According to a lot of plot data, the productivity distribution patterns of Chinese-fir plantations related to geographical or hydro-thermal factors were clearly indicated. The geographical distribution model established here objectively reflects the geographical patterns of the high-yield Chinese-fir plantations. In terms of the ecological limitation rule, the optimal models of Chinese-fir productivity vs. hydro-thermal factors were set up, showing that the hydro-thermal factors ,which are most suitable for Chinese-fir growth ,are as follows: annual mean air-temperature 16～17 ℃ , annual precipitation 1700～1900 mm, warm index 145～150 ℃ month, Thornwaite’s potential evapotranspiration 920～930 mm. Under the climate conditions, the productivity of Chinese-fir plantations can be up to 17～18 t·hm-2·a-1 for arbor layer and 21～22 t·hm-2·a-1 for the whole forest.

Based on the data of located observation in Jianfengling,Hainan Island,China, the following aspects were investigated: the carbon storage of the main tropical forest soils; the release of CO2 from the soils and litter layers under tropical mountain rain forest and tropical semi-deciduous monsoon forest; the effect of slash-and-burn agriculture on the content of soil carbon and the release of CO2 from soil; and the effect of clear-cutting on the soil carbon storage. The results show that the carbon storage of the main tropical forest soils in Jianfengling was from 97.10t·hm-2 to 119. 54t·’hm-2, and ,in average 102.60t·hm-2 ;in tropical mountain rain forest, the storage of carbon in litter layer was 2.98t·hm-2 ,and CO2 was released at a rate of 33.16t·hm-2·a-1 from the forest land, of which 29.89t·hm-2·a-1 from soil, 3.27 t·hm -2·a-1 from litter layer; in tropical semi-deciduous monsoon forest, CO2 is released with a rate of 10.50 t· hm-2·a-1 from the forest land. The effect of slash-and-burn agriculture on soil carbon was observed even at the depth of 60 cm below soil surface, the release of CO2 from the land under the activity of slash-and-burn agriculture was 37.9 % ,higher than that from the land covered with tropical semi-deciduous monsoon forest. The results also show that clear cutting-caused the decrease in the carbon storage of the forest soil and natural regeneration made the carbon storage recovered.

During 1988～1993,about 70 times of floods were systematically observed in the sites located at 4 watersheds(in two groups) of different forest vegetation in Loess Area. Based on the data, the relationship among watershed sediment yield, the forest vegetation and the other 4 factors were investigated and modeled. Then the effects of forest vegetation on watershed sediment yield were analyzed using the model. The result shows that forest vegetation had a great role in yielding watershed sediment. The sediment yield in Miaogou small watershed (no forest vegetation) was higher by 33.4 times than that in Mujialing small watershed (with much forest vegetation). Its erosion control by forest vegetation was about 96.8%. The sediment yield in Miaogou watershed (with little forest vegetation) was higher by 4.3 times than that in Mujialing watershed (with much forest vegetation). Its erosion control by forest vegetation was about 75.53%. According to the analysis of erosion control effect by forest vegetation in loess area ,the erosion reduction formulas of forest vegetation were derived. Using these formulas,the reductions of watershed sediment due to forest vegetation under the conditions of different rainfalls can be calculated.

The biomass and biomass allocation principles of the secondary vegetation in the Qingshuihe tributary of Tuojiang river valley were investigated using field investigation, sample tree and regression analysis (for arbors) and plot harvest (for shrubbery and herbs). The adaptivity of main species was investigated from the viewpoint of biomass distributive coordination in this paper.1. In order to approach the relationships between biomass of main secondary vegetation type and DBH or volume, 11 models of regression analysis were set up. Among the models,Y=aXb was the best with coefficients ranging from 0.946 to 0.999.2. The sequence in which aboveground biomasses varied among different community types was as follows: Quercus variabilis + Cupressus funebris — Rhamnus leptoph ylla + Elaeagnus pungens — Imperata cylindrica var. major community (95.721 t· hm- 2 ) > Cupressus funebris + Alnus cremastogyne — Vitex negundo + Coriaria nepalensis — Imperata cylindrica var. major + Plantago asiatica community (546t·hm-2 ) >Cupressus funebris— Plantago asiatica + Ficus tikoua + Hetero-pogon contortus community ( 38.719t·hm-2 )> Vitex negundo + Coriaria nepalensis + Elaeagnus pungens + Myrsine africana-Imperata cylindrica var. major community ( 11.969t·hm-2)> (Coriaria nepalensis)-Imperata cylindrica var. major+ Heteropogon contortus+ Plantago asiatica community (4.073t·hm-2), The aboveground biomass of two types of Cupressus lusianica were 21.065t·hm-2 and 16.810t·hm-2 ,respectively.3. Stump and thick-roots(>2.0cm in diameter) contributed to 80.42% and 62.09% of their own total root biomass, respectively, in indigenous species and Cupressus lusianica. Under-ground biomasses accounted for 23.89 % and 7.44 % of total biomass respectively,or for 17.67 and 6.9 % of aboveground biomass respectively. This indicates a uncoordination between above-ground biomass and underground biomass of Cupressus lusianica,suggesting potential lodging.4. This paper made a contrasting analysis and evaluation on main secondary vegetation types, the allocations of tree biomass, vertical structure productive potentialities and protective functions, indicating that community types at higher successive stage are the superior model with economic and ecological functions in this region.

The paper deals with Hg,Cd and their interaction on chlorophyll content and antioxidant enzyme systems in leaves of tobacco. The result indicates that, as increasing of the concentration of Hg and/or Cd in soil, content of chlorophyll, chlorophyll a/b values and activity of CAT decreased, the activity of SOD increased first and decreased afterwards and the activity of POD increased. The effects of single Hg and single Cd on chlorophyll content and antioxidant enzymes systems were both more obvious than that of the interaction of Hg and Cd.

The geographical variation in the chlorophyll fluorescence induction kinetics of Pinus armandi was studied by measuring the chlorophyll fluorescence of intact needles of five seed sources distributing from northern to southern China. Results show that P. armandi growing in southern China possessed the higher values of the maximum fluorescence (Fm),variable fluorescence (Fv)and FvFm. This is an indication of that potential activity of PS Ⅱ and the efficiency of light conversion were higher in southern populations than in northern populations, and positively correlated with the growth of tree height. On the contrary, the coefficients of non-photochemical fluorescence quenching (On) was negatively interrelated with the variation of growth. It was higher in southern population than in northern populations. These results demonstrate that the analysis of fluorescence induction kinetics is applicable to prediction of the potential growth of tree height, and to the selection of optimum seed sources of Pinus armandi.

Following conclusions were obtained from comparison of various methods used in spruce population spatial distribution pattern on sandy sites. T-value is used to be employed to test statistically for the significance of the difference (i. e. Variance/Mean Method). Its mathematical inference is rigorous and calculation process is simple. In contrast, the results of aggregative indexes might produce deviation sometimes and need test by several indexes. Furthermore, their results are lack of efficient test on statistics When indexes are close to critical value, their results were difficult to determine. Therefore, the Variance/Mean Method is better than the method with aggregative index.