Soil microbial biomass is a dynamic force driving soil phosphorus cycling in soils. The temperature, time and method for killing soil organisms in soil biomass P determination are so important factors that affect the results. The aim of this study was to compare some methods of soil sterilization and soil microbial P (Pm) release in extraction with NaHCO3. Five samples of calcareous soils in three replicates were incubated in field capacity and 28°C. The texture of soils differed from loamy sand to sandy loam. They had 10-15% equivalent calcium carbonate, 1-3% organic carbon and 40-90 mg/kg available P content. After 1, 10, 30, and 50 days of incubation a portion of each soil was sterilized by five methods (chloroform fumigation, autoclaving at 121°C for 0.5 h, oven drying at 70°C for 48 h, oven drying at 180°C for 2 h, and ultrasonification). Phosphorus of the sterilized and control soils were extracted with 0.5M NaHCO3 (pH 8.5) and determined spectrophotometrically as blue molybdate-phosphate complexes under partial reduction with ascorbic acid. Results showed that the method of soil sterilization and soil type had significant effects on biomass P estimated in soils (P < 0.01). There were no significant differences between extracted biomass P at chloroform fumigation, autoclaving at 121°C for 0.5 h, and oven drying at 70°C for 48 h. However biomass P was significantly more extracted from soil by oven drying at 180°C for 2 h and by ultrasonification. Fixation of Pm in soil during the extraction period can reduce the precision of biomass P estimates. This effect was more obvious in biomass P determination by fumigation and oven drying at 70°C for 48 h. Biomass P determined by these methods and autoclaving had positive and significant correlations with soil sand contents, respectively due to long sterilization period and temperature. Ultrasonification released more P from these calcareous soils especially at the start of soil incubation. It released higher microbial P and reduced P sorption in soils; biomass P determined by this method compared to other methods had relatively higher correlations with fungi, glumales spore and P solubilizing bacteria numbers in soil.

Soil microbial biomass is a dynamic force driving soil phosphorus cycling in soils. The temperature, time and method for killing soil organisms in soil biomass P determination are so important factors that affect the results. The aim of this study was to compare some methods of soil sterilization and soil microbial P (Pm) release in extraction with NaHCO<SUB>3</SUB>. Five samples of calcareous soils in three replicates were incubated in field capacity and 28°C. The texture of soils differed from loamy sand to sandy loam. They had 10–15% equivalent calcium carbonate, 1–3% organic carbon and 40–90 mg/kg available P content. After 1, 10, 30, and 50 days of incubation a portion of each soil was sterilized by five methods (chloroform fumigation, autoclaving at 121°C for 0.5 h, oven drying at 70°C for 48&nbsp;h, oven drying at 180°C for 2 h, and ultrasonification). Phosphorus of the sterilized and control soils were extracted with 0.5M NaHCO<SUB>3</SUB> (pH 8.5) and determined spectrophotometrically as blue molybdate-phosphate complexes under partial reduction with ascorbic acid. Results showed that the method of soil sterilization and soil type had significant effects on biomass P estimated in soils (<I>P</I> < 0.01). There were no significant differences between extracted biomass P at chloroform fumigation, autoclaving at 121°C for 0.5 h, and oven drying at 70°C for 48 h. However biomass P was significantly more extracted from soil by oven drying at 180°C for 2 h and by ultrasonification. Fixation of Pm in soil during the extraction period can reduce the precision of biomass P estimates. This effect was more obvious in biomass P determination by fumigation and oven drying at 70°C for 48 h. Biomass P determined by these methods and autoclaving had positive and significant correlations with soil sand contents, respectively due to long sterilization period and temperature. Ultrasonification released more P from these calcareous soils especially at the start of soil incubation. It released higher microbial P and reduced P sorption in soils; biomass P determined by this method compared to other methods had relatively higher correlations with fungi, glumales spore and P solubilizing bacteria numbers in soil. &nbsp; &nbsp;

Soil microbial biomass is a dynamic force driving soil phosphorus cycling in soils. The temperature, time and method for killing soil organisms in soil biomass P determination are so important factors that affect the results. The aim of this study was to compare some methods of soil sterilization and soil microbial P (Pm) release in extraction with NaHCO3. Five samples of calcareous soils in three replicates were incubated in field capacity and 28 deg C. The texture of soils differed from loamy sand to sandy loam. They had 10-15% equivalent calcium carbonate, 1-3% organic carbon and 40-90 mg/kg available P content. After 1, 10, 30, and 50 days of incubation a portion of each soil was sterilized by five methods (chloroform fumigation, autoclaving at 121 deg C for 0.5 h, oven drying at 70 deg C for 48 h, oven drying at 180 deg C for 2 h, and ultrasonification). Phosphorus of the sterilized and control soils were extracted with 0.5M NaHCO3 (pH 8.5) and determined spectrophotometrically as blue molybdate-phosphate complexes under partial reduction with ascorbic acid. The method of soil sterilization and soil type had significant effects on biomass P. There were no significant differences between extracted biomass P at chloroform fumigation, autoclaving at 121 deg C for 0.5 h, and oven drying at 70 deg C for 48 h. However biomass P was significantly more extracted from soil by oven drying at 180 deg C for 2 h and by ultrasonification. Fixation of Pm in soil during the extraction period can reduce the precision of biomass P estimates. This effect was more obvious in biomass P determination by fumigation and oven drying at 70 deg C for 48 h. Biomass P determined by these methods and autoclaving had positive and significant correlations with soil sand contents, respectively due to long sterilization period and temperature. Ultrasonification released more P from these calcareous soils especially at the start of soil incubation. It released higher microbial P and reduced P sorption in soils; biomass P determined by this method compared to other methods had relatively higher correlations with fungi, glumales spore and P solubilizing bacteria numbers in soil.

Elevated CO2 concentration, light intensity and soil-sterile conditions are thought as three of the most important factors to affect plant growth and development. However, their combined physiological effect on plants is unknown so far. In this study, we measured the possible individual and combined impacts of the three factors on the growth of yellow birch seedlings (Betula alleghaniensis Britton). Our results showed that from individual perspective, elevated CO2 can significantly increase biomass attributes (e.g., leaf, root, and stem) and root biomass ratio; light intensity can significantly influence traits like total biomass and leaf biomass; while soil conditions can influence traits like height and leaf biomass. From two-way interaction perspective, the interaction CO2 and soil can significantly influence total plant biomass, root biomass and R:S ratio; the interaction of light and soil significantly influenced the height, basal diameter, stem biomass, and so on; the interaction between CO2 and light did not significantly influence the plant growth parameters except for branch biomass ratio. From three-way interaction perspective, both traits stem biomass and root biomass were influenced by the co-effect of the three environmental factors. In conclusion, single or interactive effects among CO2, light intensity and soil conditions can lead to various growth strategies for the yellow birch.

Elevated CO2 concentration, light intensity and soil-sterile conditions are thought as three of the most important factors to affect plant growth and development. However, their combined physiological effect on plants is unknown so far. In this study, we measured the possible individual and combined impacts of the three factors on the growth of yellow birch seedlings. Elevated CO2 levels can significantly increase biomass attributes (e.g., leaf, root, and stem) and root biomass ratio; light intensity can significantly influence traits like total biomass and leaf biomass; while soil conditions can influence traits like height and leaf biomass. From the two-way interaction perspective, the interaction of CO2 and soil can significantly influence total plant biomass, root biomass and R:S ratio; the interaction of light and soil significantly influenced the height, basal diameter, stem biomass, and so on; the interaction of CO2 and light did not significantly influence the plant growth parameters except for branch biomass ratio. From the three-way interaction perspective, both traits stem biomass and root biomass were influenced by the co-effect of the three environmental factors. In conclusion, single or interactive effects among CO2, light intensity and soil conditions can lead to various growth strategies for the yellow birch.

Elevated CO2 concentration, light intensity and soil-sterile conditions are thought as three of the most important factors to affect plant growth and development. However, their combined physiological effect on plants is unknown so far. In this study, we measured the possible individual and combined impacts of the three factors on the growth of yellow birch seedlings (Betula alleghaniensis Britton). Our results showed that from individual perspective, elevated CO2 can significantly increase biomass attributes (e.g., leaf, root, and stem) and root biomass ratio; light intensity can significantly influence traits like total biomass and leaf biomass; while soil conditions can influence traits like height and leaf biomass. From two-way interaction perspective, the interaction CO2 and soil can significantly influence total plant biomass, root biomass and R:S ratio; the interaction of light and soil significantly influenced the height, basal diameter, stem biomass, and so on; the interaction between CO2 and light did not significantly influence the plant growth parameters except for branch biomass ratio. From three-way interaction perspective, both traits stem biomass and root biomass were influenced by the co-effect of the three environmental factors. In conclusion, single or interactive effects among CO2, light intensity and soil conditions can lead to various growth strategies for the yellow birch.