Contents of dissolved organic carbon and nitrogen (DOC and DON) and nitrogen mineralization of wetland soils different in freezing and thawing cycle were investigated through an indoor incubation experiment. Results show that with the number of the cycles increasing,DOC and DON rose up first and then declined. DOC peaked after one cycle,either -5 to 5 ℃ or -25 to 5 ℃,while DON did after two cycles of -5 to 5 ℃ and four cycles of -25 to 5 ℃,which indicates that the effect of freezing and thawing alternation within a short time period was significant on DOC and DON in the soil. It was also quite obvious that nitrogen mineralization in the wetland soil was affected by freezing temperature and number of freezing and thawing cycles,and the soils under cycles of -25 to 5 ℃ were higher than under cycles of -5 to 5 ℃ in accumulative nitrogen mineralization. Alternation of freezing and thawing accelerated soil nitrogen mineralization,which facilitated accumulation of soil available nitrogen,thus building up an adequate N pool to meet the demand for N of the plant growing in the spring,which contributes significantly to maintenance of stability of the wetland ecosystem.

Land degradation and human-land conflict are getting more and more serious in the karst region,northwest Guangxi and sustainable development of the region is faced with severe challenges. The ecological footprint method was used to quantitatively analyze the status of sustainable development of Hechi,a region cited for case study in the karst region,and the GM (1,1) model to predict the ecological footprint and eco-capacity per capita of the region. Results show that in the period of 1985-2006,its eco-footprint nearly doubled,while eco-capacity decreased by 12.6%,turning eco-surplus into eco-deficit,which is a symbol of unsustainability. However,in the period of 1990-2001,its eco-footprint increased by 120.76%. But the rising trend began to level off after 2001. Analysis of composition of the eco-footprint indicates that cultivated land and grassland were developed the most,and grassland footprint changed the most vigorously,rising from 12.88% up to 30.12%. The prediction reveals that in the next 9 years its eco-footprint will keep on rising and so will its eco-deficit.

The processes of industrialization and urbanization have important influence on quantity variation of cultivated land,but they differed. Based on the annual statistics of agricultural land in Chuzhou from 1975 to 2005,analysis was carried out of the difference between industrialization and urbanization in effect on quantity variation of cultivated land using a vector autoregression model and the impulse response function and the variance decomposition methods. Results show that quantity variation of cultivated land,industrialization degree and urbanization degree are non-stationary. Industrialization affects negatively the quantity variation rate of cultivated land,while urbanization does positively. And the effect of the former is greater than the latter and lasts longer as well,which suggests that urbanization is the principal factor,triggering the variation in the fast developing period of Chuzhou City. In view of the unbalanced development of industrialization and urbanization,it is of great significance to conservation of cultivated land to rationalize the urbanization process and improve the integrated quality of urbanization.

Based on the investigation of typical sampling sites in the alluvial plain of the Haihe River,a functional equation,covering standard grains and natural quality of corresponding farmland,etc.,was established and used to calculate theoretic productivity. By referring to the data of actual grain output in the 3 years (2003—2005). Grain yield-increasing potential,land use intensity and management advantage of these farmland were analyzed. Results show that the gross theoretical productivity of the farmland in the Haihe River alluvial plain area was 3.03×10⁷ t,much higher than the actual output,1.49×10⁷ t on average in the three years 2003-2005. Currently,farmland resources for grain security is highly guaranteed. Through analysis of management advantage,the farmlands are sorted into different grades. Farmlands high in management advantage are concentrated in the alluvial plain area in Central South Hebei Province,where the grain productivity is under-developed due to limitation in irrigation facilities and other farmland infrastructures,and management level. So there is much room for the farmlands therein to increase grain output.

By referring to the ecosystem service value coefficients proposed by COSTANZA and XIE Gao-di,an ecosystem service value coefficient was developed which is applicable to urban ecosystems. And based on the land use change/cover (LUCC) data of Chongqing proper in the year of 1993,2000,and 2004,ecosystem service value of the city was calculated. Results show that since 1997 when Chongqing became a municipality directly under the Central Government,large areas of farmland and forest land were alienated for urban construction,causing fall in its urban ecosystem service value by 31.3%,from 564.75 million yuan in 1993 to 387.71 million yuan in 2004. The effect of the changes in the ecosystem service value coefficient on the total urban ecosystem service value of Chongqing is not flexible enough. The impact of the change in water surface and woodland area on the total urban ecosystem service value of Chongqing is significant.

A study was carried out on seasonal variation of species composition,biomass and distribution of alpine meadow plant communities with different grazing intensity in Hongyuan County,Sichuan Province. With increasing grazing intensity,dominancy of the plant community shifted from grasses(Roegneria nutans and Elymus nutans) to sedges (Kobresia pygmaea and K. setchwanensis). Over the growing season from June to September,aboveground biomass was the highest in Treatment NG (non-grazing plot) and the lowest in Treatment HG (heavily grazed plot),while belowground biomass showed an rising trend with increasing grazing intensity and it was significantly higher in Treatment HG and Treatment MG (moderately grazed plot) than in Treatment NG and Treatment LG (lightly grazed plot). Total plant biomass averaged over the growing season was 1 543.3,1 621.6,2 294.7,and 2 448.5 g·m^-2 in Treatments NG,LG,MG and HG,respectively. The proportion of belowground biomass to total plant biomass was 87.8%,81.8%,76.2%,and 69.2%,in Treatments HG,MG,LG and NG,respectively,which shows adaptation of the plants in the meadow to grazing.

A field experiment was carried out to study effects of four kinds of organic-inorganic mixed fertilizer i.e. canola cake compost （I）,swine manure compost （Ⅱ）,Chinese medicinal herb residue compost （Ⅲ）,and chicken manure compost （IV）,mixed with chemical fertilizer,separately,but equal in N rate on soil nitrogen supply and growth of maize. Results show that during the growing season of the maize,the contents of soil mineral nitrogen with application of organic-inorganic mixed fertilizers were all significantly higher than that in CK （chemical fertilizer alone）,especially in Treatment I and Treatment Ⅱ. The grain yield of maize in the four treatments ranged from 6 725 to 8 960 kg·hm^-2,all higher than CK,while the yields of Treatment Ⅰ,Ⅲ and Ⅳ are more than 20% higher than that of CK,the difference reached to significant level. Nitrogen use efficiency （NUE） of the four treatments varied in the range of 24.2%³9.8%,higher than that of CK. In conclusion,organic-inorganic mixed fertilizer,especially Treatment IV,could efficiently regulate release of N nutrient,keeping soil N supply in coincidence with N demand of maize,and thus significantly increased grain yield of the maize.

Based on fixed field monitoring data,soil water potential dynamics and water consumption in the oil-tea camellia woods on slope land of red soil were studied. Results show that during the rainy season in 2007 soil water potential and its variation coefficient at the upper slope was greater than at the lower slope. Soils,0-50 cm in depth in the upper slope and 0-40 cm in the down slope were obviously exposed to dual impacts of evaporation and transpiration,and the soil water potential at 90 cm in depth varied more sharply than in other soil horizons nearby. Soil physical properties and root distribution affected significantly water potential and water consumption. At 40 and 90 cm in depth,where the soil was turning from clay horizon into gravel horizon,and from gravel horizon to mottling horizon,respectively,water tended to accumulate and roots were apt to extend towards there. A significant exponential-correlation between dry weight of fine roots (d_r<1 mm) and depth of soil layer was observed and about 46.95% of the fine roots were distributed in the 90 cm soil layer. The proportion of fine roots was significantly and positively related to soil water potential(70-110 cm). Zero flux plane analysis revealed that during the continuous dry period in the rainy season,water moved upwards from the deep layers,with water potential varying the most sharply at 90 cm in depth. It was also confirmed that the soil layer around 90 cm is the leading zone of water consumption in the oil-tea camellia woods during the rainy season.

In order to investigate transformation of diammonium phosphate (DAP) and vertical diffusion of fertilizer-P in acidic soils,a red soil column from Jiangxi,China was applied with DAP and incubated and then slices of the column were sampled for analysis. Results show that after 31 days of incubation,fertilizer-P diffused no more than 5 cm. Fractionation of amorphous inorganic P revealed that only a limited portion of the added fertilizer-P remained water-soluble. A major portion of the added fertilizer-P was transformed into Al-P,which is high in availability,and Fe-P,and a small portion into occluded P (O-P) . The various forms of P decreased in concentration along with the increase in distance from the fertilizer application site. DAP significantly raised soil pH,and drastically enhanced activity of soil Fe,and Al. As a result,the Fe3+ and Al3+ released from decomposition of insoluble soil minerals played a pivotal role on fertilizer-P fixation in acidic red soil.

Based on analysis of dissolved organic carbon (DOC),with the techniques of UV-visible absorption and three-dimensional excitation emission matrix (3DEEM),distribution and origin of chromophoric dissolved organic matter (CDOM) in Lake Qianwei,Chongming Island at the Yangtze River Estuary were explored. In the surface layer of the water body,DOC was evenly distributed,with concentration ranging from 5.87 to 7.02 mg·L^-1 and averaging 6.35 mg·L^-1. The UV-visible absorption revealed that the calibrated absorption coefficient a₃₅₅ was the highest in the fish-culturing zone,reaching 4.58 m^-1,and declining towards either side,which implied that there were other sources of CDOM besides terrestrial sources. Fluorescence index (f_450/500) analysis proved presence of aquatic biological sources,and also indicated that the CDOM in the waterbody of Lake Qianwei did not show any significant trace of terrestrial or aquatic biological origin. However,the ratio of a₃₅₅ and DOC showed a significant positive correlation with fluorescence index (r=0.787,n=10,P<0.01),suggesting a strong biological signal existed in the aquicultural zone,and it might come from phytoplankton production. 3-DEEM analysis show that humic-like components commonly existed in CDOM in this lake,and did not vary much in spatial distribution,while protein-like components did and presumably were the major factor affecting spatial distribution of CDOM.

An outdoor experiment was conducted for the inhibitory effect of Rhopalosiphum nymphaeae various in population density and growth stage on growth of water hyacinth,Eichhornia crassipes (Mart.) Solms. Results show that growth of water hyacinth was significantly inhibited by adult aphids,which was demonstrated in reduction of fresh plant weight,number of leaves and sprouts,and increase in the number of wizened leaves. R. nymphaeae feed on water hyacinth,thus affecting their growth. However the effect is positively related to their density,i.e. if the density is higher than 20 aphids per plant,the effect is significant and will become more and more significant as time goes by. But it should also be noted that R. nymphaeae have a relatively broad range of hosts and may endanger other aquatic plants in the neighborhood. Thus,the applicability of R. nymphaeae as natural enemy to control water hyacinth needs to be further studied.

Inhibitory effect of rice straw (Yanjing 9) on the growth of Microcystis aeruginosa and the inhibitory mechanism were studied. Results show that when 10 g·L^-1 or more of rice straw was added to M. aeruginosa liquid,both sterilized and un-sterilized rice straws could inhibit the growth of M. aeruginosa. In the sterilized group,the respiratory rate and SOD activity evidently increased firstly and then declined rapidly. The result of filter paper tests on solid medium show that among the extractives extracted by different organic solvents (petroleum ether,ethyl acetate and ether) from the leaching liquor of sterilized rice straw,ether extracts could be observed to have inhibitory effects on M. aeruginosa. This indicates that the algae-inhibition effect was caused by some substances in rice straw itself,rather than by microorganisms. Further study show that some organic acids and phenolic compounds in the ether extracts could inhibit the growth of M. aeruginosa. In addition,the smaller the fragments of rice straw were,the more obvious the inhibitory effect was,which might be related to the adsorption effect of rice straw.

Effects of soil Cd contamination on growth of Brassica chinensis in three different soils were investigated through greenhouse pot trial.Chemical fractions of cadmium (extracted by 0.43 mol·L^-1 HNO₃,0.05 mol·L^-1 EDTA and 0.01 mol·L^-1 CaCl₂) were evaluated by using a single extraction procedure. The results show that the Cd content in the aboveground part of Brassica chinensis had a nonlinear relationship with the metal in soils. It has been found that Cd content in the aboveground part of Brassica chinensis has negative correlation with soil pH values. The Cd mobility was in the order of Fe-accumulic Gleyic Stagnic Anthrosols>Typic Gleyic Stagnic Anthrosols>Lithic Ochri-Aquic Cambosols. 0.43 mol·L^-1 HNO₃,0.05 mol·L^-1 EDTA and 0.01 mol·L^-1 CaCl₂ extractable Cd were significantly correlated with the Cd content in the aboveground part of Brassica chinensis. Considering the simplicity and low cost of 0.43 mol·L^-1 HNO₃,0.05 mol·L^-1 EDTA or 0.01 mol·L^-1 CaCl₂ extraction,the extraction solutions could serve as an alternative method for assessment of phytoavailability of soil Cd to plants.

Antibiotics used in livestock and poultry production may be present in manure and slurry as the parent compound and/or metabolites. The environments may therefore be exposed to these antibiotics due to the application of animal manure to agricultural land. In order to understand the residue levels of antibiotics in livestock and poultry manures,and in agricultural soils after a long-term application of antibiotics-contained animal manure,both livestock and poultry manure samples as well as soil samples were collected from north Zhejiang Province. Concentrations of three selected tetracyclines,including chlorteracycline (CTC),tetracycline (TC),and oxytetracyline (OTC),in the samples were characterized. Residual levels of the TC,OTC,and CTC in manures varied from below determination limit to 16.75,29.60,and 11.63 mg·kg^-1,with their mean values at 1.57,3.10 and 1.80 mg·kg^-1,respectively. The residue level of selected antibiotics ranked from high to low as pig manure>chicken manure>cow manure,and the antibiotics residues were generally higher in animal manures from industrial scale farms than in those from farmer′s households. About 93%,88% and 93% of surface soils taken from the agricultural fields after application of manure contained OTC,TC,and CTC,respectively. The concentrations of the OTC,TC,and CTC in these soils ranged from below determination limit to 5.172,0.553,and 0.588 mg·kg^-1,respectively. The mean residues of the CTC,TC and OTC in the surface soils from agricultural fields treated with animal manures were 38,13,and 12 times as high as those from agricultural fields without manure application,suggesting that manure is an important source of antibiotics in the agricultural soils. The ratios of the OTC,TC,and CTC concentrations in the subsurface soils (20-40 cm) to those in the surface soils (0-20 cm) varied from to 2.13,0.02 to 1.91,and 0.02 to 1.36,with their mean values at 0.64,0.65,and 0.56,respectively. The residues of the CTC,TC,and OTC in the surface soils were positively correlated with clay content of the soils. The downward movement of antibiotics in sandy soils was more significant than in clayey soils,indicating that antibiotics is not stable but mobile in sandy soils.

A study was carried out using the sequential extraction method,on effect of application of heavy metals passivator on concentrations and forms of heavy metals in pig manure being composted aerobically under high temperature. Results show that after aerobic composting,concentrations of Zn,Cu,Pb,Cr,and As were increased,but the concentration of Hg was decreased significantly. Composting obviously stimulated transformation of Zn,Cu,Pb,Cr,As,and Hg,into forms low in activity,thus decreasing bio-availability of the heavy metals. Among the three heavy metal passivators,zeolit was the most effective in reducing bio-availability of Zn and Cu,sepiolite was the most effective in reducing bio-availability of Cr,and bentonite was the most effective in reducing bio-availability of Pb and Hg in pig manure. Therefore,zeolite,sepiolite and bentonite can be used to treat pig manure in composting to reduce the risk of heavy metal pollution of using pig manure in farmland.

An experiment was carried out on anaerobic digestion of cow-dung (CD) and kitchen waste (KW) mixtures different in ratio under 37 ℃ for 50 days. Results show that (1)when the mixture was formed at a ratio of 1/2 and 2/1,its actual biogas production potential was 0.66 and 0.71 L·g^-1,respectively,calculated on the basis of volatile solids total mass,about 50% and 29% higher than its weighted calculation,respectively; (2)the mean methane concentration of the four treatments varied in the range of 50%-55% in ratio and their mean bioenergy yielded in the range of 18.92-20.81 MJ·m^-3;(3)among the four treatments,Treatment CD1/KW2 was the highest in biogas generating efficiency. The biogas it generated in the first 10 days and 20 days accounted for 55.4% and 92.2% of the total it yielded,respectively; (4)the ultimate biodegradability of the 4 treatments,i.e. CD,CD2/KW1,CD1/KW2 and KW,was 46.99%,53.31%,70.12%,and 66.25%,respectively.

Sand samples were collected from Dengkou Section of the Wulanbuhe Desert,Inner Mongolia for analysis of forms and bioavailability of phosphorus with the six-step sequential extraction method and for classification of the sands. Results show that contents of total phosphorus (∑P_i) in the samples ranged from 172.88 to 316.67 μg·g^-1,with a mean of 251.32 μg.g^-1. The mean value of inorganic P(IP) and organic P (Or-P) content was accounting for 96.2% of ∑P_i and for 3.8% of ∑P_i,respectively. Ca-bound P was found to be the most abundant with a mean value being 233.72 μg.g^-1 (accounting for 93.0% of ∑P_i) in sand grains of all particle size fractions. The other forms of P followed a decreasing order of Or-P>Fe-P>Ads-P>Al-P>Obs-P in content. In the sand samples,contents of Ca-P,Fe-P and ∑P_i increased with decreasing of particle size,but Or-P was on the contrary,and no remarkable dependency relationship between content and sand particle size for Al-P,Ads-P and Obs-P was found. The quantity of bioavailable P was estimated at about 6.6% of ∑P_i and this fraction of P pool that actually is bioavailable under natural conditions will vary with natural water systems depending on a number of primarily physical and chemical environmental factors.

Aiming at the characteristics of water and nutrient management of rice cultivation,a model (precipitation-runoff-N loss simulation model,PRNSM) simulating rainfall-runoff-N-loss from paddy field was established with major parameters specified based on the data of field measurements and from the literature. Simulated calculation was carrid out on the basis of the daily precipitation data in the 56 years from 1951 to 2006,using a self-written computer program to study relationship of runoff and N loss therewith with rainfall in Nanjing. Results show that besides amount of rainfall and flux of runoff,interval between the date fertilizer was applied and the date relatively strong runoff took place was also a major factor affecting amount of N loss with runoff. Further analysis revealed that the first 7 days after fertilization is the key period to reducing N loss with runoff during the rice growth period,and transplanting rice in mid-June contributes to the reduction of N loss with runoff.

In August and September,2006,sparrows were caught from an industrial zone and a green area in Mudanjiang for analysis of heavy metal (Cd,Pb and Cu) contents in their feathers,livers,breast muscles and hearts. Results show that sparrows living in the industrial area have higher concentrations of heavy metals. Cd content is significantly correlated with Pb content in breast muscle,heart and liver (PPb>Cd. Hearts have higher Cu and Cd accumulation,while feathers higher Pb accumulation.