Facultad de Ciencias , Instituto de Biología Experimental , Centro Botánica Tropical , Universidad Central de Venezuela , Aptdo. 48312, Caracas 1041A , Venezuela.
AoB Plants. 2011;2011:plr014. doi: 10.1093/aobpla/plr014. Epub 2011 May 25.
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.
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.
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.
The reproductive phenology of the herbaceous-shrubby communities is mainly influenced by the composition of the life-forms, the precipitation regime and soil type.
委内瑞拉格兰萨巴纳高原（大萨凡纳高原）的草本-灌木群落生长在非地带性条件下。我们推测，这将在这些不同的土壤-气候-植被组合中产生特定的生殖物候模式。具体来说，我们检验了以下假设：四个草本-灌木群落的生殖物候模式是由气候、植物生活型和土壤特性决定的。
考虑到委内瑞拉圭亚那高地格兰萨巴纳高原的四个草本-灌木群落（即：灌丛、次生灌丛、稀树草原和阔叶草地）中植物物种的生活型（即：乔木、灌木、藤本植物、一年生草本植物、多年生草本植物、附生植物和寄生/半寄生植物），研究了 233 种植物的生殖物候。在 5 年的时间跨度内，以 24 个月为一个周期，对每个月的开花情况以及未成熟果实和成熟果实的出现情况进行了两次强度的研究。每个群落类型进行了两次记录。使用了随机选择的 2-3 公顷的样地。使用每个物种每个样地的<25%的植物来确定每个物候阶段的总持续时间，以建立一般物候模式。使用每个样地的个体>25%来建立高强度物候模式，以确定个体植物上花的高丰度、未成熟果实和/或成熟果实的出现时间。这为每个物种生成了物候峰。
四个群落中一般开花和未成熟果实的非季节性与所研究植物生活型的非季节性开花和未成熟果实模式以及全年降水变化较小有关。灌丛和阔叶草地的开花活动出现了两次高峰。灌木群落只有一个开花高峰，而稀树草原则出现了非季节性的开花高峰。未成熟果实模式与最丰富的生活型的未成熟果实物候模式没有明显的关系。在灌丛中，只有灌木、藤本植物和乔木的未成熟果实模式与降水有关。在灌木和灌丛中，成熟果实模式的高峰出现在短暂的旱季，与灌丛中的降水呈负相关。稀树草原和阔叶草地的一般和高峰成熟果实模式是非季节性的，与具有延长成熟果实时间、低气候季节性、高植物物种丰富度和多样性以及扩散综合征的草本物种的优势有关。
草本-灌木群落的生殖物候主要受生活型组成、降水格局和土壤类型的影响。
