Taking the Tamarix chinensis secondary shrubs in Laizhou Bay of Yellow River Delta as test objects, and by using synthetic factor method, this paper studied the main factors causing the lowly efficiency of T. chinensis secondary shrubs as well as the main parameters for the classification of lowly efficient T. chinensis secondary shrubs. A total of 24 indices including shrubs growth and soil physical and chemical properties were selected to determine the main affecting factors and parameters in evaluating and classifying the lowly efficient shrubs. There were no obvious correlations between the indices reflecting the shrubs growth and soil quality, and thus, only using shrub growth index to reflect the lowly efficiency level of T. chinensis was not enough, and it would be necessary to combine with soil quality factors to make a comprehensive evaluation. The principal factors reflecting the quality level of lowly efficient T. chinensis shrubs included soil salt content and moisture content, stand age, single tree's aboveground stem, leaf biomass, and basal diameter, followed by soil density, porosity, and soil nutrient status. The lowly efficient T. chinensis shrubs in the Bay could be classified into five types, namely, shrub with growth potential, slightly low quality shrub, moderately lowly efficient shrub, moderately low quality and lowly efficient shrub, and seriously low quality and lowly efficient shrub. The main features, low efficiency causes, and management measures of these shrubs were discussed based on the mean cluster value.
Four tree species(Robinia pseudoacacia,Quercus acutissima,Rhus typhma,Albizia kalkora) and four shrub species(Pyrus betulaefolia,Elaeagnus angustifolia,Lespedeza bicolor,Amorpha fruticosa) were selected in this research, and their leaf water potential,transpiration rates and environmental factors were measured in Jiaonan City,Shandong Province.The results indicate that: 1) the order of the daily average transpiration rates of the trees is A.kalkora R.pseudoacacia R.typhma Q.acutissima,and that of the shrubs is A.fruticosa L.bicolorE.angustifoliaP.betulaefolia;2) the order of the daily average leaf water potential among trees is A.kalkora R.pseudoacacia R.typhma Q.acutissima,while that of the shrubs is A.fruticosa L.bicolorE.angustifoliaP.betulaefolia;3)the biggest water use efficiency is A.kalkora for trees and A.fruticosa for shrubs;4) comparison of drought resistance indicates that A.kalkora R.pseudoacaciaR.typhma Q.acutissima for trees,while A.fruticosa L.bicolor E.angustifolia P.betulaefolia for shrubs in general.
Green accounting is generated on the basis of the environment resources worsening and revising traditional accounting.It appeared as early as 1960s and developed rapidly in the 90s.China's current accounting theory and practice cannot reflect the environmental costs of surveillance resources loss and also cannot adapt the sustainable development implementation.Implementing the green accounting system in China is not only an accounting issue,but also a social problem.This paper summarizes the various representative views and gives some preliminary ideas about establishing gradually the green accounting system in China.
The relation between diurnal variation of leaf net photosynthetic rate (Pn) and eco-physiological factors for three years old leaf of Hedera nepalensis var.sinensis under drought stress was analyzed using CIRAS-2 portable photosynthesis system.The diurnal variation of H.nepalensis var.sinensis photosynthesis and its midday depression phenomenon was explained clearly and its predominant environmental factors under drought stress were ascertained.Results showed that diurnal variation of H.nepalensis var.sinensis photosynthesis and its micro-environmental factors were connected with soil moisture nearly at the same time.With the aggravation of drought stress,the daily average and maximum Pn was decreased significantly.Compared with check treatment,the means of Pn in the drought stress of mild treatment,moderate treatment,and severe treatment were reduced by 15%,47%,and 70%,respectively.With the aggravation of drought stress,the diurnal variation of photosynthesis changed from a single peak curve to a double peak curve and the predominant cause of midday depression turned into non-stomatal limitation.By the methods of stepwise multi-regression and principal component analysis,there was an obvious difference in the environmental factors of impact Pn under different drought stresses.Under the condition of mild soil moisture,the causes of diurnal variation of Pn can be classified into two categories:one was air temperature,relative humidity and CO2 concentration and another was photosynthetic active radiation.The effects of photosynthetic active radiation,CO2 concentration,and relative humidity on Pn became more and more conspicuous with increase in drought stress and relative humidity was the dominant factor.
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