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    18 November 2010, Volume 21 Issue 11
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    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 O2-·and ·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