Some Effects of Afforestation with Lodgepole Pine on Rates of Nitrogen Mineralization in Peat

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Abstract
Rates of mineral nitrogen production and carbon dioxide evolution in incubated samples from the upper 300mm of peat beneath lodgepole pine ( Pinus contorta Dougl.) have been compared with those for adjacent unplanted areas at each of six sites in the North of Scotland. Under both aerobic (moist) and anaerobic (water logged) conditions, rates of mineral nitrogen production at 30°C are strongly influenced by peatland type, sampling depth and afforestation. During the early stages of the incubation under aerobic conditions, samples of planted peat showed a more rapid accumulation of mineral nitrogen than did samples from unplanted areas, the amounts after 17 days being 170ppm and 46ppm mineral N, respectively; after 62 days however, the difference was no longer significant. The mean rate of CO 2 production averaged 446μg CO 2 g −1 day −1 in planted as against 728μg in unplanted peat. Under anaerobic conditions, amounts of mineral nitrogen accumulated were similar in planted and unplanted sites but a difference in accumulation between the 0–150 and 150–300mm horizons in unplanted peat was significantly reduced beneath the trees.