Change in Distribution and Availability of Nitrogen with Forest Succession on North Slopes in Interior Alaska
1966
Heilman, Paul E.
Forest succession on north slopes in interior Alaska results in the development of sphagnum bogs on sites formerly occupied by productive forest. This process is one of gradual deterioration of site associated with the accumulation of moss layers on the forest floor. Advancing succession is accompanied by an increasing nitrogen deficiency in black spruce trees. Black spruce growing on the sphagnum bogs are extremely nitrogen deficient. As the moss layers thicken, the soils become increasingly cold with permafrost rising to within as little as 15 inches of the surface of the sphagnum soils. Examination of the depth distribution of nitrogen revealed very small quantities of nitrogen in the upper and warmer portions of these profiles, with the bulk of the nitrogen located in the very cold and latest to thaw, lower layers. In contrast, in the soils under birch of the nitrogen was located in the warmest upper layers. Under these conditions, much higher rates of mineralization of soil nitrogen must be obtained. The results show why burning, although changing many factors including volatilization of an undetermined amount of nitrogen, may lead to a large increase in available nitrogen because of the change in depth distribution of the nitrogen in the soil.
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