Seed germination and seedling establishment of Neotropical dry forest species in response to temperature and light conditions.

摘要

A study was conducted to examine the germination requirements of Cedrela odorata, Guaiacum sanctum and Calycophyllum candidissimum seeds, and the effect of light intensity on the survival and growth of C. odorata and G. sanctum seedlings planted on open, partially-open and beneath the canopy of a dry forest in Nicaragua. The results show that germination of Calycophyllum candidissimum seeds was significantly higher in light than darkness at constant temperatures ranging from 20-35 degrees C. Both Cedrela odorata and G. sanctum seeds germinated in light and darkness to a varying extent, and the optimal germination temperature was approximately 20-25 degrees C. Alternating temperature regimes did not improve germination. Survival of G. sanctum seedlings was 70% beneath the canopy and 80% in the open, and its relative growth rate in collar diameter was 1.88 mm/month in the open and 1.42 mm/month in the understorey. Survival was generally poor for Cedrela odorata, particularly in the understorey. We concluded that light is an absolute requirement for the germination of Calycophyllum candidissimum seeds while germination of Cedrela odorata and G. sanctum seeds are more sensitive to temperature. Owing to its high survival rate on open site, G. sanctum could serve as a candidate species for reforestation of degraded sites.