Boehmeria nivea var.strigosa Zeng Y.Wu&Y.Zhao,a new variety of B.nivea(Urticaceae)from Southwest China,is here described based on evidence from morphology and molecular phylogeny.This new variety is mainly charact...Boehmeria nivea var.strigosa Zeng Y.Wu&Y.Zhao,a new variety of B.nivea(Urticaceae)from Southwest China,is here described based on evidence from morphology and molecular phylogeny.This new variety is mainly characterized by its green abaxial leaf blade,partly connate stipules,and densely patent strigose hairs on stems and potioles.The phylogenetic analysis based on rbc L,nrDNA and rbc L+nrDNA datasets,revealed that all individuals of B.nivea var.strigosa formed a monophyletic group.The conservation status of B.nivea var.strigosa is assessed as“Near Threatened”(NT)according to IUCN evaluation criteria.The discovery of this new variety is not only crucial for the taxonomy of ramie,but also provides reference for the exploration and utilization of ramie.展开更多
This study uses DEM （Digital Elevation Model） data and remote sensing maps of the study area in 1993, 1999, and 2009 to analyze the slope gradient change of land use patterns in Qiandongnan Prefecture, Guizhou provi...This study uses DEM （Digital Elevation Model） data and remote sensing maps of the study area in 1993, 1999, and 2009 to analyze the slope gradient change of land use patterns in Qiandongnan Prefecture, Guizhou province, China. The land use data were classified into five types, forest, farmland, grassland, water and built-up, the slope gradients were divided into four grades. Indices for analyzing land use features were defined by their proportions, transformation matrixes, land use degree and changes The results showed that all land use types can be found at every gradient. Generally, with the slope degree increased, the area of forest being augmented as well, while the area of the other land use types （farmland, grassland and build-up） declined. Moreover, a mass of farmland were shifted from other land use types from o° to 25°, while a quantity of forest were transformed from the other land use types on 〉 25° from 2993 to 2009. In terms of land use degree and changes, the area of farmland and buildup land use types decreased when slope degree increased. Finally, we calculated the five landscape pattern metrics： Patch Density （PD） value, Largest Patch Index （LPI）, Shannon＇s Diversity Index （SHDI）, Area-Weighted Mean Shape Index （AWMSI） and Contagion Index （CONTAG）. The results of metricsanalysis showed that PD values, SHDI values and CONTA values had a similar variation trend, that is, they decreased when slope degree increased. There was no obvious variation trend on LPI value.展开更多
There have been few in-depth quantitative studies on soil erosion control and the ecological effects of land use changes. Soil erosion is the first eco-environmental problem particularly in mountainous areas. A major ...There have been few in-depth quantitative studies on soil erosion control and the ecological effects of land use changes. Soil erosion is the first eco-environmental problem particularly in mountainous areas. A major problem in the conversion of farmland to forest is to control soil erosion and improve ecological environment and thus to improve land use sustainability. We report results of calculation and analysis on soil erosion from converted farmland parcels in city of Mangshi （near the SW frontier of China） and the surrounding areas before and after the nine-year （2000-2009） project of converting farmland to forest. There was increased water conservation effect, as a result of decreased soil erosion. The average erosion modulus of the farmland returning to eco-friendly uses decreased by 5,535.59 t/km2·a and the control degree of soil erosion modulus reached 71.00%. The increased soil erosion after the returning in the typical sample area ＂did not drop, but increased＂ as the terraced fields decreased but sloping farmland inereased and yet woodland decreased.展开更多
Using a new vortex detection and tracing method, a dataset of the Southwest Vortex(SWV) is established based on Japanese 25-year Reanalysis(JRA-25) reanalysis data during 1979–2008. The spatiotemporal features of the...Using a new vortex detection and tracing method, a dataset of the Southwest Vortex(SWV) is established based on Japanese 25-year Reanalysis(JRA-25) reanalysis data during 1979–2008. The spatiotemporal features of the SWV are derived from the dataset. In comparison to other seasons, summer yields the least SWVs, but with the highest probability that they will migrate from their region of origin. SWVs mostly emerge in the southwest of the Sichuan Basin and the southeast of the Tibetan Plateau. Migratory SWVs mainly move along either an eastward or southeastward path. Detailed composite analysis of warm-season SWVs shows that the subtropical high is a key factor in determining the direction of migratory SWVs. Furthermore, the steering wind at 700 hPa dominates the moving direction of migratory SWVs. Potential stability diagnosed by pseudo-equivalent potential temperature ? se is of certain significance for the evolution and movement of SWVs. On the other hand, migratory SWVs possess relatively greater strength than stationary SWVs, due to a stronger low-level jet with enhanced baroclinicity and moisture transport providing more energy to support the growth of SWVs along their paths of movement.展开更多
文摘Boehmeria nivea var.strigosa Zeng Y.Wu&Y.Zhao,a new variety of B.nivea(Urticaceae)from Southwest China,is here described based on evidence from morphology and molecular phylogeny.This new variety is mainly characterized by its green abaxial leaf blade,partly connate stipules,and densely patent strigose hairs on stems and potioles.The phylogenetic analysis based on rbc L,nrDNA and rbc L+nrDNA datasets,revealed that all individuals of B.nivea var.strigosa formed a monophyletic group.The conservation status of B.nivea var.strigosa is assessed as“Near Threatened”(NT)according to IUCN evaluation criteria.The discovery of this new variety is not only crucial for the taxonomy of ramie,but also provides reference for the exploration and utilization of ramie.
基金supported by the National Natural Science Foundation of China (Grant No. 31370480)111 Project (B08044)Minzu University of China (MUC98507-08)
文摘This study uses DEM （Digital Elevation Model） data and remote sensing maps of the study area in 1993, 1999, and 2009 to analyze the slope gradient change of land use patterns in Qiandongnan Prefecture, Guizhou province, China. The land use data were classified into five types, forest, farmland, grassland, water and built-up, the slope gradients were divided into four grades. Indices for analyzing land use features were defined by their proportions, transformation matrixes, land use degree and changes The results showed that all land use types can be found at every gradient. Generally, with the slope degree increased, the area of forest being augmented as well, while the area of the other land use types （farmland, grassland and build-up） declined. Moreover, a mass of farmland were shifted from other land use types from o° to 25°, while a quantity of forest were transformed from the other land use types on 〉 25° from 2993 to 2009. In terms of land use degree and changes, the area of farmland and buildup land use types decreased when slope degree increased. Finally, we calculated the five landscape pattern metrics： Patch Density （PD） value, Largest Patch Index （LPI）, Shannon＇s Diversity Index （SHDI）, Area-Weighted Mean Shape Index （AWMSI） and Contagion Index （CONTAG）. The results of metricsanalysis showed that PD values, SHDI values and CONTA values had a similar variation trend, that is, they decreased when slope degree increased. There was no obvious variation trend on LPI value.
基金funded by the National Natural Science Foundation of China (No.40861014)
文摘There have been few in-depth quantitative studies on soil erosion control and the ecological effects of land use changes. Soil erosion is the first eco-environmental problem particularly in mountainous areas. A major problem in the conversion of farmland to forest is to control soil erosion and improve ecological environment and thus to improve land use sustainability. We report results of calculation and analysis on soil erosion from converted farmland parcels in city of Mangshi （near the SW frontier of China） and the surrounding areas before and after the nine-year （2000-2009） project of converting farmland to forest. There was increased water conservation effect, as a result of decreased soil erosion. The average erosion modulus of the farmland returning to eco-friendly uses decreased by 5,535.59 t/km2·a and the control degree of soil erosion modulus reached 71.00%. The increased soil erosion after the returning in the typical sample area ＂did not drop, but increased＂ as the terraced fields decreased but sloping farmland inereased and yet woodland decreased.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41275064 and 41175057)the Public Science and Technology Research Fund Projects of the Ocean (Grant No. 201005019)
文摘Using a new vortex detection and tracing method, a dataset of the Southwest Vortex(SWV) is established based on Japanese 25-year Reanalysis(JRA-25) reanalysis data during 1979–2008. The spatiotemporal features of the SWV are derived from the dataset. In comparison to other seasons, summer yields the least SWVs, but with the highest probability that they will migrate from their region of origin. SWVs mostly emerge in the southwest of the Sichuan Basin and the southeast of the Tibetan Plateau. Migratory SWVs mainly move along either an eastward or southeastward path. Detailed composite analysis of warm-season SWVs shows that the subtropical high is a key factor in determining the direction of migratory SWVs. Furthermore, the steering wind at 700 hPa dominates the moving direction of migratory SWVs. Potential stability diagnosed by pseudo-equivalent potential temperature ? se is of certain significance for the evolution and movement of SWVs. On the other hand, migratory SWVs possess relatively greater strength than stationary SWVs, due to a stronger low-level jet with enhanced baroclinicity and moisture transport providing more energy to support the growth of SWVs along their paths of movement.
