Table of Content

09 April 2010, Volume 29 Issue 04

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Articles

Light use efficiency within the canopies of subtropical evergreen needle-leaf plantations.

WANG Jun-Bang, ZHANG Xiu-Juan, HAN Hai-Rong

2010, 29(04):  611-616. 

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Taking the main afforestation tree species Pinus elliottii, P. massoniana, and Cunninghamia lanceolata in South China as test objects, their needles photosynthetically active radiation (PAR), net photosynthetic rate, and light use efficiency (LUE) at different canopy positions were measured with portable Li-6400 CO₂/H₂O infrared analyzer in July (mid growth period) and October (late growth period). For the  three tree species, their LUE at lower canopies was higher than that at upper canopies in July, but similar with or lower than that at upper canopies in October. North-facing needles had higher LUE than south-facing needles both in July and in October. Overall, the needles and LUE had stronger photosynthetic plasticity to light environment. The LUE of current-year needles was higher than that of one-year old ones. In July, the LUE of current year P. elliottii and P. massoniana needles was higher than that of one-year old ones, and the LUE of different-aged C. lanceolata needles was similar; but in October, the LUE of current-year P. massoniana needles was higher than that of one-year old ones, and the LUE of different-aged P. elliottii and C. lanceolata needles was similar. The photosynthes is of whole canopy was affected by the interaction of light availability and leaf age. It was suggested that forest could assimilate more carbon from atmosphere via adjusting its leaf LUE to adapt the light environment within canopy.

Species diversity and above-ground biomass of alpine vegetation in permafrost region of Qinghai-Tibetan Plateau.

2010, 29(04):  617-623. 

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Based on quadrat investigation,this paper studied the species composition of alpine vegetation in permafrost region of Qinghai-Tibetan Plateau, calculated the diversity index and evenness index,and approached the effects of permafrost degradation on the species diversity. During the permafrost degradation,the family number and species richness decreased,and the hygrophytes and mesophytes were gradually replaced by meso-xerophytes and xerophytes. Permafrost degradation lowered the species diversity and primary productivity,giving negative effects on the stability of alpine grassland ecosystem. There was a close parabolic relationship between species diversity and primary productivity.

Short-term responses of typical alpine plant species growth and reproductive characteristics to simulated climate change.

2010, 29(04):  624-629. 

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Alpine plant species are very sensitive to the climate change in their growth and reproductive characteristics,but few studies are made on it. In this paper,a reciprocal transplanted experiment was conducted along an altitude gradient from 3200 m to 3800 m at the south slope of Qilian Mountains in the northeast of Qinghai-Tibetan Plateau,aimed to understand the responses of typical alpine plant species growth and reproductive characteristics to simulated climate change. With the increase of the altitude,the mean annual air temperature decreased at a rate of 0.51 ℃/100 m,and the plant height,base leaf number,and maximum (minimum) leaf area had the peak values at 3400 m but lowered at other three altitudes. The responses of reproductive strategies such as reproductive branch number,flower number,and reproductive input were not obvious,but had a decreasing trend with increasing altitude. The results confirmed the hypothesis that climate change had more obvious effects on plant growth than on its reproductive characteristics.

Leaf surface wettability of major plant species for urban greening in Xi’an and related affecting factors.

2010, 29(04):  630-636. 

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We measured the contact angle of water droplet on leaf surfaces of 21 major plant species for urban greening in Xi’an, and studied the effects of leaf surface characteristics such as epidermal wax, trichomes, and stomata on the contact angle. There existed significant differences in the contact angle among test plant species and between adaxial and abaxial leaf surfaces. The contact angle ranged from 40°  to 140°, and was negatively correlated with its coefficient of variance. The greater variance of the contact angle on wettable leaves could be related to the greater effects of dust, acid rain, and other environmental substances on the leaf surface structure; while for nonwettable leaves, the relatively short retained time of environmental substances gave smaller effects on the leaf surface structure and composition. The contact angle increased with increasing epidermal wax content. After the removal of epidermal wax by chloroform, the leaf contact angle of most plant species, especially of hydrophobic species Ginkgo biloba, Rosa chinensis and Berberis thunbergii, decreased significantly. On the contrary, the removal of epidermal wax increased the leaf contact angle of a few hydrophilic species, such as the adaxial and abaxial leaf contact angle of Ligustrum lucidum and the abaxial leaf contact angle of Populus canadensis. The amount, morphology, and distribution of trichomes had great effects on the leaf contact angle. Different types of action pattern led to different wetting characteristics. Artificial removal of trichomes increased the leaf surface wettability. The stomatal density of abaxial leaf surface was negatively correlated with  guard cell length and stomatal pore length, while the contact angle of abaxial leaf surface was negatively correlated with  stomatal  density and positively with stomatal pore length.

Cause of large-scale Haloxylon ammodendron degeneration in west Grurbantonggut Desert.

2010, 29(04):  637-642. 

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Based on the investigation of the characteristics of degenerated Haloxylon ammodendron populations, soil physical and chemical properties, and groundwater level in west Gurbantonggut Desert, a cause analysis was made on the degeneration of H. ammodendron in the area. In the study area, most of the soils were heavily salinized, and the trees and seedlings were sparse, with an average coverage being only 11.58%. The age structure diagram indicated that the H. ammodendron populations were in declining. There was a significant negative correlation between the individual viability of H. ammodendron and the soil conductivity in 0-40 cm and 40-80 cm layers (r=-0.79, P=0.000; r=-0.32, P=0.009), and a significant positive correlation between the individual viability and the soil moisture content in 80-120 cm layer (r＝0.54, P=0.000). The survival index and coverage of the H. ammodendron populations were significantly correlated with groundwater level (r²=0.40, P=0.007; r²=0.46, P=0.004). It was concluded that the declining groundwater level, inadequate soil moisture, and high soil salt content were the main factors causing H. ammodendron degeneration.

Changes of community structure and leaf area index during vegetation secondary succession in Juci Mountain.

2010, 29(04):  643-648. 

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By using 3S (GIS, RS and GPS) technology and field survey data, this paper studied the process of vegetation secondary succession after human interference in Juci Mountain, and analyzed the changes of community structure and leaf area index (LAI) at different stages of the vegetation succession from the macro- and micro aspects. The average LAI at tree stage was 4.1-5.5, at shrub stage was 3.0-3.7, and at herb stage was 1.0-1.5. The LAI and coverage of some shrubs in growth season were higher than those of trees. With the succession went on, the community structure also changed greatly. Both the quantity and the species number of trees increased gradually. The complexity and stability of vegetation system increased with succession, and the ecological function and ecosystem service value improved accordingly.

Occurrence patterns of high temperature at booting and flowering stages of rice in the middle and lower reaches of Yangtze River and their impacts on rice yield.

2010, 29(04):  649-656. 

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Taking 19 regions of 7 provinces and municipalities in the middle and lower reaches of Yangtze River as the objects, this paper analyzed the temporal and spatial distribution patterns of their daily maximal temperature over 35 ℃ from the 15th day before rice booting to the 20th day after rice flowering in last 36 years (1970-2005). According to the climate transient scenarios of these regions in 2030 and 2050 generated by GISS GCM Transient B Runs, the temporal and spatial evolving tendency of the daily maximal temperature over 35℃ was further discussed. In last 36 years, the day number of high temperature at the booting and flowering stages of early rice in the middle and lower reaches of Yangtze River increased significantly, and under the future climate scenarios, the day number of high temperature would be the largest for single-cropping rice, followed by for early rice and late rice. For double-cropping rice production areas, the day number of high temperature in the middle reaches would be larger than that in the lower reaches of Yangtze River. The relationships between the regional quantity of rice climate yield and the stress-index occurrence pattern in the same regions suggested that the rice-spikelet abortion due to high temperature was the main cause for the decrease of rice yield. In the two climate transient scenarios in 2030 and 2050, the yield decrement in the middle reaches of Yangtze River would be larger than that in the lower reaches, and the largest yield decrement would be the late rice in the middle reaches of Yangtze River.

Short-term subtle forecast and early warning methods for cold (freezing) damage of fruit trees in Fujian Province.

2010, 29(04):  657-661. 

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Based on the 1963-2008 meteorological data from 68 weather stations in Fujian Province, and by using mathematic statistics and GIS technique, the short-term subtle forecast and early warming methods for cold (freezing) damage of fruit trees in the province were approached. The forecast period for cold (freezing) damage of fruit trees was from early December to next early February, and the key period for warning low temperature was from mid December to next mid January. The short-term forecast equations for the minimum daytime temperature in Fuzhou, Xiamen, and Shaowu were established by stepwise regression analysis, which could be used for the forecast of short-term minimum temperature by all of the meteorological observation stations in Fujian Province by means of differential algorithms. Based on the data of longitude, latitude, and altitude, the geographical relational prediction model of the minimum daytime temperature was established, and the distribution map of forecasted low temperature was drawn with GIS technology, which could subtly forecast the minimum daytime temperature of whole Fujian Province. In combining with the cold (freezing) damage indices of fruit trees such as litchi, longan, and banana in southern subtropical monsoon climate zone, the forecast information of warning cold (freezing) damage of fruit trees were popularized, and the occurrence, development, and range of cold (freezing) damage for fruit trees were forecasted in short-term. By means of differential algorithms, the short-term minimum temperature was forecasted by all weather stations in the Province in 2009, and the forecast accuracy of ≤1 ℃, ≤1.5 ℃, and ≤2 ℃was 58.3%, 83.3%, and 91.7%, respectively. It could be seen that our short-term forecast model possessed a certain forecast capability, and could be used for the quantificational forecasting of low temperature in winter.

Effects of exogenous calcium on the abundance and activity of ADH and LDH isoenzymes in cucumber seedlings root under root-zone hypoxia stress.

2010, 29(04):  662-668. 

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A hydroponic experiment was conducted to study the effects of exogenous calcium, LaCl₃, and trifluoperazine (TFP) on the abundance and activity of alcohol dehydrogenase (ADH) and lactate dehydrogenase (LDH) isoenzymes in cucumber seedlings under hypoxia stress. Hypoxia induced the formation of new ADH and LDH isoenzyme bands. Under hypoxia stress, the abundance and activity of ADH and LDH isoenzymes were significantly higher than those of the control. Increasing exogenous Ca²⁺ concentration was conducive to the Ca²⁺ signal formation and the adversity signal transduction. The application of 4 mmol CaCl₂·L^-1 alleviated the hypoxia stress significantly, and made the abundance and activity of ADH and LDH isoenzymes closed to the control level. La³⁺ inhibited the Ca²⁺ uptake and its in vivo transport. Applying 50 μmol·L^-1 of LaCl₃ decreased the abundance and activity of ADH and LDH isoenzymes significantly, inhibited the growth of cucumber seedlings, and made the plant biomass be significantly lower than that under hypoxia, implying that La³⁺ increased the hypoxia injury of cucumber seedlings. TFP inhibited the hypoxia signal transduction. Applying 20 μmol·L^-1 of TFP made the abundance and activity of ADH and LDH isoenzymes be significantly lower than those under hypoxia, inhibited the growth of cucumber seedlings, and decreased the hypoxia tolerance of the seedlings, which implied that TFP also increased the hypoxia injury of cucumber seedlings. Our results suggested that exogenous Ca²⁺ could regulate the anaerobic respiration process of cucumber roots under hypoxia stress. The exogenous Ca²⁺ increased the in vivo transport of Ca²⁺, alleviated the hypoxia injury, and enhanced the plant tolerance against hypoxia stress.

Allelopathy of different treated residues of Ambrosia artemisiifolia L. on wheat growth.

2010, 29(04):  669-673. 

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Ambrosia artemisiifolia L. is a major invasive weed in many regions of the world, and has significant impact on agricultural ecosystems. This paper studied the allelopathic effects of the burned and unburned A. artemisiifolia residues and their water extracts on wheat growth, aimed to approach whether burning could eliminate or weaken the allelopathic effects of A. artemisiifolia residue. Both the residue and its water extracts had inhibitory effects on the early growth of wheat, but the impact of the residue was smaller than that of the extracts, suggesting that the allelochemicals in A. artemisiifolia residue were water-soluble, and water extraction could release the allelochemicals into soil to a great extent. The addition of the residue also made the soil physical and chemical properties changed. With the increasing amount of added A. artemisiifolia residue, the soil pH, conductivity, organic carbon content, and the contents of phenolic compounds (main components of allelochemicals) all increased to some extent, which in integration inhibited wheat growth. Both the burned and unburned residues inhibited wheat growth significantly, and no significant difference was observed between the residues. Therefore, it was not the good way to burn the A. artemisiifolia residue to eliminate its allelopathic effects on native plants.

Physiological responses of Alopecurus aequalis to herbicide haloxyfop-R-methyl.

2010, 29(04):  674-679. 

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Alopecurus aequalis is a troublesome weed in oilseed rape field, and herbicide haloxyfop-R-methyl is often used for its control. A rapid identification by the method of seed bioassay showed that A. aequalis biotype JXRII had the resistance to the herbicide, while biotype type JJSII was in adverse. In order to approach the differences in the physiological responses of the two biotypes to the herbicide, haloxyfop-R-methyl was sprayed on them, and some important physiological indices were determined. Two days after spraying haloxyfop-R-methyl, the leaf glutathione (GSH) content of JJSII decreased gradually, while that of JXRII increased. After spraying haloxyfop-R-methyl for 6 days, the leaf electrolytic leakage and malondialdehyde (MDA) content of JJSII increased markedly, and the chlorophyll (Chl) and carotenoid (Car) contents decreased. On the contrary, the leaf electrolytic leakage and the leaf MDA, Chl, and Car contents of JXRII had no significant differences with the control. Spraying haloxyfop-R-methyl increased the leaf soluble sugar content of the two biotypes, but the increment was much more for JJSII than for JXRII. It was suggested that haloxyfop-R-methyl strongly affected the physiological aspects of susceptible biotype of A. aequalis, while the resistant biotype had some physiological adaptability to the herbicide stress.

Effects of different concentration avermectin on the catalase and glutathione-S-transferase activities of common carp.

2010, 29(04):  680-686. 

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A laboratory experiment was conducted to study the effects of different concentration (0, 3.2, 5.6, 7.5, 10.0, and 18.0 μg·L^-1) avermectin on the catalase (CAT) and glutathione-S-transferase (GSTs) activities of common carp (Cyprinus carpio). Both the CAT and the GSTs activities in the muscle and liver-pancreas of common carp in all but 3.2 μg·L^-1 dose groups were significantly affected. The enzyme activities were induced when the avermectin concentration was low, but inhibited when the avermectin concentration was high. The CAT activity in the muscle of common carp in 5.6 μg·L^-1 and 7.5 μg·L^-1 dose groups had little difference with the control, but the CAT activity in the liver-pancreas and the GSTs activity in the muscle and liver-pancreas of common carp in 5.6 μg·L^-1 and 7.5 μg·L^-1 dose groups increased significantly, compared with the control. Both the CAT and the GSTs activities in the muscle and liver-pancreas of common carp in 10.0 μg·L^-1 and 18.0 μg·L^-1 dose groups had a significant increase first, and decreased significantly then. When the common carp was transferred to aquaria with no avermectin for 10 days, both the CAT and the GSTs activities in the muscle and liver-pancreas of the common carp in all dose groups except in 18.0 μg·L^-1 dose group were recovered to the levels of the control group, which meant that high concentration avermectin might have an irreversible damage to the fish. There existed dose-effect relationships between the avermectin concentration and the CAT and GSTs activities in the muscle and liver-pancreas of common carp, suggesting that the CAT and GSTs activities in the muscle and liver-pancreas of common carp could be used as the biomarkers to monitor the avermectin pollution of water body. Meanwhile, the CAT and GSTs activities in the liver-pancreas of common carp exposed to avermectin changed much more markedly than those in the muscle, and thus, the liver-pancreas was the better sampling organ when the CAT and GSTs activities were used as the biomarkers.

Seasonal variations of bedding site characteristics of Gazella subgutturosa in Kalamaili Mountain Nature Reserve.

2010, 29(04):  687-692. 

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In 2007, an investigation was made on the seasonal variations of the bedding site characteristics of Goitred gazelle (Gazella subgutturosa) in Kalamaili Mountain Nature Reserve. Mann-Whitney U test, Kolmogorov-Smirnov Z test, Kruskal-Wallis test, one way ANOVA and principal component (PCA) analysis were used for the multivariate analysis of variables. In the bedding site, the vegetation height, Ceratoides latens density, shrub coverage, and ground biomass in spring, the vegetation height and ground biomass per unit area in summer, and the vegetation height, shrub coverage, and species richness in autumn were significantly higher than those in the random plots. Principal component analysis showed that the key environment factors determining the selection of bedding site by G. subgutturosa in spring, autumn, and winter were food, concealment, and temperature. Analysis of one way ANOVA showed that there existed significant differences in the bedding site characteristics among the three seasons, especially between spring and summer, and between spring and autumn. The variations of food resources and environment temperature were the major factors inducing the seasonal variations of the bedding site characteristics, and the bedding site selection of G. subgutturosa had some relationships with its own thermoregulation.

Cloning and inter-specific altered expression of heat shock gene Hsp70 in two invasive whiteflies in response to thermal stress.

2010, 29(04):  693-701. 

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To investigate whether the heat shock gene 70 (Hsp70) in Bemisia tabaci B-biotype and Trialeurodes vaporariorum has different expression profile in response to temperature stress, the full length cDNA of the Hsp70in the two whitefly species was cloned, and the expression profile of the Hsp70 across a temperature gradient was analyzed by real-time quantitative PCR. The Hsp70gene of both B. tabaci B-biotype and T. vaporariorum, named BTHsp70 and TVHsp70 (GenBank accession nos: DQ093385 and EU861391, respectively), had TATA-box-like elements in 5’-UTR, poly(A) signals AATAA in 3’-UTR, and three highly conserved functional motifs of the Hsp70 protein family in deduced amino acid sequences. Across the temperature gradient (from -19 to 46 ℃), the onset temperature (T_on) or maximal temperature (T_max) for inducing Hsp70 expression in T. vaporariorumwas 2.5 ℃-7.5 ℃ lower than those for the expression in B. tabaci B-biotype. All the results revealed that the cloned genes were of inducible Hsp70 gene, and, in terms of gene expression level, T. vaporariorum was more cold-tolerant than B. tabaci B-biotype, while the latter was more heat-tolerant. The T_on (or T_max) of the Hsps could represent the differences in temperature tolerance of these two whitefly species. To some extent, our results explained the different geographical distribution and seasonal occurrence of the two whitefly populations in nature.

Correlation analysis on virioplankton abundance and its environmental factors in Apostichopus japonicus culture pond.

2010, 29(04):  702-710. 

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To reveal the relationships between virioplankton abundance and environmental factors in sea cucumber (Apostichopus japonicus) culture pond ecosystem, the virioplankton abundance in an A. japonicusculture pond of Xietun near Dalian City was determined from March to November 2008. In the meantime, the environmental factors such as water temperature, pH, dissolved oxygen, salinity, chlorophyll a, chemical oxygen demand, inorganic nitrogen and phosphorus, and heterotrophic bacterioplankton were monitored, with the relationships between the virioplankton abundance and these environmental factors analyzed. In the A. japonicus culture pond, the virioplankton abundance was the highest (18.2×10¹⁰ VLPs·L^-1) in April and the lowest (1.31×10¹⁰ VLPs·L^-1) in November, with an average of 8.32×10¹⁰ VLPs·L^-1; while in outer sea, the virioplankton abundance was the highest (12.6×10¹⁰ VLPs·L^-1) in April and the lowest (2.02×10¹⁰ VLPs·L^-1) in June, with an average of 6.45×10¹⁰ VLPs·L^-1. The main environmental factors affecting the virioplankton abundance in the A. japonicus culture pond were nutrients, water temperature, pH, and salinity; while those affecting the abundance in outer sea were chlorophyll a and heterotrophic bacterioplankton.

Dynamic changes of soil trace elements under different fertilization modes.

2010, 29(04):  711-716. 

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Taking an 18-year field experiment in the lower reach of Liaohe River Plain as a platform, this paper analyzed the dynamic changes of trace elements in aquic brown soil under different fertilization modes. Fertilization had little effects on the concentrations of soil total trace elements, but affected the concentrations of soil available trace elements significantly. Treatment NPK+pig manure (M) had the highest concentrations of soil available trace elements, followed by treatments NPK, M, and CK. In all treatments, the budgets of soil trace elements were negative, with the deficit being NPK+M<M<CK<NPK, suggesting that applying chemical fertilizers alone aggravated the deficit, while applying organic manure could mitigate the deficit. The trace elements in test soil could be transformed from available pool to non-available pool and vice versa, depending on the budgets and the concentrations of soil available trace elements.

Correlations among CO₂, CH₄, and N₂O concentrations in soil profiles in central Guizhou Karst area.

2010, 29(04):  717-723. 

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From June 2006 to May 2007, the monthly CO₂, CH₄, and N₂O concentrations in soil profiles in central Guizhou Karst area were measured, with their spatiotemporal correlations analyzed. The CO₂ and N₂O concentrations in the soil profiles were 0.35-35.3 ml·L^-1 and 0.31-5.31 μl·L^-1, respectively, being higher in summer and autumn than in winter and spring, and the CH₄ concentration was 0.1-4.7 μl·L^-1, with no significant difference among seasons. With the increase of soil depth, the CO₂ and N₂O concentrations increased first and then decreased or tended to be stable, while CH₄ had an inverse trend unlike CO₂ and N₂O. The spatiotemporal distribution of CO₂ in the soil profiles was significantly positively correlated with that of N₂O, but negatively correlated with that of CH₄; while the spatiotemporal variations of CH₄ and N₂O were negatively correlated, being significant in Huaxi grassland, Qingzhen hardwood forest, and forest park Pinus massoniana forest and hardwood forest.

Phosphorus adsorption and desorption characteristics of wetland soil under different redox conditions.

2010, 29(04):  724-729. 

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A laboratory simulation experiment was conducted to study the phosphorus adsorption/ desorption characteristics of wetland soil in Panjin, Liaoning Province under different redox conditions. Langmuir model and Freundlich model were used to fit the phosphorus  desorption processes. Under both anaerobic and aerobic conditions, the phosphorus adsorption/ isotherms could be successfully fitted by the two models, and Langmuir model had better fitting effect. Under flooding, the maximum phosphorus adsorption and desorption rates decreased, with an average decrement being 9.5% and 16.3%, respectively, while the phosphorus adsorption/ desorption equilibrium mass concentration increased remarkably, with an average increment of 158.8%. The soil amorphous Fe content also increased obviously after flooding, and had significant correlation with the phosphorus adsorption desorption equilibrium mass concentration but less correlation with the maximum phosphorous adsorption and desorption rates, suggesting that soil amorphous Fe was one of the most important factors affecting the phosphorus adsorption/ desorption equilibrium mass concentration under flooding.

Effects of Bellamya aeruginosa bioturbation on nutrient fluxes across sediment-water interface of algal bloom water body.

2010, 29(04):  730-734. 

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A one-month laboratory experiment was conducted to study the effects of Bellamya aeruginosa bioturbation on the sediment oxygen consumption rate and overlying water nutrient fluxes in a simulated algal bloom water body. Three treatment groups and one control group were set up in the experiment, according to the stocking density of B. aeruginosa. Throughout the trial period, the sediment oxygen consumption (SOC) rate in treatment and control groups declined significantly. The SOC rate in treatment groups was higher than that in control group at the initial stage of the experiment, but lower than that in the control group at the late stage of the experiment. The treatment groups with high density B. aeruginosa showed a higher SOC rate than the treatment groups with low-density B. aeruginosa. In control group, ammonium always released from the sediment to the overlying water, and the release rate decreased gradually; while in treatment groups, ammonium was released to the overlying water at initial stage but absorbed by the sediment at middle and late stages of the experiment. Except at the initial stage of the experiment, the fluxes of nitrite and nitrate in all treatment groups and control group were mainly released to overlying water, and there was a significant difference between treatment group 1 and control group. Phosphate was released from the sediment at early stage, and was absorbed into sediment by the end of the experiment. This study revealed that the bioturbation of B. aeruginosa increased the SOC rate at the beginning but decreased the SOC rate by the end of the experiment, and the existence of B. aeruginosa enhanced the overall sediment nitrification rate, consequently speeded the sediment-water N cycling.

Effects of Sophora flavescens decayed products on eggplant growth and soil biological activity under phenolic acids stress.

2010, 29(04):  735-740. 

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A pot experiment was conducted to study the effects of Sophora flavescens decayed products on the growth of eggplant (Solanum melongena) and the microbial populations and enzyme activities in its rhizosphere soil under the stress of vanillin and cinnamic acid. Compared with the control, the addition of S. flavescens decayed products promoted the plant height and stem diameter of S. melongena, and increased the amounts of microbial populations, especially of bacteria and actinomycetes, in rhizosphere soil. With the increasing stress of vanillin and cinnamic acid, the amounts of bacteria and actinomycetes in rhizosphere soil decreased after an initial increase, while that of fungi was in reverse. The addition of S. flavescens decayed products also increased the activities of catalase, polyphenol oxidase, and urease in rhizosphere soil, which had the same variation trend as the amounts of bacteria and actinomycetes with the increasing stress of test phenolic acids.

Soil labile organic carbon of different land use types in a reclaimed land area of Taihu Lake.

2010, 29(04):  741-748. 

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Reclaiming land from lake is a kind of human disturbance emerged in large numbers in China since the 1950s. Taking the Xiaodian Lake area in Taihu Lake as a case, this paper measured the concentrations and proportions of microbial biomass carbon (MBC), water soluble organic carbon (WSOC), readily oxidizable carbon (ROC), and particulate organic carbon (POC) in 0-40 cm soil layer after 35 years of reclaiming and under different land use types, aiming  to understand the characteristics of soil labile organic carbon in the reclaimed land area of Taihu Lake. The concentration and proportion of soil MBC in cropland were significantly higher than those in three kinds of forestland, with its concentration in 0-10, 10-20, 20-40 cm layers being 573.38±18.28, 335.52±53.35, and 109.33±4.86 mg·kg^-1, and 2.07, 2.02, and 1.39 times higher than that in Cinnamomum camphora forestland, 2.26, 2.79, and 2.01 times higher than that in Metasequoia glyptostroboides forestland, and 1.89, 2.10, and 1.21 times higher than that in Phyllostachys heterocycla forestland, respectively, which indicated that the disturbance of cultivation and fertilization in cropland had great effects on soil microbial activity. No significant differences in the concentrations and proportions of soil WSOC, ROC, and POC were observed between cropland and  Compared with those in the mountain forestlands of the same climate zone, the proportions of soil WSOC (1.22%-3.03%) and ROC (10.56%-30.64%) in the reclaimed land area were higher, but the proportion of soil POC (3.43%-17.28%) was lower, implying that the soil organic carbon in reclaimed land had a poor stability. As a kind of human disturbance, reclaiming land from lake altered the carbon cycle of natural ecosystem significantly, which should be taken into full account.

Optimization of water sources for harvesting rainwater in Loess Plateau.

2010, 29(04):  749-753. 

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To improve the water quality and make sure the drinking safety of cellar water in Loess Plateau, the selection of the water sources for harvesting rainwater is imperative. By the method of principal component analysis (PCA), this paper determined the high-quality rainwater sources and the related control indices. Among the different types of test water sources, cement ground and tile roof were the better fields for harvesting rainwater, with their integrated principal component scores being -3.350 and -1.945, respectively. The indices COD, NH₄⁺-N, TP, SS, and fecal coliform had high load values in the main components. The harvested rainwater was mainly pollutted by organic matter, surface dust, and animal and/or human excreta, which obviously related to human activities. Some improvement measures and recommendations for the source rainwater were also proposed from the aspects of policies and regulations, water quality protection technology systems, and water quality testing and protection.

Seasonal changes of soil nutrient supply and enzyme activities in navel orange orchards of south Jiangxi.

2010, 29(04):  754-759. 

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Taking three navel orange orchards varied in stand age but similar in fertilization mode in south Jiangxi as test objects, this paper studied the seasonal changes of their soil nutrient supply and enzyme activities. The soil organic carbon (OC), total nitrogen (TN), and total phosphorus (TP) contents all increased with stand age. Soil sucrase activity was higher in the 20-year-old orchard than in the 9- and 31-year-old orchards, soil urease activity was in reverse, and soil acid phosphatase activity had no significant difference among the three orchards. The increase of soil OC, TN, and TP contents with stand age was not consistent with their transformation rates based on the determinations of soil enzyme activities, e.g., in 31-year-old orchard, the transformation rates of soil C and N had a decreasing trend. In addition, the seasonal changes of soil sucrase, urease, and acid phosphatase activities did not meet the seasonal shifts of the orange tree’s nutrient demands, i.e., C accumulation in early winter, N need in spring and summer, and P transfer in late autumn and early winter. It was deduced that the lower transformation rate of soil nutrients, imbalance of soil N and P supply, and inconsistency between the seasonal changes of soil nutrient supply and plant nutrient demand would be the main causes inducing the decrease of productivity and the decline of fruit quality in elder navel orange orchards of south Jiangxi.

Landscape heterogeneity of land use types in Shiyang River basin.

2010, 29(04):  760-765. 

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With the support of GIS technology and taking the TM/ETM remote sensing images as the data source, 14 types of landscapes in Shiyang River basin were obtained by using the artificial interpretation method. A series of other data such as digital elevation model (DEM), vegetation maps, and land use maps were used, and the theories and methodologies of landscape ecology as well as the landscape spatial pattern index were adopted to analyze the landscape heterogeneity of desert and oasis ecosystems in Shiyang River basin. Cropland, woodland, grassland, and sandy land were the main landscape types and structural elements in the basin, with an average relative frequency of >42%. In desert landscape ecosystem, the matrix of sandy land was of heterogeneity in homogenization direction, while in oasis landscape ecosystem, the matrix of woodland, grassland, and cropland  was of heterogeneity in heterogenization direction. The relative frequency of river system as a corridor was very small in both desert and oasis landscape systems. The matrix of patch and corridor displayed heterogeneity in heterogenization directions. This study would be helpful to the monitoring of land use change and environmental change in arid interior region.

Characteristics and cause analysis of land use/cover change in Dunhuang City.

2010, 29(04):  766-775. 

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By using ArcGIS 9.2 software in combining with field survey, the Landsat5-TM remote sensing images of Dunhuang City in 1987, 1996, and 2007 were interpreted. A total of eight land use/cover types were obtained, and the characteristics and causes of the land use/cover change were analyzed. In the past 20 years, the vegetation coverage in the City had a declining trend, and the coverage area was decreasing. Among the eight land use types, the cropland, urban construction land, and non-vegetation land had a net increase in their area, while the other five land use types presented a net decrease. There were inter-conversions among the eight land use types, and the main directions were: parts of grassland and non-vegetation land transformed into croplands, parts of wetland and shrub land transformed into grassland, and high coverage grassland was successively transformed into medium coverage grassland, low coverage grassland, and non-vegetation land. Except that the vegetation coverage in the edge area of cropland had somewhat increase, the vegetations in the other areas degenerated obviously. Elevated air temperature was the important natural factor affecting the land use/cover change, and land reclamation and irrigation were the important human factors affecting this change.

Effects of seawater irrigation and nitrogen fertilization on the growth of grain amaranth in tidal flat of north Jiangsu Province.

2010, 29(04):  776-782. 

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To establish a complex clean production model of seawater planting and raising in saline mudflat, it’s necessary to explore the conditions of cultivating economic crops under seawater irrigation. In this paper, a field plot experiment was conducted to study the coupling effects of seawater irrigation and nitrogen (urea N) fertilization on the yield, ion distribution, and total nitrogen content of grain amaranth in the coast of north Jiangsu Province. Under 20% seawater irrigation, the fresh mass and grain yield in treatment 120 kg N·hm^-2 increased significantly, compared with those in treatment 60 kg N·hm^-2, and the grain yield had no significant difference with that in treatment 180 kg N·hm^-2. Under 40% seawater irrigation, the grain yield in treatment 120 kg N·hm^-2 was the highest, but still significantly lower than that under 20% seawater irrigation and in treatment 120 kg N·hm^-2. Under freshwater irrigation, the grass yield was the highest in treatment 60 kg N·hm^-2, while the grain yield was the highest in treatment 180 kg N·hm^-2. Under 20% seawater irrigation and in treatment 120 kg N·hm^-2, the grain yield and grass yield were not significantly different from the highest values. With increasing N fertilization rate, the K⁺ content in stem and leaf increased, while the Na⁺ and Cl^- contents in root, stem, and leaf increased after an initial decrease. The K⁺/Na⁺ ratio in stem was increased with the increasing N fertilization up to 120 kg·hm^-2, but decreased when the N fertilization increased to 180 kg N·hm^-2. Under 20% seawater irrigation, the total N content in leaf was the highest in treatment 120 kg N·hm^-2; while under 40% seawater irrigation, nitrogen fertilization rate had less effect on the total N content in leaf. It was concluded that in the coastal beach of north Jiangsu, 20% seawater irrigation and 120 kg N·hm^-2 fertilization could significantly improve the salt tolerance of grain amaranth, and increase its economic yield.

Research advances in soil nitrogen transformation as related to drying/wetting cycles.

2010, 29(04):  783-789. 

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This paper summarized the research progress in the effects of drying/wetting cycles on the mineralization, transformation, and losses of soil nitrogen
, and on the soil aggregate structure, swelling-shrinking characteristics, microbial activity, and microbial community. It was indicated that soil drying/wetting cycles could affect the mineralization and losses of soil nitrogen, and the transformation of soil nitrogen was closely related to the soil aggregate structure, swelling-shrinking characteristics, microbial activity, and microbial community. The future research directions were also proposed, with the focus on the relationships between soil nitrogen transformation and soil physical and microbial characters, especially the microbial transformation of fertilizer nitrogen, so as to provide theoretical references for the further study of soil nitrogen transformation processes and mechanisms.

Research progress in affecting factors of stem CO₂ efflux rate.

2010, 29(04):  790-797. 

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Stem CO₂ efflux rate (F_CO2) is a key component of the carbon cycle in forest ecosystem, accounting for 14%–48% of autotrophic respiration. To study the affecting factors of F_CO2 would contribute to the understanding of global carbon cycle and of the responses of forest ecosystem to global climate change. This paper reviewed the effects of biotic and abiotic factors on F_CO2, and indicated that these factors not only directly or indirectly affected the F_CO2, but also acted interactively. Their contributions to F_CO2 varied temporally and spatially. Though a considerable advancement has been achieved in recent years, some issues are still needed to be further studied: 1) partitioning the F_CO2 with effective methods, and analyzing the relationships between the F_CO2 components and related affecting factors to reveal the F_CO2 variation mechanism, 2) incorporating the biotic and abiotic factors into F_CO2 dynamic models to improve the accuracy of simulating F_CO2, and 3) further approaching the temperature-adaptability of F_CO2.

Source-receptor models for atmospheric mercury: A review.

2010, 29(04):  798-804. 

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The behaviors of mercury in atmosphere play a significant role in global mercury biogeochemical cycling, while anthropogenic activities, such as fossi
l fuel combustion, cement production, chlorine-alkali cell manufacturing, and iron-steel processing have been the main sources of atmospheric mercury. Under definite conditions, the atmospheric mercury can be dry- or wet-deposited, giving greater effects on certain local environments (receptors). For example, significant spatial mercury deposition gradients are observed in urban and industrial areas, and larger amount of mercury deposition appears nearby the anthropogenic sources. Therefore, using a multi-element tracer approach to analyze the sources of atmospheric mercury becomes a main field in atmospheric mercury study. This paper described the development of receptor models for the source analysis of pollutants, and summarized the achievements of the application of source-receptor models in atmospheric mercury study. The establishment and application of source-receptor models in analyzing the atmospheric mercury in China were proposed.

Disturbances of urbanization to river course system and related ecological restoration principles and approaches.

2010, 29(04):  805-811. 

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The rapid development of urbanization brings large volume of waste water to the environment, and its disturbances to natural ecosystem may break the structure and the balance of original ecosystems. Much attention has been paid on the resulted environmental effects, but how to restore a healthy river course system is still lacking scientific methodology. In this paper, the disturbance types and characteristics of urbanization on river course system, the key processes affecting river course system health, and related ecological restoration principles and approaches were elaborated. In general, there are three characteristics of the disturbances on river course system, i.e., structural fixation, shape regulation, and function simplification. The key processes affecting river course system health are the stoppage of substance exchange path, the destruction of wildlife habitat, and the imbalance of river eco-hydrological processes. Following six principles have to be followed when restoring river course system, i.e., 1) nature-based principle, 2) key function-steered principle, 3) spatial and temporal scaling principle, 4) consideration of ecological circulation and balance, 5) public participation of stakeholders, and 6) optimization of comprehensive benefits. The development directions, approaches, and spatiotemporal scale issues related to the ecological restoration of river course system were analyzed.

Influence of benthic fauna on mangrove ecosystem and its ecological significance.

2010, 29(04):  812-820. 

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Benthic fauna is an important component of mangrove ecosystem. This paper summarized the research progress in the biodiversity and distribution of mangrove benthic fauna and related biotic and abiotic affecting factors, and discussed the influence of benthic fauna, especially Sesarmidae crabs, on the structure and function of mangrove ecosystem from the aspects of 1) maintenance of ecosystem primary productivity, 2) enhancement of ecosystem organic matter production, 3) effects on mangrove growth, 4) mitigation of saplings competition stress, and 5)altering sediment properties. In addition to the traditional studies in assemblage structure, biodiversity, and idiobiology, the current researches on the ecology of mangrove benthic fauna are paying more attention on the interactions between the benthic fauna and other marine invertebrates (e.g. Ocypodidae), and the intra- and inter-relationships between benthic fauna and its habitats. It is necessary to further understand the significance of crabs’ biotrubation in the natural regeneration of mangrove and the energy flow of mangrove ecosystem.

Physiological and biochemical responses of different rice cultivars to cadmium stress in tropical region of China.

2010, 29(04):  821-825. 

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Taking the main rice cultivars Boyou 225 and Ainuo (glutinous rice) in tropical region of China as test objects, a pot experiment was conducted to study their tolerance to three levels of soil cadmium (Cd) stress. Under the stresses of Cd, the Cd accumulation in the cultivars was in order of root > stem > rice husk > kernel. With the increasing concentration of soil Cd, cell membrane was more damaged, and the membrane permeability was slightly higher for Ainuo than for Boyou 225. The increase of soil Cd concentration increased the leaf malondialdehyde (MDA) and proline contents and SOD and POD activities, with the increment being obviously higher for Boyou 225 than for Ainuo, and decreased the catalase (CAT) activity. These results suggested that under the same Cd stress, Boyou 225 suffered Cd poison more severely than Ainuo.

Application of RAGA-based PPC model in eco-aesthetics assessment of urban park green space landscape.

2010, 29(04):  826-832. 

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Based on the increasing public awareness of environmental issues and with the guidance of eco-aesthetics ideology, the authors proposed an eco-aesthetics assessment index system of urban park green space landscape, and applied the RAGA-based PPC model to transform the multi-dimension data into low-dimension space, aimed to search for the optimum projection direction and the projection function value to realize the eco-aesthetics assessment of urban park green space landscape. The assessment index system and the model were then used to make landscape eco-aesthetics assessment of ten representative urban park green spaces in Daqing City. The results showed that the general landscape space diversity, vegetation color diversity, building and furniture arrangement rationality, tree species diversity, water body’s approachability, vegetation growth naturalness, landform naturalness, and building and furniture mass fitness had greater effects on the park green space landscape in Daqing City, which should be paid much attention in the landscape ecological construction, renovation, and management of the park green spaces in the future. Among the ten urban park green spaces, Oil Field Paradise and Urban Forest Park had the best eco-aesthetics effect, whereas Chengfeng Square and Century Avenue (high-tech development zone)- attached banding green space had the worse one. The model could avoid some deficiencies in traditional methods, and also, provide new idea and method for the study of comprehensive assessment, sequence analysis, and optimization of landscape assessment with fuzzy and uncertain high-dimension data.