Vegetation fractional coverage (VFC) is one of the key indicators of vegetation distribution. In the work a measurement-based model was developed to derive total forest VFC (TG) as well as the VFC of trees (T) and shr...Vegetation fractional coverage (VFC) is one of the key indicators of vegetation distribution. In the work a measurement-based model was developed to derive total forest VFC (TG) as well as the VFC of trees (T) and shrub-grasses (G) separately in a subtropical forest area in Nanjing, China. Both upward and downward photographs were taken with a digital camera in 72 quadrats (10 m × 10 m each). Fifteen models were established and validated. Models jointly using both T and G performed better than those using the T and G separately. The best model, TG = T + G- 1.134 × T × G- 0.025 (R2 = 0.9115, P < 0.01, root mean squared error = 0.0789), is recommended for application. This model provides a good way to obtain total forest VFC values through taking tree and shrub-grass photos on ground below tree canopy rather than above tree canopy.展开更多
A quite severe degradation was found in all seven types of grasslands in the study area involving 12counties of the northwestern Qinghai Province. The slightly, moderately and severely degraded grasslandsoccupied 49.7...A quite severe degradation was found in all seven types of grasslands in the study area involving 12counties of the northwestern Qinghai Province. The slightly, moderately and severely degraded grasslandsoccupied 49.7%, 32.0% and 18.3% of the area respectively. The major factors resulting in the degradationwere overgrazing, the damages from mice and grasshopper and blown sands, and improper use of grasslands.The measures to deal with these problems should be: 1) to make livestock development in accordancewith grassland carrying capacity for animals; 2) to build more artificial grasslands with a stable and highergraas yield; 3) to put more widely the rotation grazing system into practice; 4) to clear up the poisonousgrass species; and 5) to adopt more effective measures to deal with the damages to grasslands by mice andgrasshoppers.展开更多
The relationship between rangeland grasshopper density and soil type as well as topsoil moisture content was analyzed with in situ soil data collected in the Qinghai Lake region of China. Grasshoppers were confined ma...The relationship between rangeland grasshopper density and soil type as well as topsoil moisture content was analyzed with in situ soil data collected in the Qinghai Lake region of China. Grasshoppers were confined mainly to the areas with light chestnut soil or chestnut soil, and very few were found in areas with subalpine meadow soil. Grasshoppers were almost absent from other types of soil, such as aeolian soil. In addition, analysis of 14 soil samples collected in the study area revealed that a soil moisture content between 18 and 32 g kg-1 coincided spatially with a higher density of grasshoppers, with the grasshopper density averaging 15 head m-2. In areas with a soil moisture content above 42 g kg-1 or below 10 g kg-1, grasshopper density dropped to less than 5 head m-2. These indicated that for the study area, soils with very high or very low moisture contents were not conducive to the survival of grasshoppers.展开更多
基金Supported by the National Basic Research Program (973 Program) of China (No.2007CB407206)the National Natural Science Foundation of China (No.40371053)
文摘Vegetation fractional coverage (VFC) is one of the key indicators of vegetation distribution. In the work a measurement-based model was developed to derive total forest VFC (TG) as well as the VFC of trees (T) and shrub-grasses (G) separately in a subtropical forest area in Nanjing, China. Both upward and downward photographs were taken with a digital camera in 72 quadrats (10 m × 10 m each). Fifteen models were established and validated. Models jointly using both T and G performed better than those using the T and G separately. The best model, TG = T + G- 1.134 × T × G- 0.025 (R2 = 0.9115, P < 0.01, root mean squared error = 0.0789), is recommended for application. This model provides a good way to obtain total forest VFC values through taking tree and shrub-grass photos on ground below tree canopy rather than above tree canopy.
文摘A quite severe degradation was found in all seven types of grasslands in the study area involving 12counties of the northwestern Qinghai Province. The slightly, moderately and severely degraded grasslandsoccupied 49.7%, 32.0% and 18.3% of the area respectively. The major factors resulting in the degradationwere overgrazing, the damages from mice and grasshopper and blown sands, and improper use of grasslands.The measures to deal with these problems should be: 1) to make livestock development in accordancewith grassland carrying capacity for animals; 2) to build more artificial grasslands with a stable and highergraas yield; 3) to put more widely the rotation grazing system into practice; 4) to clear up the poisonousgrass species; and 5) to adopt more effective measures to deal with the damages to grasslands by mice andgrasshoppers.
基金Project supported by the National Natural Science Foundation of China (No. 40371081).
文摘The relationship between rangeland grasshopper density and soil type as well as topsoil moisture content was analyzed with in situ soil data collected in the Qinghai Lake region of China. Grasshoppers were confined mainly to the areas with light chestnut soil or chestnut soil, and very few were found in areas with subalpine meadow soil. Grasshoppers were almost absent from other types of soil, such as aeolian soil. In addition, analysis of 14 soil samples collected in the study area revealed that a soil moisture content between 18 and 32 g kg-1 coincided spatially with a higher density of grasshoppers, with the grasshopper density averaging 15 head m-2. In areas with a soil moisture content above 42 g kg-1 or below 10 g kg-1, grasshopper density dropped to less than 5 head m-2. These indicated that for the study area, soils with very high or very low moisture contents were not conducive to the survival of grasshoppers.
