Evaluating the water footprint and nutritional quality of takeaway dishes for selected large cities in China

The takeaway food and delivery market is developing rapidly in China, raising concerns about the impacts of takeaway dishes on both health and the environment. Here, we compare the environmental impact and nutritional performance of 32 popular takeaway dishes, which stem from the top 10 best-selling takeaway dishes in 10 large cities in China. We select water footprint and water scarcity footprint indicators to represent the environmental impact, and the Food Compass Score to measure nutritional quality. Our results show that 24 out of 32 takeaway dishes contains meat, which has a higher water footprint. The inhabitants of water stressed Chinese cities, mainly located in northern China, tend to favor meat dishes, resulting in a larger water scarcity footprint. The results also highlight the lower nutrition quality of the majority of takeaway dishes, with only three takeaway dishes meeting acceptable environmental and nutritional standards. Our study highlights the importance of analyzing dishes rather than individual foods, which can facilitate sustainable dietary choices for consumers.

Uneven distributions of unique species promoting N niche complementarity explain the stability of degraded alpine meadow

Alpine meadow degradation, usually involving decreased soil nitrogen (N) and patchy landscapes, is a challenge for natural restoration. However, the mechanism underlying plant species coexistence under degradation is unclear. In this study, we evaluated plant N niche complementarity in degraded alpine meadows on the Qinghai-Tibet Plateau using a 15N-labeling (15NO3-, 15NH4+, and 15N-glycine) experiment. At the community level, the concentration of 15NO3- in the degraded alpine meadow was 1.5 times higher than that in the undegraded alpine meadow; both alpine meadows had a significant preference for NO3- (60.72 % and 66.84 % for the degraded and undegraded alpine meadows, respectively), and the degree of glycine preference was significantly higher in the degraded alpine meadow (30.77 %) relative to the undegraded alpine meadow (21.85 %). At the species level, dominant species in both alpine meadows consistently preferred NO3-; the generalist species that can be found in both meadows and unique species of the two alpine meadows generally showed NO3- preferences, while the other plant species that were unevenly distributed in the degraded alpine meadow tended to show increased utilization of glycine, which could reduce N competition. We observed that differentiation among N sources and the uneven distribution of unique species may explain the stability of degraded alpine meadows. Our results suggested that uneven distributions of plants could have strong impacts on community stability and highlighted the importance of considering fine-scale analysis in studies of niche theory. This study has important implications for the restoration of degraded alpine meadows.

Ecosystem productivity drives the breeding success of an endangered top avian scavenger in a changing grazing pressure context

Environmental conditions and resource availability shape population dynamics through direct and indirect effects of climate, biological interactions and the human modification of landscape. Even when a species seems dependent on predictable anthropogenic food resources or subsidies, ecosystem-level factors can still determine population dynamics across taxa. However, there is still a knowledge gap about the cascade effects driven by climate, vegetation functioning, resource availability and governmental policies on key aspects of species reproduction for top scavengers. Here we put to good use 22 years (2000-2021) of extensive population monitoring from the endemic Canary Egyptian vulture (Neophron percnopterus majorensis) on the Fuerteventura Island (Canary Islands, Spain) to study the relative importance of demographic factors, ecosystem conditions and availability of anthropogenic food sources on breeding success. Our results suggest that ecosystem-level primary productivity, the number of livestock animals present on the island and Density-dependent processes determine the temporal changes in the breeding success of this species. We firstly accounted for a top-down effect of livestock on island vegetation, where overgrazing directly reduces landscape-level vegetation biomass. We, consequently, found a bottom-up effect between vegetation and the Egyptian vulture's breeding success. In this context, minimal changes in ecological conditions can impact the species inhabiting these ecosystems, with direct consequences on a key population stage, such as breeding season, when energy requirements are higher. These results are especially relevant because cascading and indirect effects of ecosystem processes and governmental policies are often overlooked when pursuing conservation goals of endangered species.

Quantifying key vegetation parameters from Sentinel-3 and MODIS over the eastern Eurasian steppe with a Bayesian geostatistical model

Accurate estimation of grassland leaf area index (LAI), fractional vegetation cover (FVC), and aboveground biomass (AGB) is fundamental in grassland studies. The newly launched Ocean and Land Color Imager (OLCI) sensor onboard Sentinel-3 (S3) provides images with comparable spatial and spectral resolution with MODIS data. However, the use of S3 OLCI imageries for vegetation variable estimation is rarely evaluated. This study evaluated the potential of S3 OLCI and MODIS data for estimating grassland LAI, FVC, and AGB in the eastern Eurasian steppe. A Bayesian spatial model (Integrated Nested Laplace Approximation with Stochastic Partial Differential Equation, INLA-SPDE) was used to address spatial autocorrelation of in-situ observation data and to enhance our predictions. Our results showed that the models based on S3 OLCI data presented higher accuracy than models with MODIS data. The RMSEs decreased by 3.7-10.8 %, 3.7-7.5 %, and 1.6-14.2 % for LAI, FVC, and AGB predictions, respectively. Through combinations of multiple predictors, we confirmed the robustness of red edge bands for grassland variable estimation, the models employing red edge variables yielded 3.5 %, 3.2 %, and 0.4 % lower RMSEs than models with conventional visible and NIR bands for LAI, FVC, and AGB prediction, respectively. INLA-SPDE spatial model produced lower bias and higher prediction accuracy than random forest and random forests kriging method in most of the models; the INLA-SPDE predicted LAI and FVC maps also showed a better agreement with ground observations than MODIS and PROBA-V land products.

Response of grassland growing season length to extreme climatic events on the Qinghai-Tibetan Plateau

Extreme Climatic Events (ECEs) are increasing in intensity, frequency, and duration as the earth warms, which greatly affects the vegetation phenology. However, the response of vegetation phenology to different types of ECEs (e.g., extreme hot, extreme cold, extreme drought, and extreme wet) has not been extensively studied. To fill this knowledge gap, we investigated the relationship between the length of growing season (LOS) of grassland and ECEs on the Qinghai-Tibetan Plateau (QTP). First, we analyzed the spatial distribution and interannual trends of phenology based on the MODIS Normalized Difference Vegetation Index (NDVI). Second, we used Coincidence Rate (CR) analysis to quantify the relationship between LOS anomalies and ECEs. Finally, we analyzed the sensitivity of LOS to the intensity of ECEs. The results indicated that the spatial distribution of LOS was closely related to local hydrothermal conditions, with longer LOS in places with more precipitation or higher temperatures during the growing season, and LOS extended by 0.28 days/year from 2000 to 2022. Moreover, we found that the CR of negative LOS anomalies to ECEs notably exhibited variations along climatic gradients, with higher CR to extreme hot generally occurring in warmer areas. Meanwhile, the CR of extreme wet increased while the CR of extreme drought decreased with increasing precipitation. We also found that the sensitivity of LOS to ECEs changed more markedly, along the climatic gradients, in alpine ecoregions compared to temperate ecoregions. Overall, the sensitivities of LOS ranked in descending order of absolute sensitivity to extreme drought, extreme wet, extreme hot, and extreme cold. This study furthers our understanding of the grassland response to ECEs under different hydrothermal conditions, which can provide valuable reference for the management and conservation of grassland ecosystems in QTP under future climate change scenarios.

Life-cycle impact assessment of hardwood forest resources in the eastern United States

To explore the carbon sequestration potential of hardwood forests in the eastern United States, the forest vegetation simulator (FVS) and life cycle assessment (LCA) were integrated to analyze the forest carbon dynamics for the four subregions of the eastern United States: northeast (NE), mid-Atlantic (MA), southeast (SE), and north central (NC). This study quantitatively assessed current forest management practices for timber production and their associated life-cycle environmental impacts. The system boundary was selected to be consistent with the A1 module (extraction and upstream production) required by an Environmental Product Declaration (EPD) for wood products. The results indicate that uneven-aged (UA) forest management yields higher carbon stocks and growth than even-aged (EA) management across all subregions. In contrast, clearcutting under EA management results in higher carbon removal. It was found that fuel consumption-related greenhouse gas (GHG) emissions for manual and mechanized harvesting systems for both management types ranged between 9.13 and 12.15 kg of CO2 equivalent per cubic meter (kg CO2e/m3), with an average of 11 kg CO2e/m3 of hardwood timber harvested across all subregions. It is estimated that 63-187 megajoules (MJ) of energy is needed to produce 1 m3 of hardwood sawlogs. The extraction and loading processes contributed more to the total GHG emissions than the felling and processing within the system boundary. The study concludes that UA management led to higher forest carbon and net carbon balance (excluding carbon stock) compared to EA management in the eastern U.S. hardwood forests. Forest management strategies should be determined based on the ecological goal of increasing forest carbon stock and the economic goal of maximizing revenue from the timber market. The findings of this study have implications for policymakers and forest managers in mitigating climate change and carbon sequestration through sustainable forest management for timber production.

Land use/cover and land degradation across the Eurasian steppe: Dynamics, patterns and driving factors

Despite the ecological and socio-economic importance of Eurasian steppe, the land use/cover change, land degradation and the threats facing this precious ecosystem still have not been comprehensively understood. Taking advantages of the land use/cover change monitoring platform (FROM-GLC Plus), this study developed the annual land use/cover maps during 2000-2022, and the land use/cover change, especially the change of grassland, was further analyzed. The grassland area exhibited a net increase, predominantly transformed from cropland, forest, and bareland, accounting for 17.64 %, 31.91 %, and 45.60 %, respectively. To monitor land degradation, we adopted the framework suggested by the United Nations Convention to Combat Desertification (UNCCD). According to the monitoring result, grassland constituted the highest proportion of degraded land (39.82 %). This may due to its dominance in the Eurasian steppe's land use/cover, as the extent of grassland degradation (1.92 %) was lower than the overall land degradation level (2.83 %) across the region. To offer tailored and sustainable development recommendations, we quantified the driving factors behind land dynamics using the geographical detector model and convergent cross mapping (CCM), considering both spatial and temporal dimensions. Environmental and socio-economic factors, such as precipitation, temperature, urbanization, mining and grazing intensity, etc., were integrated into the analysis. We found that urbanization, cropland and moisture distribution emerged as key drivers influencing land degradation's spatial distribution in the Eurasian steppe, while temperature variations between years impacted vegetation changes. This research thus provides a deeper understanding of the region's land dynamics, enhancing comprehensive monitoring of the Eurasian steppe's land dynamics. Moreover, it serves as a foundation for policymakers and land managers to devise conservation strategies and sustainable development initiatives for this critical ecosystem.

Dynamics of tannin variations in mangrove leaf litter decomposition and their effects on environmental nitrogen and microbial activity

Tannins play vital roles in regulating ecological processes in mangrove forests. However, how tannins affect nitrogen (N) cycling and microbial metabolism in mangrove ecosystems remains largely unexplored. In this study, we hypothesized the types and amounts of tannins released into seawater and sediments during leaf litter decomposition differed among mangrove plant species, thus their effects on N and microbial metabolism also varied. The alterations of tannins, and environmental N and microbial metabolism during leaf litter decomposition of Kandelia obovata, Avicennia marina, and Sonneratia apetala were evaluated by a microcosm-simulated tidal system. Results showed that total polyphenols (TPs) in seawater treated with K. obovata litter were significantly higher than those in A. marina and S. apetala treatments, although the trends of TP changes elicited an initial increase followed by a decrease during decomposition. The dynamic changes in TPs reduced the seawater N concentrations in K. obovata treatment but not in A. marina and S. apetala treatments. The results of microbial metabolism analysis revealed that leaf litter significantly increased microbial metabolic activities and diversities. The types of carbon sources utilized by sediment microorganisms differed among treatments, with the microbes in S. apetala and A. marina litter used more varieties of amino acids, lipids and sugars than those in K. obovata treatment, probably due to the rich amount of hydrolysable tannins (HTs) in the first two species while the last species only contained ondensed tannins (CTs). CTs released from K. obovata leaf litter not only bound nitrogen-containing macromolecular compounds such as amino acids and proteins but also carbohydrates like polysaccharides, which decreased the supply of C and N to sediment microbiota. These results reveal that the release of mangrove tannins during leaf litter decomposition is one of the key factors driving N cycling, and microbial activities and diversities in mangrove wetlands.

Comparative responses of carbon flux components in recovering bare patches of degraded alpine meadow in the Source Zone of the Yellow River

The patchy degradation of alpine grasslands is a common phenomenon on the Qinghai-Tibetan Plateau, and the presence of bare patches (BP) in degraded grasslands significantly affects the functioning of the alpine meadow ecosystem. The succession of vegetation-recovered BP may lead to significant changes in ecosystem carbon (C) cycling. To date, it is unclear whether different components of net ecosystem carbon exchange (NEE) respond similarly or differently to the succession of recovering BP. Here, we conducted a field monitoring experiment in a degraded alpine meadow, and selected three successional stages for recovering BP to study the response of NEE and its components. We found that the succession of recoevering BP increased ecosystem respiration (ER) during the growing season and decreased ER during the off-growing season, with the differences in annual carbon output between different successional stages being insignificant. However, gross primary productivity increased with the successional gradient, and carbon input at the later stage of succession was significantly greater than that at the middle stage of succession. The succession of recovering BP promoted the carbon sequestration function of the alpine grassland, with the grassland acting as a carbon sink when it reached the state of healthy alpine meadow, while it acted as a carbon source during the middle stage of succession. Compared with BP, the amount of carbon sequested by healthy alpine meadows increased significantly by 219 g·C·m-2·yr-1. We also found that the responses of other components to the succession of recovering BP were inconsistent. In addition, the effects of succession of recovering BP on carbon flux were related to field-monitored variables (soil temperature and water content) and other considered variables (biomass, organic carbon, and microbial biomass carbon). These research findings highlight the importance of restoring vegetation in BPs, and are crucial for predicting the carbon balance in the future and formulating sustainable grassland management strategies.

Characteristics of microplastic-derived dissolved organic matter and its binding with pharmaceuticals unveiled by fluorescence spectroscopy and two-dimensional correlation spectroscopy

Microplastics were an extensively detected pollutant in the environment, but microplastic-derived dissolved organic matter (MP-DOM) has received less attention, much less its impact on the binding behavior of pollutants (e.g., pharmaceuticals). In this study, DOM derived from two typical MPs, i.e., polyethylene terephthalate (PET) and polystyrene (PS) was generated by UV irradiation (a widely used way for MPs' aging treatment) and characterized by multiple spectroscopic techniques and methods. Chloramphenicol (CAP) and carbamazepine (CBZ) were selected to investigate the binding mechanism between MP-DOM and pharmaceuticals. After UV irradiation, the concentration of the dissolved organic carbon, colored DOM, and carboxyl/carbonyl groups of MP-DOM increased. Moreover, the humic-like substance released preceding and more under UV irradiation. Furthermore, the protein-like substances on PET-DOM and the humic-like substances on PS-DOM were positively correlated to the binding capacity to the pharmaceuticals, respectively. 2D-COS results revealed that the fluorescent materials having more oxygen-containing functional groups for MP-DOM preferentially interacted with the pharmaceuticals. Overall, the higher fluorescence quenching was related to the protein-like substance, CBZ, and PET-DOM as compared to the humic-like substance, CAP, and PS-DOM. It was verified by the relatively high binding ability (logKM) for them (the protein-like substance: 5.15; CBZ: 4.61; PET: 4.48). This study first proved the environmental reactivity of MP-DOM to the pharmaceuticals highlighting the significance of the spectral properties for the binding behavior of MP-DOM with pharmaceuticals and the competitive sorption role of MP-DOM to the pollutants in the natural environment.

Source, composition and molecular diversity of dissolved and particulate organic matter varied with riparian land use in tropical coastal headstreams

Source, composition and molecular diversity determine the reactivity and stabilization of organic matter (OM, dissolved [DOM]/particulate [POM]), affecting its behavior and fate. Here, multiple spectral and mass spectrometry techniques were applied to examine how riparian land-use shaped the source, composition and molecular diversity of POM and DOM (HDOM) in adjacent headstreams. Compared to HDOM with abundant lignins, microbially-transformed heteroatoms and carboxyl-rich alicyclic acids (CRAMs), POM exhibited higher allochthonous characteristics and more bioactive components, but lower molecular weight and diversity in different land-use-dominated streams. Compared to wetland-dominated headstreams, both POM and HDOM exhibited more terrestrial origin and condensed aromatics/tannins molecules for agriculture-impacted headstreams and bio-labile lipids, proteins and carbohydrates for forest-impacted headstreams. Structural equation mode (SEM) showed that soil-derived DOM (SDOM) showed the most prominent influence on the source, composition and molecular diversity of POM and the source of HDOM. The molecular composition and diversity of HDOM were mainly influenced by soil properties/SDOM and aquatic microorganisms, respectively. Redundancy analysis (RDA) revealed that autochthonous, bio-labile compositions of POM in forest and wetland streams were positively related to aquatic Bacteroidetes/Cyanobacteria, and carbohydrates/biogenic index of SDOM, while that of HDOM were positively linked with aquatic Bacteroidetes/Cyanobacteria, and SDOM molecular diversity. Terrestrial and aromatic POM in agricultural headstreams were associated with aquatic total nitrogen/Actinobacteria, and humification degree, aromatic/phenolic substances of SDOM, while that of HDOM were mainly regulated by aquatic nitrate/total nitrogen/Actinobacteria, and aromatic/carboxylic-containing moieties of SDOM. Noteworthily, the molecular diversity of agricultural OM increased along the soil-stream continuum due to the input of soil condensed aromatics and tannins. The opposite trend was observed in forest and wetland streams due to the input of bioactive carbohydrates and the microbial-degradation in-stream. These results are helpful to predict the behavior and fate of OM and determine effective management strategies in tropical coastal regions undergoing intense anthropogenic alterations.

Nitrogen and water addition alters species diversity and interspecific relationship in a desert grassland

Water and nitrogen (N) often affect plant species diversity and interspecific relationship among plant populations in global terrestrial ecosystems. However, the effects of water and N addition on plant diversity and interspecific relationship remain poorly understood. In the study, we designed a three-year field experiment in a desert grassland to assess the effect of increased water (natural +50 %) and N addition (10 g·N·m-2·a-1) on plant diversity and interspecific relationship. Our results showed that the alpha diversity was significantly changed under increased water (W), N addition (N), and water plus N addition (WN). The species richness was decreased significantly on year scales (10 %-27 %), whereas the Pielou index first increased and then decreased over three years and was significantly affected by the interaction between increased water and N addition. The total and pairwise beta diversity were significantly increased by N addition, the community was mainly caused by the turnover component after N addition, especially in 2019 and 2020 (16.6 % and 9 %, respectively). There were significant negative associations among overall populations and dominant populations under N addition, especially Stipa bungeana and Gypsophila davurica, Gypsophila davurica and Oxytropis acemose, Artemisia dalai-lamae, and Haplophyllum dauricum. Our findings suggested that plant community structure and composition changes may be due to competition for resources among dominant populations and the turnover component under increased water and N addition, which should be considered in ecosystem management.

Threshold response of ecosystem water use efficiency to soil water in an alpine meadow

Ecosystem water use efficiency (WUE) is a coupled index of carbon (gross ecosystem productivity, GEP) and water fluxes (transpiration, Tr or evapotranspiration, ET), reflecting how ecosystem uses water efficiently to increase its carbon uptake. Though ecosystem WUE is generally considered to decrease with increasing precipitation levels, it remains elusive whether and how it nonlinearly responds to extreme water changes. Here, we performed a 5-year precipitation halving experiment in an alpine meadow, combined with extremely interannual precipitation fluctuations, to create a large range of soil water variations. Our results showed that WUETr and WUEET consistently showed a quadratic pattern in response to soil water. Such quadratic patterns were steadily held at different stages of growing seasons, with minor changes in the optimal water thresholds (25.0-28.4 %). Below the water threshold, more soil water stimulated GEP but reduced Tr and ET by lowering soil temperature, resulting in a positive response of ecosystem WUE to soil water. Above the threshold, soil water stimulated GEP less than Tr (ET), leading to a negative response of ecosystem WUE to soil water. However, biological processes, including plant cover and belowground biomass as well as vertical root biomass distribution, had less effect on ecosystem WUE. Overall, this work is among the first to reveal the nonlinearity and optimal water thresholds of ecosystem WUE across a broad range of soil water, suggesting that future extreme precipitation events will more frequently surpass the water threshold and differently change the coupling relationships of carbon and water fluxes in alpine grasslands.