Assessment of Phenology in Gmelina (Gmelina arborea Roxb.) Populations in Nigeria

Abstract

The phenological events of 68 reproductive mature Gmelina arborea trees were monitored at three different periods, every month along the year in Idemili South forests for two consecutive annual cycles. Leaf initiation started with the emergence of leaf buds in first March, coinciding with the transition between the end of dry season and the beginning of rainy season. Leaf flushing started mid-June and peaked later in June. The leafing duration lasted for approximately 5 months. Leaf fall phase started in December and ended in January. Flower initiation started in mid January and peaked in late February, concentrated in the dry months. The flowering duration lasted for approximately 1 month. Flowering intensity was slightly higher in 2018 in all the populations. Fruiting phenology proceeded from early to the end of March. Fruits were mature by the end of March immediately before early significant rains. Fruiting duration from initiation to fruit drop lasted for approximately 2.5 months. The time lag between leaf flushing and first visible flowers was approximately 4 months. Low average asynchrony index (A.I.) was recorded for leafing (A.I.: 0.23), flowering (A.I.: 0.22), and fruiting (A.I.: 0.19) events among the populations. The results of this study have provided some information on aspects of the reproductive biology of the species for breeding and biodiversity conservation purposes. Since the phenophases are periodic and follow weather patterns, probable climate change will have serious implications on future reproductive success of G. arborea. In view of this, multiannual quantitative documentation of phenological patterns in the species is recommended to quantify the levels of variance, and thus trace the impacts of climate changes on the vegetation of the area.