Yangtze River Area Research Articles

Better Inversion of Wheat Canopy SPAD Values before Heading Stage Using Spectral and Texture Indices Based on UAV Multispectral Imagery

In China’s second-largest wheat-producing region, the mid-lower Yangtze River area, cold stress impacts winter wheat production during the pre-heading growth stage. Previous research focused on specific growth stages, lacking a comprehensive approach. This study utilizes Unmanned Aerial Vehicle (UAV) multispectral imagery to monitor Soil-Plant Analysis Development (SPAD) values throughout the pre-heading stage, assessing crop stress resilience. Vegetation Indices (VIs) and Texture Indices (TIs) are extracted from UAV imagery. Recursive Feature Elimination (RFE) is applied to VIs, TIs, and fused variables (VIs + TIs), and six machine learning algorithms are employed for SPAD value estimation. The fused VIs and TIs model, based on Long Short-Term Memory (LSTM), achieves the highest accuracy (R2 = 0.8576, RMSE = 2.9352, RRMSE = 0.0644, RPD = 2.6677), demonstrating robust generalization across wheat varieties and nitrogen management practices. This research aids in mitigating winter wheat frost risks and increasing yields.

Spatial variations and mechanisms for the stability of water use efficiency in China.

A clearer understanding of the stability of water use efficiency (WUE) and its driving factors contributes to improving water use efficiency and strengthening water resource management. However, the stability of WUE is unclear. Based on the EEMD method, this study analyses the spatial variations and mechanisms for the stability of WUE in China, especially in the National Forest Protection Project (NFPP) areas. It is found that the stable WUE was dominated by non-significant trends and increasing trends in China, accounting for 33.59% and 34.19%, respectively. The non-significant trend of stable WUE was mainly located in the Three-North shelterbelt program area, and the increasing trend of stable WUE was in Huaihe and Taihu, Taihang Mountains, and Pearl River shelterbelt program areas. Precipitation and soil moisture promoted the stable WUE in these project areas. The unstable WUE was dominated by positive reversals or negative reversals of WUE trends. The positive reversals of unstable WUE were mainly located in the Yellow River shelterbelt program areas, which was promoted by temperature and radiation, while the negative reversals of unstable WUE were mainly distributed in the Yangtze River and Liaohe shelterbelt program areas, which were mainly induced by saturation water vapor pressure difference (VPD). Our results highlight that some ecological restoration programs need to be improved to cope with the negative climate impact on the stability of WUE.

Bacterial seed endophyte and abiotic factors influence cadmium accumulation in rice (Oryza sativa) along the Yangtze River area

Cadmium (Cd) contamination in rice (Oryza sativa) is particularly problematic due to its high risk to human health. Investigating the hidden roles of seed endophytes of rice in influencing Cd accumulation is essential to comprehensively understand the effects of biotic and abiotic factors to food security. Here, the content of Cd in soils and rice (Huanghuazhan) seeds from 19 sites along the Yangtze River exhibited considerable differences. From a biotic perspective, we observed the dominant endophytic bacteria, Stenotrophomonas (7.25 %), contribute to Cd control of rice (below 0.2 mg kg−1). Partial Least Squares (PLS) analysis further suggested that Enterobacteriaceae (15.48 %), altitude and pH were found to be the strong variables that might reduce the Cd uptake of rice. In contrast, Cytophagaceae (0.58 %), latitude and mean annual air pressure had the opposite effect. In pot experiments, after respectively inoculating the isolated endophytic bacteria Stenotrophomonas T4 and Enterobacter R1, N1 (f_Enterobacteriaceae), the Cd contents in shoot decreased by 47.6 %, 21.9 % and 33.0 % compared to controls. The distribution of Cd resistant genes (e.g., czcABC, nccAB, cznA) of Stenotrophomonas, Enterobacteriaceaea and Cytophagaceae further suggested their distinct manners in influencing the Cd uptake of rice. Overall, this study provides new insights into the food security threatened by globally widespread Cd pollution.

Analysis of genetic diversity and population structure of Puccinia striiformis f. sp. tritici infers inoculum relationships from Yunnan to the middle and lower reaches of the Yangtze River

AbstractWheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is an important cereal fungal disease worldwide, including in the major wheat‐producing areas in China. In 2019, there was a widespread epidemic of the disease in the middle and lower reaches of the Yangtze River (MLRYR) area, including Zhejiang, Jiangsu, Anhui and Guangxi. However, in north‐western China, the postulated inoculum source of MLRYR, disease occurred mildly. Therefore, the origin of the Pst inoculum source for the MLRYR epidemic is still an open question. To address it, we collected 210 Pst uredinium samples from the Yangtze River basin and analysed their genetic structure with 13 pairs of simple‐sequence repeat (SSR) markers that we coupled with an upper airflow trajectory analysis. Our results suggest that the autumn inoculum sources of wheat stripe rust in MLRYR in 2019 probably came from south‐western over‐summering areas of Pst through long‐distance migration. We also found that Jingzhou and adjacent areas in Hubei Province function as an important bridge or stopover for inoculum sources.

Determining the critical threshold of meteorological heat damage to tea plants based on MODIS LST products for tea planting areas in China

Tea (Camellia sinensis (L.) Kuntze) is a daily drink in modern life throughout the world. Global warming increases the exposure of tea plants to elevated heat conditions during the summer picking period. Therefore, it is a fundamental function of the meteorological service to determine the critical temperature threshold that triggers heat damage (HD) to tea plants. In this study, MODIS daytime land surface temperature (LST) products obtained from the Aqua satellite (MYD11A1), annual land cover type products (MCD12Q1), and actual HD records were jointly used to determine the critical LST threshold resulting in HD to tea planting areas in China. An LST dataset of HD and HD-free samples was constructed based on actual HD records. The box-plot method was then used to delineate the range of LST outliers in HD to tea plants. The cumulative frequency distribution (CFD) method was adopted to determine the critical LST threshold by searching for the maximum slope of CFD within the range of LST outliers based on 2901 actual HD samples from 42 agrometeorological stations in 11 provinces in China. Results showed that the critical LST threshold triggering HD to tea plants was 30.1 °C. Two different HD data sources (i.e., 68 counties in eight provinces from the Meteorological Disaster Management System (MDMS) and 37 counties in six cities from a published book) were used as HD validation samples. Validation accuracy analysis revealed that a critical LST threshold of 30.1 °C was reasonable, with an average accuracy of between 60% and 90% for the published-book dataset, and 75.7% in the northern Yangtze River area and 86.3% in the southern Yangtze River area for the MDMS dataset. This study confirmed that using remotely sensed LST products is an effective method for identifying temperature-related agrometeorological disasters owing to the method's ability to intuitively capture the surface temperature distribution of the disaster-affected object. The findings will be helpful for identifying the timing and location of HD to tea plants, and thereby potentially preventing HD to tea plants.

Time distribution pattern and spatial heterogeneity of hourly scale event-based extreme precipitation in China

Extreme precipitation occurs naturally in the form of “events,” and the spatio-temporal distribution pattern of event-based extreme precipitation is of great significance to flood disaster prevention and water resources protection. This study proposed the concept of hourly scale event-based extreme precipitation (HEEP), referring to a precipitation event with at least an hourly precipitation extreme (exceeding the 99th percentile threshold). Then we identified the dominant time distribution pattern (TDP), analyzed the seasonal proportion and distribution, and investigated the spatial distribution of three basic features (total frequency, amount, and duration) of HEEP from 2008 to 2017 in China and its nine major river basins. Results showed that over 90% of the areas in China were dominated by short-duration HEEP (S-HEEP, less than eight hours). While the rest areas were led by long-duration HEEP (L-HEEP, more than eight hours), mainly concentrated on the middle and lower reaches of the Yangtze River and southeast coastal areas of China. Areas dominated by S-HEEP were more than L-HEEP in different seasons except in winter. Three basic features of HEEP showed similar spatial distribution patterns of high in southeastern China and low in northwestern China, indicating HEEP frequently occurred in southeastern China with relatively large amounts and long duration. The concept of HEEP can provide new ideas for regional and global extreme precipitation research.

Complete Genomic Sequence of Xanthomonas oryzae pv. oryzae Strain, LA20, for Studying Resurgence of Rice Bacterial Blight in the Yangtze River Region, China.

Xanthomonas oryzae pv. oryzae (Xoo) is a causative agent of rice bacterial blight (BB). In 2020-2022, BB re-emerged, and there was a break out in the Yangtze River area, China. The pandemic Xoo strain, LA20, was isolated and identified from cultivar Quanyou1606 and demonstrated to be the Chinese R9 Xoo strain, which is able to override the widely adopted xa5-, Xa7- and xa13-mediated resistance in rice varieties in Yangtze River. Here, we report the complete genome of LA20 by PacBio and Illumina sequencing. The assembled genome consists of one circular chromosome of 4,960,087 bp, sharing 99.65% sequence identity with the traditional representative strain, YC11 (R5), in the Yangtze River. Comparative genome analysis of LA20 and YC11 revealed the obvious variability in Tal genes (the uppermost virulence determinants) in numbers and sequences. Particularly, six Tal genes were only found in LA20, but not in YC11, among which Tal1b (pthXo1)/Tal4 (pthXo6), along with the lost one, pthXo3 (avrXa7), might be the major factors for LA20 to overcome xa5-, Xa7- and xa13-mediated resistance, thus, leading to the resurgence of BB. This complete genome of the new pandemic Xoo strain will provide novel insights into pathogen evolution, the traits of pathogenicity on genomic level and the epidemic disease status in China.

An overview of the recent development of the Ground Source Heat Pump (GSHP) system in China

This paper summarizes the development of the Ground Source Heat Pump (GSHP) system in China during the period from 1989 to 2021. A statistical analysis shows the Ground-Coupled Heat Pump (GCHP) system is the major type of GSHP, accounting for 95.09% of the collected 2754 systems. The most likely building types of GSHP are residential and commercial buildings. The development of GSHP can be divided into three stages including the initial stage, the accelerating stage and the steady growing stage. The analysis of distribution density displays the GSHP is majorly located at the Yangtze River Area (YRA) and North China Plain (NCP) area. This matches very well with the potential density of GSHP estimated by considering air pollution, the thermal load of buildings, people density and GDP. Technical measures aiming at the reduction of the costs and the improvement of thermal efficiency of GSHP are the dominated internal factors, policy incentives and energy price are considered the major external factors determining the development of GSHP system.

Geology, geochronology, and geochemistry of the Gaojiabang tungsten-molybdenum deposit, Anhui Province, Southeast China

The Jiangnan Mo-W-Pb-Zn metallogenic belt hosts more than fifteen W-Mo and Mo deposits and is located at the margin between the Middle-Lower Yangtze metallogenic belt and the South China Continent. The recently discovered Gaojiabang W-Mo deposit, Chizhou district, Anhui Province, is the one of the largest W-Mo deposits in the belt (25.4 Mt at a grade of 0.28% WO3, 0.11 g/t Mo, with about 10,000 t of that total at an averarge grade of 6.6 g/t Au). The deposit is associated with Jurassic granite and monzonite porphyries that intruded sedimentary rocks of the Cambrian Huangboling Formation. Alteration displays a zonation from granite porphyry to wall rock. Five distinct alteration zones are recognized: deep-seated K-feldspar-biotite-quartz alteration, a quartz-sericite alteration zone, garnet-diopside-epidote alteration zone, calcite-quartz alteration zone, and zone of thermal metamorphism (hornfels). These features are comparable with porphyry Cu-Au-Mo systems. The first three zones of alteration display a close spatial relationship with W-Mo ores. Three distinct styles of W-Mo mineralization are recognized: minor vein-type W-Mo mineralization within sedimentary units; skarn W-Mo mineralization at the contact between sedimentary rocks and granite porphyry; and disseminated Mo(±W) mineralization hosted within both porphyries. The main ore minerals are scheelite, molybdenite, pyrite, pyrrhotite, and minor chalcopyrite, and display a zoned distribution in which most molybdenite occurs inside deep porphyries and the majority of the scheelite is observed inside shallow skarns and hornfels. Based on the presence of redox-indicative mineral assemblages such as pyrrhotite, molybdenite and pyrite in the absence of sulfates, we consider Gaojiabang to be a relatively reduced W-Mo porphyry-skarn system. Our new U-Pb zircon ages confirm Late Jurassic ages for granite (150.4±1.1 Ma) and monzonite porphyries (149.4±1.6 Ma). A molybdenite Re-Os age of 149.5±1.4 Ma indicates that W-Mo mineralization is closely associated with the two porphyries. This new data makes Gaojiabang the oldest deposit recognised so far in the Middle-Lower Yangtze River area, in turn inferring that the westward subduction of the Pacific Plate commenced at ∼150 Ma. Geochemical data indicate that mineralization in the Gaojiabang deposit derives from multiple sources, dominantly from magmatic rocks and basement strata via mantle-crust interaction, with the single greatest involvment of crustal materials among all deposits in the Middle-Lower Yangtze River area. Sulfides, including pyrite, pyrrhotite and molybdenite, display a wide range of δ34S between +3.8‰ to +12.1‰. The gradual increase of δ34S from inner porphyry to outer wall rock indicates contamination from crustal marine sedimentary facies as the ore-forming fluids evolved. Following the W-Mo mineralization event at Gaojiabang, emplacement of Qingyang-Jiuhua Complex at 144–127 Ma resulted in a previously unrecognized ductile deformation of porphyries, sedimentary rocks, and ores.

당의 해양력과 고구려 - 당의 2차 침공(647년) 이후를 중심으로

In 645, Emperor Taizong of Tang(唐太宗) lost the war with Goguryeo. Two years later, Taizong prepared for invasion again. It was concluded that intermittent attacks were continued with the water force, exhausting Goguryeo, and making all-out attacks. Between 647 and 648, the army invaded Goguryeo and fought many battles, showing off its dominant power. The random landing attack put Goguryeo in trouble. The efficiency of defense declined because the party’s leadership did not know where it would attack. Goguryeo’s expected defense area expanded and was forced to consume. BR On the contrary, the landing war trained Chinese water forces and accumulated local information about Goguryeo. Judging that Goguryeo was devastated, Taizong tried to invade with 300,000 people. Since July 648, ships with a length of 300m and a width of 150m have been built in Tsuan, and 1,450 ships have been built at the shipyard of the Yangtze River. The innate factor that made it possible was in China. China had a huge hinterland that was suitable for ports and easy to explore the ocean. In the Yangtze River area, there were many people engaged in water business, and they had a habit of pursuing wealth through waterways. There was a vast water industry base.BR However, with the death of Taizong in 649, the naval enhancement was suspended, but it was inherited to his son. Emperor Gojong of Tang(唐高宗) inherited naval forces trained by his father, maritime military bases built in various places, and skilled shipbuilders and shipyards.BR In 660, Gojong sent 1,800 fleets carrying 130,000 naval forces to destroy Baekje in 10 days. Furthermore, in 661, the fleet of the Tang Dynasty landed on the Daedong River and surrounded the Goguryeo capital. And in 663, the Tang Dynasty naval forces defeated the Japanese fleet on the Baekchon River in Baekje.BR However, the existence of Goguryeo naval forces against Tang Dynasty naval forces is invisible. Goguryeo did not reinforce the naval forces, but focused on enhancing the army. The sea is limited in that it can be used for defense, and ships with a lifespan of about 7 years are more consumable than forts. In order to maintain a certain number, continuous shipbuilding is required and enormous finances are required. Goguryeo cannot compete with the Tang Dynasty for fleet construction.BR The Tang Dynasty occupied the sea, and uncertainties in the sea increased. It hit Goguryeo’s logistics economy hard and increased social costs. The Tang Dynasty, which has a powerful naval force, has become much easier to invade Goguryeo. The loss of the sea would have been one of the environments of Goguryeo’s destruction.

The miR156-Targeted SQUAMOSA PROMOTER BINDING PROTEIN (PmSBP) Transcription Factor Regulates the Flowering Time by Binding to the Promoter of SUPPRESSOR OF OVEREXPRESSION OF CO1 (PmSOC1) in Prunus mume.

Prunus mume, a famous perennial ornamental plant and fruit tree in Asia, blooms in winter or early spring in the Yangtze River area. The flowering time directly determines its ornamental and economic value, so it is of great significance to study the molecular mechanism of flowering time. SQUAMOSA PROMOTER BINDING PROTEIN (SBP), often regulated by miR156, is an important flowering regulator, although its function is unknown in P. mume. Here, 11 miR156 precursors were analyzed and located in five chromosomes of the P. mume genome. The expression pattern showed that PmSBP1/6 was negatively correlated with miR156. The promoters of PmSBP1/6 were specifically expressed in the apical meristem. Overexpression of PmSBP1/6 in tobacco promoted flowering and changed the length ratio of pistil and stamen. Moreover, PmSBP1 also affected the number and vitality of pollen and reduced the fertility of transgenic tobacco. Furthermore, ectopic expression of PmSBP1/6 caused up-regulated expression of endogenous SUPPRESSOR OF OVEREXPRESSION OF CO1 (NtSOC1). The yeast-one hybrid assay showed that PmSBP1 was bonded to the promoters of PmSOC1s. In conclusion, a miR156-PmSBP1-PmSOC1s pathway was formed to participate in the regulation of flowering time in P. mume, which provided references for the molecular mechanism of flowering time regulation and molecular breeding of P. mume.

Phytoliths reveal cycling Pleistocene climate changes at a Paleolithic site in the lower reaches of the Yangtze River, East China

Phytoliths in the laterite profile of a Paleolithic site reveal Pleistocene climate variations in the lower reaches of the Yangtze River. Two group of phytoliths including chloridoid, panicoid, bulliform flabellate and saddle (long) phytoliths in the warm group, and festucoid, elongate entire and acute bulbosus phytoliths in the cool group are recognized. A warm index is calculated on the ratio of warm group to total warm and cool groups, and an aridity index on the ratio of chloridoid to total chloridoid and panicoid phytoliths. Climate indices of the phytoliths show at least 16 climatic stages indicating 8 warm-cool cycles, which are largely comparable with the variations between MIS-5 to MIS-23. It also reveals that the warm periods mostly correspond to the paleosols, while the cool ones to the clay and sandy layers. However, the relationship between the warm index and the aridity index is not clearly correlated, and chance for the occurrence of dry and less dry conditions is nearly the same under the warm or cool climate. Changes in aridity are more distinct and frequent at the lower part than at the upper part of the profile, and a changing tendency of less dry is recognized at the upper part of the profile. The overall warm indices of the profile are relatively higher in values. It suggests that frequent activities of early Pleistocene human beings took place under mild climate, especially during the dry and cool periods in the lower reaches of the Yangtze River area.

The Physician of the Shao Xing School in the Late Qing Dynasty -- Zhao Qingchu

Zhao Qingchu, a Confucian physician from the Kuaiji area at the end of the Qing Dynasty, learned from famous physicians of the Shao Xing School on exogenous febirle disease (Shang Han) and the You's of the Shi Cai School, drawing from the knowledge of the both medical schools. He quickly became popular for being a physician after giving up his research of Confucianism. He had a wide physician-patient network because of his art of healing as many politicians and celebrities such like Shao Youlian, Zeng Guoquan, Ren Daorong, Xu Yingkui and Ren Fuchang,were his patients. He was taken as a typical example of being good at the medical communication among doctors and doctors-patients in the Yangtze River area in the late Qing Dynasty. For instance, he once had a variety of medical communication with famous physicians, such as Wang Yuezhen, Ma Peizhi, He Lianchen, Zhang Wanxiang, Ling Jialiu and Zhou Bodu. He investigated medical theories in terms of exogenous febirle disease (Shang Han) and integrated his thinking with various medical schools, even attempting to involving western medicine. He was also skilled in teaching his medical thinking to his disciples, such as Zhao Shuan, Yang Zhian, Lu Dongchuan and He Jiren. Zhao Qingchu compiled his medical understanding based on his practice and experiences throughout his life and published this knowledge in Cun Cun Zhai Yi Hua Gao. He had it published many times, leading to a profound influence in Shaoxing and the Jiangnan area at that time.

New insights into the transfer and accumulation of dioxins and dioxin-like PCBs in the food web of farmed Chinese mitten crabs: A typical case from the Yangtze River area

Dioxins and dioxin-like polychlorinated biphenyls (DL-PCBs) transfer and accumulation behavior remains poorly understood in the farmed Chinese mitten crab (Eriocheir sinensis). In this study, dioxins and DL-PCBs concentration in 48 farming crabs in lower reaches of the Yangtze River was monitored and controlled field design was conducted in a typical farm to dissect the dioxins and DL-PCBs contamination in crab food web (crab, feeds, and environment). Results showed that dioxins and DL-PCBs were ubiquitous in farmed crabs with concentrations ranging from 0.390 to 37.2 pg toxic equivalents (TEQ) g−1 ww and do not present a health risk to general consumers. Of the total dioxins TEQ found in crab in treated farms, 45.6% was attributed to direct transfer from the aquaculture environment and 46.5% to the consumption of snails. Consumption of feed material accounted for nearly all of the total DL-PCBs TEQ, divided as 58.2% from feed and 41.8% from snails. These results demonstrated that dominant routes of dioxins accumulation in crabs were transferred for the sediment-snail-crab and sediment-crab chains, whereas DL-PCBs is mainly transferred through consumption of feeds and snails. To our knowledge, this work is the first report of snails serving as a biomagnification medium that promotes accumulation of dioxins in mitten crabs. This observation provided crucial insight to prevent and reduce contamination of crab by dioxins and DL-PCBs.

Spatial difference of climate change effects on wheat protein concentration in China

Climate change effects on global food security are not only limited to its effects on the yield of cereals but also their nutritional quality. However, climate change effects on crop nutritional quality, particularly grain protein concentration (PC) on a large geographical scale have not yet been quantified in China. For this purpose, we assessed the effects of three key climatic factors (temperature, precipitation, and solar radiation) on wheat PC in ten wheat-growing areas of China using a series of statistical models on a county-level PC dataset. The results demonstrated that the average PC in China from 2006 to 2018 ranged from 12.01% to 14.50% across the ten areas, with an obvious spatial difference pattern showing an increase in PC from south to north and from west to east. The sensitivity analysis indicated that PC showed a positive response to variation in the increasing temperature, and the PC of wheat grown in the Huanghuai area was less affected than the PC of wheat grown in other areas. Conversely, solar radiation posed negative effects on the PC in the southwestern area, whereas precipitation had intricate effects on the PC in all areas. Besides, the highest explanation of climate variability during five growth periods contributed 26.0%–47.6% of the PC variability in the northeastern area, whereas the lowest explanation of climate variability during five growth periods only accounted for 2.5%–3.7% of PC variability in the Yangtze River area. Our study further demonstrated that the effects of climate change on wheat grain PC in China were spatially heterogeneous with higher effects on PC in spring wheat-growing areas as compared to winter wheat-growing areas. We suggested that the northern and the northeastern area in China could be developed as alternative areas to produce wheat with high grain PC in the face of climate warming.

Spatiotemporal Characterization of the Urban Expansion Patterns in the Yangtze River Delta Region

Characterizing urban expansion patterns is of great significance to planning and decision-making for urban agglomeration development. This study examined the urban expansion in the entire Yangtze River Delta Region (YRDR) with its land-use data of six years (1995, 2000, 2005, 2010, 2015, and 2018). On the basis of traditional methods, we comprehensively considered the four aspects of urban agglomeration: expansion speed, expansion difference, expansion direction, and landscape pattern, as well as the interconnection of and difference in the expansion process between each city. The spatiotemporal heterogeneity of urban expansion development in this region was investigated by using the speed and differentiation indices of urban expansion, gravity center migration, landscape indices, and spatial autocorrelations. The results show that: (1) over the 23 years, the expansion of built-up land in the Yangtze River Delta Region was significant, (2) the rapidly expanding cities were mainly located along the Yangtze River and coastal areas, while the slowly expanding cities were mainly located in the inland areas, (3) the expansion direction of each city varied and the gravity center of the urban agglomeration moved toward the southwest, and (4) the spatial structure of the region became more clustered, the shape of built-up land turned simpler, and fragmentation decreased. This study unravels the spatiotemporal change of urban expansion patterns in this large urban agglomeration, and more importantly, can serve as a guide for formulating urban agglomeration development plans.

Temporal-Spatial Structure and Influencing Factors of Urban Energy Efficiency in China’s Agglomeration Areas

Energy efficiency has proved to be effective in mitigating greenhouse gas emissions and is significant to carbon neutrality targets. Urban agglomeration is the major engine of urbanization supporting economic growth. To optimizing the spatial exchange structure to improve regional energy efficiency by integrating the total factor energy efficiency model and social network analysis, this study constructs the spatial network of energy efficiency among cities within five major urban agglomerations in China for the period 2011–2018 and investigates their spatial association characteristics. The influencing factors of each spatial network structure are also explored by the quadratic assignment procedure method. The findings show that the spatial association of energy efficiency within each urban agglomeration presents a typical network structure, but with considerable disparity among urban agglomerations. Most cities in the Yangtze River Delta and Pearl River Delta are closely connected with each other, while the surrounding cities in the areas of Beijing-Tianjin-Hebei, Chengyu and the Middle Reaches of the Yangtze River highly depend on their corresponding central cities. The spatial adjacency and GDP per capita determine the urban spatial relationship of the energy efficiency within urban agglomerations. In addition, the spatial correlation of urban energy efficiency in the Beijing-Tianjin-Hebei, Chengyu and Middle Reaches of the Yangtze River areas is also affected by the differences in energy consumption, capital stock, number of labor force and pollutant emission. Some suggestions for improving urban energy efficiency are discussed.

Nitrogen reduction in high plant density cotton is feasible due to quicker biomass accumulation

Cotton (Gossypium hirustum L.) as well as other crops are asking for an effective production with cost reduction and environment stewardship globally, especially in the developing countries. A new cotton planting strategy should be possible by shortening the growth season (less than six months rather than seven to eight months by late sowing and early harvesting) with low nitrogen (N) and high density. Therefore, a two-year (2018–2019) field experiment was conducted with a split plot design, two planting densities (D1, 6 plants m−2; D2, 8 plants m−2) as the main plot and three N rates (150, 180 and 210 kg ha-1 referred as N1, N2, and N3, respectively) as the subplot, to determine the effects of planting density and N rate on cotton yield and biomass accumulation. Results showed that, averaged across years, cotton yield was greater for treatment D2 as compared with that in D1, and N3 did not differ from that in N2 but was greater than that in N1. The highest lint yield (1271.2 kg ha-1) was achieved in D2N2 which no differ from that in D2N3 and D1N3. The maximal biomass (K) was achieved in treatment D2N2 (1032.4 g m−2) with the average speed (VT) of 21.2 g m−2 d-1 during the fast accumulation period, and the maximal growth rate (Rm, 20.5 g m−2 d-1) of sink during the cotton growth and development. Seedcotton yield was positively correlated (r = 0.72) to the plant biomass during flowering and boll-setting period, and the yield was contributed directly by sink with a coefficient as high as 0.70, while it was contributed indirectly by flow and source with coefficients of 0.63 and 0.59, respectively. The results suggest that N reduction is feasible due to a quicker bulk sink biomass accumulation under a higher planting density, which benefits efficient cotton production in the Yangtze River Valley, China, and areas with similar ecology.

Spatio-temporal evaluation of the urban agglomeration expansion in the middle reaches of the Yangtze River and its impact on ecological lands

In developing countries, urban agglomerations have become one of the most important carriers of urbanization. In China, one of the largest national urban agglomerations is the UAMRYR (urban agglomeration in the middle reaches of the Yangtze River), which has the fastest urban development in Central China and is home to critical ecological spaces. On this basis, this study analyzed the urban expansion and loss of ecological lands in UAMRYR by establishing a spatial database, grid system, rose maps, and scenario simulation. The highlights of results are as follows: the urban expansion of UAMRYR includes four stages of development: steady growth, accelerated development, peak, and deceleration. Polarized development has occurred in the region, with the Wuhan, Changsha-Zhuzhou-Xiangtan, and Nanchang metropolitan areas having high levels of urban expansion while the other cities have varying levels of urban growth. The loss of ecological land was found to have a highly similar curve and spatial distribution with the urban growth. In terms of ecological land types, the loss of agricultural land accounted for more than half of ecological lands lost overall. Losses in forests, grasslands, wetlands, and water areas varied for different areas, depending on particular conditions and specific environmental characteristics of the city. The three metropolitan areas experienced the highest increases in urban built-up areas; they also had the highest loss of ecological land, which can have critical consequences given their proximity to the Yangtze River, Poyang Lake, Dongting Lake, and other important environmental sensitive areas. The simulation results show that the UAMRYR is projected to maintain a rapid expansion rate from 2020 to 2030. If the urban expansion, particularly in the metropolitan areas, is not managed well and controlled, serious ecological damage could be inflicted on the Yangtze River Basin.

Monitoring drought dynamics in China using Optimized Meteorological Drought Index (OMDI) based on remote sensing data sets

Timely and accurate monitoring of the spatiotemporal changes in drought is very important for the reduction in the social losses caused by drought. The Optimized Meteorological Drought Index (OMDI), originally established in southwestern China, showed great potential for drought monitoring over large regions on a large scale. However, the applicability of the index requires further evaluation, especially when used throughout China, which has a different agricultural divisions, variable climatic conditions, complex terrain and diverse land cover. In addition, the OMDI model relies on training data to construct local parameters for the model. On a large scale, it is of great significance to use multisource remote sensing data sets to construct OMDI model parameters. In this paper, the constrained optimization method was used to establish weights for the MODIS-derived Vegetation Conditional Index (VCI), TRMM-derived Precipitation Condition Index (PCI), and GLDAS-derived Soil Moisture Condition Index (SMCI) and calculate the OMDI based on the Standard Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI) and weather stations. The accuracy of the OMDI model was evaluated by using the correlation coefficient. Moreover, the spatiotemporal changes in drought were also analyzed through trend analysis, Mann-Kendall (MK) statistics and the Hurst index on the monthly and annual scales. The results showed that (1) the highest positive correlation between the OMDI and the SPI was SPI-1, which was higher than that for any other month interval, such as 3 months, 6 months, 9 months and 12 months of the SPI. The results indicated that the OMDI was suitable to monitor meteorological drought. (2) In the nine agricultural subareas in China, the degree of drought in the Yangtze River (DYR) area had the most severe evolution and change frequency. This region was very sensitive to drought in the past two decades. (3) The area with OMDI variation coefficient less than 0.1 accounted for 94%, indicating that the degree of drought fluctuates little; The linear tendency rate is 0.0004, and the area greater than 0 reaches 66.44%, indicating that the drought is developing in a lightning trend. (4) The Hurst index value is mostly higher than 0.5 (the area ratio is 56.31%), and the area of "Positive-Consistent" and "Negative- Opposite" accounted for 54.02%, indicating that more than half of China's area drought changes will show a trend of mitigation in the future.