[Photosynthetic mechanism of tea yield and quality affected by different habitats]. / ç”Ÿå¢ƒå¯¹èŒ¶å¶å“è´¨å’Œäº§é‡å½±å“çš„å ‰åˆç”Ÿç†æœºåˆ¶.

To understand photosynthetic mechanism of tea yield and quality, an experiment was conducted with four different typical habitats, including three intercropping patterns (S1:Osmanthus-Tea, S2:Michelia-Tea, S3:Osmanthus-Michelia-Tea) and a control (CK) at Changsha Agricutural Observation Station of Chinese Academy of Sciences. The photosynthetic physiological and ecological characteristics of tea yield and quality were examined. The results showed that the habitats S1, S2, S3 reduced the leaf temperature (TL), photosynthesis active radiation flux (PAR), net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (gs), as well as the tea polyphenol content. Habitats S1, S2, S3 significantly increased leaf relative humidity (RHS), total amino-acid content of tea, and the yield and quality of tea, with a pattern of S3>S1>S2>CK. The leaves in habitats S1 and S3 could be made into high-grade green tea and famous green tea respectively. Comprehensive indicators showed that habitat S3 is an ideal intercropping pattern for high quality and high yield of tea garden.

[Effects of Long-term Fertilization on Enzyme Activities in Profile of Paddy Soil Profiles].

The enzyme activity, which is closely related to soil material cycling (mineralization, transformation, etc.), can reflect soil quality and nutrient status. In order to explore the effect of long-term fertilization on the enzyme activity in paddy soil profile (0-40 cm), soils with organic fertilizer and inorganic fertilizer, and non-fertilized soils were selected, and the carbon and nitrogen contents, and the activities of ß-1,4-glucosidase (BG), and ß-1,4-N-acetylglucosaminidase (NAG) in 10cm depths of soil were analyzed. The results showed that the activities of BG and NAG in the soils treated with inorganic fertilizer and organic fertilizer increased by 0.73-47.87 nmol·(g·h)-1 and 1.33-128.81 nmol·(g·h)-1, and 0.19-9.72 nmol·(g·h)-1 and 0.92-57.66 nmol·(g·h)-1, respectively, compared to those for non-fertilized soil. Soil enzyme activity decreased with increasing soil depth. Soil enzyme activity in soil from 0-20 cm was significantly higher than that of soil from 20-40 cm. Soil enzyme activities were significantly affected by long term fertilization at different soil depths. RDA analysis showed that soil carbon and nitrogen contents had significant positive relationships with the activities of BG and NAG in the 0-20 cm soil profiles, however, negative relationships were observed in the 20-40 cm soil profiles. The long-term application of organic fertilizer significantly increased soil biomass and enzyme activity, both of which decreased with the increase in soil depth. Long-term fertilization could increase soil nutrient contents, microbial biomass, and extracellular enzyme activities, which has important theoretical significance for optimizing farmland fertilizer management and improving soil productivity.

[Characteristics of the mineralization and transformation of autotrophic microbes-assimilated carbon in upland and paddy soils].

In this study, the mineralization and decomposition of autotrophic microbe assimilated carbon (new carbon) and native organic carbon in three upland and three paddy soils in subtropical China were measured using the 14C-labelled tracer technique. The results showed that, during the 100-d incubation, the mineralization of the 'new carbon' displayed three stages: a rise in the first 10 days, a slowdown from 11-d to 50-d, and a stabilization stage after 50 d. The mineralization ratio of the 'new carbon' ranged between 8.0% and 26.9% and the mineralization rate ranged from 0.01 to 0.22 microg 14C x g(-1) x d(-1) (0.01-0.22 microg 14C x g(-1) x d(-1) in paddy soils and 0.01-0.08 microg 14C x g(-1) x d(-1) in upland soils). However, the mineralization ratio and rate for native SOC were 1.55%-5.74% and 1.3-25.66 microg C x g(-1) x d(-1), respectively. In the soil active C pools, the 14C-dissolved organic carbon (DOC) first rose by as much as 0.3 mg x kg(-1) in the early stages of incubation (0-10 d), decreased rapidly by 0.42 mg x kg(-1) from 10-30 d, and then declined gradually. The fluctuation of the 14C-microbial biomass carbon (MBC) differed from that of the 14C DOC. At the beginning stage of the incubation (0-10 d), the 14C-MBC decreased rapidly, and then rapidly increased from 10 to 30 d, and the rate of increase reduced and was gradually stabilized after 40 d. The 14C-DOC/DOC renewal rate in the paddy soil was significantly higher than in the upland soil while the 14C-MBC/MBC renewal rate in the upland soil was significantly greater than in the paddy soil.

[Carbon dioxide assimilation potential, functional gene amount and RubisCO activity of autotrophic microorganisms in agricultural soils].

Carbon dioxide (CO2) assimilation by autotrophic microorganisms plays a significant role in carbon sequestration in terrestrial ecosystems. Here, experiments were carried out to determine the contribution of autotrophic microorganisms to atmospheric CO2 fixation in 6 representative agricultural soils. Soils were incubated continuously in an atmosphere of 14CO2 and the distribution of labeled C into soil organic carbon (14C-SOC) was determined after 110 d. Meanwhile, the amounts of the cbbL genes were determined by Quantitative PCR and the RubisCO activity was measured in different soils. The results showed that substantial amounts of 14CO2 were fixed into 14C-SOC (ranged 10.63-133.81 mg x kg(-1) after 110 d of continuous labeling, with an annual, global rate of about 0.57-7.3 Pg. The microbially fixed C was also incorporated into the active carbon pool [the dissolved organic C (14C-DOC) and in the microbial biomass C (14C-MBC)], and ranged from 0.96 to 8.10 mg x kg(-1) and 1.70 to 49.16 mg x kg(-1), respectively. The proportion of 14C-SOC in SOC was 0.09%-0.64%. The 14C-DOC /DOC and 14C-MBC /MBC were 5.07%- 4.3% and 2.51%-13.12%, respectively. Thus, the distribution and transformation of microbially fixed C had a larger influence on the dynamics of DOC and MBC than on the total SOC dynamics. Moreover, the abundance of soil bacteria cbbL gene and RubisCO activity were in the range of 2.40 x 10(7) - 1.9 x 10(8) copies x g(-1) and 34.06-71.86 nmol x (g x min)(-1), respectively. The 14C-SOC content was significantly correlated with both the 14C-MBC content (P < 0.01) and the RubisCO activity (P < 0.01) in all tested soils. We concluded that autotrophic CO2 assimilation by soil microbes is significant to the global C cycle.

[Characteristics of soil microbial populations in depressions between karst hills under different land use patterns].

Based on the investigation and analysis of six soil microbial indices, eight soil conventional nutrient indices, six soil mineral nutrient indices, and 15 vegetation indices in the farmland, grassland, scrub, forest plantation, secondary forest, and primary forest in the depressions between karst hills, this paper analyzed the main soil microbial populations, soil microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP) and their fractal characteristics, and the relationships of the soil microbes with vegetation, soil nutrients, and soil mineral components under different land use patterns. The soil microbial populations differed in their quantity and composition under different land use patterns. Primary forest and farmland had the highest quantity of soil microbial populations, while forest plantation had the lowest one. The three forests had a higher proportion of soil bacteria, the farmland, grassland, and scrub had a higher proportion of actinomycetes, and all the six land use patterns had a low proportion of soil fungi. Under the six land use patterns, the soil MBC, MBN, and MBP were all high, with the maximum in primary forest. There was a good fractal relationship between the soil MBC and microbial populations, but no fractal relationships between the soil MBN and MBP and the microbial populations. Significant relationships were observed between the soil microbes and the vegetation, soil nutrients, and soil mineral components, and the soil MBC had the closest relationships with the Shannon index of tree layer and the soil total nitrogen, Fe2O3, and CaO contents.

[Relationships between vegetation characteristics and soil properties at different restoration stages on slope land with purple soils in Hengyang of Hunan Province, South-central China].

By using space series to replace time series, this paper studied the relationships between the vegetation characteristics and soil properties at different restoration stages on the slope land with purple soils in Hengyang of Hunnan Province South-central China. There existed obvious differences in the soil physical and chemical properties at different restoration stages. From grassplot, grass-shrub, shrub to shrub-arbor, the soil organic matter, total and available N, and moisture contents increased markedly, soil bulk density had an obvious decrease, soil total and available P contents changed little, and soil pH decreased gradually, but no significant differences were observed among different restoration stages. At different restoration stages, the biomass of plant community had effects on the quantity and composition of soil microbes. The quantities of soil bacteria and fungi had significant positive correlations with the aboveground biomass of plant community, but the quantity of soil actinomycetes had less correlation with plant community's aboveground biomass. At different restoration stages, the activities of soil urease, protease, alkaline phosphatase, invertase, cellulase, catalase, and polyphenol oxidase decreased with increasing soil layer, and had significant positive correlations with plant community's richness and aboveground biomass.

[Cadmium tolerance and enrichment characteristics of Eulaliopsis binata].

A pot experiment was conducted to study the cadmium (Cd) tolerance and enrichment characteristics of Eulaliopsis binata. Applying low concentration Cd (5 mg x kg(-1)) could boost the growth and physiological vigor of E. binata, with the twelve indexes such as biomass and net photosynthetic rate, etc. increased by 1.0% -15.5%, compared with CK; while applying high concentration Cd (> 5 mg x kg(-1)) had negative effects on the growth of E. binata. Even though the E. binata still finished its physiological circle under the application of 100 mg Cd x kg(-1), the biomass and net photosynthetic rate were decreased by 27.0% and 25.6%, respectively, in comparison with CK. The Cd content in the organs of E. binata increased greatly with increasing concentration of applied Cd. The Cd content in roots was from 350 mg x kg(-1) to 500 mg x kg(-1), and that in stems and leaves was from 15 mg x kg(-1) to 35 mg x kg(-1). When the concentration of applied Cd was < 50 mg x kg(-1), the Cd uptake by E. binata increased with increasing concentration of applied Cd. The Cd content in stems and leaves amounted 15.7% - 38.4% of the total uptake, and the ratio of the Cd content in stems and leaves to that in roots was up to 0.62. All the results indicated that E. binata had stronger capability in tolerating, enriching, and transporting Cd, being a potential Cd hyperaccumulator.