© 1996 Heron Publishing—Victoria, Canada
Response of two Afromontane coniferous tree species to light and nutrient supply
Hailu Sharew, John Grace and Colin J. Legg
Institute of Ecology and Resource Management, Division of Biological Sciences, The University of Edinburgh, Darwin Building,
Mayfield Road, Edinburgh, EH9 3JU, U.K. / Received June 28, 1995
Summary
We studied the responses to light and nutrient availability of the two Afromontane conifers Juniperus procera Hochst. ex Endl., reputedly a shade-intolerant species, and Afrocarpus gracilior Polger C.N. Page, a shade-tolerant species. The species behaved similarly in response to light and nutrient availability.
Both species showed positive growth rates at photon fluxes of 0.6–0.8 mol m–2 day–1. Maximum relative growth rates of 0.15 week–1 were attained at an irradiance of 8 mol m–2 day–1 in the high-nutrient supply treatment. The growth response to high-nutrient supply was achieved by an increase in leaf area
ratio rather than by an increase in net assimilation rate.
In a 10-week growth experiment, both species displayed an increase in stem extension rate in response to a low red/far-red
ratio (0.09) at low irradiance, and A. gracilior also responded by increasing its specific leaf area. Similiar findings were observed in a short-term experiment in which
internodes were laterally irradiated.
Keywords:
Afrocarpus gracilior, Afromontane coniferous forest, climax species, Ethiopia, forest understory, Juniperus procera, pioneer species, photosynthetic photon flux, red/far-red ratio, seedling establishment.
