Table of Content

15 May 2007, Volume 18 Issue 05

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Articles

Distribution patterns of woody plant diversity in stream riparian forests along an altitudinal gradient in Changbai Mountains.

MU Chang-cheng; NI Zhi-ying; LI Dong; SUN Xiao-xin; CHEN Jia-li

2007, 18(05):  943-950 . 

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By setting up sample transects and using α and β diversity indices,this paper studied the woody plant diversity and its responses to cutting in the stream riparian primeval and secondary forests along an altitudinal gradient in Changbai Mountains. The results showed that all of the primeval forest communities distributed at different altitudes were composed of 11-13 tree species, but the importance of these tree species varied with altitude. Conifer species gradually took the place of broad-leaved tree species along the altitudinal gradient. Cutting not only made the tree species richness and importance changed, but also further strengthened the trend of tree species replacement. The Shannon-Wiener diversity index of the woody plants in primeval forests varied from 2.454 to 2.544 at the altitudes of 750-800 m, 800-850 m and 850-900 m, which was higher than that (2.250) at the altitude of 900-950 m . Cutting changed this distribution pattern, and enlarged the fluctuation (2.174-2.692) among the communities at different altitudes. The Cody index of primeval forest communities along the altitudinal gradient varied from 1.5 to 3.5, and the community similarity coefficient varied from 0.85 to 0.94. As for the secondary forest communities, their Cody index and community similarity coefficient changed from 0.5 to 6.0 and from 0.68 to 0.91, respectively, indicating that cutting increased the tree species replacement rate, and reduced the community similarity. However, a higher continuity still existed in the secondary forest communities.

CO₂ turbulent exchange in a broadleaved Korean pine forest in Changbai Mountains.

WU Jia-bing¹; GUAN De-xin¹; SUN Xiao-min²; SHI Ting-ting¹; HAN Shi-jie¹; JIN Chang-jie¹

2007, 18(05):  951-956 . 

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The measurement of CO₂ turbulent exchange in a broadleaved Korean pine forest in Changbai Mountains by an open-path eddy covariance system showed that with near neutral atmospheric stratification, the CO₂ and vertical wind components over canopy in inertial subrange followed the expected -2/3 power law, and the dominant vertical eddy scale was about 40 m. The frequency ranges of eddy contributions to CO₂ fluxes were mostly within 0.01-2.0 Hz, and the eddy translated by low frequency over canopy contributed more of CO₂ fluxes. The open-path eddy covariance system could satisfy the estimation of turbulent fluxes over canopy, but the CO₂ fluxes between forest and atmosphere were generally underestimated at night because the increment of non turbulent processes, suggesting that the CO₂ fluxes estimated under weak turbulence needed to revise correspondingly.

Effects of fertilization on fine root diameter, root length and specific root length in Larix kaempferi plantation

YU Li-zhong^1,2; DING Guo-quan^1,3; SHI Jian-wei¹; YU Shui-qiang¹; ZHU Jiao-jun²;ZHAO Lian-fu⁴

2007, 18(05):  957-962 . 

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With 16 years old Larix kaempferi plantation in the mountainous area of eastern Liaoning Province as test object, this paper studied the effects of fertilization on the fine root diameter, root length, and specific root length (SRL) of the first to fifth order roots. The results showed that with ascending root orders, the mean fine root diameter and root length increased, while the SRL decreased significantly. Among the five order roots, the first order roots were the thinnest in diameter, the shortest in length, and the highest in SRL, but the fifth order roots were in reverse. The variance coefficients for the fine root diameter, root length, and SRL increased from the first to the fifth order roots. Except for the first order roots, soil depth had no significant influence on the fine root diameter, root length and SRL.Fertilization affected the fine root diameter, root length, and SRL of the first and the second order roots significantly, but had little effects on other order roots. N fertilization decreased the mean diameter of the first and the second order roots significantly, and N or N+P fertilization decreased the mean length of the first order roots in surface soil (0-10 cm) significantly. The SRL of the first order roots in surface soil increased significantly under N fertilization.

Water parameters of desert xeric shrubs in west Erdos region.

LI Xiao; WANG Ying-chun; ZHENG Rong

2007, 18(05):  963-967 . 

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By using PV technique, this paper studied the turgor pressure (ψ_P), cell elastic modulus (ε), and relative cell volume (RCV) of super xerophytes Potaninia mongolica, Reaumuria soongorica, Tetraena mongolica and Zygophyllum xanthoxylon in west Alashan, with the relationships among the parameters analyzed. The results showed that R. soongorica had the strongest ability to maintain maximum turgor pressure (a=2.4593). The four plants maintained their turgor pressure by different ways, i. e. , P. mongolica maintained it by elastic adjustment (ε_max=8.4005 MPa),R. soongorica by osmotic adjustment (ψ_π100=-3.1302 MPa; ψ₀=-3.5074 MPa), T. mongolica by both osmotic and elastic adjustment, and Z. xanthoxylon by osmotic adjustment, which had weak adjustment ability. The cell wall of P. mongolica was soft and highly elastic, benefiting to the water absorption by root and stem and to the fast water transmission.T. mongolica also had relatively soft and high elastic cell wall, and its ψ_P and ε changed slowly with decreasing RCV, suggesting that this plant had strong ability of holding water and resisting dehydration.

Optimizing management on degraded grassland in Xilin River Basin based on ecological risk assessment.

GU Xiao-he;HE Chun-yang;PAN Yao-zhong;LI Xiao-bing;ZHU Wen-quan;ZHU Xiu-fang

2007, 18(05):  968-976 . 

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By the methods of remote sensing (RS) and geographic information system (GIS), and based on the estimations of degradation degree, risk degree and easy-restoration degree of degraded grasslands, an ecological management index (EMI) model of grassland was established to approach the practical ways of optimizing management of degraded grassland. A case study in the Xilin River Basin of Inner Mongolia showed that this model could quantitatively analyze the degradation degree, risk degree and easy-restoration degree of the grasslands under different optimizing management levels, which was of significance for applying rational measures with pertinence, and beneficial to the optimal allocation of resources during the management of degraded grassland. The EMI model could integrate most concerned information, which made it applicable widely.

Growth of modules and survival space enlargement of Leymus secalimus clones under cultivated conditions in Songnen Plain of Northeast China: An experimental research.

YANG Yun-fei¹; ZHANG Bao-tian¹; ZHANG Chun-hua²

2007, 18(05):  977-982 . 

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Leymus secalimus is a kind of rhizome grass and a species of typical clonal plant. The study showed that under cultivated conditions in the Songnen Plain of Northeast China, the growth of four test L. secalimus clones is with great plasticity. After 153 days of growth in the year of transplanting, the clones had 215 tillers in maximum and 40 tillers in minimum, and the growth pattern accorded with exponential function. The number and biomass of the tillers, rhizomes and buds, as well as the variations of their quantitative characters and of the survival space of the clones in two growth seasons all presented good regularity. The tillers number was in a power allometry growth with the increase of clonal diameter, and the biomass of tillers and rhizomes as well as the number of buds were all in an exponential allometry growth with the increase of the diameter. The number and biomass of the tillers and rhizomes were all in a linear isogony growth with increasing survival space of the clones. When the space was enough and no interspecies competition existed, L. secalimus clones survived first and developed then, and well exercised continuing updating potency.

Correlation analysis of regional vegetation seasonal fluctuation and climate factors based on MODIS-EVI.

PENG Dai-liang¹; HUANG Jing-feng¹; WANG Xiu-zhen²

2007, 18(05):  983-989 . 

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Taking Zhejiang Province as study area, and based on the data of MODIS-EVI, daily mean air temperature and daily precipitation from 52 weather stations, and actual land use in 2001-2004, the time lag cross-correlation analysis was made to relate the seasonal fluctuations of enhanced vegetation index (EVI) of farmland, woodland and garden plot with air temperature and precipitation. The results indicated that in most areas of Zhejiang, EVI had no time lag to air temperature, but about one month lag to precipitation. The time that air temperature or precipitation significantly influenced the seasonal fluctuation of most areas EVI lasted about 50 days. The correlation coefficients of the EVI of farmland, woodland and garden plot with air temperature and precipitation differed with time lags. When the time lag was zero, the correlation coefficient decreased in the sequence of woodland>garden plot>farmland, and when the time lag was not zero, it changed in adverse. The EVI of these three land-use types all had stronger correlation with air temperature than with precipitation, indicating that air temperature had more influence on the seasonal fluctuation of EVI.

Comparison of ecophysiological characteristics of seven plant species in semiarid loess hilly-gully region.

XU Bing-cheng^1,2; SHAN Lun¹; LI Feng-min^1,2

2007, 18(05):  990-996 . 

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The diurnal course of photosynthetic rate, transpiration rate, and leaf water potential (Ψ_L) of five plant species in North Shaanxi loess hilly-gully region were measured in dry seasons. Based on the daily maximum photosynthetic and transpiration rates, daily total assimilation and transpiration, and diurnal change characteristics of Ψ_L, the test plants were classified into different eco-adaptation types.Panicum virgatum L. had high photosynthetic rate, low transpiration rate and high water use efficiency (WUE), and its drought adaption strategy was to delay dehydration by developing high Ψ_L. Medicago sativa had high photosynthetic and transpiration rates but low WUE, while Lespedeza dahurica had low photosynthetic and transpiration rates and low WUE. Their drought adaptation strategies were the same, namely, by increasing Ψ_L to delay dehydration.Bothriochloa ischaemum had high photosynthetic rate, relative high transpiration rate and medium WUE, and its drought-resistant strategy was to decrease Ψ_L to endure dehydration.Astragalus adsurgens had similar characteristics in diurnal courses of photosynthesis with B. ischaemum, and its drought adaption strategy was to delay dehydration by developing low Ψ_L.

Effects of storage conditions and sowing methods on seed germination of Leymus chinensis.

MA Hong-yuan^1,2; LIANG Zheng-wei^1,3

2007, 18(05):  997-1002 . 

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This paper studied the effects of four storage conditions (dry storage at 4 ℃,dry storage at room temperature, storage in moist non- saline-alkali soil at 4 ℃, and storage in moist saline-alkali soil at 4 ℃), three germination substrates (filter paper, non- saline-alkali soil, and saline-alkali soil), and two sowing methods (sowing on and in the substrates) on the seed germination of Leymus chinensis. The results showed that compared with the dry storage at room temperature, dry storage at 4 ℃ improved the germination velocity significantly, but had less effect on germination rate. When stored in moist saline-alkali soil, the germination rate was only 28.8%, in contrast to 73.7% in non-saline-alkali soil. With different sowing methods, the seed germination rates of L.chinensis was in the order of sowing on the surface of non- saline-alkali soil (89.3%)>between papers (68.0%)>on papers (64.0%)>in non-saline-alkali soil (61.3%)>on the surface of saline-alkali soil (25.6%)>in saline-alkali soil (6.0%).

Recovery of bromeliad photosynthesis after exposed to elevated CO₂.

HUI Jun-ai; YE Qing-sheng

2007, 18(05):  1003-1008 . 

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After exposed to elevated CO₂ ［T₁: (600±40) μmol·mol^-1 and T₂: (900±40) μmol·mol^-1］ for 150 days, Guzmania‘Luna’ and Guzmania‘Denise’ were transferred to ambient CO₂ for 30 days to investigate the recovery of their photosynthesis and their key photosynthetic enzyme activities. The results showed that compared with that in CK, the net photosynthetic rate (P_n) of Guzmania‘Luna’ in treatments T₁ and T₂ was decreased by 7.41% and 13.33%, respectively. The P_n of Guzmania‘Denise’ in T₁ was approached to CK, and that in T₂ was higher than CK. After 30 days recovery, the accumulation of soluble sugar and starch in test bromeliads leaves decreased obviously, with the contents being close to those of CK. The rubisco and glycolate oxidase activities in treatments T₁ and T₂ had a decreased difference with CK, but were still lower than those of CK.

Effects of long-term potassium fertilization on potassium fixation in soils under different ecological conditions: A mechanism study.

ZHANG Hui-min^1,2,3; XU Ming-gang²; Lü Jia-long¹; LIU Hong-xia³

2007, 18(05):  1009-1014 . 

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By using X-ray diffraction and laboratory simulation, this paper studied the effects of long-term potassium (K) fertilization on K fixation in black soil, loess soil, and grey desert soil under different ecological conditions and cropping systems. The results showed that long-term K fertilization had greater effects on the K fixation capacity of soils with lower hydromica content. When the K application rate was 400 to 4 000 mg·kg^-1, the K fixation capacity of black soil and loess soil, whose hydromica contents were low or relatively low, decreased by 75-747 mg·kg^-1 and 16-238 mg·kg^-1, respectively, compared with no K application, while no change was observed in grey desert soil whose hydromica content was high. Long-term K application could affect the changes of soil K-bearing minerals, i. e. , slowing down or holding back the transformation of hydromica into mixed-layered mica-smectite, and consequently, decreased the K fixation capacity of soil. The increase of soil slow-available K content and K⁺ saturation owing to the long-term K application also induced the decrease of the K fixation capacity.

Leaching characteristics of nitrogen and phosphorus in inorganic compound fertilizer from latosolic red soil in South China.

ZENG Shu-cai¹; WU Qi-tang²

2007, 18(05):  1015-1020 . 

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A soil column experiment was conducted to investigate the leaching characteristics of nitrogen and phosphorus in inorganic compound fertilizer from latosolic red soil in South China. The results revealed that the leaching loss of soil total nitrogen (TN), NH₄⁺-N and NO₃-N was increased with increasing application rate of inorganic compound fertilizer, and 36.8%-49.2% of fertilizer nitrogen was lost with leaching water. The regression equation of TN loss (y) and N application rate (x) was y=0.3667x+66.483 (R²=0.992). TN and NH₄⁺-N losses mainly occurred in the first 5 leaching events, while NO₃^--N loss continued to be significant till the 9th leaching event. Fertilization rate had no obvious impact on soil dissolved phosphorus (DP), but the leaching loss of total phosphorus (TP) and particulate phosphorus (PP) was increased with increasing fertilization rate. The fertilizer phosphorus loss was within the range of 0.002%-0.01%, and the regression equation of TP loss (y) and P application rate (x) was y=7e^-5x+0.0538 (R²=0.931). Quite different from that of N, the leaching loss of P was a slow and continuous process. Both the leaching loss of NO₃^--N / NH₄⁺-N and of DP/PP was decreased with increasing fertilization rate.

Dynamic change of soil organic matter under different cropping systems in the oasis of Tianshan Mountain northern slope.

XU Wen-qiang^1,2; CHEN Xi¹; LUO Ge-ping¹; TANG Fei^1,2; XIAO Lu-xiang^1,2

2007, 18(05):  1021-1026 . 

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Taking the oasis of lower Sangong River watershed in the Tianshan Mountain northern slope as study area, six kinds of cropping systems, including those of saline-alkaline tolerance crop, food crop, melon and vegetables, economic plants-cotton, economic plants-grape, and economic plants-hop, were selected based on the investigation of local cropping systems, and the dynamic change of soil organic matter under effects of these cropping systems was analyzed by using the laboratory data in 1982, 1999 and 2003. The results showed that land policy and market price had a direct effect on the transformation from annuals cropping system to perennials cropping system, while soil organic matter (OM) content experienced a decline in 1982-1999 owing to the transformation from planting other crops to planting cotton, and a rise in 1999-2003 resulting from the conversion from planting food crops and cotton to planting perennial crops. On the whole, the soils in the oasis presented as a carbon sink, suggesting that the change of artificial vegetation in the oasis was helpful to the accumulation of soil OM, and beneficial to the sustainable use of farmland.

Effects of conservational tillage on aggregate composition and organic carbon storage in purple paddy soil.

TANG Xiao-hong^1,2; SHAO Jing-an^1,2; GAO Ming^1,2; WEI Chao-fu^1,2; XIE De-ti^1,2; PAN Gen-xing³

2007, 18(05):  1027-1032 . 

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A 13 years experiment was conducted to study the effects of conservational tillage on the aggregate composition and organic carbon storage in purple paddy soil of Sichuan Basin. The results showed that under no-tillage and ridge culture (rice-rape) (NR-RR), no-tillage and plain culture (rice-rape) (NP-RR), no-tillage and ridge culture (rice-green manure) (NR-RGM), tillage and ridge culture (rice-rape) (TR-RR), and tillage and plain culture (rice-rape) (TP-RR), the proportion of macroaggregates in 0-10 cm soil layer was 23%, 69%,9%, 36%, and 28% higher than that under conventional tillage (CT) (12%), respectively, while in 10-20 cm soil layer, this proportion under conservational tillage was 9%-38% lower than that under CT. The organic carbon storages in the macroaggregates at the depth of 0-10 cm were 13%, 31% and 32% higher under no-tillage and ridge culture (rice-fallow) (NR-RF), NR-RR and NR-RGM than under CT, respectively, while that at the depth of 10-20 cm was 28%-54% lower. The differences in organic carbon storage between macro- and microaggregates were smaller in 10-20 cm layer than in 0-10 cm layer. Under conservational tillage, the organic carbon storage was 8%-28% higher in 0-10 cm layer but 4%-22% lower in 10-20 cm layer, compared with that under CT. After converted from CT to conservational tillage for 13 years, the mean organic carbon sequestration rate was 53 g ·m^-2·a^-1 and 25 g·m^-2·a^-1 at the depths of 0-10 cm and 10-20 cm, while under CT, it was 26 g·m^-2·a^-1 and 33 g·m^-2·a^-1, respectively. Conservational tillage was favorable to the formation of macroaggregates in surface soil layer and the enhancement of soil total organic carbon storage.

Effects of 3,5-dimethylpyrazole phosphate (DMPZP) on soil nitrification.

SHI Yun-feng^1,2; WU Zhi-jie¹; CHEN Li-jun¹; SUN Zhi-mei^1,2

2007, 18(05):  1033-1037 . 

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With aerobic incubation test, this paper studied the effects of 3,5-dimethylpyrazole phosphate (DMPZP) on soil nitrification, taking dicyandiamide (DCD) as reference. The results indicated that when the dosage was 1.0% of applied N, DMPZP could significantly inhibit the oxidation of soil ammonium, increase soil NH₄⁺-N concentration, and decrease soil NO₃^--N concentration. The inhibitory effect of DMPZP increased with its increasing dosage. DCD showed a higher efficacy when its dosage was the same with DMPZP, but a lower efficacy when the DMPZP was applied twofold. However, the efficacy of equimolar DMPZP was significantly higher than that of DCD, because of the smaller molecular weight of DCD. The highest inhibitory effect of DMPZP was observed during the period of 7-14 days after its application, with an inhibition rate higher than 30%. Compared with the control, the apparent inhibition rate was decreased by 29.3% and 41.7% on the 7^th day, and by 18.6% and 34.3% on the 14^th day when the application rate of DMPZP was 1.0% and 2.0% of applied N, respectively. DMPZP could also slow down the falling rate of soil pH, but no significant difference was observed between the treatments of applying DMPZP and DCD.

Weed biodiversity in winter wheat field of loess soil under different fertilization regimes.

GU Qiao-zhen; YANG Xue-yun; SUN Ben-hua; ZHANG Shu-lan; TONG Yan-an

2007, 18(05):  1038-1042 . 

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Employing an inverted ‘W’ investigation procedure with 9 sampling locations and adopting a biodiversity analysis approach integrated with typical statistic method, this paper studied the effects of different long-term stationary fertilization regimes on the weed biodiversity in winter wheat fields on loess soil. The results showed that in the experimental plots, there were 16 weed species belonging to 10 family and 16 genera, occupying about 34% of the total number of weed species in winter wheat fields in Shaanxi Province. The weed biodiversity was decreased with the improvement of soil nutrient status. There were 3-5 weed populations in treatments NPK and NPK plus organic materials, and 6-8 populations in treatments CK, N, NK and NP. The relative abundance of weeds ranged from 0 to 73%, and the ranges of Shannon’s diversity index, Shannon’s evenness index and Margalef’s species richness index were 0.2-1.08,0.05-0.26 and 0.26-1.26, respectively.All of these 3 parameters were higher in unbalanced than in balanced fertilization treatments, and the differences between unbalanced and balanced fertilization treatments were significant in most case, which was probably due to the different status of available soil nutrients and might have different effects on the growth of weeds.

Effects of fertilization on microbial biomass C and N in paddy soils derived from different parent materials.

ZHOU Wei-jun¹; ZENG Xi-bai²; ZHNAG Yang-zhu¹; ZHOU Qing¹; GUO Hai-yan¹; YAN Xiong¹; CHEN Jian-guo¹

2007, 18(05):  1043-1048 . 

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Based on the monitoring of soil fertility, this paper studied the characteristics of microbial biomass C (MBC) and N (MBN) in paddy soils derived from different parent materials in Hunan Province. The results showed different fertilization systems had different effects on soil MBC and MBN. After 18 years fertilization, the MBC and MBN in different paddy soils had similar variation trend, with the sequence of paddy soil derived from lake sediment>from river alluvium and quaternary red earth>from limestone>from shale. Soil MBC content ranged from 259.5 to 864.4 mg·kg^-1, while MBN ranged from 8.7 to 70.7 mg·kg^-1. Fertilization could increase soil MBC and MBN markedly. Organic fertilizer was the main element for the promotion of soil MBC and MBN, and combined application of organic and inorganic fertilizers could obtain the greatest effect. The increment of soil MBC and MBN after applying inorganic fertilizer and its combination with organic fertilizer was 407.6 and 59.2 mg·kg^-1， in maximum, and the maximum increasing rate was 102.8% and 514.8%, respectively, compared with no fertilization.

Heterosis of photosynthetic performance of maize.

LI Xia¹; DING Zai-song²; LI Lian-lu¹; WANG Mei-yun¹; ZHAO Ming²

2007, 18(05):  1049-1054 . 

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Taking four maize inbred lines with different photosynthetic rate and their two hybrids as test materials, the diurnal variations of their photosynthesis parameters in silking stage were measured to study the heterosis of photosynthetic performance. The results showed that the net photosynthetic rate (P_n), transpiration rate (T_r) and stomatal conductance (G_s) all presented obvious single-peaked curve in a day, with the peak value occurred at 10:00-12:00, 12:00 and 10:00-12:00, respectively, while water use efficiency (WUE) had a “V” type variation trend, with the lowest value appeared at 12:00. The diurnal variation of P_n and T_r correlated markedly with G_s, suggesting that G_s played an important role in regulating the diurnal variation of P_n and T_r. P_n, T_r and G_s had higher heterosis in the afternoon than in the morning, while WUE was in reverse, indicating that maize hybrid had higher resistance to high temperature and dehydration in the afternoon, which provided a new path to select varieties with high net photosynthetic rate.

Effects of transplanting date and density on appearance quality of greenhouse single-flower cut chrysanthemum.

LI Xiang-mao¹; DAI Jian-feng²; LUO Wei-hong²; CHEN Fa-di¹; GU Jun-jie³; LU Jin-hua³

2007, 18(05):  1055-1060 . 

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Transplanting date and density are the important factors affecting the appearance quality of chrysanthemum. The study on the greenhouse single-flower cut chrysanthemum (Chrysanthemum morifolium cv. Shenma) showed that within the ranges of test transplanting date and density, the plant height and neck length increased, while the leaf number per plant, stem diameter, plant fresh mass and flower diameter decreased with the delay of transplanting date and the increase of transplanting density. No effect of transplanting density was observed on plant height. For the production of single-flower cut chrysanthemum in non-heated greenhouse in Shanghai, the optimal transplanting date and density to achieve the top rank of quality (rank A) were the middle ten days of August and 64 plants·m^-2, and those to achieve the second rank of quality (rank B) were from mid August to early September and 72-80 plants·m^-2, respectively. The results obtained in this study offered references in establishing the prediction model of greenhouse single-flower cut chrysanthemum appearance quality based on light, temperature, and transplanting date and density.

Infection of Phytophthora capsici on pepper: Models and affecting factors.

LIU Xue-min¹; ZHOU Yan-ling²; LI Li-jun³

2007, 18(05):  1061-1065 . 

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Under controlled conditions in growth chamber, this paper studied the mortality of pepper seedlings caused by Phytophthora capsici. The results showed that soil temperature and water content were the important factors affecting the infection of P. capsici, and their optimum values for the infection were 22-28 ℃ and 40%, respectively. The relationships of the mortality of pepper seedlings caused by Phytophthora capsici with soil temperature, water content and their interactions could be described by mathematical models. Field observation suggested that Gompertz model was the best one for describing the epidemic dynamics of the disease, and the incidence of P. capsici was significantly related to the initial incidence of P. capsici, soil temperature, soil water content, and air temperature. The forecast model of P. capsici incidence on field pepper was established.

Effects of potassium level on photosynthetic characteristics and chloroplast submicroscopic structure of muskmelon leaves.

LIN Duo^1,2; HUANG Dan-feng¹; YANG Yan-jie²; CHEN Ning²

2007, 18(05):  1066-1070 . 

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With soilless culture in greenhouse, this paper studied the effects of three potassium (K) levels (120, 240, and 360 mg·L^-1) on the photosynthetic characteristics and chloroplast submicroscopic structure of muskmelon cv. ‘Tiantian No. 1’ leaves. The results showed that at low (120 mg·L^-1) and high (360 mg·L^-1) K levels, the net photosynthetic rate (P_n) decreased, chloroplast lamellar structure disordered, and lamella number decreased. No significant effects were observed on CO₂ compensation point (70 μl·L^-1), saturation CO₂ for photosynthesis (600 μl·L^-1) and light compensation point (50 μmol·m^-2·s^-1) at the three K levels. The saturation light for photosynthesis, carboxylation efficiency and apparent quantum yield at 240 mg·L^-1 K level were significantly higher, being 1 200 μmol·m^-2·s^-1, 0.1364 and 0.0237, respectively. Under the conditions of this study, the optimal K level in the nutrient solution for muskmelon soilless culture was 240 mg·L^-1.

Foraging behavior and pollination ecology of Bombus lucorum L. and Apis mellifera L. in greenhouse peach garden

AN Jian-dong; WU Jie; PENG Wen-jun; TONG Yue-min; GUO Zhan-bao; LI Ji-lian

2007, 18(05):  1071-1076 . 

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From 2004 to 2006, this paper studied the foraging behavior and pollination ecology of two Chinese bee species Bombus lucorum L. and Apis mellifera L. in greenhouse peach garden in Beijing. The results showed that both of the bee species were able to substitute manual work to provide effective pollination, but their foraging behavior and pollination effect differed significantly in terms of their working timing and visiting frequency, temperature, and the location of flowers on peach tree. B. lucorum L. preferred to collect pollen and release it mainly by vibrating their wings, while A. mellifera L. gathered and released pollen mainly through body touch on flowers. Moreover, B. lucorum L. could work at lower temperature and visit more flowers each day, while the activities of A. mellifera L. were easily affected by weather conditions including sunlight and temperature. It was often found that A. mellifera L. bumped itself on greenhouse ceiling because of its strong photokinesis.

Effects of transgenic corn expressing Bacillus thuringiensis cry1Ab toxin on population increase of Rhopalosiphum maidis Fitch.

LI Li-li^1,2; WANG Zhen-ying¹; HE Kang-lai¹; BAI Shu-xiong¹; HUA Lei2

2007, 18(05):  1077-1080 . 

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A laboratory study was made on the effects of transgenic corn expressing cry1Ab toxin from the bacterium Bacillus thuringiensis (Bt) on the life table of an experimental population of corn leaf aphid Rhopalosiphum maidis Fitch. The results showed that no obvious negative effects of two Bt corn hybrids DK647BTY (event MON810) and NX4777 (event Bt11) were observed on the net reproductive rate, average generation time, innate capacity for increase, and finite rate of increase of R. maidis, and there were no significant differences in the rate of alate, mortality of nymph, and longevity and fecundity duration of corn leaf aphid when feeding on Bt and non-Bt corn hybrids, suggesting that Bt corn expressing cry1Ab toxin had no side-effects on the development and reproduction of R. maidis.

Genetic diversity of Pardosa pseudoannulata populations and its relationships with habitats.

SUN Ji-ying; PENG Guang-xu; HU Bo; FU Xiu-qin; YAN Heng-mei

2007, 18(05):  1081-1085 . 

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A random amplified polymorphic DNA (RAPD) analysis was made on the Pardosa pseudoannulata populations collected from eight habitats in Central-south China, Southwest China, and Hainan Island. 10 from 50 primers were selected,and 84 bands of 200-2 500 bp fragments were amplified, among which, 62 bands (73.8%) were polymorphic, suggesting an obvious polymorphism of the populations.As estimated by Shannon index, genetic similarity index and genetic distance, the total genetic diversity index of the spider was 0.5177, with the genetic variation being 64.24% within the P. pseudoannulata populations and 35.76% among the populations. The genetic distance among the eight populations ranged from 0.0753 to 0.3725, with an average of 0.2426, indicating that the eight populations engendered adaptive variations with different habitats. Multiple regression analysis showed that annual mean air temperature and pesticide application were the main factors restricting P. pseudoannulata to be a dominant insect species in rice field.

Effects of grazing on zoobenthos community in beach.

ZHAO Yun-long; AN Chuan-guang; LIN Ling; DUAN Xiao-wei; ZENG Cuo; CUI Li-li

2007, 18(05):  1086-1090 . 

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In May (spring) and October (autumn) 2005, the effects of grazing on the zoobenthos community in Chongming Dongtan wetland of Shanghai were investigated. A total of 3 transects including 90 sampling plots were set up. Transects Ⅰ and Ⅱ were in feeding area, and transect Ⅲ was in non-pasture area. All of these three transects were set in mid-tidal zone. 13 zoobenthos species were observed, with 7 species of arthropod, 4 species of mollusk, and 2 species of annelid. In spring, there were 6, 8 and 10 species in transects Ⅰ, Ⅱ and Ⅲ, while in autumn, the species number was 6, 8 and 12, respectively. The mean abundance of zoobenthos community in all transects was higher in autumn than in spring, and transect Ⅲ had the highest mean abundance and biomass both in autumn and spring. Transect Ⅲ also had the highest evenness, richness and diversity, indicating that grazing could change the species distribution of zoobenthos, and affect their abundance and biomass to different degree.Grazing had made certain negative effects on the biodiversity of zoobenthos community in Chongming Dongtan wetland.

Influence of cascaded exploitation of small hydropower on phytoplankton in Xiangxi River.

WU Nai-cheng^1,2; TANG Tao¹; ZHOU Shu-chan^1,2; FU Xiao-cheng^1,2; JIANG Wan-xiang^1,2; LI Feng-qing^1,2; CAI Qing-hua¹

2007, 18(05):  1091-1096 . 

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With the five small hydropowers (SHPs) from up-to downstream of Xiangxi River as test objects, this paper studied the influence of SHPs cascaded exploitation on the phytoplankton in the river. The results showed that phytoplankton assemblages were dominated by diatoms, occupying 95.54% of the total number of species. Achnanthes linearis, A. lanceolata var. elliptica and Cocconeis placentula were the most abundant species, with the relative abundance being 23.96%, 18.62% and 12.48%, respectively. The average algal density at 25 sampling sites was 6.29×10⁵ ind·L^-1, with the maximum of 1.81×10⁶ ind·L^-1 and the minimum of 2.35×10⁵ ind·L^-1. Two-way ANOVA indicated that water flow velocity was the main factor affecting the phytoplankton. The establishment of the cascaded SHPs on the river made the habitat of lower reach has a significant difference with the others, resulting in a dramatic change of many parameters including Margalef diversity index, species richness, generic richness, taxonomic composition, and the percentage of diatoms.

Succession character of salt marsh vegetations in Chongming Dongtan etland.

YAN Qian^1,2; LU Jian-jian¹; HE Wen-shan¹

2007, 18(05):  1097-1101 . 

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This paper studied the ecological character, importance value, aboveground biomass and its N content of salt marsh vegetations in Chongming Dongtan wetland in the process of succession. The results indicated that with the increase of altitude, the importance value of Scirpus mariqueter, a representative species at early succession stage, decreased gradually, while those of Spartina alterniflora and Phragmites australis increased. The biodiversity of the vegetations increased with succession. During growth period (from March to October), the aboveground biomass of the three species varied in single hump curve, with the peak in July and August. The N content had a decreasing trend, while the N capacity showed a single-peak curve. The estimated annual N accumulation in aboveground biomass was 383.4 t for P.australis, 50.5 t for S. mariqueter, and 39.3 t for S. alterniflora.

Relationships between pollutants discharge and red tide occurrence in Shenzhen eastern coast.

JIANG Tian-jiu^1,3; NIU Tao²; YING Wen-ye²

2007, 18(05):  1102-1106 . 

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The study on the effects of pollutants discharge on red tide occurrence in eastern sea area of Shenzhen showed that the occurrence frequency of dinoflagellate red tide had significant positive correlations with the net discharge of total nitrogen (TN) and total phosphorous (TP) as well as the N/P ratio of the discharge. The thresholds of net discharged TN and TP were estimated to be 3.917×10³ t and 2.123×10⁴ t, respectively. No significant correlation was observed between diatom red tide and alongshore pollutants discharge. An example was given to illustrate the means of pollutants discharge control.

Pollutant components and microbial community structure of oil-polluted soils after converted from paddy field to upland.

REN Rui-xia^1，2; ZHANG Ying¹; LI Hui¹; WANG Rong¹; XU Hui ¹; CHEN Guan-xiong¹

2007, 18(05):  1107-1112 . 

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With the oil-polluted soils after converted from paddy field to upland field for different years in the Shenfu wastewater irrigation area of Shenyang as test materials, the concentrations of their oil pollutants were determined, and the microbial community structure was investigated by denaturing gradient gel electrophoresis (DGGE) and phospholipids fatty acid (PLFA) methods. The results showed that the proportions of total polynuclear aromatic hydrocarbons (PAHs) in total petroleum hydrocarbons (TPHs) and of high molecular weight PAHs in total PAHs increased with the increasing years of field conversion. Total phospholipid fatty acids (PLFAs) had a significant positive correlation with total TPHs, but no correlation with total PAHs. Both DGGE and PLFA analyses indicated that the community structure of soil microbes was mainly correlated with geographical location, and changed obviously when the concentrations of oil pollutants in soil increased to a definite level.

Effects of earthworm inoculation and straw amendment on soil microflora and microbial activity in Cu contaminated soil.

WANG Dan-dan; LI Hui-xin; WEI Zheng-gui; LIU Man-qiang; WANG Xia; HU Feng

2007, 18(05):  1113-1119 . 

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In this paper, the dynamics of microflora and microbial activity in soil added with 0, 100, 200 and 400 mg·kg^-1 of Cu²⁺ were studied under effects of inoculating earthworm and applying straw. Four treatments were installed, i. e. , CK, surface application of straw (M), inoculation of earthworm (E), and M plus E (ME). The results showed that Cu contamination had inhibitory effect on soil bacteria and actinomycetes, but no effect on soil fungi. Straw amendment increased soil fungi significantly, while earthworm inoculation could increase the numbers of soil bacteria and actinomycetes significantly but had little effect on soil fungi. When the Cu concentration was higher than 200 mg·kg^-1, soil microbial biomass carbon was depressed, but earthworm inoculation and straw amendment could enhance it, with most significant effect under the combination of these two treatments. Earthworm inoculation and straw amendment could enhance soil basal respiration markedly. When the Cu concentration was lower than 200 mg·kg^-1, treatment M had the highest soil basal respiration, being about 3.06-5.58 times higher than that of CK, while at Cu≥200 mg·kg^-1, soil qCO₂ followed the sequence of ME>E>M>CK. Treatments M and E had no effects on soil NH₄⁺-N. As for soil NO₃^--N, treatment E could increase it significantly, but treatment M was in adverse. Treatment ME induced the lowest soil NO₃^--N. In a definite degree, earthworm inoculation and straw amendment could mitigate the negative impact of Cu contamination on soil microflora and microbial activity.

Single and joint toxicity of perchloroethylene and cadmium on Ctenopharyngodon idellus.

WANG Gui-yan^1,2,3; ZHOU Qi-xing^2,4; HU Xiao-min¹; HUA Tao⁴; LI Feng⁵

2007, 18(05):  1120-1124 . 

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In this paper, the single and joint toxicity of perchloroethylene (PCE) and cadmium (Cd) on grass carp (Ctenopharyngodon idellus) was observed by static test method, and the joint toxicity was evaluated by additive index method. The results showed that the LC₅₀ of PCE and Cd in 24, 48, 72 and 96 h was 49.12, 41.68, 36.37 and 34.30 mg·L^-1, and 45.58, 34.81, 28.63 and 24.05mg·L^-1, respectively. Both the two test chemicals had high toxicity on C. idellus, and Cd had higher single toxicity than PCE. When the toxicity ratio was 1∶1 and exposure time was 24, 48, 72 and 96 h, the LC₅₀ of PCE and Cd was 24.63, 12.54, 9.88 and 7.08 mg·L^-1, and 17.11, 8.71, 6.87, 4.92 mg·L^-1, and the additive index (AI) was 0.14, 0.81, 0.95 and 1.43, respectively, indicating that the joint toxicity of PCE and Cd was synergistic, and increased with time. At the concentration ratio of 1∶1, the LC₅₀ of PCE and Cd in 24, 48, 72 and 96 h was 17.00, 11.81, 10.61 and 9.19 mg·L^-1, and 17.00, 11.81, 10.61 and 9.19 mg·L^-1, and the AI was 0.39, 0.70, 0.51 and 0.54, respectively, and the joint toxicity was also synergistic.

Tritrophic system of tree-trunkborer-insect natural enemy association.

WEI Jian-rong^1,2,3; YANG Zhong-qi²; DAI Jian-qing¹; DU Jia-wei¹

2007, 18(05):  1125-1131 . 

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Trunkborers, mainly bark beetles and cerambycids, are the important insect pests of forests, which can cause serious damage to forest ecosystem. Taking bark beetle and long-horned beetle as the examples, this paper summarized the research progress on the tritrophic system of tree-trunkborer-insect natural enemy association, with the past ten years research results on semiochemicals release source, active compounds identification, and release dynamics of volatiles introduced. The chemical signals selection of natural enemies and their visual function in finding hosts or preys, as well as whether there were other biological active compounds beyond this tritrophic system, which could influence the natural enemy’s behaviors, were also discussed.

Controlling effects of multiple species coexistence on rice diseases, pests and weeds in paddy field ecosystem.

WANG Han¹; TANG Jian-jun¹; XIE Jian²; CHEN Xin¹

2007, 18(05):  1132-1136 . 

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Establishing a species-diversified cropping system to control crop diseases, insect pests and weeds is an important approach to sustainable agricultural development. This paper reviewed the researches on paddy field species-diversified cropping systems at home and abroad, and discussed the controlling effects and mechanisms of multiple species coexistence on rice diseases, pests and weeds control. The multiple species coexistence models such as rice-fish, rice-duck, rice-azolla-fish and rice-azolla-duck had effective controlling effects on Thanatephorus cucumeris (Frank) Donk, Nilaparata lugens Stal,Chaphalocrocis medinalis Gueneeand, and weeds. Other models like intercropping rice with Zizania caduciflora L. and with other wetland crops also had effective effects in controlling the occurrence and spread of Pyricularia grisea. It was suggested that further studies should be strengthened from the viewpoints of crop culture, molecular biology, and chemical ecology.

Application of rDNA-ITS sequence in entomology.

LIU Yan-bin^1,2; JI Lan-zhu¹

2007, 18(05):  1137-1142 . 

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As an important complement of the information obtained from mtDNA, the internal transcribed spacer (ITS) of nuclear ribosomal DNA is being increasingly applied in entomological study. This paper introduced the structure and characters of ITS, and summarized its applications in identifying insect species and in studying their relative relationships and phylogenesis, evolution and spread, and relations with environment. ITS was mainly applied in identifying the species whose morphological differences were subtle. The research of relative relationships and phylogenesis was aimed to understand the species origin and evolution, while the study on the relations with environment was mainly focused on sociological and parasitic insects. The problems and their possible causes in ITS application were discussed.

Research advances in animal toxicology of polybrominated diphenyl ethers and expectations on their ecotoxicology.

XU Zhi-qiang^1,2; ZHOU Qi-xing^1,3; ZHANG Que⁴; ZHU Ling-yan³

2007, 18(05):  1143-1152 . 

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As a kind of flame retardants, polybrominated diphenyl ethers (PBDEs) have been widely applied in industrial products and house wears, and detected in soil, sediments, air, and living organisms. PBDEs are proved to be harmful to mammals, birds, and fish. Great concern has been aroused because of their wide spreading, stable structure, and uncertain risk to human health. Based on the foreign toxicological researches and findings, this paper summarized the accumulation and elimination of PBDEs in organisms, their effects on the hepatic enzyme activities, thyroid gland, nerve and immune system, and reproduction and development of animals, and potential risk to human health. The problems in PBDEs toxicological research were analyzed, and future directions in this field were discussed.

Concept, pollution character and environmental effect of urban surface dust.

CHANG Jing¹; LIU Min¹; HOU Li-jun²; XU Shi-yuan¹; LIN Xiao¹; Ballo Siaka¹

2007, 18(05):  1153-1158 . 

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Urban surface dust is a major concern of urban non-point source pollution, which has been noticed by the scientists abroad since the 1970s, and many research achievements have been made. However, no sufficient recognition was given in China. This paper put forward a new idea about the concept of urban surface dust, summarized the development stages and present status of urban surface dust research both at home and abroad, and brought forward the key points and directions of further research. Urban surface dust is a complex environmental carrier, acting as the “sink” and “source” of pollutants. It is a valuable archive of environmental information, and can act as a useful indicator of local environmental pollution status. The study on urban surface dust should become a new focus of urban environment research in China, which is of significance in urban ecology and in the management of non-point source pollution.

Time shift invariant properties of commonly used growth models and their application.

WAN Xin-rong; LIU Wei; WANG Meng-jun; WANG Guang-he; ZHONG Wen-qin

2007, 18(05):  1159-1162 . 

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Growth analysis is of significance in estimating the age of organisms, but in reality, the initial time for this estimation adopted by different authors is not always the same. For example, in the growth analysis of mammals, the age could be birth age or conceptional age. Such a discrepancy in time, the so-called time shift, may generate different results in parameter-simulating process. In this paper, the time-shift invariant properties of commonly used three-parameter growth models, i. e. , Spillman, Logistic, Gompertz and Bertalanffy models, were analyzed, and the results showed that these four models all had the invariant characters under any time shift, namely, no matter which initial time (age) of estimation was adopted, the same fitness was obtained. A case study was made with the growth data of Phodopus roborovskii and by adopting both birth age and conceptional age.

Random amplified polymorphic DNA identification of six Bactrocera (Diptera:Tephritidae) species in Yunnan Province of Southwest China.

ZHANG Liang; ZHANG Zhi-ying

2007, 18(05):  1163-1166 . 

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In this paper, the genetic relationships among six fruit fly species of Bactrocera in Yunnan Province of Southwest China, i. e. , B. tau, B. scutellaris, B. scutellata, B. cucurbitae, B. dorsalis and B. correcta, were studied by using the technique of random amplified polymorphic DNA (RAPD). Five primers with good repetition and high polymorphism were screened from 131 primers, and a total of 302 bands were amplified, among which, 111 bands were of genetic polymorphism. The primers OPC-01, OPI-17, OPL-07, OPL-08 and OPL-16 could be used for the identification of the 6 fruit fly species.

Effects of starvation on digestive enzyme activities of Monopterus albus.

YANG Dai-qin^1,2; CHEN Fang¹;RUAN Guo-liang^1,2;HU Cheng-wen^1,2;CAO Sheng-huan¹

2007, 18(05):  1167-1170 . 

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Starvation is a major environmental stress, which has a broad effect on the physiology and ecology of aquatic animals. In this study,Monopterus albus was starved for 30 days at (20±0.5) ℃, and the activities of protease, trypsin, amylase and lipase in its digestive organs were measured on the 0, 3rd, 5th, 10th, 15th, 20th, and 30th day of starvation. The results showed that starvation had definite effects on the activities of all test enzymes. With the prolongation of starvation, the activities of test enzymes decreased, which was most significant when the fish was starved for 5-10 days. After 10 days of starvation, the decreasing trend of the enzyme activities became less obvious.

Effects of salinity on feeding rhythm and feces excretion time of Monopterus albus.

ZHOU Wen-zong^1,2; QIN Pei¹

2007, 18(05):  1171-1174 . 

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An indoor experiment was conducted to study the effects of different salinity (0, 2, 4, 6, 8, 10 and 12 g·L^-1) on the feeding rhythm and feces excretion time of feeding-domesticated Monopterus albus. The results showed that salinity had no significant effects (P>0.05) on the feeding rhythm of M. albus, but the proportions of food consumption by M. albus were significantly different (P<0.01) during different time sections.M. albus only had one peak of food consumption during the whole day, and its feces excretion was in batches which varied with salinity. There were three batches of feces excretion at salinity of 0, 2, 8, 10 and 12 g·L^-1, while four and five batches at salinity of 4 and 6 g·L^-1, respectively. At different salinities, the time of the same batch feces excretion was significantly different (P<0.01),e. g. , in control group, the time of first three batches feces excretion was delayed for 4-25 h, compared with that in other groups. These research results would provide theoretic basis for feeding management and water quality control in M. albus culture in saline-alkaline and bottomland water area.