Southern Regions Of China Research Articles

Air Quality Forecast by Statistical Methods: Application to Portugal and Macao.

Air pollution is a major concern issue for most countries in the world. In Portugal and Macao, the values of nitrogen dioxide (NO2), particulate matter (PM) and ozone (O3) are frequently above the concentration thresholds accepted as “good air quality.” Portugal follows the European Union (EU) legislation (Directive 2008/50/EC) on air quality and Macao the air quality guidelines (AQG) from the WHO. Air quality forecasts are very important mitigation tools because of their ability to anticipate pollution events, and issue early warnings, allowing to take preventive measures and reduce impacts, by avoiding exposure. The work presented here refers to the statistical forecast of air pollutants for three regions: Greater Lisbon Area, Madeira Autonomous Region (both located in Portugal), and Macao Special Administrative Region (in Southern China). The presented statistical approach combines Classification and Regression Tree (CART) and multiple regression (MR) analysis to obtain optimized regression models. This consolidated methodology is now in operation for more than a decade in Portugal, and is subject to regular updates that reflect the ongoing research and the changes in the air quality monitoring network. Recently, the same methodology was applied to Macao in collaboration with the Macao Meteorological and Geophysical Bureau (SMG). Here, a statistical approach for air quality forecasting is described that has been proven to be successful, being able to forecast PM10, PM2.5, NO2, and O3 concentrations, for the next day, with a good performance. In general, all the models have shown a good agreement between the observed and forecasted concentrations (with R2 from 0.50 to 0.89), and were able to follow the concentration evolution trend. For some cases, there is a slight delay in the prediction trend. Moreover, the results obtained for pollution episodes have proven that statistical forecast can be an effective way of protecting public health.

Quantitative Characterization for Pore Connectivity, Pore Wettability, and Shale Oil Mobility of Terrestrial Shale With Different Lithofacies—A Case Study of the Jurassic Lianggaoshan Formation in the Southeast Sichuan Basin of the Upper Yangtze Region in Southern China

Some major hydrocarbon-bearing basins are rich in shale with terrestrial facies in China, which may provide abundant terrestrial shale oil and gas resources. This work studied the Jurassic Lianggaoshan Formation in the Southeast Sichuan Basin of the upper Yangtze Region. Core samples were chosen for the total organic carbon content and mineral composition analyses to classify shale lithofacies. Afterward, pore connectivity, pore wettability, and shale oil mobility with different lithofacies were characterized by spontaneous imbibition, nuclear resonance, and centrifugation. Conclusions are as follows: the pore connectivity of organic-rich clay shale was mostly between moderate to good with oil-prone wettability and high mobile oil saturation. The organic-rich mixed shale has moderate to good pore connectivity, water-prone wettability, and the highest mobile oil saturation. Organic matter–bearing clay shale has bad to moderate pore connectivity. Meanwhile, its pore wettability covers oil wetting, mixed wetting, oil-prone wetting, and water-prone wetting. Its mobile oil saturation was moderate. Regarding organic matter–bearing mixed shale, the pore connectivity was bad to moderate with mixed-wetting pore wettability and moderate mobile oil saturation.

Research on the Occurrence State of Methane Molecules in Postmature Marine shales—A Case Analysis of the Lower Silurian Longmaxi Formation Shales of the Upper Yangtze Region in Southern China

The Yangtze region in southern China is endowed with abundant marine shale gas. Methane molecules exist in either adsorption state or free state in postmature marine shales, depending on the components of shales. In this study, the core samples of the selected well in the Lower Silurian Longmaxi Fm. shales from the Sichuan Basin, upper Yangtze region, southern China, were taken as study objects. We carried out TOC content, organic matter maturity, mineral component, and core gas content analyses and isothermal adsorption, FIB-SEM, and FIB-HIM experiments to analyze the occurrence state of methane molecules in postmature marine shales. The conclusions are as follows: most methane molecules exist in the organic matter pores of the postmature marine shales, and only a small amount of them exist in clay mineral pores. The organic matter pores in organic-rich shales are large in number with excellent roundness and are well connected, with large pores covering small ones. Thus, abundant free gas can be stored in the organic matter pores and pore throats, making it possible to densely and continuously adsorb methane molecules with a relatively large adsorption space. The flake-shaped clay minerals have a small number of pores with low roundness. Among the three clay minerals in postmature marine shales of the Longmaxi Fm., the I/S mixed layer offers certain reservoir spaces for adsorbed and free gases and chlorite stores a little adsorbed gas and little free gas, while illite hardly stores the adsorbed gas but contains a little free gas.

Spatial-Temporal Variation in Paddy Evapotranspiration in Subtropical Climate Regions Based on the SEBAL Model: A Case Study of the Ganfu Plain Irrigation System, Southern China

The surface energy balance algorithm for land (SEBAL) is a commonly used method for estimating evapotranspiration (ET) at a regional scale; however, the cloudy and rainy characteristics of subtropical monsoon regions pose a greater challenge for estimating paddy field ET based on remote sensing technology. To this end, a typical subtropical climate region in southern China (Ganfu Plain irrigation system) was selected as the study area. Subsequently, we evaluated the applicability of the SEBAL model for estimating the ET of paddy fields at the daily scale; derived the interannual variation (2000–2017) characteristics of early, middle, and late rice ET; and finally analyzed the spatial distribution patterns of rice in different hydrological years. The results demonstrated that: (1) the SEBAL model estimated ET accurately on a daily scale, with R2, NSE, and RMSE values of 0.85, 0.81, and 0.84 mm/day, respectively; (2) the ET of paddy fields in the irrigated area was higher in July and August and the interannual trend of ET of early rice was not obvious, with a declining trend observed in middle rice and late rice from 2000 to 2009, which was followed by an increasing trend from 2009 to 2017; and (3) variations in the spatial distribution of ET were significant for early and late rice at different precipitation levels and less obvious for middle rice in wet years but significant in dry years. Overall, this study verified the applicability of the SEBAL model for estimating ET in paddy fields in subtropical regions and provided a basis and reference for the rational allocation of water resources at a regional scale.

Brominated flame retardants (BFRs) in sediment from a typical e-waste dismantling region in Southern China: Occurrence, spatial distribution, composition profiles, and ecological risks

Our study evaluated the current occurrence, composition, and spatial distribution of eight congeners of polybrominated diphenyl ethers (PBDEs) and seven novel brominated flame retardants (NBFRs) in sediment from Guiyu, a typical e-waste dismantling region in China. PBDEs levels ranged from 0.345 to 401,000 ng/g dw and NBFRs levels ranged from 0.581 to 73,100 ng/g dw. Almost all sediment samples contained high levels of BDE-209 and DBDPE, and the ratio of DBDPE/BDE-209 in sediments ranged from 0.0814 to 2.80 (mean: 0.879). The concentration and composition profiles for BFRs in sediments from both mainstream and tributaries of two major rivers in Guiyu reach (and adjacent downstream locations) differed significantly from those far from Guiyu town. Whereas the high presence of BFRs in Guiyu reflected the historical crude e-waste dismantling activities in the region; the locations far from Guiyu town were likely to receive BFRs from atmospheric deposition, not originated from the region, as BFRs in water-sediment are known to be able to migrate a limited distance along the river. Ecological risk assessment revealed that the low brominated congeners of PBDEs and BDE-209 posed an unacceptable risk to the sedimentary life at multiple locations. Our results updated our knowledge of BFRs contamination in Guiyu, suggesting the necessity of continuous source monitoring, control procedures, and sediment cleanup for BFRs.

Bacteria Associated With Phaeocystis globosa and Their Influence on Colony Formation.

Phaeocystis globosa (P. globosa) is one of the dominant algae during harmful algal blooms (HABs) in coastal regions of Southern China. P. globosa exhibits complex heteromorphic life cycles that could switch between solitary cells and colonies. The ecological success of P. globosa has been attributed to its colony formation, although underlying mechanisms remain unknown. Here, we investigated different bacterial communities associated with P. globosa colonies and their influence on colony formation of two P. globosa strains isolated from coastal waters of Guangxi (GX) and Shantou (ST). Eight operational taxonomic units (OTUs) were observed in ST co-cultures and were identified as biomarkers based on Linear discriminant analysis Effect Size (LEfSe) analysis, while seven biomarkers were identified in P. globosa GX co-cultures. Bacterial communities associated with the P. globosa GX were more diverse than those of the ST strain. The most dominant phylum in the two co-cultures was Proteobacteria, within which Marinobacter was the most abundant genus in both GX and ST co-cultures. Bacteroidota were only observed in the GX co-cultures and Planctomycetota were only observed in the ST co-cultures. Co-culture experiments revealed that P. globosa colony formation was not influenced by low and medium cell densities of Marinobacter sp. GS7, but was inhibited by high cell densities of Marinobacter sp. GS7. Overall, these results indicated that the associated bacteria are selected by different P. globosa strains, which may affect the colony formation and development of P. globosa.

Third-generation sequencing: A novel tool detects complex variants in the α-thalassemia gene

ObjectiveThalassemia is a monogenic disorder with a high carrier rate in the southern region of China. Most laboratories currently follow the protocol of testing hematologic indicators in individuals with positive hematologic indicators and then using the hot-spot mutation test kit. A novel thalassemia gene test is performed if there is a mismatch between the hematology and hot-spot mutation test results. However, due to the large population in southern China, some individuals carry complex α-globin gene cluster (CAGC) variants in NG_000006.1, which are difficult to detect using conventional thalassemia genetic analysis protocols, leading to missed or false genetic test results for individuals carrying these complex α-globin gene cluster variants. When an individual carries a complex α-thalassemia gene variant, and an individual carries a β- thalassemia gene variant, there may be clinical symptoms that might complicate clinical consultation and prenatal diagnosis if not accurately detected. Third-generation sequencing (TGS) enables long-read single-molecule sequencing with high detection accuracy, and long-length DNA chain reads in high-fidelity reads mode. TGS can be used to analyze high homology and rich GC DNA sequences. ResultsFour samples that showed abnormalities in the thalassemia genetic test were studied using TGS, revealing that they carried genotypes with complex α-globin gene cluster variants, one of which was a complex variant αα anti3.7 α anti3.7 α 17.2. ConclusionsTGS detects complex α-globin gene cluster variants. This study may provide a reference protocol for the use of TGS for the detection of complex α-globin gene cluster variants. TGS can reveal individuals with complex α-thalassemia genotypes in the population and improve the accuracy of genetic counseling and prenatal diagnosis.

Response of spatiotemporal variability in soil pH and associated influencing factors to land use change in a red soil hilly region in southern China

Abnormal changes in soil acidity and alkalinity impact regional food security and sustainable development of terrestrial ecosystems, especially under land use change. The regulation of soil acidity and alkalinity requires a clear understanding of soil pH variability and its influencing factors under regional land use change. This study explored the patterns of soil pH variability under land use change between 1984 and 2018 in a red soil hilly region (Xunwu County, Jiangxi Province) in southern China. We identified the key factors influencing regional spatiotemporal variability in soil pH and analyzed the response of soil pH variability to land use change. The results showed that the mean pH values of surface soil samples in 1984 (n = 595) and 2018 (n = 580) were 5.35 and 5.05, respectively. The soil pH change between the two periods ranged from −0.91 to 0.32, with a mean value of −0.30. In total, 91.72% of the study area showed an acidification trend from 1984 to 2018. The spatiotemporal variability in soil pH was influenced by elevation, slope, distance to rivers, changes in distance to roads, and changes in the nitrogen fertilizer application rate. The main land use conversion modes were cropland and forest transferred to garden and other land. The soil pH decreased in 15 of 16 conversion modes of cropland land, garden, forest, and other land, whereas a pH increase of 0.32 occurred under conversion from cropland to garden. Changes in distance to roads, changes in the nitrogen fertilizer application rate, and slope played a dominant role in soil pH variability under land use change. This study provides fundamental data for the formulation of soil acidity and alkalinity control measures, which in turn contributes to regional improvement of agricultural production stability and sustainable development.

Influence of Organic Matter on Gas-Bearing Properties and Analysis of Sedimentary Mechanism of Organic Matter Enrichment: A Case Study on the Yangtze Region of Southern China during the Early Cambrian

Shale gas exploration requires studies on the enrichment mechanism of sedimentary organic matter. The Lower Cambrian shale is taken as a study object to analyze the effect of organic matter on gas content using TOC content and porosity analyses, isothermal adsorption experiments, and FIB-HIM scanning electron microscopy observations. Then, we selected typical wells to determine the presence of excessive silica in the siliceous minerals by quantitative calculations. Besides, we analyzed the genesis of excessive siliceous minerals using elements including Al, Fe, and Mn, thus speculating the controlling factors of the redox environment and biological productivity. Results show that total organic carbon content controls the content of free and adsorbed gas, while shale gas mainly exists in organic pores and is developed in large numbers and with high roundness, showing the characteristics of “small pores inside big pores.” In the Lower Yangtze region during the Early Cambrian, the excessive siliceous minerals were of hydrothermal origin, and there were frequent hydrothermal activities due to its closeness to plate boundaries. These activities can intensify the reducibility of the waterbody’s bottom and improve the biological productivity on its surface, resulting in the enrichment of this matter. Most excessive silicon in this region is biogenic, while only a small part is of hydrothermal and biogenic mixed origin. The enclosed waterbody of the Upper Yangtze region was far from plate boundaries and close to the semiclosed “gulf,” resulting in its delamination. The waterbody’s surface was abundant with oxygen, thus increasing the biological productivity, while the high reducibility at the waterbody’s bottom was conducive to preserving sedimentary organic matter.

Comparison of feature selection methods for mapping soil organic matter in subtropical restored forests

• Filter, wrapper, embedded and ensemble feature selection approaches (FS) were evaluated. • The proposed ensemble FS incorporates ten individual selectors to identify top significant variables. • Ensemble FS produced the highest predictive variable subset for mapping SOM. • XGBoost outperformed RF in mapping SOM in subtropical restored forests. Mapping Soil organic matter (SOM) over a complex forest landscape is challenging due to the difficulty in selecting the most insightful variables from high-dimensional datasets in the recent explosion of geospatial-data. Feature selection (FS) is necessary to reduce data redundancy and noise as well as to achieve more reliable SOM spatial predictions. However, it is still unclear that which is most effective among various FS methods in mapping SOM. Therefore, four types of FS approaches (i.e., filter, wrapper, embedded and ensemble) were adopted to generate optimum variable subsets from an original variable dataset of 60 candidates, respectively, for mapping SOM of restored forest land in a typical subtropical region of southern China. The most used methods for each type of FS approaches were selected in this study, including three filters (Chi-square, InfoGain and pearson correlation analysis), three wrappers (genetic algorithm, simulated annealing algorithm and support vector machine-recursive feature elimination) and three embedded methods (Boruta, random forest (RF) and extreme gradient boosting (XGBoost)), as well as an ensemble method (robust rank aggreg algorithm (RRA)). Meanwhile, the RF and XGBoost models were applied with a 10-fold cross-validation method to compare the relative advantages of the different FS methods in SOM mapping, by utilizing the correlation coefficients R 2 between observed and predicted values and predicting errors of root mean square error (RMSE). The results show that the SOM prediction accuracies with optimized variable subsets generated by the different FS methods are better than those with full variables, yet the improvements of prediction performance are different among the four types of FS approaches. The ensemble method (RRA) is superior to the other three types of approaches with an average RMSE reduction of 9.16% comparing to that without using FS methods, followed by wrapper and embedded methods which obtained the average RMSE reduction by 7.81%, 7.32%, respectively, and the filter methods are the weakest in the RMSE reduction with slight decreases of 4.32%. The XGBoost model achieved a better performance in predicting SOM than the RF model regardless of input variables, and the XGBoost model combined with RRA FS method shows the greatest potential to map SOM in the restored forest land. This study provides a reference for obtaining more parsimonious and robust variable sets from the available big geo-data freely for soil mapping in other areas.

Periconceptional folic acid use prevents both rare and common neural tube defects in China.

Neural tube defects (NTDs) encompass a variety of distinct types. We assessed if the preventive effect of folic acid (FA) varied by NTD type and infant sex. We examined all pregnancies with NTD status confirmation from a pregnancy-monitoring system in selected locations in northern and southern regions of China between 1993 and 1996. Women who took 400 μg of FA daily during 42 days after last menstrual period were considered FA users. We analyzed NTD prevalence by FA use status, NTD type, geographic region, and infant sex. Among 626,042 pregnancies, 700 were affected by an NTD. Among FA nonusers, 65 pregnancies (8.8 per 10,000) in the north and 51 pregnancies (1.2 per 10,000) in the south were affected by one of the two rare NTDs, that is, craniorachischisis, iniencephaly. FA use prevented occurrence of these two rare NTDs and reduced the prevalence of spina bifida (SB) by 78% (from 17.9 to 3.9 per 10,000) in the north and 51% (from 2.4 to 1.2 per 10,000) in the south. Among FA users, SB prevalence, including SB with high lesion level, was significantly reduced in both geographic regions. FA use reduced prevalence of anencephaly and encephalocele by 85% and 50%, respectively in the north, while it did not reduce the prevalence of these two NTDs in the south. There was a greater reduction in NTD prevalence in female than in male infants and fetuses. This is the first study to show that FA prevents the entire spectrum of NTD types.

Recombinase polymerase amplification combined with fast DNA extraction for on–spot identification of Deinagkistrodon acutus, a threatened species

This study addresses the use of recombinase polymerase amplification combined with fast DNA extraction for on–spot identification of Deinagkistrodon acutus, a snake species threatened due to over–exploitation and habitat destruction. For its conservation, an efficient species identification method is urgently neededto fight against illegal capture and trade. Fourteen individuals representing 12 snake species (including D. acutus and other snake species) were collected from mountainous regions in Southern China. Genomic DNA was extracted within five minutes by a modified alkaline lysis method. Species–specific primers for recombinase polymerase amplification (RPA) were designed based on the sequences of cytochrome C oxidase subunit I (COI) barcode region, and an optimized RPA assay system was set up. Specificity and sensitivity of the assay were checked, and the assay was validated by identifying 10 commercial Qi She crude drug samples derived from D. acutus. Under optimized RPA conditions, a distinct single band of 354 bp was amplified only for D. acutus but not for the related snake species. The entire procedure can be completed in 30 min at room temperature. Commercial Qi She crude drug identification validated effectiveness of the established assay system. Using a recombinase polymerase amplification (RPA) assay with rapid DNA extraction, we established an on–spot D. acutus identification method with good specificity and sensitivity. This method could become an efficient tool for rigorous supervision of illegal D. acutus capture and trade.

Quantitative effects of air pollution on regional daily global and diffuse solar radiation under clear sky conditions

Air pollution is one of the most important factors affecting the solar radiation reaching the earth’s surface under the clear (cloudless) sky conditions. In this work, six typical cities with serious pollution located in the north, northeast, eastern, central, southwest, and southern regions of China: Beijing, Shenyang, Shanghai, Wuhan, Wenjiang and Guangzhou were selected. The influence of air pollution on global and diffuse solar radiation (Rs and Rd) under clear sky condition was quantitatively analyzed, based on the historical daily meteorological data from January 2014 to December 2020. The results showed that the highest Rs attenuation ratio of the above six cities appeared in spring, autumn, winter, summer, autumn and winter, respectively. The largest Rd increment ratio of the six cities appeared in summer, spring, autumn, summer, autumn and spring, respectively. From 2014 to 2020, the relative attenuation of Rs caused by air pollution (AQI > 100) was largest in Beijing (6.03%), followed by Shanghai (4.21%), Wenjiang (4.15%), Shenyang (3.28%) and Wuhan (3.14%), while Guangzhou (1.32%) had the smallest relative attenuation. Additionally, the Rd relative increment was largest in Beijing (16.21%), followed by Shanghai (8.78%), Wenjiang (8.13%), Shenyang (7.76%) and Guangzhou (5.96%), while Wuhan (2.57%) had the smallest relative increment.

Molecular phylogeography and evolutionary history of the pink rice borer (Lepidoptera: Noctuidae): Implications for refugia identification and pest management

AbstractUnderstanding phylogeography, demographic dynamics as well as evolutionary forces of agricultural pests can enhance our understanding of their distribution dynamics, which is critical for developing effective control strategies. The pink rice borer (PRB), Sesamia inferens (Walker), is a destructive pest of rice that is widely distributed in Asia; however, little is known regarding its phylogeography and evolutionary history. In this study, we investigated the genetic diversity, population genetic structure and demographic history of the PRB at the scale of its whole distribution in China. Both mitochondrial and microsatellite datasets indicated that PRB individuals exhibit high levels of genetic diversity. Two large phylogeographic clusters were identified, corresponding to Northern and Southern China regions, respectively. The glacial events during the penultimate glacial period likely led to the separation of these two clusters, and parts of Northern and Southern China areas acted as independent refugia for PRB during glacial period. Two microrefugia in the Sichuan Basin and Yunnan‐Guizhou Plateau were also identified, and the PRB from Sichuan Basin could be one of the ancestral sources for PRB individuals from the Northern China lineage. Our study not only provides information that has implications for refugia identification, but also provides an example on how to reveal the phylogeography, demography history and evolutionary forces of an agriculture pest.

Integrating satellite-based passive microwave and optically sensed observations to evaluating the spatio-temporal dynamics of vegetation health in the red soil regions of southern China

ABSTRACT Attentions over the health of evergreen vegetation are increasing owing to frequently occurrence of recent disturbance events (i.e. soil erosion, logging activities, and afforestation). However, vegetation indices that characterize canopy greenness have limitations in spectral saturation for representing the growth states of densely vegetated areas, and the continuous acquisition of satellite-derived vegetation functional metrics depends on the availability of clear image observations. This study investigated the vegetation health dynamics (1993–2012) in the red soil regions of southern China using satellite observations based task-oriented metrics, including the Normalized Difference Vegetation Index (NDVI), Vegetation Water Content (VWC), and Aboveground Biomass Carbon (ABC). The results indicated that the total number of pixels with significant changes (SC) was 214, 1,186, and 794 for the NDVI, VWC, and ABC indices, respectively. More than 90% of the SC pixels in the three metrics exhibited increasing trends, which were primarily observed in mountainous areas. Pixels that exhibited a continuously declining trend were discretely distributed throughout the entire study area. Among the SC pixels, vegetation in major parts of the study area was disturbed by abrupt events. In the NDVI, VWC, and ABC, the frequency of abrupt changes increased after 2000, coinciding with the launch of the Natural Forest Conservation Program (NFCP) in 2000–2001. For regions with abrupt changes, four patterns were further observed based on the indices: the continued increases (pattern-1), sustained decreases (pattern-2), recovery growth after an initial decline (pattern-3), and significant decreases after initial growth (pattern-4). Pattern-1 appeared more frequently than the other three patterns. This study indicates that vegetation in most areas was optimally developed and exhibited a healthier tendency compared with previous growth states. Notably, the presence of an increasingly unhealthy vegetation state was observed in the northeastern region of the study area. Satellite derived datasets and synergetic use of indicators contribute to understanding the changes in the vegetation health in the entire red soil regions in southern China. Thus, this study acts as a reference for forest management and soil erosion control.

The spatio-temporal relationship between land use and population distribution around new intercity railway stations: A case study on the Pearl River Delta region, China

Recently, transit-oriented development (TOD) projects have begun to prosper around new intercity railway (ICR) stations in China. An important question is whether the ICR-based TOD could perform as expected since the regional ICR is different from urban transit on which more TOD projects base. This article utilizes a remote sensing dataset, mobile-phone location-based big data as well as web map portal data and a Geographically and Temporally Weighted Regression (GTWR) model to explore the spatio-temporal relationship between land use and the population distribution in the ICR station area. It adopts the Pearl River Delta region in southern China as a study area, which undergoes rapid urbanization and is a pioneer to adopt TOD to promote the ICR project. The research finds the following. First, the combination of remote sensing, spatial big data, web map portal data and the GTWR model efficiently reveals the underlying spatio-temporal heterogeneities of the relationship between land use and population distribution in the ICR station area. Second, compared with the existing built-up area, the newly developed land after ICR construction has a weaker correlation with population distribution in the ICR station area. Third, the locations of the ICR station areas within the urban-rural system play a significant role in determining the relationship between land use and population distribution. For example, the association of working facilities with population distribution in suburban and town ICR station areas is significantly larger than that in urban and rural ICR station areas.

Mapping the Complex Crop Rotation Systems in Southern China Considering Cropping Intensity, Crop Diversity, and Their Seasonal Dynamics

Crop rotation increases crop yield, improves soil health, and reduces plant disease. Mapping crop rotation is difficult because crop data from a single time point do not sufficiently represent the dynamics of a system. Studies have tried to map crop rotation by sequentially combining crop maps. However, this produced a large number of meaningless crop sequences, hindering the assessment of rotational benefits at regional scales. Here, we propose a crop rotation classification scheme that integrates temporal information into static crop maps and develop an innovative approach to map crop rotation. We chose a typical multiple cropping region in southern China. Given that the landscape is characterized by high crop diversity (e.g., food crops, cash crops, and permanent crops) and variable cropping intensity, our classification scheme first defines three main rotation systems, i.e., paddy, vegetable, and orchard systems, and then further divides the systems into nine subsystems according to their seasonal dynamics. Finally, we apply time series of Sentinel-1 and Sentinel-2 images to identify the systems by a hierarchical rule-based method. The map of crop rotation systems in 2020 had producer, user, and overall accuracies of 81%, 79%, and 81%, respectively. The results indicate that integrating temporal information into the classification scheme is vital to representing complex rotation systems and that remotely sensed temporal dynamics of crops are useful to characterize these systems. It also shows that crop rotation can be mapped directly rather than aggregating multiple crop layers, thus providing a new perspective for mapping and understanding crop rotation systems.

赤红壤植蔗坡地坡面径流及溶解态氮磷流失特征

为探究南方高强度、高频次降雨下赤红壤区坡耕地土壤侵蚀及氮磷养分流失的特征，基于野外径流小区原位观测试验，通过测定自然降雨下赤红壤植蔗坡地坡面径流和溶解态氮磷流失量，探讨自然降雨下甘蔗种植对赤红壤坡面径流及溶解态氮磷流失的影响。结果表明：（1）2019年和2020年，径流量分别为1111.3 m³/hm²和3269.4 m³/hm²，硝态氮（NO₃^--N）流失量分别为1.39 kg/hm²和15.60 kg/hm²，铵态氮（NH₄⁺-N）流失量分别为0.37 kg/hm²和1.02 kg/hm²，可溶性磷流失量分别为0.20 kg/hm²和0.27 kg/hm²。2019年和2020年植蔗坡地径流及溶解态氮磷流失量均集中在6月份，占流失总量的45%以上，硝态氮（NO₃^--N）是径流氮素流失的主要形式，占79%以上。此外，2019年和2020年5月至8月，侵蚀性降雨场次分别为18次和23次，侵蚀性降雨量分别为407.8 mm和668.0 mm。（2）不同侵蚀性降雨条件下，植蔗坡地溶解态氮磷流失量及其浓度波动较大，甘蔗生长前期（5-6月）溶解态氮磷流失量及其浓度呈上升趋势，而生长后期（7-8月）则呈波动下降趋势。2019年和2020年观测期侵蚀性降雨的年内分布存在明显差异，均集中在6月份，占35%以上。（3）坡面径流量与降雨量和最大30 min降雨强度呈极显著的正相关关系，同时坡面径流量与径流中硝态氮、铵态氮及可溶性磷流失量均呈极显著正相关关系。研究结果有助于明晰南方赤红壤区蔗区坡面土壤侵蚀及养分流失特征。;The characteristics of soil loss and nutrient loss in sloping land are quitely different among different areas of China, and crop patterns also have significant impacts on these indicators. The objectives of this study were as follows:1) to explore the characteristics of soil erosion and nutrient loss in sloping land with planting sugarcane of lateritic soil; and 2) to analyze the impacts of sugarcane growing stage and natural rainfall characteristics on soil erosion and nitrogen and phosphorus loss characteristics. This research based on the in-situ observation test of runoff plot and measured the loss of runoff, dissolved nitrogen, and phosphorus in sloping land with planting sugarcane. The amounts and concentrations of nitrate nitrogen (NO₃^--N), ammonium nitrogen (NH₄⁺-N), and dissolved phosphorus (DP) under individual natural rainfall during May to August in 2019 and 2020 were observed. The results showed that:(1) in 2019 and 2020, the runoffs, nitrate nitrogen (NO₃^--N), ammonium nitrogen (NH₄⁺-N), and dissolved phosphorus (DP) loss were 1111.3 m³/hm² and 3269.4 m³/hm², 1.39 kg/hm² and 15.60 kg/hm², 0.37 kg/hm² and 1.02 kg/hm², 0.20 kg/hm² and 0.27 kg/hm², respectively. The runoff and its dissolved nitrogen and phosphorus loss in sloping land with planting sugarcane under 2019 and 2020 were both concentrated in June, which accounted for more than 45%, and NO₃^--N was the main form of nitrogen loss in runoff, which accounted for more than 79% of total nitrogen loss. Besides, the times of individual erosive rainfall were 18 and 23, and the erosive rainfall amounts were 407.8 and 668.0 mm from May to August in 2019 and 2020, respectively. (2) The amounts of dissolved nitrogen and phosphorus loss and their concentrations in sloping land with planting sugarcane showed great fluctuation under different erosive rainfalls and stages of sugarcane growth. There were obvious differences in the annual distribution of erosive rainfall between observation period of 2019 and 2020, which were both concentrated in June, which accounted for more than 35% of total rainfall. In the early stage of sugarcane growth (from May to June), the losses of dissolved nitrogen and phosphorus and their concentrations showed an upward trend, while in the late stage of sugarcane growth (from July to August), they showed a fluctuating downward trend. (3) There was a significantly positive correlation between runoff and rainfall and maximum 30 min rainfall intensity, meanwhile, there was a significantly positive correlation between runoff and the loss of nitrate nitrogen (NO₃^--N), ammonium nitrogen (NH₄⁺-N), and dissolved phosphorus (DP). The results can provide a theoretical basis for clarifying the soil erosion characteristics of sloping land with planting sugarcane in the lateritic soil region of southern China.

Comment on “Multi-time scale variability of rainfall erosivity and erosivity density in the karst region of southern China, 1960–2017” by Zhu et al. (2021), “Spatial characteristics of the human factors of soil erosion at the boundary of political divisions: A spatial approach” by Meng et al. (2021), and “Environmental factors influencing spatial variability of soil total phosphorus content in a

Three similar equations of the rainfall erosivity factor from three separate studies published in Catena in 2021 and 2020 were compared and contrasted. All three studies appear to have cited the equations incorrectly because none of the equations can be found in the supporting references. This could have profound implications for the correctness of the results reported by the three studies and the interpretation of their findings.

Recognition and Usage of Sunscreen by Women in Yunnan Province, China

Purpose: In this study, we surveyed 1,325 women ranging in age from 10s to 40s and living in Yunnan province, China to examine their awareness regarding the harmfulness of ultraviolet (UV) rays, and their usage and preference of sunscreen.Methods: Questionnaires composed of a total of 22 questions were distributed using the online survey service Wenjuanxing. The data collected were analyzed through frequency analysis and crossover analysis using a statistics program.Results: Awareness that UV rays are harmful to the skin was present in 99.2% of the subjects. All age groups perceived the harmfulness of UV rays due to the same reasons, which were pigmentation, promotion of premature skin aging, and sunburn. Similarly, all age groups perceived that UV rays are harmful throughout the year.Conclusion: Awareness of the effects of UV rays helps Korean cosmetics companies to market and design sales strategies for sunscreen products in the southern region of China. This survey provided data specific to Yunnan regarding women's preferences, thereby facilitating comparative analysis with other regions in China.