Seasonal changes in nitrogen-fixing activity and ultrastructure of Alnus hirsuta (Betulaceae) root nodules

Data on an important ecological property of the alder-tree, the nitrogen-fixing ability, are reported. Exemplified by Alnus hirsuta, the behavior of nitrogenase activity during the growing season has been characterized. In southern West Siberia its maximum falls on the period from late July to middle September. It has been shown that nitrogenase activity is correlated with on alder vegetation phases and seasonal changes in the ultrastructure of root nodules.