreased from over 80 % to 50 % during these 20 years.There is a positive relationship between efficiency of milk production per unit pasture and bio-diversity.We estimated the recovery % of nitrogen from cattle urine to grass growth using 15N-marker method ranged 37.37 % to 78.51 %. Therefore nitrogen losses were ranged 20 % to 60 %. About 20 % of nitrogen loss was derived from small amount of urine application. About 60 % of nitrogen loss was derived from large amount of urine application. This result shows the rate of nitrogen loss was affected by amount of nitrogen input.A pasture of high species diversity would have high ability of nitrogen recovery. Less