Accurate estimates of forest aboveground biomass(AGB)are essential for global carbon cycle studies and have widely relied on approaches using spectral and structural information of forest canopies extracted from vario...Accurate estimates of forest aboveground biomass(AGB)are essential for global carbon cycle studies and have widely relied on approaches using spectral and structural information of forest canopies extracted from various remote sensing datasets.However,combining the advantages of active and passive data sources to improve estimation accuracy remains challenging.Here,we proposed a new approach for forest AGB modeling based on allometric relationships and using the form of power-law to integrate structural and spectral information.Over 60 km^(2) of drone light detection and ranging(LiDAR)data and 1,370 field plot measurements,covering the four major forest types of China(coniferous forest,sub-tropical broadleaf forest,coniferous and broadleaf-leaved mixed forest,and tropical broadleaf forest),were collected together with Sentinel-2 images to evaluate the proposed approach.The results show that the most universally useful structural and spectral metrics are the average values of canopy height and spectral index rather than their maximum values.Compared with structural attributes used alone,combining structural and spectral information can improve the estimation accuracy of AGB,increasing R^(2) by about 10%and reducing the root mean square error by about 22%;the accuracy of the proposed approach can yield a R^(2) of 0.7 in different forests types.The proposed approach performs the best in coniferous forest,followed by sub-tropical broadleaf forest,coniferous and broadleaf-leaved mixed forest,and then tropical broadleaf forest.Furthermore,the simple linear regression used in the proposed method is less sensitive to sample size and outperforms statistically multivariate machine learning-based regression models such as stepwise multiple regression,artificial neural networks,and Random Forest.The proposed approach may provide an alternative solution to map large-scale forest biomass using space-borne LiDAR and optical images with high accuracy.展开更多
While numerous allometric models exist for estimating biomass in trees with single stems,models for multi-stemmed species are scarce.This study presents models for predicting aboveground biomass(AGB)in European hazel(...While numerous allometric models exist for estimating biomass in trees with single stems,models for multi-stemmed species are scarce.This study presents models for predicting aboveground biomass(AGB)in European hazel(Corylus avellana L.),growing in multi-stemmed shrub form.We measured the size and harvested the biomass of 30 European hazel shrubs,drying and weighing their woody parts and leaves separately.AGB(dry mass)and leaf area models were established using a range of predictors,such as the upper height of the shrub,number of shoots per shrub,canopy projection area,stem base diameter of the thickest stem,and the sum of cross-sectional areas of all stems at the stem base.The latter was the best predictor of AGB,but the most practically useful variables,defined as relatively easy to measure by terrestrial or aerial approaches,were the upper height of the shrub and the canopy projection area.The leaf biomass to AGB ratio decreased with the shrub's height.Specific leaf area of shaded leaves increases with shrub height,but that of leaves at the top of the canopy does not change significantly.Given that the upper shrub height and crown projection of European hazel can be estimated using remote sensing approaches,especially UAV and LIDAR,these two variables appear the most promising for effective measurement of AGB in hazel.展开更多
Site index(SI)is determined from the top height development and is a proxy for forest productivity,defined as the expected top height for a given species at a certain index age.In Norway,an index age of 40 years is us...Site index(SI)is determined from the top height development and is a proxy for forest productivity,defined as the expected top height for a given species at a certain index age.In Norway,an index age of 40 years is used.By using bi-temporal airborne laser scanning(ALS)data,SI can be determined using models estimated from SI observed on field plots(the direct approach)or from predicted top heights at two points in time(the height differential approach).Time series of ALS data may enhance SI determination compared to conventional methods used in operational forest inventory by providing more detailed information about the top height development.We used longitudinal data comprising spatially consistent field and ALS data collected from training plots in 1999,2010,and 2022 to determine SI using the direct and height differential approaches using all combinations of years and performed an external validation.We also evaluated the use of data assimilation.Values of root mean square error obtained from external validation were in the ranges of 16.3%–21.4%and 12.8%–20.6%of the mean fieldregistered SI for the direct approach and the height differential approach,respectively.There were no statistically significant effects of time series length or the number of points in time on the obtained accuracies.Data assimilation did not result in any substantial improvement in the obtained accuracies.Although a time series of ALS data did not yield greater accuracies compared to using only two points in time,a larger proportion of the study area could be used in ALS-based determination of SI when a time series was available.This was because areas that were unsuitable for SI determination between two points in time could be subject to SI determination based on data from another part of the time series.展开更多
目的探究新兵足弓指数与足踝肌肉力量及军事训练伤的关系。方法选取驻闽某部队新兵518名,采用足底压力步态评估系统的足印法计算足弓指数,并使用表面肌电图(sEMG)测量足踝肌肉的均方根(RMS)值。根据足弓指数将受试者分为低足弓组、正常...目的探究新兵足弓指数与足踝肌肉力量及军事训练伤的关系。方法选取驻闽某部队新兵518名,采用足底压力步态评估系统的足印法计算足弓指数,并使用表面肌电图(sEMG)测量足踝肌肉的均方根(RMS)值。根据足弓指数将受试者分为低足弓组、正常足弓组和高足弓组,比较三组不同足弓高度受试者的一般资料,并比较三组受试者足踝训练伤发生率、足踝肌肉力量。另将新兵入伍训练期间出现足踝训练伤的受试者及未出现足踝训练伤的受试者分为训练伤组和对照组,比较两组受试者在一般资料、足弓指数和足踝肌肉力量的差异性,同时采用Spearman秩相关分析足弓指数与足踝肌肉力量、军事训练伤的相关性。结果低足弓组(n=131)、正常足弓组(n=207)、高足弓组(n=180)的一般资料(年龄、身高、体重及BMI)差异无统计学意义(P>0.05);高足弓组的胫前肌RMS(302.28±81.64 vs 336.77±83.19,302.28±81.64 vs325.52±83.30)、腓肠肌RMS(120.83±37.21 vs 133.62±37.81,120.83±37.21 vs 132.12±37.55)、腓骨长肌RMS(178.78±52.92 vs 197.61±50.82,178.78±52.92 vs 192.41±51.09)较正常足弓和低足弓组更低,足踝训练伤发生率较正常足弓和低足弓组(23.89%vs 13.53%,23.89%vs 15.27%)更高(P<0.05)。此外,训练伤组(n=91)和对照组(n=427)的一般资料差异无统计学意义(P>0.05),但是训练伤组的足弓指数(22.51±5.88 vs 23.83±5.48)及足踝肌肉RMS(304.12±84.81 vs 325.74±83.29,121.09±36.18 vs 130.44±38.12,177.83±52.00 vs 192.29±51.93)均较对照组低(P<0.05)。Spearman秩相关分析显示,足弓指数与足踝肌肉(胫前肌、腓肠肌、腓骨长肌)RMS(r=0.171、r=0.116、r=0.114)、足踝训练伤发生率(r=-0.093)存在相关性(P<0.05)。结论低足弓和正常足弓新兵拥有比高足弓新兵更高的足踝肌肉力量,且训练伤发生率更低。新兵足弓指数与足踝肌肉力量、足踝训练伤存在相关性。展开更多
In this study height growth models for hybrid aspen were developed using three growth equations. The mean age of the hybrid aspen was 21 years （range 15-51 years） with a mean stand density of 946 stems ha-~ （87-237...In this study height growth models for hybrid aspen were developed using three growth equations. The mean age of the hybrid aspen was 21 years （range 15-51 years） with a mean stand density of 946 stems ha-~ （87-2374） and a mean diameter at breast height （over bark） of 19.6 cm （8.5-40.8 cm）. Site index was also examined in relation to soil type. Multiple samples were collected for three types of soil： light clay, medium clay and till. Site index curves were constructed using the col- lected data and compared with published reports. A number of dynamic equations were assessed for modeling top-height growth from total age.展开更多
The“super rice”breeding program in China has been successful in developing high-yielding hybrids,including few with high harvest index values.However,there is limited information on the relationship between lodging ...The“super rice”breeding program in China has been successful in developing high-yielding hybrids,including few with high harvest index values.However,there is limited information on the relationship between lodging resistance and harvest index,and the mechanisms underlying the relationship in super-rice hybrids.In this study,a two-year field experiment was conducted to compare lodging resistance and its related traits between two superrice hybrids differing in harvest index,i.e.,Guiliangyou 2(G2)with a high harvest index and Y-liangyou 1(Y1)with a typical harvest index of modern high-yielding rice varieties.Results showed that compared to Y1,G2 was lower in plant height due to its lower aboveground N uptake,and its higher stem breaking resistance(i.e.,lower stem breaking index)resulted from a lower stem height at its center of gravity.Consequently,G2 had a higher lodging resistance(i.e.,lower plant lodging index)than Y1.This study suggests that developing super-rice hybrids with high harvest index values is a possible way to achieve both high grain yield and strong lodging resistance in rice.展开更多
Combining with the exigent demand of the development of satellite gravimetry system in China, aiming at the determination of technical indexes of gravity satellite orbit parameters, on the basis of the numerical exper...Combining with the exigent demand of the development of satellite gravimetry system in China, aiming at the determination of technical indexes of gravity satellite orbit parameters, on the basis of the numerical experiments and results analysis, the design indexes of gravity satellite orbit height, inter-satellite range and the orbit inclination are analyzed and calculated, and the issues towards twin gravity satellites such as coherence requirement of the orbit semi-major axes, control requirement of the pitch angle and time interval requirement to keep twin satellites formation in mobility are diseussed. Results show that the satellite orbit height is 400 km to 500 km, the inter-satellite range is about 220 km, the satellite orbit inclination is between polar orbit and sun-synchronous orbit, the semi-major axes difference of twin satellites orbit is within ± 70. 146 m, the pitch angle of twin satellites is about 0.9 degree, and the time interval to keep twin satellites formation in mobility is 7 days to 15 days.展开更多
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA19050401)the National Natural Science Foundation of China(41871332,31971575,41901358).
文摘Accurate estimates of forest aboveground biomass(AGB)are essential for global carbon cycle studies and have widely relied on approaches using spectral and structural information of forest canopies extracted from various remote sensing datasets.However,combining the advantages of active and passive data sources to improve estimation accuracy remains challenging.Here,we proposed a new approach for forest AGB modeling based on allometric relationships and using the form of power-law to integrate structural and spectral information.Over 60 km^(2) of drone light detection and ranging(LiDAR)data and 1,370 field plot measurements,covering the four major forest types of China(coniferous forest,sub-tropical broadleaf forest,coniferous and broadleaf-leaved mixed forest,and tropical broadleaf forest),were collected together with Sentinel-2 images to evaluate the proposed approach.The results show that the most universally useful structural and spectral metrics are the average values of canopy height and spectral index rather than their maximum values.Compared with structural attributes used alone,combining structural and spectral information can improve the estimation accuracy of AGB,increasing R^(2) by about 10%and reducing the root mean square error by about 22%;the accuracy of the proposed approach can yield a R^(2) of 0.7 in different forests types.The proposed approach performs the best in coniferous forest,followed by sub-tropical broadleaf forest,coniferous and broadleaf-leaved mixed forest,and then tropical broadleaf forest.Furthermore,the simple linear regression used in the proposed method is less sensitive to sample size and outperforms statistically multivariate machine learning-based regression models such as stepwise multiple regression,artificial neural networks,and Random Forest.The proposed approach may provide an alternative solution to map large-scale forest biomass using space-borne LiDAR and optical images with high accuracy.
基金funded by grants EVA4.0 No.Z.02.1.01/0.0/0.0/16_019/0000803 and ITMS2014+313011W580s provided by EU OP RDEin CZ and SKprojects APVV-18-0086,APVV-19-0387,APVV-20-0168,APVV-20-0215 and APVV-22-0056 from the Slovak Research and Development Agencysupport from the European Research Executive Agency for ReForest,Grant Agreement Nr:101060635
文摘While numerous allometric models exist for estimating biomass in trees with single stems,models for multi-stemmed species are scarce.This study presents models for predicting aboveground biomass(AGB)in European hazel(Corylus avellana L.),growing in multi-stemmed shrub form.We measured the size and harvested the biomass of 30 European hazel shrubs,drying and weighing their woody parts and leaves separately.AGB(dry mass)and leaf area models were established using a range of predictors,such as the upper height of the shrub,number of shoots per shrub,canopy projection area,stem base diameter of the thickest stem,and the sum of cross-sectional areas of all stems at the stem base.The latter was the best predictor of AGB,but the most practically useful variables,defined as relatively easy to measure by terrestrial or aerial approaches,were the upper height of the shrub and the canopy projection area.The leaf biomass to AGB ratio decreased with the shrub's height.Specific leaf area of shaded leaves increases with shrub height,but that of leaves at the top of the canopy does not change significantly.Given that the upper shrub height and crown projection of European hazel can be estimated using remote sensing approaches,especially UAV and LIDAR,these two variables appear the most promising for effective measurement of AGB in hazel.
基金part of the Centre for Research-based Innovation SmartForest:Bringing Industry 4.0 to the Norwegian forest sector(NFR SFI project no.309671,smartforest.no)。
文摘Site index(SI)is determined from the top height development and is a proxy for forest productivity,defined as the expected top height for a given species at a certain index age.In Norway,an index age of 40 years is used.By using bi-temporal airborne laser scanning(ALS)data,SI can be determined using models estimated from SI observed on field plots(the direct approach)or from predicted top heights at two points in time(the height differential approach).Time series of ALS data may enhance SI determination compared to conventional methods used in operational forest inventory by providing more detailed information about the top height development.We used longitudinal data comprising spatially consistent field and ALS data collected from training plots in 1999,2010,and 2022 to determine SI using the direct and height differential approaches using all combinations of years and performed an external validation.We also evaluated the use of data assimilation.Values of root mean square error obtained from external validation were in the ranges of 16.3%–21.4%and 12.8%–20.6%of the mean fieldregistered SI for the direct approach and the height differential approach,respectively.There were no statistically significant effects of time series length or the number of points in time on the obtained accuracies.Data assimilation did not result in any substantial improvement in the obtained accuracies.Although a time series of ALS data did not yield greater accuracies compared to using only two points in time,a larger proportion of the study area could be used in ALS-based determination of SI when a time series was available.This was because areas that were unsuitable for SI determination between two points in time could be subject to SI determination based on data from another part of the time series.
文摘目的探究新兵足弓指数与足踝肌肉力量及军事训练伤的关系。方法选取驻闽某部队新兵518名,采用足底压力步态评估系统的足印法计算足弓指数,并使用表面肌电图(sEMG)测量足踝肌肉的均方根(RMS)值。根据足弓指数将受试者分为低足弓组、正常足弓组和高足弓组,比较三组不同足弓高度受试者的一般资料,并比较三组受试者足踝训练伤发生率、足踝肌肉力量。另将新兵入伍训练期间出现足踝训练伤的受试者及未出现足踝训练伤的受试者分为训练伤组和对照组,比较两组受试者在一般资料、足弓指数和足踝肌肉力量的差异性,同时采用Spearman秩相关分析足弓指数与足踝肌肉力量、军事训练伤的相关性。结果低足弓组(n=131)、正常足弓组(n=207)、高足弓组(n=180)的一般资料(年龄、身高、体重及BMI)差异无统计学意义(P>0.05);高足弓组的胫前肌RMS(302.28±81.64 vs 336.77±83.19,302.28±81.64 vs325.52±83.30)、腓肠肌RMS(120.83±37.21 vs 133.62±37.81,120.83±37.21 vs 132.12±37.55)、腓骨长肌RMS(178.78±52.92 vs 197.61±50.82,178.78±52.92 vs 192.41±51.09)较正常足弓和低足弓组更低,足踝训练伤发生率较正常足弓和低足弓组(23.89%vs 13.53%,23.89%vs 15.27%)更高(P<0.05)。此外,训练伤组(n=91)和对照组(n=427)的一般资料差异无统计学意义(P>0.05),但是训练伤组的足弓指数(22.51±5.88 vs 23.83±5.48)及足踝肌肉RMS(304.12±84.81 vs 325.74±83.29,121.09±36.18 vs 130.44±38.12,177.83±52.00 vs 192.29±51.93)均较对照组低(P<0.05)。Spearman秩相关分析显示,足弓指数与足踝肌肉(胫前肌、腓肠肌、腓骨长肌)RMS(r=0.171、r=0.116、r=0.114)、足踝训练伤发生率(r=-0.093)存在相关性(P<0.05)。结论低足弓和正常足弓新兵拥有比高足弓新兵更高的足踝肌肉力量,且训练伤发生率更低。新兵足弓指数与足踝肌肉力量、足踝训练伤存在相关性。
文摘In this study height growth models for hybrid aspen were developed using three growth equations. The mean age of the hybrid aspen was 21 years （range 15-51 years） with a mean stand density of 946 stems ha-~ （87-2374） and a mean diameter at breast height （over bark） of 19.6 cm （8.5-40.8 cm）. Site index was also examined in relation to soil type. Multiple samples were collected for three types of soil： light clay, medium clay and till. Site index curves were constructed using the col- lected data and compared with published reports. A number of dynamic equations were assessed for modeling top-height growth from total age.
基金This study was supported by the National Natural Science Foundation of China(31771722)the Open Fund of the Guangxi Key Laboratory of Rice Genetics and Breeding(2018-15-Z06-KF17).
文摘The“super rice”breeding program in China has been successful in developing high-yielding hybrids,including few with high harvest index values.However,there is limited information on the relationship between lodging resistance and harvest index,and the mechanisms underlying the relationship in super-rice hybrids.In this study,a two-year field experiment was conducted to compare lodging resistance and its related traits between two superrice hybrids differing in harvest index,i.e.,Guiliangyou 2(G2)with a high harvest index and Y-liangyou 1(Y1)with a typical harvest index of modern high-yielding rice varieties.Results showed that compared to Y1,G2 was lower in plant height due to its lower aboveground N uptake,and its higher stem breaking resistance(i.e.,lower stem breaking index)resulted from a lower stem height at its center of gravity.Consequently,G2 had a higher lodging resistance(i.e.,lower plant lodging index)than Y1.This study suggests that developing super-rice hybrids with high harvest index values is a possible way to achieve both high grain yield and strong lodging resistance in rice.
基金supported by the National Natural Science Foundation of China(41174026,41104047,41174017)the Key laboratory Foundation of Geo-space Environment and Geodesy of Ministry of Education(11-01-03)
文摘Combining with the exigent demand of the development of satellite gravimetry system in China, aiming at the determination of technical indexes of gravity satellite orbit parameters, on the basis of the numerical experiments and results analysis, the design indexes of gravity satellite orbit height, inter-satellite range and the orbit inclination are analyzed and calculated, and the issues towards twin gravity satellites such as coherence requirement of the orbit semi-major axes, control requirement of the pitch angle and time interval requirement to keep twin satellites formation in mobility are diseussed. Results show that the satellite orbit height is 400 km to 500 km, the inter-satellite range is about 220 km, the satellite orbit inclination is between polar orbit and sun-synchronous orbit, the semi-major axes difference of twin satellites orbit is within ± 70. 146 m, the pitch angle of twin satellites is about 0.9 degree, and the time interval to keep twin satellites formation in mobility is 7 days to 15 days.
