ECOLOGY G. nutrient.pdf

G1 SOURCES AND CYCLES G1 SOURCES AND CYCLES 资源与循环 Key Notes 要点 Nutrients are gained and lost by communities in a variety of Nutrient sources ways. Mechanical weathering, chemical weathering, particularly 营养物资源 carbonation, are important processes. Simple dissolution of minerals in water also makes nutrients available from rock and soil. Water may carry nutrients in watercourses providing an important source in downstream areas. Atmospheric gases provide nutrient sources too, particularly carbon dioxide and nitrogen. Other nutrients from the atmosphere become available to communities as wetfall (rain, snow and fog) and dryfall (settling of particles during dry periods). 群落以形形色色的方式获得和损失营养物。机械风化、化学 腐蚀，特别是碳酸化作用，都是重要的过程。矿物质在水中 的简单溶解也使营养物从岩石和土壤中获得成为可能。在水 流中水可能携带着营养物，给下流地区提供一个重要的资源。 大气也提供营养物，特别是二氧化碳和氮。大气中其他营养 物可能以湿降落（雨，雪和雾）和干降落（干燥期间的颗粒 沉淀物）的方式回到群落。 Nutrient budgets in A particular nutrient atom taken up by an organism may terrestrial communities cycle continuously until eventually the nutrient will be lost 陆地群落的营 through any one of a number of processes that remove 养物预算 nutrients from the system. Release may be direct to the atmosphere or via bacterial action (as in the case of methane). For many elements, the most substantial pathway of loss is in streamflow. Other pathways of nutrient loss include fire, the harvesting of crops and deforestation.