[Effects of Eucalyptus Branches Biochar Application on Soil Physicochemical Properties of Acidified Soil in a Eucalyptus plantation in Northern Guangxi].

This study aims to explore the effects of different biochar applications on soil physical and chemical properties in a Eucalyptus plantation in Northern Guangxi, find the best biochar application amount, and provide scientific guidance for the efficient utilization of forest residue and soil improvement. The soil of a four-year Eucalyptus plantation at the Huangmian forest farm in Northern Guangxi was selected as the study area, and six treatments including 0 (CK), 0.5% (T1), 1.0% (T2), 2% (T3), 4% (T4), and 6% (T5) were set through a field-positioning experiment to analyze the changes in soil physical and chemical properties under different application rates. Compared with the 0-30 cm soil layer of the control treatment, biochar application decreased the mean soil bulk by 3.82%-33.55%, while it increased the soil natural water content, capillary porosity, and total capillary porosity by 7.67%-31.75%, 8.95%-33.19%, and 9.28%-35.86%, respectively. The contents of exchangeable acid, exchangeable aluminum, exchangeable hydrogen, and exchangeable sodium in the soil decreased by 8.28%-70.03%, 5.55%-70.34%, 5.10%-21.78%, and 12.81%-49.27%. Biochar application increased the cation exchange capacity, electrical conductivity, exchangeable magnesium, and exchangeable calcium by 27.08%-160.39%, 117.00%-546.64%, 17.10%-66.14%, and 17.38%-71.38%, respectively. Soil pH increased by 0.17-1.29 after biochar addition. Similarly, the contents of soil organic carbon, total phosphorus, total potassium, available nitrogen, available phosphorus, and available potassium increased by 10.94%-51.37%, 14.29%-59.45%, 6.48%-59.57%, 6.28%-29.41%, 4.79%-19.81%, and 7.72%-75.87%. There was a positive correlation among the main physical and chemical factors. The physical and chemical properties reached their maximum values in the T4 or T5 treatment (4% or 6%). Biochar application provided considerable relief from soil acidification in the Eucalyptus plantation and had a positive effect on soil physicochemical properties. The addition 4%-6% of ripe Eucalyptus biochar produced the optimum results. The results show that biochar can improve the physical and chemical properties of soil, increase soil fertility, and enhance the soil's ability to retain water and fertilizer after twelve months. The findings of this study can be used as a reference in practical applications for soil improvement and sustainable management of Eucalyptus plantations.

[Research on optimization system on tissue culture and rapid propagation of Pueraria mirifica].

OBJECTIVE: To study the tissue culture and rapid-proliferation techniques of Pueraria mirifica. METHOD: The tender branch were used as explants and cultivated in different media. The optimum media for inducing buds, proliferation and rooting were selected by adjusting the kinds and doses of plant hormones and special compounds. RESULT: The medium of MS + IBA 0.05 mg L(-1) + BA 0.5 mg L(-1) was suitable for buds inducing and could be used in the first generation cultivation; MS + IBA 0. 02 mg L(-1) + BA 0.2 mg L(-1) and MS +BA 0.1 mg L(-1) were employed by turns in subculture, 25 days propagation coefficient was 3.0; and the medium of 1/2MS + IBA 0.1 mg L(-1) + IAA 0.2 mg L(-1) + C (special compound) 10 mg L(-1) was used for roots inducing, the rooting rate was 76.9%. Rooting plantlets were transplanted in spring and summer; the surviving rate was 81.0%. CONCLUSION: This technique system could be employed for rapid propagation of P. mirifica.

[Seasonal variation of Cyclobalanopsis glauca whole-tree transpiration in karst region].

By using Granier's sap-flow method, the variations of sap flux density and whole-tree transpiration of Cyclobalanopsis glauca (syn. Quercus glauca) on a hilly slope in the karst region of South China were studied, with their driving factors analyzed. The sap flux density (Js) of C. glauca varied randomly with the diameter of breast height of individual trees, and its maximum occurred at 13:30-14:30. In a seasonal course, the daily Js was the maximum (56.00 g H2O x m(-2) x s(-1)) in summer, and the minimum (35.86 g H2O x m(-2) x s(-1)) in spring. The daily whole-tree transpiration had a greater change with weather condition, representing a power functional relationship with vapor pressure deficit (VPD) and photosynthesically active radiation (PAR) (R = 0.97, P < 0.01). The average daily whole-tree transpiration tended to be high in summer and low in winter and spring, and decreased with the decrease of soil moisture content in autumn (drought season). However, comparing with that of the tree species in other regions, the daily whole-tree transpiration amount of C. glauca in study region was still higher, even though the weather was dry and the soil was thin. It was presumed that in the dry season in karst region, the water supply for C. glauca could be mainly depended on the water-rich epikarst.

[Utilization of sugar cane bagasse hydrolysates for xylitol production by yeast].

The effects of the concentration of sulfuric acid and the ratio of liquid to solid on xylose yield from sugar cane bagasse in its hemicellulose hydrolysis process were studied with the Quadratic Rotary Combination Design. Regression analysis showed that there was a marked regression relationship between the two factors and xylose yield. As the result of optimizing the hydrolysis conditions by regression equation, xylose yield of 24 g/100 g sugar cane bagasse was obtained when sulfuric acid concentration was 2.4 g/L and liquid to solid ratio was 6.2 under the conditions of stream pressure of 2.5 x 10(4) Pa and hydrolysis time of 2.5 h. The macroporous resin adsorption was proved to be a good method to reduce the concentration of yeast cell growth inhibitor in sugar cane bagasse hemicellulose hydrolysate and to enhance the hydrolysate fermentability. The hydrolysate treated with macroporous resin adsorption under pH2 was used as the substrate for xylitol production by a xylitol-producting yeast, Candida tropicalis AS2.1776. At an initial xylose concentration of 200 g/L, all xylose was consumed within 110 h with a xylitol production rate of 1.15 g/L.h, and a xylitol yield of 0.64 g/g xylose.