摘要：
湖泊与水库作为地表水资源的重要载体,是中国特大、大中型城市最重要的集中型供水源地和最基本的地理单元,兼具供水、防洪、维系生物多样性等诸多功能,与人类生产生活息息相关。湖泊科学是地理科学的重要组成部分,加强湖泊科学基础研究...展开更多 湖泊与水库作为地表水资源的重要载体,是中国特大、大中型城市最重要的集中型供水源地和最基本的地理单元,兼具供水、防洪、维系生物多样性等诸多功能,与人类生产生活息息相关。湖泊科学是地理科学的重要组成部分,加强湖泊科学基础研究对于助力中国生态文明建设具有重要意义。国家自然科学基金是中国基础科学研究资助的主渠道,自然科学基金申请书在一定程度上反映了各研究领域前沿与热点。经过梳理,1986—2022年间地理科学学科的自然科学基金申请书标题中含“湖”和“水库”的共2347份,对其中的关键词等信息的分析表明:(1)湖泊科学申请书数量增长主要集中在2004—2011年和2018—2022年两个时段。(2)1986—2022年D0105(景观地理与综合自然地理)和D0113(遥感科学)两个二级代码下申请书数量占比分别达25.0%±8.9%和19.8%±5.5%。(3)“鄱阳湖”“太湖”“洞庭湖”“青藏高原”“三峡水库”等研究区出现频次较高,“机制”“湿地”“流域”“遥感”等研究内容与方法热词出现频次较高,这与Web of Science及中国知网等平台上热词检索结果大致吻合。(4)在湖泊科学领域提交申请书数量较多的依托单位依次为中国科学院南京地理与湖泊研究所、江西师范大学、中国科学院青藏高原研究所。未来国家自然科学基金委员会地理科学学科将进一步优化学科布局与关键词设置,增强跨领域跨学科交叉,引导聚焦湖泊科学基础理论与前沿热点问题,促进中国湖泊科学研究的高质量发展。收起
关键词：
agricultural production potential;cropland change;cropland quality;Hubei Province;RCBF policy
摘要：
Abstract Cropland quantity and quality are two important indicators for determining agricultural production. However, few studies integrate them at the pixel level for a comprehensive assessment of food production potential. Consequently, it is hard to evaluate the implementation effectiveness of China's Requisition–Compensation Balance of Farmland (RCBF) policy, which requires balances in cropland quality and quantity for land exploitation. Here, we presented a novel framework to assess the impacts of cropland change on food production potential by combining cropland quantity and quality from pixel to county level. The cropland quantity was defined as cropland gain or loss calculated by 30‐m land cover datasets, while cropland quality was characterized by the integration of climate, terrain, and soil factors using a fuzzy comprehensive evaluation method. Then, nine distinct patterns, reflecting the interdependence between changed cropland area and production potential, were identified to represent the implementation effectiveness of RCBF policy for each county. Results showed cropland area decreased by 1.85% during 2005–2015 in Hubei Province, which mainly occurred in regions with moisture climate and very flat terrain. A majority of croplands with the best soil fertility remained relatively stable during this period. The pattern “more occupation than compensation” was the dominant way of implementing RCBF in Hubei. Four counties positively responded to RCBF, for which the compensatory croplands had superior quality than occupied croplands. This study presented an efficient way to evaluate the impacts of cropland change on agricultural production potential, which provides valuable insights for researchers and decision‐makers to strengthen practices and improve policies for land reclamation and consolidation.
摘要：
Current assessments of urban forest carbon storage were missing or largely underestimating their values due to limited spatial resolution. In this study, combining field plot measurements and satellite imagery, a wall-to-wall forest biomass map were generated at a very high spatial resolution (5 m) over urban areas in Wuhan City, China. Specifically, a series of characteristic metrics were extracted from Jilin-1 satellite images, including multispectral reflectances, vegetation indices, and texture features. The estimations of forest aboveground biomass from three machine learning models were evaluated at sampled field plot level. Results demonstrated that the random forest model achieved the highest accuracy using the leave-one-out cross-validation method, with a test set RMSE of 31.84 Mg/ha. However, discrepancies were observed in low biomass areas due to variations in vegetation species, leading to overestimation of lower values.
通讯机构：
[Li, S ] C;Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat Hubei Prov, Wuhan 430079, Peoples R China.;Minist Agr & Rural Affairs, Key Lab Spect Sensing, Hangzhou 310058, Peoples R China.
关键词：
土壤碳;相似度;距离矩阵;连续统去除;偏最小二乘回归
摘要：
土壤中红外（MIR）光谱能快速、无污染、低成本地估算土壤有机碳等理化属性。随着各种尺度土壤光谱库的建立，使用其进行快速土壤分析引起广泛关注，但光谱库的通用模型在局部尺度上的预测效果不理想。开发“局部化”光谱建模方法是提高土壤光谱库性能的有效途径。本文提出了一种新的方法，通过光谱相似度计算和建模子集构建，旨在从库中快速建立最优局部建模集以提高预测精度。比较了欧氏、马氏、余弦三种距离算法衡量待测样本与库样本之间的相似度并生成距离矩阵；使用连续统去除法从距离矩阵中提取库容曲线中的特征点。利用偏最小二乘回归建立土壤MIR光谱与有机碳含量间的定量关系。结果表明，三种距离算法结合连续统去除得到的第一特征点均可得到较佳的预测精度。马氏距离不仅模型精度最高（R2 = 0.764，RMSE = 1.021%）而且用到的库样本数最少（14%库容）。本方法可改善MIR光谱分析的成本效率并能提高局部尺度的预测能力。 Soil mid-infrared (MIR) can provide a rapid, non-polluting, and cost-efficient method for estimating soil properties, such as soil organic carbon (SOC). Although there is a wide interest in using the soil spectral library (SSL) for soil analysis at various scales, the SSL with a general calibration often produces poor predictions at local scales. Therefore, developing methods to ‘localize’ the spectroscopic modelling is a reliable way to improve the use of SSL. In this study, we proposed a new approach that aims to rapidly build the optimal local model from the SSL by calculating the spectral similarity and developing the local calibration, in order to further improve the prediction accuracy. The distance matrix was constructed by three distance algorithms, namely Euclidean distance, Mahalanobis distance, and Cosine distance, which were compared and used to measure the similarity between the local samples and the SSL. The capacity curve, which was taken from the distance matrix, was used with a method called “continuum-removal” to find the feature points. Partial least-squares regression was used to build the spectroscopic models for SOC estimation. We found that for all three distance algorithms combined with the continuum-removal, the local calibration derived from the first feature point gave us a good idea of how accurate the prediction would be. The Mahalanobis distance can effectively develop the optimal local calibration from the MIR SSL, which not only achieved the best accuracy (R2 = 0.764, RMSE = 1.021%) but also used the least number of samples from SSL (14% SSL). On local scales, the approach we proposed can significantly improve both the analytical cost and the accuracy of the soil MIR technique.
作者机构：
[Yang, Meihua] Yuzhang Normal Univ, Dept Environm Engn, Nanchang 330103, Peoples R China.;[Chen, Songchao] Zhejiang Univ, ZJU Hangzhou Global Sci & Technol Innovat Ctr, Hangzhou 311215, Peoples R China.;[Hong, Yongsheng; Shi, Zhou; Chen, Songchao] Zhejiang Univ, Inst Appl Remote Sensing & Informat Technol, Coll Environm & Resource Sci, Hangzhou 310058, Peoples R China.;[Xu, Dongyun] Shandong Agr Univ, Coll Resources & Environm, Tai An 271000, Peoples R China.;[Li, Shuo] Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat, Wuhan 430079, Peoples R China.
通讯机构：
[Songchao Chen] Z;ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou 311215, China<&wdkj&>Institute of Applied Remote Sensing and Information Technology, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
作者机构：
[Li, Yong] Chinese Acad Sci, Inst Atmospher Phys, State Key Lab Atmospher Boundary Layer Phys & Atmo, Beijing 100029, Peoples R China.;[Liu, Ji; Li, Yong; Shen, Jianlin; Liu, Xinliang] Chinese Acad Sci, Inst Subtrop Agr, Key Lab Agro Ecol Proc Subtrop Reg, Changsha Res Stn Agr & Environm Monitoring, Changsha 410125, Peoples R China.;[Li, Yong] Univ Melbourne, Fac Vet & Agr Sci, Parkville, Vic 3010, Australia.;[Wang, Yi] Ludong Univ, Coll Resources & Environm Engn, Yantai 264025, Peoples R China.;[Liu, Ji] Cent China Normal Univ, Hubei Prov Key Lab Geog Proc Anal & Simulat, Wuhan 430079, Peoples R China.
通讯机构：
[Yong Li] F;Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, VIC 3010, Australia<&wdkj&>Key Laboratory of Agro-Ecological Processes in Subtropical Regions and Changsha Research Station for Agricultural & Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China<&wdkj&>State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China<&wdkj&>Author to whom correspondence should be addressed.
关键词：
N and P loadings;soil elemental stoichiometry;agricultural catchments;subtropics;water quality controls
摘要：
The control of nitrogen (N) and phosphorus (P) loadings to receiving waters is often overcompensated for by catchment planners. The objectives of this study, which investigated nine catchments in the subtropics of China, were to (i) quantify the explicit relationships between the N and P loadings to receiving waters and the topographic, soil and landscape characteristics of catchments, (ii) identify key impact factors and (iii) identify the most influential N and P loading pathways via catchments. Our collective data indicated that elevation-relief ratio, soil elemental stoichiometry and landscape structure determined the N and P loadings of the studied agricultural catchments. The N export from catchments characterized by a woodland backdrop (Masson pine) mosaic with the intrusion of paddy fields in the subtropics was postulated to be driven by two simultaneous processes: discharge and retention. In addition, a soil C:P threshold ratio for the catchment N and P loadings was estimated to be in the range of 107-117. Our PLS-SEM path analyses suggested that to reduce the N export from agricultural catchments in the subtropics, mitigation practices in landscape ecosystems (e.g., landscape patterns, ditches and streams) need to be taken into consideration and predominantly deployed, despite traditional measures used for soils. Strategies to lower the catchment P export can be directly proposed at the source site. Our findings provide greater insights into the transport and retention of N and P nutrients through catchments and may optimally direct the focus of catchment planners, thus increasing the control efficacy of catchment N and P losses.
