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地球上９８％的氮素存在于原生岩（火成岩）中，但其对氮素循环贡献甚微；大气圈中的气态氮仅是地球中总氮素质量的１．９％，但实际上是供应所有生命需要的唯一氮源；生物圈中的氮量很小，然而全球植物初级净产物中９０％～９７％的氮在生物圈内循环。氮素在生物圈中的循环主要包括增加、损失和转化３个途径，这种循环因生态系统而不同。
98% of the earth’s nitrogen is present in protoliths (igneous rocks), but it contributes little to the nitrogen cycle; the gaseous nitrogen in the atmosphere is only 1.9% of the total nitrogen in the earth, but in fact The only source of nitrogen for all life is supplied; the nitrogen in the biosphere is small, whereas 90% to 97% of the nitrogen in primary plant products worldwide circulates within the biosphere. The cycle of nitrogen in the biosphere mainly includes three ways of increase, loss and transformation. The cycle varies from ecosystem to ecosystem.