作者机构：
[Liu, Weihang; Sun, Ran; Li, Yan; Chen, Shuo; Li, Zitong; Ye, Tao; Liu, Yiqing] Beijing Normal Univ, State Key Lab Earth Surface Proc & Resource Ecol E, Beijing, Peoples R China.;[Liu, Weihang; Sun, Ran; Chen, Shuo; Li, Zitong; Ye, Tao; Liu, Yiqing] Beijing Normal Univ, Key Lab Environm Change & Nat Disasters, Minist Educ, Beijing, Peoples R China.;[Liu, Weihang; Sun, Ran; Chen, Shuo; Li, Zitong; Ye, Tao; Liu, Yiqing] Minist Educ, Minist Emergency Management, Acad Disaster Reduct & Emergency Management, Beijing, Peoples R China.;[Liu, Weihang; Sun, Ran; Chen, Shuo; Li, Zitong; Ye, Tao; Liu, Yiqing] Beijing Normal Univ, Fac Geog Sci, Beijing, Peoples R China.;[Li, Yan] Beijing Normal Univ, Inst Land Surface Syst & Sustainable Dev, Fac Geog Sci, Beijing, Peoples R China.
通讯机构：
[Ye, T ] B;Beijing Normal Univ, State Key Lab Earth Surface Proc & Resource Ecol E, Beijing, Peoples R China.;Beijing Normal Univ, Key Lab Environm Change & Nat Disasters, Minist Educ, Beijing, Peoples R China.;Minist Educ, Minist Emergency Management, Acad Disaster Reduct & Emergency Management, Beijing, Peoples R China.;Beijing Normal Univ, Fac Geog Sci, Beijing, Peoples R China.
摘要：
Understanding how crop phenology responds to climate change is critical for enabling agricultural adaptation measures. Pre-season temperature alone leads to well-understood changes in crop phenology. Nevertheless, the modulation effect of concurrent precipitation extremes on the response to temperature extremes has been largely under-addressed. Here, we investigate the response of rice transplanting dates to pre-season temperature extremes and reveal the modulation effects of concurrent precipitation extremes by using station-observed rice transplanting dates from 1981 to 2018 across mainland China. We also evaluate the performance of a remotely sensed phenology product, ChinaCropPhen1km, in reproducing the above temperature responses and modulation effects. Our results showed that transplanting dates tended to advance in response to an extremely hot pre-season, while concurrent extreme drought offset the advance by up to 2.6 days. Transplanting dates tended to be delayed in response to an extremely cold pre-season, while concurrent extreme precipitation exacerbated the delay by up to 1 day. Responses to temperature extremes and modulation effects were divergent across different regions. Under extremely hot conditions, transplanting dates advanced further in hotter and wetter regions, while under extremely cold pre-seasons, transplanting dates delayed less in colder and drier regions. Transplanting dates from the ChinaCropPhen1km product underestimated the responses to temperature extremes by up to 4.7 days and detected the opposite modulation effect compared to those obtained from observations. Our results highlight that the need to improve our understanding and modeling of modulation effects of precipitation extremes on temperature–phenology relationship, which benefits the field of agriculture risk analysis and climate change adaptation.
Concurrent extreme drought offset the extreme hot induced-advance, and extreme precipitation exacerbate the extreme cold induced-delay
Responses to temperature extremes and modulation effects of precipitation extremes are divergent across regions
Remotely sensed transplanting dates from ChinaCropPhen1km underestimate the responses to temperature extremes and modulation effects
Frequent climate extremes are projected with ongoing climate change. This paper reveals the effect of concurrent precipitation extremes in modulating rice transplanting date response to pre-season temperature extremes in China and assesses remotely sensed transplanting dates from the ChinaCropPhen1km product in reproducing the above temperature responses and modulation effects. Results show that concurrent precipitation extremes substantially influence the temperature–transplanting date relationship. Two kinds of modulation effects are detected: (a) concurrent extreme precipitation tends to exacerbate the extremely cold-induced delay by up to 1 day, and (b) concurrent extreme drought conditions tend to offset the extremely hot-induced advance by up to 2.6 days. From a spatial perspective, responses to temperature extremes and modulation effects are divergent across regions. Additionally, remotely sensed transplanting dates from the ChinaCropPhen1km product underestimate the temperature responses and detect the opposite modulation effects compared to observations. This study highlights the critical role of concurrent precipitation extremes in modulating temperature impact on crop phenology, which requires more understanding and modeling in future analysis.
作者：
Wu, Tieniu;Cheng, Antai;Lin, Henry;Zhang, Hailin;Jie, Yi
期刊：
地球科学学刊,2023年34(5):1556-1566 ISSN：1674-487X
通讯作者：
Wu, TN
作者机构：
[Cheng, Antai; Wu, Tieniu; Jie, Yi; Zhang, Hailin] Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat, Wuhan 430079, Hubei Province, Peoples R China.;[Lin, Henry; Wu, Tieniu] Penn State Univ, Dept Ecosyst Sci & Management, University Pk, PA 16802 USA.;[Cheng, Antai; Wu, Tieniu; Jie, Yi; Zhang, Hailin] Cent China Normal Univ, Coll Urban & Environm Sci, Wuhan 430079, Peoples R China.
通讯机构：
[Wu, TN ] C;Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat, Wuhan 430079, Hubei Province, Peoples R China.;Penn State Univ, Dept Ecosyst Sci & Management, University Pk, PA 16802 USA.;Cent China Normal Univ, Coll Urban & Environm Sci, Wuhan 430079, Peoples R China.
关键词：
MIS 9;climatic fluctuation;Paleosol;S3;Chinese Loess Plateau;environmental geology
摘要：
Marine Isotope Stages (MIS) 9 has been proposed as an analog for the present warm period. However, detailed studies of this geological time period are rare in loess-paleosol sequence. In the Chinese Loess Plateau (CLP), the corresponding stratum is the third paleosol layer (S3). Here, we report the terrestrial reconstruction of climatic fluctuations during MIS 9 by analyzing the paleo-climate indexes of S3 with high sampling density. Our results showed that: (1) During the period of MIS 9, the main climatic sub-cycle was 29 ka; (2) MIS 9 could be divided into five sections, MIS 9a, 9b, 9c, 9d, and 9e. Among them, MIS 9a, 9c, and 9e were warm stages, while MIS 9b and 9d were cool intervals; and 3) There were also three swift warm-wet events and one cool-dry event, which occurred around 332-331, 324-323, 311-310, and 331-329 ka BP, respectively. The overall trend of paleo-climate fluctuation correlated approximately with SPECMAP, LR04 stack and Iberian margin deep-sea cores. This study suggested that the paleosol records in the southern margin of the CLP have global significance and contain more detailed climatic signals than marine deposits.
作者机构：
[Tang, Hui; Ao, Rongjun; Zhou, Xiaoqi; Aihemaitijiang, Yierfanjiang; Chen, Jing] Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat Hubei Prov, Wuhan, Hubei, Peoples R China.;[Tang, Hui; Ao, Rongjun; Zhou, Xiaoqi; Aihemaitijiang, Yierfanjiang; Chen, Jing] Cent China Normal Univ, Coll Urban & Environm Sci, Wuhan, Hubei, Peoples R China.;[Tang, Hui] Hunan City Univ, Sch Architecture & Urban Planning, Yiyang, Hunan, Peoples R China.
通讯机构：
[Aihemaitijiang, Y ] C;Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat Hubei Prov, Wuhan, Hubei, Peoples R China.;Cent China Normal Univ, Coll Urban & Environm Sci, Wuhan, Hubei, Peoples R China.
摘要：
High-quality regional development should be promoted by facilitating inter-regional mobility of heterogeneous labor force to optimize its spatial allocation. This study incorporates skill relatedness into spatial categorization and selection effects, and explores how skill-relatedness affects the location choice of heterogeneous labor force. To do so, we use labor force migration data and employee data by occupation subcategory from the 2000 National Population Census and 2015 National Population Sample Survey. The empirical evidence provides three major findings. First, there are significant regional differences in labor migration rates by the occupational group between cities in China, and the trend is increasing. Regional concentration of location choice is increasing and six significant agglomerations are formed. Second, skill relatedness positively affects the location choice of the heterogeneous labor force in Chinese cities. When cities' skill-relatedness is more robust, influence on labor location choice is more remarkable. In cities with high-size classes, the effect of high-skill relatedness on labor location choice is higher. Third, labor force with solid skill relatedness with regional employment moves to the location owing to the spatial sorting effect. Labor force without skill relatedness or weak relatedness moves out or does not move to the location owing to the spatial selection effect.
摘要：
Extracting crop phenophases from satellite remote sensing data is crucial for managing agricultural activities and estimating crop yield over large scales. The traditional Vegetation Indices (VIs), such as the Enhanced Vegetation Index (EVI) and Normalized Difference Vegetation Index (NDVI), primarily indicate changes in vegetation greenness, which characterize crop phenophases well in vegetative growth period but may be difficult to associate with phenophases in reproductive growth period that are more related with physiology status. In this study, we investigated the potential of the satellite Solar-Induced chlorophyll Fluorescence (SIF) on extracting the crop phenophases in reproductive growth period, i.e., milk-ripe phase and maturity phase, using single-season cropland in mid-temperate zone in China as a test bed. We found that SIF outperformed EVI and NDVI in extracting milk-ripe phase and maturity phase of maize, rice and wheat using double logistic method. In particular, SIF-derived maturity phase were closer to field-observed phenophases (Mean Bias = 0.73 days) with higher R2 (0.87) than that from EVI and NDVI. At a regional scale, the milk-ripe phase and maturity phase were observed from August to mid-September, and from mid-September to mid-October, respectively, which varied with crop types and in spatial distribution. Out of all crops in mid-temperate zone in China, 65% experienced a delay in the milk-ripe phase, whereas 77% exhibited a delay in the maturity phase from 2001 to 2019. In addition to the adjustment of human managements under climate warming, we further found that crop phenophases in reproductive growth period exhibited the strongest correlation with preseason water-related environmental variables, particularly vapor pressure deficit and total precipitation. This work highlighted the potential of satellite SIF in identifying the crop-specific milk-ripe and maturity phases, and improving our understanding for spatio-temporal variations of crop phenophases in reproductive growth period as well as their responses to preseason environmental variables, which will in turn promote SIF applications in agriculture.
期刊：
ISPRS Journal of Photogrammetry and Remote Sensing,2023年205:34-49 ISSN：0924-2716
通讯作者：
Hu, Q
作者机构：
[Xu, Baodong; Shi, Zhihua; Cai, Zhiwen] Huazhong Agr Univ, Coll Resources & Environm, Wuhan 430070, Peoples R China.;[Hu, Q; Hu, Qiong; Yang, Jingya] Cent China Normal Univ, Coll Urban & Environm Sci, Hubei Prov Key Lab Geog Proc Anal & Simulat, Wuhan 430079, Hubei, Peoples R China.;[Zhang, Xinyu; You, Liangzhi; Wei, Haodong] Huazhong Agr Univ, Macro Agr Res Inst, Coll Plant Sci & Technol, Wuhan 430070, Peoples R China.;[Li, Wenjuan; Yang, Jingya] Chinese Acad Agr Sci, Inst Agr Resources & Reg Planning, State Key Lab Efficient Utilizat Arid & Semi arid, Beijing 100081, Peoples R China.;[Zeng, Yelu] China Agr Univ, Coll Land Sci & Technol, Beijing 100083, Peoples R China.
通讯机构：
[Hu, Q ] C;Cent China Normal Univ, Coll Urban & Environm Sci, Hubei Prov Key Lab Geog Proc Anal & Simulat, Wuhan 430079, Hubei, Peoples R China.
关键词：
Agricultural field parcel delineation Deep learning Multimodal satellite data Spatiotemporal fusion Spatial transferability
摘要：
Accurate spatial information for agricultural field parcels is important for agricultural production management and understanding agro-industrialization and intensification. However, traditional remote sensing methods that rely on single-modal or single-date data struggle to identify heterogeneous field parcels, particularly in regions dominated by smallholder farming systems. To address this challenge, we proposed a Dual branch Spatiotemporal Fusion Network (DSTFNet) that integrated very high-resolution (VHR) images and medium-resolution satellite image time series (MRSITS) to extract agricultural field parcels over various landscapes. The DSTFNet consisted of two branches: a spatial branch that extracted spatial features from VHR images and a temporal branch that explored seasonal spectral dynamics from MRSITS data by using ConvLSTM units and an attention module. We evaluated the DSTFNet in four regions across China by using GF-2 and Sentinel-2 data. The results showed that DSTFNet performed well in delineating agricultural field parcels, achieving the highest Matthew's correlation coefficient (MCC) = 0.823 for the field extent, the highest F1-score of edge (Fedge) = 0.865 for field boundary, and the lowest errors of segmentation evaluation index (SEI) = 0.191 for the vectorized field parcels in Hubei province. In addition, DSTFNet significantly outperformed two single-branch models that used VHR or MRSITS alone, as well as existing BsiNet, ResUNet_a, UNet and RAUNet models. DSTFNet also showed good spatial transferability in distinct regions without training data (on average, MCC = 0.728, Fedge = 0.729, and SEI = 0.281 for three target regions). Using limited training data to fine-tune the DSTFNet can further improve its ability to delineate field parcels over complex regions. The visualization analysis of temporal attention weights demonstrated that DSTFNet can well capture cropland spectral dynamics, making it advantageous in extracting diverse cropland parcels. By exploiting important spectral, spatial and temporal information from multimodal satellite data, DSTFNet provided an effective, robust, and transferable solution for accurately delineating agricultural field parcels across heterogeneous farming systems.
作者机构：
[Tao, Jianbin; Zhou, Yang; Zhang, Xinyue; Jiang, Qiyue; Zhou, Y] Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat Hubei Prov, Sch Urban & Environm Sci, Wuhan 430079, Peoples R China.;[Liu, Yiqing] Beijing Normal Univ, Inst Disaster Risk Sci, Fac Geog Sci, Beijing 100875, Peoples R China.
通讯机构：
[Zhou, Y ] C;Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat Hubei Prov, Sch Urban & Environm Sci, Wuhan 430079, Peoples R China.
关键词：
cropping intensity;temporal mixture analysis;endmember;unmixing;time series images
摘要：
Agricultural cropping intensity plays an important role in evaluating the food security and the sustainable development of agriculture. The existing indicators measuring cropping intensity include cropping frequency and multiple cropping index. As a nominal measurement, cropping frequency classifies crop patterns into single-cropping and/or double-cropping and leads to information loss. Multiple cropping index is calculated on the basis of statistical data, ignoring the spatial heterogeneity within the administrative region. Neither of these indicators can meet the requirements of precision agriculture, and new methods for fine cropping intensity mapping are still lacking. Time series remote sensing data provide vegetation phenology information and reveal temporal development of vegetation, which can be used to facilitate the fine cropping intensity mapping. In this study, a new temporal mixture analysis method is introduced to estimate the abundance level cropping intensity from time series remote sensing data. By analyzing phenological characteristics of major land-cover types in time series vegetatiosacan indices, a novel feature space was constructed by using the selected PCA components, and three unique endmembers (double-cropping, natural vegetations and water bodies) were found. Then, a linear spectral mixture analysis model was applied to decompose mixed pixels by replacing spectral data with multi-temporal data. The spatio-temporal continuous, fine resolution, abundance level cropping intensity maps were produced for the North China Plain and the middle and lower reaches of the Yangtze River Valley. The experiments indicate a good result at both county and pixel level validation. The method of manually delineating endmembers can well balance the accuracy and efficiency. We also found the size of the study area has little effect on the unmixing accuracy. The results demonstrated that the proposed method can model cropping intensity finely at large scale and long temporal span, at the same time with high efficiency and ease of implementation.
作者机构：
[Chen, Wei; Li, Siliang; Jiang, Bohan] Tianjin Univ, Inst Surface Earth Syst Sci, Sch Earth Syst Sci, Tianjin 300072, Peoples R China.;[Chen, Wei; Li, Siliang; Jiang, Bohan] Haihe Lab Sustainable Chem Transformat, Tianjin 300192, Peoples R China.;[Chen, Wei; Li, Siliang; Jiang, Bohan] Tianjin Bohai Rim Coastal Earth Crit Zone Natl Obs, Tianjin 300072, Peoples R China.;[Dai, Xiaoai] Chengdu Univ Technol, Coll Earth Sci, Chengdu 610059, Peoples R China.;[Xu, Min] Chinese Acad Sci, Aerosp Informat Res Inst, State Key Lab Remote Sensing Sci, Beijing 100101, Peoples R China.
通讯机构：
[Wei Chen] I;[Xiaoai Dai] C;College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China<&wdkj&>Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China<&wdkj&>Haihe Laboratory of Sustainable Chemical Transformation, Tianjin 300192, China<&wdkj&>Tianjin Bohai Rim Coastal Earth Critical Zone National Observation and Research Station, Tianjin 300072, China
作者机构：
[Liu, Ji; Liu, Muxing; Zhang, Hailin; Yi, Jun] Key Lab Geog Proc Anal & Simulat, Wuhan 430079, Hubei, Peoples R China.;[Liu, Ji; Wang, Qiuyue; Liu, Muxing; Zhang, Hailin; Yi, Jun] Cent China Normal Univ, Coll Urban & Environm Sci, Wuhan 430079, Peoples R China.;[Hu, Wei] New Zealand Inst Plant & Food Res Ltd, Private Bag 4704, Christchurch 8140, New Zealand.
通讯机构：
[Jun Yi] K;Key Laboratory for Geographical Process Analysis & Simulation, Hubei Province, Wuhan, 430079, China<&wdkj&>College of Urban and Environmental Sciences, Central China Normal University, Wuhan, 430079, China
关键词：
Volumetric soil water content;Wavelet analysis;Significant coherence area;Time scale;Vegetation type;Slope position
摘要：
Clarifying the mechanisms governing volumetric soil water content (VSWC) dynamics in soil profiles is essential, as it can help to elucidate soil water transport processes and improve the prediction accuracy of soil hydrological processes. Using Spearman's rank correlation and wavelet coherence analysis methods, similarity in soil profile VSWC dynamics and factors governing VSWC soil profile dynamics in upslopes and downslopes under three vegetation types (evergreen forest [EG], secondary deciduous forest mixed with shrubs [SDFS], and deforested pasture [DP]) at different time scales (hourly, daily, weekly, and monthly) and in different seasons were analyzed. The results revealed significant similarity in the VSWC of different soil depths (P < 0.01), with the similarity decreasing in accordance with the increment in soil depth. Greater VSWC similarity was found in EG than SDFS and DP sites and in upslope than downslope areas at both forest sites. The average significant coherence area (SCA) of VSWC similarity among surface and deep soil layers varied with the time scale, which was in the order of monthly (58.6%) > weekly (42.8%) > daily (21.8%). The effects of soil properties (e.g., texture, saturated hydraulic conductivity), rainfall, and potential evapotranspiration (ETp) on VSWC similarity were related to the time scale and season in which VSWC monitoring took place. Soil properties had apparent effects on VSWC similarity at longer time scales (i.e., monthly), with a high SCA. In contrast, the effects of rainfall and ETp on VSWC similarity were concentrated at weekly and daily scales, with a relatively low SCA. Rainfall and ETp dominated VSWC dynamics in the summer and fall, respectively. These results imply the use of measured VSWC at one soil depth to predict the VSWC at other soil depths was a reliable method. While the in-fluence of time scale effects and seasonal variations on prediction accuracy of VSWC should be considered. ](c) 2022 International Research and Training Center on Erosion and Sedimentation, China Water and Power Press, and China Institute of Water Resources and Hydropower Research. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY -NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
期刊：
International Journal of Environmental Research and Public Health,2023年20(2):1629- ISSN：1661-7827
通讯作者：
Yujie Liu<&wdkj&>Qing Wu
作者机构：
[Li, Xigui] Hunan Agr Univ, Coll Landscape Architecture & Art Design, Changsha 410128, Peoples R China.;[Wu, Qing] Zhaoqing Univ, Tourism & Hist Culture Coll, Zhaoqing 526061, Peoples R China.;[Wu, Qing] Nanjing Normal Univ, Sch Geog, Nanjing 210023, Peoples R China.;[Liu, Yujie] Cent China Normal Univ, Coll Urban & Environm Sci, Wuhan 430079, Peoples R China.
通讯机构：
[Yujie Liu] T;[Qing Wu] A;The College of Urban & Environmental Sciences, Central China Normal University, Wuhan 430079, China<&wdkj&>Authors to whom correspondence should be addressed.<&wdkj&>Authors to whom correspondence should be addressed.<&wdkj&>School of Geography, Nanjing Normal University, Nanjing 210023, China<&wdkj&>Tourism and Historical Culture College, Zhaoqing University, Zhaoqing 526061, China
关键词：
cultivated land system health;PSR-VOR model;zoning regulation;two lake plains
摘要：
Cultivated land resources are the material basis of sustainable agricultural development. Climate change, food security, land pollution, and other issues highlight the value of sustainable agricultural development, and the health of the cultivated land system has attracted much attention. By constructing "PSR-VOR" cultivated land system health evaluation framework under the 5 km grid scale and using GIS spatial analysis and mathematical statistics to comprehensively evaluate the health status of the cultivated land system in the two lake plains from 2000 to 2019. The major results have shown that: (1) Over the past 20 years, both the highest and average values of the health index of the cultivated land system have gone down, and the health status of the cultivated land system has changed and gotten worse over time. (2) The health status in the two lake plains has been generally good, mainly in Class I and Class II areas. However, the area of cultivated land with general and poor health status has increased rapidly. On the whole, the health level presents the characteristic of gradually decreasing from the northeast to the southwest and southeast. (3) During the study period, the global Moran's I value of the cultivated land system health index in the two lake plains increased from 0.686 to 0.729, with significant spatial positive autocorrelation, and the spatial heterogeneity of the cultivated land system health index gradually increased. As shown by the spatial distribution characteristics of high in the north, low in the south, and decreasing from the middle to the outside, the distribution of the high-value cluster area and the low-value cluster area of the cultivated land system health index in the two lake plains has not changed significantly over the past 20 years. (4) The two lake plains are divided into five areas: a moderate optimization area, a collaborative optimization area, a potential improvement area, a key improvement area, and a priority improvement area. The urgency of regulating the health status from the moderate optimization area to the priority improvement area has gradually increased, and the differentiated utilization and management of cultivated land resources need to be carried out according to local conditions.
作者：
Nie, Hanjiang;Shen, Zhenqian;Qin, Tianling;Gong, Xinfeng;Huang, Yinghou
期刊：
TECNOLOGIA Y CIENCIAS DEL AGUA,2023年14(2):376-418 ISSN：0187-8336
作者机构：
[Nie, Hanjiang; Qin, Tianling] China Inst Water Resources & Hydropower Res, State Key Lab Simulat & Regulat Water Cycle River, Beijing, Peoples R China.;[Nie, Hanjiang] Cent China Normal Univ, Sch Urban & Environm Sci, Key Lab Geog Proc Anal & Simulat Hubei Prov, Wuhan, Peoples R China.;[Shen, Zhenqian] Guangzhou Water Sci Res Inst, Guangzhou, Peoples R China.;[Gong, Xinfeng] Zhengzhou Univ, Coll Water Conservancy Engn, Zhengzhou, Peoples R China.;[Huang, Yinghou] Hohai Univ, Coll Hydrol & Water Resources, Nanjing, Jiangsu, Peoples R China.
关键词：
Trend and significance;abrupt change;spatiotemporal analysis;high resolution
摘要：
The natural hydrologic cycle is greatly influenced by climate change. In particular, substantial spatiotemporal variations in precipitation can occur in some mountainous areas, and thus it is very important to identify hydrological processes in watershed with high resolution. To analyze the problem above, the Mann-Kendall test, the moving T-test, Sen's slope estimator and Spearman rank correlation test combined with the spatial interpolation function of ArcGIS, are used to analyze and discuss the evolution of the spatiotemporal distribution characteristics of precipitation and Runoff in a typical small watershed of mountainous areas. The result is precipitation showed a downward trend from south to north and from high-altitude to low-altitude regions. And the difference mainly occurred in the western part of the basin. And the conclusions show the following: 1) An abrupt change in both precipitation and Runoff sequences occurred in 1991; 2) the extreme value of the precipitation trend shifted from the central region to the western region; 3) for the ratio of Runoff in the flood season to annual Runoff, the sequence showed a significant upward trend (95 % confidence level), indicating that the uneven distribution of Runoff has significantly increased since the 1960s.
