Nitrogen is the primary limiting nutrient for most temperate forests and plays a major role in determining the actual rate of forest growth. Adding nitrogen fertilizer to forests can often increase growth in the short term, but prolonged nitrogen enrichment can eventually lead to declines in growth. There are three common sources of nitrogen in natural forests. The most important source is from bacteria that are associated with roots on many plants. These bacteria can fix nitrogen from the nitrogen-rich air in the soil and convert it to a form that can be used by plants. The other common source is from lightning storms which fix nitrogen from the atmosphere in the form of water-soluble nitrous oxides. Lastly, nitrogen is available for plant growth through nitrogen mineralization, which breaks down nitrogen from organic material found in soils. In regions with large numbers of vehicles such as Southern California and the densely populated areas of Europe, nitrogen deposition related to vehicle emissions has increased forest growth of the trees. However, the excess nitrogen also can also create other problems by altering nutrient cycles and increasing nitrogen leaching from soils, creating problems in neighboring waterways. Tom DeGomez, Area Agent and Regional Specialist, University of Arizona

Browse related Faqs by tag: soils, forest, nitrogen, nutrients, climate forests woodlands