Influence of Tree Roots on Nitrogen Mineralization
Abstract:This study compared the total carbon (C), mineral nitrogen (N) contents and N mineralization potentials of the rhizospheric and bulk soils, collected at two depths in three forest sites in France. The site at Breuil is a comparative plantation of different species with or without fertilization, the Fougères site is a time sequence of four Fagus sylvatica L. stands including a limed plot, and the Aubure site is a comparison between adjacent young and old Picea abies. (L.) Karst stands with different nitrifying activity. Mineral N was extracted from fresh soil with K2SO4 and after laboratory incubation at 15°C for 2 days or 1 week. The moisture, C and N contents of the rhizospheric soil were higher than in the bulk soil in the A1 horizon, but only slightly higher or similar in A1B horizons. Soil-extractable NH4 and net mineralization were much larger in the rhizospheric soil than in the bulk soil. Soil-extractable NO3 and net nitrification were not significantly different. Soil-extractable NH4 and net N mineralization were linearly and positively related to the soil C (or N) contents, but the relationship was stronger and the amount of mineral N per gram of carbon was higher for rhizospheric soil. This suggests that the quality of rhizospheric carbon should be taken into account. Net N mineralization was negatively related to the soil C/N ratio. In summary, tree roots appear to have a strong influence on N transformation in soils.
Document Type: Research Article
Publication date: January 1, 2003