Vegetative and reproductive biomass allocation responses of herbaceous plant species to induced drought in a semi–arid highland savanna, central, Namibia
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Date
2024
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University of Namibia
Abstract
Namibia's arid conditions renders its vegetation vulnerable to changes in precipitation,
affecting plant growth and biomass allocation. Recurring droughts, intensified by climate
change lead to alterations in biomass allocation. Thus resulting in the reduction of
medicinal products, livestock fodder, and food sources while disrupting nutrient cycles.
This study investigated herbaceous drought responses in biomass allocation and the
influence of environmental variables on these patterns, aiming to inform ecosystem
management to conserve Namibia's biodiversity. Twenty fixed rainout shelters (4 m x 4
m) were used at Neudamm Agricultural Farm to simulate drought conditions with four
treatments (0%, 20%, 40%, and 80% rainfall reduction), each replicated five times.
Environmental parameters, including temperature (measured with a mercury
thermometer), soil moisture content and chlorophyll content (using a SPAD-502 Plus
Chlorophyll meter) were recorded before biomass harvesting. Biomass was collected from
0.5 m x 0.5 m quadrants, with aboveground biomass clipped at ground level and
belowground biomass obtained through soil excavation. The Generalized Linear Models
indicate that drought treatments are significant predictors of reproductive biomass
allocation (χ²(3) = 13.114, p < 0.004), while temperature significantly influences
vegetative biomass allocation (χ²(1) = 17.103, p < 0.004). The Friedman test results show
a significant difference in chlorophyll content across drought treatments (χ² = 18.456, df
= 1, p < 0.001), with Aptosimum lineare and Ocimum americanum exhibiting the highest
chlorophyll levels under treatment 60 highlighting the resilience of these species in arid
savannas. These findings underscore the significant impact of drought on biomass
allocation and the need for targeted interventions to mitigate its effects on plant growth
and development
Description
A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science in Biodiversity Management
Keywords
Climate change, Drought, Rainout shelters, Herbaceous plants, Namibia, University of Namibia