Significance of phenologically asynchronous populations of the central Himalayan oaks in drought adaptation

In this paper we describe asynchrony in leaf production of the two major ce ntral Himalayan oaks (Quercus floribunda and Q. leucotrichophora) with majo r focus on their adaptational significance to an unusually severe drought o f 1999. In each oak, early and late leafing populations were differentiable and individuals of such types could occur adjacently. However, by and larg e, they tend to occupy different microsites, early leafing concentrating on moist microsites and late leafing on drier ones. Analysis of association b etween the two populations within each oak indicated that there was no sign ificant association in distribution. The study provides some direct evidenc e of adaptational significance of having asynchronous populations. The capa city of the late leafing population of Q. floribunda to employ high osmotic adjustment during the drought, and protecting buds even when leaves were d ry and dead enabled them to survive the severe drought of 1999.