From August to October in 2006,three times of field spectral measurements with a Field Spec FR spectroradiometer(Analytical Spectral Devices,Inc.,USA) were carried out in Shitoukoumen Reservoir,Jilin Province,Northeas...From August to October in 2006,three times of field spectral measurements with a Field Spec FR spectroradiometer(Analytical Spectral Devices,Inc.,USA) were carried out in Shitoukoumen Reservoir,Jilin Province,Northeast China. Owing to the serious soil and water loss in the upstream,reflectance curves of the reservoir were characterized by high concentrations of total suspended matter(TSM) . Extending the spectral analysis to 1200nm in the near-infrared band,this research revealed an obvious reflectance peak around 1070nm which was caused by the strong backscattering of high TSM. The method of partial least squares(PLS) regression was applied to retrieving the TSM. Reflectance in two spectral bands,i.e.,675-948nm and 1029-1105nm,were used as variables to develop PLS models. Traditional linear regression,first derivative model and logarithmic model were also used for the comparison of different models. Results showed that the PLS model based on Rrs(675) -Rrs(948) gave out best results with high precision and stability. Although the PLS model based on Rrs(1029) -Rrs(1105) did not have an outstanding performance due to lots of noise,the reflectance peak in the near-infrared band was an important TSM feature and its efficient exploitation would have a considerable significance in TSM remote sensing.展开更多
Raptors primarily use soaring-gliding flight which exploits thermals and ridge lifts over land to reduce energetic costs However during migration, these birds often have to cross water surfaces where thermal currents ...Raptors primarily use soaring-gliding flight which exploits thermals and ridge lifts over land to reduce energetic costs However during migration, these birds often have to cross water surfaces where thermal currents are weak; during these times, birds mainly use flapping （powered） flight which increases energy consumption and mortality risk. As a result, some species have evolved strategies to reduce the amount of time spent over water by taking extensive detours over land. In this paper, we con- ducted a meta-analysis of water-crossing tendencies in Afro-Palearctic migrating raptors in relation to their morphology, their flight performance, and their phylogenetic relationships. In particular, we considered the aspect ratio （calculated as the wing span squared divided by wing area）, the energetic cost of powered flight, and the maximum water crossing length regularly performed by adult birds. Our results suggest that energy consumption during powered flight predominately affects the ability of raptors to fly over water surfaces展开更多
基金Under the auspices of the Scientific Cooperation Project between Chinese Academy of Sciences and Jilin Province (No.K09P13)project of "Spring of Northeast China", Chinese Academy of Sciences (No. C08K23)
文摘From August to October in 2006,three times of field spectral measurements with a Field Spec FR spectroradiometer(Analytical Spectral Devices,Inc.,USA) were carried out in Shitoukoumen Reservoir,Jilin Province,Northeast China. Owing to the serious soil and water loss in the upstream,reflectance curves of the reservoir were characterized by high concentrations of total suspended matter(TSM) . Extending the spectral analysis to 1200nm in the near-infrared band,this research revealed an obvious reflectance peak around 1070nm which was caused by the strong backscattering of high TSM. The method of partial least squares(PLS) regression was applied to retrieving the TSM. Reflectance in two spectral bands,i.e.,675-948nm and 1029-1105nm,were used as variables to develop PLS models. Traditional linear regression,first derivative model and logarithmic model were also used for the comparison of different models. Results showed that the PLS model based on Rrs(675) -Rrs(948) gave out best results with high precision and stability. Although the PLS model based on Rrs(1029) -Rrs(1105) did not have an outstanding performance due to lots of noise,the reflectance peak in the near-infrared band was an important TSM feature and its efficient exploitation would have a considerable significance in TSM remote sensing.
文摘Raptors primarily use soaring-gliding flight which exploits thermals and ridge lifts over land to reduce energetic costs However during migration, these birds often have to cross water surfaces where thermal currents are weak; during these times, birds mainly use flapping （powered） flight which increases energy consumption and mortality risk. As a result, some species have evolved strategies to reduce the amount of time spent over water by taking extensive detours over land. In this paper, we con- ducted a meta-analysis of water-crossing tendencies in Afro-Palearctic migrating raptors in relation to their morphology, their flight performance, and their phylogenetic relationships. In particular, we considered the aspect ratio （calculated as the wing span squared divided by wing area）, the energetic cost of powered flight, and the maximum water crossing length regularly performed by adult birds. Our results suggest that energy consumption during powered flight predominately affects the ability of raptors to fly over water surfaces
