Integrated Predictive Modeling of Nectar Volume and Concentration of Croton macrostachyus Across Canopy Levels, Ontogeny and Environmental Variation in Sidama, Hawassa University, Ethiopia
Year: 2026
Type: preprint
Abstract: Introduction : Nectar secretion plays a crucial role in honey production, but the effects of canopy strata, tree age, and environmental factors on nectar availability remain unclear. This study quantifies these effects in Sidama and Hawassa, Ethiopia, and develops predictive models. Previous research on Callistemon citrinus L. showed that younger plants do not respond to relative humidity or temperature in terms of nectar volume, while medium-aged and older plants do. Additionally, studies on Croton macrostachyus Hochst. ex Delile and Trifolium repens . indicate that temperature, humidity, daylight, canopy layers, tree age, and soil moisture influence nectar volume and concentration. Methods A factorial design (6 × 3) was used to assess nectar solute concentration (%) and volume (µL) across six canopy layers (AL1–AL3, ML1–ML3) and three tree age classes (small, medium, older). Bivariate and multiple linear regression (MLR) models were applied to develop forecasting tools for nectar yield and to evaluate climate-induced thermal stress. Results Analysis of variance showed a significant interaction between canopy layer and tree age for solute concentration (p < 0.001), with older trees in the upper canopy (AL3) reaching the highest concentration (36.42 ± 0.10%). Nectar volume decreased significantly with tree age (p < 0.001) across all canopy positions. The bivariate model (Volume = 0.8456 − 0.0189 × Concentration; R² = 0.620) indicated a clear trade-off between sugar concentration and fluid availability. Conclusions Model projections for 2076 suggest a potential “Viscosity Trap,” where a + 2.0°C temperature increase could raise concentrations above 42.8% and reduce volumes below 0.10 µL. These findings highlight older trees as high-solute hotspots and lower canopy layers as thermal refuges. Maintaining multi-layered canopy structures is essential for sustaining honeybee foraging efficiency and enhancing apiculture resilience under climate change.
Source: Research Square
Authors: kasim Jilo, Muzeyin Berarti
Institution: Arsi University
Language: English
Subfield: Insect Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W7165575072