Land Area Of China Research Articles

Identifying the flow paths and beneficiary ranges of the sand fixation service: A case‐study in Xilingol League, China

AbstractThe sand fixation service (SFS) is a function of vegetation ecosystems whereby sand is restrained and stabilized. It not only generates ecological benefits for local areas but also affects circulation media such as wind and has an impact on surrounding areas. Therefore, it is urgent to study the flow process and influence of the SFS, so as to provide a theoretical basis for cross‐regional ecological compensation. We chose Xilingol League (shorten as "Xilingol") as the study area and used the hybrid single‐particle Lagrangian integrated trajectory (HYSPLIT) model to comprehensively identify the spatial flow paths (FPs) and beneficiary ranges (BRs) of the SFS from 2000 to 2018. The results showed that there were 726 FPs of the SFS, which were mainly distributed in spring, accounting for 63.50% of the total FPs. The total area of the BRs was 279.50 × 104 km2, accounting for 29.15% of China's land area. The high‐frequency BRs were mainly distributed in the southeast of Inner Mongolia, northern Hebei, northern Liaoning, northern Beijing, and northwestern Jilin. In terms of BRs, farmland was the largest (92.09 × 104 km2) land cover type, accounting for 34.51% of the total area of the BRs, and the total beneficiary population and gross domestic product accounting for 44.53% and 50.06% of whole China in 2015. Identification of FPs and BRs of SFS in this study could provide a reference to make ecology compensation policy at national level.

气候变化对柴胡与狭叶柴胡适生分布的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 气候变化对柴胡与狭叶柴胡适生分布的影响 DOI: 10.5846/stxb202108242369 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家中医药管理局全国中药资源普查项目（GZY-KJS-2018-004）；全国第四次中药资源普查黑龙江专项（2018hljzyzypc-12）；黑龙江省自然科学基金（C2018038） Prediction of distribution pattern and change of suitable areas of Bupleurum chinense and Bupleurum scorzonerifolium under climate change in China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:研究气候变化下物种适生区的分布格局与变迁，对于物种的保护和资源的可持续利用具有重要的理论和实践意义。选取柴胡（Bupleurum chinense）与狭叶柴胡（Bupleurum scorzonerifolium）在中国地域内的381个有效分布点和36个环境因子，利用MaxEnt模型模拟当前以及未来（2050和2070年）两种气候情景下（RCP4.5和RCP8.5）其适生区的分布格局，并分析了制约其适生区分布的主导环境因子。结果表明：（1）影响柴胡适生区分布的主导环境因子为最湿月份降水量、最干季度平均温度以及海拔。影响狭叶柴胡适生区分布的主导环境因子为最湿月份降水量、温度季节性变化标准差以及海拔；（2）当前气候条件下，柴胡适生区总面积为1.4755×106km2，约占我国国土面积的15.37%，中、高度适生区主要分布在陕西南部、山西东部、甘肃东南部、山东中部、河北中西部等地；狭叶柴胡适生区总面积为1.8034×106km2，约占我国国土面积的18.78%，中、高度适生区主要分布在黑龙江西部和东部、内蒙古中部和东北部、河北北部、陕西中部等地。（3）未来气候背景下，两种柴胡总适生区面积呈现增加趋势。柴胡适生区分布质心向东北方向的高纬度地区迁移，狭叶柴胡适生区分布质心向西部方向的高海拔地区迁移。 Abstract:It is of great theoretical and practical importance to study the distribution patterns and changes of species suitable geographical distribution areas under the background of climate change for the protection of species and the sustainable use of resources. In this study, 381 effective distribution sites of Bupleurum chinense and Bupleurum scorzonerifolium in China (excluding duplicate, invalid and cultivated distribution sites) and 36 environmental factors (terrain, soil and climate data) were selected. Baesd on the data mentioned above, the spatial distribution patterns of the suitable geographical distribution areas, B. chinense and B. scorzonerifolium, were simulated by the maximum entropy (MaxEnt) model under current climate and two climate scenarios (RCP4.5 and RCP8.5) for the future (2050 and 2070), respectively. Meanwhile, the dominant environmental factors that restrict the distribution of these two species suitable geographical distribution areas were analyzed. The results show that (1) Precipitation of wettest period (Bio13) was the most important environmental factor affecting the suitable geographical distribution areas of B. chinense, followed by mean temperature of driest quarter (Bio09), and altitude (Elevation). In the same way, precipitation of wettest period (Bio13), temperature seasonality (Bio04), and altitude (Elevation) are the dominant environmental factors that affect the distribution of B. scorzonerifolium suitable geographical distribution areas. (2) Under the current climate conditions, the total area of suitable geographical distribution areas for B. chinense is 1.4755×106km2, which is account for about 15.37% of the total land area of China. And the middle and high suitable geographical distribution areas are mainly distributed in southern Shaanxi, eastern Shanxi, southeastern Gansu, central Shandong, central and western Hebei, etc. At the same time, the total area of suitable geographical distribution areas for B. scorzonerifolium is 1.8034×106km2, accounting for approximately 18.78% of the total land area of China, of which the middle and high suitable geographical distribution areas are mainly distributed in western and eastern Heilongjiang, central and northeastern Inner Mongolia, northern Hebei and central Shaanxi, etc. (3) Under the background of future climate change, the total suitable geographical distribution area of two species of Bupleurum both shows an increasing trend. In term of the migration study of suitable geographical distribution geometric center, the suitable geographical distribution geometric center of B. chinense will step by step move to the high latitude area in the northeast, while the suitable geographical distribution geometric center of B. scorzonerifolium will gradually migrate to the high altitude areas in the west. 参考文献 相似文献 引证文献

Disentangling the roles of land-use-related drivers on vegetation greenness across China

Quantifying the drivers of terrestrial vegetation dynamics is critical for monitoring ecosystem carbon sequestration and bioenergy production. Large scale vegetation dynamics can be observed using the leaf area index (LAI) derived from satellite data as a measure of ‘greenness’. Previous studies have quantified the effects of climate change and carbon dioxide (CO2) fertilization on vegetation greenness. In contrast, the specific roles of land-use-related drivers (LURDs) on vegetation greenness have not been characterized. Here, we combined the Interior-Point Method-optimized ecosystem model and the Bayesian model averaging statistical method to disentangle the roles of LURDs on vegetation greenness in China from 2000 to 2014. Results showed a significant increase in growing season LAI (greening) over 35% of the land area of China, whereas less than 6% of it exhibited a significantly decreasing trend (browning). The overall impact of LURDs on vegetation greenness over the whole country was comparatively low. However, the local effects of LURDs on the greenness trends of some specified areas were considerable due to afforestation and urbanization. Southern Coastal China had the greatest area fractions (35.82% of its corresponding area) of the LURDs effects on greening, following by Southwest China. It was because of these economic regions with great afforestation programs. Afforestation effects could explain 27% of the observed greening trends in the forest area. In contrast, the browning impact caused by urbanization was approximately three times of the greening effects of both climate change and CO2 fertilization on the urban area. And they made the urban area had a 50% decrease in LAI. The effects of residual LURDs only accounted for less than 8% of the corresponding observed greenness changes. Such divergent roles would be valuable for understanding changes in local ecosystem functions and services under global environmental changes.

Predicting Possible Distribution of Tea (Camellia sinensis L.) under Climate Change Scenarios Using MaxEnt Model in China

Climate change has dramatic impacts on the growth and the geographical distribution of tea (Camellia sinensis L.). Assessing the potential distribution of tea will help decision makers to formulate appropriate adaptation measures to use the altered climatic resources and avoid the damage from climate hazards. The objective in this study is to model the current and future distribution of tea species based on the four SSPs scenarios using the MaxEnt model in China. For the modeling procedure, tea growth records in 410 sites and 9 climate variables were used in this paper. The area under the receiver operating characteristic (ROC) curve (AUC) was used to evaluate the performance of the model. The AUC value was over 0.9 in this study, showing the excellent simulation result of the model. In relation to the current distribution, areas of 82.01 × 104 km2 (8.51% of total land area in China), 115.97 × 104 km2 (12.03% of total land area in China), and 67.14 × 104 km2 (6.97% of total land area in China) were recognized as Marginal, Medium, and Optimal climate suitable habitats for tea over China. Compared to the current distribution, most of the Optimal suitability areas in southeast China would be lost in four scenarios. The area of Marginal and Medium suitable habitats would expand in SSP370 and SSP585, especially in 2041–2061 and 2081–2100. The suitable area of tea would expand northwards and westwards, suggesting that additional new suitable habitats could be created for tea production with the future climate change, especially in Shandong, Henan, Guizhou, and Yunnan Provinces. This research would provide vital scientific understanding for policy making on tea production, tea garden site chosen and adopyion of adaptation methods in the future.

Dynamic analysis of mixed forest species under climate change scenarios

The outstanding self-regulation ability of mixed forest plays an important role in maintaining ecosystem stability. However, in recent years, climate change has caused geographical changes of species. This paper studies the potential geographical location of mixed species for the first time, so as to formulate the planting plan of mixed species in suitable areas. Therefore, we use the species distribution model based on Maxent to predict the potential suitable area of Chinese Pinus tabuliformis and Ostryopsis davidiana mixed forest under the climate change scenario, and provide a scientific basis for expanding the construction of P. tabuliformis and O. davidiana mixed forest in the future under three greenhouse gas emission scenarios (RCP2.6, RCP4.5 and RCP8.5) of current and future climate (2041–2060 and 2081–2100). The simulation accuracy of Maxent model is verified by the area under receiver operating characteristic curve (AUC ). The results show that the distribution range of P. tabuliformis is much larger than that of O. davidiana in China. Under the current climate conditions, the overlapping area of medium to highly suitable growing areas of P. tabuliformis and O. davidiana is 64.40 × 104 km2, accounting for 6.71% of China's land area, mainly distributed in most areas of North China, Northeast China (Western Liaoning), Northwest China (Shaanxi, Ningxia, the Southernmost part of Inner Mongolia and Eastern Gansu) and Central China (Northern Hubei). Under the future high concentration emission scenario (RCP8.5), the overlapping area of medium to highly suitable growing areas of P. tabuliformis and O. davidiana will be reduced. Under the scenario of medium concentration climate emission (RCP 4.5), the centroids of P. tabuliformis and O. davidiana tend to migrate from west to north. The annual mean temperature (bio1) has a significant effect on the geographical distribution of P. tabuliformis and O. davidiana. In addition, the mean temperature of the driest quarter (bio9) and annual precipitation (bio12) also have a significant impact on the geographical distribution of P. tabuliformis. Similarly, there are obvious factors on the geographical distribution of O. davidiana, as well as isothermality (bio3) and precipitation of the wettest quarter (bio16), indicating that the important climate factors affecting the geographical distribution of P. tabuliformis and O. davidiana are not completely consistent. We believe that mixed forests play a positive role in coping with climate change. The research results can help decision-makers to formulate adaptation countermeasures based on climate change.

Soil salinity variations and cotton growth under long-term mulched drip irrigation in saline-alkali land of arid oasis

The sustainable development and utilization of saline-alkali land are closely related to holding fast the minimum cultivated land area of China. The change of soil salt in cotton field under long-term mulched drip irrigation (MDI) is connected with the development of the national cotton industry. From 2015 to 2019, five cotton fields with different applying years of MDI, which were reclaimed in 2004, 2008, 2010, 2012 and 2015 respectively and were saline-alkali wasteland before, were monitored continuously in the Manas River irrigation area of Xinjiang. By means of continuous location monitoring and spatial–temporal variability (For example, the monitoring data of cotton fields under MDI in 2004, 2008, 2010, 2012 and 2015, and in the year of 2015 were counted as 12, 8, 6, 4 and 1 years, respectively), the spatial–temporal variations of soil salt and ions in cotton field with 1-16a MDI technology were presented. The cotton growth characteristics and its main influencing factors were also analyzed in the study. The results showed that saline-alkali cotton field experienced changed from intensive saline soil to moderate saline soil and finally to non-saline soil under long-term MDI. The change of soil salt and the response of cotton growth to soil salt were divided into three typical stages. Firstly, soil desalinated rapidly in 1-4a MDI cotton field, which the annual average desalination rate was 24.93% in 0–100 cm soil layer (root zone). Additionally, the survival rate of cotton rocketed from 1.48% to 42.04%, and yield increased sharply from 72.43 kg ha−1 to 3075.90 kg ha−1. Soil desalination was lower in 5-11a MDI cotton field, which the annual average desalination rate was 10.92% at the root zone. The annual survival rate and yield of cotton increased by 6.26% and 5.18%, respectively. After 12a MDI, the soil salt in cotton field tended to be generally constant, which the average salt content in root zone was less than 2.49 g kg−1. The survival rate of cotton was stable above 90.39%, and the yield per unit area exceeded 5401.32 kg ha−1. Ions, sodium absorption ratio and Cl− and SO42− equivalent ratio (CSER) in cotton soil also decreased with the extension of MDI. Salt composition changed year by year, but the type of intensive saline soil had always been chloride-sulphate solonchak (0.2 < CSER < 1). In practice, with a higher irrigation quota and ideal irrigation water quality, the soil salt environment of saline-alkali soil MDI cotton field had developed in favor of cotton growth in an oasis irrigation area. However, this management practice caused between 124.21–143.61 mm of water resources waste. Therefore, we should further enhanced the consciousness of water-saving and implemented quota management in practice.

Characterization of Dissolved Organic Matter and Its Derived Disinfection Byproduct Formation along the Yangtze River.

The Yangtze River basin covers one-fifth of China's land area and serves as a water source for one-third of China's population. During long-distance water transport from upstream to downstream, various sources of dissolved organic matter (DOM) lead to considerable variation in DOM properties, significantly impacting water treatability and disinfection byproduct (DBP) formation after chlorination. Using size-exclusion chromatography and fluorescence spectroscopy, the spatial variation in DOM characteristics was comprehensively investigated on a basin scale. The formation of 36 DBPs and speciated total organic halogen in chlorinated samples was determined. Overall, the Yangtze River waters featured a high proportion of terrestrially derived humic substances that served as important precursors for trihalomethanes and haloacetic acids, which was responsible for the increase in total DBP formation along the Yangtze River. The downstream waters were characterized by high levels of microbially derived protein-like biopolymers, which significantly contributed to the formation of haloacetaldehydes and haloacetonitriles that dominated DBP-associated mammalian cell cytotoxicity. Moreover, the precursors of haloacetaldehydes and haloacetonitriles in downstream waters were highly hydrophilic, posing a challenge for water treatment. This study presents an extensive basin-scale study, providing insights into DOM variations along the Yangtze River, illustrating the impact of DOM properties on drinking water from a DBP perspective.

Effects of climate changes on the distribution of Rhipicephalus microplus in China

To identify the environmental factors affecting the geographical distribution of Rhipicephalus microplus in China, and to examine the impact of climate changes on the distribution of R. microplus in China. The national and international publications pertaining to the geographical distribution of R. microplus in China were retrieved, and the geographical location was extracted. The suitable habitats of R. microplus and the dominant environmental factors affecting the distribution of suitable habitats of R. microplus were predicted in China based on the geographical data and environmental variables using the ArcGIS 10.7 software and the maximum entropy model. Among the main climatic factors affecting the geographical distribution of R. microplus in China, the factors contributing more than 10% to the suitable habitats of R. microplus mainly include the annual mean precipitation (38.2%), the average temperature of the coldest quarter (28.4%) and the precipitation of the driest month (14.2%). The current suitable habitats of R. microplus were mainly found in southern China, and the high-, medium- and low-suitable areas accounted for 8.6%, 13.1% and 10.5% of the total land area of China, respectively. The suitable habitats of R. microplus were predicted to increase by 399 800 km2 in China using the maximum entropy model under the RCP 4.5 emissions scenario in 2070, and the emerging suitable habitats were mainly distributed in Gansu Province, Ningxia Hui Autonomous Region, Qinghai Province, Hebei Province, Shaanxi Province, Liaoning Province, Inner Mongolia Autonomous Region, Shandong Province, Sichuan Province and Tibeten Autonomous Region. In addition, the suitable habitats of R. microplus were predicted to show an overall expansion towards northward from present to 2070. Climate changes affect the distribution of suitable habitats of R. microplus in China, and annual mean precipitation may be a key factor affecting the distribution of suitable habitats of R. microplus.

Effects of environmental factors on the distribution of suitable habitats of Ixodes ovatus in China

To identify the environmental factors affecting the distribution of suitable habitats of Ixodes ovatus, and to examine the effects of environmental changes on the distribution of suitable habitats of I. ovatus. Data pertaining to the distribution of I. ovatus in China were captured by literature review. The distribution of suitable habitats of I. ovatus in China was simulated using the maximum entropy model with the environmental variable data and the I. ovatus distribution data. In addition, the potential distribution of suitable habitats of I. ovatus was predicted based on the 2050 and 2070 environmental data. The current suitable habitats of I. ovatus cover 3.11 million km2, accounting for 32.28% of the total land area of China, and they are mainly concentrated in southwestern and northwestern China. Among the screened 16 environmental factors, the standard deviation of seasonal variation of temperature, average annual precipitation and altitude were predominant environmental factors affecting the distribution of suitable habitats of I. ovatus, and these three variables contributed 76.5% to the distribution of suitable habitats of I. ovatus in China. The suitable habitats of I. ovatus were predicted to showing a tendency towards expansion to northwestern and northeastern China in 2050 and 2070, and the proportion of highly suitable habitats of I. ovatus was predicted to increase. Moderate climate, adequate precipitation and high altitude are favorable for the survival of I. ovatus. Future climate changes may cause expansion of suitable habitats of I. ovatus in China.

Effects of Different Organic Fertilizers on Improving Soil from Newly Reclaimed Land to Crop Soil

The rapid development of cities in the recent 10 years caused a reduction in the cultivated land area, which only accounts for 14% of the total land area in China. Land development and reclamation have been regarded as an effective way to compensate farmland occupation. However, most of the newly reclaimed land has poor soil fertility and suitability; in some cases, the production capacity is only 10–30% of the occupied farmland. In order to ameliorate the soil quality of the newly reclaimed land, this study evaluated the effects of commercial organic fertilizer (0.75, 1.50, and 2.25 kg/m2), mushroom residue (1.50, 2.25, and 3.00 kg/m2), biogas slurry (150, 225, and 300 kg/m2), vegetable cake (0.30 and 0.60 kg/m2), and chemical compound fertilizer (37.50 g/m2) on the pH, moisture content and organic matter content (OMC), available phosphate, total nitrogen, alkaline hydrolysis nitrogen, microbial biomass carbon and nitrogen, and number of total bacteria and phosphate-solubilizing bacteria, as well as the growth of maize seedlings. The results from this study indicate that the soil quality (OMC is an indicator) was ameliorated by chemical and organic fertilizers, in particular commercial organic fertilizers, which caused a 9.35–16.35% increase in moisture content, a 11.56–18.72% increase in pH, a 1.73–2.15 fold increase in OMC, a 338.44–491.41% increase in available P, a 36.80–48.14% increase in total N, a 95.32–128.34% increase in alkaline hydrolysis N, a 92.57–178.38% increase in total bacterial numbers, and a 7.57–20.87 fold increase in microbial biomass carbon compared with the control. The pot experiment further indicated that soil amended with commercial organic fertilizers caused a 20.35–30.55% increase in the height and a 12.50–16.67% increase in the total dry weight of maize seedlings. In addition, representative strains with the ability to dissolve phosphorus and fix nitrogen were successfully isolated using the culture method, and were then identified based on colony morphological observation and 16S rDNA sequence analysis, which help us to not only understand why organic fertilizer has great effect on soil improvement, but also provides beneficial microbial resources for further study.

Modeling climatically suitable areas for soybean and their shifts across China

CONTEXTCrop suitability determines its distribution and yield in a given region and can be greatly affected by climate change. In recent decades, the distribution of soybean cultivation has undergone significant spatial shifts in China. However, whether this change matches with climatic suitability for soybean at a national scale has not been reported. OBJECTIVEOur objectives were to investigate the spatial distribution and shifts in climatically suitable areas for soybean from 1961 to 2017 and to determine whether actual production matches with climatic suitability in China. METHODSThe MaxEnt model was used to simulate the presence probability of soybean from 1961 to 2017 based on soybean occurrence data and climate data across China. Regions were classified as climatically unsuitable or as having low, moderate, or high climatic suitability. Then, the overlay analysis was performed to assess spatial changes of soybean suitability and the consistency between climatic suitability and actual production. RESULTS AND CONCLUSIONSAccumulated temperature ≥ 10 °C, humidity index during the potential growing season, and annual temperature range were the major climatic factors that affected soybean distribution. Areas of high climatic suitability were mainly located in the Northeast and North-central Regions, and the total acreage of high suitability was 129.88 × 106 ha. Unsuitable areas for soybean contracted over the study period, whereas highly suitable areas migrated westward and southward. The climatic suitability for soybean across China has increased overall in the past decades. The area of improved climatic suitability from 1961 to 2017 comprised 14.60% of the entire land area of China and was concentrated primarily in the Northwest and North-central Regions. Nonetheless, consistency between climatic suitability and actual production decreased from 83.47% in 1985 to 65.16% in 2015. This may pose a risk to soybean production, especially in emerging major planting areas of the Southwest Region. SIGNIFICANCEThis study described the distribution of climatically suitable areas for soybean, used spatial analysis to illustrate the extent to which climatically suitable areas overlap with actual production areas, and discussed possible solutions for improving soybean production at a national scale in China. This work has practical significance for optimizing the regional layout of soybean production and implementing countermeasures to address future climate change.

Spatio-Temporal Differentiation of Trade-Offs and Synergies of Ecosystem Services in Typical Mountain Areas of China

Mountain area accounts for a high proportion of the land area in China, and it is the focal area to solve the contradiction of imbalanced regional development, as well as an important source of ecosystem services. Therefore, this area has been facing long-term pressure and challenges in economic development and ecological protection. In this paper, we selected a rocky desertification mountain area, an active mountain area of new tectonic movement and a typical northern earth-rock mountain area, as Qian-Gui karst Mountain area, Hengduan Mountain area and Taihang Mountain area, as examples to represent three main types of mountain areas. Three representative types of ecosystem services, including NPP (Net Primary Productivity) as a support service, water conservation as a regulation service, and agricultural produce as a supply service, were incorporated into this study. Linear regression, correlation analysis and other methods were then used to investigate the spatial-temporal characteristics of the trade-offs and synergies in each of the three kinds of mountain areas during 1990-2015 in China. The analysis yielded three main conclusions for the three mountainous areas. (1) The agricultural produce supply service decreased relatively, while the support and regulation services of NPP and hydrological regulation increased significantly. (2) There was a synergistic relationship between NPP and the hydrological regulation services in the three mountainous areas. The synergistic relation in Qian-Gui karst Mountain area became enhanced, while those in Hengduan and Taihang Mountain areas became weakened, and the former was weakened to a greater extent. There was a trade-off between NPP, the hydrological regulation service and the agricultural produce supply service among the three mountainous areas. In particular, the trade-off between NPP and the agricultural produce supply service in Qian-Gui karst Mountain area became weaker, while those in Hengduan and Taihang Mountain areas were enhanced, and the latter was enhanced to a greater degree. (3) Significant spatial differentiation was evident in the trade-offs and synergies of ecosystem services among the three mountain areas.

Mechanisms of salt rejection at the ice-liquid interface during the freezing of pore fluids in the seasonal frozen soil area

Seasonal frozen soil accounts for about 53.50% of the land area in China. Frozen soil is a complex multiphase system where ice, water, soil, and air coexist. The distribution and migration of salts in frozen soil during soil freezing are notably different from those in unfrozen soil areas. However, little knowledge is available about the process and mechanisms of salt migration in frozen soil. This study explores the mechanisms of salt migration at the ice-liquid interface during the freezing of pore fluids through batch experiments. The results are as follows. The solute concentrations of liquid and solid phases at the ice-liquid interface (CL*, CS*) gradually increased at the initial stage of freezing and remained approximately constant at the middle stage. As the ice-liquid interface advanced toward the system boundary, the diffusion of the liquid phase was blocked but the ice phase continued rejecting salts. As a result, CL* and CS* rapidly increased at the final stage of freezing. The distribution characteristics of solutes in ice and the liquid phases before CL* and CS* became steady were mainly affected by the freezing temperature, initial concentrations, and particle-size distribution of media (quartz sand and kaolin). In detail, the lower the freezing temperature and the better the particle-size distribution of media, the higher the solute proportion in the ice phase at the initial stage of freezing. Meanwhile, the increase in concentration first promoted but then inhibited the increase of solutes in the ice phase. These results have insights and scientific significance for the tackling of climate change, the environmental protection of groundwater and soil, and infrastructure protection such as roads, among other things.© 2021 China Geology Editorial Office.

气候变化和人类活动对中国陆地生态系统总初级生产力的影响厘定研究

总初级生产力（GPP）是生态系统植被光合作用生成有机物的能力表征，是生态系统服务功能的基础，关系到区域社会经济可持续发展及区域生态安全。基于生态系统过程模型CEVSA2，应用中分辨率成像光谱仪（MODIS）卫星遥感的叶面积指数数据产品（MCD15A2H），以强迫法构建了遥感数据驱动的模型新版本——CEVSA-RS；基于CEVSA-RS模拟分析了气候变化和人类活动对中国陆地生态系统GPP时空变化的相对影响，从气候潜在总初级生产力（GPP_CL）和现实总初级生产力（GPP_RS）的大小和趋势两方面厘定了人类活动影响。2000至2017年全国平均潜在GPP （1016.36 gC m^-2a^-1）略高于对应现实GPP （962.85 gC m^-2a^-1），但存在明显的空间分异：长江以南大部、秦岭、太行山脉以东以及大兴安岭以东和长白山地区等森林植被覆盖区，现实GPP高于潜在GPP；而西部草地及灌丛等地区现实GPP低于潜在GPP。全国GPP呈显著增加趋势（P<0.05），其中现实GPP的增速（46.04 gC m^-210a^-1）高于潜在GPP的增速（41.46 gC m^-210a^-1），人类活动影响促进GPP增长，主要体现在华南地区和华北平原等地；内蒙古东部、东北平原北部、青藏高原西部等地人类活动呈负面影响。人类活动影响大于气候影响的区域可达全国陆地面积的53%，其中西部生态相对脆弱的草地区人类活动仍为负面影响，这些地区以草定畜，发展草牧业和保护生态，仍然任重道远。;Gross primary productivity (GPP) is the fundament of all ecological services that ecosystems can provide, and its change will influence the sustainable development of regional socio-economic and ecological security. Based on the ecosystem process model CEVSA2, this study applied the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite remote sensing data to construct a new version of the remote sensing data-driven model, CEVSA-RS. The relative impacts of climate change and human activities on the spatial and temporal changes of terrestrial ecosystem gross primary productivity were analyzed based on CEVSA-RS, and the impacts of human activities were determined in terms of both the magnitude and trends of potential gross primary productivity (GPP_CL) driven by climate and actual gross primary productivity (GPP_RS) driven by climate and remote sensing. According to the national average, potential GPP (1016.36 gC m^-2a^-1) was slightly higher than actual GPP (962.85 gC m^-2a^-1) from 2000 to 2017. However, there is an obviously spatial disparity:the actual GPP is higher than the potential GPP in forested vegetation cover areas such as most of the south of the Yangtze River, the east of the Qinling and Taihang Mountains, and the east of the Daxinganling and Changbai Mountain areas. Meanwhile, the actual GPP is lower than the potential GPP in areas such as grassland and shrubland over western China. The GPP of whole Chinese terrestrial ecosystems showed a significant increasing trend (P<0.05), and the increasing speed of actual GPP (46.04 gC m^-210a^-1) exceeded that of potential GPP (41.46 gC m^-210a^-1), which meant human activities positively contributed to the most area in South China and North China Plain, while negatively impacted the ecosystems in eastern Inner Mongolia, northern Northeast Plains and western Tibetan Plateau. The areas where the impacts of human activities are greater than the impacts of climate chang accounted for 53% of the total land area in China. Considering negative impacts of human activities in the western China, as an area of fragile eco-environment, there is a long way to protect its ecosystems while to develop grassland-based husbandry through determining livestock stocking rate according forage production.

Projected Changes in Abrupt Shifts Between Dry and Wet Extremes Over China Through an Ensemble of Regional Climate Model Simulations

AbstractThe dry‐wet abrupt alternation (DWAA) event, which is defined as the phenomenon of dry (or wet) spells abruptly following wet (or dry) spells, magnifies the influence of individual wet and dry events. The dynamic evolution of DWAA events has not been studied for different climate zones of China that is particularly susceptible to dry and wet extremes. This study explores the future changes in the abrupt alternations between dry and wet extremes across 10 climate divisions of China, with a thorough assessment of dry and wet conditions using the Standardized Precipitation Evapotranspiration Index (SPEI). We take advantage of an ensemble of regional climate model simulations including the Providing Regional Climate Impacts for Studies (PRECIS) experiment and five CORDEX East Asia experiments to produce high‐resolution climate information for a baseline period of 1975–2004 and a future period of 2069–2098. Our findings disclose that a total of 70% of China's land area suffered from the DWAA events at least once during 1975–2004. The wet‐dry alternation event is projected to become more frequent in summer, and a prominent increase in the number of dry‐wet alternation events is expected to occur in spring over most parts of China. Moreover, an increasing number of DWAA events with intensified magnitude is projected to strike the North China Plain dominated by warm temperature and humid zone, which is the most densely populated region of the country and is also the largest agriculture production area. Our findings also reveal a strong positive correlation between DWAA and heavy rainfall. The 95th percentile rainfall event contributes most to the wet‐dry alternation event for most climate divisions of China.

Mapping Sandy Land Using the New Sand Differential Emissivity Index From Thermal Infrared Emissivity Data

On the basis of the spectral shape of thermal infrared (TIR) emissivity for sandy land, a remote sensing sand index called the sand differential emissivity index (SDEI) is proposed in this article to simply and conveniently detect sandy land over large areas. The SDEI is evaluated on ground, airborne, and spaceborne thermal emissivity data, and it shows good characterization of sandy land and performs better in sandy land identification than two previous indices. The SDEI was also evaluated in the transition zones of China's four mega-sandy lands and was applied to long-term land surface emissivity to obtain the spatial distribution and variation in China's sandy land from 2000 to 2016. The findings showed that a mean accuracy of 96% and a mean kappa coefficient of 0.83 were obtained in the transition zones, and the sandy land in the transition zone exhibited a decreasing trend over the past 17 years and a significant decline in the Mu Us sandy land. Meanwhile, the sandy land area in China decreased by 3.6×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (1.53%) by the end of 2016 compared with that in early 2000.

Evaluation of High-Resolution Crop Model Meteorological Forcing Datasets at Regional Scale: Air Temperature and Precipitation over Major Land Areas of China

Air temperature and precipitation are two important meteorological factors affecting the earth’s energy exchange and hydrological process. High quality temperature and precipitation forcing datasets are of great significance to agro-meteorology and disaster monitoring. In this study, the accuracy of air temperature and precipitation of the fifth generation of atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ERA5) and High-Resolution China Meteorological Administration Land Data Assimilation System (HRCLDAS) datasets are compared and evaluated from multiple spatial–temporal perspectives based on the ground meteorological station observations over major land areas of China in 2018. Concurrently, the applicability to the monitoring of high temperatures and rainstorms is also distinguished. The results show that (1) although both forcing datasets can capture the broad features of spatial distribution and seasonal variation in air temperature and precipitation, HRCLDAS shows more detailed features, especially in areas with complex underlying surfaces; (2) compared with the ground observations, it can be found that the air temperature and precipitation of HRCLDAS perform better than ERA5. The root-mean-square error (RMSE) of mean air temperature are 1.3 °C for HRCLDAS and 2.3 °C for ERA5, and the RMSE of precipitation are 2.4 mm for HRCLDAS and 5.4 mm for ERA5; (3) in the monitoring of important weather processes, the two forcing datasets can well reproduce the high temperature, rainstorm and heavy rainstorm events from June to August in 2018. HRCLDAS is more accurate in the area and magnitude of high temperature and rainstorm due to its high spatial and temporal resolution. The evaluation results can help researchers to understand the superiority and drawbacks of these two forcing datasets and select datasets reasonably in the study of climate change, agro-meteorological modeling, extreme weather research, hydrological processes and sustainable development.

Formation mechanism analysis of irrigation-induced retrogressive loess landslides

The Loess Plateau covers about 6.6% of the total land area of China. Landslides are serious concerns in Loess Plateau of China, and the south Jingyang tableland on the Loess Plateau of China has received significant attention because of frequent occurrence of gradual retrogressive loess landslides (GRLL) there. However, the characteristics and mechanism of GRLL are largely unknown. In this study, three typical landslide groups, namely, Miaodian-zaitou landslide group, Jiangliu landslide group and Dabuzi landslide group are chosen as examples to analyze the characteristics of GRLL by performing a field survey and undrained triaxial shear tests. Loess fissures are found to play a key role in controlling the evolution of landslides. On the one hand, the mechanical properties of loess surrounding fissures rapidly weaken due to water infiltration into loess fissures. On the other hand, the self-weight of the overlying loess increases since water infiltrates into fissures. The undrained triaxial shear tests results indicate that loess specimen shows either strain-hardening or strain-softening behavior, depending on its initial moisture content. Furthermore, reduction in the shear strength of loess samples is observed as moisture content increases. Three factors associated with the characteristics and mechanism of GRLL group, including strata lithology, slope shape, irrigation and rainfall are discussed. Finally, the formation mechanism and evolution of GRLL are summarized into three stages, namely, a creep-tensional stage, a localized liquefaction stage and a sliding stage. This study provides important insights on gradual retrogressive characteristics of loess landslides and facilitates appropriate safeguards to reduce the risk of such landslide hazards.

Coxiella burnetii is widespread in ticks (Ixodidae) in the Xinjiang areas of China

BackgroundThe gram-negative Coxiella burnetii bacterium is the pathogen that causes Q fever. The bacterium is transmitted to animals via ticks, and manure, air, dead infected animals, etc. and can cause infection in domestic animals, wild animals, and humans. Xinjiang, the provincial-level administrative region with the largest land area in China, has many endemic tick species. The infection rate of C. burnetii in ticks in Xinjiang border areas has not been studied in detail.ResultsFor the current study, 1507 ticks were collected from livestock at 22 sampling sites in ten border regions of the Xinjiang Uygur Autonomous region from 2018 to 2019. C. burnetii was detected in 205/348 (58.91%) Dermacentor nuttalli; in 110/146 (75.34%) D. pavlovskyi; in 66/80 (82.50%) D. silvarum; in 15/32 (46.90%) D. niveus; in 28/132 (21.21%) Hyalomma rufipes; in 24/25 (96.00%) H. anatolicum; in 219/312 (70.19%) H. asiaticum; in 252/338 (74.56%) Rhipicephalus sanguineus; and in 54/92 (58.70%) Haemaphysalis punctata. Among these samples, C. burnetii was detected in D. pavlovskyi for the first time. The infection rate of Rhipicephalus was 74.56% (252/338), which was the highest among the four tick genera sampled, whereas the infection rate of H. anatolicum was 96% (24/25), which was the highest among the nine tick species sampled. A sequence analysis indicated that 63 16S rRNA sequences could be found in four newly established genotypes: MT498683.1 (n = 18), MT498684.1 (n = 33), MT498685.1 (n = 6), and MT498686.1 (n = 6).ConclusionsThis study indicates that MT498684.1 might represent the main C. burnetii genotype in the ticks in Xinjiang because it was detected in eight of the tick species studied. The high infection rate of C. burnetii detected in the ticks found in domestic animals may indicate a high likelihood of Q fever infection in both domestic animals and humans.

QUALITY INSPECTION AND EVALUATION OF SATELLITE ORTHOPHOTOS IN CHINA'S THIRD NATIONAL LAND SURVEY

Abstract. Satellite orthophotos are important data sources and results of China's third national land survey, and their quality profoundly affects the accuracy of the survey results. This article reviews the quality requirements and quality models of satellite orthophotos for the purpose of land survey in conjunction with the quality inspection and evaluation of satellite orthophotos covering the entire land area of China, and analyzes the shortcomings of current orthophotos quality evaluation methods. On the basis of this method, a multilevel fuzzy comprehensive evaluation method was introduced to test the orthophotos quality evaluation, and the concepts of maximum membership effectiveness index and evaluation grade probability were used to constrain the evaluation results. The results prove that the method is more effective than the current method true and accurate.