Search

Flash drought is characterized by rapid onset and short-duration drought conditions caused by a combination of factors, including high evaporation, high temperature, and prolonged periods of little to no precipitation, leading to a sudden and severe decrease in soil moisture levels. In comparison to conventional drought, it is more susceptible to the effects of global warming and has the potential to become a common drought phenomenon in the coming years, necessitating further research. In this paper, we focused on flash drought events, specifically in forest parts of northeastern China that are included within the Greater Khingan Mountains (GKM), Lesser Khingan Mountains (LKM), and Changbai Mountains (CM), using daily soil moisture data as well as SPOT- VEGETATION NDVI satellite data from 2000 to 2020 and determined their impact on the forest NDVI. Our major findings are as follows. (1) The forest within GKM had the maximum area being affected by flash drought events. (2) The frequency ranged from 1 to 2 times, whereas the total duration varied between 20 and 55 days over the study area in a 21-year period. (3) Flash drought was most common in the plant-growing seasons. (4) The flash drought events had a negative influence on the forest NDVI. Our study contributes to a deeper understanding of the flash drought dynamics in forest areas of northeast China for flash drought monitoring, prediction, and management strategies in this region. [ABSTRACT FROM AUTHOR]

Ecosystems are undergoing continuous degradation due to the dual perturbation of global climate change and human activities, posing unprecedented threats and challenges to the ecosystem services they provide. To gain a deeper understanding of the spatio-temporal evolution of ecosystem service value (ESV), it is essential to accurately capture the characteristics of its spatial and temporal changes and its influencing factors. However, traditional spatio-temporal statistical methods are limited to analyzing the heterogeneity of ESV in a single temporal or spatial dimension, which fails to meet the comprehensive analysis needs for spatio-temporal heterogeneity over an extended continuum. Therefore, this paper constructs a Bayesian spatio-temporal hierarchical model to analyze the ESV heterogeneity in both temporal and spatial dimensions in Northeast China from 2000 to 2020 to accurately identify the regions with unstable fluctuations in ESV and analyze the influencing factors behind them. It aims to comprehensively and systematically reveal the intrinsic laws of spatio-temporal evolution of ESV, and provide a scientific basis for relevant decision-making. The study found a continuous fluctuating downward trend of ESV in Northeast China from 2000 to 2020, with significant spatial and temporal heterogeneity. Notably, the distribution of hot and cold spots is regularly concentrated, especially in the transition zone from low hills to plains, which forms an "unstable zone" of spatial and temporal fluctuations of ESV. Natural factors such as NDVI and NPP exhibit a significant positive correlation with ESV, while social factors like population density and GDP show a strong negative correlation. Compared to traditional statistical methods, the Bayesian spatio-temporal hierarchical model, with its outstanding flexibility and accuracy, provides a new perspective and way of thinking for analyzing classical spatio-temporal problems. Firstly, the model examines time and space as a whole and fully accounts for the influence of spatio-temporal interactions on ESV. Secondly, the Bayesian spatio-temporal hierarchical model meets the needs of long-term continuous ESV outcome detection, which provides us with solid support for a deeper understanding of the evolution of ESV. [ABSTRACT FROM AUTHOR]

Background: China is one of the most biodiverse countries in the world and has given birth to unique ecosystems, abundant species and rich genetic variety. More and more attention has been paid to biodiversity research in China. The Wanda Mountains, located in the east of Heilongjiang Province in northeast Chia, is a northern extension of the Changbai Mountains, one of the main mountains ranges in the region. In this study, we present the first checklist of spermatophyte and invasive alien plant species in the Wanda Mountains, which was compiled using published materials, specimen records and field surveys conducted from 2018 to 2020. This checklist, which has been published in the Global Biodiversity Information Facility (GBIF), provides a comprehensive overview of the plant species richness of the Wanda Mountains. New information: This data paper presents the first checklist of spermatophytes and invasive alien plants in the Wanda Mountains, comprising a total of 704 species and infraspecific taxa. Amongst these, there are 656 native plants belonging to 328 genera and 94 families and 48 invasive alien plants belonging to 39 genera and 20 families. The checklist includes 251 new records of native plants and 39 new records of invasive plants. This is the first widely shared data on an independent floristic unit in northeast China and can serve as a valuable resource for future biodiversity research in this region and, moreover, trigger more biodiversity data papers in this data-valued country. [ABSTRACT FROM AUTHOR]

This study investigates the 40-year spatiotemporal evolution of cropland in Northeast China's black soil region at the county scale. Utilizing land use/cover maps from 1980 to 2020 with a 30 m x 30 m resolution, we employed various analytical methods, including mathematical statistics, GIS spatial analysis, land use transition matrix, landscape pattern analysis, and hotspot analysis. The findings of this study are as follows: (1) Cropland area expanded by 51,976.76 km² from 1980 to 2020, mainly concentrated in the Sanjiang Plain, Songnen Plain, and Liaohe Plain. Notably, areas near prefecture-level city locations experienced a decrease in cropland, while regions farther from cities witnessed an increase. (2) Cropland primarily transitioned from woodland, grassland, and unused land to cropland, covering substantial areas. Conversely, cropland was converted mainly into woodland, built-up land, and grassland. (3) Over the same period, cropland in the region exhibited increased elevation and slope, with average altitude rising by 2.06 m and average slope increasing by 0.0369 degrees. (4) The study revealed an increase in cropland proportion, predominance, and aggregation, alongside more irregular shapes and reduced subdivision. These findings highlight significant changes in the cropland landscape in Northeast China's black soil region and offer insights for policy recommendations and land management strategies. The research findings of this paper can offer valuable insights for the protection and utilization of cropland in the region. They can provide scientific references for the formulation of policies related to China's food security. [ABSTRACT FROM AUTHOR]

At present, scholars hold two opposite views on the spatial impact (i.e., positive and negative impact) of high-speed rail (HSR) on tourism economy. To better explore the spatial impact of HSR on tourism economy, this paper uses the difference-in-differences (DID) to empirically test the causal effect of HSR and tourism economy, specifically by using the panel data of cities in Northeast China from 2010 to 2018 as research sample. On the whole, empirical results show that HSR has become an important factor in promoting the development of tourism economy. The impact of HSR on tourism economy in different years indicates that with the continuous promotion of HSR, the effect of HSR-driven tourism economy has become increasingly evident. On this basis, this paper classifies cities according to different types and finds that compared with ordinary prefecture-level cities, central cities are more affected by HSR. Compared with cities with high abundance of tourism resources, cities with low abundance of tourism resources are more affected by HSR. Therefore, current article is convinced that while seizing the opportunity of HSR, cities should actively avoid the negative impact brought by the development of HSR and truly promote the balanced development of regional tourism. • We provide a broader understanding of the issue of HSR and tourism economy through detailed data and quantitative evidence. • Taking Northeast China as an example, the positive effect of HSR on tourism economy in underdeveloped regions is verified. • The impact of HSR on the tourism economy in Northeast China is heterogeneous. • The findings provide support for synergistic HSR planning and tourism development. [ABSTRACT FROM AUTHOR]

The size of snow grains is an important parameter in cryosphere studies. It is the main parameter affecting snow albedo and can have a feedback effect on regional climate change, the water cycle and ecological security. Larger snow grains increase the likelihood of light absorption and are important for passive microwave remote sensing, snow physics and hydrological modelling. Snow models would benefit from more observations of surface grain size. This paper uses an asymptotic radiative transfer model (ART model) based on MOD09GA ground reflectance data. A simulation of snow grain size (SGS) in northeast China from 2001 to 2019 was carried out using a two-channel algorithm. We verified the accuracy of the inversion results by using ground-based observations to obtain stratified snow grain sizes at 48 collection sites in northeastern China. Furthermore, we analysed the spatial and temporal trends of snow grain size in Northeastern China. The results show that the ART model has good accuracy in inverting snow grain size, with an RMSD of 65 μm, which showed a non-significant increasing trend from 2001 to 2019 in northeast China. The annual average SGS distribution ranged from 430.83 to 452.38 μm in northeast China, 2001–2019. The mean value was 441.78 μm, with an annual increase of 0.26 μm/a, showing a non-significant increasing trend and a coefficient of variation of 0.014. The simulations show that there is also intermonth variation in SGS, with December having the largest snow grain size with a mean value of 453.92 μm, followed by January and February with 450.77 μm and 417.78 μm, respectively. The overall spatial distribution of SGS in the northeastern region shows the characteristics of being high in the north and low in the south, with values ranging from 380.248 μm to 497.141 μm. Overall, we clarified the size and distribution of snow grains over a long time series in the northeast. The results are key to an accurate evaluation of their effect on snow–ice albedo and their radiative forcing effect. [ABSTRACT FROM AUTHOR]

Population shrinkage has had a certain negative impact on urban and rural development in many aspects. The impact of population shrinkage on urban–rural integration has become one of the core scientific issues that needs to be addressed in the current research on promoting the goal of common prosperity in China. Northeast China is a typical region in China that is experiencing a decrease in population and economic activity. Investigating the integrated development of urban and rural areas in this region is highly important for revitalizing Northeast China. This research paper focuses on 32 prefecture-level cities in Northeast China and utilizes spatial correlation analysis and the Geographical Weighted Regression model to uncover the evolving spatial patterns and influential factors affecting integrated urban–rural development in the context of population decline. The findings revealed the following: (1) The level of integrated urban–rural development in Northeast China continues to rise despite the shrinking population. During the comprehensive population decline stage, the growth rate of the urban–rural coupling coordination degree surpasses that of the initial stage. The areas with high values of urban–rural coupling coordination degree shift from northeastern Heilongjiang to four sub-provincial cities. The spatial correlation between urban–rural coupling and coordinated development weakens, with the main type being low–low agglomeration. (2) Factors such as economic development level, labor force size, urbanization level, level of openness, urban–rural accessibility, and proportion of built-up areas significantly correlate with urban–rural coupling and coordination. The influence of each factor varies in magnitude and direction across different locations. Labor force size and urban–rural accessibility have the most-significant impact on integrated urban–rural development, with labor force size having a positive effect and urban–rural accessibility having a negative effect. The impact of the economic development level follows a pattern of initial increase and subsequent decrease as the population shrinks. (3) Although population decline does not hinder integrated urban–rural development in Northeast China, it is closely connected to changes in the factors influencing such development. To capitalize on the development opportunities presented by national policies, Northeast China should adopt a model of urban–rural development that promotes rural growth through cities. This entails attracting talented individuals to return, enhancing the flow of urban–rural development elements in both directions, and creating a spatial development pattern characterized by "big city, big agriculture, and big ecosystem". By doing so, the revitalization of Northeast China can be achieved. [ABSTRACT FROM AUTHOR]

Northeast China plays a pivotal role in producing commodity grains. The precipitation and temperature distribution during the growth season is impacted by geographical and climate factors, rendering the region vulnerable to drought. However, relying on a single index does not reflect the severity and extent of drought in different regions. This research utilised the random forest (RF) model for screening remote sensing indices. Relative soil moisture (RSM) was employed to compare seven commonly used indices: the temperature vegetation dryness index (TVDI), vegetation supply water index (VSWI), vegetation condition index (VCI), temperature condition index (TCI), vegetation health index (VHI), multi-band drought index (MBDI), and normalised difference drought index (NDDI). The effectiveness of these indices for monitoring drought during different developmental stages of spring maize was evaluated. Trend rates were employed to investigate the temporal changes in drought patterns of spring maize from 2003 to 2020, and the Sen + Mann–Kendall test was used to analyse spatial variations. The results showed the following: (1) The seven remote sensing indices could accurately track drought during critical growth stages with the TVDI demonstrating higher applicability than the other six indices. (2) The application periods of two TVDIs with different parameters differed for the drought monitoring of spring maize in different developmental periods. The consistency and accuracy of the normalised difference vegetation index (NDVI)-based TVDI (TVDIN) were 5.77% and 34.62% higher than those of the enhanced vegetation index (EVI)-based TVDI (TVDIE), respectively, in the early stage. In contrast, the TVDIE exhibited 13.46% higher consistency than the TVDIN in the middle stage, and the accuracy was the same. During the later stage, the TVDIE showed significantly higher consistency and accuracy than the TVDIN with consistency increases of 9.61% and 38.64%, respectively. (3) The drought trend in northeast China increased from 2003 to 2020, exhibiting severe spring drought and a weakening of the drought in summer. The southern, southwestern, and northwestern parts of northeast China showed an upward drought trend; the drought-affected areas accounted for 37.91% of the study area. This paper identified the most suitable remote sensing indices for monitoring drought in different developmental stages of spring maize. The results provide a comprehensive understanding of the spatial–temporal patterns of drought during the past 18 years. These findings can be used to develop a dynamic agricultural drought monitoring model to ensure food security. [ABSTRACT FROM AUTHOR]

China's largest high-latitude permafrost distribution zone is in Northeast China. With the intensification of global warming and engineering construction, the carbon stored in permafrost will gradually thaw and be released in the form of methane gas. However, research on the changes in methane concentration and emission sources in this area is still unclear. In this paper, the AIRS (Atmospheric Infrared Sounder) data carried by the Aqua satellite were used to analyze the distribution and change trends in the overall methane concentration in the near-surface troposphere in Northeast China from 2003 to 2022. These data, combined with national meteorological and on-site monitoring data, were used to study the methane emission characteristics and sources in the permafrost area in Northeast China. The results show that the methane concentration in the near-surface troposphere of Northeast China is mainly concentrated in the permafrost area of the Da and Xiao Xing'an Mountains. From 2003 to 2022, the methane concentration in the near-surface troposphere of the permafrost area in Northeast China showed a rapid growth trend, with an average linear trend growth rate of 4.787 ppbv/a. In addition, the methane concentration in the near-surface troposphere of the permafrost area shows a significant bimodal seasonal variation pattern. The first peak appears in summer (June–August), with its maximum value appearing in August, and the second peak appears in winter (December–February), with its maximum value appearing in December. Combined with ground surface methane concentration monitoring, it was found that the maximum annual ground surface methane concentration in degraded permafrost areas occurred in spring, causing the maximum average growth rate in methane concentration, also in spring, in the near-surface troposphere of permafrost areas in Northeast China (with an average value of 6.05 ppbv/a). The growth rate of methane concentration in the southern permafrost degradation zone is higher than that in the northern permafrost stable zone. In addition, with the degradation of permafrost, the geological methane stored deep underground (methane hydrate, coal seam, etc., mainly derived from the accumulation of ancient microbial origin) in the frozen layer will become an important source of near-surface troposphere methane in the permafrost degradation area. Due to the influence of high-permeability channels after permafrost degradation, the release rate of methane gas in spring is faster than predicted, and the growth rate of methane concentration in the near-surface troposphere of permafrost areas can be increased by more than twice. These conclusions can provide a data supplement for the study of the carbon cycle in permafrost areas in Northeast China. [ABSTRACT FROM AUTHOR]

Soil moisture plays an important role in crop yield estimation, irrigation management, etc. Remote sensing technology has potential for large-scale and high spatial soil moisture mapping. However, offline remote sensing data processing is time-consuming and resource-intensive, and significantly hampers the efficiency and timeliness of soil moisture mapping. Due to the high-speed computing capabilities of remote sensing cloud platforms, a High Spatial Resolution Soil Moisture Estimation Framework (HSRSMEF) based on the Google Earth Engine (GEE) platform was developed in this study. The functions of the HSRSMEF include research area and input datasets customization, radar speckle noise filtering, optical-radar image spatio-temporal matching, soil moisture retrieving, soil moisture visualization and exporting. This paper tested the performance of HSRSMEF by combining Sentinel-1, Sentinel-2 images and in-situ soil moisture data in the central farmland area of Jilin Province, China. Reconstructed Normalized Difference Vegetation Index (NDVI) based on the Savitzky-Golay algorithm conforms to the crop growth cycle, and its correlation with the original NDVI is about 0.99 (P < 0.001). The soil moisture accuracy of the random forest model (R2 = 0.942, RMSE = 0.013 m3/m3) is better than that of the water cloud model (R2 = 0.334, RMSE = 0.091 m3/m3). HSRSMEF transfers time -consuming offline operations to cloud computing platforms, achieving rapid and simplified high spatial resolution soil moisture mapping. [ABSTRACT FROM AUTHOR]

In order to achieve a rapid and accurate identification of soil stratification information and accelerate the development of smart agriculture, this paper conducted soil stratification experiments on agricultural soils in the Mollisols area of Northeast China using Ground Penetrating Radar (GPR) and obtained different types of soil with frequencies of 500 MHz, 250 MHz, and 100 MHz antennas. The soil profile data were obtained for 500 MHz, 250 MHz, and 100 MHz antennas, and the dielectric properties of each type of soil were analyzed. In the image processing procedure, wavelet analysis was first used to decompose the pre-processed radar signal and reconstruct the high-frequency information to obtain the reconstructed signal containing the stratification information. Secondly, the reconstructed signal is taken as an envelope to enhance the stratification information. The Hilbert transform is applied to the envelope signal to find the time-domain variation of the instantaneous frequency and determine the time-domain location of the stratification. Finally, the dielectric constant of each soil horizon is used to obtain the propagation velocity of the electromagnetic wave at the corresponding position to obtain the stratification position of each soil horizon. The research results show that the 500 MHz radar antenna can accurately delineate Ap/Ah, horizon and the absolute accuracy of the stratification is within 5 cm. The effect on the soil stratification below the tillage horizon is not apparent, and the absolute accuracy of the 250 MHz and 100 MHz radar antennas on the stratification is within 9 cm. The overwhelming majority of the overall calculation errors are kept to within 15%. Based on the three central frequency antennas, the soil horizon detection rate reaches 93.3%, which can achieve accurate stratification of soil profiles within 1 m. The experimental and image processing methods used are practical and feasible; however, the GPR will show a missed detection for soil horizons with only slight differences in dielectric properties. Overall, this study can quickly and accurately determine the information of each soil stratification, ultimately providing technical support for acquiring soil configuration information and developing smart agriculture. [ABSTRACT FROM AUTHOR]

Tomographic imaging technology is a geophysical inversion method. According to the ray scanning, this method carries on the inversion calculation to the obtained information, and reconstructs the image of the parameter distribution rule of elastic wave and electromagnetic wave in the measured range, so as to delineate the structure of the geological body. In this paper, teleseismic tomography is applied by using seismic travel time data to constrain layered crustal structure where Fast Marching Methods (FMM) and the subspace method are considered as forward and inverse methods, respectively. Based on the travel time data picked up from seismic waveform data in the study region, the P-wave velocity structure beneath Northeast China down to 750 km is obtained. It can be seen that there are low-velocity anomalies penetrating the mantle transition zone under the Changbai volcano group, Jingpohu Volcano, and Arshan Volcano, and these low-velocity anomalies extend to the shallow part. In this paper, it is suggested that the Cenozoic volcanoes in Northeast China were heated by the heat source provided by the dehydration of the subducted Pacific plate and the upwelling of geothermal matter in the lower mantle. The low-velocity anomaly in the north Songliao basin does not penetrate the mantle transition zone, which may be related to mantle convection and basin delamination. According to the low-velocity anomalies widely distributed in the upper mantle and the low-velocity bodies passing through the mantle transition zone beneath the volcanoes, this study suggests that the Cenozoic volcanoes in Northeast China are kindred and have a common formation mechanism. [ABSTRACT FROM AUTHOR]

Northeast China played an irreplaceable role in population migrations and cultural exchanges in East Asia during the Paleolithic. This paper collected 182 archaeological sites to analyse the characteristics of spatial-temporal variations of Paleolithic human activities in Northeast China, and explored the driving mechanisms behind these variations in combination with the paleoenvironmental and archaeological studies. During the Lower Paleolithic, constrained by the relatively cold-dry climate and blocked by the Songnen paleo-lake basin, the population was sparse and distributed only near 40° N at the southern end of Northeast China. Upon entering the Middle Paleolithic, as humans developed greater tolerance to cold climates and adopted more sophisticated survival strategies with the application of small lithic tools, their numbers increased and geographical distribution expanded northward to 45° N at the central region of Northeast China. The Upper Paleolithic saw a considerable increase in population and expansion across almost all of Northeast China except for the eastern Inner Mongolia Plateau. We speculated that 50 ka and 30 ka BP were two key points, both of which may be associated with a significant increase in the frequency of migrations and communications among humans, and the widespread popularity of highly mobile microblade technology, respectively. In addition, the environmental analysis of archaeological sites revealed a continuous spread of Paleolithic humans to areas with higher elevations, steeper slopes, and lower temperatures. Meanwhile, they were becoming less reliant on water resources and were more widely conducting activities in open-air areas, showing that the environmental adaptability had been continuously improving over time. This study can provide a reference for the reconstruction of the migration history of early humans in East Asia, and is also of great significance for a comprehensive understanding of the evolutionary process of early human-environment interactions. [ABSTRACT FROM AUTHOR]

Selenium is an important element for human health. Many studies have identified selenium deficiency in soil and water as an important factor in causing Keshan Disease (KD) in Northeast China. Previous studies have mainly focused on soil selenium content, staple food selenium content, and human selenium level, but there are few systematic studies on soil selenium's existing forms and their migration from soil to crops and the human body. This paper focused on inferring the barrier factors in the migration of selenium from soil to crop and the human body and transformation of its compounds. It provides a reference basis for the etiological analysis, prevention, control, and elimination of KD. The study used 121 183 samples of topsoil (0−20 cm), 30 295 soil parent samples of selenium and other geochemical indices in northeast China, and crop seeds and human hair samples from the KD endemic area. The surface soil selenium was dominantly selenium-sufficient in Northeast China. However, the soil selenium levels were generally low. The average topsoil selenium in Northeast China was 0.20 mg/kg, significantly lower than the world's average soil selenium content (0.4 mg/kg) and slightly lower than the Chinese average soil selenium content (0.24 mg/kg). Soil selenium mainly existed in strongly bounding by organic bound, with humic acid, and residue forms. The amount of selenium available to plants was sufficient in the selenium-sufficient and KD-endemic areas. However, the average selenium content of human hair was deficient, on average, with 0.16 mg/kg in KD endemic area. We assume that lower soil selenium content may be the basic factor influencing the biogeochemical deficiency of selenium in Northeast China. The sequestration of selenium by clay chemical constituents, such as iron and aluminum oxides and soil organic matter, especially in acidic soils, is another direct contributing factor to the low selenium content in biogeochemical food chain, which increases the risk of KD in the population. [ABSTRACT FROM AUTHOR]

The Nenjiang River Basin, located in the northern part of Northeast China, is an important cultural region that has attracted much attention from academic communities. Previous studies demonstrated that hunting and gathering always dominate the subsistence for prehistoric populations in this region. Herein, we further investigate the evolution of dietary and economic strategies in the Late Neolithic and Bronze Age occupations at the recently excavated Honghe site of the Nenjiang River Basin by means of a multidisciplinary approach incorporating zooarchaeological and stable isotope analysis. The results of zooarchaeological approaches indicate that the Honghe populations rely extensively on hunting and fishing during the Late Neolithic (4500–4000 cal BP), consistent with the results of previous studies. Interestingly, by the Bronze Age (3100–2400 cal BP), animal husbandry develops as one main economic strategy, corresponding to the probable decline of hunting and fishing, which is different from the previous reports. In addition, based on the results of stable isotopic approaches, C3 plants are always prominent diets for animals and humans from the Late Neolithic to the Bronze Age, which signifies that crop agriculture does not appear to have been of primary importance during either of these eras, in contrast to the C4 agricultural tradition formed in the Neolithic Age of the southern part of Northeast China. The findings of this paper shed some more light on the evolution of human subsistence strategies in the Nenjiang River Basin. [ABSTRACT FROM AUTHOR]

The Erdaopuzi section in the Baishan area of Jilin Province, northeast China, contains abundant late Tremadoc graptolites. However, there are some taxonomic controversies regarding the characters of the hand specimens that are difficult to identify. In this paper, we present our restudy of isolated graptolites from acid residue and discuss the taxonomic problems of the subgenus Clonograptus (Neoclonograptus) Zhao and Zhang. Four genera and six species were identified, including Adelograptus tenellus (Linnarsson), Ancoragraptus gracilis (Zhao and Zhang), Dictyonema sp., Psigraptus jacksoni Rickards and Stait, Psigraptus lenzi Jackson, Psigraptus arcticus Jackson. According to the significant evolution of morphological characters, two graptolite zones (from bottom to top) can be identified in ascending order in the study area, i.e. Adelograptus Zone and the Psigraptus Zone. [ABSTRACT FROM AUTHOR]

Northeast China is a prominent base for commercial grain production nationwide. Soil erosion, a primary cause of land degradation and grain yield decrease, has become an imminent issue and is still not well documented in Northeast China. Thus, a comprehensive assessment of soil erosion in Northeast China is essential for deepening our understanding of various geological and agricultural issues, such as control of regional water and soil losses, anti-degeneration attempts on black soil, preservation of land fertility, and safeguarding of national food security. Based on the Revised Universal Soil Loss Equation (RUSLE) and the Revised Wind Erosion Equation (RWEQ) models, this paper comprehensively assessed the water and wind erosion in Northeast China from 2000 to 2020 and analyzed the current situation, as well as the spatial and temporal evolution of soil erosion. The results suggest the following: (1) The degree of soil erosion in Northeast China was mainly slight, and water erosion was more severe than wind erosion. Water and wind erosion in bare land and grassland were more intensive than in cropland and forests. The Liao River Plain (LRP) has undergone relatively intensive water erosion, while the wind erosion in the Greater Kinggan Mountains Region (GKMR) was more intensive than in other sub-regions. (2) A slight intensifying trend of water erosion could be observed in Northeast China from 2000 to 2020, where the area of slight water erosion decreased and that of light and intensive water erosion increased. The water erosion in the Changbai Mountain Region (CBMR), the Sanjiang Plain (SJP), and the Songnen Plain (SNP) intensified, while the LRP has undergone slower water erosion than before. The water erosion in bare land and cropland intensified, while the water erosion in grassland and forests slowed down. Compared to the first decade (2000–2010), the second decade (2010–2020) in the timespan of study had a reversed trend of water erosion from intensifying to moderating, which means water erosion was alleviated. (3) A moderating trend in wind erosion could be found in Northeast China from 2000 to 2020, where the area of slight wind erosion increased and that of light, moderate, and intensive wind erosion decreased. The wind erosion in the LRP showed a pronounced decrease, and the wind erosion in bare land and cropland also considerably decreased. Compared to the first decade, the amount of wind erosion in the second decade decreased by 18.2%, but the rate in the second decade decreased slowly or even increased. These two facts indicate that wind erosion in Northeast China has alleviated, but this trend is gradually slowing down. Soil erosion is caused by multiple factors, such as climate, topography, soil, and human activities. This study provides important implications for our understanding of soil erosion control and management in Northeast China. In sub-regions with severe erosion, such as the LRP and the GKMR, we can adopt methods such as zero tillage, cross ridge tillage, and straw mulching according to the local characteristics of soil erosion to slow down the process. [ABSTRACT FROM AUTHOR]

Facing the new era of construction of socialism with Chinese characteristics, it is critical for the northeastern region of China to hold this new chance for its overall revitalization. The foundation and key of this revitalization lie in finding out problems in the urban development and then putting forward feasible countermeasures. This paper studies 34 prefecture-level cities in northeast China, and uses the coordination index to analyze the relationship between land and population, economy, and investment, of different types of cities in the region from 2000 - 2014, in order to discover problems in its urban development and provide planning countermeasures. Data shows that in northeast China, the imbalance between urban land expansion and population is significant, the imbalance between urban land use and either economic development or capital investment is periodical, for which the primary reasons include strong centralization effect of center cities, limited input on land resources, and weak industrial competitiveness. Correspondingly, the paper proposes planning strategies in terms of vitalizing stock land, enriching land use functions, and coordinating industrial resources, with an expectation of providing both the theoretical foundation for the economic revival in the northeastern region and a guidance on practice of revitalization strategies in all cities of the region. [ABSTRACT FROM AUTHOR]

Since establishing diplomatic relations in October 1949, North Korea and China have forged a complex alliance characterized by both firm solidarity and mutual distrust. This paper analyzes the ups and downs of their alliance relationship by examining the "Northeast Rear Doctrine" (NRD) suggested by Mao Zedong in the early 1960s, which proposed that North Korea could utilize China's Northeast region as its rear base in the event of a war on the Korean Peninsula. Mao's proposal represents the apex of the Sino-North Korean alliance, implying China's temporary concession of its sovereignty over the northeastern territory to North Korea. However, when China and South Korea established diplomatic relations in 1992, the NRD policy was virtually abolished, thereby significantly affecting Sino-North Korean relations. First, it exacerbated security threats to North Korea's regime as Northeast China, which once served as Pyongyang's rear base, was transformed into Seoul's outpost for infiltration into North Korea. Second, it deepened North Korea's distrust of China and served as a catalyst for transforming Sino-North Korean relations into normal state-to-state dynamics, rather than the traditional party-to-party relationship. [ABSTRACT FROM AUTHOR]

Heavy-duty diesel trucks (HDDTs) have caused serious environmental pollution in China. Accurate estimation of their pollutant emission characteristics is essential to reduce emissions and associated environmental and public health impacts. To achieve sustainable development for transport emissions in Northeast China, we developed localized emission factors and a high-resolution emission inventory of HDDTs, based on on-board test, Guidebook and international vehicle emission (IVE) model. The results show that the total emissions of CO, NO, NO2, and PM from HDDTs in Northeast China in 2020 were 172.2 kt, 531.5 kt, 11.2 kt, and 921.4 t, respectively. In terms of spatial distribution, emissions decreased from the city center to the city fringe. Temporally, the NOx emission variation curves of different types of roads presented a "single-peak" emission characteristic, which was different from the peak of traffic flow. Three emission reduction scenarios are further developed in the paper. Scenario analysis shows that elimination of HDDTs that follow the old China III emission standard and installing tailpipe treatment devices are the most effective pollutant reduction measure. The reduction percentages for CO, NO, NO2, and PM ranged from 62.9 to 83.89%. The results of our study could inform policymakers to devise feasible strategies to reduce vehicle pollution in Northeast China. [ABSTRACT FROM AUTHOR]

Background: An investigation report of stonefly fauna in Benxi Manchu Autonomous County, Liaoning Province, northeast China (used to be called Manchuria, now includes Liaoning, Jilin, Heilongjiang Provinces and parts of Inner Mongolia, which are adjacent to the Russian Far East and the Korean Peninsula). Materials were studied with field observation in 2018 and 2019. New information: This paper records five families, nine genera and 14 species of stoneflies from Taizi River, Liaoning Province. Nine species have been recorded for the first time in China and the biology of several common species is also reported for the first time. [ABSTRACT FROM AUTHOR]

In the early summer (June) of 2022, the spatial mean precipitation in northeast China (NEC) was 62% higher than normal and broke the historical record since 1951. Based on the precipitation data of 245 meteorological stations in NEC and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis, this paper analyzes the role of large-scale circulation and sea-surface temperature (SST) associated with anomalous precipitation over NEC in June using singular value decomposition (SVD), correlation analysis, regression analysis, and composite analysis methods, and further investigates the possible cause of the abnormal precipitation in June 2022. Results show that the northeast China cold vortex (NCCV) accompanying the blocking high in the Okhotsk Sea (BHOS) has been the primary mid-to-high latitude atmospheric circulation pattern affecting NEC precipitation in June since 2001. This circulation pattern is closely related to the tripole SST pattern over the North Atlantic (NAT) in March. In June 2022, the NAT SST anomaly in March stimulates eastward-propagating wave energy, resulting in the downstream anomalous circulation pattern in which the NCCV cooperates with the BHOS in the mid-high latitudes of East Asia. Under this background atmospheric circulation favorable for precipitation, the Kuroshio region SST anomaly in June led to a more northward and stronger anomalous anticyclone in the northwestern Pacific through local air–sea interaction, which provides more sufficient water vapor for NEC, resulting in unprecedented precipitation in June 2022. [ABSTRACT FROM AUTHOR]

The increasing scarcity of cultivated land resources necessitates the continuous change in cultivated land functions. Cultivated land has gradually changed from being used for a single function to multiple functions. The use of cultivated land for multiple functions has become an important way to achieve the sustainable use, management, and protection of cultivated land. In this, the development of different functions of cultivated land must be coordinated. Thus, clarifying the evolution trend of the use of cultivated land for various functions, calculating the coupling and coordination degrees of these multiple functions, and identifying the driving factors in these uses play important roles in realizing the orderly development of cultivated land multifunctionality. This paper defined multifunctioning cultivated land as containing a production function, a social function, and an ecological function. Based on the socioeconomic panel data and geospatial data of Heilongjiang, Jilin, and Liaoning, which are the major grain-producing areas of northeast China, in the years 2005, 2010, 2015, and 2020 we calculated the multiple function coupling coordination degree of cultivated land using the Coupling Coordination Degree Model and identified the driving forces in the evolution of the spatial-temporal pattern of cultivated land multifunctionality using Geodetector. The results show that from 2005 to 2020, there were significant regional differences in terms of the production, social, and ecological functions of cultivated land in the research areas. The multifunctional coupling coordination degree of cultivated land in the study areas was gradually improved. The spatial-temporal evolution of the multifunctional coupling coordination degree of cultivated land was found to mainly be influenced by the level of agricultural development, such as the level of per capita disposable income and the rate of effective irrigation of cultivated land. The government should attempt to guarantee the comparative benefits of agricultural production to increase the income level of farmers; increase investment in agricultural infrastructure construction to improve the level of agriculture development; and implement a strict farmland protection policy to achieve the continuous improvement of the productivity of cultivated land, realize the ordered development of coupling, and improve the coordination of the use of cultivated land for multiple functions. The results of this study are applicable not only to northeast China but also to other major grain-producing areas that are under pressure to protect their cultivated land and achieve the suitable use of cultivated land. [ABSTRACT FROM AUTHOR]

• Ecosystem services are quantified at large scales and long time series in NE China. • The trade-offs and synergies among ecosystem services are characterized. • Human activities are the dominant driving factors of provisioning services. • Synergistic optimization paths of production-ecological functions are proposed. In Northeast (NE) China, the largest commodity grain base and natural forest area in China, both agricultural production and ecological protection require attention. In recent years, land degradation in NE China has increased, seriously affecting the production-ecology synergy. In this paper, four key ecosystem services (ESs) in NE China are quantified: provisioning, water conservation (WC), soil conservation (SC) and sand fixation (SF), and the spatiotemporal evolution characteristics and trade-offs and synergies (T&S) of ESs are analyzed. The driving factors of provisioning services and the characteristics of T&S are considered, and the county zoning scheme and the corresponding production-ecological function synergistic optimization paths are proposed. The results show that (1) the provisioning, WC and SF services in NE China have slightly increased in the past 20 years, and the provisioning in the Greater-Khingan-Mountains-Region (GKMR) and Lesser-Khingan-Mountains-Region (LKMR), the WC in the LKMR, and the SF in the Liao-River-Plain (LRP) have more obviously increased. The SC service has slightly decreased, especially in the Changbai-Mountains-Region (CBMR). (2) The provisioning service in NE China mainly shows a synergistic relationship with WC and SF, accounting for 79.1 % and 62.9 % of the area, respectively, and a trade-off relationship with SC, accounting for 52.54 % of the area. (3) Human activities (HA) are the dominant driving factor of the provisioning service change in NE China, with an impact degree of 62.65 %. The LKMR is an exception, as climate change (CC) dominates. The LRP, Songnen-Plain (SNP) and GKMR have high degrees of HA. (4) The number of synergistic optimized (SO), light optimized (LO) and trade-off limited (TL) counties accounted for 19.0 %, 61.7 % and 19.3 %, respectively. Among them, the SO type counties should prioritize improving provision and grain production capacity, the LO type counties should protect basic farmland and decrease trade-offs between ESs, and the TL type counties should improve ecological functions and strengthen ecological protection and restoration. This paper clarifies the main contradictions of ESs in NE China and provides an important scientific basis for ecological protection and restoration, which is important for ensuring food and ecological security and realizing the ecological and efficient sustainable utilization of black soil. [ABSTRACT FROM AUTHOR]

In recent years, the frequent occurrence of extreme climate disasters has seriously affected agriculture in Northeast China. Based on precipitation data derived from 83 geographical stations in the study area for 60 years (1960–2019), we chose the reliable statistical methods of the Mann–Kendall test, Sen's slope, and the Standardized Precipitation Index, and regarded drought and flood as a whole in this paper, to identify the temporal and spatial variation characteristics of precipitation and extreme climate events in Northeast China. The results show that an increasing trend of disasters was detected at the 95% confidence level (Z = 2.3). According to the timescale analysis, abrupt climate changes started in 2006. Temporal and spatial distribution of extreme climate disasters, mainly drought and flood disasters, showed a significant upward trend from 2006 to 2019. According to the spatial analysis, the precipitation in Northeast China decreased from south to north and fluctuated less from east to west. Moreover, stations with extreme climate trends (trend of climatic anomaly with confidence level > 90%) followed the same spatial pattern as those with a high frequency of extreme climate disasters (more than 17.87 times/decade). The severity and frequency of extreme climate have increasingly threatened Northeast China in the past decade. In particular, the Northeast Plain experienced the most severe and extreme climate events that seriously threatened the study area in 2007, 2009, 2010, and 2019. Our results highlight the urgent need for the development of monitoring and early warning of droughts and flood disasters to reduce economic losses. [ABSTRACT FROM AUTHOR]

In this paper, we selected the northeast region as a study area from the perspective of soil nutrient demand, calculated the livestock carrying capacity of farmland under three scenarios where nitrogen nutrient accounts for 35% (low level), 45% (medium level), and 55% (high level) of fertilization, and carried out a risk analysis. The results show that the scale of husbandry breeding is expanding and the scale of the planting industry has remained basically unchanged. Under the three scenarios, there were 23 regions where the livestock manure exceeded the maximum value that could be absorbed by farmland in 2008 and 28 regions in 2019. These regions in the potential area are mostly located in Heilongjiang province and the regions in the restricted area are mostly located in Liaoning Province. On the whole, the northeast region is generally faced with the problem of livestock overloading, and the insufficient utilization and treatment capacity of livestock manure poses a huge threat to regional ecological security. Based on this, adjusting the structure of regional planting and breeding, promoting the development of the livestock manure processing industry, enhancing the production capacity of organic fertilizer, and constructing an integrated pattern of regional planting and breeding are effective ways to realize the sustainable utilization of farmland in northeast China. [ABSTRACT FROM AUTHOR]

The tectonic setting of Jurassic magmatism in the Northeast China (NE China) is unclear. Here, we present new petrological, whole-rock geochemical, zircon U-Pb geochronological, and zircon Lu-Hf isotope data for Jurassic granitoids of the Wulong region, Liaodong Peninsula, NE China. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) zircon U-Pb data indicate that these granitoids were emplaced at 165–156 Ma. The biotite monzogranite, two-mica monzogranite, monzogranite, granodiorite, biotite granodiorite, and syenogranite are strongly peraluminous (A/CNK=1.09–1.29), contain peraluminous minerals such as muscovite, have high normative corundum abundances (1.26 wt.%–3.28 wt.%), and have high K2O/Na2O ratios (0.76–1.48), all of which indicate an S-type granite affinity. However, the biotite granodiorite and syenogranite have high Sr (391 ppm–570 ppm) and low Y (3.06 ppm–5.94 ppm) contents, with high Sr/Y (65.8–185.9) ratios, and the two-mica monzogranite, monzogranite, and granodiorite have relatively high Sr (138 ppm–379 ppm) and low Y (3.38 ppm–8.71 ppm) contents, with high Sr/Y ratios (19.1–77.9). All of the analyzed samples have negative zircon εHf(t) values (−41.4 to −20.6) with old two-stage Hf model ages (TDM2(Hf)=2.50–3.76 Ga). Therefore, we infer that the biotite monzogranite is the typical feature of S-type granite that was derived by partial melting of metagraywacke. The monzogranite, two-mica monzogranite, granodiorite, biotite granodiorite, and syenogranite exhibit geochemical characteristics of S-type granite with K-rich adakitic features, and were possibly derived by mixing of melts from clastic crustal materials and adakitic magmas. There are voluminous Jurassic igneous rocks in the NE China. By combining our study with the previous researches, this paper infers that the Jurassic magmatism within the Erguna-Xing'an Massif was related to the southward subduction and closure of the Mongol-Okhotsk Ocean; the Early Jurassic magmatism to the east of the Songliao Basin and in the northern North China Craton (NCC) was related to the subduction of the Pacific Plate; however, the Middle-Late Jurassic igneous rocks to the west of the Songliao Basin were related to the closure of the Mongol-Okhotsk Ocean and, in the northern NCC, were related to closure of the Mongol-Okhotsk Ocean with an influence from flat-slab subduction of the Pacific Plate. [ABSTRACT FROM AUTHOR]

Urban shrinkage has become a worldwide phenomenon, and poses challenges to urban planning and regional development strategies. Although numerous researchers have identified the characteristics and causes of urban shrinkage, the understanding of urban shrinkage from a regional perspective has not yet been explored. To fill this gap, in this paper, we analyzed the nature of urban shrinkage in northeast China, the typical Chinese region affected by urban shrinkage, from a regional perspective. The results show urban shrinkage occurs in 64 county-level cities. A total of 34.62% of shrinking cities were classified as smartly growing cities, characterized by economic growth and population loss, while 65.38% of shrinking cities were identified as absolutely shrinking cities, suffering simultaneously from economic and demographic decline. The connection between central cities and shrinking cities allowed identification of three types of phenomena, namely central agglomeration leading to peripheral shrinkage, shrinkage of prefecture-level city proper, and central diffusion leading to peripheral shrinkage. The causes of urban shrinkage include agglomeration effects of central cities, aging of demographic structure, supply–demand mismatch between industries and market, weak connection between industries and services, and underdeveloped public services. Furthermore, the agglomeration effects of central cities play a critical role in urban shrinkage in northeast China. Therefore, from a regional perspective, shrinkage was an inevitable experience in the process of socioeconomic development in northeast China. The "best" development path for northeast China may be to comply with the tendency toward urban shrinkage, and restructuring of the spatial distribution of socioeconomic activities. [ABSTRACT FROM AUTHOR]

Large volumes of Early Cretaceous adakitic rocks crop out in northeast China. In this paper, we summarize their spatial-temporal distribution and geochemical characteristics. These adakitic rocks exhibit variable MgO, Cr and Ni contents, as well as potassium enrichments, in contrasting with those of the slab melting derived adakites. Positive εNd(t) and εHf(t) values and low 87Sr/86Sr(i) indicate significant Phanerozoic crust growth in NE China. Based on their geochemistry, these adakitic rocks are mainly derived from partial melting of juvenile lower crust. We interpret the melting to have resulted from extension and associated delamination. The ages of adakitic rocks are 141–120 Ma in the Xing'an region, 129–113 Ma in the Songliao basin, and 113–90 Ma in the Jiamusi region. Based on the lower-crustal-melting geochemical characteristics and spatial distribution of ages, we propose a new two-stage convergent bidirectional subduction model: Mongol-Okhotsk oceanic plate subduction and associated slab rollback in the west from 141–114 Ma and the Paleo-Pacific oceanic plate subduction and associated slab rollback in the east from 113–90 Ma. [ABSTRACT FROM AUTHOR]

This paper addresses the interannual variation of winter air temperature over Northeast China and its connection to preceding Eurasian snow cover. The results show that there is a significant negative correlation between October Eurasian snow cover and following-winter air temperature over Northeast China. The snow cover located in eastern Siberia and to the northeast of Lake Baikal plays an important role in the winter air temperature anomaly. More (less) eastern Siberia snow in October can cause an atmospheric circulation anomaly pattern in which the atmospheric pressure is higher (lower) than normal in the polar region and lower (higher) in the northern mid-high latitudes. Due to the persistence of the eastern Siberia snow from October to the following winter, the winter atmospheric anomaly is favorable (unfavorable) to the widespread movement of cold air masses from the polar region toward the northern mid-high latitudes and, hence, lower (higher) temperature over Northeast China. Simultaneously, when the October snow cover is more (less), the SST in the northwestern Pacific is continuously lower (higher) as a whole; then, the Aleutian low and the East Asia trough are reinforced (weakened), favoring the lower (higher) temperature over Northeast China. [ABSTRACT FROM AUTHOR]

Quality of life (QOL) is a hotspot issue that has attracted increasing attention from the Chinese Government and scholars, it is also a vital issue that should be addressed during the cause of ′establishing overall well-off society′. Northeast China is one of the most import old industrial bases in China, however, the industrial structure of heavy chemical industry and the development mode of ′production first, living last′ have leaded to series of social problems, which have also become a serious bottleneck to social stability and economic sustainable development. Through applying the methods of BP neural network, exploratory spatial data analysis (ESDA) and spatial regression model, this paper examines the space-time dynamics of QOL of the residents in Northeast China. We first investigate the indexes of QOL of the residents and then use ESDA methods to visualize its space-time relationship. We have found a spatial agglomeration of QOL of the residents in middle-southern Liaoning Province, central Jilin Province and Harbin-Qiqihar-Daqing area of Heilongjiang Province. Two third of the counties are low-low spatial correlation, and the correlative type of about 60% of the prefecture level areas keeps stable, indicating QOL of the residents in Northeast China shows a certain character of path dependence or spatial locked. We have also found that economic strength and development levels of service industry have positive and obvious effect on QOL of the residents, while the effect of such indexes as the social service level and the proportion of the tertiary industries are less. [ABSTRACT FROM AUTHOR]

Research has increasingly demonstrated that complex relationships exist between residential indoor air quality, health and socioeconomic factors. However, few studies have provided a comprehensive understanding of these relationships. The purpose of this paper, therefore, was to use structural equation modeling to identify the combined effect of residential indoor air quality and socioeconomic factors on occupants' health, based on field measurement data in Northeast China. The results showed that socioeconomic status had a direct impact on the occupants' health with the path coefficient of 0.413, whereas the effect from indoor air quality was 0.105. Socioeconomic status posed the direct effect on indoor air quality with path coefficients of 0.381. The weights of PM2.5, CO2, TVOC (Total Volatile Organic Compounds), and formaldehyde concentration to the indoor air quality were 0.813, 0.385, 0.218, and 0.142, respectively. Relative contributions of Income level, education level, and occupation prestige to socioeconomic status were 0.595, 0.551, and 0.508, respectively. Relationships between indoor air quality, socioeconomic factors and health were further confirmed based on multiple group analysis. The study defines and quantifies complex relationships between residential indoor air quality, socioeconomic status and health, which will help improve knowledge of the impacts of the residential indoor environment on health. [ABSTRACT FROM AUTHOR]

Under the background of complex international situation, how to build the special geo-economic space of China-Russia border lies in strengthening their foreign trade resilience against external shocks. Based on empirical evidence from ten prefecture-level China-Russia border regions in Northeast China, this paper analyzed the spatiotemporal evolution of foreign trade resilience under different shocks. Furthermore, through the Panel Regression model, the mechanism of the industrial structure on the foreign trade resilience in contraction period and expansion period was discussed. The results showed that: 1) from 2004 to 2021, foreign trade in China-Russia border regions experienced five phases. The overall foreign trade resilience was higher than expected, showing a rising volatility trend, but there was significant spatial heterogeneity in the ability of cities to cope with shocks. 2) Highly specialized clusters were mainly concentrated in Yichun, Heihe and Da Hinggan Ling Prefecture, while Mudanjiang and Yanbian performed better in related and unrelated diversification. 3) In different stages of economic system evolution, the response mode, degree and result of border foreign trade resilience to regional industrial structure showed obvious stage characteristics. During the contraction period, related diversification was more conducive to improving the resistance through risk spillovers. During the expansion period, specialization played a more significant role in improving regional resilience through self-reinforcing effect. These results are beneficial for expanding the resilience theory, ensuring border economic security and optimizing border industrial investment layout. [ABSTRACT FROM AUTHOR]

Assessing Sustainable Development Goal (SDG) indicator 15.3.1, which refers to the proportion of degraded land to total land area, and analysing its status and drivers is essential for the development of policies to promote the early achievement of SDG target 15.3 of Land Degradation Neutrality (LDN). In this study, Northeast China was selected as the study area, and the progress of indicator 15.3.1 was assessed based on the perspective of Net Primary Productivity (NPP) calculated by the CASA model. WorldPop population spatial distribution data were used as a proxy for human activities, combined with climate data to calculate the effects of changes in temperature, precipitation and population spatial distribution on vegetation NPP based on the partial correlation coefficient method and the Geodetector method. The results showed that 92.81% of the areas that passed the test of significance showed an increasing trend in vegetation NPP from 2000 to 2020. The vegetation NPP was affected by a combination of temperature, precipitation and population. The effects of temperature and precipitation on spatial differences in NPP for various vegetation types were significantly greater than those of population, but in high-density population zones, the effects of population on spatial differences in NPP were generally greater than those of temperature and precipitation. Precipitation was the main driver for spatial variation in NPP in deciduous broad-leaved forests, cultivated vegetation and thickets, while temperature was the main driver for spatial variation in NPP in evergreen coniferous forests. Generally, the warming and wetting trend in Northeast China contributed to the accumulation of NPP in cultivated vegetation, thickets, steppes and grasslands. The sensitivity of NPP to temperature and precipitation in deciduous broad-leaved and deciduous coniferous forests varied according to geographical location. [ABSTRACT FROM AUTHOR]

The permafrost in Northeast China is experiencing rapid degradation due to the influence of climate change and human activities, profoundly impacting the local ecological environment and engineering construction. Understanding the spatiotemporal dynamics of long-term permafrost in this region is crucial; however, systematic research on this topic remains scarce. This study combines meteorological station data, MODIS land surface temperature (LST) datasets, and borehole locations to apply the surface frost number (SFn) model. This approach enables the simulation and estimation of the spatial distribution and changes in the area of the surface frost number without vegetation effects (SFnv) and permafrost temperature (PT) in Northeast China from 1971 to 2020. The area of the SFnv > 0.49 within the permafrost region decreased substantially from approximately 44.353 × 104 km2 to 19.909 × 104 km2 between 1971 and 2020, with a notable change in 1988. The area of permafrost calculated using PT < 0 was slightly smaller, declining from 39.388 × 104 km2 to 29.852 × 104 km2. There was also a significant increase in the area with PT ranging from −1 °C to 0 °C, indicating a decline in permafrost stability. Approximately 10.926 × 104 km2 of stable permafrost has been transformed into semi-stable and unstable permafrost. Moreover, from 1982 to 2020, the NDVI was negatively correlated with the area of stable permafrost and positively correlated with the area of transitional or unstable permafrost. Vegetation cover decreased as transitional or unstable permafrost degraded. These findings provide valuable information for permafrost research and engineering development in cold regions, as well as for future planning and adaptation strategies. [ABSTRACT FROM AUTHOR]

This fundamental investigation aimed to deliver a new theoretical perspective to address the brain drain problem from Northeast China. The amenity theory could provide a robust ideological foundation that enables cities to attract talent and drive urban innovation and development. This study explores the spatial–temporal pattern evolution of talent inflow to Northeast China based on data from the China Migrant Dynamic Survey (CMDS) from 2012 to 2018. It utilizes spatial analysis methods and geographic detectors to interpret the factors that influence the spatial heterogeneity of talent inflow from the perspective of urban amenities. The following results were obtained. First, the trend in the number of talent inflows displays an initial increase followed by fluctuations before inflow destinations are concentrated in four major cities and certain resource-based cities in Northeast China. Second, a high-quality labor force is engaged in varied industries. Talents with different academic qualifications could avail themselves of diverse employment choices, primarily in information transmission, software, and information technology services. Those with undergraduate and postgraduate degrees could find positions in the education industry. Third, the talent flow mode has gradually changed from interprovincial to intercity movements within a particular province. However, the mode of talent flow differs according to discrete academic qualifications. Most postgraduates choose the interprovincial flow, and undergraduates and junior college students predominantly select the intercity flow within a particular province. Fourth, the inflow of talent to destinations in Northeast China is based on artificial amenities and tends toward cities that offer efficient public services, abundant leisure facilities, and innovative soft and hard environments. The major factors that affect the spatial differentiation in talent inflow to a city include the number of hospital beds per 10,000 people, scientific research, creative practitioners, talent-related policies, exhibition halls and other leisure and entertainment venues, and average housing prices in the city. Most interactions between artificial environment amenity factors and other elements are better than their individual effects, especially the interactive configuration of affordable urban housing prices, high-quality public resources, such as education and health care, and abundant leisure and entertainment facilities. [ABSTRACT FROM AUTHOR]

Despite the significant impacts of biomass burning (BB) on global climate change and regional air pollution, there is a relative lack of research on the temporal trends and geographic patterns of BB in Northeast China (NEC). This study investigates the spatial–temporal distribution of BB and its impact on the atmospheric environment in the NEC region during 2004 to 2023 based on remote sensing satellite data and reanalyzed data, using the Siegel's Repeated Median Estimator and Mann–Kendall test for trend analysis, HDBSCAN to identify significant BB change regions, and Moran's Index to examine the spatial autocorrelation of BB. The obtained results indicate a fluctuating yet overall increasing BB trend, characterized by annual increases of 759 for fire point counts (FPC) and 12,000 MW for fire radiated power (FRP). BB predominantly occurs in the Songnen Plain (SNP), Sanjiang Plain (SJP), Liaohe Plain (LHP), and the transitional area between SNP and the adjacent Greater Khingan Mountains (GKM) and Lesser Khingan Mountains (LKM). Cropland and urban areas exhibit the highest growth in BB trends, each surpassing 60% (p < 0.05), with the most significant growth cluster spanning 68,634.9 km2. Seasonal analysis shows that BB peaks in spring and autumn, with spring experiencing the highest severity. The most critical periods for BB are March–April and October–November, during which FPC and FRP contribute to over 80% of the annual total. This trend correlates with spring planting and autumn harvesting, where cropland FPC constitutes 71% of all land-cover types involved in BB. Comparative analysis of the aerosol extinction coefficient (AEC) between areas with increasing and decreasing BB indicates higher AEC in BB increasing regions, especially in spring, with the vertical transport of BB reaching up to 1.5 km. County-level spatial autocorrelation analysis indicates high–high clustering in the SNP and SJP, with a notable resurgence of autocorrelation in the SNP, suggesting the need for coordinated provincial prevention and control efforts. Finally, our analysis of the impact of BB on atmospheric pollutants shows that there is a correlation between FRP and pollutants, with correlations for PM2.5, PM10, and CO of 0.4, 0.4, and 0.5, respectively. In addition, the impacts of BB vary by region and season, with the most significant impacts occurring in the spring, especially in the SNP, which requires more attention. In summary, considering the escalating BB trend in NEC and its significant effect on air quality, this study highlights the urgent necessity for improved monitoring and strategic interventions. [ABSTRACT FROM AUTHOR]

The Cretaceous continental strata developed in eastern Northeast China are rich in animal and plant fossils and have formed important minerals such as coal and oil shale. The only records of the earliest marine strata in Early Cretaceous are also preserved here besides Tibet' which is of great significance for the study on Cretaceous geography in China. Many new discoveries have been made in the Cretaceous stratigraphy of this area in recent years' some of which have filled the gaps of strata study in Northeast China. The paper also preliminarily discusses the co-evolution of Late Cretaceous flora and fauna represented by dinosaurs in the region. [ABSTRACT FROM AUTHOR]

Northeast (NE) China is characterized by large areas of Mesozoic and Paleozoic granitoids, whereas Cenozoic granitoids are scarce. This paper reports LA-ICP-MS zircon U-Pb ages and whole-rock geochemical data for late Paleocene-early Eocene granitoids from the Jiamusi Massif, NE China, in order to determine their petrogenesis and tectonic implications. Geochronological data indicate that the granodiorite and dioritic porphyry from the Wudingshan pluton formed at 51.5 ± 0.3 Ma and 56.3 ± 0.8 Ma, respectively. The biotite-quartz diorite, biotite granodiorite, and dioritic porphyry have high SiO2 (68.38-70.06 wt.%), Al2O3 (15.34-15.79 wt.%), and Na2O (3.96-4.49 wt.%) contents, low MgO contents (1.10-1.26 wt.%), A/CNK ratios of 0.99-1.11, and are classified as medium- to high-K calc-alkaline and weakly peraluminous I-type granitoids. They are enriched in LREEs and LILEs, and depleted in HFSEs, with Nb/Ta ratios of 10.4-15.0. Moreover, they have negative Nb-Ta-Ti anomalies, indicating that they were derived from continental crust. Combining with the previously published isotopic data and regional geological results, we suggest that the late Paleocene-early Eocene granitoids (56-52 Ma) were probably derived from partial melting of juvenile lower crust, and formed in an active continental margin setting, possibly related to subduction slab rollback of the Paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Predict the evolution of land use and landscape ecological risk. • Couple landscape ecological risk and ecological security network. • Construct an ecological security network for multiple future development scenarios. • Explore sustainable development scenario for Northeast China. • Make recommendations for ecological security network optimization. The expansion of human activities has significantly increased ecological risks, which threaten the security of ecosystems. This paper takes Northeast China, a national typical ecological barrier region, as a case study to explore the evolution of the ecological environment under various future development scenarios. Considering the complexity of ecological assessments, a comprehensive approach integrating various methods is employed. This includes the Patch-based Land Use Simulation (PLUS) model, Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model, a landscape ecological risk assessment index system, the Space Minimum Cumulative Resistance (MCR) model, among others. These methods are used to dynamically assess changes in land use, landscape ecological risk (LER), and the layout of ecological networks. An integrated framework is proposed for identifying, constructing, and optimizing the ecological security network (ESN). The results show that the LER in Northeast China presents a "high in the middle, low around" distribution characteristic. High risk areas are mainly distributed in water bodies and construction lands with high landscape fragmentation and isolation, while low risk areas are primarily in the Northeast forest belt and Inner Mongolia grassland areas with lower landscape vulnerability and separation. From 2000 to 2020, the LER in the Northeast China has increased, primarily manifested in the Greater and Lesser Khingan Range areas in the northern part of the study region. Forecast results indicate significant differences in the evolution of LERs and the layout of the ESN under different socio-economic development scenarios. Under the ecological protection (EP) scenario, the average LER in Northeast China is 0.2215. The area of ecological source lands is 302,405.56 km2, the length of ecological corridors is 179,024.71 km, with 339 ecological nodes and 410 ecological breakpoints identified. Compared with the natural development (ND) and urban construction (UC) scenarios, the EP scenario in Northeast China shows the lowest LER and the most ideal layout of the ESN. This study provides a reference for future land resource optimization and ecological restoration in Northeast China. [ABSTRACT FROM AUTHOR]

Northeast China (NEC) is the most prominent grain‐producing region in China. However, it is currently facing significant impacts from climate change. Since the climate‐related impacts on crop yield in this region are a major concern for society in the future, quantifying climate change impacts on crop yields in NEC is essential to ensure future food security. This study aimed to quantify the effects of future climate change on crop yields in NEC and explore adaptation strategies using the Crop Growth Model (PCSE) driven by downscaled CMIP6 climate projections under four Shared Socioeconomic Pathways (SSPs) scenarios during 2015–2100. Results showed that there could be average reductions in crop yields of 21.4% for maize and 4.2% for soybean by the year 2100 under SSP585 compared to the 2015 baseline. The increasing temperature was the dominant factor in reducing yields, although elevated CO2 and precipitation offered partial compensation. The optimized planting date brought noticeable benefits for rice and soybean but had limited effects on maize due to heat stress. Relocating rice expansion eastward and implementing earlier planting increased yields by up to 50% but adversely decreased soybean and maize due to competition. This study enriches our comprehension of climate change impacts on NEC agriculture, while also quantifying potential benefits and constraints of evaluated adaptations. The proposed adaptations may help mitigate projected yield declines in other key agricultural regions across the globe. Adjusting crop management practices to capitalize on changing climate factors shows promise as a strategy for sustaining production globally. Plain Language Summary: Northeast China (NEC) is essential for achieving food accessibility and food security in China, but its agricultural production is seriously threatened by climate change. This study investigated how climate change could impact maize, rice, and soybean crop yields in this region from 2015 to 2100, using the PCSE crop model and forcing from the international Coupled Model Intercomparison Project 6 (CMIP6) climate projections. Simulation results suggested rising temperatures would negatively affect crop yields, especially for maize. Increased carbon dioxide and rainfall partially offset these losses. By 2100, average declines were projected for maize (−21%) and soybeans (−4%), respectively. Altering planting dates to match crop needs was an effective adaptation to boost yields, with rice benefiting the most. Relocating rice production eastward and expanding its area substantially increased simulated rice yields (+62%) but decreased other crops due to competition (−32% maize, −28% soybeans). Even with adaptations, some areas still showed yield declines, indicating extra measures may be needed to maintain production. Overall, this study suggests significant risks to crop yields from climate change in Northeast China, with adaptations like optimized planting and strategic crop relocation able to mitigate some but not all of the projected impacts. Key Points: Rising temperatures negatively impacted simulated future crop yields, especially for maizeAdjusting planting dates boosted yields for rice and soybeans but had limited benefits for maizeRelocating and expanding the rice area increased yields substantially [ABSTRACT FROM AUTHOR]

Freeze–thaw cycles (FTCs) occur during the nongrowing season, and residual nitrogen (N) increases the risk of N loss with melting water. To study the effect of FTCs on soil N, rice fields in improved irrigated saline soil in northeast China were selected as the research subjects. Water content (10%, 20%, and 30%), different N fertilizer levels (180 and 220 kg/ha), and multiple FTCs of soil samples were used to clarify the effects of N fertilizer application and water content on N efficiency. The results indicate that, after the third FTC, the soil ammonium nitrogen (NH4+-N) level increased significantly. NH4+-N increased with an increase in the initial soil moisture content and decreased with fertilizer levels. Nitrate nitrogen (NO3−-N) decreases with increasing initial soil moisture. The inorganic N increased significantly compared with that in the unfrozen stage, indicating that FTCs promote soil N mineralization. However, high fertilization rates inhibit mineralization. Analysis of variance showed that NO3−-N is sensitive to the N application rate, water content, and salinity (p < 0.05). FTCs and artificial fertilization are the factors that affect N mineralization (p < 0.05). The research results are significant for preventing nitrate leaching and soil acidification during spring plowing and providing a scientific basis for fertilization systems and water environment pollution in improved saline soils. [ABSTRACT FROM AUTHOR]

In order to understand the pathogenicity differentiation of rice blast fungus (Pyricularia oryzae Cavara), a total of 206 isolates of P. oryzae were collected from three Japonica rice regions in Jilin Province, northeast China. Pathogenicity test showed that the reaction pattern of 25 monogenic differential varieties (MDVs) of rice (Oryza sativa L.) demonstrated a wide pathogenic diversity among the isolates. Those MDVs harbor 23 resistance (R) genes with the susceptible variety Lijiangxintuanheigu (LTH) as control. Virulent isolates of MDVs harboring R genes Pish, Pit, Pia, Pii, Pik-s, Pik, Pita (two lines), and Pita-2 (two lines) had high frequencies ranging from 80 to 100%, to MDVs harboring R genes Pib, Pi5(t), Pik-m, Pi1, Pik-h, Pik-p, Pi7(t), Piz, Piz-5, and Piz-t showed intermediate frequencies ranging from 40 to 80%, and to MDVs with R genes Pi3, Pi9(t), Pi12(t), Pi19(t) and Pi20(t) presented low frequencies ranging only from 0 to 40%. The U-i-k-z-ta pattern of race-named criteria categorized the 206 isolates into 175 races. Sub-unit U73 for Pib, i7 for Pi3 and Pi5(t), k177 for Pik-m/Pik-h/Pik-p, z17 for Pi9(t), and ta332 for Pi20(t) were crucial on pathogenic differences in regions. Twenty-seven standard differential blast isolates (SDBIs) were selected to characterize resistance in rice accessions. This study could help to build a durable identification system against blast in the Japonica rice area of northeast China and enhance our understanding of the differentiation and diversity of blast races in the world. [ABSTRACT FROM AUTHOR]

Stavsolus shihu sp. n., a new species of stonefly family Perlodidae is described from the Jilin Province of China, illustrated and compared with the related taxa. Habitat data of the new species are given. [ABSTRACT FROM AUTHOR]

It is necessary to further investigate the spatial considerations, temporal characteristics, and drivers of change affecting the beginning and end of soil freezing and thawing, including the maximum depth of the seasonal freezing (MDSF) and the active layer thickness (ALT) in Northeast China. Hourly soil temperature, among other data, from 1983–2022 were investigated, showing a delay of about 6 days in freezing. In contrast, thawing and complete thawing advanced by about 26 and 20 d, respectively. The freezing period and total freeze-thaw days decreased by about 29 and 23 days, respectively. The number of complete thawing period days increased by about 22 days, while the MDSF decreased by about 25 cm. The ALT increased by about 22 cm. Land Surface Temperature (LST) is the main factor influencing the beginning and end of soil freezing and thawing, MDSF and ALT changes in Northeast China; air temperature, surface net solar radiation, and volumetric soil water content followed. The influence of the interacting factors was greater than the single factors, and the interactive explanatory power of the LST and surface net solar radiation was highest when the soil started to freeze (0.858). The effect of the LST and the air temperature was highest when the soil was completely thawed (0.795). LST and the volumetric soil water content interacted to have the first explanatory power for MDSF (0.866) and ALT (0.85). The results of this study can provide scientific reference for fields such as permafrost degradation, cold zone ecological environments, and agricultural production in Northeast China. [ABSTRACT FROM AUTHOR]

Urban policy implementation in shrinking cities has been problematic due to actors' different interests regarding managing shrinkage issues. This issue is presently influencing shrinking cities in China. Under the pro-growth urban policy at odds with the population decline tendency, actors' responses to policy implementation are complex and bear uncertain impacts on policy implementation outcomes. This paper brings up a conceptual framework from a new institutionalist perspective to uncover the implementation of the pro-growth urban policy in shrinking cities in China from the actors' perspective. An exemplary city, Fushun in Northeast China is investigated. It is found that development discourses in urban policy are reinvented by actors with their diverse responses to policy implementation. A pro-transformation coalition is built with actors collaborating on shared development goals, making compromises and developing new rules to deal of policy implementation issues. This coalition steers urban policy implementation and diverts its outcomes. This paper advances understandings on the forming mechanisms of actors' responses to urban policy implementation in shrinking cities. It is suggested that a collaborating platform with the empowerment of micro-scale networks and capacity should be adopted early on in formal planning processes in China and beyond to sustain the diverse development discourses among actors. • Problematic planning and policy implementation challenges urban development in shrinking cities. • Shrinking cities in China, with built-up area growth and population decline, are challenged in policy implementation. • A perspective built on the new institutionalism theory is developed to study shrinking cities in China. • An empirical study is conducted to study how actor-reinvented discourses and actor relationships shape urban development. • A pro-transform coalition is found among city-level actors and steers urban development in shrinking cities in China. [ABSTRACT FROM AUTHOR]

Studies of the history and current status of forest resources in Northeast China have become important in discussions of sustainable forest management in the region. Prior to 1998, excessive logging and neglected cultivation led to a series of problems that left exploitable forest reserves in the region almost exhausted. A substantial decrease in the area of natural forests was accompanied by severe disruption of stand structure and serious degradation of overall forest quality and function. In 1998, China shifted the primary focus of forest management in the country from wood production to ecological sustainability, adopting ecological restoration and protection as key foci of management. In the process, China launched the Natural Forest Conversion Program and implemented a new system of Classification-based Forest Management. Since then, timber harvesting levels in Northeast China have decreased, and forest area and stocking levels have slowly increased. At present, the large area of low quality secondary forest lands, along with high levels of timber production, present researchers and government agencies in China with major challenges in deciding on management models and strategies that will best protect, restore and manage so large an area of secondary forest lands. This paper synthesizes information from a number of sources on forest area, stand characteristics and stocking levels, and forest policy changes in Northeastern China. Following a brief historical overview of forest harvesting and ecological research in Northeast China, the paper discusses the current state of forest resources and related problems in forest management in the region, concluding with key challenges in need of attention in order to meet the demands for multi-purpose forest sustainability and management in the future. [ABSTRACT FROM AUTHOR]

Under global climate warming, the global water cycle is further accelerating, the risk of drought is increasing, and the instability and sustainability of agricultural production are seriously threatened. Northeast China, as the "granary" of China, located in the mid-high latitudes of the Northern Hemisphere, is one of the regions strongly influenced by droughts. Thus, studying the spatial and temporal distribution of drought is helpful for the development of methods for forecasting potential drought hazards in Northeast China. This study used observed data from 86 meteorological stations in Northeast China from 1961 to 2020 to calculate the standardized precipitation evapotranspiration index (SPEI) at different time scales for the past 60 years and analyzed the spatial and temporal characteristics of drought in Northeast China based on the run theory and the Mann-Kendall test. The SPEI at the annual scale showed decreasing trends with no significant mutation point. Seasonally, there was a decreasing trend of the SPEI in summer and autumn and an increasing trend in spring and winter, which indicates that drought in Northeast China has decreased in winter and spring. The annual drought frequency ranged from 25.5% to 37.6%, and the spatial characteristics of the frequency of moderate drought, severe drought, and extreme drought, respectively, showed the following distribution patterns from the western region to the central region and then to the eastern region of Northeast China: "high-low-high", "low-high-low", and "gradually decreasing". [ABSTRACT FROM AUTHOR]

The Rolling Hilly Region of Northeast China (RHRNEC) is a critical grain production area in China, and soil erosion is a major problem in this region. To determine spatial and temporal changes in rainfall erosivity (RE) in the RHRNEC and generate information useful for soil and water conservation, agricultural management, and ecological protection efforts, a RE index consisting of nine erosivity indices based on normal and extreme precipitation was established. The normal RE index (NREI) comprised annual RE (ARE), wet season RE (WRE), dry season RE (DRE), typical wet-month RE (TWRE), and typical dry-month RE (TDRE), and the extreme RE index set (EREI) comprised maximum one-day RE (RE × 1 day), maximum five consecutive days RE (RE × 5 day), storm RE (RE50), and maximum continuous RE (CRE). ARE, WRE, and TWRE decreased at relative rates of 2.5%, 2.9%, and 4.1%, respectively. By comparison, DRE increased at a non-significant relative rate of 6.3%, and all extreme RE indices decreased at a non-significant rate relative to 1981–2015 mean values. The future trends for all RE indices were predicted to be opposite to historical trends. The future trends and historical trends of all indices exhibited opposite patterns. RE gradually increased from north to south, and WRE, DRE, and all extreme RE indices were significantly negatively correlated with longitude, latitude, and altitude (p < 0.05). ARE, WRE, and TWRE showed increasing trends in the north and south and decreasing trends in the center. The findings are useful for soil and water conservation, especially for agricultural management and ecological protection. [ABSTRACT FROM AUTHOR]

Ecological compensation for cultivated land is a prominent means to coordinate the protection and utilization of cultivated land ecosystems. This study assessed the ecological compensation for cultivated land, considering both the ecological footprint and value of ecosystem services. We used the ecological footprint model to calculate the ecological footprint and ecological carrying capacity of cultivated land, combined with the value of its ecosystem services, with a focus on estimating its ecological compensation standard, and we analyzed the temporal and spatial distribution characteristics of Northeast China. We found that the ecological footprint and ecological carrying capacity of cultivated land showed a fluctuating growth trend in Northeast China from 2000 to 2020, increasing by 288.83 × 105 ha and 131.37 × 105 ha, respectively. The spatial distribution of cultivated land's ecological footprint and ecological carrying capacity showed growth from the southwest to the northeast. The value of its ecosystem services presented an overall trend of growth over the past 20 years, increasing by CNY 13.64 billion, or an increase of 12.47%. In terms of spatial distribution, the trends of the ecological compensation for cultivated land showed obvious differences. This study mainly focused on black soil cultivated land, and its results are helpful for governments in different countries solving similar problems in terms of the ecological compensation for cultivated land. This study will provide a valuable reference to measure the compensation standard scientifically and to provide policy recommendations for sustainable cultivated land's protection and utilization. [ABSTRACT FROM AUTHOR]