Stemflow in two xerophytic shrubs and its significance to soil water and nutrient enrichment

Abstract

Shrub canopies are expected to funnel substantial amounts of intercepted rainwater with enriched nutrients as stemflow to shrub base in the desert ecosystems characterized by limited water and nutrients. However, lacking are quantitative studies on the water and nutrient enrichment of stemflow at the shrub basal area. In this study, stemflow were quantified for two xerophytic shrubs (Caragana korshinskii and Artemisia ordosica) in a revegetated desert ecosystem of Shapotou area in northwestern China. We also measured the ion concentrations of total nitrogen (TN), total phosphors (TP), NH4+–N, NO3−–N, Na+, K+, Ca2+, Mg2+, Cl−, SO42− and the pH and electric conductivity (EC) in stemflow, throughfall and bulk precipitation. Results indicated that stemflow accounted for 8.8 and 2.8 % of the gross rainfall for C. korshinskii and A. ordosica, respectively. Individual stemflow linearly increased with increasing rainfall depth. Stemflow increased with rainfall intensity when rainfall intensity was less than 2 mm h−1 but showed decreased tendency thereafter. An antecedent precipitation of 1.3 and 1.6 mm was necessary for stemflow initiation for C. korshinskii and A. ordosica, respectively. The mean (confidence intervals, α = 0.05) funneling ratio was 82 (17) for C. korshinskii and 26 (7) for A. ordosica. Ion concentrations in stemflow were higher than in throughfall, and the concentration of most of the ions measured were significantly higher (p < 0.05) in stemflow than in bulk precipitation, with a nutrient enrichment ratio ranged 122.8–1677.0 for C. korshinskii and 12.6–1306.0 for A. ordosica among measured ions, respectively. Overall, the larger funneling ratios and enrichment ratios for the two shrubs suggest that stemflow plays a significant positive role in soil water replenishment and nutrient enrichment at deeper soil profile of root zone in the revegetated ecosystems under arid desert conditions.

The effects of stemflow on redistributing precipitation and infiltration around shrubs

“…This threshold is consistent with the values reported by previous studies about shrubs in arid and semiarid regions (Enright, 1987;Martinez-Meza and Whitford, 1996;Li et al, 2008;Wang et al, 2013). The studies of Wang et al (2011b) and Zhang et al (2013) were based on one year experiment data in the Tengger Desert which reported that an antecedent precipitation of 2.2 and 1.3 mm was necessary for stemflow initiation for C. korshinskii. Our result (0.5 mm) was less than the above studies, this may be due to the different amount of data, different rainfall characteristics and environmental conditions.…”

“…Wang et al (2011a) found that stemflow water of C. korshinskii can reach a soil depth of 90 cm in Tengger Desert, it is favourable for the infiltrated water redistribution in the deeper soil profile of the root zone. Also, Zhang et al (2013) agreed to the findings, he thought infiltration of stemflow alongside stems into deep soil profiles, creating islands of soil moisture, can be an important potential source of soil moisture allowing shrubs to remain physiologically active during drought spells. Návar and Bryan (1990) found that stemflow transported into the soil area close to the shrub stems showed a water input that was five times higher than by other areas beneath the shrub canopies in northeastern Mexico.…”

“…The infiltration process is controlled by several biophysical factors, including ground cover, soil type, hydraulic properties, rainfall characteristics (such as rainfall amount, intensity and duration), meteorological conditions, seasonality and shrub canopy structure and soil surface features (Laio et al, 2001;Zhang et al, 2013). The wetting fronts of the area outside the canopy reached a depth of 5 cm more quickly than that around stem because most of the initial rainfall was intercepted by the canopy without producing stemflow for C. korshinskii and H. rhamnoides.…”

“…They are widely used for ecological restoration (Wei et al, 2007;Zhang et al, 2009). The effects of both rainfall and soil surface characteristics on soil water replenishment in re-vegetated ecosystems have been studied (Wang et al, 2011b;Wang et al, 2013;Zhang et al, 2013). However, the previous studies were mainly based on one year experiment data, the results obtained had occasionality.…”

Partición de la precipitación en un bosque tropical montano de pino-encino en el centro de México

“…El efecto de concentración de humedad del suelo asociado a la escorrentía cortical ha sido reportado en vegetación arbustiva (Zhang et al 2013) y en vegetación arbórea (Ladekarl 1998) y se ha postulado que la escorrentía cortical que ingresa al suelo alrededor de la base de un árbol es un mecanismo importante de resistencia a la sequía (Martinez-Meza y Whitford 1996). Guan et al (2010) demostraron que en suelos arcillosos y bajo ciertas condiciones, la presencia de raíces de árboles favorece la recarga del suelo y los mantos freáticos, posibilitando una percolación hasta del 20 % de la precipitación anual, mientras que sin presencia de este tipo de vías preferenciales de infiltración la percolación es < 1 %.…”