Distinct altitudinal trends in the wood structure of Rhododendron arboreum (Ericaceae) in Nepal.

摘要

Altitudinal trends in the wood structure of Rhododendron arboreum Sm. (Ericaceae) were studied in two areas of Nepal, Rolwaling in the central and Bajhang-Khaptad in the far western regions. In the Rolwaling area Rhododendron arboreum grew throughout the altitudinal range of this species in Nepal from 1200 to 3500 m, but, in the Bajhang-Khaptad area, it grew only above 2000 m due to the lack of enough precipitation below this altitude. In both areas stem diameter or plant height did not have any significant correlation with wood anatomical features, but altitude had significant correlations with vessel element and fibre lengths and several features of multiseriate rays. Comparison with previously reported materials collected throughout Nepal showed that features of multiseriate rays have more distinct correlations than other features, occasionally with plant size, but mostly with altitude. Ecological implications of altitudinal trends in multiseriate rays are discussed in relation to climatic gradients and transport of signal or minerals, but no clear explanation could be found.