摘要：
Land cover mapping is crucial for natural resource assessment, urban planning, and sustainable development. Land cover nomenclature often includes two or three hierarchical levels with tree-like hierarchical structures. This study aims to explore these hierarchical relationships and the potential of hierarchical semantic segmentation for land cover mapping. We propose a hierarchical semantic segmentation architecture by taking advantage of dual U-shaped network, named as HierU-Net. The coarse-level result is ingested to the fine-level segmentation functioned as soft constraints. The propagation of error will not be certain. Moreover, we employ a multitask loss function weighted by homoscedastic uncertainty to optimize the training. To evaluate the performance of the proposed method, we create a hierarchical semantic segmentation dataset (HierToulouse), which contains 11 528 samples, including images and land cover labels at two hierarchical levels. The experiments demonstrate that the proposed approach is capable of achieving accurate land cover segmentation at both coarse and fine levels, with segmentation results surpassing those obtained using the flat method.
摘要：
Logistics services are integral to urban economic activity, and delving into the spatial distribution traits and evolutionary pathways of various kinds of logistics service node facilities (LSNF) is markedly valuable for understanding a city’s functional spatial makeup and refining the spatial layout of logistics services. This study quantitatively and qualitatively analyzes the spatial congregation and spreading characteristics of diverse LSNFs in Wuhan in 2011, 2014, 2017, and 2020, employing kernel density analysis, average nearest neighbor index, mean center, and distance distribution frequency, seeking to characterize the spatial evolution characteristics of LSNF, alongside examining the trends in distances to city cores, principal adjoining roads, and production and consumption sites. The following conclusions were made: (1) Between 2011 and 2020, various types of LSNFs in Wuhan experienced a pattern characterized by the noticeable coexistence of spatial expansion and agglomeration, particularly visible after 2014. The degree of agglomeration is classified in a descending order as follows: CWC, STN, PSN, and PDN. (2) An “absolute diffusion” phenomenon characterizes the distribution of distances between various kinds of LSNFs and city cores or neighboring roads, with the lion’s share of high-frequency distribution zones spreading beyond city cores by 5–10 km, and a majority of the LSNFs being situated within 1 km from adjacent roads. (3) While the LSNF collective exhibits a stronger tendency towards the consumption facet, it reflects a surrounding of industrial production sites on the production facet and locations of manufactured goods consumption on the consumption facet, followed by locations of agricultural product consumption and comprehensive consumption sites.
摘要：
The rice -crayfish field (i.e., RCF), a recently emerged rice cultivation pattern, has experienced remarkable growth in China over the last decade due to its significant socioeconomic advantages. However, the impacts of expanding RCF areas on the regional -scale ecological environment, particularly concerning methane (CH4) emissions, remain unclear. A major obstacle in addressing this knowledge gap is the absence of accurate and upto-date spatial distribution information on RCF across years. Here, we selected Jianghan Plain which has the largest RCF area in China as the study area. First, we developed a phenology-based identification algorithm using Landsat-7/8 satellite data, which considered the distinctive flooding signatures of RCF during the rice fallow periods, to identify RCF at the regional scale. Second, we employed the DeNitrification-DeComposition (DNDC) model to simulate the CH4 fluxes of various rice cropping systems, including RCF, rice monoculture (RM), ricerapeseed rotation (RR), and rice -wheat rotation (RW). Finally, the effects of RCF expansion during 2014-2019 on regional CH4 emissions were analyzed by comparing six scenarios that simulated the conversion of different rice cropping systems to RCF. Results showed the phenology-based algorithm performed well in extracting RCFs, achieving an overall accuracy >92 % for all years based on 1025 RCF and 2096 non-RCF validation samples. RCF generated the least CH4 flux, followed by RM, RR, and RW. Moreover, shifting from traditional rice cropping systems to RCF reduced CH4 emissions across all cases, with mitigation rates ranging from 4.82 % to 21.85 %, indicating RCF's substantial CH4 mitigation potential. These findings significantly improve our understanding of the ecological effects of RCF cultivation, which is critical for advancing land use planning and decision -making for sustainable agricultural development in China. Our presented evaluation method of integrating the remote sensing mapping algorithm and DNDC model can be easily generalized for other crop types in other regions.
摘要：
Infiltration is the process of water entering into, and routings through, the subsurface. It has a profound impact on hillslope and catchment runoff. However, because of the hidden and complex subsurface structures, our understanding of rainfall-related infiltration and how it partitions along a topographic gradient remains challenging. In this study, we used two years of field observations of volumetric soil moisture at 25 combinations of topographic positions and soil depths along a steep subtropical forested hillslope. The lateral partition patterns of infiltration and its control factors were investigated based on a new index, percentage of soil water storage increment at each site to all hillslope sites during a rainfall event (PWSI). Our results showed that the active soil layer involved in hillslope lateral flow was distributed within the depths of 10–40 cm. In deep soil depths (i.e., 40–80 cm), lateral flow was more evident under wet initial moisture conditions than under dry initial moisture conditions, whereas rainfall characteristics had a relatively weak effect on it. Unexpectedly, we found the variability of infiltration partitioning remained high in the deeper soil layers. Among the soil properties, sand, bulk density, n, KS, and SOM were conducive to infiltration, whereas clay had the opposite effect. The dominant factors controlling the lateral partition patterns of infiltration across soil depths were sand in the depths of 0–10 cm, topographic gradient in depths of 10–40 cm, and n (parameter of soil retention curve) in the depths of 40–80 cm. Findings of this study reveal the infiltration partitioning indices were useful to quantitatively describe the distribution patterns of infiltration after rainfall events at the hillslope, and provide new insights into the detection of hillslope lateral flow, which is valuable for understanding subsurface hydrological processes and improving water resource management in humid mountain ecosystems.
摘要：
Maritime transportation plays a crucial role in global trade and economic development. However, this industry is exposed to various risks (e.g., natural disasters), which can cause significant economic and environmental damage. This study aims to develop a spatial risk assessment approach for maritime transportation using machine learning and geospatial big data to identify potential risks in China's maritime transportation industry. The proposed approach first produces risk maps that reveal significant variability in maritime transportation risks across different regions of China. Then, factor importance analysis identifies wave height, rainfall, and sea surface temperature as the most influential factors affecting navigational safety. Finally, capability indicators are employed to analyze the matching relationship between coastal search and rescue resources and maritime transportation risks. Our study provides valuable references for enhancing maritime emergency response capabilities and protecting marine ecological environments.
摘要：
The United Nations has proposed Sustainable Development Goals (SDGs), of which SDG11 aims to "make cities and human settlements inclusive, safe, resilient and sustainable". This is in line with Urban Vitality's objectives. This study proposes a quantitative framework to evaluate the impact of urban morphology on urban vitality. In this framework, a proxy that is more reflective of economic and human activities is proposed for depicting urban vitality based on geographic big data; then we use a Multi-scale Geographically Weighted Regression (MGWR) regression considering spatial heterogeneity to analyze the different effects of urban form on urban vitality. Taking the Beijing Sixth Ring Road area as the study region, the results indicate that tall, large-area, multi-functional buildings have a significantly positive impact on urban vitality. These areas exhibit single-function buildings and high levels of greenery, leading to inefficient space utilization. Increasing road network density, as well as the density of transportation and public facilities, also positively influences urban vitality. However, commercial density has a negative impact on workday vitality. Furthermore, excessive green space density, a high proportion of the largest green patches, and complex green space borders all contribute to a reduction in urban vitality.
摘要：
Revegetation is effective in improving soil quality in ecologically fragile areas. However, little is known about the impact of diverse phytomanagement strategies of tailings on soil quality and ecological security in erosion-prone areas. We investigated the water stability, soil aggregate nutrients, and the risk of heavy metal contamination of abandoned tailings under phytomanagement and in adjacent bare land on the Loess Plateau. The results showed that phytomanagement significantly enhanced soil aggregate stability, as demonstrated by higher contents of soil organic carbon (SOC), glomalin-related soil protein (GRSP), aromatic-C, and alkene-C in macro-aggregates. The pollution load index (PLI) and ecological risk index (RI) of soil heavy metals were lower in shrub/herbaceous mixed forests than in natural grasslands and planted forests. The risk of heavy metal contamination was higher in macro-aggregates (>0.25 mm) than in micro-aggregates (<0.25 mm) and was significantly and positively correlated with the SOC and GRSP contents of the aggregates. Our study demonstrates that soil aggregate quality is closely related to the fate of heavy metals. Diversified tailing revegetation measures can improve soil quality and ensure ecological security.
关键词：
Biochar leachate;Nitrate assimilation;Nitrogen fixation;Nitrogen-fixing cyanobacteria;Photosynthetic system
摘要：
Biochar contains biotoxic aromatic compounds, and their influence on nitrogen-fixing cyanobacteria, the critical nitrogen fixer in paddy soil, has never been tested. Here, the physiological, metabolomic, and transcriptomic analyses of Nostoc sp. PCC7120 in response to biochar leachate were performed. The results suggested that biochar leachate inhibited the efficiency of photosynthesis, nitrogen fixation, and nitrate assimilation activities of nitrogen-fixing cyanobacteria. Biochar leachate containing aromatic compounds and odd- and long-chain saturated fatty acids impaired the membrane structure and antenna pigments, damaged the D1 protein of the oxygen evolution complex, and eventually decreased the electron transfer chain activity of photosystem II. Moreover, the nitrogen fixation and nitrate assimilation abilities of nitrogen-fixing cyanobacteria were inhibited by a decrease in photosynthetic productivity. A decrease in iron absorption was another factor limiting nitrogen fixation efficiency. Our study highlights that biochar with relatively high contents of dissolved organic matter poses a risk to primary nitrogen assimilation reduction and ecosystem nitrogen loss. Further evidence of the potential negative effects of biochar leachates on the fixation and assimilation capacity of nitrogen by soil microbes is needed to evaluate the impact of biochar on soil multifunctionality prior to large-scale application.
通讯机构：
[Zhang, XS ] C;Cent China Normal Univ, Coll Urban & Environm Sci, Wuhan, Peoples R China.;Hubei Prov Key Lab Geog Proc Anal & Simulat, Wuhan, Peoples R China.
关键词：
ecosystem service trade-off/synergy;InVEST model;GeoSOS-FLUS model;multiscenario simulation;Jianghan Plain of China
摘要：
Disturbance from human activities has intensified the evolution of ecosystem structure in the Jianghan Plain of China, leading to intensified conflicts between ecosystem services. It is essential to clarify the trade-off synergies between ecosystem services in the Jianghan Plain of China to better coordinate the economic and social development and ecological protection of the region. Based on historical data and scenario predictions using the GeoSOS-FLUS model, the InVEST model was applied to five key ecosystem services: Carbon storage, crop production, habitat quality, soil conservation and water yield from 2000 to 2020. Spearman correlation analysis was used to explore the trade-off synergies between different ecosystem services in space and time. The results showed that arable land and water land areas are the most important land types in the Jianghan Plain of China. From 2000 to 2020, the increase in build-up land and water land areas was accompanied by a decrease in arable land, forest land and unused land, and an increase in forest land. The natural development scenario in 2035 continues this trend except forest land reduction, while the ecological protection scenario reverses this trend. From 2000 to 2020, crop production, water yield, and soil conservation increased in the Jianghan Plain of China, while carbon storage and habitat quality declined significantly, showing a spatial distribution pattern of higher in the northwest and lower in the southeast. The comprehensive ecosystem services simulated in 2035 showed a downward trend compared with 2020, and the ecological protection scenario has the smallest decrease. There is an overall synergistic relationship between the five ecosystem services in the Jianghan Plain of China, and the strongest synergistic relationship is between soil conservation and water yield. The spatiotemporal relationship between the ecosystems in the Jianghan Plain of China is dynamic and requires sustainable management. Thus, it is necessary to rationally utilize land resources and enhance the ecological functions of the area to minimize trade-offs based on scientific land and spatial planning to maximize synergy.
期刊：
Journal of Soils and Sediments,2024年24(1):1-16 ISSN：1439-0108
通讯作者：
Liu, Muxing;Yi, J
作者机构：
[Yi, Jun; Lu, Shiguo; Liu, Muxing; Zhang, Hailin; Liu, MX; Wang, Weijie] Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat Hubei Prov, Wuhan 430079, Peoples R China.;[Yi, Jun; Lu, Shiguo; Liu, Muxing; Zhang, Hailin; Liu, MX; Wang, Weijie] Cent China Normal Univ, Coll Urban & Environm Sci, Wuhan 430079, Peoples R China.;[Wan, Jinhong] Inst Water Resources & Hydropower Res, Beijing 100048, Peoples R China.
通讯机构：
[Yi, J ; Liu, MX] C;Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat Hubei Prov, Wuhan 430079, Peoples R China.;Cent China Normal Univ, Coll Urban & Environm Sci, Wuhan 430079, Peoples R China.
关键词：
Soil infiltration response;Forest conversion;Hillslope hydrology;Humid area
摘要：
PurposeUnderstanding the characteristics of soil infiltration response to rainfall is critical for soil water transport processes and hydrologic modeling. However, little is known about how they vary with forest conversion at different temporal stages (< 20 years) below the rooting zone. Therefore, this study aims to investigate soil infiltration response patterns in different subtropical forest conversion hillslopes, including mature original forest (thick root), young secondary forest (middle root), and very young secondary grassland (fine root), and analyzed the effects of environmental factors on the dynamics of soil infiltration.Materials and methodsSeveral metrics were evaluated to characterize and quantify the nature of these responses by estimating changes in the soil water content, the response time difference between two adjacent soil depths, and infiltration velocities for 1144 infiltration events at 6 locations on the three hillslopes.Results and discussionSoil infiltration responses were similar on both forestland hillslopes, yet significantly different from those on the grassland hillslope. The preferential flow was more evident in the profile of thick-rooted vegetation, and the velocity of the wetting front was faster in the profiles of middle- and fine-rooted vegetation. Topography and root characteristics interact to influence soil infiltration response at the hillslope scale.ConclusionsConversion from thick-rooted forests into fine-rooted grasslands altered the rainfall-related soil infiltration dynamics below the rooting zone. In particular, the occurrence of preferential flow and infiltration rates varied, which helps enhance our understanding of ecohydrological processes in the context of changing land use and hydroclimatic conditions.
期刊：
Science of The Total Environment,2024年906:167663 ISSN：0048-9697
通讯作者：
Yin, GF
作者机构：
[Yin, Gaofei; Yin, GF; Xie, Jiangliu; Ma, Dujuan; Chen, Rui] Southwest Jiaotong Univ, Fac Geosci & Environm Engn, Chengdu 610031, Peoples R China.;[Zhao, Wei] Chinese Acad Sci, Inst Mt Hazards & Environm, Chengdu 610041, Peoples R China.;[Xie, Qiaoyun] Univ Western Australia, Sch Engn, Perth, WA 6009, Australia.;[Wang, Cong] Cent China Normal Univ, Sch Urban & Environm Sci, Key Lab Geog Proc Anal & Simulat Hubei Prov, Wuhan 430079, Peoples R China.;[Lin, Shangrong; Yuan, Wenping] Sun Yat Sen Univ, Guangdong Prov Data Ctr Terr & Marine Ecosyst Carb, Sch Atmospher Sci, Zhuhai 519000, Peoples R China.
通讯机构：
[Yin, GF ] S;Southwest Jiaotong Univ, Fac Geosci & Environm Engn, Chengdu 610031, Peoples R China.
关键词：
Climatic limitations;Light use efficiency model;Plant photosynthesis;Tibetan plateau
摘要：
Plant photosynthesis plays an essential role in regulating the global carbon cycle. Therefore, it is essential to understand the limitations imposed by climate on plant photosynthesis to comprehend the impacts of climate change on land carbon dynamics. In this study, taking gross primary productivity as a direct representation of photosynthesis, we employed a light use efficiency model (i.e., the revised EC-LUE) and factorial analysis method to quantify the spatiotemporal variation of temperature- and water-limitations on plant photosynthesis over the Tibetan Plateau (TP) grasslands during growing season (May to October) in 1983-2018. Results revealed a clear spatiotemporal pattern of the temperature- and water-limitations: temperature is the primary climatic limiting factor in the eastern TP, while water is the primary climatic limiting factor in the western TP; the water- and temperature-limitations prevail in summer and spring/autumn, respectively. The water- and temperature-limitations intensified and alleviated, respectively, during 1983 through 2018. There also was a widespread shift from temperature-limitation to water-limitation in the TP, particularly in midsummer (August). Our findings demonstrated the shifting relative importance of climatic limitations on plant photosynthesis under changing climate, which is crucial for predicting future terrestrial carbon cycle dynamics.
摘要：
Sediment yields in different slope sections on heterogeneous slopes. Note: (a) MTL/MDL; (b) MDL/MTL; (c) MTL/LBC; (d) LBC/MTL; (e) LBC/MDL; (f) MDL/LBC. MTL, MDL and LBC represent the simulated slopes filled with soils derived from nodular limestone, mud‐like limestone and limestone breccia. For heterogeneous slopes, upslopes were the primary contributors to slope deposits and accounted for a substantial portion of sediment yield. Besides, the parent materials of upslopes are a crucial factor influencing the source‐sink relationship. Abstract Understanding erosion, sediment sources and the spatial distribution along heterogeneous slopes is essential for soil and water conservation. In this study, soils derived from nodular limestone, mud‐like limestone and limestone breccia (abbreviated as SMTL, SMDL and SLBC, respectively) were utilized to establish artificial homogeneous and heterogeneous slopes. The homogeneous slopes MTL, MDL and LBC represent SMTL‐, SMDL‐ and SLBC‐filled‐ slopes, respectively. The heterogeneous slopes were abbreviated as MTL/MDL, MDL/LBC and LBC/MTL. Rare earth elements (REEs; lanthanide, cerium and ytterbium) were used to tag soils on the upper and lower slope sections to track sediment transport and deposition. The results showed that for homogeneous slopes, the LBC slope was the most severely eroded, followed by the MDL and MTL slopes. For heterogeneous slopes, the order of erosion was LBC/MTL > MTL/MDL > MDL/LBC. Upslope sections contributed a sizable portion of the total sediment yield, ranging from 51% to 79%. Over time, the difference in the sediment contribution between the upslope and downslope regions decreased and reached equilibrium. Runoff rates on heterogeneous slopes demonstrated an inverse function (R2 > 0.75) in contrast to a logarithmic distribution (R2 > 0.87) on homogeneous slopes. Heterogeneous slopes displayed minimal intersegment variation and the absence of a consistent ordering of the magnitude of hydraulic parameters. Conversely, the hydraulic parameters of homogeneous slopes were consistently ordered across the slope sections. For sediment transport, all slopes exhibited suspension‐dominated flow with percentages greater than 89%. However, the particle size distribution of the sediment of heterogeneous slopes exhibited greater diversity and complexity because of the coexistence of distinct soils. These findings underscore the importance of customized strategies for soil and water conservation in environments characterized by diverse soil parent materials.
关键词：
C losses;greenhouse gas;maize;N leaching;N losses
摘要：
Abstract With the rapid expansion of agriculture on saline–alkaline soils, environmental problems such as increased greenhouse gas (GHG) emissions, eutrophication and soil degradation are becoming increasingly serious. To clarify the characteristics of carbon (C) and nitrogen (N) cycling and their loss mechanisms in cultivated saline–alkaline soils, an undisturbed soil column experiment was conducted to analyse C and N leaching and GHG emissions by applying different fertilizer rates. The experiment had six treatments using N‐(NH4)SO4 over a 40‐day seedling stage, with and without maize. Treatments were: no N with maize (0Nmaize: 0 kg N ha−1), reduced N with maize (RNmaize: 63 kg N ha−1), conventional N with maize (CNmaize: 160 kg N ha−1) and their equivalents without maize (0Nsoil: 0 kg N ha−1; RNsoil: 63 kg N ha−1; CNsoil: 160 kg N ha−1). The results indicated that reduced N with maize reduced the N2O emission by 21%, with N leaching (TN: 41%, NO3−–N: 19%, NH4+ − N: 63%) within 15 days after fertilization, but had no significant effect on CH4 emission compared to conventional N with maize. Therefore, reduced N with maize had the smallest N loss, which accounted for 1.5% of the relative percentage of N flow including N2O (0.3%), N leaching (2%), aboveground biomass N (76%) and root biomass N (22%). Compared to conventional N with maize, reduced N with maize significantly reduced N leaching by 40% because conventional N with maize greatly exceeded the crop N uptake when maize root length was only within 20 cm. Reduced N without maize reduced CO2 emission (19%) compared to conventional N without maize. Uncultivated saline–alkaline soils face greater N overuse and leaching risk because higher NO3−–N leaching (6.9 mg L−1) that occurred in bare soils without fertilization, which increased by 2.6–3.6 times when the N input increased from 63 to 160 kg N ha−1 compared to control. In conclusion, reducing conventional N fertilizer inputs by 60% is not only an effective strategy to reduce CO2 and N2O emission and N leaching but also effectively absorbs C, and the N retained in the soil tillage layer can help to meet maize seedling growth requirements in Solonchaks.
关键词：
Dispersion coefficient;Turbulent flow;Eddy dispersion;Taylor diffusion;Capillary bundle model
摘要：
PurposeFor a homogeneous soil, the traditional laminar flow and well-known Taylor diffusion mechanism cannot interpret dispersivity (linear relationship between dispersion coefficient and pore-water velocity). The objective of this study was to propose a new mechanism and mathematical model based on fluid mechanics.MethodsDue to the roughness of the wall of a soil capillary tube, a new turbulent flow is proposed to be eddies at the wall and laminar flow at the main stream of a soil capillary tube. A new eddy dispersion mechanism is that the behavior of solute in the eddies follows random walks and the solute mixes instantly between the wall and main stream in a tube at the microscale. The new turbulent flow and eddy dispersion occur when the pore-water velocity is greater than a critical value. Transition to the new mechanism from a laminar flow in the tube and molecular diffusion is described by a plateau-linear model. It was tested by published datasets of pore-water velocity and dispersion coefficient in miscible displacement experiments on a loam and a sandy loam.ResultsThe plateau-linear model fit the published datasets. The estimate of dispersivity was 0.135 cm. The transition of water flow and dispersion process occurred at the critical pore-water velocity 0.216 cm h-1 or Reynolds number of the order of 10-6.ConclusionDispersivity in homogeneous soils was interpretated by the turbulent water flow and the eddy dispersion mechanism. It is determined by the structure of rough wall in a soil capillary tube at the miscroscale.
期刊：
GEOPHYSICAL RESEARCH LETTERS,2024年51(4) ISSN：0094-8276
通讯作者：
Yin, GF
作者机构：
[Wang, Cong] Cent China Normal Univ, Sch Urban & Environm Sci, Key Lab Geog Proc Anal & Simulat Hubei Prov, Wuhan, Peoples R China.;[Yin, Gaofei; Yin, GF; Yang, Yajie] Southwest Jiaotong Univ, Fac Geosci & Environm Engn, Chengdu, Peoples R China.;[Xie, Qiaoyun] Univ Western Australia, Sch Engn, Perth, WA, Australia.;[Xu, Baodong] Huazhong Agr Univ, Macro Agr Res Inst, Coll Resource & Environm, Wuhan, Peoples R China.;[Verger, Aleixandre] CSIC UV GV, CIDE, Valencia, Spain.
通讯机构：
[Yin, GF ] S;Southwest Jiaotong Univ, Fac Geosci & Environm Engn, Chengdu, Peoples R China.
摘要：
Abstract Remote sensing detection of autumn phenology is challenging and highly uncertain, as exemplified by the observed divergence in autumn phenology extracted from different proxies. Here, we compared the autumn phenology derived from Solar‐Induced chlorophyll Fluorescence (SIF), Chlorophyll/Carotenoid Index (CCI), Enhanced Vegetation Index (EVI), and Normalized Difference Vegetation Index (NDVI) over deciduous forest sites. We observed a clear temporal sequence in the derived autumn phenology from various proxies: SIF < CCI < EVI < NDVI. Comparison with field measurements supported that SIF, EVI, and NDVI can successfully capture the attenuation of photosynthetic activity, leaf coloration, and leaf fall, respectively. The sequence among the autumn phenology derived from those proxies was also consistent with their responses to climate cues, where SIF had the highest partial correlation coefficient to solar radiation in autumn, followed by CCI, EVI, and NDVI, while NDVI was more correlated with temperature, followed by EVI, CCI, and SIF.
期刊：
Science of The Total Environment,2024年921:171167 ISSN：0048-9697
通讯作者：
Fang, J
作者机构：
[Fang, Jian; Liu, Yuxin; Xu, Yating; Fang, J] Cent China Normal Univ, Coll Urban & Environm Sci, Wuhan 430079, Peoples R China.;[Fang, Jian; Liu, Yuxin; Xu, Yating] Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat Hubei Prov, Wuhan 430079, Peoples R China.;[Tao, Kai] Beijing Normal Univ, Fac Geog Sci, Beijing 100875, Peoples R China.;[Fang, Jiayi] Hangzhou Normal Univ, Inst Remote Sensing & Earth Sci, Sch Informat Sci & Technol, Hangzhou 311121, Peoples R China.
通讯机构：
[Fang, J ] C;Cent China Normal Univ, Coll Urban & Environm Sci, Wuhan 430079, Peoples R China.
关键词：
Flood seasonality;Spatial-temporal variation;Synchronous flood;Yangtze River basin
摘要：
Floods are some of the most frequent and severe natural hazards worldwide. In the context of climate change, the risk of extreme floods is expected to increase in the future. While, the trends in flood timing and risk for flood synchronization remain unclear. In this study, the seasonality of flood peaks, annual maximum rainfall, and annual maximum soil moisture in the Yangtze River Basin were examined using observational and reanalysis data from 1949 to 2020. Changes in the timing of extreme events may increase the possibility of concurrent flooding, therefore the risk for synchronous floods were further explored. The results indicate that the seasonality of floods has a strong consistency with that of annual maximum rainfall. In the southern Yangtze River Basin, floods usually occur between early June and early July, with a delayed trend. However, they occur slightly later in the north, generally from late July to early August, with a tendency of advance. Overall, the timing of floods is positively correlated with rainfall and soil moisture peaks, and the correlation is much stronger for annual maximum rainfall. However, for more intense floods or for larger catchments, soil moisture plays an important role in modulating the variations in flood timing. Reverse latitudinal changes in flood timing are expected to result in more synchronous floods. The synchrony frequency exceeded 60 % for most of the stations, and the frequency was increasing for nearly half of the region, especially in the middle reaches, Poyang Lake and south of Dongting Lake. In addition, the flood synchrony scale in the south of the basin showed significant upward trends. These findings would provide important implications for flood risk management and adaptive strategy development.
摘要：
Although snow cover is a major factor affecting vegetation in alpine regions, it is rarely introduced into ecological niche models in alpine regions. Snow phenology over the Tibetan Plateau (TP) was estimated using a daily passive microwave snow depth dataset, and future datasets of snow depth and snow phenology were projected based on their sensitivity to temperature and precipitation. Furthermore, the potential habitats of five alpine vegetation types on the TP were predicted under two future climate scenarios (SSP245 and SSP585) by using a model with incorporated snow variables, and the driving factors of habitat change were analyzed. The results showed that the inclusion of snow variables improved the prediction accuracy of MaxEnt model, particularly in alpine meadow habitats. By the end of the 21st century, the potential habitats of steppes, meadows, shrubs, deserts, and coniferous forests on the TP will migrate to higher latitudes and altitudes, in which the potential habitats of alpine desert will recede (replaced by alpine steppe), and the potential habitats of other four vegetation types will expand. The random forest importance analysis showed that the recession of potential habitat was mainly driven by the increase in average annual temperature, and the expansion of potential habitat was mainly driven by the increase in precipitation. With the gradual increase in temperature and precipitation in the future, the snow depth and snow cover duration days will decrease, which may further lead to the transition of vegetation types from cold-adapted to warm-adapted on the TP. Our study highlights both that the prediction accuracy of alpine vegetation was improved by incorporating snow variables into the species distribution model, and that a changing climate will likely have a powerful influence on the distribution of alpine vegetation across the TP.
期刊：
Journal of Soils and Sediments,2024年24(2):829-846 ISSN：1439-0108
通讯作者：
Tian, P
作者机构：
[Ping, Yaodong; Tian, Pei; Guo, Yahui; Tian, P] Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat Hubei Prov, Wuhan 430079, Peoples R China.;[Luo, Li] Northwest Agr & Forestry Univ, Coll Water Resources & Architectural Engn, Yangling 712100, Peoples R China.;[Zhu, Zhanliang; Gong, Yuwei] Beijing Normal Univ, Coll Water Sci, Beijing 100091, Peoples R China.;[Cui, Yongsheng] Fujian Agr & Forestry Univ, Forestry Coll, Fuzhou 350002, Peoples R China.;[Chen, Lin] Univ Calif Riverside, Dept Environm Sci, Riverside, CA 92521 USA.
通讯机构：
[Tian, P ] C;Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat Hubei Prov, Wuhan 430079, Peoples R China.
关键词：
Soil erosion sensitivity;RUSLE;Deep learning-LSTM model;Geographic detector;Hilly areas of Hubei Province
摘要：
Purpose Hilly areas are highly susceptible to soil erosion. This study aims to discover the drivers of soil erosion, identify soil erosion-sensitive areas, and predict future soil erosion in typical hilly areas of Hubei Province, China, using combined RUSLE and LSTM models.Materials and methods In this study, soil erosion in hilly areas of Hubei Province from 2000 to 2020 was quantitatively analyzed using the revised universal soil loss equation (RUSLE), and the soil erosion sensitivity evaluation system was constructed, a geographic detector was employed to identify the main drivers of soil erosion sensitivity, and using the long short-term memory neural network model (LSTM) to predict soil erosion in 2025.Results and discussions The results showed that most areas were dominated by slight and moderate erosion. Slope and vegetation coverage were identified as the core elements influencing the space heterogeneity of soil erosion. Soil erosion sensitivity was mainly composed of moderate sensitivity, accounting for more than 70% of the total area. The strong and extreme sensitivity demonstrated a downward trend with the continued implementation of slope management and forest rehabilitation from slope agriculture, whereas the sensitivity was still higher in the northwest and southwest Hubei Province. Regions with severe soil erosion had high sensitivity, and the spatial distribution of the two is strongly coherent. Areas with surface relief > 300 m and vegetation cover < 30% had the highest sensitivity and should be highly valued. The percentage of moderate and higher soil erosion area in 2025 was 3.77% lower than in 2020, but severe erosion still exists in the northwest and southwest Hubei Province.Conclusions Soil erosion sensitivity in the western part of the study area was the highest, followed by the southeast, and the overall erosion sensitivity was gradually decreasing during the studied period. In the future, soil erosion intensity will show a downward trend, whereas the deployment of soil and water conservation measures in soil erosion-sensitive areas should still be strengthened. The results are helpful for accurate soil erosion control and prediction in the hilly areas of Hubei Province, China.
摘要：
Extreme rainfall events pose a severe challenge to soil and water conservation, even in areas with high vegetation cover on the Loess Plateau. In this study, the artificial extreme rainfalls with cumulative rainfall of 270 mm and intensity of 60 mm · hr−1 were conducted on in-situ experimental plots (20 × 2.5 m) on a loess gully–slope with gradients of 35°–40° that were treated with different grass coverage: (0%, 30%–40%, 70%–80%, >90%). The ephemeral gully/rill and shallow landslide occurred in plots were analyzed. Revegetation changed the erosion type on gully–slope, reducing gully erosion but promoting shallow landslide due to the change from infiltration–excess runoff to saturation–excess runoff. Under grass coverage of >90%, over 95% of rainfall seeped into the soil, and subsurface flow was generated due to the lower saturated hydraulic conductivity of underlying soil, which increased the possibility of landslides. The average erosion rate (0.36–3.29 g · m−2 min−1; no obvious erosion) in plots with 70%–80% coverage was 95.5% lower than that in bare land plots (27.8–47.5 g · m−2 min−1; ephemeral gully erosion), while due to landslides the average erosion rate in plots with >90% coverage (135.1–184.3 g · m−2 min−1) was 86.5 times higher than that in plots with 70%–80%. For grass, a coverage of 70%–80% was most effective in preventing soil erosion, controlling gully erosion and preventing landslides under extreme rainfall. These results deepen the understanding of the complex relationship between vegetation, gully erosion, and landslides in ecologically sensitive areas.
Vegetation changed the erosion type on slope from water erosion to gravity erosion
High-coverage vegetation promoted shallow landslides under extreme rainfall
For grass cover, a coverage of 70%–80% was most effective in preventing soil erosion
摘要：
Located in the northwestern edge of the modern Asian summer monsoon (ASM), the northeastern Tibetan Plateau (NETP) is sensitive to changes of the ASM climate. However, variations of climate and vegetation during the Holocene remain unclear in this marginal region of the monsoon climate. Here we present a Holocene highresolution pollen record from Lake Gahai in the NETP since 11.4 (+/- 0.3) ka BP to reconstruct regional vegetation history. A quantitative reconstruction of precipitation is also tried using fossil pollen assemblages. Results suggested that before 10.2 (+/- 0.4) ka BP in the early Holocene, the vegetation cover was low and the climate was arid. A relatively wet climate indicated by high A/C ratio values occurred between 10.2 (+/- 0.4) and 7.4 (+/- 0.2) ka BP. After 7.4 (+/- 0.2) ka BP, the A/C ratio decreased, indicating that the climate was getting drier. The overall environment of the basin has become similar to modern conditions since 5.4 (+/- 0.1) ka BP. The reconstructed precipitation is not comparable with the tree-ring-based reconstruction from the Delingha region, although the reconstruction processes passed significance tests statistically. In addition to abundant surface pollen data and gradually improved quantitative reconstruction techniques, other factors such as the environmental settings and vegetation dynamics also affect the reliability of the pollen-based quantitative reconstruction of regional precipitation. Therefore, the applicability of pollen data for quantitative precipitation reconstruction in arid regions should be assessed and the results should be treated cautiously.
