CHESNEYA NUBIGENA ON A HIMALAYAN GLACIAL MORAINE - A CASE OF FACILITATION IN PRIMARY SUCCESSION

Facilitation during plant succession is predicted to be an important m echanism in extreme environments whereby facilitating species moderate the micro-habitat and allow colonization by secondary species. This p aper proposes two criteria for exploring facilitation. (1) Does the pr oposed facilitator modify the physical environment? (2) Does this modi fication enable colonization by later species? Failure to demonstrate either of these criteria is sufficient reason to reject the facilitati on hypothesis. Criterion 1 can be addressed in a brief field season, a nd determines whether the more detailed physiologic and fitness studie s of criterion 2 are warranted. These criteria can be used to allocate effort in extreme environments where research is difficult, and we ap ply them to evaluate possible facilitation by Chesneya nubigena on a g lacial moraine in the Nepal Himalaya. This study demonstrates that Che sneya moderates the physical environment (criterion 1) by forming soil , increasing organic composition, and by raising soil temperatures, pe rhaps providing a micro-habitat suitable for colonization by grasses a nd forbs. Physiological and fitness benefits conferred on the secondar y species (criterion 2) remain to be demonstrated.