Northern Areas Of China Research Articles

Exploring the Spatial-Temporal Patterns, Drivers, and Response Strategies of Desertification in the Mu Us Desert from Multiple Regional Perspectives

Desertification poses a serious threat to the global ecological environment and challenges the achievement of an ecological civilization. Understanding the spatial and temporal evolution of desertification in the Mu Us Desert, a key area in northern China, is crucial for predicting regional trends and analyzing causes. This study employs quantitative methods, including remote sensing data from Landsat satellites (2000–2020), combined with multi-scale analysis and statistical models, to systematically analyze desertification trends. The analysis reveals that desertification improved significantly after 2005 due to effective human intervention and governance efforts. In particular, the eastern regions (Shaanxi Province and Inner Mongolia) showed marked improvement, while the western regions exhibited limited change. The greatest progress was seen in the reduction in high-desertification areas to moderate levels. Quantitatively, human activities contributed to a 17.3% reduction in desertification (p < 0.05), while meteorological factors were responsible for a 45.8% reduction (p < 0.05). Conversely, desertification in Ningxia worsened by 41.8% due to unsustainable land use. Additionally, spatial correlation analysis highlighted that those areas of severe desertification became more uniformly distributed over time. The key drivers influencing desertification were agricultural development, urbanization, climate warming, and vegetation coverage, with human activities playing a substantial role. Initially, agricultural factors had the strongest correlation with desertification, but over time, population growth, rising temperatures, and vegetation cover (NDVI) became more prominent. These findings offer scientific support for desertification control in the Mu Us Desert and provide methodological insights for other severely desertified regions, contributing to sustainable ecological development.

Characteristics and health risks assessment of PM2.5-bound heavy metals during winter in urban areas of northern China: A case study in Kaifeng

The health impact of heavy metals in atmospheric PM2.5 has garnered increasingly widespread attention. We have collected PM2.5 samples in a typical city (Kaifeng) within the Central Plains Urban Agglomeration in China during winter and measured the mass concentration of PM2.5-bound heavy metals. The pollution of As and Cr in the urban atmosphere requires significant attention. As PM2.5 concentrations increased, the enrichment factors (EFs) of Mn, Cu, Zn, As, and Pb also rose, suggesting a growing contribution from anthropogenic emissions. The analysis showed that the hazard quotient (HQ) for the non-heating and heating periods (HQ < 1) did not result in a cumulative non-carcinogenic health risk to humans. Regarding carcinogenic effects, As and Cr exhibit significant carcinogenic impacts on both children and adults (ELCR>1 × 10−6), indicating that the carcinogenic risks posed by As and Cr under PM2.5 exposure in Kaifeng could not be overlooked. It was found that industrial and biomass combustion are the primary sources of carcinogenic risk in Kaifeng city. From the non-heating to the heating period, the industrial carcinogenic risk increased from 37.12 % to 43.39 %, while the contribution of biomass burning remained at 25 %. This result was strongly correlated with the high proportions of heavy metal elements such as As, Mn, Pb, and Ni from the metal refinery industry. The results of this study revealed the equally important source of heavy metals, compared to coal combustion in North China Plain. In addition to residential coal combustion, industrial emissions are a major source of PM2.5-bound heavy metals in Kaifeng, contributing significantly to overall air pollution and providing a useful reference to mitigating human health risks in the area.

Effects of Different Additives and Ratios on Broom Sorghum Straw Silage Characteristics and Bacterial Communities

As a large agricultural country, China produces a large number of agricultural and sideline products while harvesting agricultural products every year. Crop straw is one of them. Broom sorghum is a traditional crop in China, which produces a large amount of straw resources every year. These straw resources are placed in the field and cannot be used efficiently. The purpose of this study was to solve the problem of straw utilization of Broom sorghum, one of the main food crops in arid and semi-arid areas of northern China. Broom sorghum is not only a nutritious food crop, its straw is also rich in crude fiber and mineral elements, which has high utilization value. However, due to the high content of lignocellulose in straw, the texture is hard, which limits its digestion and utilization efficiency as feed. In this study, the broom sorghum straw was used as the research object, and the straw raw materials were treated with Lactobacillus plantarum, cellulase and xylanase, respectively. After silage fermentation for 30 d and 60 d, the bags were opened to determine the nutritional quality, fermentation quality, microbial community structure and other indicators. The best fermentation time and additives for broom sorghum straw silage were comprehensively screened to improve the nutritional value of straw and animal production performance. The results showed that the nutritional quality of silage straw increased with the extension of fermentation time. Compared with silage straw after 30 days of fermentation, the nutritional quality and fermentation quality of straw were significantly improved after 60 days of fermentation. Lactobacillus plantarum, cellulase and xylanase could improve the silage performance of broom sorghum straw by improving the microbial community structure in straw, and the effect of cellulase was the best. When cellulase was used in straw at the standard of 20 U/g FM, the content of water-soluble carbohydrates could be significantly increased to 31.35 g/kg FM, and the concentration of lactic acid was also significantly increased to 23.79 g/kg FM. Therefore, in actual production, it is recommended to use cellulase at a dose of 20 U/g FM in broom sorghum silage and open the bag after 60 days of silage fermentation. The results of this study provided a scientific basis for the efficient utilization of broom sorghum straw as feed.

An epidemiological survey of visual impairment in rural populations aged 30 and above: the Handan Eye Study

Objective: To investigate the changes in prevalence and causes of blindness and visual impairment over six years among rural populations aged 30 and above in Yongnian County, Handan City, Hebei Province, a pilot area in northern China for blindness prevention and treatment, and to study the incidence of common blinding eye diseases. Methods: This population-based prospective cohort study included a baseline survey conducted from 2006 to 2007 using stratified cluster sampling, targeting 6 830 Han Chinese individuals aged 30 and above, with a response rate of 90.4%, and a follow-up survey conducted from 2012 to 2013 with 5 394 participants, maintaining a response rate of 85.3%. Visual impairment was defined according to World Health Organization standards as visual acuity<20/60 but ≥20/400, and blindness as visual acuity<20/400. Age-and gender-standardized prevalence rates of blindness and visual impairment, along with their 95% confidence intervals (CI), were estimated. The six-year incidence rates of primary glaucoma, age-related macular degeneration, and myopic maculopathy, along with their 95%CI, were reported. Results: At baseline, the standardized prevalence of bilateral blindness in individuals aged 30 and above was 0.6% (41/6 799) for presenting visual acuity and 0.5% (31/6 799) for best-corrected visual acuity. These rates were higher than those found in the follow-up survey, 0.5% (27/5 293) and 0.3% (17/5 276). Conversely, the standardized prevalence of bilateral visual impairment increased from 4.7% (361/6 799) and 1.0% (85/6 799) at baseline to 6.5% (355/5 293) and 1.4% (74/5 276) at follow-up, respectively. The leading cause of bilateral blindness was cataract in both baseline (13/31, 41.9%) and follow-up (7/17) surveys. Other major causes included myopic retinal degeneration (5/31, 16.1% at baseline; 2/17 at follow-up), glaucoma (3/31, 9.7% at baseline; 2/17 at follow-up), and corneal opacity (3/31, 9.7% at baseline; 2/17 at follow-up). Over six years, the incidence rates for primary glaucoma, early and late age-related macular degeneration, and myopic maculopathy in individuals aged 35 and above were 1.6% (95%CI: 1.2%-1.9%), 4.2% (95%CI: 3.8%-4.7%), 0.2% (95%CI: 0.2%-0.3%), and 0.1% (95%CI: 0.0%-0.2%), respectively. Conclusions: The prevalence of bilateral blindness in the rural population of Yongnian County, Handan City, Hebei Province, decreased over six years due to blindness prevention and treatment efforts but remained higher than in urban areas. Meanwhile, the prevalence of bilateral visual impairment increased since the baseline survey. Cataracts continued to be the primary cause of blindness, followed by myopic retinal degeneration, glaucoma, and corneal opacity.

Influence of soil organic carbon fractions on the soil priming effect under different vegetation restoration modes

AbstractThe soil priming effect is a key mechanism influencing carbon (C) cycling processes between the forest soil organic carbon (SOC) pool and the atmosphere. Different vegetation restoration modes have different SOC pool compositions, and it is not clear whether such differences affect the soil priming effect. Therefore, we selected soil from six typical vegetation restoration modes Platycladus orientalis (PO), Pinus sylvestris (PS), Quercus acutissima (QA), shrub (SH) and wasteland (WL) in the soil and rocky mountainous areas of northern China and measured the soil properties, microbial communities, microbial necromass carbon (MNC), SOC fractions and the soil priming effect. The SOC content decreased in the order of PO (21.33 g kg−1), PS (22.00 g kg−1), QA (13.67 g kg−1), SH (13.33 g kg−1) and WL (10.33 g kg−1), and the trends of the mineral‐associated organic carbon (MAOC) and fungal necromass carbon (FNC) content were the same as those of the SOC content. The soil priming effect was greater in both forests and shrublands than in wastelands, with the greatest effect occurring in PO forests, where the soil priming effect reached 159.91 mg CO2‐C kg−1 soil after 30 days of incubation, which was 1.4 times greater than that in WL. The soil priming effect was mainly determined by the difference in MAOC content. In addition, the soil C/N ratio and bacterial community diversity also indirectly affected the soil priming effect by influencing the soil MNC and SOC fractions. Overall, afforestation increased the SOC content, fungal necromass contribution and mineral conservation, increasing the soil priming effect. This theoretical foundation supports the enhancement of SOC sequestration capacity by implementing various modes of vegetation restoration in the future.

Decoupling the effects of near-surface characteristic change on soil roughness in a dune-meadow cascade ecosystem

As an important indicator of ecological restoration, soil roughness changes exhibit a synergistic evolutionary relationship with near-surface characteristics such as soil and vegetation. However, the main controlling factors for changes in soil roughness in different ecosystems are still unclear. This study was conducted to clarify the changes in soil roughness in different ecosystems and to decouple and quantify the impact of near-surface characteristics on soil roughness in the Horqin Sandy Land (China). Soil roughness was measured using the structure-from-motion (SfM) technique, showing a pattern of farmland (14.08 mm) > semi-mobile dune (12.59 mm) > meadow (6.19 mm) > woodland (5.67 mm). Redundancy analysis (RDA) results showed that the near-surface characteristics of the dune-meadow cascade ecosystem that explained soil roughness, in descending order of importance, were as follows: sand, soil moisture content (MC), silt, plant stem diameter (SD), clay, pH, soil organic matter (SOM), soil shear resistance (SC), litter thickness (LT), water-stable aggregates (WSA), litter density (LD) and bulk density (BD). Specifically, in the semi-mobile dune ecosystem, the order of total effects on soil roughness was as follows: sand (1.311) > pH (0.447) > clay (0.387). In the woodland ecosystem, SC (0.226), pH (|-0.216|), and LD (0.179) were important factors controlling soil roughness. In the farmland ecosystem, MC (0.380), LT (|-0.378|), and SOM (|-0.336|) were the main controlling factors of soil roughness. In the meadow ecosystem, silt (0.574), SOM (|-0.413|), and clay (|-0.380|) significantly influenced soil roughness. Compared to other machine learning models and stepwise regression models, the k-nearest neighbors (KNN) model could predict soil roughness changes more accurately. The findings of this research are of great significance for ecological restoration and sustainable development of the ecologically fragile areas in northern China.

Alterations in Suitable Cultivation Area for Scutellaria baicalensis under Future Climatic Scenarios in China: Geodetector-Based Prediction

The dried roots of Scutellaria baicalensis (S. baicalensis) have been widely used as a traditional medicine. Recently, climate change and human activities have caused the degeneration of its wildlife habitat. However, there is rare knowledge on the effect and interactive effect of different variables on the spatial heterogeneity of S. baicalensis and how the pattern of suitable cultivation area in China would shift in response to climate change. Based on the Geodetector and Habitat Suitability Index (HSI) method, we proposed an assessment model to identify the critical environmental variable(s) affecting the distribution of suitable cultivation area for S. baicalensis in China and to project its shift under climate change. The results showed that soil and mean annual temperature are two determining variables in its spatial heterogeneity in China. Compared to 1981–2010, future climate change may result in a decrease in its suitable area, and yet may result in an increase in the extremely suitable area (about 1.00–1.35 million km2). S. baicalensis in the southern and northwestern part of its current distribution and the southwestern part and small area of northern China may experience expansion during the 21st century, while S. baicalensis in southern China, the Huang-Huai-Hai plain, and the midwest of northwestern China may experience contractions. Meanwhile, climate warming is expected to shift its distribution northwest through an expansion at the northern (at least 84 km) and western (at least 62 km) boundary and contraction at the southern (at least 529 km) boundary, respectively. These results could provide valuable information to policy-makers for the conservation and scientific introduction of S. baicalensis.

Microplastics distribution, ecological risk and outflows of rivers in the Bohai Rim region of China - A flux model considering small and medium-sized rivers

Microplastics (MPs) pollution and its ecological risks have attracted increasing global attention. The Bohai Rim region (BRR), as the economic and population center of the entire northern China, still lacks a precise assessment of MPs pollution. Although current attention on MPs pollution mainly focuses on large rivers, small and medium-sized rivers are more numerous and more closely connected to human activities. In this study, measurement data of MPs from 11 estuaries in the BRR was collected to understand MPs distribution and ecological risk. The results indicate that the overall MPs pollution in these estuaries is still at a low level, with an average abundance of 1254.3 particles m−3. While the pollution load index (1.85) is relatively low, the potential ecological risk of PVC in some area (S8, EPVC = 1433.78, III) warrants further attention. Then we integrated data from 22 relevant rivers (covering all size rivers) in this region from the literature to fit a MPs flux model and assessed the MPs outflow from the four provinces and cities in the region. A strong correlation is achieved between modeled estimates and field measurements (r2 = 0.74), which can well estimate the river MPs outflows in northern China such as the Nanfei River. The MPs outflow from the four provinces (cities) is calculated to be 123.235 (range 44.415–242.314) T year−1, of which Shandong accounted for >80 % (104.066 T year−1). The small and medium-sized rivers accounted for 47 % (58.08 T year−1), whose contribution to MPs outflows should not be underestimated. This study can help us to accurately assess MPs pollution in different coastal areas in northern China, benefiting the formulation of precise control measures and policies for marine MPs pollution.

Comprehensive dietary exposure assessment of the Chinese population to organophosphate esters (OPEs): Results of the sixth China total diet study

Organophosphate esters (OPEs) are emerging pollutants, while data on their occurrence in foods and human dietary intake are limited. Based on the 6th China total diet study conducted in 2016–2019, this study implemented a comprehensive survey of OPEs in plant-derived foods of cereals, potatoes, legumes, fruits, vegetables, and further assessed dietary exposure from both plant- and animal-derived food. The sum concentrations of 15 OPEs in the plant-derived samples ranged from 0.567 to 106 ng/g ww. 2-Ethylhexyl diphenyl phosphate (EHDPP) (median: 1.14 ng/g ww) had the highest level in plant-derived foods, with a proportion of 35.6% in the total median OPEs. Regional distribution analysis showed a higher contamination of OPEs in plant-derived food from northern area of China. Estimated dietary intakes (EDIs) of ∑OPEs for Chinese population were from 109 ng/kg bw/day in Beijing to 1164 ng/kg bw/day in Gansu province, with mean and median of 296 and 222 ng/kg bw/day, respectively. Although animal-derived foods had higher levels of OPEs, plant-derived foods, specifically cereals, was the major source of dietary OPE intake. The EDIs were much lower than reference doses, which suggested the intakes of OPEs via food consumption could not cause significant health risks to the Chinese population at present.

Dynamic trends in maize diseases and pests across six regions in China over two decades

Maize production faces persistent threats from maize diseases and pests (MDPs) throughout its growth cycle, posing substantial risks to food security. However, understanding the spatio-temporal dynamics of MDPs occurrences on a regional scale has remained elusive due to a lack of continuous observation data. This study curated a comprehensive dataset spanning two decades, from 1999 to 2018, across six key maize planting regions in China [Spring sown area in Northern China (1-NC), Summer sown region in Huang-Huai-Hai Plain (2-HHP), Southwest Mountain Maize Region (3-SM), Southern Hilly Maize Region (4-SH), Northwest Irrigated Maize Region (5-NI), and Maize Region in Qinghai-Tibet Plateau (6-QTP)]. The average extent of MDP occurrence in 1-NC and 2-HHP exceeded that in other regions over the two-decade period. Furthermore, the occurrence of MDPs exhibited a substantial increase in 1-NC, 2-HHP, 3-SM, 4-SH, and 5-NI over the same period. Meanwhile, the average occurrence intensity of MDPs in 2-HHP surpassed that in other regions. Notably, maize leaf blight and the Asian maize borer emerged as predominant diseases and pests in 1-NC, 2-HHP, 3-SM, 4-SH, and 5-NI. A bivariate trend analyses highlighted a notable increase in the species count for both the extent and intensity of MDP occurrences, including double-spotted leaf beetle in 1-NC, and cotton bollworm in 2-HHP. This extensive, long-term analysis offers a foundation for devising comprehensive strategies for MDP control on a national scale, enabling the formulation of tailored forecasting and control measures across six planting regions.

Study on the Ecological Emotions in Mongolian Desert Folk Songs

Inner Mongolia is the largest and most diverse ecological functional area in northern China. Mongolian folk songs often express gratitude for nature, praise nature, reflect on life, promote ecological balance, and highlight the harmonious coexistence of humans and nature. This paper analyzes 553 folk songs from the collection Five Hundred Mongolian Folk Songs, focusing on the "ecological emotions" embodied in the desert folk songs that hold a significant position in Mongolian folk music. The study explores the mechanisms of these ecological emotions, their practical significance, and the role of Mongolian folk songs in ecological protection, emphasizing the contemporary relevance of the ecological culture reflected in these songs.

Baseline load characteristics of transitioning to air-to-air heat pump electric heating in rural areas of northern China

Baseline load characteristics of transitioning to air-to-air heat pump electric heating in rural areas of northern China

Distributed multienergy and low-carbon heating technology for rural areas in northern China

In the context of China's “double carbon” policy and “rural revitalization” strategy, clean and low-carbon heating in rural areas of the northern China has become a key problem that needs to be urgently addressed. Practice has proved that “coal-to-gas” and “coal-to-electricity” projects have various limitations, such as high operating cost, high carbon emission, and high cost of distribution network upgrade, making them unsuitable for nationwide promotion. To address this issue, this research proposes a distributed multienergy and low-carbon heating (DMLH) system, which integrates the photovoltaic power generation, combined heat and power (CHP) system, heat storage, and newly developed multisource efficient heat pump (MEHP). The MEHP operates by simultaneously absorbing heat from air and waste heat sources of the CHP generation, providing a stable and efficient heat output. The multienergy complementary operating strategy of the DMLH system has been presented, considering variations of heating demand and environmental temperature. Comprehensive case studies were performed under typical and extremely cold winter scenarios to examine the effectiveness of the DMLH system. Simulation results revealed that 66.7 % of the operating cost can be reduced by the proposed system in typical scenario and the heat supply stability of MEHP has been considerably enhanced compared to a single-stage heat pump system. Furthermore, the DMLH system has low-level requirement of distribution network capability, which is conducive to promotion in the rural areas of northern China.

Assessment of Ecological Quality and Analysis of Influencing Factors in Coal-Bearing Hilly Areas of Northern China: An Exploration of Human Mining and Natural Topography

The Changhe Basin is located in the earth–rock mountainous area in southeastern Shanxi, China, and represents a characteristic northern coal-bearing hilly area. The terrain is complex, and the area is rich in coal mines. It plays an indispensable role in maintaining ecological balance and sustainable development in North China. To investigate the changes in ecological quality in the Changhe Basin, as well as the impact of human mining activities and natural topography on ecological quality, this study constructs the Remote Sensing Ecological Index (RSEI) based on Landsat remote sensing images from 2001, 2008, 2015, and 2022, undertaking an analysis of the spatial–temporal distribution characteristics of the ecological quality and its changing trends over the past 20 years. Additionally, spatial autocorrelation distribution features are revealed using Moran’s I. The exploration extends to examining the relationship between mining activities and the surrounding ecological quality. Subsequently, we study the relationship between Topographic Wetness Index (TWI) and RSEI. The results indicate the following: (1) On the temporal scale, the average proportion of RSEIs categorized as excellent and good from 2001 to 2022 is 46.78%. Types showcasing stable ecological conditions average 52.49%. The level of overall ecological quality of the basin has remained consistently high. On the spatial scale, the western part of the Changhe River, particularly in mountainous areas, exhibits higher ecological quality. Poorer areas concentrate in Chuandi Town in the southwestern part, and are significantly impacted by mining activities. The eastern region manifests areas undergoing either rapid or gradual degradation. (2) The four-phase Moran index results reveal a robust positive correlation in the spatial distribution of ecological quality within the basin. High–High and Low–Low clusters dominate, while High–Low and Low–High distributions are scattered. (3) Mining activities exert a discernible impact on the surrounding ecological quality. As the distance from the buffer zone outside the mining area increases, RSEI gradually decreases. The impact level exhibits an initial increase and subsequent decrease from 2001 to 2022.

Coupling effects of building-vegetation-land on seasonal land surface temperature on street-level: A study from a campus in Beijing

The land surface temperature (LST) of urban streets is significantly influenced by the surrounding urban environment. In the cold areas of northern China, this influence exhibits a seasonal pattern. Currently, in areas with noticeable seasonal variations, the coupling effects of urban elements on the annual stability of street LST remain unclear. This study developed a new metric, Normalized Winter-Summer Land Surface Temperature Difference, to measure the year-round LST stability of campus streets. Three key urban elements affecting street-level LST in winter and summer were identified: building, vegetation, and land. The influencing characteristics for winter and summer LST were quantified and ranked respectively. The study reveals that the green space ratio dominates summer LST, while fraction vegetation coverage, leaf area index and average building height dominate winter LST. We found that morphological characteristics of buildings and vegetation cannot fully explain the impact of the urban physical environment on street-level LST. For winter street LST studies, greater emphasis should be placed on non-morphological characteristics and land. Based on the impact mechanisms and critical thresholds of key features in winter and summer, this study establishes an interpretable spatial classification method. By assigning seasonal weights to influencing features, it provides comprehensive design strategies that consider both winter and summer features to enhance annual LST stability and climate resilience in urban spaces facing extreme meteorological conditions.

Moss differentiating the fluxes and sources of nitrogen deposition between 1984 and 2021 in a mountain area of Northern China

Anthropogenic reactive nitrogen (N) deposition has increased significantly since the industrial revolution. Northern China has become a global hotspot for N deposition. However, few studies have been conducted to quantify the historical changes of atmospheric N deposition fluxes and source contributions in Northern China.By investigating N contents and δ15N values of mosses at Mount Tai (Northern China) in 1984 and 2021, we reconstructed fluxes and source contributions of wet inorganic N deposition and evaluated their historical changes.Compared with 1984, moss N contents (from 1.7 ± 0.3% to 2.1 ± 0.4%) showed a significant increase in 2021, which was mainly attributed to a significant increase in nitrate N deposition fluxes at Mount Tai. Moss δ15N values (from −5.9 ± 0.9‰ to −5.2 ± 2.4‰) showed a slight increase from 1984 to 2021 at Mount Tai. The importance of combustion-related NH3 (including vehicle exhaust, coal combustion, and biomass burning) in 2021 (51.2%) were higher than those in 1984 (43.9%), while the importance of volatilization NH3 sources (including waste and fertilizers) in 2021 (48.8%) were lower than those in 1984 (56.1%). It was fossil-fuel NOx (from vehicle exhaust and coal combustion) (54.1%) rather than non-fossil fuel NOx (from biomass burning and microbial N cycles) (45.9%) dominated NOx emissions in both 1984 and 2021. Our results revealed significant contributions of combustion-related NH3 and fossil-fuel NOx sources emissions to the elevation of N deposition at Mount Tai in Northern China, which are beneficial for mitigating N emissions and conducting ecological benefit assessments in Northern China.

Greenhouse covering cultivation promotes chlorophyll accumulation of tea plant (Camellia sinensis) by activating relevant gene expression and enzyme activity

BackgroundThe tea plant (Camellia sinensis (L.) O. Kuntze) is one of the most economically important woody crops. Plastic greenhouse covering cultivation has been widely used in tea areas of northern China. Chlorophyll is not only the crucial pigment for green tea, but also plays an important role in the growth and development of tea plants. Currently, little is known about the effect of plastic greenhouse covering cultivation on chlorophyll in tea leaves.ResultsTo investigate the effect of plastic greenhouse covering cultivation on chlorophyll in tea leaves, color difference values, chlorophyll contents, gene expression, enzyme activities and photosynthetic parameters were analyzed in our study. Sensory evaluation showed the color of appearance, liquor and infused leaves of greenhouse tea was greener than field tea. Color difference analysis for tea liquor revealed that the value of ∆L, ∆b and b/a of greenhouse tea was significantly higher than field tea. Significant increase in chlorophyll content, intracellular CO2, stomatal conductance, transpiration rate, and net photosynthetic rate was observed in greenhouse tea leaves. The gene expression and activities of chlorophyll-metabolism-related enzymes in tea leaves were also activated by greenhouse covering.ConclusionThe higher contents of chlorophyll a, chlorophyll b and total chlorophyll in greenhouse tea samples were primarily due to higher gene expression and activities of chlorophyll-metabolism-related enzymes especially, chlorophyll a synthetase (chlG), pheophorbide a oxygenase (PAO) and chlorophyllide a oxygenase (CAO) in tea leaves covered by greenhouse. In general, our results revealed the molecular basis of chlorophyll metabolism in tea leaves caused by plastic greenhouse covering cultivation, which had great significance in production of greenhouse tea.

Regional difference and prevention strategy of farmland erosion induced by extreme rainstorms in the Loess area and Rocky mountain area of Northern China

AbstractElucidating the mechanism of soil erosion caused by extreme rainstorms could improve agroecosystems' resilience to the extreme climate. However, less attention has been paid to the regional difference of soil erosion during extreme rainstorms through multiple field investigations. Using six field surveys of extreme rainstorms, soil erosion and its driving mechanism were investigated on farmland in the Loess area and the Rocky mountain area. Conclusions are as follows: (1) Farmland was severely eroded in comparison with abandoned land and forest–grass land. The erosion modulus of farmland in the Loess area (51 606.51 t/km2) was greater than that in the Rocky mountain area (2582.75 t/km2). (2) In both the Loess area and the Rocky mountain area, the main erosion types on sloped cropland and terraced land were rills/gullies and embankment failure, respectively. Terracing is an appropriate measure that can effectively control farmland erosion in rainstorm events. (3) Concentrated flow is a major driver of soil erosion, with nearly all rills/gullies occurring in the flow paths. Drainage measures can prevent the formation of concentrated flow, weakening rills/gullies erosion in farmland. (4) Building bio‐embankment, planting high‐coverage crops, and implementing local protection measures could reduce the farmland erosion influenced by extremely heavy rainfall. Combining drainage and agronomic measures is the common strategy to combat extreme rainstorm events for reducing farmland erosion in the two regions. These results can be applied to improve the ability of agricultural systems to cope with extreme rainstorms.

Mapping Foliar C, N, and P Concentrations in An Ecological Restoration Area with Mixed Plant Communities Based on LiDAR and Hyperspectral Data

Interactions between carbon (C), nitrogen (N), and phosphorus (P), the vital indicators of ecological restoration, play an important role in signaling the health of ecosystems. Rapidly and accurately mapping foliar C, N, and P is essential for interpreting community structure, nutrient limitation, and primary production during ecosystem recovery. However, research on how to rapidly map C, N, and P in restored areas with mixed plant communities is limited. This study employed laser imaging, detection, and ranging (LiDAR) and hyperspectral data to extract spectral, textural, and height features of vegetation as well as vegetation indices and structural parameters. Causal band, multiple linear regression, and random forest models were developed and tested in a restored area in northern China. Important parameters were identified including (1), for C, red-edge bands, canopy height, and vegetation structure; for N, textural features, height percentile of 40–95%, and vegetation structure; for P, spectral features, height percentile of 80%, and 1 m foliage height diversity. (2) R2 was used to compare the accuracy of the three models as follows: R2 values for C were 0.07, 0.42, and 0.56, for N they were 0.20, 0.48, and 0.53, and for P they were 0.32, 0.39, and 0.44; the random forest model demonstrated the highest accuracy. (3) The accuracy of the concentration estimates could be ranked as C &gt; N &gt; P. (4) The inclusion of LiDAR features significantly improved the accuracy of the C concentration estimation, with increases of 22.20% and 47.30% in the multiple linear regression and random forest models, respectively, although the inclusion of LiDAR features did not notably enhance the accuracy of the N and P concentration estimates. Therefore, LiDAR and hyperspectral data can be used to effectively map C, N, and P concentrations in a mixed plant community in a restored area, revealing their heterogeneity in terms of species and spatial distribution. Future efforts should involve the use of hyperspectral data with additional bands and a more detailed classification of plant communities. The application of this information will be useful for analyzing C, N, and P limitations, and for planning for the maintenance of restored plant communities.

Simulated phase state and viscosity of secondary organic aerosols over China

Abstract. Secondary organic aerosols (SOAs) can exist in liquid, semi-solid, or amorphous solid states. Chemical transport models (CTMs), however, usually assume that SOA particles are homogeneous and well-mixed liquids, with rapid establishment of gas–particle equilibrium for simulations of SOA formation and partitioning. Missing the information of SOA phase state and viscosity in CTMs impedes accurate representation of SOA formation and evolution, affecting the predictions of aerosol effects on air quality and climate. We have previously developed a parameterization to estimate the glass transition temperature (Tg) of an organic compound based on volatility and to predict viscosity of SOA. In this study, we apply this method to predict the phase state of SOA particles over China in summer of 2018 using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). The simulated Tg of dry SOA (Tg,org) agrees well with the value estimated from ambient volatility measurements at an urban site in Beijing. For the spatial distributions of Tg,org, simulations show that at the surface the values of Tg,org range from ∼287 to 305 K, with higher values in northwestern China, where SOA particles have larger mass fractions of low-volatility compounds. Considering water uptake by SOA particles, the SOA viscosity shows a prominent geospatial gradient in which highly viscous or solid SOA particles are mainly predicted in northwestern China. The lowest and highest SOA viscosity values both occur over the Qinghai–Tibet Plateau, where the solid phase state is predicted over dry and high-altitude areas and the liquid phase state is predicted mainly in the south of the plateau with high relative humidity during the summer monsoon season. Sensitivity simulations show that, including the formation of extremely low-volatility organic compounds, the percent time that a SOA particle is in the liquid phase state decreases by up to 12 % in southeastern China during the simulated period. With an assumption that the organic and inorganic compounds are internally mixed in one phase, we show that the water absorbed by inorganic species can significantly lower the simulated viscosity over southeastern China. This indicates that constraining the uncertainties in simulated SOA volatility distributions and the mixing state of the organic and inorganic compounds would improve prediction of viscosity in multicomponent particles in southeastern China. We also calculate the characteristic mixing timescale of organic molecules in 200 m SOA particles to evaluate kinetic limitations in SOA partitioning. Calculations show that during the simulated period the percent time of the mixing timescale longer than 1 h is &gt;70 % at the surface and at 500 hPa in most areas of northern China, indicating that kinetic partitioning considering the bulk diffusion in viscous particles may be required for more accurate prediction of SOA mass concentrations and size distributions over these areas.