This paper theoretically studies the continuous immobilized cell (IMC) fer mentation system. A kinetic model of IMC is established, and the relational expressions between production rate, substrate concentration, biom...This paper theoretically studies the continuous immobilized cell (IMC) fer mentation system. A kinetic model of IMC is established, and the relational expressions between production rate, substrate concentration, biomass concentration and dilution rate in the IMC continuous stirred tank reactor (CSTR) are derived. These equations and some numerical calculations show that as compared with the free cell system the IMC system has many advantages: high production rate, steady operation, and being independent of the dilution rote. They also indicate that the diffusion of substrate is a constraint to the production of metablite.展开更多
The distributions of dimethylsulfide （DMS） and its precursor dimethylsulfoniopropionate （DMSP） in surface water of the Yellow Sea and the Bohai Sea were studied during June 2011. The mean concentrations and ranges...The distributions of dimethylsulfide （DMS） and its precursor dimethylsulfoniopropionate （DMSP） in surface water of the Yellow Sea and the Bohai Sea were studied during June 2011. The mean concentrations and ranges of DMS, dissolved DMSP （DMSPd）, and particulate DMSP （DMSPp） in surface waters were 6.85 （1.60-12.36）, 7.25 （2.28-19.05） and 61.87 （6.28-224.01） nmol/L, respectively. There were strong correlations between DMSPp and chlorophyll a in the Bohai Sea and the North Yellow Sea, respectively, and concentrations of DMS and DMSP were high, with a relatively high proportion of dinoflagellates, in the region of the South Yellow Sea Cold Water Mass. Results show that phytoplankton biomass and species composition were important factors that controlled the distribution of DMS and DMSP. Complex environmental factors, including nutrients, transparency, and terrestrial runoff, might also influence the variability in DMS and DMSP. Biological production and consumption rates of DMS in the Bohai Sea were higher than those in the Yellow Sea. DMS production rates were closely correlated with DMSPd concentrations. DMS and DMSP exhibited obvious diel variations, with high concentrations occurring in the late afternoon （16：00-19：00） and low concentrations occurring during the night, implying that the intensity of solar radiation had a significant influence on these variations. Size distributions of chlorophyll a and DMSPp were also investigated and large nanoplankton （5-20 μm）, mainly diatoms, contributed significantly to chlorophyll a and DMSPp at most stations. The average sea-to-air flux of DMS in the study area was estimated to be 11.07 μmol/（m^2·d） during the summer.展开更多
The effects of different NaCl concentrations, nitrogen sources, carbon sources, and carbon to nitrogen molar ratios on biomass accumulation and polyhydroxybutyrate （PHB） production were studied in batch cultures of ...The effects of different NaCl concentrations, nitrogen sources, carbon sources, and carbon to nitrogen molar ratios on biomass accumulation and polyhydroxybutyrate （PHB） production were studied in batch cultures of the marine photosynthetic bacterium Rhodovulum sulfidophilum P5 under aerobic-dark conditions. The results show that the accumulation of PHB in strain P5 is a growth-associated process. Strain P5 had maximum biomass and PHB accumulation at 2%-3% NaCl, suggesting that the bacterium can maintain growth and potentially produce PHB at natural seawater salinity. In the nitrogen source test, the maximum biomass accumulation （8.10±0.09 g/L） and PHB production （1.11±0.13 g/L and 14.62%±2.25% of the cell dry weight） were observed when peptone and ammonium chloride were used as the sole nitrogen source. NH^-N was better for PHB production than other nitrogen sources. In the carbon source test, the maximum biomass concentration （7.65±0.05 g/L） was obtained with malic acid as the sole carbon source, whereas the maximum yield of PHB （5.03±0.18 g/L and 66.93%± 1.69% of the cell dry weight） was obtained with sodium pyruvate as the sole carbon source. In the carbon to nitrogen ratios test, sodium pyruvate and ammonium chloride were selected as the carbon and nitrogen sources, respectively. The best carbon to nitrogen molar ratio for biomass accumulation （8.77±0.58 g/L） and PHB production （6.07±0.25 g/L and 69.25%±2.05% of the cell dry weight） was 25. The results provide valuable data on the production of PHB by R. sulfidophilum P5 and further studies are on-going for best cell growth and PHB yield.展开更多
Fermentation of bioflocculant with Corynebacterium glutamicum was studied by way of kinetic modeling.Lorentzian modified Logistic model, time-corrected Luedeking–Piret and Luedeking–Piret type models were proposed a...Fermentation of bioflocculant with Corynebacterium glutamicum was studied by way of kinetic modeling.Lorentzian modified Logistic model, time-corrected Luedeking–Piret and Luedeking–Piret type models were proposed and applied to describe the cell growth, bioflocculant synthesis and consumption of substrates, with the correlation of initial biomass concentration and initial glucose concentration, respectively. The results showed that these models could well characterize the batch culture process of C. glutamicum at various initial glucose concentrations from 10.0 to 17.5 g·L-1. The initial biomass concentration could shorten the lag time of cell growth,while the maximum biomass concentration was achieved only at the optimal initial glucose concentration of16.22 g·L-1. A novel three-stage fed-batch strategy for bioflocculant production was developed based on the model prediction, in which the lag phase, quick biomass growth and bioflocculant production stages were sequentially proceeded with the adjustment of glucose concentration and dissolved oxygen. Biomass of2.23 g·L-1was obtained and bioflocculant concentration was enhanced to 176.32 mg·L-1, 18.62% and403.63% higher than those in the batch process, respectively, indicating an efficient fed-batch culture strategy for bioflocculant production.展开更多
The biodegradability of wastewater containing priority pollutant pesticideVydine or triadimenol（C14H18CLN3O2） in different bio-reactor configurations was investigated.Two laboratory scale biological reactors were em...The biodegradability of wastewater containing priority pollutant pesticideVydine or triadimenol（C14H18CLN3O2） in different bio-reactor configurations was investigated.Two laboratory scale biological reactors were employed：one reactor under aerobic condition and the other under anaerobic condition.The aerobic reactor was operated at an ambient temperature（22±2） °C,while the anaerobic reactor was run in the lower mesophilic range（30±2） °C.The effect of pesticide concentration,hydraulic retention time（HRT） ,and co-substrate on the treatment process was explored,using glucose as a supplemental carbon substrate.More than 96%pesticide was removed after an acclimation period of approximately 172 d（aerobic） and 230 d（anaerobic） .The aerobic reactor achieved complete Vydine utilization at feed concentrations up to 25 mg·L^-1 .On the other hand,the anaerobic reactor was able to degrade 25 mg·L^-1 of Vydine.Moreover,glucose was consumed first throughout the experiment in a sequential utilization pattern.The combination of anaerobic and aerobic biological processes yielded higher biomass concentration and lower retention time than individual units.The biomass in the combined reactors was first acclimated with the corresponding pesticide.Then,the target pesticide,at a concentration of 25 mg·L^-1,was sequentially treated in a semi batch mode in the reactors.HRT studies showed that 24 h HRT of aerobic and 12 h HRT of anaerobic were the optimum combination for the treatment of simulated wastewater containing Vydine,which produced Vydine effluent at concentration below 0.1 mg·L^-1 .The optimum ratio of substrate（Vydine） to co-substrate（glucose） was 1︰100.展开更多
Heavy metal pollution is one of the most important environmental problems today.Biosorption is an innovative tech-nology that employs biological materials to accumulate heavy metals from waste water through metabolic ...Heavy metal pollution is one of the most important environmental problems today.Biosorption is an innovative tech-nology that employs biological materials to accumulate heavy metals from waste water through metabolic process or physicochemi-cal pathways of uptake.Even though several physical and chemical methods are available for removal of heavy metals,currently many biological materials such as bacteria,algae,yeasts and fungi have been widely used due to their good performance,low cost and large quantity of availability.The aim of the present study is to explore the biosorption of toxic heavy metals,Cr（VI）,Cr（III）,Pb（II） and Cd（II） by algal biomass obtained from algae Sargassum wightii（brown） and Caulerpa racemosa（green）.Biosorption of algal biomass was found to be biomass concentration-and pH-dependent,while the maximal biosorption was found at pH 5.0 and with the metal concentration of 100 mg L-1.S.wightii showed the maximal metal biosorption at the biomass concentration of 25 g L-1,followed by C.racemosa with the maximal biosorption at 30 g L-1.S.wightii showed 78% biosorption of Cr（VI）,Cr（III）,Pb（II） and Cd（II） ions.C.racemosa exhibited 85% biosorption of Cd（II） and Cr（VI）,and 50% biosorption of Cr（III） and Pb（II）.The results of our study suggest that seaweed biomass can be used efficiently for展开更多
Acid hydrolysis is a simple and direct way to hydrolyze polysaccharides in biomass into fermentable sugars. To produce fermentable sugars effectively and economically for fuel ethanol, we have investigated the hydroly...Acid hydrolysis is a simple and direct way to hydrolyze polysaccharides in biomass into fermentable sugars. To produce fermentable sugars effectively and economically for fuel ethanol, we have investigated the hydrolysis of Enteromorpha using acids that are typically used to hydrolyze biomass： H2SO4, HC1, H3PO4 and C4H404 （maleic acid）. 5%（w/w） Enteromorpha biomass was treated for different times （30, 60, and 90 min） and with different acid concentrations （0.6, 1.0, 1.4, 1.8, and 2.2%, w/w） at 121~C. H2SO4 was the most effective acid in this experiment. We then analyzed the hydrolysis process in H2SO4 in detail using high performance liquid chromatography. At a sulfuric acid concentration of 1.8% and treatment time of 60 min, the yield of ethanol fermentable sugars （glucose and xylose） was high, （230.5 mg/g dry biomass, comprising 175.2 mg/g glucose and 55.3 mg/g xylose）, with 48.6% of total reducing sugars being ethanol fermentable. Therefore, Enteromorpha could be a good candidate for production of fuel ethanol. In future work, the effects of temperature and biomass concentration on hydrolysis, and also the fermentation of the hydrolysates to ethanol fuel should be focused on.展开更多
Gracilaria asiatica, being highly efficient in nutrient absorption, is cultivated in sea cucumber ponds to remove nutrients such as nitrogen and phosphate. It was cultured in a laboratory simulating field conditions, ...Gracilaria asiatica, being highly efficient in nutrient absorption, is cultivated in sea cucumber ponds to remove nutrients such as nitrogen and phosphate. It was cultured in a laboratory simulating field conditions, and its nutrient absorption was measured to evaluate effects of environmental conditions. Ammonia nitrogen （AN）, nitrate nitrogen （NN）, total inorganic nitrogen （TIN）, and soluble reactive phosphorus （SRP） uptake rate and removal efficiency were determined in a 4~2 factorial design experiment in water temperatures （T） at 15~C and 25~C, algae biomass （AB） at 0.5 g/L and 1.0 g/L, total inorganic nitrogen （TIN） at 30 ~tmol/L and 60 ~tmol/L, and soluble reactive phosphorus （SRP） at 3 and 6 ~tmol/L. AB and ambient TIN or SRP levels significantly affected uptake rate and removal efficiency of AN, NN, TIN, and SRP （P〈0.001）. G. asiatica in AB of 0.5 g/L showed higher uptake rate and lower removal efficiency relative to that with AB of 1.0 g/L. Nitrogen and phosphorus uptake rate rose with increasing ambient nutrient concentrations; nutrient removal efficiency decreased at higher environmental nutrient concentrations. The algae preferred to absorb AN to NN. Uptake rates of AN, NN, and SRP were significantly affected by temperature （P〈0.001）; uptake rate was higher for the 25~C group than for the 15~C group at the initial experiment stage. Only the removal efficiency of AN and SRP showed a significant difference between the two temperature groups （P〈0.01）. The four factors had significant interactive effects on absorption of N and P, implying that G. asiatica has great bioremedial potential in sea cucumber culture ponds.展开更多
Precipitation is a potential factor that significantly affects plant nutrient pools by influencing biomass sizes and nutrient concentrations. However, few studies have explicitly dissected carbon(C), nitrogen(N) and p...Precipitation is a potential factor that significantly affects plant nutrient pools by influencing biomass sizes and nutrient concentrations. However, few studies have explicitly dissected carbon(C), nitrogen(N) and phosphorus(P) pools between above- and belowground biomass at the community level along a precipitation gradient. We conducted a transect(approx. 1300 km long) study of Stipa purpurea community in alpine steppe on the Tibet Plateau of China to test the variation of N pool of aboveground biomass/N pool of belowground biomass(AB/BB N) and P pool of aboveground biomass/P pool of belowground biomass(AB/BB P) along a precipitation gradient. The proportion of aboveground biomass decreased significantly from mesic to drier sites. Along the belt transect, the plant N concentration was relatively stable; thus, AB/BB N increased with moisture due to the major influences by above- and belowground biomass allocation. However, P concentration of aboveground biomass decreased significantly with increasing precipitation and AB/BB P did not vary with aridity because of the offset effect of the P concentration and biomass allocation. Precipitation gradients do decouple the N and P pool of a S. purpurea community along a precipitation gradient in alpine steppe. The decreasing of N:P in aboveground biomass in drier regions may indicate much stronger N limitation in more arid area.展开更多
文摘This paper theoretically studies the continuous immobilized cell (IMC) fer mentation system. A kinetic model of IMC is established, and the relational expressions between production rate, substrate concentration, biomass concentration and dilution rate in the IMC continuous stirred tank reactor (CSTR) are derived. These equations and some numerical calculations show that as compared with the free cell system the IMC system has many advantages: high production rate, steady operation, and being independent of the dilution rote. They also indicate that the diffusion of substrate is a constraint to the production of metablite.
基金Supported by the National Natural Science Foundation of China(Nos.41320104008,41030858,41306069)the National Natural Science Foundation for Creative Research Groups(No.41221004)+3 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20110132120010)the Cheung Kong Scholars Program of Chinathe Taishan Scholar Program of Shandong Provincethe Fundamental Research Funds for the Central Universities
文摘The distributions of dimethylsulfide （DMS） and its precursor dimethylsulfoniopropionate （DMSP） in surface water of the Yellow Sea and the Bohai Sea were studied during June 2011. The mean concentrations and ranges of DMS, dissolved DMSP （DMSPd）, and particulate DMSP （DMSPp） in surface waters were 6.85 （1.60-12.36）, 7.25 （2.28-19.05） and 61.87 （6.28-224.01） nmol/L, respectively. There were strong correlations between DMSPp and chlorophyll a in the Bohai Sea and the North Yellow Sea, respectively, and concentrations of DMS and DMSP were high, with a relatively high proportion of dinoflagellates, in the region of the South Yellow Sea Cold Water Mass. Results show that phytoplankton biomass and species composition were important factors that controlled the distribution of DMS and DMSP. Complex environmental factors, including nutrients, transparency, and terrestrial runoff, might also influence the variability in DMS and DMSP. Biological production and consumption rates of DMS in the Bohai Sea were higher than those in the Yellow Sea. DMS production rates were closely correlated with DMSPd concentrations. DMS and DMSP exhibited obvious diel variations, with high concentrations occurring in the late afternoon （16：00-19：00） and low concentrations occurring during the night, implying that the intensity of solar radiation had a significant influence on these variations. Size distributions of chlorophyll a and DMSPp were also investigated and large nanoplankton （5-20 μm）, mainly diatoms, contributed significantly to chlorophyll a and DMSPp at most stations. The average sea-to-air flux of DMS in the study area was estimated to be 11.07 μmol/（m^2·d） during the summer.
基金Supported by the National Natural Science Foundation of China (Nos.30830015, 40806063)the Key Natural Science Foundation of Tianjin,China (No. 12JC2DJC22200)+2 种基金the Natural Science Foundation of Guangxi,China (No. 1000050096)the Foundation of Tianjin Key Laboratory of Marine Resources and Chemistry (Tianjin University of Science & Technology) (No. 200913)the Introduced Talents Scientific Research Initiating Foundation of Tianjin University of Science and Technology (No.20100410)
文摘The effects of different NaCl concentrations, nitrogen sources, carbon sources, and carbon to nitrogen molar ratios on biomass accumulation and polyhydroxybutyrate （PHB） production were studied in batch cultures of the marine photosynthetic bacterium Rhodovulum sulfidophilum P5 under aerobic-dark conditions. The results show that the accumulation of PHB in strain P5 is a growth-associated process. Strain P5 had maximum biomass and PHB accumulation at 2%-3% NaCl, suggesting that the bacterium can maintain growth and potentially produce PHB at natural seawater salinity. In the nitrogen source test, the maximum biomass accumulation （8.10±0.09 g/L） and PHB production （1.11±0.13 g/L and 14.62%±2.25% of the cell dry weight） were observed when peptone and ammonium chloride were used as the sole nitrogen source. NH^-N was better for PHB production than other nitrogen sources. In the carbon source test, the maximum biomass concentration （7.65±0.05 g/L） was obtained with malic acid as the sole carbon source, whereas the maximum yield of PHB （5.03±0.18 g/L and 66.93%± 1.69% of the cell dry weight） was obtained with sodium pyruvate as the sole carbon source. In the carbon to nitrogen ratios test, sodium pyruvate and ammonium chloride were selected as the carbon and nitrogen sources, respectively. The best carbon to nitrogen molar ratio for biomass accumulation （8.77±0.58 g/L） and PHB production （6.07±0.25 g/L and 69.25%±2.05% of the cell dry weight） was 25. The results provide valuable data on the production of PHB by R. sulfidophilum P5 and further studies are on-going for best cell growth and PHB yield.
基金Supported by the National Natural Science Foundation of China(21206143,51378444)the program for New Century Excellent Talents of Education Ministry of China(ncet-13-0501)
文摘Fermentation of bioflocculant with Corynebacterium glutamicum was studied by way of kinetic modeling.Lorentzian modified Logistic model, time-corrected Luedeking–Piret and Luedeking–Piret type models were proposed and applied to describe the cell growth, bioflocculant synthesis and consumption of substrates, with the correlation of initial biomass concentration and initial glucose concentration, respectively. The results showed that these models could well characterize the batch culture process of C. glutamicum at various initial glucose concentrations from 10.0 to 17.5 g·L-1. The initial biomass concentration could shorten the lag time of cell growth,while the maximum biomass concentration was achieved only at the optimal initial glucose concentration of16.22 g·L-1. A novel three-stage fed-batch strategy for bioflocculant production was developed based on the model prediction, in which the lag phase, quick biomass growth and bioflocculant production stages were sequentially proceeded with the adjustment of glucose concentration and dissolved oxygen. Biomass of2.23 g·L-1was obtained and bioflocculant concentration was enhanced to 176.32 mg·L-1, 18.62% and403.63% higher than those in the batch process, respectively, indicating an efficient fed-batch culture strategy for bioflocculant production.
文摘The biodegradability of wastewater containing priority pollutant pesticideVydine or triadimenol（C14H18CLN3O2） in different bio-reactor configurations was investigated.Two laboratory scale biological reactors were employed：one reactor under aerobic condition and the other under anaerobic condition.The aerobic reactor was operated at an ambient temperature（22±2） °C,while the anaerobic reactor was run in the lower mesophilic range（30±2） °C.The effect of pesticide concentration,hydraulic retention time（HRT） ,and co-substrate on the treatment process was explored,using glucose as a supplemental carbon substrate.More than 96%pesticide was removed after an acclimation period of approximately 172 d（aerobic） and 230 d（anaerobic） .The aerobic reactor achieved complete Vydine utilization at feed concentrations up to 25 mg·L^-1 .On the other hand,the anaerobic reactor was able to degrade 25 mg·L^-1 of Vydine.Moreover,glucose was consumed first throughout the experiment in a sequential utilization pattern.The combination of anaerobic and aerobic biological processes yielded higher biomass concentration and lower retention time than individual units.The biomass in the combined reactors was first acclimated with the corresponding pesticide.Then,the target pesticide,at a concentration of 25 mg·L^-1,was sequentially treated in a semi batch mode in the reactors.HRT studies showed that 24 h HRT of aerobic and 12 h HRT of anaerobic were the optimum combination for the treatment of simulated wastewater containing Vydine,which produced Vydine effluent at concentration below 0.1 mg·L^-1 .The optimum ratio of substrate（Vydine） to co-substrate（glucose） was 1︰100.
文摘Heavy metal pollution is one of the most important environmental problems today.Biosorption is an innovative tech-nology that employs biological materials to accumulate heavy metals from waste water through metabolic process or physicochemi-cal pathways of uptake.Even though several physical and chemical methods are available for removal of heavy metals,currently many biological materials such as bacteria,algae,yeasts and fungi have been widely used due to their good performance,low cost and large quantity of availability.The aim of the present study is to explore the biosorption of toxic heavy metals,Cr（VI）,Cr（III）,Pb（II） and Cd（II） by algal biomass obtained from algae Sargassum wightii（brown） and Caulerpa racemosa（green）.Biosorption of algal biomass was found to be biomass concentration-and pH-dependent,while the maximal biosorption was found at pH 5.0 and with the metal concentration of 100 mg L-1.S.wightii showed the maximal metal biosorption at the biomass concentration of 25 g L-1,followed by C.racemosa with the maximal biosorption at 30 g L-1.S.wightii showed 78% biosorption of Cr（VI）,Cr（III）,Pb（II） and Cd（II） ions.C.racemosa exhibited 85% biosorption of Cd（II） and Cr（VI）,and 50% biosorption of Cr（III） and Pb（II）.The results of our study suggest that seaweed biomass can be used efficiently for
基金Supported by the National High Technology Research and Development Program of China(863 Program)(No.2009AA10Z106)the Major State Basic Research Development Program(No.2011CB200902)+4 种基金the CAS International Innovation Partnership Program:Typical Environmental Process and Effects on Resources in Coastal Zone Areathe National Key Technology Research and Development Program(No.2008BAC49B01)the National Natural Science Foundation of China(Nos.40876082,30870247)Outstanding Young Scholar Fellowship of Shandong Province(No.JQ200914)the Science and Technology Project of Qingdao City(No.09-1-3-59-jch)
文摘Acid hydrolysis is a simple and direct way to hydrolyze polysaccharides in biomass into fermentable sugars. To produce fermentable sugars effectively and economically for fuel ethanol, we have investigated the hydrolysis of Enteromorpha using acids that are typically used to hydrolyze biomass： H2SO4, HC1, H3PO4 and C4H404 （maleic acid）. 5%（w/w） Enteromorpha biomass was treated for different times （30, 60, and 90 min） and with different acid concentrations （0.6, 1.0, 1.4, 1.8, and 2.2%, w/w） at 121~C. H2SO4 was the most effective acid in this experiment. We then analyzed the hydrolysis process in H2SO4 in detail using high performance liquid chromatography. At a sulfuric acid concentration of 1.8% and treatment time of 60 min, the yield of ethanol fermentable sugars （glucose and xylose） was high, （230.5 mg/g dry biomass, comprising 175.2 mg/g glucose and 55.3 mg/g xylose）, with 48.6% of total reducing sugars being ethanol fermentable. Therefore, Enteromorpha could be a good candidate for production of fuel ethanol. In future work, the effects of temperature and biomass concentration on hydrolysis, and also the fermentation of the hydrolysates to ethanol fuel should be focused on.
基金Supported by the Science and Technology Project of Tackling Key Problems in Shandong Province(No.2010GHY10505)the National Natural Science Foundation of China(No.31172426)
文摘Gracilaria asiatica, being highly efficient in nutrient absorption, is cultivated in sea cucumber ponds to remove nutrients such as nitrogen and phosphate. It was cultured in a laboratory simulating field conditions, and its nutrient absorption was measured to evaluate effects of environmental conditions. Ammonia nitrogen （AN）, nitrate nitrogen （NN）, total inorganic nitrogen （TIN）, and soluble reactive phosphorus （SRP） uptake rate and removal efficiency were determined in a 4~2 factorial design experiment in water temperatures （T） at 15~C and 25~C, algae biomass （AB） at 0.5 g/L and 1.0 g/L, total inorganic nitrogen （TIN） at 30 ~tmol/L and 60 ~tmol/L, and soluble reactive phosphorus （SRP） at 3 and 6 ~tmol/L. AB and ambient TIN or SRP levels significantly affected uptake rate and removal efficiency of AN, NN, TIN, and SRP （P〈0.001）. G. asiatica in AB of 0.5 g/L showed higher uptake rate and lower removal efficiency relative to that with AB of 1.0 g/L. Nitrogen and phosphorus uptake rate rose with increasing ambient nutrient concentrations; nutrient removal efficiency decreased at higher environmental nutrient concentrations. The algae preferred to absorb AN to NN. Uptake rates of AN, NN, and SRP were significantly affected by temperature （P〈0.001）; uptake rate was higher for the 25~C group than for the 15~C group at the initial experiment stage. Only the removal efficiency of AN and SRP showed a significant difference between the two temperature groups （P〈0.01）. The four factors had significant interactive effects on absorption of N and P, implying that G. asiatica has great bioremedial potential in sea cucumber culture ponds.
基金supported by the Western Action Plan Project of the Chinese Academy of Sciences(Grant No.KZCX2-XB3-08)the Strategic Pilot Science and Technology Projects of the Chinese Academy of Sciences(Grant No.XDB03030505)the National Key Technology Research and Design Program of China(Grant No.2010BAE00739-03)
文摘Precipitation is a potential factor that significantly affects plant nutrient pools by influencing biomass sizes and nutrient concentrations. However, few studies have explicitly dissected carbon(C), nitrogen(N) and phosphorus(P) pools between above- and belowground biomass at the community level along a precipitation gradient. We conducted a transect(approx. 1300 km long) study of Stipa purpurea community in alpine steppe on the Tibet Plateau of China to test the variation of N pool of aboveground biomass/N pool of belowground biomass(AB/BB N) and P pool of aboveground biomass/P pool of belowground biomass(AB/BB P) along a precipitation gradient. The proportion of aboveground biomass decreased significantly from mesic to drier sites. Along the belt transect, the plant N concentration was relatively stable; thus, AB/BB N increased with moisture due to the major influences by above- and belowground biomass allocation. However, P concentration of aboveground biomass decreased significantly with increasing precipitation and AB/BB P did not vary with aridity because of the offset effect of the P concentration and biomass allocation. Precipitation gradients do decouple the N and P pool of a S. purpurea community along a precipitation gradient in alpine steppe. The decreasing of N:P in aboveground biomass in drier regions may indicate much stronger N limitation in more arid area.
