Reproductive phenology of 233 species from four herbaceous-shrubby communities in the Gran Sabana Plateau of Venezuela

Abstract

Background and aims: Herbaceous-shrubby communities in the Gran Sabana (Great Savanna) Plateau of Venezuela grow under non-zonal conditions. We speculated that this would produce specific patterns of reproductive phenology within these different soil-climate-vegetation associations. Specifically, we tested the hypothesis that the reproductive phenology patterns of four herbaceous-shrubby communities are determined by climate, plant life-forms and soil properties.

Methodology: The reproductive phenology of 233 plant species of the Gran Sabana Plateau of the Venezuelan Guayana Highlands was studied taking into account their life-forms (i.e. trees, shrubs, climbers, annual herbs, perennial herbs, epiphytes and parasites/hemiparasites) in four herbaceous-shrubby communities: (i) shrubland, (ii) secondary bush, (iii) savanna and (iv) broad-leaved meadow. Patterns of flowering, and occurrence of unripe fruit and ripe fruit were studied at two levels of intensity for 24 months within a 5-year span. Two phenological records for each month of the year and between two and four replicates for each community type were made. Randomly selected 2-3 ha plots were used. General phenological patterns were established using <25% of the plants of each species in each plot to give the total duration of each phenological phase. High-intensity phenological patterns were established using >25% of individuals in each plot to establish times of high abundance of flowers, and presence of unripe fruit and/or ripe fruit on individual plants. This generated phenological peaks for each species.

Principal results: Non-seasonality of general flowering and unripe fruiting in each of the four communities was related to non-seasonal flowering and unripe fruiting patterns in the plant life-forms studied and to low variation in precipitation throughout the year. Flowering activity in the shrubland and broad-leaved meadow peaked twice. The bush community had only one flowering peak while the savanna gave a non-seasonal flowering peak. The peak unripe fruiting pattern was not clearly related to unripe fruit phenological patterns of the most abundant life-forms. Unripe fruit patterns and precipitation were only correlated for shrubs, climbers and trees in the shrubland. Ripe fruiting patterns peaked during the short-dry season in the bush and shrubland, and were negatively correlated with precipitation in the shrubland. General and peak ripe fruiting patterns were non-seasonal in the savanna and broad-leaved meadow and related to the dominance of herbaceous species with prolonged ripe fruiting times, low climate seasonality, high plant species richness and diversity, and dispersal syndromes.

Conclusions: The reproductive phenology of the herbaceous-shrubby communities is mainly influenced by the composition of the life-forms, the precipitation regime and soil type.

Fig. 1

Cluster analysis grouping the months of the year with respect to the frequency of plant species in flower and with unripe and ripe fruit.

Fig. 2

General phenological patterns of plant species according to their life-forms. (A) flowering, (B) fruiting and (C) ripe fruiting.

Fig. 3

Phenological patterns of life-forms. These are based on maximum values of flower (A), unripe fruit (B) and ripe fruit (C) production.

Fig. 4

General phenological patterns of plant species at the community level. (A) flowering, (B) fruiting and (C) ripe fruiting.

Fig. 5

Phenological patterns of communities. These are based on maximum values of flower (A), unripe fruit (B) and ripe fruit (C) production.