Safe site for seedlings of <i>Rhododendron metternichii</i> var. <i>hondoense</i>

Abstract

Abstract Safe sites for seedlings of Rhododendron metternichii Sieb. et Zucc. var. hondoense Nakai (Ericaceae) were determined in the field in Japan. Microhabitats were classified by overlaying a distribution map of ground conditions (moss and rock patches) with crown projection diagrams. Seedlings of R. metternichii var. hondoense were highly dependent on ground conditions; seedling density was extremely low on soil but high on moss mats. Considering the canopy condition, seedling density on soil and rock was significantly lower at open sites than under tree crowns. In contrast, seedling density on moss mats was high at open sites, especially under deciduous trees. Moss–deciduous trees or moss–open sites were the best microhabitats as they usually provided both water and sunlight for seedlings. Of seedlings 0–2 cm in height, 87.7% were on moss mats while only 2.7% were on soil. This proportion of seedlings on moss and soil gradually changed with seedling development. Only 6.1% of the seedlings over 10 cm in height were on moss mats, while 81.8% were found on soil: this apparently was due to changes in ground conditions. The change from moss to soil occurred more frequently than a change from soil to moss during a 2‐year observation period. Although early seedling establishment of R. metternichii var. hondoense is highly dependent on moss mats, seedlings seem to gain tolerance for drought and instability of the substrate as they grow and they continue to survive after the disappearance of moss mats.