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Table of Content

    18 November 2010, Volume 21 Issue 11
    Articles
    Effects of simulated warming on soil enzyme activities in two subalpine coniferous forests in west Sichuan.
    2010, 21(11):  2727-2733. 
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    With open top chamber (OTC), this paper studied the effects of simulated warming on the activities of soil invertase, urease, catalase, polyphenol oxidase in two contrasting subalpine coniferous forests (a dragon spruce plantation and a natural conifer forest) in west Sichuan. The dynamic changes of soil temperature and soil moisture were monitored synchronously. In the whole growth season, simulated warming enhanced the daily mean temperature at soil depth 5 cm by 0.61 ℃ in the plantation, and by 0.55 ℃ in the natural forest. Conversely, the volumetric moisture at soil depth 10 cm was declined by 4.10% and 2.55%, respectively. Simulated warming also increased soil invertase, urease, catalase, and polyphenol oxidase activities. The interactive effect of warming and forest type was significant on soil urease and catalase, but not significant on soil invertase and polyphenol oxidase. The warming effect on soil catalase depended, to some extent, on season change. In all treatments, the soil enzyme activities in the natural forest were significantly higher than those in the plantation. The seasonal changes of test soil enzyme activities were highly correlated with soil temperature, but less correlated with soil moisture. This study indicated that warming could enhance soil enzyme activities, and the effect had definite correlations with forest type, enzyme category, and season change. The soil enzyme activities in the subalpine coniferous forests were mainly controlled by soil temperature rather than soil moisture.
    Effects of fertilization level on diurnal variation of gas exchange of young Eucalyptus grandis leaf.
    2010, 21(11):  2734-2741. 
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    Different levels (0, 90, 180, and 270 g per tree) of compound fertilizer containing 15% N, 15%P2O5, and 15%K2Owere applied to young Eucalyptus grandis to study the diurnal variations of its leaf stomatal conductance (Gs), intercellular CO2 concentration (Ci), net photosynthesis rate (Pn), transpiration rate (Tr), water use efficiency (WUE), and vapor pressure deficiton leaf surface (Vpdl) as well as the variation of leaf chlorophyll content, aimed to approach the relationships of E. grandis photosynthesis with fertilization and environmental factors. In all treatments, the diurnal variation of Pn presented a single-peak curve, with the peak at 14:00 and not showing midday depression. TheGs,Tr, and Vpdlshowed the similar trend with Pn, while theCihad a minimum value at 14:00. The WUE demonstrated a double-peak curve, with the first and second peak occurred at 10:00 and 14:00, respectively. Comparing with the control, the mean values of Gs,Pn,Tr,WUE, and chlorophyll a, chlorophyll b, and total chlorophyll contents under fertilization increased by 4.6%-15.9%, 7.8%-21.8%, 4.8%-11.6%, 3.2%-8.8%, 15.5%-62.0%, 14.5%-44.5% and 15.3%-57.1%, respectively, and the increment increased with fertilization level. By contrast, the mean values of Ci and Vpdl decreased by 14.5%-44.5% and 15.3%-57.1%, respectively, and the decrement increased with fertilization level. The Gs, Pn, and Tr were significantly correlated with air temperature, relative humidity (RH), and photosynthetic active radiation (PAR), and also, the Gs was significantly correlated with Pn and Tr. It was suggested that fertilization could promote E. grandis growth and enhance its WUE and biological carbon sequestration, and air temperature, RH, PAR, and Gs were the main factors causing the diurnal variations of photosynthesis and transpiration of E. grandis.
    Time lag effect between poplar’s sap flow velocity and microclimate factors in agroforestry system in west Liaoning Province.
    2010, 21(11):  2742-2748. 
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    By using Granier’s thermal dissipation probe, the sap flow velocity of the poplars in agroforestry system in west Liaoning was continuously measured, and the microclimate factors were measured synchronously. Dislocation contrast method was applied to analyze the sap flow velocity and corresponding air temperature,air humidity, net radiation, and vapor pressure deficit to discuss the time lag effect between poplar’s sap flow velocity and microclimate factors on sunny days. It was found that the poplar’s sap flow velocity advanced of air temperature, air humidity, and vapor pressure deficit, and lagged behind net radiation. The sap flow velocity in June, July, August, and September was advanced of 70, 30, 50, and 90 min to air temperature, of 80, 30, 40, and 90 min to air humidity, and of 90, 50, 70, and 120 min to vapor pressure deficit, but lagged behind 10, 10, 40, and 40 min to net radiation, respectively. The time lag time of net radiation was shorter than that of air temperature, air humidity, and vapor pressure. The regression analysis showed that in the cases the time lag effect was contained and not, the determination coefficients between comprehensive microclimate factor and poplar’s sap flow velocity were 0.903 and 0.855, respectively, indicating that when the time lag effect was contained, the determination coefficient was ascended by 2.04%, and thus, the simulation accuracy of poplar’s sap flow velocity was improved.
    Relationships between reactive oxygen metabolism and endodormancy release of peach bud under short-term heating.
    2010, 21(11):  2749-2754. 
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    Taking the 6-year old peach “Shuguang” as test object, this paper studied the effects of shortterm heating at 40 ℃, 45 ℃, and 50 ℃ on the bud livability, bud burst, reactive oxygen content, and activities of related enzymes in peach bud, aimed to investigate the regulation effect of short-term heating on the endodormancy release of peach bud. The results indicated that the effects of short-tern heating on the endodormancy release of peach bud were advanced by the postponement of treatment date, the increase of treatment temperature, and the prolonging of treatment time. On November 30, the regulation effect of heating at 40 ℃ was negative. Comparing with those under no-heating (CK), the date of endodormancy release was postponed, the bud burst, the O2and ·OH production rates, the H2O2 content, and the activities of CAT and POD were lowered, and the SOD activity was improved. It was adverse under heating at 45 ℃ and 50 ℃. On December 10, heating at 40 ℃ nearly had no obvious effect on the endodormancy release, while heating at 45 ℃ and 50 ℃ had the same effect as that on November 30, with the former being more superior to the latter. Correlation analysis indicated that the rapid increase of reactive oxygen might be the critical reason for the endodormancy release of peach bud.
    Effects of sand-covering on apple trees transpiration and fruit quality in dry land orchards of Longdong, Gansu.
    2010, 21(11):  2755-2762. 
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    Aiming at the seasonal drought in the dry land orchards of Longdong, Gansu Province, a sand-covering experiment was conducted with 15-year-old  Nagafu No.2 apple trees, with the soil water content, temperature, stem sap flow velocity, leaf stomatal conductance, and fruit quality measured. In the orchard covered with 5-cm-thick riversand, the increment of soil temperature in February-April was lower than 1 ℃, while in June-July, it was 2.44  ℃ and 2.61  ℃ on sunny and cloudy days, respectively. The soil water content was over 60% of field capacity throughout the growing season. On sunny days with high soil water content  (H season), the stem sap flow curve presented a wide peak. Under sand covering, the sap flow started 0.6 h earlier, and the maximum sap flow velocity was 25.5% higher than the control.  On cloudy days of H season, the maximum sap flow velocity was 165.6% higher than the control. On sunny days with low soil water content   (L season), the sap flow curve had a single peak, and under sand covering, the sap flow started 0.5-1 h earlier than the control on sunny days. The maximum sap flow velocity was 794 g·h-1. On cloudy days of L season, the sap flow started 1 h earlier, and the maximum sap flow velocity was 311.0% higher than the control. The evaporation of the control was 156.0% higher than that of sand-covering from March to July, suggesting that excessive ground water evaporation was the main reason to cause soil drought. Under sand-covering, single fruit mass was improved obviously whereas fruit firmness was reduced slightly, and soluble solids, vitamin C, total sugar, and organic acid contents were somewhat promoted.
    Changes of root biomass, root surface area, and root length density in a Populus cathayana plantation.
    2010, 21(11):  2763-2768. 
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    By using soil core method, the biomass, surface area, and length density of roots ≤2 mm and 2-5 mm in diameter in a 50-year-old Populus cathayana plantation on the northern slope of Qinling Mountains were determined during growth season. Among the roots <5 mm in diameter, those ≤2 mm and 2-5 mm in diameter accounted for 77.8% and 22.2% of the total root biomass, respectively. The surface area and length density of the roots ≤2 mm in diameter accounted for more than 97% of the total, and those of the roots 2-5 mm in diameter only occupied less than 3%. The biomass, surface area, and root length density of roots ≤2 mm in diameter decreased with soil depth, while those of the roots 2-5 mm in diameter were the least in 20-30 cm soil layer. The biomass, surface area, and length density of roots ≤ 2 mm in diameter were significantly correlated with soil organic matter and available nitrogen, but no significant correlations were found for the roots 2-5 mm in diameter.
    Spatial patterns of and specific correlations between dominant tree species in a karst evergreen and deciduous broadleaved mixed forest in Mulun Karst National Nature Reserve.
    2010, 21(11):  2769-2776. 
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    In order to understand the biological characteristics and specific correlations of dominant tree species in a karst characteristic evergreen and deciduous broad-leaved mixed forest in Mulun National Nature Reserve of Guangxi, a point pattern analysis was made on the spatial distribution patterns and inter-and intraspecific correlations of four dominant species in a one-hectare plot. Among the four species, Boniodendron minius dominated in tree sublayer I, while Ligustrum japonicum, Sinosideroxylon wightianum, and Rapanea kwangsiensis  dominated in tree sublayers II and III. All the four species had a clumped distribution at scale <10 m, a transition from clumped to random distribution at scale 10-25 m, and a random or regular distribution at scale >25 m. The critical scale from clumped to random distribution varied with species. No significant correlations were observed between the B. minius in sublayerⅠand the dominant species in sublayer Ⅱ. The correlations of B. minius with the dominant species in sublayers Ⅱ and Ⅲ showed greater fluctuation, with significant positive correlation for L. japonicum at scale <50 m, no significant correlation for S. wightianum, and no significant correlation for R. kwangsiensis at scale <20 m but significant negative correlation at scale 20-50 m.
    Physical properties of paddy soils with different productivity in double-rice cropping region of Hunan Province.
    2010, 21(11):  2777-2784. 
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    A total of 24 paddy soil samples with different productivity were collected from eight main rice production counties in east, central, and northwest Hunan Province, with the parameters of soil physical properties and clay mineral composition, including bulk density, particle density, porosity, field water-holding capacity, water-stable aggregates, mean weight diameter, normalized mean weight diameter, aggregate destruction rate, organic carbon, organic cementing materials, inorganic cementing materials, and clay minerals determined. The results showed that highly productive (>14000 kg·hm-2) paddy soil possessed bulk density below 1.2 g·cm3, soil particle density about 2.0 g·cm3, and 5-0.5 mm water-stable macroaggregates about 20%. Most of the test parameters had no significant differences between highly productive and medium productive (10000-13500 kg·hm-2) paddy soils, but significant differences between highly productive and lowly productive (<10000 kg·hm-2) paddy soils, suggesting that under good management, medium productive paddy soils could be upgraded to highly productive paddy soils. At present, the physical properties of lowly productive paddy soils were poor, which need to be improved to raise productivity.
    Effects of rhizosphere soil permeability on water and nutrient uptake by maize.
    2010, 21(11):  2785-2791. 
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    Aimed to better understand the significance of soil microenvironment in crop growth, a pot experiment was conducted to investigate the effects of rhizosphere soil permeability on the water and nutrient uptake by maize. Under three irrigation levels (600, 400, and 200 ml per pot), three treatments of soil aeration (no tube aeration as the control, tube aeration every two days, and tube aeration every four days) were installed, and the physiological indices of maize were measured. Under the same irrigation levels, soil aeration increased the plant height, leaf area, chlorophyll contents, promoted nutrient adsorption and increased root vitality markedly. At elongation stage, treatment tube aeration every four days had the highest root vitality (8.24 mg·g-1·h-1) under the irrigation level 600 ml per pot, being significantly higher (66.7%) than that (4.94 mg·g-1·h-1) of the control. Soil aeration had no significant effects on the transpiration rate of maize, indicating that rhizosphere soil aeration could raise water and nutrient use efficiency, and improve maize growth.
    Effects of long-term fertilization on microbial biomass carbon and nitrogen and on carbon source utilization of microbes in a red soil.
    2010, 21(11):  2792-2798. 
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    In order to explore the effects of long-term fertilization on the microbiological characters of red soil, soil samples were collected from a 19-year long-term experimental field in Qiyang of Hunan, with their microbial biomass carbon (MBC) and nitrogen (MBN) and microbial utilization ratioof carbon sources analyzed. The results showed that after 19-year fertilization, the soil MBC and MBN under the application of organic manure and of organic manure plus inorganic fertilizers were 231 and 81 mg·kg-1soil, and 148 and 73 mg·kg-1 soil, respectively, being significantly higher than those under non-fertilization, inorganic fertilization, and inorganic fertilization plus straw incorporation. The ratio of soil MBN to total N under the application of organic manure and of organic manure plus inorganic fertilizers was averagely 6.0%, significantly higher than that under non-fertilization and inorganic fertilization. Biolog-ECO analysis showed that the average well color development (AWCD) value was in the order of applying organic manure plus inorganic fertilizers≈applyingorganic manure > non-fertilization > inorganic fertilization ≈ inorganic fertilization plus straw incorporation. Under the application of organic manure or of organic manure plus inorganic fertilizers, the microbial utilization rate of carbon sources, including carbohydrates, carboxylic acids, aminoacids, polymers, phenols, and amines increased; while under inorganic fertilization plus straw incorporation, the utilization rate of polymers was the highest, and that of carbohydrates was the lowest. Our results suggested that long-term application of organic manure could increase the red soil MBC, MBN, and microbial utilization rate of carbon sources, improve soil fertility, and maintain a better crop productivity.
    Effects of irrigation amount on water use characteristics and grain yield of wheat under different nitrogen application rates.
    2010, 21(11):  2799-2805. 
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    A field experiment was conducted to examine the effects of irrigation amount on the water consumption, flag leaf physiological characteristics, and grain yield of wheat under the nitrogen application rates 180 kg·hm-2 (N180) and 240 kg·hm-2 (N240 ). Four irrigation regimes were designed, i.e., no irrigation during whole growth period (W0), irrigation with 60 mm water before sowing (W1), irrigation with 60 mm water before sowing and at jointing stage, respectively (W2), and irrigation with 60 mm water before sowing, at jointing stage, and at flowering stage, respectively(W 3). In treatment W0, the water consumption amount below 100 cm soil layer was lower than that in other treatments; and in treatments W1and W2 , the water consumption amount in 100-200 cm and 0-200 cm soil layers was higher than that in treatment W3. The soil water consumption amount in 0-80 cm soil layer, the consumption percentage from flowering to maturing stage, and the total water consumption amount were all higher under  N240 than under N180. At mid and late grain-filling stages, the relative water content (RWC) and water potential (ψw) of flag leaves were higher in treatments W2and 3than in treatments W0and W1. The RWC and ψw at late grainfilling stage were higher in treatments N240W0 and N240 W1 than in N180W0 and N180W1, respectively, but had no significant differences between treatments N240W2 and N180W2, and N240W3 and N180W3. In this study, treatment N180W2 had the higher grain yield, water use efficiency (WUE), and nitrogen use efficiency, while over-irrigation increased the  water consumption amount, and decreased theWUE, irrigation water use efficiency, and irrigation benefit.
    Effects of irrigation amount on leaf structure, photosynthetic physiology, and fruit yield of Lycium barbarum in arid area.
    2010, 21(11):  2806-2813. 
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    Lycium barbarum is an important traditional medicinal plant in China. Under controlled condition, a field experiment was conducted to study the effects of different monthly irrigation quota on the leaf structure, photosynthetic physiology, and fruit yield of L. barbarum, aimed to determine an appropriate irrigation amount for the plant. When the monthly irrigation quota was less than 900 m3·hm-2, the leaf area, leaf thickness, palisade tissue thickness, cell tense ratio (CTR), net photosynthetic rate (Pn), intrinsic water use efficiency (WUE), stomatal limitation value (Ls), and fruit yield of L. barbarum all increased significantly with monthly irrigation quota, while leaf stoma density and intercellular CO2 concentration (Ci) showed a reverse trend. When the irrigation quota was more than 900 m3·hm-2, the Ci increased with irrigation quota, the leaf area, stoma density, and fruit yield had no obvious change, whereas the other indices showed a reverse trend. The leaf transpiration rate and Gs were the highest at irrigation quota 450 m3·hm-2, being 8.02 and 324 mmol·m-2·s-1, respectively; whereas at other irrigation quota, these two indices were lower than the control. In terms of saving water, the monthly irrigation quota 900 m3·hm-2was more appropriate for Lycium barbarum.
    Regulation effect of water and nitrogen on cotton biomass and yield under different drip irrigation patterns.
    2010, 21(11):  2814-2820. 
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    Three levels (low, medium, and high) of irrigation amount and nitrogen application rate were installed in a field experiment to study the regulation effect of water and nitrogen on the cotton biomass and yield under different drip irrigation patterns. Under the irrigation patterns 1 lateral 4 rows, 2 laterals 4 rows, and 2 laterals 6 rows, when the irrigation amount increased from low (90, 140, and 140 mm) to medium level (150, 200, and 200 mm), the aboveground dry biomass was increased by 9.2%, 37.9%, and 23.5%, and the seed yield was increased by 19.1%, 14.1%, and 16.0%, respectively. When the irrigation amount increased from medium to high level (210, 260, and 260 mm), the aboveground dry biomass was increased by 15.8%, 19.1%, and 16.7%, and the seed yield was increased by 7.7%, 11.2%, and 9.5%, respectively. When the nitrogen application rate changed from low (67.6 kg·hm-2) to medium level (95.2 kg·hm-2), the aboveground dry biomass under irrigation pattern 2 laterals 4 rows was increased by 14.3%, the seed yield under irrigation pattern 1 lateral 4 rows was increased by 22.2%, while these two parameters under other irrigation patterns had no significant change. When the nitrogen application rate changed from medium to high level (122.8 kg·hm-2), the seed yield under the irrigation patterns 1 lateral 4 rows, 2 laterals 4 rows, and 2 laterals 6 rows was increased by 7.4%, 13.9%, and 9.9%, respectively, but the aboveground dry biomass had no significant change. Comparing with that under the irrigation patterns 1 lateral 4 rows and 2 laterals 6 rows, the regulation effect of water and nitrogen on the aboveground dry biomass and seed yield under irrigation pattern 2 laterals 4 rows was more apparent. As for the same water and nitrogen treatments, the aboveground dry biomass and seed yield were higher under the irrigation pattern 2 laterals 4 rows, suggesting that this drip irrigation pattern was most appropriate to the water and nitrogen management of cotton field.
    Variation analysis on the grain yield and main agronomic traits of spring wheat in rainfed regions of China.
    2010, 21(11):  2821-2829. 
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    Based on the grain yield data of spring wheat from the 2002-2005 regional trials with 13 cultivars (lines) on the rainfed farmlands at 18 locations of China, and by using variance analysis and GGE (genotype main effect plus genotype-by-environment interaction) biplot, this paper studied the effects of genotype, environment, and genotype × environment interaction (GEI) on the yield variation of spring wheat and the yield stability of different cultivars (lines). Comparing with genotype and GEI, the environment had much more contribution on the yield variation, accounting for 87.5%-92.0% of the total. In the GEI items, genotype × location had the greatest effect, whereas genotype × year had the smallest one. The average yield of modern spring wheat genotypes across years and locations in China was 2550 kg·hm-2. Among the three yield components, thousand kernel weight (TKW) had the least variation under environmental change. The main environment factors affecting the yield variation were annual accumulated temperature (≥10 ℃), precipitation in growth season, mean air temperature, altitude, annual precipitation, and frost-free period. The grain yield had significant positive correlations with spike number per unit area (SPU) (r=0.675**), TKW (r=0.456**, and kernels per spike (KPS) (r=0.581**), and the SPU, KPS and TKW also had positive correlations (r=0.244-0.480**) with each other, implying that these three yield components might be increased or improved synchronously.
    Effects of exogenous Ca2+ on |morphological and photosynthetic characteristics and chlorophyll fluorescent parameters of squash seedlings under high temperature and strong light stress.
    2010, 21(11):  2830-2835. 
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    Taking squash (Cucurbita pepo L.) variety Alan as test object, this paper studied the effects of exogenous Ca2+ on the morphological and photosynthetic characteristics and chlorophyll fluorescent parameters of squash seedlings under the cross-stress of high temperature and strong light. Under the stress, applying 5-20 mmol·L-1 of Ca2+ increased the plant height, leaf area, chlorophyll and carotenoid contents, photosynthetic rate (Pn), stoma conductance (Gs), transpiration rate(Tr), maximal PSⅡ efficiency (Fv/Fm), actual PSⅡ efficiency (ΦPSⅡ), and photochemical queching coefficient (qP), and decreased the intercellular CO2 concentration (Ci) and non-photochemical fluorescence quenching coefficient (NPQ), suggesting that this application of exogenous Ca2+could effectively mitigate the damage of high temperature and strong light stress on the squash seedlings leaf, and make it keep more rapid photosynthetic electron transfer rate and higher PSⅡ electron transfer activity. Among the treatments of applying Ca2+, 10 mmol Ca2+·L-1had the best effect. When the Ca2+application rate exceeded 40 mmol·L-1, no mitigation effect was observed on the high temperature and strong light stress.
    Protective effects of La(NO3)3 on ryegrass seedlings photosynthetic apparatus under NaHCO3 stress.
    2010, 21(11):  2836-2842. 
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    This paper studied the effects of foliar spraying different concentration La(NO3)3 on the photosynthesis, chlorophyll fluorescence parameters, Mehler reaction, and xanthophyll cycle of ryegrass seedlings under the stress of 150 mmol NaHCO3·L-1. Foliar spraying low concentration (0.05 mmol·L-1) La(NO3)3 could significantly decrease the decrement of net photosynthesis rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and stomatal limited value (Ls) and the increment of intercellular CO2 concentration (Ci) under NaHCO3 stress, efficiently alleviate the inhibitory effects of NaHCO3 stress on PSⅡ photochemical quenching (qP), actual photochemical efficiency (ΦPSⅡ), photosynthetic carbon assimilation dependent electron transport rate (ETRp), and Mehler reaction- dependent electron transport rate (ETRm), enhance the activities of superoxide dismutase, peroxidase, and ascorbate peroxidase, the non-photochemical energy dissipation (NPQ), the xanthophyll cycle pool (V+A+Z), and the de-epoxidation extent of xanthophyll cycle(A+Z)/(V+A+Z),and thereby, alleviate the damage of photosynthetic apparatus caused by NaHCO3 stress. However, treating with
    high concentration (0.5 mmol·L-1) La(NO3)3 had no obvious alleviation effects. It was suggested that foliar spraying an appropriate concentration La(NO3)3 could not only alleviate the decrease of ryegrass seedling’s photosynthetic rate induced by non stomata factors and the inhibition of photochemical efficiency, but also accelerate the Mehler reaction under NaHCO3 stress. With the accelerated Mehler reaction, excessive excitation energy could directly be consumed, and the xanthophyll cycle- dependent thermal dissipation could be promoted to efficiently protect the photosynthetic apparatus against photo-damage under NaHCO3 stress. Also, the active oxygen produced by the accelerated Mehler reaction could be scavenged by the enhanced anti-oxidative enzyme activities.
    Effects of continuous cropping on bacterial community diversity in rhizosphere soil of Rehmannia glutinosa.
    2010, 21(11):  2843-2848. 
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    In this paper, T-RFLP (terminal restriction fragment length polymorphism) technique was adopted to study the dynamic changes of bacterial community in the rhizosphere soil of continuously cropped Rehmannia glutinosa L. The results showed that the Shannon diversity index, Margalefindex, and similarity index of bacterial community in the rhizosphere soil all decreased in the order of control > one-year cropping > two-year continuous cropping. Under continuous cropping, the proportion of dominant bacterial species declined obviously. In one-year cropping soil, the class Bacilli of phylum Firmicute dominated the bacteria community; while in two-year continuous croppingsoil, the class Epsilonproteobacteria of phylum Proteobacteria became dominant. Continuous cropping of R. glutinosa decreased the bacteria species, and simplified the bacterial community structure. The changes of bacterial community diversity under continuous cropping of R. glutinosa led to the disorder of the functions of bacterial community, and thereby, the destruction of the ecological balance in rhizosphere soil, which might be one of reasons causing the obstacles of continuous cropping of R. glutinosa.
    Community structure and diversity of soil arthropods in naturally restored sandy grasslands after grazing.
    2010, 21(11):  2849-2855. 
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    Taking the Naiman Desertification Research Station under Chinese Academy of Sciences as a base, an investigation was conducted on the community structure of soil arthropods in the naturally restored sandy grasslands after different intensity grazing disturbance, with the effects of vegetation and soil on this community structure approached. In the non-grazing grassland, soil arthropods were rich in species and more in individuals, and had the highest diversity. In the restored grassland after light grazing, soil arthropods had the lowest evenness and diversity. In the restored grassland after moderate grazing, the individuals of soil arthropods were lesser but the major groups were more, and the evenness and diversity were higher. In the restored grassland after heavy-grazing, the individuals of soil arthropods were more but the major groups were lesser, and the diversity was higher. Plant individuals’ number, vegetation height and coverage, and soil alkalinity were the main factors affecting the soil arthropod community in naturally restored grasslands after different intensity grazing disturbance. It was implied that after 12-year exclosure of grassland, soil arthropod community could be recovered to some degree, while grazing disturbance had long-term negative effects on the arthropod community.
    Population division of Larimichthys polyactis in China Sea.
    2010, 21(11):  2856-2864. 
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    Previous approaches prevalently believed that there were three populations of Larimichthy spolyactis existed in China Sea. To clarify the number of the populations, an improved approach was adopted in this paper, based on the suite of methodologies including geographical isolation, population dynamics, morphology, anatomy, and molecular genetics. In our finding, there were two instead of three L. polyactis populations in the China Sea, one in Northern Yellow Sea and Bohai Sea, and the other in Southern Yellow Sea and East China Sea. Three evidences were against traditional approaches. Firstly, the traditional division was not supported by morphology, anatomy, and molecular genetics evidences. Secondly, in accordance with our study by referring the 1971-1982 fishing yield statistics from 14 major fishery companies in China, the geographical isolation for L. polyactis between Southern Yellow Sea group and East China Sea group was insignificant. In fact, the two L. polyactis groups inhabited at the same overwintering ground in offshore during winter, and the spawning fishes migrated towards to the nearshore of Zhoushan, Yushan, and Lüsi fishing grounds in the following spring. At the same time, another L. polyactis group originally inhabited at the southern nearshore of mid East China Sea during winter migrated northwards and amalgamated with the fishes in the waters of Zhoushan. After spawning, these fishes aggregated into a large feeding group outside the prohibited fishing zone line from May to August. In contrast, the population from the northern Yellow Sea and Bohai Sea had significant geographic isolation with the population from the southern Yellow Sea and East China Sea. Last but not least, no evidences could support that there were two populations existed at Southern Yellow Sea and the East China Sea, because the productivity of these two areas increased synchronously in recent years while the resource density at northern Yellow Sea and Bohai Sea was still much lower.
    Effects of substrate nitrogen and phosphorus contents on Potamogeton crispus growth and reproduction.
    2010, 21(11):  2865-2870. 
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    Six nutritional levels were designed to study the effects of different nitrogen (N) and phosphorus (P) contents in sediment on the growth and reproduction of Potamogeton crispus. The results revealed that the germination rate of P. crispus was not affected by the N and P contents in sediment, and all reached 100%. With the increasing N and P contents in sediment, the N content in plant tissues increased first and approached to a stationary level then, while the P content presented a slow increasing trend. In the meantime, the initial fluorescence (Fo) declined rapidly, while the potential maximum quantum yield (Fv/Fm) increased first followed by a slight decrease, indicating that the photosynthetic efficiency was enhanced by the increasing N and P contents in sediment but decreased at excessively high N and P contents. The rapid light curves showed that P. crispus could effectively use weak light and was more susceptible to photoinhibition under intense light, but its resistance capability against intense light could be improved by the high N and P contentsin sediment. The high N and P contents in sediment could also promote the total biomass of P. crispus, but reduce the root:shoot ratio of the plant. Under the increasing N and P contents in sediment, the asexual reproduction of P. crispus was improved, reproductive strategy was optimized, and also, the sexual reproduction occurred but the seed setting rate was low, only 19.6% on average.
    Changes of reproduction habitat quality of red-crowned crane in Zhalong wetlands.
    2010, 21(11):  2871-2875. 
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    Based on the maps of habitat factors in Zhalong wetlands in 1996 and 2004, two models called habitat suitability index model and nearest neighbor analysis model were established to quantitatively analyze the changes of reproduction habitat quality of red-crowned crane in Zhalong wetlands. The results showed that in 1996-2004, the suitable reproduction habitats of red-crowned crane in the wetlands experienced both area loss and functional loss. By the end of  2004, the suitable habitats in the study area lost greatly, and those in core area undergone serious fragmentation. Consequently, the habitatselection behaviors of red-crowned crane responded in two ways: one was the centralization of nests towards core area, and the other was the spatial distribution pattern changed from uniform to aggregative.
    Remote sensing based monitoring of vegetation dynamics and ecological restoration in Beijing mountainous area.
    2010, 21(11):  2876-2882. 
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    By using the Landsat images in 1979, 1988, 1999, 2005, and 2009, and the linear unmixed model at pixel scale, this paper analyzed the spatiotemporal variation of vegetation coverage in Beijing mountainous area. After detecting the areas of vegetation degradation or restoration, the impacts of elevation, slope, and soil type on vegetation restoration were studied. From 1979 to 1988, the vegetation coverage in the study area had no obvious change, but in the following 12 years, the vegetation coverage was seriously destroyed due to the fast development of social economy. Fortunately, many protective measures were taken since 2000, which improved the vegetation coverage to 72% in 2009, with an increment of 13% compared to the vegetation coverage in 1999. A significant correlation was observed between the variations of vegetation coverage and territorial features. The areas with poor soil or large slope were more easily suffered from degradation than other places, and the flat regions with low elevation were more affected by human activities.
    LAI-based regional winter wheat yield estimation by remote sensing.
    2010, 21(11):  2883-2888. 
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    By using retrieved LAI from remotely-sensed imagery, this paper studied the regional winter wheat yield estimation in Huanghuaihai Plain of North China. In order to improve the quality of remotely sensed data for winter wheat yield estimation, a Savitzky-Golay filter was used to smooth the MODIS-NDVI time series data to reduce the cloud contamination and remove the abnormal data. Then, a Gaussian model was used to simulate the daily crop LAI which was corrected by interpolating the measured LAI to get the average LAI values for each phenological stage. Using these LAI data, the relationships between LAI and crop yield at the main phenological stages of winter wheat was established. After optimizing the yield estimation model, the optimal time period and the best model parameters for winter wheat yield estimation in the study area were selected out. Finally, the established model was applied to estimate winter wheat yield based on the retrieved LAI from MODIS-NDVI, and the model accuracy was tested. Through the comparison of the predicted yield with the measured yield in the field, the mean relative error was 1.21%, and the RMSE was 257.33 kg·hm-2. The model and the method proposed in this study were promising, and could help to get the accurate estimated yield of winter wheat in about 20-30 days ahead of the harvest.
    Landscape ecological security assessment of Beijing City based on RS and GIS.
    2010, 21(11):  2889-2895. 
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    By using RS, GIS, and landscape ecology methods, and based on the landscape structure, function, vitality, ecological sensitivity, and landscape pressure, an evaluation index system of landscape ecological security was constructed to analyze the landscape ecological security level and its spatiotemporal distribution pattern in Beijing City in 1988-2004. During the study period, the ecological service value of Beijing City was on a relatively high level, while the landscape vigor index and landscape pressure were on a relatively low level. The stability of landscape structure dropped, and the ecological sensitivity was also on a relatively low level. In 1998 and 2004, the landscape ecological security index of Beijing City was on a medium level, with the average value being 0.410 and 0.403, respectively, suggesting a slight deterioration in the landscape ecological security during the study period.
    Change characteristics and their causes of fractional vegetation coverage (FVC) in Shaanxi Province.
    2010, 21(11):  2896-2903. 
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    Based on the sub-pixel analysis model, and by using 2000-2009 MODIS NDVI (250 m resolution), this paper quantitatively analyzed the spatiotemporal change characteristics and their causes of fractional vegetation coverage (FVC) in Shannxi Province. From 2000 to 2009, the FVC in the Province had a significant increasing trend, with the great magnitude of 35.0%. During that period, the vegetation coverage increased from 56.9% in 2000 to 68.9% in 2009 in the provincial scale, and the increment was much higher in northern Shannxi, being 21.6% in Yulin and 22.0% in Yan’an. Though the vegetation coverage had an overall increase, it was locally degraded in some areas. The areas with improved vegetation coverage at the significance levels of  <0.01, and <0.05 were 37.8% and 11.9%, while those with non-improved and degraded vegetation coverage were 46.1% and 4.2%, respectively. The areas whose vegetation coverage had a change rate of 200%, 200%-100%, 100%-10%, 10%-10%, and < -10% occupied12.2%, 13.3%, 38.8%, 29.3%, and 6.4% of the total, respectively. During the study period, the structure of vegetation coverage in the Province also improved. The areas with high and normal vegetation density increased significantly by 10% and 8.4%, respectively, while the area with low vegetation density decreased significantly by 18.4%. The improvement of the FVC in Shaanxi Province was the interactive effect of natural factors and human activities, but the main cause was the implementation of a series of ecological construction projects such as closing hill for forestation and restoring farmland into forestland and grassland.
    Changes of wetland landscape pattern in Eastern Yellow River Delta Nature Reserve from 1995 to 1999.
    2010, 21(11):  2904-2911. 
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    Based on the 1995-1999 Landsat TM images and geographic information systems, this paper analyzed the change characteristics of wetland landscape pattern in the Eastern Yellow River Delta Nature Reserve (an inlet of current flow path emptying into the sea), and related driving factors during the past few years pre and post the Yellow River diverting into Qing 8 anabranches in 1996. In 1995-1999, natural wetland was still the matrix of the wetlands in the Reserve, while constructed wetland only had a very small proportion. A substantial increase was observed in the area of nonwetlands, and a decline was found in the area of natural and constructed wetlands, among which, bare muddy tidal flats and marshes shrank significantly. Though the landscape types in the reserve had no homogeneity in the changes of shape and structure, and their aggregation degree in spatial distribution varied, the overall landscape structure became more complicated and fragmented, and the distribution of inner landscape types converted from continuously large blocks to discretely small patches. River diversion, flow break, and human activities were the main three driving factors leading to the changes of the wetland landscape pattern in the reserve.
    Spatiotemporal change characteristics of agricultural climate resources in middle and lower reaches of Yangtze River.
    2010, 21(11):  2912-2921. 
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    The  period 1961-2007 was divided into two by the time node of year 1981, and the change characteristics of the agricultural climate resources both in periodⅠ(1961-1980) and in period Ⅱ (1981-2007) were analyzed and compared. The results showed that under the background of global warming, the average climatic trend rate of ≥10 ℃ accumulated temperature in the middle and lower reaches of Yangtze River in temperaturedefined growth season during 1961-2007 was 74 ℃·d·10 a-1, and the ≥10 ℃ accumulated temperature in period Ⅱ was 124 ℃·d higher than that in period I. Comparing with that in period I, the safe planting boundary of double cropping rice in period Ⅱ moved 0.79° northward. In 1961-2007, the precipitation in temperature-defined growth season had an overall increasing trend. Comparing with those in period I, the precipitation and the area of ≥767 mm precipitation (water requirement for normal growth of double cropping rice) in period II were increased by 1.6% and 1.13×10.4 km2, respectively. The average sunshine hour in temperature-defined growth season in period II was reduced by 8.1%, comparing with that in period I. In recent 47 years, about 91.1% stations in the reaches showed a decreasing trend in sunshine hours. Comparing with that in period I, the reference crop evapotranspirati
    on in temperature-defined growth season in period Ⅱ showed a slightly decreasing trend, and its low value region expanded while its high value region narrowed. The beginning date of daily temperature over 10 ℃ was averagely 2 days earlier in period Ⅱ than that in period I, while the ending date was in reverse. The ending date of daily temperature over 22 ℃ was almost the same in periods I and Ⅱ.
    Change trends of China agricultural thermal resources under climate change and related adaptation countermeasures.
    2010, 21(11):  2922-2930. 
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    Based on the 2011-2050 A2 climate scenario derived from the regional climate model PRECIS and the daily data of 1961-1990 baseline climate condition, this paper analyzed the possible changes of the agricultural thermal resources in China from 2011 to 2050. Comparing with the baseline climate condition in 1961-1990, the average frost-free periods in most parts of China in 2011-2050 under A2 climate scenario would have an obvious extension, mainly manifested in the advance of last frost date and the postpone of first frost date. The days with the daily averagetemperature stably passing 0 ℃ would also prolong significantly, and extend from 1 day to 14 days in most parts of the country. Especially from 2041 to 2050, the days with the daily average temperature stably passing 0 ℃ in most regions of Qinghai-Tibet Plateau, middle and lower reaches of Yangtze River, and western and southwestern regions of Gansu and Xinjiang could be extended by 49 days. The ≥0 ℃ accumulated temperatures in most parts of the country would have  increasing trends. In order to meet the future change trend of our agricultural thermal resources and to realize the sustainable development of agriculture in China, some countermeasures should be formulated, e.g, further adjusting agricultural cropping system, optimizing agricultural production distribution, developing biotechnology, and so on.
    Effects of climate warming and drying on millet yield in Gansu Province and related countermeasures. 
    2010, 21(11):  2931-2937. 
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    Based on the data of air temperature, precipitation, and millet yield from Ganzhou, Anding, and Xifeng, the representative stations in Hexi moderate arid oasis irrigation area, moderate sub-arid dry area in middle Gansu, and moderate sub-humid dry area in eastern Gansu, respectively, this paper calculated the regional active accumulated temperature of ≥0 ℃, ≥5 ℃, ≥10 ℃, ≥15 ℃, and ≥20 ℃ in millet growth period, and the average temperature and precipitation in millet key growth stages. The millet climatic yield was isolated by orthogonal polynomial, and the change characteristics of climate and millet climatic yield as well as the effects of climate change on millet yield were analyzed by statistical methods of linear tendency, cumulative anomaly, and Mann-Kendall. The results showed that warming and drying were the main regional features in the modern climatic change of Gansu. The regional temperature had a significant upward trend since the early 1990s, while the precipitation was significantly reduced from the late 1980s. There were significant correlations between millet yield and climatic factors. The millet yield in dry areas increasedwith the increasing temperature and precipitation in millet key growth stages, and that in Hexi Corridor area increased with increasing temperature. Warming and drying affected millet yield prominently. The weather fluctuation index of regional millet yield in Xifeng, Anding, and Ganzhou accounted for 73%, 72%, and 54% of real output coefficient variation, respectively, and the percentagesincreased significantly after warming. Warming was conducive to the increase of millet production, and the annual increment of millet climatic yield in Xifeng, Anding, and Ganzhou after warming was 30.6, 43.1, and 121.1 kg·hm-2, respectively. Aiming at the warming and drying trend in Gansu Province in the future, the millet planting area in the Province should be further expanded, and the millet planting structure should be adjusted. At the same time, according to the different regional and yearly climatic types, different varieties should be selected, and various planting measures should be taken.
    Environmental benefit-loss analysis of agro-ecosystem in Haihe River basin, China.
    2010, 21(11):  2938-2945. 
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    According to the connotation of ecosystem services, an evaluation index system for the agro-ecosystem services in the Haihe River basin of China was established, and the economic value  of the agro-ecosystem services and environmental costs were evaluated by the methods of market valuation, shadow price, and opportunity cost. In 2005, the total environmental benefit value of the agro-ecosystem services in the basin was 180.264 billion RMB, with the regulation value of 79.416 billion RMB (44.06%) and the supporting value of 100.848 billion RMB (55.94%). Provision and cultural services were not considered in this research. From the viewpoint of functional type, the ecosystem services value from high to low was in the order of oxygen release > water conservation > nutrient cycling > soil conservation > waste purification > environmental purification > carbon sequestration > straw returning. The environmental costs of the agro-ecosystem  were quite high (42.293 billion RMB), among which, fertilizer loss was 427.42×104 t, equivalent to 15.191 billion RMB, and greenhouse gases production was calculated as 3599.65×104 t CO2, equivalent to 27.102 billion RMB.
    Soil arsenic content and its health risk assessment for agricultural products in the region surrounding Shimen arsenic sulphide mine.
    2010, 21(11):  2946-2951. 
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    A systematic investigation was carried out on the arsenic content in the soils and plants surrounding Shimen arsenic sulphide mine. The arsenic content in top soils (0-20 cm) was averagely 99.51 mg·kg-1, being 5.34 times higher than that of the background value in Hunan Province and 8.70 times higher than that of local farmland soil. The topsoil arsenic content in paddy field and dry land was 43.51 and 115.1 mg·kg-1, respectively, being 0.45 and 1.87 times higher than that of the grade II level (paddy field 30 mg·kg-1; dry land 40 mg·kg-1) commended by the National Soil Quality (GB 15618-1995), and the corresponding arsenic exceeding rate was 62.5% and 50.0%, respectively. The arsenic content in edible parts of foodstuff, vegetables, and fruits was 0.16, 0.06, and 0.01 mg·kg-1, respectively, and the arsenic exceeding rate of crop samples compared to food security standard ranked in the order of foodstuff > vegetables > fruits. Rice and sweet potato were relatively seriously contaminated by arsenic. The highest arsenic content of rice was up to 0.84 mg·kg-1, which was 4.6 times higher than that of the National Standard, with the exceeding rate of 62.5%. Statistical analysis demonstrated that there was a positive correlation between the arsenic contents of soil and plant. The average daily intake of arsenic by local people through the consumption of the crops was 6.416 μg·kg-1·d-1, which was much higher than the standard commended by WHO, and the related health risk index was 21.39, which was 14.39 times higher than that in the control region.
    Effects of Sedum plumbizincicola-Oryza sativa rotation and phosphate amendment on Cd and Zn uptake by O. sativa.
    2010, 21(11):  2952-2958. 
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    In a pot experiment, hyperaccumulator Sedum plumbizincicola and low-cadmium accumulating Oryza sativa cultivar “Zhongxiang No. 1” were planted in rotation on a heavy metals-polluted soil, and calcium magnesium phosphate (Ca-P) and rock phosphate (P-R) were amended, aimed to study the effects of the rotation and phosphate amendment on the growth of the two plants and the zinc- and cadmium accumulation in their shoots. After the amendment of 50 g P-R·kg-1, the Zn and Cd uptake by S. plumbizincicola was 11.5 mg·pot-1 and 0·79 mg·pot-1, respectively, being significantly higher than that after the amendment of 4 g Ca-P·kg-1. After the planting of S. plumbizincicola, the Zn and Cd concentrations in “Zhongxiang No. 1” increased, but the amendment of Ca-P decreased the accumulation of Zn and Cd in rice shoot significantly. The rotation with S. plumbizincicola and the amendment of Ca-P and P-R could immobilize the Zn and Cd in the contaminated soil as indicated by the quantitative change of NH4OAc-extractable Cd and Zn, and the efficiency of amendment with Ca-P was better than that of amendment with P-R. Field trial showed that amendment with Ca-P could not only increase the rice yield, but also reduce the Zn and Cd accumulation in rice shoot to a certain extent.
    Effects of exogenous dissolved organic matter and temperature on copper forms in red soil.
    2010, 21(11):  2959-2964. 
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    A simulating incubation test was conducted to evaluate the effects of exogenous dissolved organic matter (DOM) and incubation temperature on the copper forms in red soil. Comparing with the control, adding different amount of DOM increased the content of soil exchangeable Cu, but decreased the content of soil Fe-Mn bound Cu. With increasing time of incubation, the content of soil exchangeable Cu in all DOM-added treatments had a decreasing trend. By the end of the incubation, treatment 250 mg DOM·L-1 had the highest contents of soil exchangeable Cu and carbonate bound Cu, while treatment 500 mg DOM·L-1 had the highest content of soil Fe-Mn bound Cu. In the treatments with DOM addition, the content of soil organic bound Cu increased by 10.67%-23.66%, compared with the control. At incubation temperature 25 ℃ and 45 ℃, the contents of soil exchangeable Cu and Fe-Mn bound Cu decreased with increasing time of incubation; while at 5 ℃, an opposite trend was observed. At these three temperatures, the content of soil carbonate bound Cu in treatments with DOM addition increased with incubation time. The content of soil organic bound Cu increased with increasing temperature, but that of soil residual Cu decreased at lower temperature (5 ℃).
    Quantitative characteristics and source analysis of heavy metals in paddy soils in downstream of the Second Songhua River, Jilin Province.
    2010, 21(11):  2965-2970. 
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    In autumn 2008, a total of 65 plough layer soil samples were collected from the paddy fields in Qianguo Irrigation Area located at the downstream of the Second Songhua River. These paddy fields were irrigated with  water from the River, and had different irrigation histories. The Cu, Pb, Zn, Cd, Ni, As, and Hg concentrations in the soil samples were determined, and the accumulation characteristics, input approaches, and pollution sources of these heavy metals were analyzed. The Cu, Pb, Zn, Cd, Ni, As, and Hg concentrations in the samples were 14.1- 28.4 mg·kg-1, 37.6-57.4 mg·kg-1, 53.3-84.4 mg·kg-1, 0.044-0.367 mg·kg-1, 18.4-37.0 mg·kg-1, 3.25-12.11 mg·kg-1, and 0.031-0.155 mg·kg-1, respectively. The Pb, Hg, and Cd exhibited an obvious accumulation trend, with their concentrations being 100.0%, 38.7%, and 66.1% higher than the baselines, respectively, while Cu, Zn, Ni, and As had less accumulation. With the increase of irrigation history, the Pb concentration showed a decreasing trend, while the Hg concentration was in reverse. There was no significant correlation between the Cd concentration and the irrigation history. According to source analysis, soil Pb  mainly originated from the atmospheric Pb deposition via historical use of leaded gasoline, soil Hg was  from the polluted irrigation water from the Second Songhua River, and soil Cd was from the use of chemical fertilizers, pesticides, and other agrochemicals. Though the Pb, Hg, and Cd had obviously accumulatied in the paddy fields in Qianguo Irrigation Area, their potential ecological risk was still low, and would not pose threat on the local agricultural production and food security.
    Optical methods for in situ measuring leaf area index of forest canopy: A review.
    2010, 21(11):  2971-2979. 
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    Leaf area index (LAI) is an important parameter of canopy structure, because it relates to many biophysical and physiological processes of canopy, including photosynthesis, respiration, transpiration, carbon cycling, precipitation interception, and energy exchange, etc. This paper introduced the theoretical bases and mathematical models of optical methods for forest canopy LAI determination, introduced the principles, merits, and drawbacks of currently used optical methods, and summed up the main sources of the errors in LAI optical measurement, including clumping effect, non-photosynthesis components, measurement conditions, and terrain effect. The developing status of quantitatively evaluating clumping effect, non-photosynthesis components, and terrain effect was analyzed, and the promising development directions of optical methods for measuring forest canopy LAI were discussed.
    Research advances in population dynamics of Orchidaceae.
    2010, 21(11):  2980-2985. 
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    In the study of population dynamics of Orchidaceae, demographic analysis can make us better understand the spatiotemporal variation of plant individuals, the core of the population dynamics study. Nevertheless, many orchid species have an epiphytic or lithophytic habit, which predisposes them to a discrete or patchy distribution. In this case, metapopulation study is a good method to judge the protective scale of the population by analyzing the extent of gene flow among patches. In addition, long-term observation is needed to obtain reliable information on the life history and population dynamics of Orchidaceae, and to understand the relationships between the spatiotemporal variation and functioning of orchid population in certain environmental conditions. As for the short-term study, it’s essential for a better understanding of the relationships between the structurally dependent plants and the communities in which they are fund. This paper reviewed the research advances in the population dynamics of Orchidaceae from the viewpoints of the population ecology and ecological characteristics of Orchidaceae.
    Application of nanoscale material in environmental remediation and its eco-environmental toxicity assessment: A review.
    2010, 21(11):  2986-2991. 
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    Though it has been claimed that nanotechnology has great potential in environmental cleaning, caution is required to the application of nano-particles (<100 nm). The studies relevant to organism exposure have shown that nano-particles can be hazardous. Currently, more papers are available about the remediation efficiency, characteristics, and mechanisms of manufactured nano-particles after applied into polluted environment, but  few studies are conducted about the ecotoxicological effects of the nano-particles. This paper reviewed the current researches on the hazards of nano- or ultrafine particles in environmental detoxification, discussed the potential environmental risks of applying nano-particles, and prospected the perspectives of the nanoparticles in environmental cleaning research.
    Effects of chlorimuron-ethyl on soil microbial community structure in soybean field.
    2010, 21(11):  2992-2996. 
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    By using phospholipid fatty acids (PLFA) method, this paper studied the soil microbial community structure in the soybean fields with different chlorimuron-ethyl application history in Weihe district of Heilongjiang Province. In the meantime, the residual amount of chlorimuron-ethyl in soil was determined. There was a very low residual of chlorimuron-ethyl in soil under the conditions of different chlorimuron-ethyl application history. With the increasing year of chlorimuron-ethyl application, the total concentration of soil microbial PLFA and the ratios of fungi/bacteria and Gram negative/Gram positive bacteria decreased, and the microbial stress level increased. Principal component analysis (PCA) showed that long-term application of chlorimuron-ethyl into soybean field changed the soil microbial community structure significantly.
    Influence of flooding on form transformation of soil arsenic.
    2010, 21(11):  2997-3000. 
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    An incubation test was conducted to study the dynamics of exogenously supplied dimethylarsenic acid (DMA), monomethylarsonic acid (MMA), and As(V) in soil under flooding. With the increasing time of incubation, the exogenously supplied DMA and MMA were mainly transformed into As(V), and the As(V) concentration increased, being significantly higher after incubated for 150 days, compared with that after incubated for 1 day. The exogenously supplied DMA was demethylated into As(V) within 30 days, accompanied by a little As(III), while the transformation rate of exogenously supplied MMA was rather slow within 60 days, accompanied by a little As(Ⅲ) and DMA. The exogenously supplied As(V) decreased with increasing time of incubation, and its form had less change except that a little As(Ⅲ) occurred.