Differences in interception storage capacities of undecomposed broad-leaf and needle-leaf litter under simulated rainfall conditions

Abstract

Leaf litter is an important component of agroforestry ecosystems that plays a key role in soil and water conservation. This study assessed the effect of leaf shape on water interception under controlled laboratory conditions. Two contrasting leaf shapes (needle-leaf, represented by Pinus massoniana; and broad-leaf, represented by Magnolia grandiflora) were placed in a steel box (2 m long and 1 m wide) for separate experiments with different leaf masses per ground area (0.5, 1.0 and 1.5 kg/m2); the steel box was positioned on two different slopes (5° and 20°) corresponding to gentle and steep slopes; the rainfall intensity was 90 mm/h. The results indicated that leaf shapes had specific effects on the interception storage capacity of the leaf litter on a slope. The needle-leaf litter intercepted 2.08 times more rainwater than the broad-leaf litter on average. As the leaf mass increased, the interception storage capacity of the leaf litter successively increased for the needle-leaf litter, while there were no obvious patterns for the broad-leaf litter. This difference occurred because the initially erect broad leaves were easily flattened by raindrop impacts due to their large surface areas and hence formed a horizontal leaf cover (or leaf overlap). This leaf accumulation structure restricted the infiltration of rainwater into the lower leaf litter while providing a short path for rainwater to leave the leaf litter, hence promoting litter flow and leading to less rainwater intercepted by the broad-leaf litter than the needle-leaf litter. Our results provide a better understanding of the effects of leaf shape on leaf litter interception on inclined slopes, which is lacking in the current literature.