干旱区生态环境知识资源中心

Revegetation in arid desert ecosystems is emerging as a practical strategy to cease sand dune encroachment and combat desertification worldwide. The revegetation is expected to affect the spatial distribution of rainfall to the ground within vegetation communities. However, the impact of revegetation on the temporal distribution of dry and/or wet dust fall trapped by shrub canopies via stemflow and throughfall remains a topic of concern for shrub "fertile islands." This study investigated whether xerophytic shrub community acts as a sink of various cations (Na+, K+, Ca2+, and Mg2+), inorganic anions (Cl- and SO42-), total nitrogen, and total phosphorus to the revegetated desert ecosystems. Gross rainfall, the stemflow, and throughfall of two codominated xerophytic shrubs (Caragana korshinskii and Artemisia ordosica) were volumetrically measured after natural rainfall events, and their samples were chemically analyzed in the laboratory. Results showed that ions had higher concentrations in stemflow than in throughfall, followed by gross rainfall. Ion concentrations in stemflow and throughfall strongly depends on the first flush effect, rainfall depth, and the antecedent dry period before a rainfall event occurring. Concentrations of most of the ions in stemflow and throughfall collected after the first rainfall event of a year were obviously higher than other rainfall events for both shrub species, suggesting a first flush effect. Ion concentrations generally decreased with the increasing depth of gross rainfall, stemflow, and throughfall, while increased with prolonged antecedent dry period. Based on nutrient input by stemflow and throughfall at the community scale, we conclude that chemical enrichment of stemflow and throughfall plays an important role in forming the shrub fertile islands and contributes significantly to a sustainable succession of the revegetated desert ecosystems.