A Study of the Autecology of Polygonum Affine D. Don in the Karakoram Mountains

At high altitudes in the Karakoram Mountains of West Pakistan, the development of vegetation is strongly influenced by the grazing of flocks of sheep and goats. In the Salix-Betula scrub zone (at approximately 3700 m in the area studied) the woody species do not survive grazing and the scrub is replaced by herbaceous communities. Polygonum affine D. Don is a rhizomatous herbaceous perennial which is abundant in some of these communities but is rare or absent from others. As it is highly unpalatable it is not directly subject to grazing as a limiting factor, and its local distribution has been studied in order to characterize some of its ecological requirements. P. affine grows abundantly in communities of well-drained habitats, with coarse porous soils, often on steeply sloping ground. These communities have also a relatively long growing season and the species is absent from communities which are known to be subjected to standing water during the spring thaw and from areas where the snow lies until late in the year. It grows poorly in areas with fine textured, permanently moist soils and in ungrazed communities, in which it is shaded by taller species.