Tumbleweeds participate in a common seasonal biological process in temperate grasslands,creating hanging grass fences during the grass-withering season that result in distinct ecological phenomena.In this study,we add...Tumbleweeds participate in a common seasonal biological process in temperate grasslands,creating hanging grass fences during the grass-withering season that result in distinct ecological phenomena.In this study,we addressed the urgent need to understand and restore the degraded desert steppe in Central Mongolia,particularly considering the observed vegetation edge effects around hanging grass fences.Using field surveys conducted in 2019 and 2021 in the severely degraded desert steppe of Central Mongolia,we assessed vegetation parameters and soil physical and chemical properties influenced by hanging grass fences and identified the key environmental factors affecting vegetation changes.The results indicate that the edge effects of hanging grass fences led to changes in species distributions,resulting in significant differences in species composition between the desert steppe's interior and edge areas.Vegetation parameters and soil physical and chemical properties exhibited nonlinear responses to the edge effects of hanging grass fences,with changes in vegetation coverage,aboveground biomass,and soil sand content peaking at 26.5,16.5,and 6.5 m on the leeward side of hanging grass fences,respectively.In the absence of sand dune formation,the accumulation of soil organic carbon and available potassium were identified as crucial factors driving species composition and increasing vegetation coverage.Changes in species composition and plant density were primarily influenced by soil sand content,electrical conductivity,and sand accumulation thickness.These findings suggest that hanging grass fences have the potential to alter vegetation habitats,promote vegetation growth,and control soil erosion in the degraded desert steppe of Central Mongolia.Therefore,in the degraded desert steppe,the restoration potential of hanging grass fences during the enclosure process should be fully considered.展开更多
Environmental factors play vital roles in successful plantation and cultivation of tree seedlings.This study focuses on problems associated with reforestation under extreme continental climatic conditions.The objectiv...Environmental factors play vital roles in successful plantation and cultivation of tree seedlings.This study focuses on problems associated with reforestation under extreme continental climatic conditions.The objectives were to assess relative seedling performance(survival and growth)with respect to plantation age,and to analyze the influence of specific climatic factors during the early stages of Scots pine(Pinus sylvestris L.)plantations.The study was carried out in reforested areas of the Tujyin Nars region of northern Mongolia on six Scots pine plantations ranging from 5 to 10 years.In each of the six plantations,five 900 m^2 permanent sample plots were established and survival rates and growth performance measured annually over 7 years.Results show high variation in survival among the plantations(p<0.001,F=29.7).Seedling survival in the first year corresponded directly to the number of dry days in May.However,survival rate appeared to stabilize after the second year.The insignificant variation of height categories throughout the observation period indicated low competition among individuals.Two linear mixed-effect models show that height and radial growth were best explained by relative air humidity,which we consider to be a reliable indicator of site-specific water availability.Insufficient amounts and uneven distribution of rainfall pose a major threat during the first year of plantation establishment.Humidity and water availability are decisive factors for a successful seedling plantation.This highlights the impact of drought on forest plantations in northern Mongolia and the importance of developing climate resilient reforestation strategies.展开更多
This study presents thermokarst lake changes at seven different sites in the continuous and isolated permafrost zones in Mongolia. Lakes larger than 0.1 ha were analyzed using Corona KH-4, KH-4A and KH-4B (1962-1968),...This study presents thermokarst lake changes at seven different sites in the continuous and isolated permafrost zones in Mongolia. Lakes larger than 0.1 ha were analyzed using Corona KH-4, KH-4A and KH-4B (1962-1968), Landsat ETM + (1999-2001), and ALOS/AVNIR-2 (2006-2007) satellite imagery. Between 1962 and 2007, the total number and area of lakes increased by +21% (347 to 420), and +7% (3680 ha to 3936 ha) in the continuous permafrost zone, respectively. These changes correspond to the appearance of 85 new lakes (166 ha) during the last 45 years. In contrast, lakes in the isolated permafrost zone have decreased by –42% (118 to 68) in number and –12% (422 ha to 371 ha) in area from 1962 to 2007. The changes in lake area and number are likely attributed to shifts in climate regimes and local permafrost conditions. Since 1962, the mean annual air temperature and potential evapotranspiration have increased significantly in the northern continuous permafrost zone compared to the southern isolated permafrost zone. Due to ongoing atmospheric warming without any significant trend in annual precipitation, patches of ice-rich subsurface have thawed, and the number and area of lakes have accordingly developed in the continuous permafrost zone. Shrinking of thermokarst lakes in the isolated permafrost zone may be due to disappearing permafrost, deepening of the active layer, and increased water loss through surface evaporation and subsurface drainage.展开更多
Snow cover is an important water source for vegetation growth in arid and semi-arid areas,and grassland phenology provides valuable information on the response of terrestrial ecosystems to climate change.The Mongolian...Snow cover is an important water source for vegetation growth in arid and semi-arid areas,and grassland phenology provides valuable information on the response of terrestrial ecosystems to climate change.The Mongolian Plateau features both abundant snow cover resources and typical grassland ecosystems.In recent years,with the intensification of global climate change,the snow cover on the Mongolian Plateau has changed correspondingly,with resulting effects on vegetation growth.In this study,using MOD10A1 snow cover data and MOD13A1 Normalized Difference Vegetation Index(NDVI)data combined with remote sensing(RS)and geographic information system(GIS)techniques,we analyzed the spatiotemporal changes in snow cover and grassland phenology on the Mongolian Plateau from 2001 to 2018.The correlation analysis and grey relation analysis were used to determine the influence of snow cover parameters(snow cover fraction(SCF),snow cover duration(SCD),snow cover onset date(SCOD),and snow cover end date(SCED))on different types of grassland vegetation.The results showed wide snow cover areas,an early start time,a late end time,and a long duration of snow cover over the northern Mongolian Plateau.Additionally,a late start,an early end,and a short duration were observed for grassland phenology,but the southern area showed the opposite trend.The SCF decreased at an annual rate of 0.33%.The SCD was shortened at an annual rate of 0.57 d.The SCOD and SCED in more than half of the study area advanced at annual rates of 5.33 and 5.74 DOY(day of year),respectively.For grassland phenology,the start of the growing season(SOS)advanced at an annual rate of 0.03 DOY,the end of the growing season(EOS)was delayed at an annual rate of 0.14 DOY,and the length of the growing season(LOS)was prolonged at an annual rate of 0.17 d.The SCF,SCD,and SCED in the snow season were significantly positively correlated with the SOS and negatively correlated with the EOS and LOS.The SCOD was significantly negatively correlated with the SOS and positively correlated with the EOS and LOS.The SCD and SCF can directly affect the SOS of grassland vegetation,while the EOS and LOS were obviously influenced by the SCOD and SCED.This study provides a scientific basis for exploring the response trends of alpine vegetation to global climate change.展开更多
Long-term analyses of vegetation succession after catastrophic events are of high interest for an improved understanding of succession dynamics. However, in many studies such analyses were restricted to plot-based mea...Long-term analyses of vegetation succession after catastrophic events are of high interest for an improved understanding of succession dynamics. However, in many studies such analyses were restricted to plot-based measurements. Contrarily, spatially continuous observations of succession dynamics over extended areas and timeperiods are sparse. Here, we applied a change vector analysis(CVA) to investigate vegetation succession dynamics at Mount St. Helens after the great volcanic eruption in 1980 using Landsat. We additionally applied a supervised random forest classification using Sentinel-2 data to map the currently prevailing vegetation types. Change vector analysis was performed with the normalized difference vegetation index(NDVI) and the urban index(UI) for three subsequent decades after the eruption as well as for the whole observation time between 1984 and 2016. The influence of topography on the current vegetation distribution was examined by comparing altitude, slope angles and aspect values of vegetation classes derived by the random forest classification. WilcoxRank-Sum test was applied to test for significant differences between topographic properties of the vegetation classes inside and outside of the areas affected by the eruption. For the full time period, a total area of 516 km2 was identified as re-vegetated, whereas the area and magnitude of re-growing vegetation decreased during the three decades and migrated closer to the volcanic crater. Vegetation losses were mainly observed in regions unaffected by the eruption and related mostly to timber harvesting. The vegetation type classification reached a high overall accuracy of approximately 90%. 36 years after the eruption, coniferous and deciduous trees have established at formerly devastated areas dominating with a proportion of 66%, whereas shrubs are more abundant in riparian zones. Sparse vegetation dominates at regions very close to the crater. Elevation was found to have a great influence on the reestablishment and distribution of the vegetation classes within the devastated areas showing in almost all cases significant differences in altitude distribution. Slope was less important for the different classes-only representing significantly higher values for meadows, whereas aspect seems to have no notable influence on the reestablishment of vegetation at Mount St. Helens. We conclude that major vegetation succession dynamics after catastrophic events can be assessed and characterized over large areas from freely available remote sensing data and hence contribute to an improved understanding of succession dynamics.展开更多
Cistanche deserticola is an important medicinal plant in Mongolia.Despite its significant role in local healing systems,little traditional knowledge had been reported.The present study investigated folk names of C.des...Cistanche deserticola is an important medicinal plant in Mongolia.Despite its significant role in local healing systems,little traditional knowledge had been reported.The present study investigated folk names of C.deserticola and other species of the same community in Umnugobi Province,South Gobi region of Mongolia,based on ethnobotanical approaches.The high correspondence between folk names and scientific names of plant species occurring in Cistanche-associated community shows the scientific meaning of folk nomenclature and classification in Mongolia.The Mongolian and folk names of plants were formed on the basis of observations and understanding of wild plants including their morphology,phenology and traditional uses as well.Results from this study will support the conservation of C.deserticola itself,a rare and endangered plant species listed in the Monglian Red Data Book.Our documentation of folk nomenclature based on 96 plant species in the Cistanche community,as a part of traditional knowledge associated with biodiversity,will be very helpful for making strategy of plant biodiversity conservation in Mongolia.展开更多
The Uvs Lake Basin in western Mongolia is a natural world heritage site and is known for its diversity in landscape and wildlife.Recently,investigative research has shown that the protected pristine ecotone is sufferi...The Uvs Lake Basin in western Mongolia is a natural world heritage site and is known for its diversity in landscape and wildlife.Recently,investigative research has shown that the protected pristine ecotone is suffering land degradation due to global warming.In order to obtain evidence of the changes over a long-term time scale,serial multi-temporal Landsat images obtained between 1995 and 2015 were used to classify land cover and land cover changes over the Basin ecoregion using a machine learning classification technique,support vector machine.Results showed that the forest land area in 1995 was 1888.48 km^2 which was equivalent to 7.48%of the total area of the study site.The forest area showed considerable decrease by 301.36 km^2 during the first decade(1995–2004)and 155.81 km^2 during second decade(2004–2015).A total of 457.17 km^2 or 24.21%of the forest land has been developed,most being changed into grassland.The major driver of such changes was illegal logging,forest fire,and pest damage.However grassland was changed primarily into bare land during the two decades.The area of glacier was decreased and primarily changed into water body.In contrast,the area of sand in the Basin ecoregion increased dramatically from 65.20 km^2 in 1995 to 318.33 km^2 in 2015 the increase being mostly from the transition of bare land.In summary,the drivers of the significant decrease of greenness coverage and increase of sand/bare land areas were the interaction of complicated disturbances in both anthropogenic and natural factors,in which logging,grazing,wind erosion,and global warming were the key causes.展开更多
Global maps of bioclimatic variables currently exist only at very coarse spatial resolution(e.g.WorldClim).For ecological studies requiring higher resolved information,this spatial resolution is often insufficient.The...Global maps of bioclimatic variables currently exist only at very coarse spatial resolution(e.g.WorldClim).For ecological studies requiring higher resolved information,this spatial resolution is often insufficient.The aim of this study is to estimate important bioclimatic variables of Mongolia from Earth Observation(EO)data at a higher spatial resolution of 1 km.The analysis used two different satellite time series data sets:land surface temperature(LST)from Moderate Resolution Imaging Spectroradiometer(MODIS),and precipitation(P)from Climate Hazards Group Infrared Precipitation with Stations(CHIRPS).Monthly maximum,mean,and minimum air temperature were estimated from Terra MODIS satellite(collection 6)LST time series product using the random forest(RF)regression model.Monthly total precipitation data were obtained from CHIRPS version 2.0.Based on this primary data,spatial maps of 19 bioclimatic variables at a spatial resolution of 1 km were generated,representing the period 2002-2017.We tested the relationship between estimated bioclimatic variables(SatClim)and WorldClim bioclimatic variables version 2.0(WorldClim)using determination coefficient(R^(2)),root mean square error(RMSE),and normalized root mean square error(nRMSE)and found overall good agreement.Among the set of 19 WorldClim bioclimatic variables,17 were estimated with a coefficient of determination(R^(2))higher than 0.7 and normalized RMSE(nRMSE)lower than 8%,confirming that the spatial pattern and value ranges can be retrieved from satellite data with much higher spatial resolution compared to WorldClim.Only the two bioclimatic variables related to temperature extremes(i.e.,annual mean diurnal range and isothermality)were modeled with only moderate accuracy(R^(2) of about 0.4 with nRMSE of about 11%).Generally,precipitation-related bioclimatic variables were closer correlated with WorldClim compared to temperature-related bioclimatic variables.The overall success of the modeling was attributed to the fact that satellite-derived data are well suited to generated spatial fields of precipitation and temperature variables,especially at high altitudes and high latitudes.As a consequence of the successful retrieval of the bioclimatic variables at 1 km spatial resolution,we are confident that the estimated 19 bioclimatic variables will be very useful for a range of applications,including species distribution modeling.展开更多
基金supported by the Third Xinjiang Scientific Expedition and Research Program(2021xjkk0305)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA2003020201)the Key Intergovernmental Projects for International Scientific and Technological Innovation Cooperation of the National Key Research and Development Program of China(2017YFE0109200).
文摘Tumbleweeds participate in a common seasonal biological process in temperate grasslands,creating hanging grass fences during the grass-withering season that result in distinct ecological phenomena.In this study,we addressed the urgent need to understand and restore the degraded desert steppe in Central Mongolia,particularly considering the observed vegetation edge effects around hanging grass fences.Using field surveys conducted in 2019 and 2021 in the severely degraded desert steppe of Central Mongolia,we assessed vegetation parameters and soil physical and chemical properties influenced by hanging grass fences and identified the key environmental factors affecting vegetation changes.The results indicate that the edge effects of hanging grass fences led to changes in species distributions,resulting in significant differences in species composition between the desert steppe's interior and edge areas.Vegetation parameters and soil physical and chemical properties exhibited nonlinear responses to the edge effects of hanging grass fences,with changes in vegetation coverage,aboveground biomass,and soil sand content peaking at 26.5,16.5,and 6.5 m on the leeward side of hanging grass fences,respectively.In the absence of sand dune formation,the accumulation of soil organic carbon and available potassium were identified as crucial factors driving species composition and increasing vegetation coverage.Changes in species composition and plant density were primarily influenced by soil sand content,electrical conductivity,and sand accumulation thickness.These findings suggest that hanging grass fences have the potential to alter vegetation habitats,promote vegetation growth,and control soil erosion in the degraded desert steppe of Central Mongolia.Therefore,in the degraded desert steppe,the restoration potential of hanging grass fences during the enclosure process should be fully considered.
基金supported by the Partnerships for Enhanced Engagement in Research(PEER)Science Cycle 2 Grant#296’Building research and teaching capacity to aid climate change and natural resource management at the National University of Mongolia(NUM)’
文摘Environmental factors play vital roles in successful plantation and cultivation of tree seedlings.This study focuses on problems associated with reforestation under extreme continental climatic conditions.The objectives were to assess relative seedling performance(survival and growth)with respect to plantation age,and to analyze the influence of specific climatic factors during the early stages of Scots pine(Pinus sylvestris L.)plantations.The study was carried out in reforested areas of the Tujyin Nars region of northern Mongolia on six Scots pine plantations ranging from 5 to 10 years.In each of the six plantations,five 900 m^2 permanent sample plots were established and survival rates and growth performance measured annually over 7 years.Results show high variation in survival among the plantations(p<0.001,F=29.7).Seedling survival in the first year corresponded directly to the number of dry days in May.However,survival rate appeared to stabilize after the second year.The insignificant variation of height categories throughout the observation period indicated low competition among individuals.Two linear mixed-effect models show that height and radial growth were best explained by relative air humidity,which we consider to be a reliable indicator of site-specific water availability.Insufficient amounts and uneven distribution of rainfall pose a major threat during the first year of plantation establishment.Humidity and water availability are decisive factors for a successful seedling plantation.This highlights the impact of drought on forest plantations in northern Mongolia and the importance of developing climate resilient reforestation strategies.
文摘This study presents thermokarst lake changes at seven different sites in the continuous and isolated permafrost zones in Mongolia. Lakes larger than 0.1 ha were analyzed using Corona KH-4, KH-4A and KH-4B (1962-1968), Landsat ETM + (1999-2001), and ALOS/AVNIR-2 (2006-2007) satellite imagery. Between 1962 and 2007, the total number and area of lakes increased by +21% (347 to 420), and +7% (3680 ha to 3936 ha) in the continuous permafrost zone, respectively. These changes correspond to the appearance of 85 new lakes (166 ha) during the last 45 years. In contrast, lakes in the isolated permafrost zone have decreased by –42% (118 to 68) in number and –12% (422 ha to 371 ha) in area from 1962 to 2007. The changes in lake area and number are likely attributed to shifts in climate regimes and local permafrost conditions. Since 1962, the mean annual air temperature and potential evapotranspiration have increased significantly in the northern continuous permafrost zone compared to the southern isolated permafrost zone. Due to ongoing atmospheric warming without any significant trend in annual precipitation, patches of ice-rich subsurface have thawed, and the number and area of lakes have accordingly developed in the continuous permafrost zone. Shrinking of thermokarst lakes in the isolated permafrost zone may be due to disappearing permafrost, deepening of the active layer, and increased water loss through surface evaporation and subsurface drainage.
基金supported by the National Natural Science Foundation of China(41861014)the Natural Science Foundation of Inner Mongolia Autonomous Region,China(2020BS03042,2020BS04009)the Scientific Research Start-up Fund Projects of Introduced Talents(5909001803,1004031904).
文摘Snow cover is an important water source for vegetation growth in arid and semi-arid areas,and grassland phenology provides valuable information on the response of terrestrial ecosystems to climate change.The Mongolian Plateau features both abundant snow cover resources and typical grassland ecosystems.In recent years,with the intensification of global climate change,the snow cover on the Mongolian Plateau has changed correspondingly,with resulting effects on vegetation growth.In this study,using MOD10A1 snow cover data and MOD13A1 Normalized Difference Vegetation Index(NDVI)data combined with remote sensing(RS)and geographic information system(GIS)techniques,we analyzed the spatiotemporal changes in snow cover and grassland phenology on the Mongolian Plateau from 2001 to 2018.The correlation analysis and grey relation analysis were used to determine the influence of snow cover parameters(snow cover fraction(SCF),snow cover duration(SCD),snow cover onset date(SCOD),and snow cover end date(SCED))on different types of grassland vegetation.The results showed wide snow cover areas,an early start time,a late end time,and a long duration of snow cover over the northern Mongolian Plateau.Additionally,a late start,an early end,and a short duration were observed for grassland phenology,but the southern area showed the opposite trend.The SCF decreased at an annual rate of 0.33%.The SCD was shortened at an annual rate of 0.57 d.The SCOD and SCED in more than half of the study area advanced at annual rates of 5.33 and 5.74 DOY(day of year),respectively.For grassland phenology,the start of the growing season(SOS)advanced at an annual rate of 0.03 DOY,the end of the growing season(EOS)was delayed at an annual rate of 0.14 DOY,and the length of the growing season(LOS)was prolonged at an annual rate of 0.17 d.The SCF,SCD,and SCED in the snow season were significantly positively correlated with the SOS and negatively correlated with the EOS and LOS.The SCOD was significantly negatively correlated with the SOS and positively correlated with the EOS and LOS.The SCD and SCF can directly affect the SOS of grassland vegetation,while the EOS and LOS were obviously influenced by the SCOD and SCED.This study provides a scientific basis for exploring the response trends of alpine vegetation to global climate change.
文摘Long-term analyses of vegetation succession after catastrophic events are of high interest for an improved understanding of succession dynamics. However, in many studies such analyses were restricted to plot-based measurements. Contrarily, spatially continuous observations of succession dynamics over extended areas and timeperiods are sparse. Here, we applied a change vector analysis(CVA) to investigate vegetation succession dynamics at Mount St. Helens after the great volcanic eruption in 1980 using Landsat. We additionally applied a supervised random forest classification using Sentinel-2 data to map the currently prevailing vegetation types. Change vector analysis was performed with the normalized difference vegetation index(NDVI) and the urban index(UI) for three subsequent decades after the eruption as well as for the whole observation time between 1984 and 2016. The influence of topography on the current vegetation distribution was examined by comparing altitude, slope angles and aspect values of vegetation classes derived by the random forest classification. WilcoxRank-Sum test was applied to test for significant differences between topographic properties of the vegetation classes inside and outside of the areas affected by the eruption. For the full time period, a total area of 516 km2 was identified as re-vegetated, whereas the area and magnitude of re-growing vegetation decreased during the three decades and migrated closer to the volcanic crater. Vegetation losses were mainly observed in regions unaffected by the eruption and related mostly to timber harvesting. The vegetation type classification reached a high overall accuracy of approximately 90%. 36 years after the eruption, coniferous and deciduous trees have established at formerly devastated areas dominating with a proportion of 66%, whereas shrubs are more abundant in riparian zones. Sparse vegetation dominates at regions very close to the crater. Elevation was found to have a great influence on the reestablishment and distribution of the vegetation classes within the devastated areas showing in almost all cases significant differences in altitude distribution. Slope was less important for the different classes-only representing significantly higher values for meadows, whereas aspect seems to have no notable influence on the reestablishment of vegetation at Mount St. Helens. We conclude that major vegetation succession dynamics after catastrophic events can be assessed and characterized over large areas from freely available remote sensing data and hence contribute to an improved understanding of succession dynamics.
基金This research was supported by the National Natural Science Foundation of China(31761143001,31870316)the Natural Science Foundation of Beijing(7202109)+4 种基金Minzu University of China(KLEMZZ201904,KLEM-ZZ201906,YLDXXK201819)the Ministry of Ecology and Environment of China(2019HB2096001006)Jiansheng Fresh Herb Medicine R&D Foundation(JSYY-20190101-043)the Ministry of Education of China(B08044)Colleagues and Dr.Bayartungalag from the institute of Geography and Geoecology,Mongolian Academy of Sciences provided assistances in the field surveys.Yingjie Song at Minzu University of China provided useful comments.We are grateful to all of them.
文摘Cistanche deserticola is an important medicinal plant in Mongolia.Despite its significant role in local healing systems,little traditional knowledge had been reported.The present study investigated folk names of C.deserticola and other species of the same community in Umnugobi Province,South Gobi region of Mongolia,based on ethnobotanical approaches.The high correspondence between folk names and scientific names of plant species occurring in Cistanche-associated community shows the scientific meaning of folk nomenclature and classification in Mongolia.The Mongolian and folk names of plants were formed on the basis of observations and understanding of wild plants including their morphology,phenology and traditional uses as well.Results from this study will support the conservation of C.deserticola itself,a rare and endangered plant species listed in the Monglian Red Data Book.Our documentation of folk nomenclature based on 96 plant species in the Cistanche community,as a part of traditional knowledge associated with biodiversity,will be very helpful for making strategy of plant biodiversity conservation in Mongolia.
文摘The Uvs Lake Basin in western Mongolia is a natural world heritage site and is known for its diversity in landscape and wildlife.Recently,investigative research has shown that the protected pristine ecotone is suffering land degradation due to global warming.In order to obtain evidence of the changes over a long-term time scale,serial multi-temporal Landsat images obtained between 1995 and 2015 were used to classify land cover and land cover changes over the Basin ecoregion using a machine learning classification technique,support vector machine.Results showed that the forest land area in 1995 was 1888.48 km^2 which was equivalent to 7.48%of the total area of the study site.The forest area showed considerable decrease by 301.36 km^2 during the first decade(1995–2004)and 155.81 km^2 during second decade(2004–2015).A total of 457.17 km^2 or 24.21%of the forest land has been developed,most being changed into grassland.The major driver of such changes was illegal logging,forest fire,and pest damage.However grassland was changed primarily into bare land during the two decades.The area of glacier was decreased and primarily changed into water body.In contrast,the area of sand in the Basin ecoregion increased dramatically from 65.20 km^2 in 1995 to 318.33 km^2 in 2015 the increase being mostly from the transition of bare land.In summary,the drivers of the significant decrease of greenness coverage and increase of sand/bare land areas were the interaction of complicated disturbances in both anthropogenic and natural factors,in which logging,grazing,wind erosion,and global warming were the key causes.
基金The authors appreciate the providers of temperature and precipitation products to allow us to download and use these data sets.We thank two anonymous referees for their comments on the manuscript.
文摘Global maps of bioclimatic variables currently exist only at very coarse spatial resolution(e.g.WorldClim).For ecological studies requiring higher resolved information,this spatial resolution is often insufficient.The aim of this study is to estimate important bioclimatic variables of Mongolia from Earth Observation(EO)data at a higher spatial resolution of 1 km.The analysis used two different satellite time series data sets:land surface temperature(LST)from Moderate Resolution Imaging Spectroradiometer(MODIS),and precipitation(P)from Climate Hazards Group Infrared Precipitation with Stations(CHIRPS).Monthly maximum,mean,and minimum air temperature were estimated from Terra MODIS satellite(collection 6)LST time series product using the random forest(RF)regression model.Monthly total precipitation data were obtained from CHIRPS version 2.0.Based on this primary data,spatial maps of 19 bioclimatic variables at a spatial resolution of 1 km were generated,representing the period 2002-2017.We tested the relationship between estimated bioclimatic variables(SatClim)and WorldClim bioclimatic variables version 2.0(WorldClim)using determination coefficient(R^(2)),root mean square error(RMSE),and normalized root mean square error(nRMSE)and found overall good agreement.Among the set of 19 WorldClim bioclimatic variables,17 were estimated with a coefficient of determination(R^(2))higher than 0.7 and normalized RMSE(nRMSE)lower than 8%,confirming that the spatial pattern and value ranges can be retrieved from satellite data with much higher spatial resolution compared to WorldClim.Only the two bioclimatic variables related to temperature extremes(i.e.,annual mean diurnal range and isothermality)were modeled with only moderate accuracy(R^(2) of about 0.4 with nRMSE of about 11%).Generally,precipitation-related bioclimatic variables were closer correlated with WorldClim compared to temperature-related bioclimatic variables.The overall success of the modeling was attributed to the fact that satellite-derived data are well suited to generated spatial fields of precipitation and temperature variables,especially at high altitudes and high latitudes.As a consequence of the successful retrieval of the bioclimatic variables at 1 km spatial resolution,we are confident that the estimated 19 bioclimatic variables will be very useful for a range of applications,including species distribution modeling.
