Germination rate of endangered cloud forest trees in Mexico: potential for ex situ propagation

Abstract

ABSTRACTDeforestation and elimination of reproductive adult trees in Mexican tropical montane cloud forest (TMCF), due to traditional selective logging, threaten the maintenance of more than half of the tree species in this ecosystem. The objective of this study was to evaluate germination in threatened TMCF tree species in order to assess their propagation potential for conservation efforts. Given that seed size is an important trait influencing germination, the relationship between seed size and mean time to germination (MTG) was evaluated. Seeds of 10 valuable TMCF tree species were sown in a controlled environment and germination rates were recorded until reaching their maximum value. All species displayed potential for propagation from seed without pre-germination treatments. Final germination percentages were as follows: Fraxinus uhdeii = 36.3 ± 7.4% (mean ± 1 SE), Juglans pyriformis = 50.6 ± 6.5%, Magnolia vovidesii = 90.8 ± 1.1%, Meliosma alba = 68.4 ± 6.8%, Ocotea disjuncta = 64.1 ± 12.9%, Oreomunnea mexicana = 17.8 ± 4.4%, Quercus germana = 18.1 ± 1.9%, Sideroxylon contrerasii = 27.1 ± 12.6%, Ulmus mexicana = 33.6 ± 3.7%, and Zanthoxylum melanostictum = 12.7 ± 2.2%. Time required to reach maximum germination varied widely among species; from 49 days in F. uhdei to 434 days in S. contrerasii. No significant correlation was found between seed mass and MTG. While ex situ germination is an important aspect of propagation to reinforce populations of these species, further assessment of germination and transplanted seedling survival under varied TMCF conditions is required.