An examination of thematic research,development,and trends in remote sensing applied to conservation agriculture

Conservation agriculture seeks to reduce environmental degradation through sustainable management of agricultural land.Since the 1990s,agricultural research has been conducted using remote sensing technologies;however,few previous reviews have been conducted focused on different conservation management practices.Most of the previous literature has focused on the application of remote sensing in agriculture without focusing exclusively on conservation practices,with some only providing a narrative review,others using biophysical remote sensing for quantitative estimates of the bio-geo-chemical-physical properties of soils and crops,and few others focused on single agricultural management practices.This paper used the preferred reporting items for systematic review(PRISMA)methodology to examine the last 30 years of thematic research,development,and trends associated with remote sensing technologies and methods applied to conservation agriculture research at various spatial and temporal scales.A set of predefined key concepts and keywords were applied in three databases:Scopus,Web of Science,and Google Scholar.A total of 188 articles were compiled for initial examination,where 68 articles were selected for final analysis and grouped into cover crops,crop residue,crop rotation,mulching,and tillage practices.Publications on conservation agriculture research using remote sensing have been increasing since 1991 and peaked at 10 publications in 2020.Among the 68 articles,94%used a pixel-based,while only 6%used an object-based classification method.Prior to 2005,tillage practices were abundantly studied,then crop residue was a focused theme between 2004 and 2012.From 2012 to 2020,the focus shifted again to cover crops.Ten spectral indices were used in 76%of the 68 studies.This examination offered a summary of the new potential and identifies crucial future research needs and directions that could improve the contribution of remote sensing to the provision of long-term operational services for various conservation agriculture applications.

Towards accurate mapping of loess waterworn gully by integrating google earth imagery and DEM using deep learning

Accurate mapping of loess waterworn gully(LWG)is essential to further study gully erosion and geomorphological evolution for the Chinese Loess Plateau(CLP).Due to the vertical joint and collapsibility of loess,LWGs have the characteristics of zigzag and unique slope abruptness under synthetic action of hydraulic force and gravity.This forces existing LWG mapping methods to either focus on the improvement of mapping accuracy or center on the increase of mapping efficiency.However,simultaneously achieving accurate and efficient mapping of LWG is still in its infancy under complex topographic conditions.Here,we proposed a method that innovatively integrates the loess slope abruptness feature into an improved deep learning semantic segmentation framework for LWG mapping using 0.6 m Google imagery and 5 m DEM data.We selected four study areas representing typical loess landforms to test the performance of our method.The proposed method can achieve satisfactory mapping results,with the F1 score,mean Intersection-over-Union(mIoU),and overall accuracy of 90.5%,85.3%,and 92.3%,respectively.In addition,the proposed model also showed significant accuracy improvement by inputting additional topographic information(especially the slope of slope).Compared with existing algorithms(Random forests,original DeepLabV3+,and Unet),the proposed approach in this study achieved a better accuracy-efficiency trade-off.Overall,the method can ensure high accuracy and efficiency of the LWG mapping for different loess landform types and can be extended to study various loess gully mapping and water and soil conservation.

Runoff and Infiltration responses of revegetated slopes to clipping management on the northern Loess Plateau

Large-scale vegetation restoration can reduce local watershed water yield,limit vegetation establishment and subsequent growth,and influence regional ecosystem functions.Clipping management by reducing aboveground parts of grassland was gradually recommended and adopted in Grain-for-Green project management to offset these additional issues.Thus,scientific evaluation of the effectiveness of clipping management on infiltration and runoff processes is necessary for maintaining the stability of the surface water system and the sustainability of vegetation restoration in semi-arid regions.A field simulated rainfall experiment was conducted with four managed clipping grasslands(mainly bunge needlegrass and Stipa grandis),including no clipping,light clipping,heavy clipping,and complete clipping under three slope gradients(10,20,and 30°)and three rainfall intensities(60,90,and 120 mm/h)to explore the mechanism of runoff and infiltration responses to clipping using structural equation modeling and variation partitioning based on an SCS-CN model.The results showed the runoff coefficient of the light clipping,heavy clipping,and complete clipping plots were 1.33,2.22,and 4.22 times that of the no clipping plot.The light clipping,heavy clipping,and complete clipping plots decreased the infiltration coefficients by 0%,5%,and 26%relative to the no clipping plot.Rainfall intensity dominated runoff and infiltration amounts,and clipping intensity's total effect was stronger than slope gradient.Clipping intensity and slope gradient were more influential on runoff with increasing rainfall intensity.The mutual inhibition effect was between clipping intensity and slope gradient on runoff.In order to maintain the sustainability of restoration,a 25-50%vegetation coverage after clipping maximizes the benefits of increasing runoff and maintaining enough soil water supply that prevents possible soil drought.We propose that future vegetation restoration policies should evaluate the appropriate clipping intensity;meanwhile,local physiographic and climate conditions should be considered.These findings may offer guidance for the development of measures for runoff regulation and ecosystem functions of the watershed during vegetation restoration on the northern Loess Plateau.

Assessing gully erosion and rehabilitation using multi temporal LiDAR DEMs:Case study from the Great Barrier Reef catchments,Australia

Millions of dollars are being spent on gully rehabilitation to help reduce excess fine sediment delivery to the Great Barrier Reef(GBR).There is an urgent need for(i)prioritisation of active gullies for rehabilitation and(ii)the development of methodologies to inform the effectiveness of remediation.In this study we analyse DEMs of Difference derived from 0.5 m resolution 2-3 year interval multi-temporal LiDAR data collected pre and post rehabilitation at three variable gully morphologies in the Burdekin catchment.Our analysis indicates that the highest annual average fine sediment erosion rates for the untreated control gullies occur at the linear gully(53.38 t ha^(-1)y^(-1))followed by linear-alluvial gully(34.24 t ha^(-1)y^(-1))and least at the alluvial gully(14.41 t ha^(-1)y^(-1)).The proportional loss or export of fine sediment from the gullies in their un-treated condition ranges from∼68 to 90%of what is eroded,and when the gullies are treated the proportion of fine sediment that is retained in the gully proportional to what is eroded increases to∼60%at all sites.Without pre-treatment baseline erosion rates,and additional post treatment LiDAR captures,it is difficult to quantify the treatment effectiveness.Our results offer insights in the erosion mechanisms within different geomorphic gully morphologies and rehabilitation effects in these erosional landforms.This study provides crucial knowledge of gully dynamics that can be coupled with other lines of evidence for better prioritisation of rehabilitation in the GBR catchments.

Soil type and wetting intensity control the enhancement extent of N_(2)O efflux in soil with drought and rewetting cycles

Climate change alters the intensity and frequency of drought and rewetting(D/W)events;however,the influence patterns of D/W on soil N_(2)O efflux in the water-limited area were not fully understood.Therefore,the impacts of D/W cycles varying in different extent of rewetting and frequency to N_(2)O efflux in two kinds of soil on the Loess Plateau were investigated.The incubation conditions consisted of 1)D/W treatments with four 7-day cycles from 10%water holding capacity(WHC)to 60%WHC or 90%WHC,2)constant moisture of 60%WHC and 90%WHC.The pulse of N_(2)O efflux rate under 10-60%WHC treatment was higher than that under 10-90%WHC treatment in calcic cambisols,while opposite trend was observed in earth-cumuli-orthic anthrosols.Meanwhile,the pulse of N_(2)O efflux rate decreased as cycle number increased for different wetting intensities and soil types.The direct N_(2)O efflux under 10-60%WHC and 10-90%WHC treatments were 5.49 and 1.89μg N_(2)O-N g^(-1)soil in calcic cambisols,with those being 1.92 and 10.85μg N_(2)O-N g^(-1)soil in earth-cumuli-orthic anthrosols,respectively.The N loss in earth-cumuli-orthic anthrosols was approximately 5.74 times greater than that in calcic cambisols under 10-90%WHC treatment,whereas the N loss under 10-60%WHC treatment was about 2.86 times greater in calcic cambisols than that in earth-cumuli-orthic anthrosols.This study suggested that extreme rainfall events can enhance the N_(2)O efflux and N loss in agricultural soils on the Loess Plateau in terms of soil type and wetting intensity,which should not be ignored in the N fertilizer management.

Simulated rainfall in Brazil:An alternative for assesment of soil surface processes and an opportunity for technological development

Rainfall simulators(RS)have been used,above all,to evaluate hydrological processes related to soil water infiltration,surface runoff and soil erosion.They allow repeatability of rain application with different precipitation intensities in field and/or laboratory conditions and should produce events with physical characteristics similar to natural rain.In this manuscript,we carried out a bibliometric and scientometric analysis of studies with simulated rainfall in Brazil to assess the temporal evolution of publications,the main topics addressed and the degree of technological development of the equipment.We searched for the terms“rainfall simulator”OR“simulated rainfall”AND“Brazil”in the Scopus,Web of Science,SciELO and Google Scholar databases.We found 143 articles published in the last 37 years(1985-2022).Our findings indicate that the main research areas covered in papers are soil erosion(57.34%),soil water infiltration(24.47%),nutrient losses(9.8%)and RS development and calibration/assessment(8.39%).In recent years,the number of published papers in international high-impact factor journals has increased.Most of the papers(49.65%)refer to studies carried out by institutions located in the south and southeast regions of Brazil.Moreover,there is a large gap of studies on simulated rainfall in other regions of Brazil,where important biomes such as the Cerrado,Amazon,Caatinga,and their transitions are located.This study informs research priorities on soil erosion under simulated rainfall and provides a bibliographic database that can assist in more detailed future analyses.

Limited impacts of occasional tillage on dry aggregate size distribution and soil carbon and nitrogen fractions in semi-arid drylands

Tillage management that minimizes the frequency and intensity of soil disturbance can increase soil carbon(C)and nitrogen(N)sequestration and improve the resilience of dryland cropping systems,yet the impact of occasional disturbance on soil aggregate formation and the soil organic carbon(SOC)storage within aggregates has not been studied well.We evaluated the effect of four tillage management practices on soil dry aggregate size distribution,aggregate-protected C and N,mineral-associated organic matter carbon(MAOM-C),particulate organic matter carbon(POM-C),and corn(Zea mays L.)and sorghum(Sorghum bicolor(L.)Moench)yields in a semi-arid dryland cropping system.Treatments included conventional tillage(CT),strip-tillage(ST),no-tillage(NT),and occasional tillage(OT)management in a corn-sorghum rotation.Soil macro-aggregates were 51-54%greater under ST,NT,and OT,while small and micro-aggregates were greater in CT.Conventional tillage reduced soil aggregate-associated C by 28-31%in macro-aggregates and 47-53%in small aggregates at 26 months(M)sampling compared to ST,NT,and OT.In clay+silt fraction,CT had 14-16%,21-26%,and 36-43%less SOC at 7,14,and 26M samplings,respectively,than ST,NT,and OT.Aggregate associated N was generally similar under ST,NT,and OT,which was greater on average than CT.Soil MOAM-C and POM-C under ST,NT,and OT were generally greater than respective SOC fractions under CT at 19 and 26 M after OT implementation.Corn and sorghum yields were similar among tillage systems in 2020,but greater under ST,NT,and OT than CT in 2021.Our results suggest that while frequent intensive tillage can lower SOC and N storage,a single stubble mulch occasional tillage after several years of NT does not lead to soil C and N losses and soil structural instability in semi-arid drylands.

Spatial distributions of soil nutrients affected by land use,topography and their interactions,in the Loess Plateau of China

Soil nutrient availability and their spatial distributions are strongly related to land use and landscape morphology.This study aims to address the knowledge gap regarding the interaction between these factors and the underlying mechanisms.We selected five land uses(grassland with Artemisia gmelinii,woodland with Robinia pseudoacacia,shrubland with Caragana korshinskii and Hippophae rhamnoides,and apple orchard with Malus pumila)and nine slope positions across hillslopes in the Loess Plateau,China,to investigate their combined effects on the contents and stocks of soil organic carbon(SOC),total nitrogen(TN)and total phosphorus(TP).Parametric and non-parametric statistical tests were conducted to determine the significant differences in the means or the medians of the soil nutrient variables.Results showed that the SOC and TN contents of shrubland with Caragana korshinskii were statistically significantly greater than those of the grassland(p<0.05).SOC and TN contents generally decreased from the upper slope to the middle slope,and to the foot slope for the grassland,woodland and shrublands,and on the contrary,an increasing trend from the upper slope,to the middle slope,and to the foot slope was identified for the apple orchard.This study highlights that land use,slope position and their interaction have significant effects on the spatial distributions of soil nutrients.It provides essential empirical evidence for the identification of the optimal vegetation type and slope positions in land management and vegetation restoration activities.

Drainage of paddy terraces impacts structures and soil properties in the globally important agricultural heritage of Hani Paddy Terraces,China

Marginalization and abandonment of paddy terraces are widespread,but their effects on the sustainability of subsequent agricultural production are still unknown.Hani Paddy Terraces,included in Globally Important Agriculture Heritage Systems,are threatened by paddy fields drainage.Here,changes in terrace structure,the productivity of topsoil(0-20 cm),and soil water holding capacity at 0-70 cm depth were determined in a case study of Hani Paddy Terraces in Amengkong River Basin in Yuanyang County in Southwestern China,which had been converted into dryland terraces for 2-14 years.Our results showed that:(1)The degree of terrace structures degradation exhibited a U-shaped curve with increasing time since draining,with those drained for 5-9 years having the best structure;(2)Soil productivity index decreased first and then increased with time after conversion;(3)Maximum water holding capacity at 0-70 cm soil depth dramatically decreased after conversion and such trend became increasingly obvious with increasing time since conversion.Our study revealed that drainage of paddy terraces along with associated changes in crop and field management led to an increase in soil productivity,but degradation of terrace structures and a decrease in water holding capacity will inhibit restoration to paddy terraces.These findings enhance the understanding of the biophysical changes due to marginalization in paddy terraces.

Temporal variability of global potential water erosion based on an improved USLE model

Assessing spatiotemporal variation in global soil erosion is essential for identifying areas that require greater attention and management under the effects of anthropogenic activities and climate change.Soil erosion can be modelled using the universal soil loss equation(USLE),which includes rainfall erosivity(R-factor),vegetation cover(C-factor),topography(LS-factor),soil erodibility(K-factor),and management practices(P-factor).However,global soil erosion modeling faces numerous challenges,including data acquisition,calculation processes,and parameter calibration under different climatic and topographic backgrounds.Thus,we presented an improved USLE-based model using highly distributed parameters.The R-,C-,and P-factors were modified by the climate zone,country,and topography.This distributed model was applied to estimate the intensity and variations in global soil erosion from 1992 to 2015.We validated the accuracy of this model by comparing simulations with measurements from 11,439 plot years of erosion data.The results showed that i)the average global erosion rate was 5.78 t ha^(-1)year^(-1),with an increase rate of 4.26×10^(-3)t ha^(-1)year^(-1);ii)areas with significantly increasing erosion accounted for 16%of the land with water erosion,whereas those with significantly decreasing erosion accounted for 7%;and iii)areas with severe erosion included the western Ghats,Abyssinian Plateau,Brazilian Plateau,south and east of the Himalayas,and western coast of South America.Intensified erosion occurred mainly on the Amazon Plain and the northern coast of the Mediterranean.This study provides an improved water erosion prediction model and accurate information for researchers and policymakers to identify the drivers underlying changes in water erosion in different regions.

Semi-automated detection of rangeland runoff and erosion control berms using high-resolution topography data

An inventory of topographic modifications is essential to addressing their impacts on hydrological and morphological processes in human-altered watersheds.However,such inventories are generally lacking.This study presents two workflows for semi-automatic detection of linear earthen runoff and erosion control berms in rangelands using high-resolution topographic data.The workflows consist of initial object identification by applying either morphological grayscale reconstruction(MGR)or the Geomorphon(GEO)method,followed by identification refinements through filters based on objects’horizontal and vertical information.Three sites were selected within the Altar Valley,Arizona,in the southwestern United States.One site was used for developing workflows and optimizing filter thresholds,and the other two sites were used to validate workflows.The results showed that:1)The MGR-based workflow methodology could produce final precision and detection rates of up to 92%and 75%,respectively,and take less than 5 s for a 10.1 km^(2) site;2)The workflow based on the MGR method yielded greater identification accuracy than did the GEO workflow;3)Object length,orientation,and eccentricity were important characteristics for identifying earthen berms,and are sensitive to general channel flow direction and berm shape;4)Manual interrogation of topographic data and imagery can significantly improve identification precision rates.The proposed workflows will be useful for developing inventories of runoff and erosion control structures in support of sustainable rangeland management.

Towards defining soil quality of Mediterranean calcareous agricultural soils:Reference values and potential core indicator set

To avoid soil degradation,adapt to climate change and comply with the Sustainable Development goals 2030(UN General Assembly),establishing the quality/fertility of the agricultural soils of the Mediterranean region and evaluate how these evolve with time is mandatory.This enables adequate management practices to be implemented.The Mediterranean calcareous region has received little attention in this sense,in spite its soil particularities.So,24 different representative calcareous agricultural soils of the Mediterranean region,including the main management strategies of agricultural soils(rainfed and irrigated),were sampled from the island of Mallorca;and their physical,chemical and biological properties determined.The values obtained for most of the soil characteristics allowed to establish an initial approach to the reference values for the type of calcareous agricultural soils considered,and to clearly distinguish the effect of rainfed or irrigation management practices on soils properties and dynamics.Some enzyme activities were not stimulated by the irrigation conditions assayed or they were only in dry conditions,suggesting optimum enzyme activities could be obtained when alternating dry and humid soil conditions.Soil organic carbon,calcium carbonate and active lime revealed of significant importance in the collection of soils.Finally,the results obtained clearly indicate the heterogeneity of the region and its implications on the different soil characteristics.Therefore,this study could serve as a starting point to adequately establish the quality(fertility)for Mediterranean calcareous agricultural soils and their reference values by conducting further research in this region and including more type of soils.

Field experimental study on the effect of thawed depth of frozen alpine meadow soil on rill erosion by snowmelt waterflow

Soil erosion by snow or ice melt waterflow is an important type of soil erosion in many high-altitude and high-latitude regions and is further aggravated by climate warming.The snowmelt waterflow erosion process is affected by soil freeze-thaws and is highly dynamically variable.In this study,a methodology was developed to conduct in situ field experiments to investigate the effects of the thawed depth of the frozen soil profile on snowmelt waterflow erosion.The method was implemented on an alpine meadow soil slope at an altitude of 3700 m on the northeastern Tibetan Plateau.The erosion experiments involved five thawed soil depths of 0,10,30(35),50,and 80(100)mm under two snowmelt waterflow rates(3 and 5 L/min).When the topsoil was fully frozen or shallow-thawed(≤10 mm),its hydrothermal and structural properties caused a significant lag in the initiation of runoff and delayed soil erosion in the initial stage.The runoff and sediment concentration curves for fully frozen and shallow-thawed soil showed two-stage patterns characteristic of a sediment supply limited in the early stage and subject to hydrodynamic-controlled processes in the later stage.However,this effect did not exist where the thawed soil depth was greater than 30 mm.The deep-thawed cases(≥30 mm)showed normal hydrograph and sedigraph patterns similar to those of the unfrozen soil.The findings of this study are important for understanding the erosion rates of partially thawed soil and for improving erosion simulations in cold regions.

Isotopic insights on quantitative assessments of interaction of eco-hydrological processes in multi-scale karst watersheds

The dynamics of hydrological processes and the storage mechanisms of karst water resources are the most important issues in karst hydrology.The impact of environmental changes on water quantity,and the evaluation and quantification of eco-hydrological processes remain poorly addressed.In this study,high-frequency continuous monitoring in multi-scale karst watersheds in Southwest China combined the approaches of water isotopes and the hybrid single-particle lagrangian integrated trajectory(HYSPLIT)model to identify the recharge mechanisms between atmospheric vapor,rainfall,surface water,and groundwater,and to reveal the interaction of eco-hydrological processes.The dominant moisture sources in Puding(PD)County were the Indian Ocean(43-69%)and local moisture(24-33%).Theδ^(18)O and deuterium excess(d-excess)values showed a positive correlation indicating that secondary or sub-cloud evaporation was prominent in the wet seasons.Karst water line-conditioned excess(lc-excess)indicated that karst water interacted with recent precipitation,groundwater,and evaporation across seasons.Owing to its specific hydrogeological structure,surface water and rainwater have a higher contribution rate to groundwater replenishment.The Chenqi stream replenished the Houzhai River mainly in the form of groundwater,with percentages ranging from 38.1 to 93.5%in the wet season,and 47.8-80.1%in the dry season.In the Houzhai outlet,surface water and groundwater interconverted frequently with a percentage of 45.6-49.1%.We believe this is the first systematic study to quantify the supply relationship between water vapor transport,rainfall,surface water and groundwater in the Chinese karst zone,making a significant move forward in the field of karst hydrological processes and improving the efficiency of water resource evaluation and management.

Trade-off analyses between food provision and soil conservation service of Grain for Green Program in Mountainous Area

The Grain for Green Program and soil and water conservation engineering initiatives are crucial for controlling erosion in steep-slope agriculture.However,it is still unclear how these two management methods should be carried out in respect to the situation in mountainous areas.Therefore,taking a typical mountainous area in southwest China as an example,we simulated six scenarios in order to compare the food provisioning service(FPS)and soil conservation service of the Grain for Green Program(converting to grassland)and Construction Measures(converting to sloping terrace)under different slopes.Results showed that when farmland with a>25°slope was converted into grassland,the amount of soil erosion(M)decreased by 21.0%,while FPS decreased by only 0.7%.However,when farmland with a>25°slope was converted into sloping terrace,M decreased by 31.3%while FPS increased by 18.7%.With the increases of farmland slope ranges in the Construction Measures scenario,M gradually decreased and FPS gradually increased.Particularly when farmland>15°was converted into sloping terrace,M decreased by 63.9%and FPS increased by 52.7%.Furthermore,the trade-offs of Construction Measures are lower than that of Grain for Green on different slope ranges.Therefore,we conclude that Construction Measures are a more suitable method in mountainous areas than the Grain for Green,and we suggest that further research be conducted to consider the ecological risks of construction engineering measures.

Effects of physical crust on soil detachment by overland flow in the Loess Plateau region of China

Physical soil crust(PSC),a key component of surface soil structure,exists extensively in loess areas.PSC is considered to have a significant effect on soil detachment processes.However,the long-term effects and the corresponding mechanisms of PSC on soil detachment by overland flow are still not well understood,especially in natural environments.To investigate temporal variation in soil erosion resistance and the underlying factors during PSC formation,an 8×8-m soil plot was exposed to natural conditions in the Loess Plateau over a 524-day period spanning two rainy seasons and a winter between them.A flume test was conducted to determine soil detachment capacity(Dc)under six designed flow shear stress levels(5.66-22.11 Pa)using crusted(SC)and non-crusted(NSC)soil samples at different PSC development stages.Subsequently,two soil erosion resistance parameters,rill erodibility(K_(r))and critical shear stress(τ_(c)),were calculated.Over time,in the SC and NSC treatments,K_(r)decreased from 0.516 to 0.120 s m^(-1)and 0.521 to 0.223 s m^(-1),respectively,whileτ_(c)increased from 0.49 to 4.42 Pa and 0.26-2.46 Pa,respectively.Variation in soil erosion resistance was rapid in the first one to two months,and then slowed down,with slight fluctuations afterwards.In the SC treatment,K_(r)was 42%lower andτ_(c)was 67%greater than those in the NSC treatment.Soil properties changed greatly for both treatments.SCT increased from 0 to 7.09 mm in the SC treatment.Coh increased from 2.91 to 9.04 kPa and 3.01-4.78 kPa in SC and NSC treatments,respectively.Both soil erosion resistance parameters could be well predicted by SCT and Coh in the SC treatment(R^(2)≥0.82),while their best predictor was Coh in the NSC treatment(R^(2)≥0.90).The results demonstrate that PSC formation enhances soil erosion resistance in the soil detachment process in the loess region under natural conditions.Our study revealed the important role and complexity of PSC in the process of soil erosion,and provided theoretical and data support for accurate understanding and prediction of soil erosion.

Remote estimates of suspended particulate matter in global lakes using machine learning models

Suspended particulate matter(SPM)in lakes exerts strong impact on light propagation,aquatic ecosystem productivity,which co-varies with nutrients,heavy metal and micro-pollutant in waters.In lakes,SPM exerts strong absorption and backscattering,ultimately affects water leaving signals that can be detected by satellite sensors.Simple regression models based on specific band or hand ratios have been widely used for SPM estimate in the past with moderate accuracy.There are still rooms for model accuracy improvements,and machine learning models may solve the non-linear relationships between spectral variable and SPM in waters.We assembled more than 16,400 in situ measured SPM in lakes from six continents(excluding the Antarctica continent),of which 9640 samples were matched with Landsat overpasses within±7 days.Seven machine learning algorithms and two simple regression methods(linear and partial least squares models)were used to estimate SPM in lakes and the performance were compared.To overcome the problem of imbalance datasets in regression,a Synthetic Minority Over-Sampling technique for regression with Gaussian Noise(SMOGN)was adopted in this study.Through comparison,we found that gradient boosting decision tree(GBDT),random forest(RF),and extreme gradient boosting(XGBoost)models demonstrated good spatiotemporal transferability with SMOGN processed dataset,and has potential to map SPM at different year with good quality of Landsat land surface reflectance images.In all the tested modeling approaches,the GBDT model has accurate calibration(n=6428,R^(2)=0.95,MAPE=29.8%)from SPM collected in 2235 lakes across the world,and the validation(n=3214,R^(2)=0.84,MAPE=38.8%)also exhibited stable performance.Further,the good performances were also exhibited by RF model with calibration(R^(2)=0.93)and validation(R^(2)=0.86,MAPE=24.2%)datasets.We applied GBDT and RF models to map SPM of typical lakes,and satisfactory result was obtained.In addition,the GBDT model was evaluated by historical SPM measurements coincident with different Landsat sensors(L5-TM,L7-ETM+,and L8-OLI),thus the model has the potential to map SPM of lakes for monitoring temporal variations,and tracks lake water SPM dynamics in approximately the past four decades(1984-2021)since Landsat-5/TM was launched in 1984.

Best management practices to reduce soil erosion and change water balance components in watersheds under grain and dairy production

Soil erosion and sedimentation are among the most serious global environmental problems.Soil and water conservation measures have been proven effective ways to reduce soil loss.The objective of this study was to evaluate the impact of three approaches of soil and water conservation measures(soil management,vegetative measures,and structural practices)on soil erosion and water balance of two paired agricultural watersheds located in Southern Brazil.Streamflow and sediment monitoring was carried out from 2016 to 2019 in the two small paired agricultural watersheds;called North watershed(NW)and South watershed(SW).Modeling using Soil&Water Assessment Tool(SWAT)was performed to simulate individual(nine scenarios)and combined(four scenarios)best management practices(BMPs),by including the three approaches.Among the nine individual BMP scenarios,the most effective in reducing soil erosion was crop rotation and cover crop(sediment yield,SY,reduction of 38.4 for NW,and 28.8%for SW).Among the four combined scenarios,the association of all conservation approaches was the most effective in reducing soil erosion(SY reduction of 46 for NW,and 41.5%for SW),followed by the vegetative measures scenario(SY reduction of 43.5 and 34.1%for NW and SW).All combined scenarios increased infiltration and subsurface water components,and decreased surface runoff.The findings of this study can help farmers and policymakers choosing appropriate BMPs to reduce current soil erosion problems and promote water and soil conservation.

GUIDE FOR AUTHORS

INTRODUCTION Types of paper Contributions falling into the following categories will be considered for publication:Original research papers,reviews,letters to the editor.Please ensure that you select the appropriate article type from the list of options when making your submission.Authors contributing to special issues should ensure that they select the special issue article type from this list.