Biocrust-induced partitioning of soil water between grass and shrub in a desert steppe of Northwest China

Abstract

Maintaining the stability of exotic sand-binding shrub has become a large challenge in arid and semi-arid grassland ecosystems in northern China. We investigated two kinds of shrublands with different BSCs (biological soil crusts) cover in desert steppe in Northwest China to characterize the water sources of shrub (Caragana intermedia Kuang et H. C. Fu) and grass (Artemisia scoparia Waldst. et Kit.) by stable 18 O isotopic. Our results showed that both shrublands were subject to persistent soil water deficiency from 2012 to 2017, the minimum soil depth with CV (coefficient of variation) <15% and SWC (soil water content) <6% was 1.4 m in shrubland with open areas lacking obvious BSC cover, and 0.8 m in shrubland covered by mature BSCs. For C. intermedia, a considerable proportion of water sources pointed to the surface soil. Water from BSCs contributed to averages 22.9% and 17.6% of the total for C. intermedia and A. scoparia, respectively. C. intermedia might use more water from BSCs in rainy season than dry season, in contrast to A. scoparia. The relationship between shrub (or grass) and soil water by δ 18 O shown significant differences in months, which partly verified the potential trends and relations covered by the high variability of the water source at seasonal scale. More fine roots at 0-5 cm soil layer could be found in the surface soil layer covered by BSCs (8000 cm/m 3 ) than without BSCs (3200 cm/m 3 ), which ensured the possibility of using the surface soil water by C. intermedia. The result implies that even under serious soil water deficiency, C. intermedia can use the surface soil water, leading to the coexistence between C. intermedia and A. scoparia. Different with the result from BSCs in desert areas, the natural withdrawal of artificial C. intermedia from desert steppe will be a long-term process, and the highly competitive relationship between shrubs and grasses also determines that its habitat will be maintained in serious drought state for a long time.

Evaluation of Water Balance and Water Use Efficiency with the Development of Water-Saving Irrigation in the Yanqi Basin Irrigation District of China

“…Quantitative assessment of the soil-atmosphere transformation processes using remotely sensed data provides a better understanding of the relationship between crop growth and water resource management [12]. The effectiveness of spatiotemporal engineering of land surface evapotranspiration and irrigation water consumption in the Yanqi Basin at the farmland scale was evaluated using MODIS remote sensing data and HTEM (hybrid dual-source scheme and trapezoid framework-based evapotranspiration model) [13] modeling of this region [14]. In that study, remote sensing was used to identify the area of arable land [15], compensating for the limitations of statistical data that can only be counted at the county and city levels, as well as the problem of data accuracy, making the results more rapid and accurate.…”