: Shifting cultivation is a major form of agricultural practice in most parts of tropical regions worldwide. In places where the bush fallow period is excessively shortened or the period of cultivation is extended for...: Shifting cultivation is a major form of agricultural practice in most parts of tropical regions worldwide. In places where the bush fallow period is excessively shortened or the period of cultivation is extended for too long, the rate of vegetation recovery and biodiversity on abandoned lands of shifting cultivation would decline. The recovery of the secondary plant communities could even be inhibited for a prolonged period because of grass occupancy. Because of the vital significance of the early recovery communities to secondary succession, we studied the community characteristics of early recovery vegetation on abandoned lands of shifting cultivation in Bawangling of Hainan Island. Measurements were made of the community composition and structure of early recovery vegetation. The sprouting abilities of different functional groups and different species in the same functional group, and the effect of the grass functional group on the composition and quantitative characteristics of tree and shrub functional groups were analyzed. Results indicated that only a few families, genera, or species apparently dominated in the early recovery vegetation on the abandoned lands of shifting cultivation and that deciduous species occurred with a rather high percentage in this early recovery community compared with the natural secondary or old growth forests. Small-sized individuals dominated the woody community. The abundance and basal area of sprouting stems for species in the tree functional group were greater than those of seeder stems, whereas the abundance and basal area of resprouters and seeders for species in the shrub functional group did not differ. The total abundance of stems for the community, stem abundances for species in tree or shrub functional groups, and for seeder or resprouter stems were all negatively correlated with coverage of the grass functional group. The mean sprouting ability in the tree functional group was greater than in the shrub functional group. The sprouting ability for different species in the same functional group was also significantly different.展开更多
All plants emit a wide range of volatile compounds, the so-called biogenic volatile organic compounds(BVOC). BVOC emissions have received increased scientific attention in the last two decades because theymay profound...All plants emit a wide range of volatile compounds, the so-called biogenic volatile organic compounds(BVOC). BVOC emissions have received increased scientific attention in the last two decades because theymay profoundly influence the chemical and physical properties of the atmosphere, and may modulate planttolerance to heat, pollutants, oxidative stress and abiotic stresses, and affect plant-plant and plant-insectinteractions. Urban forestry may have a high impact on atmospheric composition, air quality, environment,and quality of life in urban areas. However, few studies have been carried out where the emission of BVOCcould have important consequence for the quality of air and contribute to pollution episodes. A screening ofBVOC emission by the mixed stand constituting urban forests is therefore required if emissions are to bereliably predicted. Monitoring the emission rates simultaneously with measurements of air quality, plantphysiology and micrometeorology on selected urban forests, will allow detailed quantitative information onthe inventory of BVOC emissions by urban vegetation to be compiled. This information will make itpossible to propose an innovative management of urban vegetation in cities characterised by heavy emissionsof anthropogenic pollutants, aiming at the abatement of BVOC emissions through the introduction or selectionof non-BVOC emitting species in urban areas subjected to pollution episodes and in the new afforestationareas covering peri-urban parks, green belts and green corridors between peri-urban rural areas and theconurbations.展开更多
文摘: Shifting cultivation is a major form of agricultural practice in most parts of tropical regions worldwide. In places where the bush fallow period is excessively shortened or the period of cultivation is extended for too long, the rate of vegetation recovery and biodiversity on abandoned lands of shifting cultivation would decline. The recovery of the secondary plant communities could even be inhibited for a prolonged period because of grass occupancy. Because of the vital significance of the early recovery communities to secondary succession, we studied the community characteristics of early recovery vegetation on abandoned lands of shifting cultivation in Bawangling of Hainan Island. Measurements were made of the community composition and structure of early recovery vegetation. The sprouting abilities of different functional groups and different species in the same functional group, and the effect of the grass functional group on the composition and quantitative characteristics of tree and shrub functional groups were analyzed. Results indicated that only a few families, genera, or species apparently dominated in the early recovery vegetation on the abandoned lands of shifting cultivation and that deciduous species occurred with a rather high percentage in this early recovery community compared with the natural secondary or old growth forests. Small-sized individuals dominated the woody community. The abundance and basal area of sprouting stems for species in the tree functional group were greater than those of seeder stems, whereas the abundance and basal area of resprouters and seeders for species in the shrub functional group did not differ. The total abundance of stems for the community, stem abundances for species in tree or shrub functional groups, and for seeder or resprouter stems were all negatively correlated with coverage of the grass functional group. The mean sprouting ability in the tree functional group was greater than in the shrub functional group. The sprouting ability for different species in the same functional group was also significantly different.
文摘All plants emit a wide range of volatile compounds, the so-called biogenic volatile organic compounds(BVOC). BVOC emissions have received increased scientific attention in the last two decades because theymay profoundly influence the chemical and physical properties of the atmosphere, and may modulate planttolerance to heat, pollutants, oxidative stress and abiotic stresses, and affect plant-plant and plant-insectinteractions. Urban forestry may have a high impact on atmospheric composition, air quality, environment,and quality of life in urban areas. However, few studies have been carried out where the emission of BVOCcould have important consequence for the quality of air and contribute to pollution episodes. A screening ofBVOC emission by the mixed stand constituting urban forests is therefore required if emissions are to bereliably predicted. Monitoring the emission rates simultaneously with measurements of air quality, plantphysiology and micrometeorology on selected urban forests, will allow detailed quantitative information onthe inventory of BVOC emissions by urban vegetation to be compiled. This information will make itpossible to propose an innovative management of urban vegetation in cities characterised by heavy emissionsof anthropogenic pollutants, aiming at the abatement of BVOC emissions through the introduction or selectionof non-BVOC emitting species in urban areas subjected to pollution episodes and in the new afforestationareas covering peri-urban parks, green belts and green corridors between peri-urban rural areas and theconurbations.
