Advantages of rainfall partitioning by the global invader Ligustrum lucidum over the dominant native Lithraea molleoides in a dry forest

Vegetation canopy plays a key role in the local water balance by partitioning rainfall into interception, throughfall and stemflow in dry forests. Many invasive plants have the capacity to replace native species and alter the net amount and spatial distribution of rainfall reaching the soil. In this paper, we aimed to compare the rainfall partitioning for the invader Ligustrum lucidum and the dominant native Lithraea molleoides, to evaluate the influence of morphological characteristics on stemflow generation in both species, and to explore spatiotemporal patterns of throughfall at stand scale. Stemflow percentage for L. lucidum was hugely higher than for L. molleoides (18 and 1%, respectively), which overcompensated its lower throughfall percentage (58.1 and 68.6%, respectively). Interception losses were lower for L. lucidum than for L. molleoides (23.2 and 30.6%, respectively). The minimum rainfall amount needed to generate throughfall and stemflow was 1.8 and 0.5 mm for L. lucidum, while 2.2 and 7.2 mm for L. molleoides. The differences in morphological characteristics between species mainly explained the stemflow generation. The increment on tree basal area, projected canopy area, and number of branches favored stemflow in L. lucidum, but not in L. molleoides. The throughfall spatial patterns showed that the dripping from different canopy densities was homogenous in L. lucidum stands, whereas throughfall increase towards more opened-canopies in L. molleoides stands. Lateral inflows were registered from small-scale crown sections at both forest stands, but less frequent in L. lucidum stands. The time stability of throughfall pattern differed between forest stands. Based on our results, relatively higher stemflow and lower interception losses for L. lucidum than for L. Molleoides may represent a competitive advantage in terms of plant invasion in waterlimited ecosystems. These findings highlight the need for further inquiries determining the underlying role of rainfall partitioning in the invasion process of woody species.