Agricultural greenhouse gas(GHG)emissions are influenced by a combination of climate,soil and agricultural management practices.Over the past 30 years,approximately 5% of China's cropland has shifted from the sout...Agricultural greenhouse gas(GHG)emissions are influenced by a combination of climate,soil and agricultural management practices.Over the past 30 years,approximately 5% of China's cropland has shifted from the south to the north.This shift has significantly altered the geographical environment,with potential substantial impacts on agricultural GHG emissions.This study used the DeNitrification DeComposition(DNDC)process-based model to simulate GHG emissions(CH_(4)and N_(2)O)from the production of China's 10 major food crops and explored changes in agricultural GHG emissions caused by the spatial shift of cropland in China.Results from the validated DNDC model indicate that total emissions from the major food crop production in China were approximately 343 Tg CO_(2)-eq yr^(-1)with CH_(4)emissions accounting for about 74%.Meanwhile,the spatial shift of cropland from 1990 to 2020 resulted in a 3% decrease in average CH_(4)emissions per unit cropland area and an 8% increase in average N_(2)O emissions per unit cropland area,respectively.The expansion of dryland in the Northwest Arid Region emitted less CH_(4)but significantly more N_(2)O,thereby driving changes in national GHG emissions.This study provides a scientific foundation for the sustainable use of cropland and the formulation of strategies to reduce agricultural GHG emissions.展开更多
Croplands are decreasing due to the expansion of urban areas into rural communities and to some extent due to sand accumulations. Increases in population numbers, new development, in addition to the accumulation of sa...Croplands are decreasing due to the expansion of urban areas into rural communities and to some extent due to sand accumulations. Increases in population numbers, new development, in addition to the accumulation of sand and soil salinity are the major driving force leading to abandonment and shrinking of cropland. The aim of this study was to investigate and assess to what extent agricultural lands are affected by urban development in the Al Hassa oasis, Eastern region in Saudi Arabia by employing Landsat time series data of years 1988, 2000 and 2017 as the main source of information. A set of ground truth, control points (GCPs) was also used besides population census data. Unsupervised classifications approach, Normalized Difference Vegetation Index (NDVI) and change detection methods were used here. Urban area during 2000-2017 exhibits much higher increase compared to 1988-2000, while the arable lands declined to −3.4% in 1988-2000 and increased to 22% during 2000-2017. The data analysis results provided new accurate numerical information supported by a graphical representation in regard to the decrease and increase in urban and agricultural lands. Therefore the findings of this study should be considered by decision maker for improving and development the agriculture activities in rural and urban communities.展开更多
The soil organic carbon (SOC) pool is the largest component of terrestrial carbon pools. With the construction of a geographically referenced database taken from the second national general soil survey materials and b...The soil organic carbon (SOC) pool is the largest component of terrestrial carbon pools. With the construction of a geographically referenced database taken from the second national general soil survey materials and based on 1546 typical cropland soil profiles, the paddy field and dryland SOC storage among six regions of China were systematically quantified to characterize the spatial pattern of cropland SOC storage in China and to examine the relationship between mean annual temperature, precipitation, soil texture features and SOC content. In all regions, paddy soils had higher SOC storage than dryland soils, and cropland SOC content was the highest in Southwest China. Climate controlled the spatial distribution of SOC in both paddy and dryland soils, with SOC storage increasing with increasing precipitation and decreasing with increasing temperature.展开更多
Soil organic carbon （SOC） is one of the centre issues related to not only soil fertility but also environmental safety. Assessing SOC dynamics in croplands has been a challenge in China for long due to the lack of a...Soil organic carbon （SOC） is one of the centre issues related to not only soil fertility but also environmental safety. Assessing SOC dynamics in croplands has been a challenge in China for long due to the lack of appropriate methodologies and data sources. As an alternative approach for studying SOC dynamics, process-based models are adopted to meet the needs. In this paper, a process-based model, DeNitrification-DeComposition （DNDC）, was applied to quantify the SOC storage and the spatial distribution in croplands of China in 2003, with the support of a newly compiled county-level soil/ climate/land use database. The simulated results showed that the total SOC storage in the top layer （0-30 cm） of the 1.18 × 10^8 ha croplands of China is 4.7-5.2 Pg C in 2003 with an average value of 4.95 Pg C. The SOC storage in the northeastern provinces （1.3 Pg C） accounts for about 1/4 of the whole national totals due to their dominantly fertile soils with high organic matter content. SOC density ranges from 3.9 to 4.4 kg C m 2, with an average of 4.2 kg C m^-2, a level is much lower than the world average level. The model results also indicated that high rates of SOC losses occurred in the croplands with the most common cropping patterns in China as like single soybean 〉 maize 〉 paddy 〉 cotton 〉 winter wheat and corn rotation. The results reported in this paper showed that there was still a great potential for improving SOC status in most croplands of China by adopting proper farming practices and land-use pattern. Therefore, long-term policy to protect SOC is urgently needed.展开更多
Crop harvesting and residue removal from croplands often result in imbalanced biogeochemical cycles of carbon and nutrients in croplands, putting forward an austere challenge to sustainable agricultural production. As...Crop harvesting and residue removal from croplands often result in imbalanced biogeochemical cycles of carbon and nutrients in croplands, putting forward an austere challenge to sustainable agricultural production. As a beneficial element, silicon（Si） has multiple eco-physiological functions, which could help crops to acclimatize their unfavorable habitats. Although many studies have reported that the application of Si can alleviate multiple abiotic and biotic stresses and increase biomass accumulation, the effects of Si on carbon immobilization and nutrients uptake into plants in croplands have not yet been explored. This review focused on Si-associated regulation of plant carbon accumulation, lignin biosynthesis, and nutrients uptake, which are important for biogeochemical cycles of carbon and nutrients in croplands. The tradeoff analysis indicates that the supply of bioavailable Si can enhance plant net photosynthetic rate and biomass carbon production（especially root biomass input to soil organic carbon pool）, but reduce shoot lignin biosynthesis. Besides, the application of Si could improve uptake of most nutrients under deficient conditions, but restricts excess uptake when they are supplied in surplus amounts. Nevertheless, Si application to crops may enhance the uptake of nitrogen and iron when they are supplied in deficient to luxurious amounts, while potassium uptake enhanced by Si application is often involved in alleviating salt stress and inhibiting excess sodium uptake in plants. More importantly, the amount of Si accumulated in plant positively correlates with nutrients release during the decay of crop biomass, but negatively correlates with straw decomposability due to the reduced lignin synthesis. The Si-mediated plant growth and litter decomposition collectively suggest that Si cycling in croplands plays important roles in biogeochemical cycles of carbon and nutrients. Hence, scientific Si management in croplands will be helpful for maintaining sustainable development of agriculture.展开更多
Regional aridity is increasing under global climate change,and therefore the sustainable use of water resources has drawn attention from scientists and the public.Land-use changes can have a significant impact on grou...Regional aridity is increasing under global climate change,and therefore the sustainable use of water resources has drawn attention from scientists and the public.Land-use changes can have a significant impact on groundwater recharge in arid regions,and quantitative assessment of the impact is key to sustainable groundwater resources management.In this study,the changes of groundwater recharge after the conversion of natural lands to croplands were investigated and compared in inland and arid region,i.e.,the northern slope of the Tianshan Mountain.Stable isotopes suggest that soil water in topsoil(<2 m)has experienced stronger evaporation under natural lands than croplands,and then moves downward as a piston flow.Recharge was estimated by the tracer-based mass balance method,i.e.,chloride and sulfate.Recharge rates under natural conditions estimated by the chloride mass balance(CMB)method were estimated to be 0.07 mm/a in deserts and 0.4 mm/a in oases.In contrast,the estimated groundwater recharge ranged from 61.2 mm/a to 44.8 mm/a in croplands,indicating that groundwater recharge would increase significantly after land changes from natural lands to irrigated croplands in arid regions.Recharge estimated by the sulfate mass balance method is consistent with that from the CMB method,indicating that sulfate is also a good tracer capable of estimating groundwater recharge.展开更多
Studies on long-term change of cropland is of great significance to the utilization of land resources and the implementation of scientific agricultural policies. The Korean Peninsula, adjacent to China, plays an impor...Studies on long-term change of cropland is of great significance to the utilization of land resources and the implementation of scientific agricultural policies. The Korean Peninsula, adjacent to China, plays an important role in the international environment of Northeast Asia. The Korean Peninsula includes South Korea and North Korea—two countries that have a great difference in their institutions and economic developments. Therefore, we aim to quantify the spatiotemporal changes of croplands in these two countries using Landsat Thematic Imager(TM) and Operational Land Imager(OLI) imagery, and to compare the differences of cropland changes between the two countries. This paper take full advantage of ODM approach(object-oriented segmentation and decision-tree classification based on multi-season imageries) to obtain the distribution of croplands in 1990 and 2015. Results showed that the overall classification accuracy of cropland data is 91.10% in 1990 and 92.52% in 2015. The croplands were mainly distributed in areas with slopes that were less than 8° and with elevations that were less than 300 m in the Korean Peninsula. However, in other region(slope > 8° or elevation > 300 m), the area and proportion of North Korea's croplands were significantly higher than that of South Korea. Croplands significantly increased by 15.02% in North Korea from 1990 to 2015. In contrast, croplands in South Korea slightly decreased by 1.32%. During the 25 years, policy shift, economic development, population growth, and urban sprawl played primary roles for cropland changes. Additionally, the regional differences of cropland changes were mainly due to different agriculture policies implemented by different countries. The achievements of this study can provide scientific guidance for the protection and sustainability of land resources.展开更多
Mount Kilimanjaro and the Taita Hills are adjacent montane areas that experience similar climate and agricultural activity, but which differ in their geologic history, nature of elevation gradients and cultures. We as...Mount Kilimanjaro and the Taita Hills are adjacent montane areas that experience similar climate and agricultural activity, but which differ in their geologic history, nature of elevation gradients and cultures. We assessed differences in cropland above ground carbon (AGC) between the two sites and against environmental variables. One hectare sampling plots were randomly distributed along elevational gradients stratified by cropland type;AGC was derived from all trees with diameter ≥ 10 cm at breast height in each plot. Predictor variables were physical and edaphic variables and human population. A generalized linear model was used for predicting AGC with AIC used for ranking models. AGC was spatially upscaled in 2 km buffer and visually compared. Kilimanjaro has higher AGC in cropped and agroforestry areas than the Taita Hills, but only significant difference in AGC variation in agroforestry areas (F = 9.36, p = 0.03). AGC in cropped land and agroforestry in Kilimanjaro has significant difference on mean (t = 4.62, p = 0.001) and variation (F = 17.41, p = 0.007). In the Taita Hills, significant difference is observed only on the mean AGC (t = 4.86, p = 0.001). Common tree species that contribute the most to AGC in Kilimanjaro are Albizia gummifera and Persea americana, and in the Taita Hills Grevillea robusta and Mangifera indica. Significant and univariate predictors of AGC in Mount Kilimanjaro are pH (R2 = 0.80, p = 0.00) and EVI (R2 = 0.68, p = 0.00). On Mount Kilimanjaro, the top multivariate model contained SOC, CEC, pH and BLD (R2 = 0.90, p = 0.00), whereas in the Taita Hills, the top multivariate model contained elevation, slope and population (R2 = 0.89, p = 0.00). Despite of the difference in land management history of Mount Kilimanjaro and the Taita Hills, mean of AGC in croplands does not differ significantly. Difference occurs on variation of AGC, type of trees contributing AGC, and environmental variables that explain AGC distribution. The research results provide reference for management of carbon sequestration on inhabited montane areas.展开更多
Climate change and the increasing frequency of floods have undermined China’s food security.Creating detailed maps of flooded croplands is essential to improve prevention and adopt effective adaptation initiatives.Pr...Climate change and the increasing frequency of floods have undermined China’s food security.Creating detailed maps of flooded croplands is essential to improve prevention and adopt effective adaptation initiatives.Previous large-scale flood mapping efforts were hampered by limited meteorological and hydrological data,and the susceptibility of optical satellite images to cloud cover,leading to high uncertainty when downscaled to the cropland-scale.Here,using 4968 near-real-time(NRT)Sentinel-1 SAR(S1)images(spatial resolution:10 m),we generated China’s first set of high-resolution flooded cropland maps covering the period from 2017 to 2021.Our results demonstrate that croplands accounted for 43.8%to49.8%of China’s total flooded areas(ranging from 82,175 km^(2) to 122,037 km^(2)).We also created highresolution flood maps specifically for rice and maize crops.The inundated rice areas ranged from 8428 km^(2) to 22,123 km^(2),accounting for 22.34%to 41.91%of the annual flooded croplands,or 2.82%to7.45%of the annual rice cropland.In comparison,the inundated maize cropland fluctuated from 2619 km^(2) to 5397 km^(2),representing 5.38%to 13.56%of the annual flooded croplands.Our findings revealed extensive floods in rural areas,highlighting the urgent need to prioritize flood prevention and mitigation efforts in such regions.In light of China’s allocation of an additional 1-trillion-RMB treasury bonds for water infrastructure projects,the high-resolution flood maps can be used to select sites for flood control projects,and evaluate the impact of flooding on crop yields and food security,thus targeting poverty alleviation in rural areas of China.展开更多
Reconstructing Canada's cropland over the past millennium reveals human-land relationships and informs strategies for climate change mitigation.Canada's population and per capita cropland area are estimated fo...Reconstructing Canada's cropland over the past millennium reveals human-land relationships and informs strategies for climate change mitigation.Canada's population and per capita cropland area are estimated for 1000–1840 by analyzing and revising historical documents.These estimates are then multiplied and combined with census data to obtain the cropland area of Canada for 1000–2015.Then,using a sophisticated land suitability map for cultivation,a cropland area allocation model is constructed,and the spatial pattern of cropland in Canada for the past millennium is mapped using the model and the maximum extent of cropland in different periods.The results indicated that the cropland area increased from 0.078 million ha in 1000 to38.690 million ha in 2015,with slow growth before 1900 and rapid growth thereafter.The spatial distribution of cropland in Canada expands gradually from the Great Lakes-St.Lawrence Lowlands to the western prairie area,with land use intensity increasing and exhibiting spatial heterogeneity over the past millennium.This high-resolution,spatially explicit reconstruction aligns more closely with Canada's agricultural history than several noteworthy global datasets.Archaeological data are needed to enhance subsequent land use estimation and mapping for Canada.展开更多
Mapping croplands,including fallow areas,are an important measure to determine the quantity of food that is produced,where they are produced,and when they are produced(e.g.seasonality).Furthermore,croplands are known ...Mapping croplands,including fallow areas,are an important measure to determine the quantity of food that is produced,where they are produced,and when they are produced(e.g.seasonality).Furthermore,croplands are known as water guzzlers by consuming anywhere between 70%and 90%of all human water use globally.Given these facts and the increase in global population to nearly 10 billion by the year 2050,the need for routine,rapid,and automated cropland mapping year-after-year and/or season-after-season is of great importance.The overarching goal of this study was to generate standard and routine cropland products,year-after-year,over very large areas through the use of two novel methods:(a)quantitative spectral matching techniques(QSMTs)applied at continental level and(b)rule-based Automated Cropland Classification Algorithm(ACCA)with the ability to hind-cast,now-cast,and future-cast.Australia was chosen for the study given its extensive croplands,rich history of agriculture,and yet nonexistent routine yearly generated cropland products using multi-temporal remote sensing.This research produced three distinct cropland products using Moderate Resolution Imaging Spectroradiometer(MODIS)250-m normalized difference vegetation index 16-day composite time-series data for 16 years:2000 through 2015.The products consisted of:(1)cropland extent/areas versus cropland fallow areas,(2)irrigated versus rainfed croplands,and(3)cropping intensities:single,double,and continuous cropping.An accurate reference cropland product(RCP)for the year 2014(RCP2014)produced using QSMT was used as a knowledge base to train and develop the ACCA algorithm that was then applied to the MODIS time-series data for the years 2000–2015.A comparison between the ACCA-derived cropland products(ACPs)for the year 2014(ACP2014)versus RCP2014 provided an overall agreement of 89.4%(kappa=0.814)with six classes:(a)producer’s accuracies varying between 72%and 90%and(b)user’s accuracies varying between 79%and 90%.ACPs for the individual years 2000–2013 and 2015(ACP2000–ACP2013,ACP2015)showed very strong similarities with several other studies.The extent and vigor of the Australian croplands versus cropland fallows were accurately captured by the ACCA algorithm for the years 2000–2015,thus highlighting the value of the study in food security analysis.展开更多
Ecological stoichiometry is an important indicator presenting multiple elements balance in agro-ecosystems.However,information on microbial communities and nutrient stoichiometry in soil aggregate fractions under diff...Ecological stoichiometry is an important indicator presenting multiple elements balance in agro-ecosystems.However,information on microbial communities and nutrient stoichiometry in soil aggregate fractions under different croplands(rice,maize,and soybean fields)remains limited.Thus,this study investigated water-stable aggregate structure and their internal nutrient stoichiometry under different croplands and ascertain their interaction mechanism with microbial communities.The results showed that no significant difference on the carbon-to-nitrogen ratio(C:N)in soil aggregate fractions was observed,while the carbon-to-phosphorus ratio(C:P)and the nitrogen-to-phosphorus ratio(N:P)were ranked as rice field>maize field>soybean field,and were higher in mega-aggregates(ME,>1 mm).General fatty acid methyl ester(FAME),Gram-positive bacteria(G+),and Gramnegative bacteria(G−)were predominant microbial communities in all croplands and tented to condense into coarse-aggregates.Redundancy analysis(RDA)demonstrated that N:P ratio was primary environmental controls on the distribution of soil microorganisms.In the Sanjiang Plain,N was the nutrient element limiting agro-ecosystem productivity,and rice cultivation is expected to improve the N-limited nutrient status.展开更多
In the study area (Yanjiaping Village, Hebei Province, China), grazing extensity varies at different loca-tions, small and discontinuous croplands are imbedded in some arid grassland, which are habitats for the melita...In the study area (Yanjiaping Village, Hebei Province, China), grazing extensity varies at different loca-tions, small and discontinuous croplands are imbedded in some arid grassland, which are habitats for the melitaeine butterflies, Euphydryas aurinia and Melitaea phoebe. These two species of butterflies coexist in this area, in which grazing and cultivation are the main disturbances. Grazing and cultivation have a reciprocal effect on E. aurinia, rather than M. phoebe. We observed that E. aurinia preferred to occupy patches with moderate grazing and imbedded with small and discontinuous croplands, where E. aurinia also has high population density. The percentage of E. aurinia larval groups in the ribbings was significantly higher than that of M. phoebe, whereas larvae of both species tended to increase in recent years. Our data also showed that the population density and the patch occupancy rate of both E. aurinia and M. phoebe were the highest under moderate grazing. It indicates that cultivation of small and dis-continuous croplands within the patch has a significant effect on the population density of both spe-cies of melitaeine butterflies. Thus, to artificially create or maintain semi-natural habitats, comple-mented by moderate grazing, might be an ecological strategy to conserve melitaeine butterflies effec-tively. Considering the distinct impacts of cultivation and grazing on the population distribution and dynamics of the two different species, human disturbance in the mountainous area might be strategi-cally involved in proposing conservation plans for the target species in the future.展开更多
Cropland nitrate leaching is the major nitrogen(N) loss pathway, and it contributes significantly to water pollution. However, cropland nitrate leaching estimates show great uncertainty due to variations in input data...Cropland nitrate leaching is the major nitrogen(N) loss pathway, and it contributes significantly to water pollution. However, cropland nitrate leaching estimates show great uncertainty due to variations in input datasets and estimation methods. Here, we presented a re-evaluation of Chinese cropland nitrate leaching, and identified and quantified the sources of uncertainty by integrating three cropland area datasets, three N input datasets, and three estimation methods. The results revealed that nitrate leaching from Chinese cropland averaged 6.7±0.6 Tg N yr^(-1)in 2010, ranging from 2.9 to 15.8 Tg N yr^(-1)across 27 different estimates. The primary contributor to the uncertainty was the estimation method, accounting for 45.1%, followed by the interaction of N input dataset and estimation method at 24.4%. The results of this study emphasize the need for adopting a robust estimation method and improving the compatibility between the estimation method and N input dataset to effectively reduce uncertainty. This analysis provides valuable insights for accurately estimating cropland nitrate leaching and contributes to ongoing efforts that address water pollution concerns.展开更多
Cropland suitability analysis is a vital tool for ensuring food security and sustainable agriculture,coordinating ecological space with human activity space on the Qinghai-Tibet Plateau(QTP).However,there are few stud...Cropland suitability analysis is a vital tool for ensuring food security and sustainable agriculture,coordinating ecological space with human activity space on the Qinghai-Tibet Plateau(QTP).However,there are few studies on complete and accurate cropland suitability assessments on the QTP,let alone on identifying key potential areas for cropland development.We used a novel assessment model to generate a 30-m cropland suitability map for the QTP.The identification of areas with cropland development potential and the evaluation of potentially available cropland were further integrated into a unified analytical framework.We found that only 10.18%of the study area is suitable for large-scale and permanent cropland.Moreover,approximately 72.75%of the existing cropland was found to be distributed in suitable or marginally suitable areas.Considering the trade-offs related to irrigation water supply convenience,approximately 1.07%of the study area was identified as having high potential for cropland development.Four key potential areas were further identified:the Shannan Valley,the Nyingchi Valley,the Zanda Valley,and the Gonghe Basin.These areas boast abundant potentially available cropland resources and ecological resettlement capacities,which leads us to recommend strategic priorities for comprehensive land consolidation and water development.This study has practical significance for optimizing land resource allocation and guiding decision-making related to ecological migration on the QTP.展开更多
Cropland abandonment is prevalent throughout China,particularly in mountainous regions.However,the varying degrees of land marginalization and the specific factors influencing different types of cropland remain insuff...Cropland abandonment is prevalent throughout China,particularly in mountainous regions.However,the varying degrees of land marginalization and the specific factors influencing different types of cropland remain insufficiently understood.This knowledge gap hampers targeted management strategies for mitigating cropland abandonment in these areas.This study used spatial analysis,logistic regression,and random forest models to explore the spatial patterns and key drivers of abandonment across flatland,terrace,and slopeland in Chongyi county,a mountainous region in Jiangxi Province of South China,utilizing data from the 2009 and 2019 national land surveys of China.Results showed that the overall cropland abandonment rate in Chongyi county was 36.46%,with particularly high rates in core terrace conservation areas.Abandoned cropland was spatially clustered,predominantly in high-elevation regions.The abandonment rates were 9.71%for flatland,37.52%for terrace,and 43.02%for slopeland.Variations in vegetation cover on abandoned cropland suggest that abandonment started earlier on slopeland and later extended to terraces and flatlands.The factors driving the abandonment of flatland,terrace,and slopeland included land altitude,cultivation height difference,and distance to forest land,respectively.Consequently,the results recommend implementing land consolidation and developing small machinery projects for the fragmented flatland.Promoting the multifunctional use of terraces could realize their ecological value.Additionally,the Program of Converting Farmland to Forest should be implemented on the low-quality slopeland.展开更多
In many existing dictionaries,cropland is defined as land that is suitable for or used to grow crops.It has several synonyms,such as“farmland”,“arable land”,and“cultivated land”.However,in scientific literature,...In many existing dictionaries,cropland is defined as land that is suitable for or used to grow crops.It has several synonyms,such as“farmland”,“arable land”,and“cultivated land”.However,in scientific literature,the nuances of these terms are often overlooked.The inconsistent terminology usage could lead to ambiguity and confusion in research and policy discussions.In particular,it creates difficulties for newcomers and students when they search for precise information in the published literature.Hence,exploring the variations of terminology applications is important for the cropland-related research community.In this study,the differences in six cropland-related terminologies were explored through a review of 5,214 scientific articles,by employing the independence test,clustering approach,and correlation analysis.The results showed that disparities exist across disciplines.For example,biodiversity&conservation studies preferentially use“farmland”to highlight effects from human activities,while studies in geology and computer science use“cropland”.The term“cultivated land”tends to be used in geography research for clear geographical demarcation,while“arable land”is related to engineering studies.Moreover,further disparities based on the geographical affiliations of the authors were found.The correlation between China and“cultivated land”was reliable and a close link was found between“agricultural land”and the USA.The regional variations in cropland terminology can be influenced by multiple factors,including the degree of agricultural mechanization,colonial history,and migration patterns.This study reveals variations in cropland-related terminology across disciplines and regions.The results highlight the importance of standardizing cropland terminology to foster interdisciplinary research,improve data comparability,and support global agricultural and environmental policymaking.展开更多
Sustainable Development Goal 2(SDG 2,zero hunger)highlights that global hunger and food insecurity have worsened since 2015,driven in part by growing imbalance.Addressing the challenge of achieving SDG 2 in the face o...Sustainable Development Goal 2(SDG 2,zero hunger)highlights that global hunger and food insecurity have worsened since 2015,driven in part by growing imbalance.Addressing the challenge of achieving SDG 2 in the face of rapid global population growth requires sustained attention to global and national cropland changes.Accurately quantifying the correlation between population and cropland area(i.e.,SDG 2.4.1 per capita cropland)and analyzing the trends of global cropland imbalance are essential for a comprehensive understanding of SDG 2.In this study,we utilized a new global 30 m land-cover dynamic dataset(GLC_FCS30D)to analyze cropland dynamics,quantify per capita cropland and its changes across various countries and levels of development.Our results indicate that the global cropland area expanded by 0.944 million km^(2)from 1985 to 2022,with an average expansion rate of 2.42×10^(4)km^(2)/yr.However,the global per capita cropland area decreased from 0.347 ha in 1985 to 0.217 ha in 2022,mainly due to a higher population increase of nearly 65%in the same period.In the context of globalization,cropland expansion and per capita cropland exhibited spatial imbalances globally,particularly in developing countries.Developing countries saw an increase in total cropland area by 7.09%but a significant decrease in per capita cropland area by 37.38%.From a temporal perspective,the global imbalance has been steadily increasing with the Gini index rising from 0.895 in 1985 to 0.909 in 2022.Consequently,this study reveals an increasing imbalance of global per capita cropland across various countries,which threatens the attainment of the targets of SDG 2.展开更多
Conversion of dryland to paddy fields(CDPF)is an effective way to transition from rain-fed to irrigated agricul ture,helping to mitigate the effects of climate change on agriculture and increase yields to meet growing...Conversion of dryland to paddy fields(CDPF)is an effective way to transition from rain-fed to irrigated agricul ture,helping to mitigate the effects of climate change on agriculture and increase yields to meet growing food demand.However,the suitability of CDPF is spatio-temporally dynamic but has often been neglected in previous studies.To fill this knowledge gap,this research developed a novel method for quantifying the suitability of CDPF,based on the MaxEnt model for application in Northeast China.We explored the spatiotemporal characteristics of the suitability of CDPF under the baseline scenario(2010-2020),and future projections(2030-2090)coupled with climate change and socioeconomic development scenarios(SSP126,SSP245,and SSP585),and revealed the driving factors behind it.Based on this,we identified potential priority areas for future CDPF implementation.The results show that the suitability of CDPF projects implemented in the past ten years is relatively high.Com pared with the baseline scenario,the suitability of CDPF under the future scenarios will decline overall,with the lightest decrease in the RCP585 and the most severe decrease in the RCP245.The key drivers affecting the suitability of CDPF are elevation,slope,population count,total nitrogen,soil organic carbon content,and precip itation seasonality.The potential priority areas for the future CDPF range from 6,284.61 km^(2)to 37,006.02 km^(2).These findings demonstrate the challenges of CDPF in adapting to climate change and food security,and provide insights for food-producing regions around the world facing climate crises.展开更多
Cropland abandonment has become a global issue that poses significant threats to sustainable cropland management,national food security,and the ecological environment.Remote sensing technology is crucial for identifyi...Cropland abandonment has become a global issue that poses significant threats to sustainable cropland management,national food security,and the ecological environment.Remote sensing technology is crucial for identifying and monitoring abandoned cropland in large-scale areas.However,limited information is available on the effective identification methods and spatial distribution patterns of abandoned cropland in the hilly and gully regions.This study introduced two methods-the land-use trajectory and normalized difference vegetation index(NDVI)time series-for monitoring abandoned cropland and evaluating its spatial distribution in Yanhe River Basin using Landsat-8 images from 2019 to 2021.The results showed that using a random forest algorithm,high-precision annual land-use classifications were achieved with the generation of reliable land-cover samples and an optimized feature dataset.The overall accuracy(OA)and Kappa coefficient of the land-use maps exceeded 90% and 0.88,respectively,demonstrating the effectiveness of the classification over three years.These two distinct change detection methods were used to identify abandoned cropland in the study area,and their accuracy and effectiveness were evaluated.The land-use trajectory method performed better than the NDVI time series method for extracting abandoned cropland,with an OA of 83.5% and an F1 score of 84.7%.According to the land-use trajectory detection results,the study area had 164.6 km^(2) of abandoned cropland area in 2021,with an abandonment rate of 16.3%.Furthermore,cropland abandonment mainly occurred in the northwestern part of the region,which has harsh natural conditions,while abandonment was rare in the southern and eastern regions.Topography and landforms significantly influenced the spatial distribution of abandoned cropland,with most abandoned cropland located in mountainous regions with higher elevations and steeper slopes.The abandonment rate generally increased with the elevation and slope.These findings provide valuable references and guidance for selecting appropriate methods to identify abandoned cropland and analyze its spatial distribution in the hilly and gully regions.Our proposed methods offer robust solutions for monitoring abandoned cropland and optimizing land-use change detection in similar regions with complex landforms.展开更多
基金National Natural Science Foundation of China,No.42361144881,No.42201310The Third Xinjiang Scientific Expedition Program,No.2021xjkk0900。
文摘Agricultural greenhouse gas(GHG)emissions are influenced by a combination of climate,soil and agricultural management practices.Over the past 30 years,approximately 5% of China's cropland has shifted from the south to the north.This shift has significantly altered the geographical environment,with potential substantial impacts on agricultural GHG emissions.This study used the DeNitrification DeComposition(DNDC)process-based model to simulate GHG emissions(CH_(4)and N_(2)O)from the production of China's 10 major food crops and explored changes in agricultural GHG emissions caused by the spatial shift of cropland in China.Results from the validated DNDC model indicate that total emissions from the major food crop production in China were approximately 343 Tg CO_(2)-eq yr^(-1)with CH_(4)emissions accounting for about 74%.Meanwhile,the spatial shift of cropland from 1990 to 2020 resulted in a 3% decrease in average CH_(4)emissions per unit cropland area and an 8% increase in average N_(2)O emissions per unit cropland area,respectively.The expansion of dryland in the Northwest Arid Region emitted less CH_(4)but significantly more N_(2)O,thereby driving changes in national GHG emissions.This study provides a scientific foundation for the sustainable use of cropland and the formulation of strategies to reduce agricultural GHG emissions.
文摘Croplands are decreasing due to the expansion of urban areas into rural communities and to some extent due to sand accumulations. Increases in population numbers, new development, in addition to the accumulation of sand and soil salinity are the major driving force leading to abandonment and shrinking of cropland. The aim of this study was to investigate and assess to what extent agricultural lands are affected by urban development in the Al Hassa oasis, Eastern region in Saudi Arabia by employing Landsat time series data of years 1988, 2000 and 2017 as the main source of information. A set of ground truth, control points (GCPs) was also used besides population census data. Unsupervised classifications approach, Normalized Difference Vegetation Index (NDVI) and change detection methods were used here. Urban area during 2000-2017 exhibits much higher increase compared to 1988-2000, while the arable lands declined to −3.4% in 1988-2000 and increased to 22% during 2000-2017. The data analysis results provided new accurate numerical information supported by a graphical representation in regard to the decrease and increase in urban and agricultural lands. Therefore the findings of this study should be considered by decision maker for improving and development the agriculture activities in rural and urban communities.
基金Project supported by the National Key Basic Research and Development Program of China (No. 2002CB412501), theKnowledge Innovation Key Project of Chinese Academy of Sciences (No. KZCX1-SW-01-19), and the Integrated Interdis-ciplinary Science Plan of Land-Use/Land-Cover and Terrestrial Carbon Process of Institute of Geographical Sciences andNatural Resources Research (No. CXIOG-E01-02-02).
文摘The soil organic carbon (SOC) pool is the largest component of terrestrial carbon pools. With the construction of a geographically referenced database taken from the second national general soil survey materials and based on 1546 typical cropland soil profiles, the paddy field and dryland SOC storage among six regions of China were systematically quantified to characterize the spatial pattern of cropland SOC storage in China and to examine the relationship between mean annual temperature, precipitation, soil texture features and SOC content. In all regions, paddy soils had higher SOC storage than dryland soils, and cropland SOC content was the highest in Southwest China. Climate controlled the spatial distribution of SOC in both paddy and dryland soils, with SOC storage increasing with increasing precipitation and decreasing with increasing temperature.
基金supported by a bilateral scientific cooperation project financed by UGent-BOF, Belgiumand the Ministry of Science and Technology, China(2005-2)the Non-Profit Research Foundation for Agriculture of China (200803036)
文摘Soil organic carbon （SOC） is one of the centre issues related to not only soil fertility but also environmental safety. Assessing SOC dynamics in croplands has been a challenge in China for long due to the lack of appropriate methodologies and data sources. As an alternative approach for studying SOC dynamics, process-based models are adopted to meet the needs. In this paper, a process-based model, DeNitrification-DeComposition （DNDC）, was applied to quantify the SOC storage and the spatial distribution in croplands of China in 2003, with the support of a newly compiled county-level soil/ climate/land use database. The simulated results showed that the total SOC storage in the top layer （0-30 cm） of the 1.18 × 10^8 ha croplands of China is 4.7-5.2 Pg C in 2003 with an average value of 4.95 Pg C. The SOC storage in the northeastern provinces （1.3 Pg C） accounts for about 1/4 of the whole national totals due to their dominantly fertile soils with high organic matter content. SOC density ranges from 3.9 to 4.4 kg C m 2, with an average of 4.2 kg C m^-2, a level is much lower than the world average level. The model results also indicated that high rates of SOC losses occurred in the croplands with the most common cropping patterns in China as like single soybean 〉 maize 〉 paddy 〉 cotton 〉 winter wheat and corn rotation. The results reported in this paper showed that there was still a great potential for improving SOC status in most croplands of China by adopting proper farming practices and land-use pattern. Therefore, long-term policy to protect SOC is urgently needed.
基金supports from the National Natural Science Foundation of China (41522207, 41571130042, 31572191 and 31772387)the National Key R&D Program of China (2016YFA0601002)
文摘Crop harvesting and residue removal from croplands often result in imbalanced biogeochemical cycles of carbon and nutrients in croplands, putting forward an austere challenge to sustainable agricultural production. As a beneficial element, silicon（Si） has multiple eco-physiological functions, which could help crops to acclimatize their unfavorable habitats. Although many studies have reported that the application of Si can alleviate multiple abiotic and biotic stresses and increase biomass accumulation, the effects of Si on carbon immobilization and nutrients uptake into plants in croplands have not yet been explored. This review focused on Si-associated regulation of plant carbon accumulation, lignin biosynthesis, and nutrients uptake, which are important for biogeochemical cycles of carbon and nutrients in croplands. The tradeoff analysis indicates that the supply of bioavailable Si can enhance plant net photosynthetic rate and biomass carbon production（especially root biomass input to soil organic carbon pool）, but reduce shoot lignin biosynthesis. Besides, the application of Si could improve uptake of most nutrients under deficient conditions, but restricts excess uptake when they are supplied in surplus amounts. Nevertheless, Si application to crops may enhance the uptake of nitrogen and iron when they are supplied in deficient to luxurious amounts, while potassium uptake enhanced by Si application is often involved in alleviating salt stress and inhibiting excess sodium uptake in plants. More importantly, the amount of Si accumulated in plant positively correlates with nutrients release during the decay of crop biomass, but negatively correlates with straw decomposability due to the reduced lignin synthesis. The Si-mediated plant growth and litter decomposition collectively suggest that Si cycling in croplands plays important roles in biogeochemical cycles of carbon and nutrients. Hence, scientific Si management in croplands will be helpful for maintaining sustainable development of agriculture.
基金The research was funded by Innovation Capability Support Program of Shaanxi(2019TD-040)China National Natural Science Foundation(41472228,41877199)+1 种基金Groundwater and Ecology Security in the North Slope Economic Belt of the Tianshan Mountain(201511047)Key Laboratory of Groundwater and Ecology in Arid Regions of China Geological Survey.
文摘Regional aridity is increasing under global climate change,and therefore the sustainable use of water resources has drawn attention from scientists and the public.Land-use changes can have a significant impact on groundwater recharge in arid regions,and quantitative assessment of the impact is key to sustainable groundwater resources management.In this study,the changes of groundwater recharge after the conversion of natural lands to croplands were investigated and compared in inland and arid region,i.e.,the northern slope of the Tianshan Mountain.Stable isotopes suggest that soil water in topsoil(<2 m)has experienced stronger evaporation under natural lands than croplands,and then moves downward as a piston flow.Recharge was estimated by the tracer-based mass balance method,i.e.,chloride and sulfate.Recharge rates under natural conditions estimated by the chloride mass balance(CMB)method were estimated to be 0.07 mm/a in deserts and 0.4 mm/a in oases.In contrast,the estimated groundwater recharge ranged from 61.2 mm/a to 44.8 mm/a in croplands,indicating that groundwater recharge would increase significantly after land changes from natural lands to irrigated croplands in arid regions.Recharge estimated by the sulfate mass balance method is consistent with that from the CMB method,indicating that sulfate is also a good tracer capable of estimating groundwater recharge.
基金Under the auspices of Key Deployment Project of Chinese Academy of Sciences(No.KZZD-EW-08-02)
文摘Studies on long-term change of cropland is of great significance to the utilization of land resources and the implementation of scientific agricultural policies. The Korean Peninsula, adjacent to China, plays an important role in the international environment of Northeast Asia. The Korean Peninsula includes South Korea and North Korea—two countries that have a great difference in their institutions and economic developments. Therefore, we aim to quantify the spatiotemporal changes of croplands in these two countries using Landsat Thematic Imager(TM) and Operational Land Imager(OLI) imagery, and to compare the differences of cropland changes between the two countries. This paper take full advantage of ODM approach(object-oriented segmentation and decision-tree classification based on multi-season imageries) to obtain the distribution of croplands in 1990 and 2015. Results showed that the overall classification accuracy of cropland data is 91.10% in 1990 and 92.52% in 2015. The croplands were mainly distributed in areas with slopes that were less than 8° and with elevations that were less than 300 m in the Korean Peninsula. However, in other region(slope > 8° or elevation > 300 m), the area and proportion of North Korea's croplands were significantly higher than that of South Korea. Croplands significantly increased by 15.02% in North Korea from 1990 to 2015. In contrast, croplands in South Korea slightly decreased by 1.32%. During the 25 years, policy shift, economic development, population growth, and urban sprawl played primary roles for cropland changes. Additionally, the regional differences of cropland changes were mainly due to different agriculture policies implemented by different countries. The achievements of this study can provide scientific guidance for the protection and sustainability of land resources.
文摘Mount Kilimanjaro and the Taita Hills are adjacent montane areas that experience similar climate and agricultural activity, but which differ in their geologic history, nature of elevation gradients and cultures. We assessed differences in cropland above ground carbon (AGC) between the two sites and against environmental variables. One hectare sampling plots were randomly distributed along elevational gradients stratified by cropland type;AGC was derived from all trees with diameter ≥ 10 cm at breast height in each plot. Predictor variables were physical and edaphic variables and human population. A generalized linear model was used for predicting AGC with AIC used for ranking models. AGC was spatially upscaled in 2 km buffer and visually compared. Kilimanjaro has higher AGC in cropped and agroforestry areas than the Taita Hills, but only significant difference in AGC variation in agroforestry areas (F = 9.36, p = 0.03). AGC in cropped land and agroforestry in Kilimanjaro has significant difference on mean (t = 4.62, p = 0.001) and variation (F = 17.41, p = 0.007). In the Taita Hills, significant difference is observed only on the mean AGC (t = 4.86, p = 0.001). Common tree species that contribute the most to AGC in Kilimanjaro are Albizia gummifera and Persea americana, and in the Taita Hills Grevillea robusta and Mangifera indica. Significant and univariate predictors of AGC in Mount Kilimanjaro are pH (R2 = 0.80, p = 0.00) and EVI (R2 = 0.68, p = 0.00). On Mount Kilimanjaro, the top multivariate model contained SOC, CEC, pH and BLD (R2 = 0.90, p = 0.00), whereas in the Taita Hills, the top multivariate model contained elevation, slope and population (R2 = 0.89, p = 0.00). Despite of the difference in land management history of Mount Kilimanjaro and the Taita Hills, mean of AGC in croplands does not differ significantly. Difference occurs on variation of AGC, type of trees contributing AGC, and environmental variables that explain AGC distribution. The research results provide reference for management of carbon sequestration on inhabited montane areas.
基金the Agritech National Research Center supported by European Union Next-Generation EU(PIANO NAZIONALE DI RIPRESA E RESILIENZA(PNRR)-MIS-SIONE 4 COMPONENTE 2,INVESTIMENTO 1.4-D.D.103217/06/2022,CN00000022)The China Scholarship Council。
文摘Climate change and the increasing frequency of floods have undermined China’s food security.Creating detailed maps of flooded croplands is essential to improve prevention and adopt effective adaptation initiatives.Previous large-scale flood mapping efforts were hampered by limited meteorological and hydrological data,and the susceptibility of optical satellite images to cloud cover,leading to high uncertainty when downscaled to the cropland-scale.Here,using 4968 near-real-time(NRT)Sentinel-1 SAR(S1)images(spatial resolution:10 m),we generated China’s first set of high-resolution flooded cropland maps covering the period from 2017 to 2021.Our results demonstrate that croplands accounted for 43.8%to49.8%of China’s total flooded areas(ranging from 82,175 km^(2) to 122,037 km^(2)).We also created highresolution flood maps specifically for rice and maize crops.The inundated rice areas ranged from 8428 km^(2) to 22,123 km^(2),accounting for 22.34%to 41.91%of the annual flooded croplands,or 2.82%to7.45%of the annual rice cropland.In comparison,the inundated maize cropland fluctuated from 2619 km^(2) to 5397 km^(2),representing 5.38%to 13.56%of the annual flooded croplands.Our findings revealed extensive floods in rural areas,highlighting the urgent need to prioritize flood prevention and mitigation efforts in such regions.In light of China’s allocation of an additional 1-trillion-RMB treasury bonds for water infrastructure projects,the high-resolution flood maps can be used to select sites for flood control projects,and evaluate the impact of flooding on crop yields and food security,thus targeting poverty alleviation in rural areas of China.
基金supported by the National Natural Science Foundation of China(42371260&42101293)the National Key Research and Development Program of China on Global Change(2017YFA0603304)。
文摘Reconstructing Canada's cropland over the past millennium reveals human-land relationships and informs strategies for climate change mitigation.Canada's population and per capita cropland area are estimated for 1000–1840 by analyzing and revising historical documents.These estimates are then multiplied and combined with census data to obtain the cropland area of Canada for 1000–2015.Then,using a sophisticated land suitability map for cultivation,a cropland area allocation model is constructed,and the spatial pattern of cropland in Canada for the past millennium is mapped using the model and the maximum extent of cropland in different periods.The results indicated that the cropland area increased from 0.078 million ha in 1000 to38.690 million ha in 2015,with slow growth before 1900 and rapid growth thereafter.The spatial distribution of cropland in Canada expands gradually from the Great Lakes-St.Lawrence Lowlands to the western prairie area,with land use intensity increasing and exhibiting spatial heterogeneity over the past millennium.This high-resolution,spatially explicit reconstruction aligns more closely with Canada's agricultural history than several noteworthy global datasets.Archaeological data are needed to enhance subsequent land use estimation and mapping for Canada.
基金This work was supported by NASA MEaSUREs(grant number NNH13AV82I)U.S.Geological Survey provided sup-plemental funding from other direct and indirect means through its Land Change Science(LCS)Land Remote Sensing(LRS)programs as well as its Climate and Land Use Change Mission Area.
文摘Mapping croplands,including fallow areas,are an important measure to determine the quantity of food that is produced,where they are produced,and when they are produced(e.g.seasonality).Furthermore,croplands are known as water guzzlers by consuming anywhere between 70%and 90%of all human water use globally.Given these facts and the increase in global population to nearly 10 billion by the year 2050,the need for routine,rapid,and automated cropland mapping year-after-year and/or season-after-season is of great importance.The overarching goal of this study was to generate standard and routine cropland products,year-after-year,over very large areas through the use of two novel methods:(a)quantitative spectral matching techniques(QSMTs)applied at continental level and(b)rule-based Automated Cropland Classification Algorithm(ACCA)with the ability to hind-cast,now-cast,and future-cast.Australia was chosen for the study given its extensive croplands,rich history of agriculture,and yet nonexistent routine yearly generated cropland products using multi-temporal remote sensing.This research produced three distinct cropland products using Moderate Resolution Imaging Spectroradiometer(MODIS)250-m normalized difference vegetation index 16-day composite time-series data for 16 years:2000 through 2015.The products consisted of:(1)cropland extent/areas versus cropland fallow areas,(2)irrigated versus rainfed croplands,and(3)cropping intensities:single,double,and continuous cropping.An accurate reference cropland product(RCP)for the year 2014(RCP2014)produced using QSMT was used as a knowledge base to train and develop the ACCA algorithm that was then applied to the MODIS time-series data for the years 2000–2015.A comparison between the ACCA-derived cropland products(ACPs)for the year 2014(ACP2014)versus RCP2014 provided an overall agreement of 89.4%(kappa=0.814)with six classes:(a)producer’s accuracies varying between 72%and 90%and(b)user’s accuracies varying between 79%and 90%.ACPs for the individual years 2000–2013 and 2015(ACP2000–ACP2013,ACP2015)showed very strong similarities with several other studies.The extent and vigor of the Australian croplands versus cropland fallows were accurately captured by the ACCA algorithm for the years 2000–2015,thus highlighting the value of the study in food security analysis.
基金This research was financially supported by the National Natural Science Foundation of China(Nos.41771505,41571480,and 41706119)the Project of Changchun Science and Technology Plan(No.19SS019).
文摘Ecological stoichiometry is an important indicator presenting multiple elements balance in agro-ecosystems.However,information on microbial communities and nutrient stoichiometry in soil aggregate fractions under different croplands(rice,maize,and soybean fields)remains limited.Thus,this study investigated water-stable aggregate structure and their internal nutrient stoichiometry under different croplands and ascertain their interaction mechanism with microbial communities.The results showed that no significant difference on the carbon-to-nitrogen ratio(C:N)in soil aggregate fractions was observed,while the carbon-to-phosphorus ratio(C:P)and the nitrogen-to-phosphorus ratio(N:P)were ranked as rice field>maize field>soybean field,and were higher in mega-aggregates(ME,>1 mm).General fatty acid methyl ester(FAME),Gram-positive bacteria(G+),and Gramnegative bacteria(G−)were predominant microbial communities in all croplands and tented to condense into coarse-aggregates.Redundancy analysis(RDA)demonstrated that N:P ratio was primary environmental controls on the distribution of soil microorganisms.In the Sanjiang Plain,N was the nutrient element limiting agro-ecosystem productivity,and rice cultivation is expected to improve the N-limited nutrient status.
基金the National Natural Science Foundation of China (Grant Nos. 39893360 and 30270241)the Chinese Ministry of Education (Grant No. 272007)
文摘In the study area (Yanjiaping Village, Hebei Province, China), grazing extensity varies at different loca-tions, small and discontinuous croplands are imbedded in some arid grassland, which are habitats for the melitaeine butterflies, Euphydryas aurinia and Melitaea phoebe. These two species of butterflies coexist in this area, in which grazing and cultivation are the main disturbances. Grazing and cultivation have a reciprocal effect on E. aurinia, rather than M. phoebe. We observed that E. aurinia preferred to occupy patches with moderate grazing and imbedded with small and discontinuous croplands, where E. aurinia also has high population density. The percentage of E. aurinia larval groups in the ribbings was significantly higher than that of M. phoebe, whereas larvae of both species tended to increase in recent years. Our data also showed that the population density and the patch occupancy rate of both E. aurinia and M. phoebe were the highest under moderate grazing. It indicates that cultivation of small and dis-continuous croplands within the patch has a significant effect on the population density of both spe-cies of melitaeine butterflies. Thus, to artificially create or maintain semi-natural habitats, comple-mented by moderate grazing, might be an ecological strategy to conserve melitaeine butterflies effec-tively. Considering the distinct impacts of cultivation and grazing on the population distribution and dynamics of the two different species, human disturbance in the mountainous area might be strategi-cally involved in proposing conservation plans for the target species in the future.
基金supported by the National Key Research and Development Program of China (2023YFD1902703)the National Natural Science Foundation of China (Key Program) (U23A20158)。
文摘Cropland nitrate leaching is the major nitrogen(N) loss pathway, and it contributes significantly to water pollution. However, cropland nitrate leaching estimates show great uncertainty due to variations in input datasets and estimation methods. Here, we presented a re-evaluation of Chinese cropland nitrate leaching, and identified and quantified the sources of uncertainty by integrating three cropland area datasets, three N input datasets, and three estimation methods. The results revealed that nitrate leaching from Chinese cropland averaged 6.7±0.6 Tg N yr^(-1)in 2010, ranging from 2.9 to 15.8 Tg N yr^(-1)across 27 different estimates. The primary contributor to the uncertainty was the estimation method, accounting for 45.1%, followed by the interaction of N input dataset and estimation method at 24.4%. The results of this study emphasize the need for adopting a robust estimation method and improving the compatibility between the estimation method and N input dataset to effectively reduce uncertainty. This analysis provides valuable insights for accurately estimating cropland nitrate leaching and contributes to ongoing efforts that address water pollution concerns.
基金The Second Tibetan Plateau Scientific Expedition and Research ProgramNo.2019QZKK0406。
文摘Cropland suitability analysis is a vital tool for ensuring food security and sustainable agriculture,coordinating ecological space with human activity space on the Qinghai-Tibet Plateau(QTP).However,there are few studies on complete and accurate cropland suitability assessments on the QTP,let alone on identifying key potential areas for cropland development.We used a novel assessment model to generate a 30-m cropland suitability map for the QTP.The identification of areas with cropland development potential and the evaluation of potentially available cropland were further integrated into a unified analytical framework.We found that only 10.18%of the study area is suitable for large-scale and permanent cropland.Moreover,approximately 72.75%of the existing cropland was found to be distributed in suitable or marginally suitable areas.Considering the trade-offs related to irrigation water supply convenience,approximately 1.07%of the study area was identified as having high potential for cropland development.Four key potential areas were further identified:the Shannan Valley,the Nyingchi Valley,the Zanda Valley,and the Gonghe Basin.These areas boast abundant potentially available cropland resources and ecological resettlement capacities,which leads us to recommend strategic priorities for comprehensive land consolidation and water development.This study has practical significance for optimizing land resource allocation and guiding decision-making related to ecological migration on the QTP.
基金supported by the National Natural Science Foundation of China[Grant No.42201232]the Science and Technology Research Project of Jiangxi Provincial Department of Education[Grant No.GJJ210539].
文摘Cropland abandonment is prevalent throughout China,particularly in mountainous regions.However,the varying degrees of land marginalization and the specific factors influencing different types of cropland remain insufficiently understood.This knowledge gap hampers targeted management strategies for mitigating cropland abandonment in these areas.This study used spatial analysis,logistic regression,and random forest models to explore the spatial patterns and key drivers of abandonment across flatland,terrace,and slopeland in Chongyi county,a mountainous region in Jiangxi Province of South China,utilizing data from the 2009 and 2019 national land surveys of China.Results showed that the overall cropland abandonment rate in Chongyi county was 36.46%,with particularly high rates in core terrace conservation areas.Abandoned cropland was spatially clustered,predominantly in high-elevation regions.The abandonment rates were 9.71%for flatland,37.52%for terrace,and 43.02%for slopeland.Variations in vegetation cover on abandoned cropland suggest that abandonment started earlier on slopeland and later extended to terraces and flatlands.The factors driving the abandonment of flatland,terrace,and slopeland included land altitude,cultivation height difference,and distance to forest land,respectively.Consequently,the results recommend implementing land consolidation and developing small machinery projects for the fragmented flatland.Promoting the multifunctional use of terraces could realize their ecological value.Additionally,the Program of Converting Farmland to Forest should be implemented on the low-quality slopeland.
基金supported by the National Key Research and Development Program of China(2023YFD2300501)the National Natural Science Foundation of China(41921001 and 42401440)。
文摘In many existing dictionaries,cropland is defined as land that is suitable for or used to grow crops.It has several synonyms,such as“farmland”,“arable land”,and“cultivated land”.However,in scientific literature,the nuances of these terms are often overlooked.The inconsistent terminology usage could lead to ambiguity and confusion in research and policy discussions.In particular,it creates difficulties for newcomers and students when they search for precise information in the published literature.Hence,exploring the variations of terminology applications is important for the cropland-related research community.In this study,the differences in six cropland-related terminologies were explored through a review of 5,214 scientific articles,by employing the independence test,clustering approach,and correlation analysis.The results showed that disparities exist across disciplines.For example,biodiversity&conservation studies preferentially use“farmland”to highlight effects from human activities,while studies in geology and computer science use“cropland”.The term“cultivated land”tends to be used in geography research for clear geographical demarcation,while“arable land”is related to engineering studies.Moreover,further disparities based on the geographical affiliations of the authors were found.The correlation between China and“cultivated land”was reliable and a close link was found between“agricultural land”and the USA.The regional variations in cropland terminology can be influenced by multiple factors,including the degree of agricultural mechanization,colonial history,and migration patterns.This study reveals variations in cropland-related terminology across disciplines and regions.The results highlight the importance of standardizing cropland terminology to foster interdisciplinary research,improve data comparability,and support global agricultural and environmental policymaking.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFB3907403)the National Natural Science Foundation of China(Grant No.42201499)the Open Research Program of the International Research Center of Big Data for Sustainable Development Goals(Grant No.CBAS2022ORP03).
文摘Sustainable Development Goal 2(SDG 2,zero hunger)highlights that global hunger and food insecurity have worsened since 2015,driven in part by growing imbalance.Addressing the challenge of achieving SDG 2 in the face of rapid global population growth requires sustained attention to global and national cropland changes.Accurately quantifying the correlation between population and cropland area(i.e.,SDG 2.4.1 per capita cropland)and analyzing the trends of global cropland imbalance are essential for a comprehensive understanding of SDG 2.In this study,we utilized a new global 30 m land-cover dynamic dataset(GLC_FCS30D)to analyze cropland dynamics,quantify per capita cropland and its changes across various countries and levels of development.Our results indicate that the global cropland area expanded by 0.944 million km^(2)from 1985 to 2022,with an average expansion rate of 2.42×10^(4)km^(2)/yr.However,the global per capita cropland area decreased from 0.347 ha in 1985 to 0.217 ha in 2022,mainly due to a higher population increase of nearly 65%in the same period.In the context of globalization,cropland expansion and per capita cropland exhibited spatial imbalances globally,particularly in developing countries.Developing countries saw an increase in total cropland area by 7.09%but a significant decrease in per capita cropland area by 37.38%.From a temporal perspective,the global imbalance has been steadily increasing with the Gini index rising from 0.895 in 1985 to 0.909 in 2022.Consequently,this study reveals an increasing imbalance of global per capita cropland across various countries,which threatens the attainment of the targets of SDG 2.
基金supported by the Ministry of Education of Human-ities and Social Science project,China(Grant No.21YJA630121)the National Key Technology R&D Program of Ministry of Science and Technology of China(Grant No.2023YFD1500103)+2 种基金the Tsinghua Rural Studies PhD Scholarship(Grant No.202323)2023 Gradu-ate Innovation Fund Project of China University of Geosciences,Beijing(Grant No.ZD2023YC043)National Social Science Fund of China(Grants No.19ZDA096 and 20&ZD090)。
文摘Conversion of dryland to paddy fields(CDPF)is an effective way to transition from rain-fed to irrigated agricul ture,helping to mitigate the effects of climate change on agriculture and increase yields to meet growing food demand.However,the suitability of CDPF is spatio-temporally dynamic but has often been neglected in previous studies.To fill this knowledge gap,this research developed a novel method for quantifying the suitability of CDPF,based on the MaxEnt model for application in Northeast China.We explored the spatiotemporal characteristics of the suitability of CDPF under the baseline scenario(2010-2020),and future projections(2030-2090)coupled with climate change and socioeconomic development scenarios(SSP126,SSP245,and SSP585),and revealed the driving factors behind it.Based on this,we identified potential priority areas for future CDPF implementation.The results show that the suitability of CDPF projects implemented in the past ten years is relatively high.Com pared with the baseline scenario,the suitability of CDPF under the future scenarios will decline overall,with the lightest decrease in the RCP585 and the most severe decrease in the RCP245.The key drivers affecting the suitability of CDPF are elevation,slope,population count,total nitrogen,soil organic carbon content,and precip itation seasonality.The potential priority areas for the future CDPF range from 6,284.61 km^(2)to 37,006.02 km^(2).These findings demonstrate the challenges of CDPF in adapting to climate change and food security,and provide insights for food-producing regions around the world facing climate crises.
基金supported by the National Key R&D Program of China(2023YFD1900300)the State Administration of Foreign Experts Affairs of China(B12007)+1 种基金the 111 Project of Chinathe support by the China Scholarship Council(202306300092).
文摘Cropland abandonment has become a global issue that poses significant threats to sustainable cropland management,national food security,and the ecological environment.Remote sensing technology is crucial for identifying and monitoring abandoned cropland in large-scale areas.However,limited information is available on the effective identification methods and spatial distribution patterns of abandoned cropland in the hilly and gully regions.This study introduced two methods-the land-use trajectory and normalized difference vegetation index(NDVI)time series-for monitoring abandoned cropland and evaluating its spatial distribution in Yanhe River Basin using Landsat-8 images from 2019 to 2021.The results showed that using a random forest algorithm,high-precision annual land-use classifications were achieved with the generation of reliable land-cover samples and an optimized feature dataset.The overall accuracy(OA)and Kappa coefficient of the land-use maps exceeded 90% and 0.88,respectively,demonstrating the effectiveness of the classification over three years.These two distinct change detection methods were used to identify abandoned cropland in the study area,and their accuracy and effectiveness were evaluated.The land-use trajectory method performed better than the NDVI time series method for extracting abandoned cropland,with an OA of 83.5% and an F1 score of 84.7%.According to the land-use trajectory detection results,the study area had 164.6 km^(2) of abandoned cropland area in 2021,with an abandonment rate of 16.3%.Furthermore,cropland abandonment mainly occurred in the northwestern part of the region,which has harsh natural conditions,while abandonment was rare in the southern and eastern regions.Topography and landforms significantly influenced the spatial distribution of abandoned cropland,with most abandoned cropland located in mountainous regions with higher elevations and steeper slopes.The abandonment rate generally increased with the elevation and slope.These findings provide valuable references and guidance for selecting appropriate methods to identify abandoned cropland and analyze its spatial distribution in the hilly and gully regions.Our proposed methods offer robust solutions for monitoring abandoned cropland and optimizing land-use change detection in similar regions with complex landforms.
