Temporally dependent effects of rainfall characteristics on inter- and intra-event branch-scale stemflow variability in two xerophytic shrubs

Abstract

Abstract. Stemflow is important for recharging root-zone soil moisture in arid regions. Previous studies have generally focused on stemflow volume, efficiency and influential factors but have failed to depict stemflow processes and quantify their relations with rainfall characteristics within events, particularly for xerophytic shrubs. Here, we measured the stemflow volume, intensity, funneling ratio and time lags to rain at two dominant shrub species (Caragana korshinskii and Salix psammophila) and rainfall characteristics during 54 events at the semiarid Liudaogou catchment of the Loess Plateau, China, during the 2014–2015 rainy seasons. The funneling ratio was calculated as the ratio between stemflow and rainfall intensities at the inter- and intra-event scales. Our results indicated that the stemflow of C. korshinskii and S. psammophila, on average, started at 66.2 and 54.8 min, maximized 109.4 and 120.5 min after rain began, and ended 20.0 and 13.5 min after rain ceased. The two shrubs had shorter stemflow duration (3.8 and 3.4 h) and significantly larger stemflow intensities (517.5 and 367.3 mm h−1) than those of rain (4.7 h and 4.5 mm h−1). As branch size increased, both species shared the decreasing funneling ratios (97.7–163.7 and 44.2–212.0) and stemflow intensities (333.8–716.2 and 197.2–738.7 mm h−1). Tested by the multiple correspondence analysis and stepwise regression, rainfall amount and duration controlled stemflow volume and duration, respectively, at the event scale by linear relations (p < 0.01). Rainfall intensity and raindrop momentum controlled stemflow intensity and time lags to rain for both species within the event by linear or power relationships (p < 0.01). Rainfall intensity was the key factor affecting stemflow process of C. korshinskii, whereas raindrop momentum had the greatest influence on stemflow process of S. psammophila. Therefore, rainfall characteristics had temporally dependent influences on corresponding stemflow variables, and the influence also depended on specific species.

Exploring the stemflow dynamics and driving factors at both inter‐ and intra‐event scales in a typical subtropical deciduous forest

“…Our high temporal resolution data of stemflow could provide conditions to examine the timing of stemflow within rainfall events. Stemflow synchronized well with rainfall under rainfall type A and B (Figure 7), which was consistent with previous observations (Levia et al, 2010; Yuan et al, 2019). In particular, the peaks of both F i and R i were highly synchronized.…”

“…Stemflow synchronized well with rainfall under rainfall type A and B (Figure 7), which was consistent with previous observations (Levia et al, 2010;Yuan et al, 2019). In particular, the peaks of both F i and R i were highly synchronized.…”

“…Previous studies also report that L S show large differences between different tree species such as arborescent babassu palms with 15 min (Germer et al, 2010), S. psammophila with 54.8 min (Yuan et al, 2019), pine trees with 1 h and oak trees with 1.5 h (Carlyle- Moses et al, 2018). L S values of B. papyrifera and Q. acutissima in our forest also fall within the above-mentioned variation range, except for the L S under low-intensity, long-duration rainfall type for Q. acutissima with 4.1 h and B. papyrifera with 3.2 h (Figure 9a).…”

“…Thus, to better understand the stemflow dynamics and its importance to forest hydrological processes, high temporal resolution data are required (Levia & Germer, 2015). Such data can provide insights into the short‐intensity burst and temporal fluctuations of stemflow (Dunkerley, 2019; Yuan et al, 2019), which permits in‐depth interpretation of the effects of “hot spots” and “hot moments” on many hydrological processes (McClain et al, 2003). Furthermore, the lag time between stemflow and rainfall can also be captured by high temporal resolution data.…”

“…5‐min data capture the phenomenon that stemflow may continue to drain for up to 48 h after the cessation of rainfall in a temperate redwood forest (Reid & Lewis, 2009). Thus, lag time is an effective parameter to understand temporal dynamics of stemflow (Yuan et al, 2019). However, studies reporting quantitative assessments on lag time and the relationship between lag time and rainfall characteristics (e.g., rainfall types) for different tree species are quite limited (Cayuela et al, 2018; Germer et al, 2010).…”