Nitrogen Storage in Alpine Plants

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This study tests the hypothesis that storing nitrogen over winter is an important adaptation in alpine plants. The alpine environment is characterized by: 1) a short growing season, (2) low soil temperatures, and 3) low nitrogen (N) availability. By using N that is stored during one growing season plants can begin growth in the following spring, even though soils are too cold for them to acquire N from the soil. This may allow them to take maximum advantage of the short alpine growth season and to quickly flower and set seed before the danger of frost becomes great. The investigators will determine when plants are using nitrogen for growth, and when plants are able to take nitrogen from the soil. If they find that plants start growing before they can acquire N in the spring, the hypothesis will be supported. However, determining when N is actually available to plants is a complicated task. Nitrogen availability is determined by the amount of mineral N in the soil, the rate at which this N is added (from rain or snow, or from decomposition of old plant matter) and the relative ability of plants versus soil microbes to acquire this N. Therefore, the annual pattern of N ion concentration in the soil, the rate of production of these ions from decomposition, and the relative ability of plants and soil microbes to assimilate this nitrogen must be determined. The study is significant for several reasons. First, it will advance basic understanding of plant N allocation and plant- nutrient relations in the alpine environment. The manner in which a plant allocates its resources can be as important as the quantity of resources it garners from the environment in determining a plant's ultimate ability to survive. Second, the study will address the important general question "to what extent do microorganisms compete for nitrogen with higher plants?" Awareness is growing that such competition can have a potent affect on plant nutrient status. These questions have practical implications. For example, an understanding of N storage in alpine plants may provide insight into what happens when fruit trees overwinter in temperate areas. By learning how soil temperature affects N cycling in the alpine, scientists may be able to provide insight into the fate of N fertilizer in cold agricultural systems with a goal of more efficient use of fertilizer and reduced ground water pollution by nitrogen fertilizers. Finally, denitrification of nitrate into nitrous oxide (a greenhouse gas) is affected by many of the soil parameters tested in this study. These results could be useful in predicting the effect of polar warming on greenhouse gas emissions from the arctic.