Background:There is an urgent need for quantifying the terrestrial carbon sink in the context of global carbon emissions.However,neither the flux measurements,nor the national wood balances fulfil this purpose.In this...Background:There is an urgent need for quantifying the terrestrial carbon sink in the context of global carbon emissions.However,neither the flux measurements,nor the national wood balances fulfil this purpose.In this discussion article we point at various shortcomings and necessary improvements of these approaches in order to achieve a true quantification of the carbon exchange of land surfaces.Results:We discuss the necessity of incorporating all lateral fluxes,but mainly the export of biomass by harvest,into the flux balance and to recognize feedbacks between management and fluxes to make flux measurements compatible with inventories.At the same time,we discuss the necessity that national reports of wood use need to fully recognize the use of wood for energy use.Both approaches of establishing an ecosystem carbon balance,fluxes and inventories,have shortcomings.Conclusions:Including harvest and feedbacks by management appears to be the main requirement for the flux approach.A better quantification of wood use for bioenergy seems a real need for integrating the national wood balances into the global carbon cycle.展开更多
Climate change is a major concern of humanity. One of the consequences of climate change is global warming causing melting glaciers, rising sea levels and shoreline regression. In Togo, the regression of shoreline lea...Climate change is a major concern of humanity. One of the consequences of climate change is global warming causing melting glaciers, rising sea levels and shoreline regression. In Togo, the regression of shoreline leads to coastal erosion with significant damage on socio-economic infrastructures and hu</span><span style="font-family:Verdana;">man habitats. This research, basing on geospatial techniques, focuses on coastal </span><span style="font-family:Verdana;">erosion monitoring from 1988 to 2018 in Togo. It is interested in the extrac</span><span style="font-family:Verdana;">tion of shoreline and in the analysis of change. Various satellite images index</span></span><span style="font-family:Verdana;">es</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">have been developed for shoreline extraction but the major scientific problem concerns the precision of the different classification algorithms methods used for the extraction of the shoreline from these water index. This study used NDWI index from multisource satellite images. It assesses the performance of </span><span style="font-family:Verdana;">Otsu threshold segmentation, Iso Cluster Unsupervised Classification and Supp</span><span style="font-family:Verdana;">ort Vector Machine (SVM) Supervised Classification methods for the</span><span style="font-family:Verdana;"> extraction of the shoreline on NDWI index. The topographic morphology such </span><span style="font-family:Verdana;">as linear and non-linear coastal surfaces have been considered. The estimation</span><span style="font-family:Verdana;"> of the rates of change of the shoreline was performed using the statistical linear regression method (LRR). The results revealed that the SVM Supervised </span><span style="font-family:Verdana;">Classification method showed good performance on linear and non-linear coastal </span><span style="font-family:Verdana;">surface than the other methods. For the kinematics of the shoreline, the southwest of the Togolese coast has an average erosion rate ranging from 2.49 to 5.07 m per year. The results obtained will serve as decision-making support tools for the design and implementation of appropriate adaptations plans to avoid the immersion of the asphalt road by sea, displacement of population</span><b> </b><span style="font-family:Verdana;">and disturbance of human habitats.展开更多
We elaborate an error budget for the long-term accuracy of IGS（International Global Navigation Satellite System Service） polar motion estimates, concluding that it is probably about 25-30 μas（1-sigma）overall, alt...We elaborate an error budget for the long-term accuracy of IGS（International Global Navigation Satellite System Service） polar motion estimates, concluding that it is probably about 25-30 μas（1-sigma）overall, although it is not possible to quantify possible contributions（mainly annual） that might transfer directly from aliases of subdaily rotational tide errors. The leading sources are biases arising from the need to align daily, observed terrestrial frames, within which the pole coordinates are expressed and which are continuously deforming, to the secular, linear international reference frame. Such biases are largest over spans longer than about a year. Thanks to the very large number of IGS tracking stations, the formal covariance errors are much smaller,around 5 to 10 μas. Large networks also permit the systematic frame-related errors to be more effectively minimized but not eliminated. A number of periodic errors probably also influence polar motion results, mainly at annual, GPS（Global Positioning System） draconitic, and fortnightly periods, but their impact on the overall error budget is unlikely to be significant except possibly for annual tidal aliases. Nevertheless, caution should be exercised in interpreting geophysical excitations near any of the suspect periods.展开更多
The present study aimed to provide the basics needed to reconcile the fight against poverty with the need of a good management of community resources in the context of local and sustainable development. It focused on ...The present study aimed to provide the basics needed to reconcile the fight against poverty with the need of a good management of community resources in the context of local and sustainable development. It focused on the identification of geographic location and spatio-temporal dynamics of these resources in the southeastern part of Togo. The methodological approach was based on the spatial analysis of the area for the years 1988, 2000 and 2018 by combining optical imagery from Landsat TM, ETM+ and Sentinel-2A MSI satellites with radar imagery from Sentinel-1A IW/GRDH. Spatial analysis showed a fragmented spatial structure undergoing major changes for the period 1988-2018. Plantations, riparian formations, agglomerations, water bodies and wetlands increased respectively by 4.61%, 2.09%, 1.07%, 0.43% and 0.35% annually, while forests, savannahs, crops and fallow lands decreased annually by 0.71%, 5.87% and 1.97%. For the “forests” class, seven community forests geographically organized in three sub-groups were identified and mapped. The analysis of their areas pointed to the fact that out of 667 ha of community forests in 1988, only 415 ha remain in 2018, which means a loss of 37.78% in forest areas over the 30 years, or an annual deforestation rate of 1.64%. The different spatial changes observed could be attributed to several unsustainable human activities. The land use maps for the years 1988, 2000 and 2018 will contribute to resource localization and protection in sensitive areas or, in other words, to the integrated and rational management of these resources. The different identified and mapped community forests could serve as management units for managers in developing their management plans.展开更多
Background:Higher exportation of harvest residues from forests due to increased demand for woody biomass,has reportedly diminished soil mineral resources and may lead to degraded tree nutrition as well as growth.Howev...Background:Higher exportation of harvest residues from forests due to increased demand for woody biomass,has reportedly diminished soil mineral resources and may lead to degraded tree nutrition as well as growth.However,as nutrients become less available in the soil,the remobilization of nutrients in biomass tissues(plant internal cycling)helps sustain tree nutrition.Our study aims to quantify the impact of Removing Harvest Residues and Litter(RHRL)during five years on tree growth,wood density,and stem wood nutrient concentrations in young beech and oak forest stands.Result:Our study found that,RHRL significantly decreased tree growth ring width by 14%,and wood density by 3%,in beech trees,in near bark rings.RHRL also significantly reduced nutrient concentration in near bark and near pith areas of both studied species.Mg,Na and S were found lower by 44%,76%,and 56%,respectively,in near bark area of beech trees.In near bark area of oak trees,K,Ca,Mg,Na,S,and Fe were lower by 20%,25%,41%,48%,41%,and 16%,respectively.K and Mg concentrations decreased more strongly in near pith area compared to near bark area suggesting internal translocation of these two elements.Conclusion:In beech trees,wood density proved to be an important factor while quantifying the effect of removing harvest residuals on tree growth and biomass.Soil nutrient loss intensified the remobilization of nutrients con-tained in older tree rings(close to the pith)towards newly formed rings(close to bark).In our study,in beech trees,K was found to be the most recycled major nutrient.These results demonstrate the potential of such analysis for providing valuable insight into the effect of RHRL in premature stands on the physiological adaptive strategies of trees and an indication of soil fertility status.展开更多
Exceptional bound(EB)states represent a unique new class of robust bound states protected by the defectiveness of non-Hermitian exceptional points.Conceptually distinct from the more well-known topological states and ...Exceptional bound(EB)states represent a unique new class of robust bound states protected by the defectiveness of non-Hermitian exceptional points.Conceptually distinct from the more well-known topological states and non-Hermitian skin states,they were recently discovered as a novel source of negative entanglement entropy in the quantum entanglement context.Yet,EB states have been physically elusive,being originally interpreted as negative probability eigenstates of the propagator of nonHermitian Fermi gases.In this work,we show that EB states are in fact far more ubiquitous,also arising robustly in broad classes of systems whether classical or quantum.This hinges crucially on a newlydiscovered spectral flow that rigorously justifies the EB nature of small candidate lattice systems.As a highlight,we present their first experimental realization through an electrical circuit,where they manifest as prominent stable resonant voltage profiles.Our work brings a hitherto elusive but fundamentally distinctive quantum phenomenon into the realm of classical metamaterials,and provides a novel pathway for the engineering of robust modes in otherwise sensitive systems..展开更多
Updating an authoritative Land Use and Land Cover(LULC)database requires many resources.Volunteered geographic information(VGI)involves citizens in the collection of data about their spatial environment.There is a gro...Updating an authoritative Land Use and Land Cover(LULC)database requires many resources.Volunteered geographic information(VGI)involves citizens in the collection of data about their spatial environment.There is a growing interest in using existing VGI to update authoritative databases.This paper presents a framework aimed at integrating multi-source VGI based on a data fusion technique,in order to update an authoritative land use database.Each VGI data source is considered to be an independent source of information,which is fused together using Dempster-Shafer Theory(DST).The framework is tested in the updating of the authoritative land use data produced by the French National Mapping Agency.Four data sets were collected from several in-situ and remote campaigns run between 2018 and 2020 by contributors with varying profiles.The data fusion approach achieved an overall accuracy of 85.6%for the 144 features having at least two contributions when the confidence threshold was set to 0.05.Despite the heterogeneity and limited amount of VGI used,the results are promising,with 99%of the LU polygons updated or enriched.These results show the potential of using multi-source VGI to update or enrich authoritative LU data and potentially LULC data more generally。展开更多
The rapid growth of the global population has resulted in a continuous increase in cropland intensity and a shortening of the fallow period as part of the cropland rotation cycle.Yet,there is a lack of systematic know...The rapid growth of the global population has resulted in a continuous increase in cropland intensity and a shortening of the fallow period as part of the cropland rotation cycle.Yet,there is a lack of systematic knowledge on the extent of fallow lands,particularly in complex landscapes,such as the mountainous regions of China.To fill this knowledge gap,taking Yuanyang County(YYC),Yunnan Province,China,as a case study,we tested a method to identify the spatial-temporal distribution of fallow land by mapping cropland with Landsat data.The overall accuracy of land cover classification,including cropland,ranged between 90.1%and 95.8%from 1998 to 2019.The average accuracy of fallow plots was 75.7%from 2001 to 2019.The annual fallow rate varied between 8.3%and 54.3%,with an average of 20.7%.Kernel density estimated with the probability density function showed that fallow varied between 5 and 13 blocks per km2,gradually decreasing from the central area to the periphery.Increasing elevation,the low value of regional domestic products,and the increased distance to rural settlements were closely related to the higher proportions of fallow land.The approach presented here can be applied to map fallow land in other regions.展开更多
This paper presents a tool for the numerical propagation of high-fidelity astrodynamics,called PHiFA.The coupled orbit–attitude dynamics for space objects are modeled by considering various types of perturbative forc...This paper presents a tool for the numerical propagation of high-fidelity astrodynamics,called PHiFA.The coupled orbit–attitude dynamics for space objects are modeled by considering various types of perturbative forces and torques.Two methods have been implemented to calculate the surface forces:the area matrix method and the beam method.The beam method is more precise as it discretizes the source media(e.g.,sunlight and aerodynamic wind)and the surface of the target into multiple rays and finite elements,respectively,and then accumulates the effect of each hit.The PHiFA tool was tested and validated using a 3U CubeSat model and the defunct European environment satellite(Envisat)model.展开更多
文摘Background:There is an urgent need for quantifying the terrestrial carbon sink in the context of global carbon emissions.However,neither the flux measurements,nor the national wood balances fulfil this purpose.In this discussion article we point at various shortcomings and necessary improvements of these approaches in order to achieve a true quantification of the carbon exchange of land surfaces.Results:We discuss the necessity of incorporating all lateral fluxes,but mainly the export of biomass by harvest,into the flux balance and to recognize feedbacks between management and fluxes to make flux measurements compatible with inventories.At the same time,we discuss the necessity that national reports of wood use need to fully recognize the use of wood for energy use.Both approaches of establishing an ecosystem carbon balance,fluxes and inventories,have shortcomings.Conclusions:Including harvest and feedbacks by management appears to be the main requirement for the flux approach.A better quantification of wood use for bioenergy seems a real need for integrating the national wood balances into the global carbon cycle.
文摘Climate change is a major concern of humanity. One of the consequences of climate change is global warming causing melting glaciers, rising sea levels and shoreline regression. In Togo, the regression of shoreline leads to coastal erosion with significant damage on socio-economic infrastructures and hu</span><span style="font-family:Verdana;">man habitats. This research, basing on geospatial techniques, focuses on coastal </span><span style="font-family:Verdana;">erosion monitoring from 1988 to 2018 in Togo. It is interested in the extrac</span><span style="font-family:Verdana;">tion of shoreline and in the analysis of change. Various satellite images index</span></span><span style="font-family:Verdana;">es</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">have been developed for shoreline extraction but the major scientific problem concerns the precision of the different classification algorithms methods used for the extraction of the shoreline from these water index. This study used NDWI index from multisource satellite images. It assesses the performance of </span><span style="font-family:Verdana;">Otsu threshold segmentation, Iso Cluster Unsupervised Classification and Supp</span><span style="font-family:Verdana;">ort Vector Machine (SVM) Supervised Classification methods for the</span><span style="font-family:Verdana;"> extraction of the shoreline on NDWI index. The topographic morphology such </span><span style="font-family:Verdana;">as linear and non-linear coastal surfaces have been considered. The estimation</span><span style="font-family:Verdana;"> of the rates of change of the shoreline was performed using the statistical linear regression method (LRR). The results revealed that the SVM Supervised </span><span style="font-family:Verdana;">Classification method showed good performance on linear and non-linear coastal </span><span style="font-family:Verdana;">surface than the other methods. For the kinematics of the shoreline, the southwest of the Togolese coast has an average erosion rate ranging from 2.49 to 5.07 m per year. The results obtained will serve as decision-making support tools for the design and implementation of appropriate adaptations plans to avoid the immersion of the asphalt road by sea, displacement of population</span><b> </b><span style="font-family:Verdana;">and disturbance of human habitats.
文摘We elaborate an error budget for the long-term accuracy of IGS（International Global Navigation Satellite System Service） polar motion estimates, concluding that it is probably about 25-30 μas（1-sigma）overall, although it is not possible to quantify possible contributions（mainly annual） that might transfer directly from aliases of subdaily rotational tide errors. The leading sources are biases arising from the need to align daily, observed terrestrial frames, within which the pole coordinates are expressed and which are continuously deforming, to the secular, linear international reference frame. Such biases are largest over spans longer than about a year. Thanks to the very large number of IGS tracking stations, the formal covariance errors are much smaller,around 5 to 10 μas. Large networks also permit the systematic frame-related errors to be more effectively minimized but not eliminated. A number of periodic errors probably also influence polar motion results, mainly at annual, GPS（Global Positioning System） draconitic, and fortnightly periods, but their impact on the overall error budget is unlikely to be significant except possibly for annual tidal aliases. Nevertheless, caution should be exercised in interpreting geophysical excitations near any of the suspect periods.
文摘The present study aimed to provide the basics needed to reconcile the fight against poverty with the need of a good management of community resources in the context of local and sustainable development. It focused on the identification of geographic location and spatio-temporal dynamics of these resources in the southeastern part of Togo. The methodological approach was based on the spatial analysis of the area for the years 1988, 2000 and 2018 by combining optical imagery from Landsat TM, ETM+ and Sentinel-2A MSI satellites with radar imagery from Sentinel-1A IW/GRDH. Spatial analysis showed a fragmented spatial structure undergoing major changes for the period 1988-2018. Plantations, riparian formations, agglomerations, water bodies and wetlands increased respectively by 4.61%, 2.09%, 1.07%, 0.43% and 0.35% annually, while forests, savannahs, crops and fallow lands decreased annually by 0.71%, 5.87% and 1.97%. For the “forests” class, seven community forests geographically organized in three sub-groups were identified and mapped. The analysis of their areas pointed to the fact that out of 667 ha of community forests in 1988, only 415 ha remain in 2018, which means a loss of 37.78% in forest areas over the 30 years, or an annual deforestation rate of 1.64%. The different spatial changes observed could be attributed to several unsustainable human activities. The land use maps for the years 1988, 2000 and 2018 will contribute to resource localization and protection in sensitive areas or, in other words, to the integrated and rational management of these resources. The different identified and mapped community forests could serve as management units for managers in developing their management plans.
基金This work was supported within the XyloDensMap project,INRAE funded by the French Ministry of Agriculture under the convention n°A6.01/2017.
文摘Background:Higher exportation of harvest residues from forests due to increased demand for woody biomass,has reportedly diminished soil mineral resources and may lead to degraded tree nutrition as well as growth.However,as nutrients become less available in the soil,the remobilization of nutrients in biomass tissues(plant internal cycling)helps sustain tree nutrition.Our study aims to quantify the impact of Removing Harvest Residues and Litter(RHRL)during five years on tree growth,wood density,and stem wood nutrient concentrations in young beech and oak forest stands.Result:Our study found that,RHRL significantly decreased tree growth ring width by 14%,and wood density by 3%,in beech trees,in near bark rings.RHRL also significantly reduced nutrient concentration in near bark and near pith areas of both studied species.Mg,Na and S were found lower by 44%,76%,and 56%,respectively,in near bark area of beech trees.In near bark area of oak trees,K,Ca,Mg,Na,S,and Fe were lower by 20%,25%,41%,48%,41%,and 16%,respectively.K and Mg concentrations decreased more strongly in near pith area compared to near bark area suggesting internal translocation of these two elements.Conclusion:In beech trees,wood density proved to be an important factor while quantifying the effect of removing harvest residuals on tree growth and biomass.Soil nutrient loss intensified the remobilization of nutrients con-tained in older tree rings(close to the pith)towards newly formed rings(close to bark).In our study,in beech trees,K was found to be the most recycled major nutrient.These results demonstrate the potential of such analysis for providing valuable insight into the effect of RHRL in premature stands on the physiological adaptive strategies of trees and an indication of soil fertility status.
基金supported by the National Key R&D Program of China(2022YFA1404904)the National Research Foundation Singapore grant under its QEP2.0 programme(NRF2021-QEP2-02-P09)+1 种基金the Ministry of Education(MOE)Tier-II grant(MOE-T2EP502220008)supported by the SUTD-ZJU Thematic Research Grant(SUTD-ZJU(TR)202203)。
文摘Exceptional bound(EB)states represent a unique new class of robust bound states protected by the defectiveness of non-Hermitian exceptional points.Conceptually distinct from the more well-known topological states and non-Hermitian skin states,they were recently discovered as a novel source of negative entanglement entropy in the quantum entanglement context.Yet,EB states have been physically elusive,being originally interpreted as negative probability eigenstates of the propagator of nonHermitian Fermi gases.In this work,we show that EB states are in fact far more ubiquitous,also arising robustly in broad classes of systems whether classical or quantum.This hinges crucially on a newlydiscovered spectral flow that rigorously justifies the EB nature of small candidate lattice systems.As a highlight,we present their first experimental realization through an electrical circuit,where they manifest as prominent stable resonant voltage profiles.Our work brings a hitherto elusive but fundamentally distinctive quantum phenomenon into the realm of classical metamaterials,and provides a novel pathway for the engineering of robust modes in otherwise sensitive systems..
基金supported by Horizon 2020 Framework Programme[grant number 689812].
文摘Updating an authoritative Land Use and Land Cover(LULC)database requires many resources.Volunteered geographic information(VGI)involves citizens in the collection of data about their spatial environment.There is a growing interest in using existing VGI to update authoritative databases.This paper presents a framework aimed at integrating multi-source VGI based on a data fusion technique,in order to update an authoritative land use database.Each VGI data source is considered to be an independent source of information,which is fused together using Dempster-Shafer Theory(DST).The framework is tested in the updating of the authoritative land use data produced by the French National Mapping Agency.Four data sets were collected from several in-situ and remote campaigns run between 2018 and 2020 by contributors with varying profiles.The data fusion approach achieved an overall accuracy of 85.6%for the 144 features having at least two contributions when the confidence threshold was set to 0.05.Despite the heterogeneity and limited amount of VGI used,the results are promising,with 99%of the LU polygons updated or enriched.These results show the potential of using multi-source VGI to update or enrich authoritative LU data and potentially LULC data more generally。
基金supported by the National Natural Science Foundation of China[grant number 42071233]the Strategic Priority Research Program of Chinese Academy of Sciences[grant number XDA20040201]and the Second Tibetan Plateau Scientific Expedition and Research Program[grant number 2019QZKK0603].
文摘The rapid growth of the global population has resulted in a continuous increase in cropland intensity and a shortening of the fallow period as part of the cropland rotation cycle.Yet,there is a lack of systematic knowledge on the extent of fallow lands,particularly in complex landscapes,such as the mountainous regions of China.To fill this knowledge gap,taking Yuanyang County(YYC),Yunnan Province,China,as a case study,we tested a method to identify the spatial-temporal distribution of fallow land by mapping cropland with Landsat data.The overall accuracy of land cover classification,including cropland,ranged between 90.1%and 95.8%from 1998 to 2019.The average accuracy of fallow plots was 75.7%from 2001 to 2019.The annual fallow rate varied between 8.3%and 54.3%,with an average of 20.7%.Kernel density estimated with the probability density function showed that fallow varied between 5 and 13 blocks per km2,gradually decreasing from the central area to the periphery.Increasing elevation,the low value of regional domestic products,and the increased distance to rural settlements were closely related to the higher proportions of fallow land.The approach presented here can be applied to map fallow land in other regions.
基金support from the Guangdong Basic and Applied Basic Research Foundation Project(No.2020A1515110216)the support of the Cooperative Research Center for Space Environment Management(SERC Limited)through the Australian Government’s Cooperative Research Center Program when the work was initialized.
文摘This paper presents a tool for the numerical propagation of high-fidelity astrodynamics,called PHiFA.The coupled orbit–attitude dynamics for space objects are modeled by considering various types of perturbative forces and torques.Two methods have been implemented to calculate the surface forces:the area matrix method and the beam method.The beam method is more precise as it discretizes the source media(e.g.,sunlight and aerodynamic wind)and the surface of the target into multiple rays and finite elements,respectively,and then accumulates the effect of each hit.The PHiFA tool was tested and validated using a 3U CubeSat model and the defunct European environment satellite(Envisat)model.
