Relationships between topography,soil properties and the distribution of plant communities on two different rocky hillsides are examined in two subtropical karst forests in the Maolan National Natural Reserve,southwes...Relationships between topography,soil properties and the distribution of plant communities on two different rocky hillsides are examined in two subtropical karst forests in the Maolan National Natural Reserve,southwestern China.Surveys of two 1-ha permanent plots at each forest,and measurements of four topographic and thirteen edaphic factors on the slopes were performed.Twoway Indicator Species Analysis(TWINSPAN) and Detrended Canonical Correspondence Analysis(DCCA) were used for the classification of plant communities and for vegetation ordination with environmental variables.One hundred 10m×10m quadrats in each plot were classified into four plant community types.A clear altitudinal gradient suggested that elevation was important in community differentiation.The topography and soil explained 51.06% and 54.69% of the variability of the distribution of plant species in the two forest plots,respectively,indicating both topographic factors(eg.elevation,slope and rock-bareness rate) and edaphic factors(e.g.total P,K and exchangeable Ca) were the important drivers of the distribution of woody plant species in subtropical karst forest.However,our results suggested that topographical factors were more important than edaphic ones in affecting local plant distribution on steep slopes with extensive rock outcrops,while edaphic factors were more influential on gentle slope and relatively thick soil over rock in subtropical karst forest.Understanding relationships between vegetation and environmental factors in karst forest ecosystems would enable us to apply these findings in vegetation management strategies and restoration of forest communities.展开更多
This study on dynamic changes of culture color, astaxanthin and chlorophylls, inorganic N including N NO - 3, N NO - 2 and N NH + 4 in batch culture of Haematococcus pluvialis exposed to different additive nitrate con...This study on dynamic changes of culture color, astaxanthin and chlorophylls, inorganic N including N NO - 3, N NO - 2 and N NH + 4 in batch culture of Haematococcus pluvialis exposed to different additive nitrate concentration showed (1) ast/chl ratio was over 0.8 for brown and red algae, but was usually less than 0.5 for green and yellow algae; (2) N NO - 3, in general, was unstable and decreased, except for a small unexpected increase in nitrate enriched treatment groups; (3) measurable amounts of N NO - 2 and N NH + 4 were observed respectively with three change modes although no external nitrite and ammonia were added into the culture; (4) a non linear correlation between ast/chl ratio (or color) changes and the levels of N NO - 3 , N NO - 2 , N NH + 4 in H. pluvialis culture; (5) up and down variation of the ast/chl ratio occurred simultaneously with a perceptible color change from yellow to brown (or red) when N NO - 3, N NO - 2 and N NH + 4 fluctuated around 30, 5, 5 μmol/L respectively; (6) existence of three dynamic modes of N NO - 3, N NO - 2 and N NH + 4 changes, obviously associated with initial external nitrate; (7) the key level of total inorganic N concentration regulating the above physiological changes during indoor cultivation was about 50 μmol/L; and (8) 0.5-10 mmol/L of nitrate was theoretically conducive to cell growth in batch culture.展开更多
An efficient porous spherical polyethyleneimine-cellulose （PEI-cell） absorbent was synthesized and char- acterized. The main influencing factors and adsorption mechanism for two typical metal ions, Cr3＋ and Fe3＋, ...An efficient porous spherical polyethyleneimine-cellulose （PEI-cell） absorbent was synthesized and char- acterized. The main influencing factors and adsorption mechanism for two typical metal ions, Cr3＋ and Fe3＋, were investigated. The adsorption performance primarily depends on the initial concentration of metal ions, pH value and temperature, and the chelation action between N atoms of PEl-cell and metal ions plays an important role. Under dynamic adsorption conditions, the saturation adsorption of polyethyleneimine-cellulose is 83.98 mg.g-1 for Cr（Ⅲ） and 377.19 mg-g-1 for Fe（Ⅲ）, higher than report- ed data and that of unmodified cellulose. The adsorption can be well described with second-order kinetic equation and Freundlich adsorption model, and AH, AG and 5 of the adsorption are all negative. With 5% HCI as eluent, the elution ratio of Cr（Ill） and Fe（llI） achieved 99.88% and 97.74% at 313 K, respectively. After the porous PEI-cell was reused 6 times, it still presented satisfactory adsorption performance. Above results show the advantages such as easily-acquired raw material, high efficiency, stable recycling oerformance and biodegradability.展开更多
基金supported by the "Hundred Talents Program" of the Chinese Academy of Sciences (to Jian Ni)the National Basic Research Program (No. 973) of the Ministry of Science and Technology of China(Grant No. 2013CB956704)the Scientific Research Foundation of the Education Department of Guangxi Zhuang Autonomous Region (Grant No.201106LX296)
文摘Relationships between topography,soil properties and the distribution of plant communities on two different rocky hillsides are examined in two subtropical karst forests in the Maolan National Natural Reserve,southwestern China.Surveys of two 1-ha permanent plots at each forest,and measurements of four topographic and thirteen edaphic factors on the slopes were performed.Twoway Indicator Species Analysis(TWINSPAN) and Detrended Canonical Correspondence Analysis(DCCA) were used for the classification of plant communities and for vegetation ordination with environmental variables.One hundred 10m×10m quadrats in each plot were classified into four plant community types.A clear altitudinal gradient suggested that elevation was important in community differentiation.The topography and soil explained 51.06% and 54.69% of the variability of the distribution of plant species in the two forest plots,respectively,indicating both topographic factors(eg.elevation,slope and rock-bareness rate) and edaphic factors(e.g.total P,K and exchangeable Ca) were the important drivers of the distribution of woody plant species in subtropical karst forest.However,our results suggested that topographical factors were more important than edaphic ones in affecting local plant distribution on steep slopes with extensive rock outcrops,while edaphic factors were more influential on gentle slope and relatively thick soil over rock in subtropical karst forest.Understanding relationships between vegetation and environmental factors in karst forest ecosystems would enable us to apply these findings in vegetation management strategies and restoration of forest communities.
文摘This study on dynamic changes of culture color, astaxanthin and chlorophylls, inorganic N including N NO - 3, N NO - 2 and N NH + 4 in batch culture of Haematococcus pluvialis exposed to different additive nitrate concentration showed (1) ast/chl ratio was over 0.8 for brown and red algae, but was usually less than 0.5 for green and yellow algae; (2) N NO - 3, in general, was unstable and decreased, except for a small unexpected increase in nitrate enriched treatment groups; (3) measurable amounts of N NO - 2 and N NH + 4 were observed respectively with three change modes although no external nitrite and ammonia were added into the culture; (4) a non linear correlation between ast/chl ratio (or color) changes and the levels of N NO - 3 , N NO - 2 , N NH + 4 in H. pluvialis culture; (5) up and down variation of the ast/chl ratio occurred simultaneously with a perceptible color change from yellow to brown (or red) when N NO - 3, N NO - 2 and N NH + 4 fluctuated around 30, 5, 5 μmol/L respectively; (6) existence of three dynamic modes of N NO - 3, N NO - 2 and N NH + 4 changes, obviously associated with initial external nitrate; (7) the key level of total inorganic N concentration regulating the above physiological changes during indoor cultivation was about 50 μmol/L; and (8) 0.5-10 mmol/L of nitrate was theoretically conducive to cell growth in batch culture.
基金Supported by the National Natural Science Foundation of China(81373284,81102344)the Project of Education Department in Sichuan(14ZB0267)the Bureau of Science and Technology of Mianyang City of China(10Y003-8)
文摘An efficient porous spherical polyethyleneimine-cellulose （PEI-cell） absorbent was synthesized and char- acterized. The main influencing factors and adsorption mechanism for two typical metal ions, Cr3＋ and Fe3＋, were investigated. The adsorption performance primarily depends on the initial concentration of metal ions, pH value and temperature, and the chelation action between N atoms of PEl-cell and metal ions plays an important role. Under dynamic adsorption conditions, the saturation adsorption of polyethyleneimine-cellulose is 83.98 mg.g-1 for Cr（Ⅲ） and 377.19 mg-g-1 for Fe（Ⅲ）, higher than report- ed data and that of unmodified cellulose. The adsorption can be well described with second-order kinetic equation and Freundlich adsorption model, and AH, AG and 5 of the adsorption are all negative. With 5% HCI as eluent, the elution ratio of Cr（Ill） and Fe（llI） achieved 99.88% and 97.74% at 313 K, respectively. After the porous PEI-cell was reused 6 times, it still presented satisfactory adsorption performance. Above results show the advantages such as easily-acquired raw material, high efficiency, stable recycling oerformance and biodegradability.
