Interception, throughfall and stemflow partition in drylands: Global synthesis and meta-analysis

Abstract

The net amount of rainfall entering into the soil and its spatial distribution at the patch scale are key drivers of ecosystem processes in drylands. The spatial distribution of water is mainly controlled by vegetation canopy which determines the partitioning of rainfall into interception, throughfall and stemflow. In this paper, we synthesized and analyzed rainfall partitioning for 68 woody plant species in drylands (delimited by a rainfall-potential evapotranspiration ratio <0.65; 46 papers). We explored the role of rainfall inputs and plant morphological attributes (life form, phenology, leaf type and bark type) by considering a rainfall gradient from 145 to 805 mm year^−1. On average, interception, throughfall and stemflow accounted for 24.0, 69.8 and 6.2% of total rainfall, respectively. Stemflow was the most variable flux (coefficient of variation = 107.8%), while interception and throughfall were less variable fluxes (coefficient of variation = 39.2 and 20.4%, respectively). Along the increasing rainfall gradient, interception showed a tendency to decrease from 27.1 to 18.9% (p = 0.12), throughfall increased from 61.4 to 81.2% (p < 0.01) and stemflow decreased from 10.0 to 1.6% (p < 0.0001). Shrubs presented higher stemflow than trees (9.4% vs. 3.5%, respectively; p < 0.0001), while trees presented higher throughfall than shrubs (72.3% vs. 63.0%, respectively; p < 0.05). Species with smooth barks presented higher stemflow than species with rough barks (8.3% vs. 4.2%, respectively; p < 0.0001). Both phenology and leaf type had no effect on interception, throughfall and stemflow (p > 0.05 for all cases). Shrubs were more abundant towards the dry edge of the rainfall gradient (145-500 mm year^−1), while trees were more abundant towards the subhumid edge (500-805 mm year^−1). These results suggested that higher stemflow found towards the dry edge of the rainfall gradient was caused by the higher abundance of shrubs, which generated more stemflow than trees. Our findings highlighted the ecohydrological key role of vegetation life form and rainfall inputs affecting the amount of water entering into the soil and its spatial distribution in drylands.