Trait-based analysis of rainfall partitioning in tropical shrubs: a comparative study of Cordyline sp. and Heliconia sp.

This study investigates the rainfall interception dynamics of two morphologically distinct tropical shrub species, Heliconia sp. and Cordyline sp., in a coastal equatorial region of Malaysia. With increasing recognition of shrubs in urban hydrology and ecological landscaping, the research aims to quantify how structural traits influence interception, throughfall, and stemflow. A 30-day field experiment was conducted involving replicated measurements of rainfall partitioning under controlled monitoring of gross precipitation, throughfall, and stemflow. Results reveal that Cordyline sp., characterized by taller stature, linear leaves, and rough, channeled stems, exhibited significantly higher interception losses (8.96–35.14%) and stemflow (0.64–1.21%), whereas Heliconia sp., with shorter height and broader, smooth-leaved canopies, allowed more throughfall (0.91–33.37 mm) and exhibited lower interception (5.30– 7.67%). Interception losses were particularly pronounced under low rainfall (<10 mm), where over 95% interception was recorded in certain instances, especially for dense Cordyline canopies. Regression analyses identified canopy coverage and shrub height as significant structural factors influencing interception partitioning. These findings underscore the need to integrate species-specific shrub traits into urban water management and ecological planning strategies.