The architecture and nutrient-use traits of dwarf Alnus japonica in the Kushiro Mire, northern Japan

Abstract

We investigated the stem architecture, leaf dynamics and nutrient-use traits of N_2-fixing Alnus japonica (Thunb.) Steud. at three sites with different stem height in a dwarf alder patch, concurrently established in the Kushiro Mire, northern Japan. Total dissolved phosphorus in the soil water was abundant in the H-site with ca. 3m stems in height, in which the clone density was the lowest. In this site the leaf longevity was significantly longer among the sites, though there was no difference in the cumulative number of leaves expanded per current shoot with the other sites. While the mean residence time of phosphorus was the longest in the H-site probably due to the longer leaf longevity, the phosphorus use efficiency was the highest in the L-site with ca. 1m stems, indicating that the productivity is not so low irrespective of less phosphorus content in the leaves. We estimated that excess resorption of phosphorus from the senescent leaves induced by destitution in the phosphorus resource would shorten the leaf longevity, probably because an inherited constraint prevents to reduce flexibly the total number of leaves expanding per current shoots. Plasticity in the phosphorus-use traits according to its availability of the habitat may partly enable to establish N_2-fixing alder forests broadly in the mire with various shoot architecture.