The recurrent extreme El Niño events are commonly linked to reduced vegetation growth and the land carbon sink over many but discrete regions of the Northern Hemisphere(NH).However,we reported here a pervasive an...The recurrent extreme El Niño events are commonly linked to reduced vegetation growth and the land carbon sink over many but discrete regions of the Northern Hemisphere(NH).However,we reported here a pervasive and continuous vegetation greening and no weakened land carbon sink in the maturation phase of the 2015/2016 El Niño event over the NH(mainly in the extra-tropics),based on multiple evidences from remote sensing observations,global ecosystem model simulations and atmospheric CO_(2)inversions.We discovered a significant compensation effect of the enhanced vegetation growth in spring on subsequent summer/autumn vegetation growth that sustained vegetation greening and led to a slight increase in the land carbon sink over the spring and summer of 2015(average increases of 23.34%and 0.63%in net ecosystem exchange from two independent datasets relative to a 5-years average before the El Niño event,respectively)and spring of 2016(6.82%),especially in the extra-tropics of the NH,where the water supply during the pre-growing-season(November of the previous year to March of the current year)had a positive anomaly.This seasonal compensation effect was much stronger than that in 1997 and 1998 and significantly alleviated the adverse impacts of the 2015/2016 El Niño event on vegetation growth during its maturation phase.The legacy effect of water supply during the pre-growing-season on subsequent vegetation growth lasted up to approximately six months.Our findings highlight the role of seasonal compensation effects on mediating the land carbon sink in response to episodic extreme El Niño events.展开更多
Hyperspectral reflectance contains valuable information about leaf functional traits,which can indicate a plant's physiological status.Therefore,using hyperspectral reflectance for high-throughput phenotyping of f...Hyperspectral reflectance contains valuable information about leaf functional traits,which can indicate a plant's physiological status.Therefore,using hyperspectral reflectance for high-throughput phenotyping of foliar traits could be a powerful tool for tree breeders and nursery practitioners to distinguish and select seedlings with desired adaptation potential to local environments.We evaluated the use of 2 nondestructive methods(i.e.,leaf and proximal/canopy)measuring hyperspectral reflectance in the 350-to 2,500-nm range for phenotyping on 1,788 individual Scots pine seedlings belonging to lowland and upland ecotypes of 3 different local populations from the Czech Republic.Leaf-level measurements were collected using a spectroradiometer and a contact probe with an internal light source to measure the biconical reflectance factor of a sample of needles placed on a black background in the contact probe field of view.The proximal canopy measurements were collected under natural solar light,using the same spectroradiometer with fiber optical cable to collect data on individual seedlings'hemispherical conical reflectance factor.The latter method was highly susceptible to changes in incoming radiation.Both spectral datasets showed statistically significant differences among Scots pine populations in the whole spectral range.Moreover,using random forest and support vector machine learning algorithms,the proximal data obtained from the top of the seedlings offered up to 83%accuracy in predicting 3 different Scots pine populations.We conclude that both approaches are viable for hyperspectral phenotyping to disentangle the phenotypic and the underlying genetic variation within Scots pine seedlings.展开更多
Dryland degradation has long been recognized at regional,national,and global scales,yet there are no objective assessments of its location and severity.An assessment of reductions in net primary production(NPP)due to ...Dryland degradation has long been recognized at regional,national,and global scales,yet there are no objective assessments of its location and severity.An assessment of reductions in net primary production(NPP)due to dry land degradation in the southwestern United States is reported.The local NPP scaling(LNS)approach was applied to map the extent and magnitude of degrada tion.LNS seeks to identifty reference sites in which there is no degradation that can be used as a standard for comparison with other sites that share the same environment,except for degradation.Twelve years were analyzed(2000--2011),using Normalized Difference Vegetation Index(NDVI)data(250 m)from the Moderate Resolution Imaging Spectroradiometer(MODIS)satellite-borne multispectral sensor.The results indicated that the total NPP reductions in the study area were about35.9±4.7Tg C/yr,which equates to 0.31±0.04 Mg C·ha^(-1)· yr^(-1).The NPP reductions in grassland-savanna and livestock grazing areas were large and mostly consistent between years in spite of large variations in overall NPP caused by differences in land-use,interannual variations in rainfall,and other aspects of weather.In comparison with other cover types,forested land generally had higher NPP reduction per unit area.The maps also enable attribution of degradation from the finest management units to entire agencies,such as the Bureau of Land Management,which had 50%less production per unit area than the U.S.Forest Service.The degradation within Native American land was low with total NPP reduction of about 2.41±0.24 Tg C/yr and unit area reduction of productivity of just 0.21±0.02 Mg C·ha^(-1)·yr^(-1),yet the percent reduction from potential was in equivalence with other land management agencies.展开更多
Data from the Moderate Resolution Imaging Spectro-radiometer(MODIS)on-board the Earth Observing System Terra and Aqua satellites are processed using a land water mask to determine when an algorithm no longer needs to ...Data from the Moderate Resolution Imaging Spectro-radiometer(MODIS)on-board the Earth Observing System Terra and Aqua satellites are processed using a land water mask to determine when an algorithm no longer needs to be run or when an algorithm needs to follow a different pathway.Entering the fourth reprocessing(Collection 6(C6))the MODIS team replaced the 1 km water mask with a 500 m water mask for improved representation of the continental surfaces.The new water mask represents more small water bodies for an overall increase in water surface from 1%to 2%of the continental surface.While this is still a small fraction of the overall global surface area the increase is more dramatic in certain areas such as the Arctic and Boreal regions where there are dramatic increases in water surface area in the new mask.MODIS products generated by the on-going C6 reprocessing using the new land water mask show significant impact in areas with high concentrations of change in the land water mask.Here differences between the Collection 5(C5)and C6 water masks and the impact of these differences on the MOD04 aerosol product and the MOD11 land surface temperature product are shown.展开更多
Reliablemicrostructuremeasurement of snow is a requirement for microwave radiative transfer model validation.Snow specific surface area(SSA)can be measured using stereological methods,in which snow samples are cast in...Reliablemicrostructuremeasurement of snow is a requirement for microwave radiative transfer model validation.Snow specific surface area(SSA)can be measured using stereological methods,in which snow samples are cast in the field and photographed in the laboratory.Processing stereology photographs manually by counting intersections of test cycloids with air-ice boundaries reduces the problems in binary segmentation.This paper is a case study to evaluate the repeatability of the manually stereology interpretation by two independent research groups.We further assessed how uncertainty in snow SSA influences simulated brightness temperature(TB)driven by the Microwave Emission Model of Layered Snowpacks(MEMLS),and how stereology compares to Near Infrared(NIR)camera and hand lens.Data was obtained from two alpine snow profiles from Steamboat Springs,Colorado.Results showed that stereological SSA values measured by two groups are highly consistent,and the ground radiometer measured T_(B)at 19 and 37 GHz was successfully predicted(RMSE<3.8 K);simulations using NIR SSA and hand-lens geometric grain size(Dg)measurements have larger errors.This conclusion was not sensitive to uncertainty in the free parameters of TB modeling.展开更多
基金This study was financially supported by the National Key Research and Development Program of China(Grant No.2022YFF0801802)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0306)+2 种基金the National Natural Science Foundation of China(Grant No.42171050)the China Postdoctoral Science Foundation(Grant No.2023M730281)the State Key Laboratory of Earth Surface Processes and Resource Ecology of Beijing Normal University(Grant No.2023-KF-07).
文摘The recurrent extreme El Niño events are commonly linked to reduced vegetation growth and the land carbon sink over many but discrete regions of the Northern Hemisphere(NH).However,we reported here a pervasive and continuous vegetation greening and no weakened land carbon sink in the maturation phase of the 2015/2016 El Niño event over the NH(mainly in the extra-tropics),based on multiple evidences from remote sensing observations,global ecosystem model simulations and atmospheric CO_(2)inversions.We discovered a significant compensation effect of the enhanced vegetation growth in spring on subsequent summer/autumn vegetation growth that sustained vegetation greening and led to a slight increase in the land carbon sink over the spring and summer of 2015(average increases of 23.34%and 0.63%in net ecosystem exchange from two independent datasets relative to a 5-years average before the El Niño event,respectively)and spring of 2016(6.82%),especially in the extra-tropics of the NH,where the water supply during the pre-growing-season(November of the previous year to March of the current year)had a positive anomaly.This seasonal compensation effect was much stronger than that in 1997 and 1998 and significantly alleviated the adverse impacts of the 2015/2016 El Niño event on vegetation growth during its maturation phase.The legacy effect of water supply during the pre-growing-season on subsequent vegetation growth lasted up to approximately six months.Our findings highlight the role of seasonal compensation effects on mediating the land carbon sink in response to episodic extreme El Niño events.
基金funded mainly by the Ministry of Education,Youth and Sports of the Czech Republic,scheme INTER-EXCELLENCE,INTER-ACTION,grant number LTA-USA19113,titled“Genetic variability of hyper-spectral reflectance in Scots pine ecotypes for selection of drought-resistant individuals”.This project was coordinated with U.S.partners:P.Campbell and J.Brawnerfunding from the European Union's Horizon Europe Research and Innovation Programme under grant agreement no:101081774-OptFORESTS+1 种基金supported by NASA,LCLUC Program NNH17ZDA001N-LCLUC,grant no:80NSS-C18K0337,titled“Prototyping MuSLI canopy chlorophyl content for assessment of vegetation function and productivity”supported by the Academy of Finland Flagship on Photonics Research and Innovation(PREIN,320166)
文摘Hyperspectral reflectance contains valuable information about leaf functional traits,which can indicate a plant's physiological status.Therefore,using hyperspectral reflectance for high-throughput phenotyping of foliar traits could be a powerful tool for tree breeders and nursery practitioners to distinguish and select seedlings with desired adaptation potential to local environments.We evaluated the use of 2 nondestructive methods(i.e.,leaf and proximal/canopy)measuring hyperspectral reflectance in the 350-to 2,500-nm range for phenotyping on 1,788 individual Scots pine seedlings belonging to lowland and upland ecotypes of 3 different local populations from the Czech Republic.Leaf-level measurements were collected using a spectroradiometer and a contact probe with an internal light source to measure the biconical reflectance factor of a sample of needles placed on a black background in the contact probe field of view.The proximal canopy measurements were collected under natural solar light,using the same spectroradiometer with fiber optical cable to collect data on individual seedlings'hemispherical conical reflectance factor.The latter method was highly susceptible to changes in incoming radiation.Both spectral datasets showed statistically significant differences among Scots pine populations in the whole spectral range.Moreover,using random forest and support vector machine learning algorithms,the proximal data obtained from the top of the seedlings offered up to 83%accuracy in predicting 3 different Scots pine populations.We conclude that both approaches are viable for hyperspectral phenotyping to disentangle the phenotypic and the underlying genetic variation within Scots pine seedlings.
文摘Dryland degradation has long been recognized at regional,national,and global scales,yet there are no objective assessments of its location and severity.An assessment of reductions in net primary production(NPP)due to dry land degradation in the southwestern United States is reported.The local NPP scaling(LNS)approach was applied to map the extent and magnitude of degrada tion.LNS seeks to identifty reference sites in which there is no degradation that can be used as a standard for comparison with other sites that share the same environment,except for degradation.Twelve years were analyzed(2000--2011),using Normalized Difference Vegetation Index(NDVI)data(250 m)from the Moderate Resolution Imaging Spectroradiometer(MODIS)satellite-borne multispectral sensor.The results indicated that the total NPP reductions in the study area were about35.9±4.7Tg C/yr,which equates to 0.31±0.04 Mg C·ha^(-1)· yr^(-1).The NPP reductions in grassland-savanna and livestock grazing areas were large and mostly consistent between years in spite of large variations in overall NPP caused by differences in land-use,interannual variations in rainfall,and other aspects of weather.In comparison with other cover types,forested land generally had higher NPP reduction per unit area.The maps also enable attribution of degradation from the finest management units to entire agencies,such as the Bureau of Land Management,which had 50%less production per unit area than the U.S.Forest Service.The degradation within Native American land was low with total NPP reduction of about 2.41±0.24 Tg C/yr and unit area reduction of productivity of just 0.21±0.02 Mg C·ha^(-1)·yr^(-1),yet the percent reduction from potential was in equivalence with other land management agencies.
基金funded in part by National Aeronautics and Space Administration(NASA)Terrestrial Ecology program Grant/Cooperative Agreement Number:#NNX08AT97ANASA MEaSURES program Grant/Cooperative Agreement Number:#NNX13AJ35ANASA EOS Grant/Cooperative Agreement Number:#NNX14AJ33G.
文摘Data from the Moderate Resolution Imaging Spectro-radiometer(MODIS)on-board the Earth Observing System Terra and Aqua satellites are processed using a land water mask to determine when an algorithm no longer needs to be run or when an algorithm needs to follow a different pathway.Entering the fourth reprocessing(Collection 6(C6))the MODIS team replaced the 1 km water mask with a 500 m water mask for improved representation of the continental surfaces.The new water mask represents more small water bodies for an overall increase in water surface from 1%to 2%of the continental surface.While this is still a small fraction of the overall global surface area the increase is more dramatic in certain areas such as the Arctic and Boreal regions where there are dramatic increases in water surface area in the new mask.MODIS products generated by the on-going C6 reprocessing using the new land water mask show significant impact in areas with high concentrations of change in the land water mask.Here differences between the Collection 5(C5)and C6 water masks and the impact of these differences on the MOD04 aerosol product and the MOD11 land surface temperature product are shown.
基金supported by NASA Terrestrial Hydrology Program[grant number NNX09AM10G]Strategic Priority Research Program of Chinese Academy of Sciences[grant number XDA20100300].
文摘Reliablemicrostructuremeasurement of snow is a requirement for microwave radiative transfer model validation.Snow specific surface area(SSA)can be measured using stereological methods,in which snow samples are cast in the field and photographed in the laboratory.Processing stereology photographs manually by counting intersections of test cycloids with air-ice boundaries reduces the problems in binary segmentation.This paper is a case study to evaluate the repeatability of the manually stereology interpretation by two independent research groups.We further assessed how uncertainty in snow SSA influences simulated brightness temperature(TB)driven by the Microwave Emission Model of Layered Snowpacks(MEMLS),and how stereology compares to Near Infrared(NIR)camera and hand lens.Data was obtained from two alpine snow profiles from Steamboat Springs,Colorado.Results showed that stereological SSA values measured by two groups are highly consistent,and the ground radiometer measured T_(B)at 19 and 37 GHz was successfully predicted(RMSE<3.8 K);simulations using NIR SSA and hand-lens geometric grain size(Dg)measurements have larger errors.This conclusion was not sensitive to uncertainty in the free parameters of TB modeling.