From Genes to Ecosystems: Mechanisms Controlling Long-Term Ecosystem Response to Nitrogen Deposition

从基因到生态系统：控制长期生态系统对氮沉降的反应的机制密歇根理工大学和密歇根大学的科学家们已经收到了NSF的资助，继续长期调查慢性氮沉降对北方硬木林的影响。 该基金继续进行1993年开始的长期实地试验。 密歇根州的四个研究地点每年接受每平方米三克硝酸盐氮的实验性添加。 十年后，这些森林生长得更快，储存了更多的碳，并将大量的氮和碳泄漏到根部以下。 在接下来的三年里，研究人员将确定长期添加硝酸盐如何改变土壤真菌分解凋落物和枯木的能力，从而增加土壤中的碳储存。 他们将研究硝酸盐添加物改变根系和菌根真菌之间共生关系的方式，从而可能使树木分配更多的光能用于生长。 他们将研究叶片氮含量增加对光合作用的影响，这也会影响树木的生长。 最后，他们将研究氮添加对林分发展（树木生长和死亡率）和死木残体积累的影响。 这种巨大的死亡物质储存碳，并为更多样化的植物和动物群落提供栖息地。

From Genes to Ecosystems: Mechanisms Controlling Long-Term Ecosystem Response to Nitrogen DepositionScientists at Michigan Technological University and the University of Michigan have received funding from NSF to continue a long-term investigation of the effects of chronic nitrogen deposition on northern hardwood forests. The funding continues a long-term field experiment initiated 1993. Four study sites in Michigan, annually receive experimental additions of three grams of nitrate-nitrogen per square meter. After a decade, these forests grow faster, store more carbon, and leak significant quantities of nitrogen and carbon below the rooting zone. During the next three years, the investigators will determine how chronic nitrate additions alter the ability of soil fungi to break down litter and dead wood, leading to increased carbon storage in soils. They will study the way nitrate additions alter the symbiotic relationship between roots and mycorrhizal fungi, potentially allowing trees to allocate more photosynthate to growth. They will examine the effects of increased leaf nitrogen content on photosynthesis, which also can affect tree growth. Finally, they will study the effects of nitrogen additions on stand development (tree growth and mortality) and the accumulation of dead woody debris. This large dead material stores carbon and provides habitat for a more diverse plant and animal community.