Shoot nitrate reductase activities of field‐layer species in different forest types

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Abstract
Analysis of the activity of the substrate‐induced enzyme nitrate reductase in plants can be used to indicate the mode of nitrogen nutrition and the presence of nitrate in the soil. We made two surveys of current and maximally induced shoot nitrate reductase activities (NRA) in different forest types. Dwarf shrubs had little or no NRA. Deschampsia flexuosa is, however, a species which can be common in dwarf shrub types and which is capable of high NRA. In short herb types most species had low current NRA and reacted only slightly on induction. This was the case also for some species in tall herb types, while others had high current and maximally induced NRA. Soil analyses showed that the presence of plants with high current NRA coincided with low C/N ratio, high N concentration and relatively high pH. This was most clearly demonstrated along a sharp forest productivity gradient.