Abstract
Rainfall is known as the main water replenishment in dryland ecosystem, and rainfall partitioning by vegetation reshapes the spatial and temporal distribution patterns of rainwater entry into the soil. The dynamics of rainfall partitioning have been extensively studied at the inter-event scale, yet very few studies have explored its finer intra-event dynamics and the relating driving factors for shrubs. Here, we conducted a concurrent in-depth investigation of rainfall partitioning at inter- and intra-event scales for two typical xerophytic shrubs (Caragana korshinskii and Salix psammophila) in the Liudaogou catchment of the Loess Plateau, China. The event throughfall (TF), stemflow (SF), and interception loss (IC) and their temporal variations within the rainfall event as well as the meteorological factors and vegetation characteristics were systematically measured during the 2014–2015 rainy seasons. The C. korshinskii had significantly higher SF percentage (9.2 %) and lower IC percentage (21.4 %) compared to S. psammophila (3.8 % and 29.5 %, respectively) (p < 0.05), but their TF percentages were not significantly different (69.4 % vs. 66.7 %). At the intra-event scale, TF and SF of S. psammophila was initiated (0.1 vs. 0.3 h and 0.7 vs. 0.8 h) and peaked (1.8 vs. 2.0 h and 2.1 vs. 2.2 h) more quickly, and TF of S. psammophila lasted longer (5.2 vs. 4.8 h), delivered more intensely (4.3 vs. 3.8 mmâh−1), whereas SF of C. korshinskii lasted longer (4.6 vs. 4.1 h), delivered more intensely (753.8 vs. 471.2 mmâh−1). For both shrubs, rainfall amount was the most significant factor influencing inter-event rainfall partitioning, and rainfall intensity and duration controlled the intra-event TF and SF variables. The C. korshinskii with larger branch angle, more small branches and smaller canopy area, has an advantage to produce stemflow more efficiently over S. psammophila. The S. psammophila has lower canopy water storage capacity to generate and peak throughfall and stemflow earlier, and it has larger aboveground biomass and total canopy water storage of individual plant to produce higher interception loss compared to C. korshinskii. These findings contribute to the fine characterization of shrub-dominated eco-hydrological processes, and improve the accuracy of water balance estimation in dryland ecosystem.
Highlights
45 Rainfall is known as the main replenishment of water resources in arid and semi-arid areas, and water resource is the key factor limiting the function of arid ecosystems (Cayuela et al, 2018; Magliano et al, 2019a)
For C. korshinskii, TF represented the largest component of all rainfall events, while for S. psammophila, SF represented the smallest component of all rainfall events (Figs. 2 b and 2c)
4 Discussion 4.1 Rainfall partitioning and influencing factors at inter-event scale 375 This study indicated that SF% and interception loss (IC)% significantly differed between the two xerophytic shrub species in the Loess Plateau, northern China (Fig. 3)
Summary
45 Rainfall is known as the main replenishment of water resources in arid and semi-arid areas, and water resource is the key factor limiting the function of arid ecosystems (Cayuela et al, 2018; Magliano et al, 2019a). 50 Differences in the distribution of net rainfall caused by plant canopy interception alter the spatial and temporal patterns of rainfall entry into the soil (Martinez-Meza and Whitford, 1996; Li et al, 2009; Van Stan II et al, 2020; Tonello et al, 2021), and further profoundly affect the water use efficiency of vegetation and ecosystem sustainability (Lacombe et al, 2018; Molina et al, 2019). Net rainfall could regulate vegetation physiological 55 metabolic processes through nutrient enrichment (Levia and Frost, 2003; Van Stan II et al, 2017), affecting the carbon balance of ecosystems (Chu et al, 2018; Jia et al, 2016). Studies on rainfall partitioning have been broadly carried out in different climatic zones and various types of vegetation (Magliano et al, 2019a; Gordon et al 2020; Sadeghi et al 2020; Rivera and Van Stan II, 2020; Zhang et al, 2021b). The lack 70 of information on the detailed dynamics of rainfall partitioning processes induced by shrubs due to limited studies hinders us form a clear understanding of shrubs’ eco-hydrological role in shaping and sustaining drylands
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