Interannual variation in resource abundance has become more unpredictable, and food shortages have increasingly occurred in the recent decades. However, compared to seasonal fluctuations in resource ...abundance, the influences of interannual variation in resource abundance on the dietary niches of consumers remain poorly understood. Poyang Lake, China, is a very important wintering ground for the globally endangered Siberian Crane (Leucogeranus leucogeranus), White-naped Crane (Grus vipio), and Hooded Crane (G. monacha), as well as the non-endangered Eurasian Crane (G. grus). Tubers of Vallisneria spp., the dominant submerged macrophytes at Poyang Lake, is an important food for cranes. Nevertheless, submerged macrophytes have experienced serious degradation recently. In this study, we used metabarcoding technology to explore the consequences of Vallisneria tuber collapse on the diet compositions, breadths, and overlaps of the four crane species based on fecal samples collected in winter 2017 (a year with tuber collapse) and winter 2018 (a year with high tuber abundance).
Compared to previous studies, our study elucidates crane diets in an unprecedented level of detail. Vallisneria tubers was confirmed as an important food source of cranes. Surprisingly, the grassland plant Polygonum criopolitanum was also found to be an important food source in the feces of cranes. Agricultural fields were important foraging sites for Siberian Cranes, White-naped Cranes, and Hooded Cranes, providing foods that allowed them to survive in winters with natural food shortages. However, the three crane species preferred natural wetlands to agricultural fields when the abundance of natural foods was high. The abundance of Vallisneria tubers, and probably P. criopolitanum, greatly influenced the dietary compositions, breadths and overlap of cranes. During periods of preferred resource shortage, White-naped Cranes and Hooded Cranes widened their dietary niches, while Siberian Cranes maintained a stable niche width. The dietary niche overlap among crane species increased substantially under conditions of plentiful preferred food resources.
Our study emphasizes the superior quality of natural wetlands compared to agricultural fields as foraging habitats for cranes. To provide safer and better foraging areas for cranes, it is urgent to restore the submerged plants at Poyang Lake. While high dietary niche overlap is often interpreted as intense interspecific competition, our study highlights the importance of taking food abundance into account.
Landslide and debris flows are typically triggered by rainfall-related weather conditions, including short-duration storms and long-lasting rainfall. The critical precipitation of landslides and ...debris flow occurrence is different under various hydrometeorological conditions. In this study, the trigger sensitivities of different daily hydrological variables were assessed using 50 days-worth of recorded landslide and debris flows using the Soil and Water Assessment Tool model. The event days were divided into long-lasting rainfall trigger (LLR-trigger) event days and short-duration storm trigger (SDS-trigger) event days with six determinate criteria based on modeled wetness states. The landslide and debris flow prediction model was built using nine hydrometeorological variables, and the predictive performance was tested with simulated data from 2010 to 2012. The results suggest that, except for rainfall, historical hydrological variables and their development provide important information for triggering landslides and debris flows. The prediction model with an area under curve (AUC) value of 0.85 was able to capture most of the landslides and debris flows. The temporal distribution of the two triggering events predicted by the model was consistent with the annual precipitation distribution. In addition, the spatial variations of the specific trigger types could be attributed to the different land covers. Despite some uncertainty, this study provides an idea of improving the landslide and debris flow prediction model.
As a critical service of terrestrial ecosystem, water regulation (conservation and provision) shows complicated regional heterogeneities due to interactions of various land covers and climate ...conditions. The widely used valuation methods usually lack accurate descriptions of hydrological responses to multiple land covers, and also ignore their regional differences at large scales. Tibetan Plateau is well known as the Asian water tower with the most diverse and vulnerable ecosystems, and 44 counties in the Brahmaputra, Salween and Lancang River Basins, and Qinghai Region are selected as our study area. The terrestrial ecosystem services are valuated for individual land covers at county scale using improved hydrological simulations for alpine regions (particularly freezing and thawing process simulations of snow cover and glacier), and their regional differences are further identified using multivariate statistical analysis. Results show that runoff hydrographs at most stations are well reproduced with relative bias within ±15%, and average correlation coefficient and efficiency coefficient of 0.88 and 0.72, respectively. The total water regulation values are from US$ 0.59 × 108 to US$ 69.80 × 108 at county scale, accounting for 4.6%–7807.7% of local gross domestic products in the 2015 price level. Thereinto, the water conservation values are the greatest for grass (15.2%–91.2% of total), followed by forest (0.0%–51.3%) and cropland (0.0%–32.4%), while the water provision values are the greatest for glacier (0.0%–80.9%), followed by waterbody (0.0%–38.2%). The water conservation zones of grass, forest and cropland, and the water provision zones of glacier and waterbody are identified, and show obvious regional differences. These zones are in 61.4% of total counties, middle and downstream counties (20.5%), downstream counties of Qinghai Region (4.5%), source counties (9.1%), and middle stream counties of Qinghai Region (4.5%), respectively. This study gives new insights into the valuation of terrestrial ecosystem services in alpine regions, and provides scientific evidence for regional ecological compensations and protection in the Tibetan Plateau.
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•HEQM is improved for water regulation simulations of various land covers.•Water regulation service compositions and their spatial differences are assessed.•Water regulation values are greater than local GDP in 82% of total counties.•Five regulation zones of land covers are identified for 44 counties.•Water conservation zone of grass is dominant in 61.4% of total counties.
A simple and effective ratiometric fluorescence imaging method was proposed for the visualizing and quantitative detection UO22+ ions by cellphone-based optical platform. This method has greatly ...shortened the detection time, reduced the cost of detection, and improved the accessibility of UO22+ ions detection even in resource-limited areas.
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Under the public spotlight, uranyl (UO22+) ions has attracted considerable attention for the extreme radioactive and chemical toxicity to ourselves and our environment. Herein, we present a simple and effective ratiometric fluorescence imaging method for the visualizing and quantitative detection UO22+ ions by cellphone-based optical platform. The sensing solution was prepared by mixing label-free red carbon dots (r-CDs) and blue carbon dots (b-CDs) together with a fixed photoluminescence intensity ratio of 4:1. When UO22+ ions were added, the fluorescence of r-CDs can be selectively quenched, while the fluorescence of b-CDs remains stable without spectral changes. With the gradually increase the amounts of UO22+ ions, the different response of dual-color CDs resulted in a signification color evolution from deep red to dark purple under the ultraviolet (UV) light illumination. Then, a cellphone-based optical platform was constructed for directly imaging the color change of the samples, and the built-in Colorpicker APP quickly output the red, green and blue (RGB) channel values of these images within one second. Interesting, there was a linear relationship between the ratio of red and blue (R/B) channel values and UO22+ ions concentration from 0 μmol/L to 30.0 μmol/L (R2 = 0.92804) with the detection limit of ∼8.15 μmol/L (signal-to-noise ratio of 3). In addition, the optical platform has also been applied to the quantification of UO22+ ions in tap water and river water sample. With the advantage of low-cost, portable, easy to operation, we anticipate that this method would greatly improve the accessibility of UO22+ ions detection even in resource-limited areas.
A smartphone-based dual-wavelength digital imaging platform containing red (539–695 nm) and blue (389–511 nm) band-pass filters was developed for point-of-care (POC) testing of alkaline phosphatase ...(ALP) activity. The platform was based on dual-emitting fluorescent nanohybrids (AuNC@NAN), the ratiometric probe, which had a fluorescence “on-off-on-off” response. The probe comprised red-emitting gold nanoclusters (AuNCs) acting as the signal report units and blue-emitting N-(2-aminoethyl-1,8-naphthalimide) (NAN) acting as an internal reference. The different responses of the ratiometric probes resulted in a continuous color-multiplexing change from pink-red to dark-purple upon exposure to ALP. The dual-wavelength digital imaging platform was employed to acquire images of AuNC or NAN fluorescence signals without the influence of background light. Unlike the classical one-time digital imaging mode, the accurate red (R) and blue (B) channel values of the generated images can help to directly judge or eliminate the disturbance from unavoidable interfering factors. The R/B values were successfully employed for determining the ALP activity at a range 2.0 to 35.0 mU·mL
−1
with the detection limit of 1.04 mU·mL
−1
. Such sensing imaging platform is also successful in determining ALP activity in human serum with 94.9–105% recoveries and relative standard deviation in the range 4.2–5.6%.
Graphical abstract
A novel dual-wavelength smartphone-based digital imaging platform was proposed for simultaneous readout of the reporting and internal reference signals from dual-emitting ratiometric fluorescence probes, which allowed us to the accurate, reliable, and highly sensitive assay of ALP activity in complex samples.
The cropping system conversion, from rice to vegetable, showed various influences on the greenhouse gases (GHG) emission with conversion time and fertilizer/irrigation management. In this study, we ...evaluated the DeNitrification-DeComposition (DNDC) model for predicting carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) emissions and crop yields as rice converted to vegetable cropping system under conventional or no fertilization from 2012 to 2014. Then, we quantified the long-term (40 years) impacts of rice-vegetable cropping system conversions and fertilization levels (0, 50, 100 and 150% conventional fertilization rate) on GHGs emissions and global warming potentials (GWP) using the calibrated model. The DNDC model-simulated daily GHG emission dynamics were generally consistent with the measured data and showed good predictions of the seasonal CH4 emissions (coefficient of determination (R2) = 0.96), CO2 emissions (R2 = 0.75), N2O emissions (R2 = 0.75) and crop yields (R2 = 0.89) in response to the different cropping systems and fertilization levels across the two years. The overall model performance was better for rice than for vegetable cropping systems. Both simulated and measured two-year data showed higher CH4 and CO2 emissions and lower N2O emissions for rice than for vegetable cropping systems and showed positive responses of the CO2 and N2O emissions to fertilizations. The lowest GWP for vegetable without fertilization and highest the GWP for rice with fertilization were obtained. These results were consistent with the long-term simulation results. In contrast to the two-year experimental data, the simulated long-term CH4 emissions increased with fertilization for the rice-dominant cropping systems. The reasonable cropping systems and fertilization levels were recommended for the region.
Many waterbird populations have become increasingly dependent on agricultural habitats for feeding. While habitat destruction has been proposed as a key reason forcing waterbirds to move from natural ...habitats to agricultural habitats, few have used long‐term data to test this hypothesis. The Siberian crane (Leucogeranus leucogeranus) is an IUCN Critically Endangered species. About 98% of its global population winters at Poyang Lake, China. Recently, many cranes shifted from feeding in natural wetlands to agricultural habitats. Here, we integrate bird surveys, Vallisneria tuber (the traditional food of cranes in natural wetlands) surveys, water level data, and remotely sensed images from 1999 to 2016 to explore the drivers of this habitat shift. Changes in Siberian crane numbers in natural wetlands and agricultural fields indicated that the habitat shift occurred in the winters of 2015–2016. Analyses using generalized linear mixed models suggested that crane numbers in natural wetlands were positively related to tuber density and the interaction between dry season (October–March) water level and tuber density. The changes in tuber density and dry season water level in 2015–2016 indicated that tuber disappearance may have been the primary driver of the habitat shift, with a smaller effect of high water level. Submerged plants at Poyang Lake have degraded seriously in the past two decades. The plant degradation at Shahu Lake, a sublake of Poyang Lake, may have been caused by high spring water, high winter temperature, and low summer temperature. However, the drivers of tuber disappearance at Poyang Lake may not be restricted to these variables. Because Poyang Lake is an important refuge for many waterbirds in the Yangtze River floodplain, it is urgent to take effective measures to restore its submerged plants and ecosystem health. Agricultural fields can be important refuges for Siberian cranes, mitigating the negative impacts of wetland deterioration.
Our study, using field surveys and remotely sensed images from 18 years, suggests that habitat degradation affecting food shortage may have been the primary driver of the Siberian Crane, an IUCN Critically Endangered species, shifting from feeding in natural wetlands to agricultural habitats at its most important wintering ground, Poyang Lake, China, in the winters of 2015–2016.
Fluorescent colorimetric test strips normally have a narrow dynamic detection–range due to the limited responsive range from single responsive materials, which cannot meet the wide detection ...requirement in practical applications. Herein, we developed an approach to detect uranyl ions (UO22+) with a broad detection range using the synthesized ZnS:Mn quantum dots (QDs) modified Zn2GeO4 nanoellipsoids (Zn2GeO4 @ZnS:Mn NEs), containing two responsive materials with the opposite signal responses at different UO22+ concentrations. Specifically, a red to chocolate color change was observed at low analyte concentrations (0.01–100 μM) resulting from the photoinduced electron transfer effect from ZnS:Mn QDs to UO22+. A sequentially olive drab to green color change has been observed when further increasing the UO22+ concentration (100–1000 μM) as a result of the antenna effect between Zn2GeO4 nanoellipsoids and UO22+. In addition, a low-cost and portable fluorescent test strip has been further fabricated through embedding Zn2GeO4 @ZnS:Mn NEs on a microporous structure membrane, demonstrating a facile yet effective colorimetric response to UO22+ in lab water, lake water, and seawater with a wide dynamic range. Therefore, it is potentially attractive for real-time and on-site detection of UO22+ in sudden-onset situations.
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•A simple hydrothermal approach to synthesize Zn2GeO4@ZnS:Mn nanoellipsoids.•Expanding UO22+ detection range up to 5 orders by combining PET and antenna effect.•A distinct color change form red to green at various UO22+ concentrations.•Fluorescent test strip to quantitative detect UO22+ by RGB analysis.
An ideal adsorbent material that combines the multiple capabilities of sensitive detection, efficient adsorption, and repeatable removal of uranium (U) from the environment remains a serious ...challenge. Herin, a general method was developed for synthesizing a series of phosphate anions (such as: PO43-, P2O74-, P3O105- and P6O186-) modified magnetic mesoporous silica nanoparticles (Fe3O4 @mSiO2-Zn2+ NPs). The mesoporous surfaces and abundant phosphate groups provide potential, powerful uranium-binding sites for capturing U(VI) ions. Especially, the optimum adsorption capacity of Fe3O4 @mSiO2-Zn2+/P3O105- NPs was as high as 885.90 mg·g−1 (298 K), which was higher than that of unmodified or other phosphate anions-modified Fe3O4 @mSiO2-Zn2+ NPs. Meanwhile, P3O105--binding sites and mesoporous surfaces also strongly restrict U(VI) ions’ fluorescence vibrational inactivation, the adsorption results in rapid green fluorescence enhancement (within 180 s), and an ultra-low detection limit (4.5 nmol·L–1), which is well below the standard in drinking water of the World Health Organization (WHO). Furthermore, even after 5 cycles, the adsorbent still maintained their original adsorption capacity of 80.21% and displayed excellent selectivity for detecting and removing U(VI) from seawater. Based on these results, the Fe3O4 @mSiO2-Zn2+/P3O105- NPs seem to be a suitable multifunctional adsorbent for the detection, adsorption, and removal of U(VI) from environment.
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•General method for synthesizing phosphate anion-modified Fe3O4 @mSiO2-Zn2+ NPs.•Surface modification significantly enhances U(VI) sorption capacity.•Visible green fluorescence enhancement facilitates U(VI) ions detection.•Excellent reusability for the repeated separation of U(VI) ions.
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