Endemism of lineages lies at the core of understanding variation in community composition among geographic regions because it reflects how speciation,extinction,and dispersal have influenced current distributions.Here...Endemism of lineages lies at the core of understanding variation in community composition among geographic regions because it reflects how speciation,extinction,and dispersal have influenced current distributions.Here,we investigated geographic patterns and ecological drivers of taxonomic and phylogenetic endemism of angiosperm genera across the world.We identify centers of paleo-endemism and neo-endemism of angiosperm genera,and show that they are mostly located in the Southern Hemisphere in tropical and subtropical regions,particularly in Asia and Australia.Different categories of phylogenetic endemism centers can be differentiated using current climate conditions.Current climate,historical climate change,and geographic variables together explained~80%of global variation in taxonomic and phylogenetic endemism,while 42-46%,1%,and 15%were independently explained by these three types of variables,respectively.Thus our findings show that past climate change,current climate,and geography act together in shaping endemism,which are consistent with the findings of previous studies that higher temperature and topographic heterogeneity promote endemism.Our study showed that many centers of phylogenetic endemism of angiosperms,including regions in Amazonia,Venezuela,and west-central tropical Africa that have not previously been identified as biodiversity hotspots,are missed by taxon-based measures of endemism,indicating the importance of including evolutionary history in biodiversity assessment.展开更多
Predicting the spatial distribution of soil moisture is an important hydrological question. We measured the spatial distribution of surface soil moisture (upper 6 cm) using an Amplitude Domain Reflectometry sensor at ...Predicting the spatial distribution of soil moisture is an important hydrological question. We measured the spatial distribution of surface soil moisture (upper 6 cm) using an Amplitude Domain Reflectometry sensor at the plot scale (2 × 2 m) and small catchment scale (0.84 ha) in a temperate forest. The spatial variation of soil water content was higher during dry conditions than that during wet conditions. Results indicated 3.1 samples at the plot scale were sufficient to estimate mean soil water content when the precision was 0.1. Soil water content increased with increasing topographic index (TI) and soil-topographic index (STI) at the small catchment scale. The correlation between soil water content and TI was higher than that between soil water content and STI. This suggests that topography is more important for estimating surface soil moisture than soil depth as formation of surface soil moisture occurs at ≤6 cm.展开更多
Based on the DEM raster image data with a resolution of 60 m×60 m in the Sanjiangyuan region,the topographic heterogeneity in the Sanjiangyuan region was analyzed by calculating and processing the topographic rel...Based on the DEM raster image data with a resolution of 60 m×60 m in the Sanjiangyuan region,the topographic heterogeneity in the Sanjiangyuan region was analyzed by calculating and processing the topographic relief,elevation standard deviation,terrain heterogeneity and surface roughness indexes.The results show that the overall terrain elevation of the Sanjiangyuan area is high,and the surface undulations are large.The southern and southeastern parts of the region are the places with the most dramatic terrain changes.The absolute values of terrain undulations,elevation standard deviation and surface roughness are large.In the central and western regions,the terrain change is small,the relief degree is small,the elevation standard deviation and the surface roughness are small.展开更多
The ecological environment of the Three-River Headwater Region is primitive and unique,and sensitive and complex to external influences.The Three-River Headwater Region is the largest nature reserve in China,and is al...The ecological environment of the Three-River Headwater Region is primitive and unique,and sensitive and complex to external influences.The Three-River Headwater Region is the largest nature reserve in China,and is also a nature reserve with the highest concentration of biodiversity in the world's high-altitude areas,so the protection of ecological diversity in this region is particularly important.Ecological diversity is the material basis on which the entire humanity depends to survive and develop.It not only provides humans with basic needs such as food,energy and materials,and is also extremely important for maintaining ecological balance,regulating the climate and promoting the sustainable development of the region.Studying the topographical heterogeneity of the region is first of all a true grasp of the topography of the region,which has certain guiding significance for people's production and life.In addition,studying the impact of topographical heterogeneity on the climate of the region will help to study the formation and variation of regional climate.展开更多
文摘Endemism of lineages lies at the core of understanding variation in community composition among geographic regions because it reflects how speciation,extinction,and dispersal have influenced current distributions.Here,we investigated geographic patterns and ecological drivers of taxonomic and phylogenetic endemism of angiosperm genera across the world.We identify centers of paleo-endemism and neo-endemism of angiosperm genera,and show that they are mostly located in the Southern Hemisphere in tropical and subtropical regions,particularly in Asia and Australia.Different categories of phylogenetic endemism centers can be differentiated using current climate conditions.Current climate,historical climate change,and geographic variables together explained~80%of global variation in taxonomic and phylogenetic endemism,while 42-46%,1%,and 15%were independently explained by these three types of variables,respectively.Thus our findings show that past climate change,current climate,and geography act together in shaping endemism,which are consistent with the findings of previous studies that higher temperature and topographic heterogeneity promote endemism.Our study showed that many centers of phylogenetic endemism of angiosperms,including regions in Amazonia,Venezuela,and west-central tropical Africa that have not previously been identified as biodiversity hotspots,are missed by taxon-based measures of endemism,indicating the importance of including evolutionary history in biodiversity assessment.
文摘Predicting the spatial distribution of soil moisture is an important hydrological question. We measured the spatial distribution of surface soil moisture (upper 6 cm) using an Amplitude Domain Reflectometry sensor at the plot scale (2 × 2 m) and small catchment scale (0.84 ha) in a temperate forest. The spatial variation of soil water content was higher during dry conditions than that during wet conditions. Results indicated 3.1 samples at the plot scale were sufficient to estimate mean soil water content when the precision was 0.1. Soil water content increased with increasing topographic index (TI) and soil-topographic index (STI) at the small catchment scale. The correlation between soil water content and TI was higher than that between soil water content and STI. This suggests that topography is more important for estimating surface soil moisture than soil depth as formation of surface soil moisture occurs at ≤6 cm.
基金Project of Shaanxi Provincial Land Engineering Construction Group(DJNY2021-32).
文摘Based on the DEM raster image data with a resolution of 60 m×60 m in the Sanjiangyuan region,the topographic heterogeneity in the Sanjiangyuan region was analyzed by calculating and processing the topographic relief,elevation standard deviation,terrain heterogeneity and surface roughness indexes.The results show that the overall terrain elevation of the Sanjiangyuan area is high,and the surface undulations are large.The southern and southeastern parts of the region are the places with the most dramatic terrain changes.The absolute values of terrain undulations,elevation standard deviation and surface roughness are large.In the central and western regions,the terrain change is small,the relief degree is small,the elevation standard deviation and the surface roughness are small.
文摘The ecological environment of the Three-River Headwater Region is primitive and unique,and sensitive and complex to external influences.The Three-River Headwater Region is the largest nature reserve in China,and is also a nature reserve with the highest concentration of biodiversity in the world's high-altitude areas,so the protection of ecological diversity in this region is particularly important.Ecological diversity is the material basis on which the entire humanity depends to survive and develop.It not only provides humans with basic needs such as food,energy and materials,and is also extremely important for maintaining ecological balance,regulating the climate and promoting the sustainable development of the region.Studying the topographical heterogeneity of the region is first of all a true grasp of the topography of the region,which has certain guiding significance for people's production and life.In addition,studying the impact of topographical heterogeneity on the climate of the region will help to study the formation and variation of regional climate.
