Studies on the changes of West Lake＇s zoobenthic communites after Qiantang River water was pumped into it

During Jan. 1995 to Dec. 1996, monthly investigations on the zoobenthic conummities of West Lake, samples were collected from six sampling stations. A total of 26 species of macmzoobenthes were identified. The seasonal changes in density and biomass of zoobenthos in this lake were analyzed. The annual mean densities were 980- 2751 ind/m^2 and mean biomass was 19.69 - 122.80 g/m^2. The densities in winter and early spring were higher than those in sumr^r and autunm. Comimrafive study of theprevious data ( 1982 to 1983) collected by the authors, showed that the succession of zoobenthic conammities, dominated by Procludius choreus in density and Bellamya purificata in biomass, had been occurred in Xiaonan sub-lake after Qiantang River water was drawn into it; and that the species and biomass of zoobenthes were then increased and the density was decreased. In other sub-lakes, the dominant species were Limnodrilus hoffmeisteri and Tokunag-ayusurika akamusi in density and Branchiura sowerbyi and Tokunagayusurika akamusi in biomass. The water quality was bad in these sub-lakes because these dominant species are indicators of eutrophication. According to the Margalef index and Goodnight index, West Lake is still an eutrophic lake. Only the water quality of Xiaonan sub-lake was improved after water drawn from the Qiantang River was introduced into it.

Varietal differences in photosynthetic characters and chlorophyll fluorescence induction kinetics parameters among intergeneric progeny derived from Oryza×Sorghum, its parents, and hybrid rice

A comparative study on the photosynthetic parameters among intergeneric progenies derived from Oryza sativa L.× Sorghum vulgare L. , its maternal parent Gui 630 and commercial 3-line hybrid rice Shanyou 63 in pot experiment in greenhouse was conducted. The morphological and photosynthetic characters of canopy leaves and chlorophyll fluorescence kinetic pm'mneters including Fv/Fm, Fv/F0, photochemical quenching coefficient and non-photochemical coefficient of canopy leaves of 3 varieties were measured. The results showed the progeny, Yuanyou 1, derived from an intergeneric cross of rice and sorghum possesses better canopy spatial architecture with thicker, heavier and bigger canopy leaf than its maternal parent Gui 630.Higher photosynthetic rate due to higher chlorophyll content, higher primary energy transformation efficiency,potential of PSII and non-photochemieal quenching coefficient (qE) were also measured in Yuanyou 1. These explain partly why the intergeneric progeny has higher biomass production, and better tolerance to adverse conditions and higher field yields even under stress conditions.

Phosphate-solubilizing microbes in rhizosphere soils of 19 weeds in southeastern China

Low phosphorus (P) availability is one of the most important factors limiting plant growth in red soils across southeastern China. Many non-symbiotic microorganisms in rhizosphere can enhance P solubility, hut little is known about the magnitude of their phosphorus-solubilizing ability (PSA) and the difference in phosphorus-solubilizing microorganisms (PSM) among plant species. The rmmber of phosphorns-solubilizing microorganisms and their PSA in rhizosphere soils of 19 weed species in a citrus orchard on red soil at Changshan, Zhejiang, China, were investigated. Inorganic P (powdered phos-phate rock, PR) and orgatfic P (lecithin, OP) were respectively used as the sole P-souree to examine the PSA of isolated microbes. The PS actinomycetes community varied greatly among the different weed rhizospheres while the PS fungus community showed to be most stable to the weed rhixosphere.The highest number of PR-PS and OP-PS bacteria was found in rhizos, phere soil of Mollugo pentaphyll and the highest nuraber of PR-PS and OP-PS actinomycetes was found in rhizosphere soil of Polygonum lapathlfollum. The highest number of PR-PS fungi was found in Erigeron annuus and Mollugo pen-taphyll rhizosphere soil, and the highest number of OP-PS fungi was found in rhizosphere soil of Maxus stachydifolius. Mazus stachydifolius showed the strongest PR-PS ability (6340.75μg) while Eragrostis pilosa showed the strongest OP-PS ability (1301.84μg). The PR-PS ability and OP-PS ability of Mollugo pentaphyll was 4432.87μg and 1122.05μg respectively. A significant correlation between the number of PR-PSM and OP-PSM was found. Significant correlation was only found between the PR-PS fungi number and its PSA( r = 0.75, P < 0.05 ) and between the number of OP-PS fungi and its PSA( r=0.87, P<0.011 ). It indicated that plant species had significant influence on components of the non-symbiotic PSM community and their activity in its rhizosphere soil. Fungi play a l~ role inphosphorus solubilization in weed rhizopshere. It suggested that weed conservadoncould benefit soil microbe development in agroecosystems, especially in the initial stage of agroecosystam develolmaent because there is less organic carbon in bare soil. The results suggested that weed conservation could increase PSA of PSM.

Prediction and setup of phytoplankton statistical model of Qiandaohu Lake

This research considers the mathematical relationship between concentration of Chla and seven environmental factors, i.e. Lake water temperature (T), Secci-depth (SD), pH, DO, CODMn, Total Nitrogen (TN), Total Phosphorus (TP). Stepwise linear regression of 1997 to 1999 monitoring data at each sampling point of Qiandaohu Lake yielded the multivariate regression models presented in this paper. The concentration of Chla as simulation for the year 2000 by the regression model was similar to the observed value. The suggested mathematical relationship could be used to predict changes in the lakewater environment at any point in time. The results showed that SD, TP and pH were the most significant factors affecting Chla concentration.