Change in Species Diversity during Recovering Process of Evergreen Broad-leaved Forest

Evergreen broad-leaved forestis one of the most important vegetation types in China.Because of the human activities,evergreen broad-leaved forest has been destroyed extensively,leading to degraded ecosystem.It is urgent to conserve and restore these natural forests in China. In this paper,the tendency and rate of species diversity restoration of the evergreen broad-leaved forest in Daming Mountain has been studied.The main resultsare as follows:(a)In subtropical mid-mountain area,species diversity in degraded evergreen broad-leaved forestcan be restored. Through analyzing b diversity index of communities in different time and space,it was found that the species composition of communities tend to be the same as that in the zonal evergreen broad-leaved forest.(b)The restoration rate of evergreen broad-leaved forest was very fast.Planting Chinese fir after clear-cutting and controlled burning of the forest,178 species appeared in a 600m^2 sample area after 20 years’natural recovering.Among the sespecies,58 were tree layer and the height of community reached 18m.The survey suggested that it would take only 20 years for the degraded forest to develop into community composed of lightdemanding broad-leaved pioneer trees and min-tolerance broad-leaved trees,and it need another 40~80 years to reach the stage consisting of min-tolerance evergreen broad-leaved trees.(c)Species number increased quickly at the early stage(2-20years)during vegetation recovering process toward the climax,and decreased at the min-stage (50-60 years),then maintained a relatively stable level at the late-stage (over 150 years).

Biogenic Emissions of Volatile Organic Compounds by Urban Forests

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.

A Review on Basic Research of Desertification Combating in China

China is one of the countries seriously affected by desertification in the world. Nowadays, China has desertification-affected land area of about 2.67 million square kilometers, accounting for 27.9 percent of the entire territory in China, at an average rate of about 10400 square kilometers annually during the period of 1994 to 1999.