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积反应的机制密歇根理工大学和密歇根大学的科学家们已获得美国国家科学基金会的资助，继续对北方阔叶林长期氮沉积的影响进行长期调查。这笔资金继续进行1993年开始的一项长期实地试验。在密歇根州的四个研究地点，每年每平方米增加3克硝酸盐氮。十年后，这些森林生长得更快，储存了更多的碳，并在生根区以下泄漏了大量的氮和碳。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量。他们将研究硝酸盐的添加如何改变根和菌根真菌之间的共生关系，从而可能使树木分配更多的光合作用来生长。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育（树木生长和死亡）和枯木碎片积累的影响。这种巨大的死亡物质储存着碳，并为更多样化的动植物群落提供了栖息地。

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.