Search

Climate change is a significant force influencing catchment hydrological processes, such as baseflow, i.e., the contribution of delayed pathways to streamflow in drought periods and is associated with catchment drought propagation. The Weihe River Basin is a typical arid and semi-arid catchment on the Loess Plateau in northwest China. Baseflow plays a fundamental role in the provision of water and environmental functions at the catchment scale. However, the baseflow variability in the projected climate change is not well understood. In this study, forcing meteorological data were derived from two climate scenarios (RCP4.5 and RCP8.5) of three representative general circulation models (CSIRO-Mk3-6-0, MIROC5, and FGOALSg2) in CMIP5 and then were used as inputs in the Soil and Water Assessment Tool (SWAT) hydrological model to simulate future streamflow. Finally, a well-revised baseflow separation method was implemented to estimate the baseflow to investigate long-term (historical (1960–2012) and future (2010–2054) periods) baseflow variability patterns. We found (1) that baseflow showed a decreasing trend in some simulations of future climatic conditions but not in all scenarios (p < 0.05), (2) that the contribution of baseflow to streamflow (i.e., baseflow index) amounted to approximately 45%, with a slightly increasing trend (p ≤ 0.001), and (3) an increased frequency of severe hydrological drought events in the future (2041–2053) due to baseflows much lower than current annual averages. This study benefits the scientific management of water resources in regional development and provides references for the semi-arid or water-limited catchments. [ABSTRACT FROM AUTHOR]

• Fungal β-diversity significantly differed between the DW and NW treatments. • No significant bacterial β-diversity difference between the DW and NW treatments. • Compared to the CK, the NW treatment significantly increased bacterial ACE, Chao1 and Shannon diversity indices. • Compared to the CK, the NW treatment significantly increased fungal ACE diversity. • AP and TN are the main factors affecting bacterial Shannon diversity after DW and NW. The global temperature is continuously rising, and the impacts of nighttime warming (NW) and daytime warming (DW) on ecosystems have drawn widespread attention. However, most studies on the effects of daytime and nighttime warming on ecosystems have focused primarily on aboveground processes, but little is known about how they affect underground processes, particularly soil microorganisms. Therefore, we examined the effects of daytime and nighttime experimental warming (CK: control, DW: daytime warming, NW: nighttime warming, DW + NW: daily warming) on soil bacterial and fungal diversities at the Experimental Station of Zengcheng Forestry Science Research Institute in Guangdong, China. The results showed that, compared with the CK treatment, the NW rather than DW treatment significantly increased the abundance-based coverage estimator (ACE) diversity index of bacteria and fungi. Fungal beta diversity significantly differed between the DW and NW treatments, while there was no significant difference in bacterial beta diversity. Our research indicated that the NW treatment creates a more favourable microenvironment than the DW treatment, accelerating the mineralization of soil carbon, nitrogen, and phosphorus nutrients, which may be the reason for changes in microbial diversity. Our study provides important theoretical support and practical guidance for predicting the impact of global climate change on the diversity of microbial ecosystems. [ABSTRACT FROM AUTHOR]

The likelihood changes of the numbers of occurrences, duration and intensity of hydrological droughts in the Weihe River Basin in China were investigated by using the bias-corrected future climate projections from three selected Global Climate Models (GCMs) with two emission scenarios (RCP 4.5, RCP 8.5), and Soil and Water Assessment Tool (SWAT) hydrological model. Results showed that: 1) The frequency of hydrological droughts, drought durations and intensities would have obvious increasing trends in the future under dry GCM condition. However, an opposite decreasing trend was shown under wet GCM condition; 2) Future precipitation changing direction and magnitudes were dominating factor for the likelihood changes of drought characteristics. Forty GCMs project a future precipitation change from −3.42% to +14.24%, which is the largest source of uncertainties. If the observed trends of precipitation and temperature during the last 50 years continue, then the Weihe River Basin would likely be in the dry condition of GCMs; 3) The impacts of temperature on hydrological droughts cannot be neglected and it has direct (evaporation and runoff generation) and larger magnitude indirect effects (precipitation patterns). The presented results have practical applications for regional drought mitigation planning under future climate changes. [ABSTRACT FROM AUTHOR]

Abstract Baseflow is the portion of streamflow that originates from groundwater. It is pivotal to groundwater supply as well as the interactions between groundwater and surface water. In the Loess Plateau of China, the baseflow plays a fundamental role in sustaining the aquatic ecosystem. Rational estimation of baseflow is of critical importance for understanding the functioning of the groundwater system and informing management of regional water resources. In this study, a two-well parameterised digital filter was used to separate baseflow from observed daily total streamflow on the Weihe River Basin. Two parameters (maximum baseflow index (BFI max) and the recession constant) of this filter were estimated using UKIH and a recession analysis with physical meaning, respectively. The results show that the baseflow index increased from the upstream to downstream (0.27–0.32) of the Weihe River, and the baseflow of the river is summer dominant. In general, the baseflow has been increasing gradually owing to the implementation of soil conservation measures. This study provides an understanding of baseflow response to seasonal variability and water environmental management in basin scale. Highlights • The baseflow in the loess regional catchment with the spatial attributes. • Baseflow shows a gradually increasing trend from upstream to downstream in the Weihe River Basin. • The baseflow of this river is dominated by summer baseflow. [ABSTRACT FROM AUTHOR]