Nitrogen resorption efficiency of 13 tree species of a cool temperate deciduous forest in Central Japan

Abstract

The nitrogen (N) concentration of green and senescent leaves, and the N resorption efficiency of 13 dominant species from three distribution patterns along a slope (Ridge, Valley, and Uniform types) and two types of leaf emergence pattern (determinate and indeterminate flush types) were examined in a cool temperate natural forest in central Japan. Ridge species tended to have lower N concentrations of green and senescent leaves and higher N resorption efficiency than those of Valley species, and those of Uniform species were intermediate to other types with some exceptions. Furthermore, indeterminate flush species tended to have higher N concentrations in green and senescent leaves and lower N resorption efficiency than those of the determinate type. The N concentration of senescent leaves, which is an index of leaf-level N use efficiency (NUE), was significantly correlated with N concentrations in green leaves and with N resorption efficiency. The concentration in green leaves was not correlated with N resorption efficiency, suggesting that interspecific variation in the N concentration was not a major determinate of the N resorption efficiency at this study site. Rather N resorption efficiency was positively correlated with the start date of leaf fall, suggesting that early leaf fall species, which tended to have intermediate leaf flush types (with some exceptions), were not proficient in N resorption. Thus, the patterns in NUE and N resorption efficiencies were affected not only by the distribution pattern along the slope but also by leaf phenology in this cool temperate deciduous forest.