Under the background of greenhouse gases emission reduction, the measurement of carbon emissions from the tourism industry has attracted increasing academic attention. Tourism is not a traditional ...sector in the System of National Accounts, and as a result the statistics of carbon dioxide emissions of the tourism industry on a national scale is difficult to calculate. The measurement methodology of a bottom-up approach and a top-down approach were mainly used in others studies. Utilizing a boundary that includes domestic tourism consumption, inbound tourism consumption, and tourism consumption incurring domestically in relation to outbound travel and airfares paid to the national carriers, a top-down approach is used to measure the national tourism dioxide emissions combining the Tourism Satellite Account and the Input–Output model from productive industry. Using this case study, it was calculated that the total carbon emissions of the Chinese tourism industry in 2002, 2005, 2007 and 2010 were 111.49 Mt, 141.88 Mt, 169.76 Mt and 208.4 Mt respectively, accounting for 2.489%, 2.425%, 2.439% and 2.447% respectively of the total carbon emission of all industries in China. The indirect carbon emissions by other tourism sectors except the transport sector were 3–4 times their direct carbon emissions. Compared with the manufacturing industry, the tourism industry is an industry of low pollution and low energy consumption. We discuss the advantage and shortcoming of the two approaches and put forward some suggestions to assist the research of tourism carbon emissions.
•A top-down framework is provided to measure the national tourism dioxide emissions.•An approach is applied to China at a national level, and CO2 emission values were calculated.•Carbon emission of tourism is 208.4 Mt in 2010, accounting for 2.447% of the total.
Microplastics, as emerging contaminants, pose a serious threat to terrestrial ecosystems, yet their impact on plant communities remains largely unexplored. This study utilized the soil seed bank to ...establish naturally germinated plant communities and investigated the effects of polyethylene (PE) and polypropylene (PP) on community characteristics. Additionally, the study aimed to elucidate the mechanisms by which variations in soil properties influenced plant community. The results indicated that microplastics led to a significant increase in soil available potassium (AK), likely due to alterations in soil microorganism proliferation. Furthermore, microplastics caused a decrease in soil salinity, total phosphorus (TP), and ammonium nitrogen (AN). Additionally, plant community composition shifted, resulting in reduced stability and niche breadth of dominant species. Microplastics also impacted niche overlap and interspecific associations among dominant species, possibly due to the reduced accessibility of resources for dominant species. Salinity, AK, and TP were identified as major drivers of changes in niche breadth, niche overlap, and community stability, with TP exerting the strongest impact on plant community composition. These findings provide valuable insights for the restoration of plant communities in coastal saline-alkali wetland contaminated by microplastics.
•Microplastics significantly increased soil AK and decreased soil salinity, TP and AN.•Microplastics altered plant community composition, resulting in reduced stability and niche breadth of the most dominant species.•Microplastics altered the niche overlap and interspecific associations among dominant species.•Salinity, AK and TP were important determinants of niche breadth, niche overlap, and community stability. The composition of plant community was most affected by TP.
Our study aimed to investigate the prevalence and risk factors of low bone mineral density (BMD) among HIV/AIDS patients in China.
We performed a cross-sectional analysis of HIV-infected patients ...from October 2017 to August 2020. Demographic information, clinical data, and serum parameters were obtained. Univariable and multiple logistic regression analyses were performed.
A total of 1143 patients were included. In the ART-naive group, low BMD was diagnosed in 19.2% (117/608), including osteoporosis in 1.0% (6/608) and osteopenia in 18.3% (111/608). In the ART group, low BMD was diagnosed in 32.2% (231/717), including osteoporosis in 2.4% (17/717) and osteopenia in 29.8% (214/717). Using multivariate analysis, we identified age older than 50 years, body mass index < 18.5 kg/m2, and treatment based on tenofovir disoproxil fumarate as independent risk factors for low BMD. Low high-density lipoprotein cholesterol was a protective factor for low BMD. Among low BMD participants, the most common number of low BMD sites for a patient to have was 4 (33.6%, 117/348).
We confirmed a high prevalence of low BMD and osteoporosis in HIV/AIDS patients, and we identified age older than 50 years, low body mass index, and a treatment based on tenofovir disoproxil fumarate as risk factors for low BMD. Low high-density lipoprotein cholesterol had a protective effect against low BMD. Among low BMD patients, patients most commonly had 4 sites with low BMD, which has been associated with fracture risk. In addition, bone changes to L1 can present before low BMD diagnosis and may be a potentially useful indicator that low BMD is developing.
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•Translating broad and feasible global priorities into clear space implementation plans at the national level is necessary.•Various benefits can be coordinated simultaneously by ...combining multiple vulnerability features in prioritization.•The 52.04% region is prioritized in all four scenarios, yielding multiple benefits when protected.•Include more conservation features beyond species diversity to avoid relying solely on it as the criterion.•Grasslands and croplands should be allowed to complement forests in collaborative management measures.
To meet the ambitious goals of the post-2020 global biodiversity framework, China’s spatial implementation plan, which will delineate which areas will be protected, requires clarity at the national level. Prioritizing biodiversity alone, especially when a single species' richness is emphasized, may lead to inadequate conservation strategies, thus making it challenging to meet the requirements of collaborative governance. Here, we provide a spatial conservation prioritization method integrating species, carbon, climate, and anthropogenic vulnerability features. As such, we identified land to prioritize in conservation efforts by constructing different conservation scenarios with different combinations of vulnerability features using Chinese terrestrial ecosystems as an example. We also analyzed the differences in the benefits of different conservation scenarios. The results showed spatial variability in the distribution of land prioritized by the various protection scenarios. The conservation scenario that combined all features best harmonized the benefits and thus avoided an imbalance in conservation caused by an undue focus on one feature. The scenarios covered 73.54% of biodiversity hotspots, 63.17% of vulnerable carbon hotspots, and 80.21% of climate hotspots. We also found that forests had a strong presence in the various configurations of prioritized land, and usually exceeded 50% of the prioritized area. Secondly, cropland accounted for a prominent proportion of prioritized land at approximately 29.72%, and ranked second only to forests. In addition, when accounting for carbon vulnerability as well, the proportion of grasslands in the prioritized land increased by about 3.35 times. This study offers valuable and citable information that may be used to support biodiversity conservation initiatives in China.
•Waterbird populations have gradually increased over the past 20 years in China’s Bohai Rim.•Five waterbird hotspots were found here.•NDVI, land cover and maximum temperature of the warmest month are ...recognized as major drivers of waterbird change.
In recent years, due to rapid economic development, the Bohai Rim has become a focus of attention. The area has abundant waterbird resources, however, the coastal wetlands in the Bohai Rim are currently under serious threat and waterbird conservation needs to be addressed urgently. Exploring the changes and main driving factors of waterbirds and conducting habitat suitability assessments for waterbirds are of great significance to regional ecology and environmental protection efforts. In this study, during the period of 2002–2021, we recorded the waterbird numbers and species in the Bohai Rim region of China. Then, we quantified the potential suitable habitats and analyzed the driving factors for waterbirds using the MaxEnt model. The results showed that the waterbird richness around the Bohai Rim increased gradually over a 20-year period, and more waterbird species were detected in wetland habitats than in other habitats. Five waterbird hotspot regions require special attention, including the Yellow River Delta Nature Reserve, Beidagang Wetland, Beidaihe National Wetland Park, Liaohe Estuary wetland and Caofeidian Wetland Park. The main driving factors of waterbird changes are the NDVI, land cover and maximum temperature in the warmest month. This study provides a reference and theoretical support for waterbird conservation and rational habitat use.
Considered as an essential measure in the application of soil seed bank (SSB) projects, the mixing of substrate and surface soil can effectively improve soil condition. This research is aimed at ...exploring the diversity characteristics of SSBs and the relationships between SSBs and soil properties.
Canonical correspondence analysis (CCA) was adopted to describe the ordination of SSBs on soil properties' gradients; multiple linear regressions were adopted to analyze the relationship between average growth height and soil properties, density and soil properties.
Experimental groups of mixed substrate (the mixture of organic and inorganic substrates) had high diversity indexes, especially the Shannon-Wiener Index compared with those of single substrate. Meanwhile, a higher number of species and increased density were also noted in those of mixed substrate. The best test group, No.16, had the highest diversity indexes with a Shannon-Wiener of 1.898, Simpson of 0.633 and Pielou of 0.717, and also showed the highest density of 14000 germinants /m2 and 21 species. In addition, an improvement of the soil's chemical and physical properties was noted when the substrates were mixed. The mixed substrate of turfy soil and perlite could effectively enhance the soil moisture content, whilst a mixed substrate of rice husk carbon and vermiculite could improve the content of available potassium (AK) and phosphorus (AP) and strengthen soil fertility. The germinated plants also reflected obvious regularities of ordination on soil factor gradients. Three distinct cluster groups were presented, of which the first cluster was distributed in an area with a relatively higher content of AK and AP; the second cluster was distributed at places with relatively higher soil moisture content; and the third cluster of plants didn't show any obvious relationship with soil physical and chemical properties. Through CCA analysis, AK and AP were considered the most important soil factors to influence the SSB, which was illustrated in regression analysis with a high correlation coefficient when dependent values were growth height and density respectively. The linear regression equations with: growth height = 142.728 - 1.514TC + 30.218AP - 5.083TN + 10.839AK + 1.234mc; density = -68.216 - 4.609TC + 9.566AP - 35.492TN + 19.779AK - 1.591mc.were established by multiple linear regression.
(1) The mixed substrates showed a greater advantage for SSBs than single substrates, both in improving the number of species, density and diversity indexes. (2) The germinated plants reflected an obvious preference to different soil conditions, which different mixed substrates could improve accordingly. (3) AK, AP were important soil factors to influence SSBs, especially in the growth of plants and density.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Purpose
The purposes of this study were to analyse the spatiotemporal variations in greenhouse gas diffusive fluxes at the sediment–water interface of sewage-draining rivers and natural rivers, and ...investigate the factors responsible for the changes in greenhouse gas diffusive fluxes.
Materials and methods
Greenhouse gas diffusive fluxes at the sediment–water interface of rivers in Tianjin city (Haihe watershed) were investigated during July and October 2014, and January and April 2015 by laboratory incubation experiments. The influence of environmental variables on greenhouse gas diffusive fluxes was evaluated by Spearman’s correlation analysis and a multiple stepwise regression analysis.
Results and discussion
Sewage-draining rivers were more seriously polluted by human sewage discharge than natural rivers. The greenhouse gas diffusive fluxes at the sediment–water interface exhibited obvious spatiotemporal variations. The mean absolute value of the CO
2
diffusive fluxes was seasonally variable with spring>winter>fall>summer, while the mean absolute values of the CH
4
and N
2
O diffusive fluxes were both higher in summer and winter, and lower in fall and spring. The annual mean values of the CO
2
, CH
4
and N
2
O diffusive fluxes at the sewage-draining river sediment–water interface were − 123.26 ± 233.78 μmol m
−2
h
−1
, 1.88 ± 6.89 μmol m
−2
h
−1
and 1505.03 ± 2388.46 nmol m
−2
h
−1
, respectively, which were 1.22, 4.37 and 134.50 times those at the natural river sediment–water interface, respectively. The spatial variation of the N
2
O diffusive fluxes in the sewage-draining rivers and the natural rivers was the most significant. As a general rule, the more serious the river pollution was, the greater the diffusive fluxes of the greenhouse gases were. On average for the whole year, the river sediment was the sink of CO
2
and the source of CH
4
and N
2
O. There were positive correlations among the CO
2
, CH
4
and N
2
O diffusive fluxes. The main influencing factor for CO
2
and N
2
O diffusive fluxes was the water temperature of the overlying water; however, the key factors for CH
4
diffusive fluxes were the Eh of the sediment and the NH
4
+
-N of the overlying water.
Conclusions
River sediment can be either a sink or a source of greenhouse gases, which varies in different levels of pollution and different seasons. Human sewage discharge has greatly affected the carbon and nitrogen cycling of urban rivers.
Because of geographical position and high carbon storage potential, coastal salt marshes are recognized as an essential component of blue carbon and play an indispensable role in regulating climate ...and reaching carbon neutrality targets. Nonetheless, accurately mapping salt marsh carbon stock on a regional scale remains challenging. The framework of mapping salt marsh carbon stock was developed by using machine learning (temporal–phenological–spatial) models, vegetation index aboveground biomass inversion models, and above/belowground biomass allometric models. Here, we employed Sentinel-2 time series images based on Google Earth Engine in combination with field survey data to produce a 10-m map of salt marsh carbon stocks in the Tianjin coastal zone (TCZ). The total and average carbon stocks of TCZ salt marsh vegetation in 2020 were approximately 6.24 × 10
3
Mg C and 45.02 Mg C/ha, respectively. In terms of vegetative species, the carbon stock was ranked by
Spartina alterniflora
(2.89 × 10
3
Mg C)
> Phragmites australis
(1.74 × 10
3
Mg C)
> Suaeda salsa
(1.61 × 10
3
Mg C). The carbon density of 3 representative salt marsh species sampled in Tianjin were calculated:
S. alterniflora
(18.63 Mg/ha)
> P. australis
(6.49 Mg/ha)
> S. salsa
(1.40 Mg/ha). The random forest algorithm shows the best performance in classifying, with an overall accuracy of 87.21%. This work created the replicable and generic technical framework for mapping carbon stocks in salt marshes, which supports blue carbon accounting and provides case support for “nature-based solutions.”
Maintaining carbon sequestration is becoming increasingly significant and challenging during coastal wetland carbon restoration. To clear the influence of water, nitrogen and salinity on soil organic ...carbon (SOC), indoor incubation experiments were carried out, where soil from wetlands with dominant vegetation of Phragmites australis and Suaeda salsa were sampled and Box-Behnken central composite design was used to maximize SOC. The results indicated that:1) water, nitrogen and salinity altered soil chemical and physical properties, then significantly affect SOC in Phragmites australis wetland, but possessed little impact on Suaeda salsa wetland. 2) Optimal condition was determined with water of − 5.49 cm, salinity of 3.52 ds/m and nitrogen of 13.40 g/m2 for the biggest SOC of 8.6 g/kg in Phragmites australis wetland, whereas in Suaeda salsa wetland, SOC reached out to 8.7 g/kg with water of − 4.09 cm, salinity of 2.51 ds/m and nitrogen of 16.61 g/m2. 3) Nitrogen and water were determining factors on SOC. In Phragmites australis wetland, SOC was substantially influenced by water, nitrogen and its interaction, while in Suaeda salsa wetland, water and nitrogen displayed no direct influence, but its interactive effect worked. 4) Quadratic models were found the most desirable to reveal connections between SOC and three factors (p < 0.05). Our finding could provide support for maintaining soil carbon sink in coastal wetland restoration management.
•Water, nitrogen and salinity could alter soil properties to influence soil organic carbon in Phragmites australis wetland.•The maximum soil carbon organic was optimized by response surface methodology.•Quadratic models were established to reveal relationships between soil organic carbon and three factors.•Nitrogen and water were determining factors, the interaction of nitrogen and water was found significant to influence soil organic carbon.
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