The combined effects of climate change and human activities pose threat to the sustainable development of ecosystems. Human appropriation of net primary production (HANPP) has been extensively used as an important indicator for evaluating the sustainable development of the ecosystem. However, few studies quantitatively assessed the driving factors of HANPP. Based on Moderate-Resolution Imaging Spectroradiometer (MODIS) data, methods of net primary production (NPP) model and regression analysis, the spatial and temporal distribution of HANPP and its driving factors in the Qilian Mountains from 2005 to 2015 were illustrated. The results showed that the HANPP in the Qilian Mountains decreased gradually from both east to west and from south to north, showing a slight upward overall. The regions affected by human activities and climate change accounted for 26.8% and 73.2% respectively. Moreover, there was a significant negative impact between grain yield and HANPP, and a significant positive impact of either the annual sunshine duration, or livestock amount to HANPP.
ABSTRACT Microbial communities in riverine hyporheic zones provide essential ecosystem services. However, the mechanisms whereby they respond to hyporheic water exchange under different habitat stress conditions remain poorly understood. Therefore, investigating the impact of riverine hyporheic exchange on the microbial community composition and its potential ecological function is essential, particularly in the seasonal rivers of northern China. To elucidate the structure and function of hyporheic zone sediment microbial communities in response hyporheic exchange and environmental fluctuations, we examined associations by performing in situ falling‐head permeameter tests and eDNA techniques. The primary findings were as follows: (1) We detected variations in the spatial distribution patterns of streambed hydraulic conductivity (range, 0.055–3.490 m/day) and vertical fluxes (range, 1.886–342.0 mm/day) among different monitoring stations. (2) Microbial communities displayed compositional similarities and spatial heterogeneity. Stations with limited vertical exchange were characterised by reduced species diversity. (3) Prokaryotes showed better modularity characteristics with higher stability and functional diversity than eukaryotic communities. (4) Differences in the abundance of microbial metabolism and genetic functions were observed among different habitats. This study emphasises the significance of local hydrological patterns (such as downwelling) in maintaining riverine environmental elements and acting as hotspots for microbial diversity within the hyporheic zone. The heterogeneity of the hydrological patterns governing hyporheic water exchange can explain the abundance, species diversity and biogeochemical processes of microorganisms within this zone.
Variable infiltration capacity model is used to quantitatively analyse the runoff reduction benefits of three basins on the Loess Plateau since the implementation of the 'Grain for Green' programme. The programme played an important role, contributing to >60% of the runoff variation in the different basins. Furthermore, for every 1000 km2 increase in cumulative forest area in basins, the rate of runoff coefficient reduction changed by −30%, −37.3% and 169% in the late stage of the programme compared to the early stage, respectively ('-' represents a decrease in reduction rate). This was closely related to the restoration of vegetation.
The bioturbation activity of macroinvertebrates can affect the level of water exchange across the sediment–water interface. The impact of tubificid worm with different densities on the vertical water exchange at the sediment–water interface was investigated based on laboratory flume experiments. Vertical water fluxes, as well as physiochemical parameters, were measured at seven-day intervals, and the maximum penetration depths were obtained by dye injection before and after the tubificid bioturbation experiment, respectively. The bioturbation effects can be summarized in two aspects: (1) when the density was less than (or equal to) 20 individual/10 cm2, the volume of vertical water exchange positively correlated with the tubificid bioturbation. Once the density exceeded (or equaled) 25 individual/10 cm2, the vertical water flux decreased with increasing tubificid bioturbation. After 14 to 21 days, a negative correlation was identified between the bioturbation and the vertical water flux under all biological densities. (2) The maximum depth that the surface water can penetrate the sediment increased with increasing tubificid density. These results revealed that the vertical water was closely related to the biological density. The study has certain reference significance to understanding the spatiotemporal heterogeneity of hyporheic water exchange on a local scale.
The groundwater-dependent ecosystem in the Gnangara region is confronted with great threats due to the decline in groundwater level since the 1970s. The aim of this study is to apply multiple trend analysis methods at 351 monitoring bores to detect the trends in groundwater level using spatial, temporal and Hydrograph Analysis: Rainfall and Time Trend models, which were applied to evaluate the impacts of rainfall on the groundwater level in the Gnangara region, Western Australia. In the period of 1977–2017, the groundwater level decreased from the Gnangara’s edge to the central-north area, with a maximum trend magnitude of −0.28 m/year. The groundwater level in 1998–2017 exhibited an increasing trend in December–March and a decreasing trend in April–November with the exception of September when compared to 1978–1997. The rainfall + time model based on the cumulative annual residual rainfall technique with a one-month lag during 1990–2017 was determined as the best model. Rainfall had great impacts on the groundwater level in central Gnangara, with the highest impact coefficient being 0.00473, and the impacts reduced gradually from the central area to the boundary region. Other factors such as pine plantation, the topography and landforms, the Tamala Limestone formation, and aquifer groundwater abstraction also had important influences on the groundwater level.
Limited water resources and rapid socioeconomic development pose new challenges to watershed water resource management. By integrating the perspectives of stakeholders and decision-makers, this study aims to identify cases and approaches to achieve sustainable water resources management. It improves and expands the experience of previous project research. The comparative evaluation provides an analytical basis to verify the importance of stakeholder participation in water policy interactions. The results show that if an effective demand management policy is not implemented, the Guanzhong area will not meet water demand in the future. Through the combination of water-saving policies, water transfer projects and other measures, the available water resources will continue into the future. Optimizing management measures, improving the ecological environment, and encouraging stakeholder participation will help change this situation, although supply-side limitations and future uncertainties likely cause unsustainable water. Therefore, decision-makers should pay attention to the application potential of water-saving and other measures to reduce dependence on external water sources. In addition, the three sustainable development decision-making principles identified in this paper can promote the fairness and stability of water policy.
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