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    20 October 2008, Volume 19 Issue 10
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    Articles
    Effects of litter coverage and watering frequency on seed germination and seedling survival of Castanopsis fissa.
    WANG Jun1,2;WANG Zhuo-han1,2;YANG Long1,2;REN Hai1
    2008, 19(10):  2097-2102 . 
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    Castanopsis fissa is an important pioneer species commonly used in the restoration of degraded subtropical grassland in southern China. The study on the effects of litter coverage and watering frequency on the seed germination and seedling survival of C. fissa showed that the effects of litter coverage depended on soil moisture condition. When the watering frequency was 1 time per day, litter covering could restrain seed germination and increase seedling mortality; while watering 2 or 3 times per day, the covering would ameliorate soil moisture condition, and benefit seed germination and seedling establishment. The biomass of C. fissa seedlings was enhanced significantly by litter covering. It was suggested that keeping a litter layer on soil surface could benefit the seed germination and seedling survival of C. fissa to restore subtropical shrub land.
    Gap features and renewal dynamics in secondary natural Pinus tabulaeformis forest in hilly loess region.
    ZHANG Xi-biao1,2; WANG Rui-juan2; ZHOU Tian-lin2; SGANGGUAN Zhou-ping1
    2008, 19(10):  2103-2108 . 
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    Taking the secondary natural Pinus tabulaeformis forest in hilly loess region as research object, the shape, size structure, distribution, gap-maker features, and renewal dynamics of gaps were investigated. The results showed that the areas of canopy gap (CG) and extended gap (EG) appeared to have a skewed and small gap-dominated distribution. The CGs had an average area of 31.15 m2, and those with an area of 20-40 m2 made up the highest proportions in number and area, accounting for 38.24％ and 30.50％, respectively; while the EGs had an average area of 58.04 m2, and those with an area of 30-60 m2 made up the highest proportions in number and area, accounting for 36.77％ and 27.79％, respectively. The average CG area accounted for 53.67％of the average EG area. The gaps were mainly elliptical, and their ages were mainly within 10-20 years, which occupied 33.82％ of the total. The gaps were mainly with a height of 14-16 m, and those with a height of 18-22 m made up 36.8％ of the total. The gaps were mainly formed by the trees being broken at their bases and the standing dead trees, which made up 47.66％ and 23.44％ of all gap-makers, respectively, and thinning and unlawful felling were the major factors in gap formation. The tree deaths from lowered resistance due to tree- ageing, drought, and pest and diseases were one of the reasons for gap formation. The gap-makers per gap numbered 1.89 on average, and most of the gaps were formed by two gap-makers. The gap-makers were mainly Pinus tabulaeformis, followed by Populus davidiana, Betula platyphylla, and Quercus liaotungensis. The diameters of the gap-makers appeared to have a remarkably skewed normal distribution, and the diameters commonly ranged in 10-20 cm and 21-30 cm, taking up 25.0% and 45.31%, respectively. This skewed normal distribution agreed with the skewed area distribution of the gaps. In forest gap, trees had a better regeneration condition, and Chinese pine seedings had no age-discontinuity; while in the understory of Chinese pine, seedings had an obvious discontinuity in age-structure.
    Effects of exotic Larix kaempferi on forest soil quality and bacterial diversity.
    YANG Xin; CAO Jing; DONG Mao-xing; MA Xiao-jun
    2008, 19(10):  2109-2116 . 
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    The study on the soil quality and bacterial diversity under 8-30 years old exotic Larix kaempferi, native Pinus tabulaeformis, and secondary deciduous broadleaf forest stands in Xiaolongshan Mountains of Gansu, Northwest China showed that the soil pH under different forest stands had no distinct variation, but soil moisture content was increased with increasing age of forest stands. Soil organic matter and nitrogen contents were the highest under secondary deciduous forest, followed by under L. kaermpferi, and P.tabulaeformis. However, the soils under different ages of forest stands had no obvious variations in their organic matter and nitrogen contents,suggesting that tree species was the main factor affecting soil quality. Compared with P. tabulaeformis, exotic L. kaempferi could significantly increase soil organic matter and nitrogen contents. PCR-DGGE banding patterns suggested that the soil under secondary deciduous broadleaf forest had the highest bacterial diversity, followed by under L. kaempferi, and P. tabulaeformis. The sequenced DGGE bands were classified into three bacterial groups, i.e., Proteobacteria, Cytophaga-Flavobacterium-Bacteroides, and high G+C content gram-positive type, among which, Proteobacteria occurred most frequently. Further detailed analyses suggested that the soil bacterial compositions under exotic Larix stands were more similar to each other than those under pine and secondary deciduous broadleaf forests. It was concluded that exotic L. kaempferi induced the changes of microbial diversity in the forest soils of this region.
    Characteristics of soil salinity profiles and their electromagnetic response under various vegetation types in coastal saline area.
    YANG Jing-song; YAO Rong-jiang;ZOU Ping; LIU Guang-ming
    2008, 19(10):  2117-2124 . 
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    Aiming at the intrinsic relationships between vegetation type and soil salinity in coastal saline area, and by using electromagnetic induction EM38 and field sampling method, the characteristics of soil salinity profiles under various vegetation types in typical coastal saline region of the Yellow River Delta were analyzed, and the electromagnetic response characters of the salinity profiles were compared. The results showed that across the study area, soil salinity exhibited the characteristics of top enrichment and strong spatial variation. The horizontal electromagnetic conductivity EMh responded well to soil salinity at upper layers, and the response of vertical electromagnetic conductivity EMv to soil salinity at deeper layers was superior to that of EMh. Soil salinity profiles were classified into inverted, normal, and uniform types. The vegetation types of inverted salinity profiles were mainly bare land and Suaeda salsa, while those of normal and uniform salinity profiles were cotton and weed, respectively. The sequence of top enrichment intensity was bare land >S. salsa land>weed land>cotton land. With the change of vegetation type of cotton-weed-S. salsa-bare land, the EMv/EMh value of salinity profiles decreased gradually. Nonparametric test results showed that there was a significant correlation between vegetation type and electromagnetic response characters, and the distribution characters of EMv/EMh under various vegetation types varied significantly.
    Seasonal variation of soil heat conduction in a larch plantation and its relations to environmental factors.
    WANG Wen-jie1; CUI Song1; LIU Wei1; ZU Yuan-gang1; SUN Wei1 ; WANG Hui-min2
    2008, 19(10):  2125-2131 . 
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    Based on a 3-year (2003-2005) observation of soil heat flux (SHF) in a larch (Larix gmelinii) plantation, the characteristics of soil heat conduction in the plantation and their relationships with environment factors were analyzed. The results showed that there was an obvious seasonal variation of SHF in different years and sampling sites. The SHF was positive from April to August and mostly negative from September to next March, with an almost balance between heat income and outcome at annual scale. Solar net radiation had significant effects on the SHF and soil heat conductance (k), and an obvious time-lag effect was found, with 4-5 hours’ time-lag in winter and 2-3 hours’ time-lag in summer. Based on the real-time measurement of SHF and soil temperature difference at the study sites, the k value was significantly higher in early spring (P<0.05), but no significant difference was observed in other seasons (P>0.05). Therefore, when we use the observation data of soil temperature from weather stations to estimate soil heat flux, the k value in spring (from March to May) could induce a bias estimation.
    Effects of different irrigation treatments on photosynthesis of Tieguanyin tea plants.
    KE Yu-qin; ZHUANG Chong-guang; HE Hua-qin; WANG Li; HAN Guo-qiang; CHEN Ming; YE Jun-hua
    2008, 19(10):  2132-2136 . 
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    By using chlorophyll fluorescence kinetics technique, the effects of different irrigation intervals, i.e., 5 d (T1), 10 d (T2), 15 d (T3), 20 d (T4), and 25 d (T5), on the photosynthesis of 2-year Tieguanyin tea plants were investigated in the field, with no irrigation as the control. The results showed that the leaf water potential and chlorophyll content decreased with increasing irrigation interval, while the net photosynthesis (Pn) increased first and decreased then, reaching its highest value (15.55 μmol·m-2·s-1) in treatment T2. The ratio of the variable to maximal fluorescence (Fv/Fm), the variable fluorescence quenching (ΔFv), and the variable fluorescence quenching rate (ΔFv/Fo) all got the highest in treatment T2, being 0.844, 342.5, and 4.03, respectively. The initial fluorescence (Fo) decreased with increasing irrigation interval, while a reverse changing trend of Fo was observed in the control, demonstrating that PSⅡ reaction center was damaged by drought stress. In conclusion, irrigating per 10 d was favorable to the photosynthetic electron transport and CO2 assimilation of the tea plants, which would enhance their photosynthesis efficiency.
    Inhibition effects of salt stress on photosynthetic activity of Rumex K-1.
    FANG Peng1,2; REN Li-li3; ZHANG Li-tao1; GAO Hui-yuan1
    2008, 19(10):  2137-2142 . 
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    With Rumex K-1 seedlings as test materials, this paper studied the effects of different concentration (100 -300 mmol·L-1) NaCl and KCl on their leaf photosynthetic activity and osmotic adjustment. The results showed that at the concentration of 200 mmol·L-1, NaCl had greater inhibition effect on the leaf photosynthetic activity than KCl, but at 300 mmol·L-1, the inhibition effect of KCl was much greater than NaCl. After treated with 300 mmol·L-1 of KCl and NaCl, the leaf water potential was -0.93 MPa and -1.05 MPa, and the osmotic potential was -1.43 MPa and -1.10 MPa, respectively, indicating that the increased damage caused by 300 mmol·L-1 of KCl was not from osmotic stress. Under the stress of 300 mmol KCl·L-1, the leaf Na+ concentration decreased by 88.6%, compared with the control, while the supplement of 25mmol NaCl·L-1 could obviously alleviate the damage of KCl on leaf photosynthesis, which proved that the deficit of Na+ and the accumulation of K+ in Rumex K-1 leaves could be responsible to the enhanced damage caused by 300 mmol·L-1 of KCl.
    Effects of NaCl on the growth and alkaloid content of Catharanthus roseus seedlings.
    WANG Jing-yan; LIU Zhao-pu; LIU Ling; LIU Chong
    2008, 19(10):  2143-2148 . 
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    Catharanthus roseus seedlings were grown in 1/2 Hoagland solution containing 0250 mmol·L-1of NaCl, and their fresh and dry mass, malondialdehyde (MDA) and chlorophyll contents, tryptophan decarboxylase (TDC) and peroxidase (POD) activities, and vindoline, catharanthine, vincristine and vinblastine contents were measured after 7 days. The results showed that NaCl markedly decreased the fresh and dry mass but increased the MDA content. The chlorophyll content had no difference with the control when the concentration of NaCl was 50 mmol·L-1, but decreased with increasing NaCl concentration when the NaCl concentration was above 50 mmol·L-1. There was a significant enhancement of POD activity under NaCl stress. The TDC activity was the highest when the concentration of NaCl was 50 mmol·L-1, but decreased with increasing NaCl concentration. The vindoline, catharanthine, vincristine, and vinblastine contents were the highest under 50 mmol·L-1NaCl stress, with the values being 4.61, 3.56, 1.19, and 2.95 mg·g-1, respectively, and significant higher than the control and other treatments. Salt stress could restrain the growth of C. roseus seedlings, but promote the metabolism of alkaloid and increase the alkaloid content. 50 mmol·L-1 of NaCl had the greatest promotion effect on the alkaloid content of C. roseus eedlings.
    Effects of high temperature stress on photosynthesis and chlorophyll fluorescence of cut flower chrysanthemum (Dendranthema grandiflora ‘Jinba’).
    SUN Xian-zhi; ZHENG Cheng-shu; WANG Xiu-feng
    2008, 19(10):  2149-2154 . 
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    Cut flower chrysanthemum (Dendranthema grandiflora ‘Jinba’) plants were treated with 40 ℃/35 ℃ or 33 ℃/28 ℃ (day/night) for 11 days and then transferred to 23 ℃/18 ℃ for 5 days to study the changes in their photosynthesis and fluorescence parameters under high temperature stress and normal temperature recovery. The results showed that on the 5th day of 33 ℃/28 ℃ treatment, net photosynthesis (Pn) decreased gradually and stomatal conductance (Gs) decreased evidently; while after recovery for 5 days, both Pn and Gs resumed to 80% of the control. At 40 ℃/35 ℃,Pn and Gs decreased dramatically. The increase of intercellular CO2 concentration (Ci) at the early stage under given high temperatures showed that the photosynthesis inhibition by high temperature stress was resulted from non-stomatal limitations. However, 9 days later, stomatal limitation became the mainly cause of photosynthesis inhibition. The intrinsic photochemical efficiency (Fv/Fm), quantum yield of PSⅡ(ΦPSⅡ), and the efficiency of excitation energy capture by open PSⅡ reaction center（Fv′/Fm′） at 33 ℃/28 ℃ and 40 ℃/35 ℃ all decreased, with antenna heat dissipation increased, indicating that reaction center was protected by decreased light capture and efficiency of electron transfer through PSⅡ. The photochemical quenching (qP) at 33 ℃/28 ℃ descended first and turned to rise then, suggesting that the electron transfer was firstly restrained by the stress. Contrastively, qP rose continuously at 40 ℃/35 ℃, indicating that oxygen-evolving complex (OEC) was the location in chrysanthemum photosynthesis apparatus most sensitive to extreme high tempe rature.
    Effects of inoculation with arbuscular mycorrhizal fungi on AlPO4 uptake by Poncirus trifoliata.
    LIU Jin-fa; XIA Ren-xue; WANG Ming-yuan; WANG Peng; RAN Qing-qing;LUO Yuan
    2008, 19(10):  2155-2160 . 
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    With sand culture in greenhouse, this paper studied the effects of inoculation with arbuscular mycorrhizal (AM) fungi Glomus mosseae and G. versiforme on the utilization of insoluble phosphate AlPO4 (Al-P) by trifoliate orange (Poncirus trifoliata) seedlings. The results indicated that inoculation with AM fungi notably increased the dry matter, P content, and P absorption rate of P.trifoliata. The contribution of mycorrhiza, P uptake by plant and AM fungi, and the contribution of AM fungi in P uptake by P. trifoliata increased greatly with increasing Al-P level in the medium. Inoculation with AM fungi greatly increased the excretion of phosphatase, especially acid- and neutral phosphatase, from plant root and hyphae, but the excretion amount decreased with increasing Al-P level. The contribution of the fungi in P uptake by P. trifoliata was significantly positively correlated with the amounts of acid-, neutral-, alkaline-, and total phosphatase.
    Simulation on the seasonal growth patterns of grassland plant communities in northern China.
    ZHANG Li1,2; ZHENG Yuan-run1
    2008, 19(10):  2161-2167 . 
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    Soil moisture is the key factor limiting the productivity of grassland in northern China ranging from arid to subhumid arid regions. In this paper, the seasonal and annual growth, foliage projective cover (FPC), evaporative coefficient (k), and net primary productivity (NPP) of 7 types of grasslands in North China were simulated by using a simple model based on well established ecological processes of water balance and climatic data collected at 460 sites over 40 years. The observed NPPs were used to validate the model, and the simulated NPPs were in high agreement with the observed NPPs. The simulated k, NPP, and FPC deceased from east to west in temperate grasslands, and decreased from southeast to northwest in Qinghai-Tibet Plateau, reflecting the moisture gradient in northern China. Alpine meadow had the highest k, NPP, and FPC in the 7 types of grasslands, alpine steppe had the second highest FPC but with a NPP similar to that of temperate steppe, and the three simulated parameters of temperate desert were the smallest. The simulated results suggested that the livestock density should be lower than 5.2, 2.3, 3.6, 2.1, 1.0, 0.6, and 0.2 sheep unit·hm-2, while the coverage of rehabilitated vegetation should be about 93%, 79%, 56%, 50%, 44%, 38%, and 37% in alpine meadow, alpine steppe, temperate meadow steppe, temperate steppe, temperate desert steppe, temperate steppe desert, and temperate desert, respectively.
    Net primary productivity of Leymus chinensis steppe in Xilin River basin of Inner Mongolia and its responses to global climate change.
    YUAN Fei1,3; HAN Xing-guo2; GE Jian-ping3; WU Jian-guo1,2,3,4
    2008, 19(10):  2168-2176 . 
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    CENTURY model was utilized to simulate the annual aboveground net primary production (ANPP) of Leymus chinensis steppe, a dominant community type in Xilin River basin of Inner Mongolia steppe region. The results showed that the model performed reasonably well in predicting the dynamics of the ANPP. The scenario-based simulations indicated that though the variations of air temperature and precipitation due to global climate change as well as the elevated CO2 would significantly affect the dynamics of the ANPP, precipitation was the key affecting factor. Several GCM models had predicted that the precipitation in this region would decrease in the future, and consequently, it was likely that the ANPP would also decrease. Nevertheless, the simulation results showed that while the ANPP decreased in most climate change scenarios, it might also increase in the following climate change scenarios: 1) if the atmospheric CO2 concentration was doubled, air temperature was increased by 2 ℃, and precipitation was kept unchanged or increased by 10%-20%, and 2) if the atmospheric CO2 concentration was kept unchanged, air temperature was increased by 2 ℃, and precipitation was increased by 20%. Overall, it was evident that climate change would have significant effects on the steppe in Xilin River basin of Inner Mongolia.
    Micro-community characteristics of vegetations in blowouts and depositional areas of Hulunbuir grassland, Inner Mongolia.
    MAN Liang1,2; HASI Eerdun1; ZHANG Ping1; YAN Xu1; XIA Xian-dong1
    2008, 19(10):  2177-2181 . 
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    By using traditional sampling methods, the micro-communities of vegetations in fixed, semi-bare, and bare blowouts of Hulunbuir grassland were investigated, and the investigation data were statistical analyzed. The results showed that the vegetation coverage decreased in the order of fixed blowout, semi-bare blowout, and bare blowout, and was lower than that of the primary vegetation Form. Stipa grandis. Potentilla acaulis and Kengia squarrosa were the dominant species in fixed blowout, with the coverage being 5%; while P. acaulis and Carex sp. were the dominant species in semi-bare blowout, with the coverage being 2%. The dominant species in depositional areas of semi-bare blowout were P. acaulis, K. squarrosa, Agropyron cristatum, and Thymus mongolicus, and the coverage was 4%. The dominant species on the southwest slope of bare blowout was Agriophyllum pungens. The middle depositional area of bare blowout was also occupied by A. pungens (coverage 4.7%), and the edge of it was dominated by A. cristatum (coverage 2.7%), Carex sp. (coverage 2.6%), and T. mongolicus (coverage 1.7%) from the edge of the depositional area to primary grassland. The mean species importance value in fixed, semi-bare, and bare blowouts was 12.64%, 13.38%, and 20.08%, while that in the depositional area of semi-bare blowout and in the middle and edge of bare blowout was 12.55%, 40.18%, and 11.15%, respectively.
    Assessment on vegetation restoration capacity of several grassland ecosystems under destroyed disturbance in permafrost regions of Qinghai-Tibet Plateau.
    LI Dong-ming1,2; GUO Zheng-gang1; AN Li-zhe2
    2008, 19(10):  2182-2188 . 
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    Vegetation restoration capacity of disturbed grassland ecosystem is one of the important components in assessing the influence of human engineering activities on the grassland ecosystems in permafrost region of Qinghai-Tibet Plateau. After comparing the features of vegetation communities, plant species diversity, grassland primary productivity, and economic group between disturbed and undisturbed communities, the comprehensive vegetation restoration capacity of several grassland communities under destroyed disturbance was assessed by using comprehensive assessment index. The results showed that the restoration of cover and community composition was obvious after 26 years natural restoration, being better for alpine steppes than for alpine meadows. However, the cover of disturbed communities was less than that of undisturbed communities. The restoration of plant species diversity in Stipa purpurea steppe was better than that in other grassland types. The biomass of standing plants restored from 0 to 148.8-489.6 g·m-2, and that of Kobresia tibetica meadow was the highest (489.6 g·m-2). The palatable plants of disturbed communities were lower than those of undisturbed communities except for K. tibetica meadow, in which, the palatable plants were not changeable between disturbed and undisturbed communities. The comprehensive vegetation restoration capacity of alpine steppes was better than that of alpine meadows.
    Diurnal dynamics of photosynthetic characteristics of alfalfa on Kerqin sandy land.
    XU Li-jun1,2; WANG Bo3; SUN Qi-zhong2
    2008, 19(10):  2189-2193 . 
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    By using a Li-6400 portable photosynthesis system, the diurnal dynamics of the photosynthetic characteristics of three alfalfa varieties Medicago sativa L. cv. Aohan, M. sativa L. cv. Rangelander, and M. sativa L. cv. Algonquin were studied. The results showed that for the test alfalfa varieties, the diurnal variation curves of their Pn, Tr, and WUE were not all presented double-peak. For Aohan and Algonquin, the maximum Pn and Tr occurred at 9:00-11:00; while for Rangelander, they appeared at 11:00. The minimum Pn and Tr of the three varieties all appeared at 7:00 and 19:00. The maximum WUE of Rangelander and Algonquin appeared at 7:00 and that of Aohan was at 9:00, and the minimum WUE of the three varieties all appeared at 15:00-17:00. Comprehensive analysis on the photosynthetic performance indices Pn, Tr, and WUE indicated that 2 years old alfalfa was in the best state, followed by 1 year old, and 4 years old. Correlation analysis showed that air temperature (Ta) was the main environmental factor affecting Pn and Tr, followed by water vapor pressure deficit (VPD) and relative humidity (RH).
    Growth responses of belowground modules of Carex lasiocarpa to different water regimes and water experiences.
    WANG Li1,2; SONG Chang-chun1; HU Jin-ming3; YANG Tao1,2
    2008, 19(10):  2194-2200 . 
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    With seedling’s transplanting experiment under different water levels, this paper studied the growth responses of belowground modules of Carex lasiocarpa to various water regimes and water experiences in Sanjiang Plain. The results showed that the belowground modules of C. lasiocarpa had significantly different responses to water regimes. At thriving stage, the length of rhizome and adventitious root decreased with increasing water level, and until later growth stage, the maximal value still appeared under drought condition. However, under dry-wet alternate condition, the length of rhizome and adventitious root increased most from thriving stage to the end, indicating that stable and lower water level could improve the growth of rhizome and adventitious root. The biomass of rhizome, adventitious root, and belowground part were maximal under dry-wet alternate condition at both growth stages. For those with different water experiences, the ones undergoing alternate condition in early growth season and then drought had maximal rhizome biomass, and the others under sustained alternate condition had maximal adventitious root and belowground biomass. More biomass was distributed to rhizome in the later growth season under various water regimes. The percentage of rhizome in total biomass was significantly higher under drought condition than under other water conditions through the growth season. Besides, C. lasiocarpa grew slowly when submerged, but could recover through rhizomatic reproduction after the stress disappeared.
    Accuracy of winter wheat identification based on multi-temporal CBERS-02 images.
    QI La1; ZHAO Chun-jiang2; LI Cun-jun2; LIU Liang-yun2; TAN Chang-wei3; HUANG Wen-jiang2
    2008, 19(10):  2201-2208 . 
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    Chinese-Brazi1 Earth Resources Satellite No.2 (CBERS-02) has good spatial resolution and abundant spectral information, and a strong ability in detecting vegetation. Based on five CBERS-02 images in winter wheat growth season, the spectral distance between winter wheat and other ground targets was calculated, and then, winter wheat was classified from each individual image or their combinations by using supervised classification. The train and validation samples were derived from high resolution Aerial Images and SPOT5 images. The accuracies and analyses were evaluated for CBERS-02 images at early growth stages, and the results were compared to those of TM images acquired in the same phenological calendars. The results showed that temporal information was the main factor affecting the classification accuracy in winter wheat, but the characteristics of different sensors could affect the classification accuracy. The multi-temporal images could improve the classification accuracy, compared with the results derived from signal stage, with the producer accuracy of optimum periods combination improved 20.0% and user accuracy improved 7.83%. Compared with TM sensor, the classification accuracy from CBERS-02 was a little lower.
    Spatiotemporal variation of root systems of cytoplasmic male sterile maize (Zea may L.) and its homotype fertile lines.
    LI Cong-feng; LIU Peng; WANG Kong-jun， DONG Shu-ting; ZHANG Ji-wang
    2008, 19(10):  2209-2214 . 
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    Maize cytoplasmic male sterile (CMS) lines and their homotype fertile lines were cultivated on soil column to study the differences of their root traits at different growth stages after anthesis. The results indicated that CMS lines had stronger ability of dry matter accumulation in their aboveground part, their grain yield was significantly higher than that of homotype fertile lines (P<0.05), and their root dry mass was higher. In addition, the ratio of their root to canopy had a similar variation trend as root dry mass. The root mass of CMS lines in 0-20 cm and 20-40 cm soil layers was higher than that of homotype fertile lines, and the superiority was more obvious in 40-80 cm soil layer. Compared with homotype fertile lines, CMS lines had significantly higher root activity in 0-20 cm and 20-40 cm soil layers (P<0.05), and significantly higher root SOD activity and soluble protein content (P<0.05) in 40-80 cm soil layer. The root activity and root SOD activity and soluble protein content of CMS lines were significantly higher than those of their homotype fertile lines (P<0.05) at late growth stage. In conclusion, CMS lines had the characteristics of larger root quantity in deeper soil layers and higher root physiological activity at late growth stage, which could prolong the functional period of root and postpone the process of senescence, possibly being one of the important reasons of the high grain yield of CMS lines.
    Effects of nitrogen application rate on spatiotemporal variability of biomass accumulation of cotton’s fruiting branch at flower and boll stage.
    YANG Zhi-bin; CHEN Bing-lin; ZHOU Zhi-guo
    2008, 19(10):  2215-2220 . 
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    Field experiments were conducted in Anyang and Nanjing, the typical representatives of ecological regions in the Yellow River Valley and the lower reaches of Yangtze River Valley in China, to quantitatively analyze the spatiotemporal variability of biomass accumulation of the fruiting branch of cotton variety Nucotn 33B at its flower and boll stage under effects of 0, 120, 240, 360, and 480 kg N·hm-2 (marked as N0, N1, N2, N3, and N4, respectively). The results indicated that both in Nanjing and in Anyang, the temporal variability of biomass accumulation of vegetative and reproductive organs at different positions of fruiting branch could be described by Logistic equation, but the spatial variability was obviously different. Under the nitrogen application rate of 360 kg·hm-2 in Anyang and of 240 kg·hm-2 in Nanjing, the biomass accumulation had the characteristics of earlier starting date, shorter duration, and maximal speed of rapid increase. These nitrogen application rates could accelerate the biomass accumulation to benefit the high lint yield and fiber quality, while excess or deficient nitrogen supply was disadvantageous to the biomass accumulation of fruiting branch. Therefore, it could be possible to apply appropriate amount of nitrogen to regulate the growth eigenvalues of different positions fruiting branch at its speed growth stage to obtain high lint yield and fiber quality.
    Chemical forms and subcellular and molecular distribution of Cd in two Cd-accumulation rice genotypes.
    YU Hui1; YANG Zhong-yi2; YANG Zhi-jian1; XIANG Zuo-xiang1
    2008, 19(10):  2221-2226 . 
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    A hydroponic experiment combined with subcellular fractionation and gel filtration was carried out to study the chemical forms and subcellular and molecular distribution of Cd in rice roots and leaves, and to compare the differences between the rice varieties ‘Guangyuanzhan No.3’ (a low-Cd accumulation genotype) and ‘Zhenguiai’ (a high-Cd accumulation genotype). The results showed that with increasing concentration of Cd in the medium, the Cd content in all fractions of rice roots and leaves increased significantly, and most of Cd accumulated in FⅠ(cell wall) and FⅢ(soluble substance). Compared with ‘Guangyuanzhan No.3’, ‘Zhenguiai’ had a significantly higher soluble fraction of Cd in its roots and leaves. The greatest amount of Cd in roots and leaves was in the extraction solution of 1 mol·L-1 NaCl, followed by in 2% HAC, and 0.6 mol·L-1 HCl. In comparison with ‘Guangyuanzhan No.3’, ‘Zhenguiai’ had a higher proportion of d-H2O and 80% ethanol extractable-Cd, the more mobile form of Cd. In the two rice varieties, the soluble Cd eluted followed the same pattern as the soluble protein in the sample medium, and the majority of soluble Cd was bounded to phytochelatins (PCs) or low molecular weight components. However, the Cd-PCs content in ‘Guangyuanzhan No.3’ roots was much lower than that in ‘Zhenguiai’ roots, which could possibly result in a lower Cd mobility in roots and less Cd translocation from root to aboveground part.
    Effects of simulated acid rain on leaf photosynthate, growth, and yield of wheat.
    MAI Bo-ru1; ZHENG You-fei1; LIANG Jun1; LIU Xia2; LI Lu1; ZHONG Yan-chuan1
    2008, 19(10):  2227-2233 . 
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    With winter wheat variety Yamgmai 12 as test object, a field experiment was conducted to study the stress of simulated acid rain on its growth and development. The results showed that simulated acid rain had considerable effect on wheat growth and yield. When the pH of acid rain was ≤3.5, the growth of leaf area as well as the mass of fresh leaf per unit area declined greatly, and the yield was significantly lower than CK. When pH was ≤2.5, the plant height was obviously lowered, and the visible injury on leaf surface was observed. Under acid rain stress, the contents of leaf chlorophyll a, chlorophyll b, and carotenoid, especially chlorophyll a, decreased obviously. Acid rain also suppressed the synthesis of soluble sugar and reduced sugar, and the suppression was stronger at pH≤3.5, and became much stronger with increasing acidity. The total free amino acid and soluble protein contents in leaves decreased with increasing acidity, and were significantly lower than CK when the pH was ≤3.5 and ≤4.5, respectively.
    Changes of microbial biomass carbon and enzyme activities in rice-barnyard grass coexisted soils.
    LI Hai-bo1，2; KONG Chui-hua1
    2008, 19(10):  2234-2238 . 
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    Taking barnyard grass (Echinochloa crus-galli), allelopathic rice (Oryza sativa) PI312777, and non-allelopathic rice Liaojing-9 as test materials, this paper studied the changes of microbial biomass C and of dehydrogenase, urease and invertase activities in soils under 1∶1 rice-barnyard grass coexistence. The results showed that with the coexistence of barnyard grass, the microbial biomass C in rhizosphere soil of PI312777 was decreased by 50.52% (P<0.01), while that in inter-row soil was increased. The microbial biomass C in rhizosphere soil of Liaojing-9 was also decreased by 38.99%(P<0.01), but no significant difference was observed in inter-row soil. The dehydrogenase activity in rhizosphere soils of the two rice varieties were decreased by 20% or more (P<0.05), but the urease and invertase activities in rhizosphere soil of PI312777 were significantly stimulated (P<0.01). The invertase activity in rhizosphere soil of Liaojing-9 was inhibited by coexisting barnyard grass, but urease activity had less change. As a result, the allelopathic traits of rice variety led to a significant decrease of microbial biomass C and an increase of urease and invertase activities in rhizosphere soil under barnyard grass coexistence, implying that soil microbial biomass and enzymes might play essential roles in species interactions between rice and barnyard grass, and allelopathic rice had its advantage in resistance to barnyard grass.
    Assessment on the availability of nitrogen fertilization in improving carbon sequestration potential of China’s cropland soil.
    LU Fei, WANG Xiao-ke;HAN Bing; OUYANG Zhi-yun; DUAN Xiao-nan;ZHENG Hua
    2008, 19(10):  2239-2250 . 
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    With reference to the situation of nitrogen fertilization in 2003 and the recommendations from agricultural experts on fertilization to different crops, two scenarios, namely, ‘current situation’ and ‘fertilization as recommended’, were set for estimating the current and potential carbon sequestration of China’s cropland soil under nitrogen fertilization. After collecting and analyzing the typical data from the long-term agricultural experiment stations all over China, and based on the recent studies of soil organic matter and nutrient dynamics, we plotted China into four agricultural regions, and estimated the carbon sequestration rate and potential of cropland soil under the two scenarios in each province of China. Meanwhile, with the data concerning fossil fuel consumption for fertilizer production and nitrogen fertilization, the greenhouse gas leakage caused by nitrogen fertilizer production and application was estimated with the help of the parameters given by domestic studies and IPCC. We further proposed that the available carbon sequestration potential of cropland soil could be taken as the criterion of the validity and availability of carbon sequestration measures. The results showed that the application of synthetic nitrogen fertilizer could bring about a carbon sequestration potential of 21.9 Tg C·a-1 in current situation, and 30.2 Tg C·a-1 with fertilization as recommended. However, under the two scenarios, the greenhouse gas leakage caused by fertilizer production and application would reach 72.9 Tg C·a-1 and 91.4 Tg C·a-1, and thus, the actual available carbon sequestration potential would be -51.0 Tg C·a-1 and -61.1 Tg C·a-1,respectively. The situation was even worse under the ‘fertilization as recommended’ scenario, because the increase in the amount of nitrogen fertilization would lead to 10.1 Tg C·a-1 or more net greenhouse gas emission. All these results indicated that the application of synthetic nitrogen fertilizer could not be taken as a feasible measure for the carbon sequestration of cropland soil in China. Since synthetic fertilizer application is the basic guarantee of China’s crop production, it was suggested to increase the efficiency of synthetic nitrogen fertilizer, and at the same time, to cut down the synthetic nitrogen fertilizer production and its application on the premise that the crop yield should be ensured.
    Dynamic changes of ecosystem service value in Pinggu District of Beijing.
    LI Bo; SONG Xiao-yuan; XIE Hua-lin; HAO Li-xia; ZHANG Shu-hui
    2008, 19(10):  2251-2258 . 
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    Based on the land use/cover data of 1995 and 2004, and by using ecosystem service value per unit area of different terrestrial ecosystem types in China, the dynamic changes of ecosystem service value in Pinggu District of Beijing were analyzed. The results showed that the total ecosystem service value of Pinggu District was decreased from 3.291×109 yuan in 1995 to 3.044×109 yuan in 2004, with a change rate of -7.50%. The decrease in the areas of farmland and waters was the primary cause of the loss in ecosystem service function. Aquatic ecosystem had the highest ecological service value per unit area, while forest ecosystem gave the greatest contribution to the total ecosystem service value. The dynamic changes of the ecological service value revealed the conspicuously irrationality of land use structure in the District. The area proportions of forestland, farmland, and waters should be increased, and the conversion from farmland to constructive land should be controlled strictly. As the emergency water source and eco-conservation division of Beijing City, Pinggu District should improve its eco-environment protection and economic development to support the ecological and drinking water source securities of the Capital Beijing.
    Emergy analysis of agro-ecolomic system in Shanxi Province.
    WANG Run-ping1,2; RONG Xiang-min1
    2008, 19(10):  2259-2264 . 
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    By the methods of emergy, this paper studied the input and output, working efficiency, and environmental loading of the agro-ecolomic system in Shanxi Province in 2005. The results showed that in 2005, the agro-ecolomic system in Shanxi still stayed in the period of traditional agriculture, which mainly depended on manpower and environmental resources. The emergy investment ratio (EIR) was 1.07, emergy yield ratio (EYR) was 0.99, and environmental loading ratio (ELR) was 6.55. In the structural adjustment of agriculture, stockbreeding had made great strides forward, but grain crops other than rice and wheat, vegetables, and fruits still had smaller emergy yield and were far from becoming dominant industry. The efficiency of the agro-ecolomic system was lower, and its environmental loading press was bigger. For the future, the surplus labors in agriculture in Shanxi should be shifted continually to other industries, and the high quality emergy such as agricultural science and technology should be increased to improve the use efficiency of environmental resources and the input and output of the system emergy.
    Effects of leachate-loading and irrigation depth on N2O and CO2 emissions from leachate-irrigated soil.
    SHAO Li-ming1,2,3; KONG Xiang-rui1,2,3; ZHANG Hou-hu1,2,3; HE Pin-jing1,2,3
    2008, 19(10):  2265-2270 . 
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    By using prefabricated probe and static chamber, the N2O concentration at different depths along the soil columns irrigated by landfill leachate as well as the N2O and CO2 fluxes were determined. The results showed that leachate irrigation could promote the N2O emission. Within the first 24 hours after irrigation, the N2O fluxes from the soil columns were significantly correlated with the N2O concentrations in the columns at the depths of 10 cm (r=0.944, P<0.01), 20 cm (r=0.799, P<0.01), 30 cm (r=0.666, P<0.01), and 40 cm (r=0.482, P<0.05), and the correlation decreased along the depths. Landfill leachate irrigation also promoted the CO2 emission from the soil columns. There was no significant correlation between the emissions of N2O and CO2 (P>0.05). The irrigation loading of landfill leachate had a predominant effect on the total greenhouse gas emissions (including N2O and CO2 fluxes, based on CO2-equivalent emissions). When the irrigation loading was 6 mm·d-1, the total greenhouse gas emissions from the soil columns were 2 times higher than those when the irrigation loading was 2 mm·d-1. 47% of the total greenhouse gas emissions were reduced from the soil columns when the leachate irrigation depth was at 20 cm, compared with the depth being at 10 cm. Within the 14 days under leachate irrigation, 57.0%-91.0% of the total greenhouse gas emissions were originated from N2O emission.
    Application of frost number model in Northeast China pepmafrost regionalization
    LÜ Jiu-jun1,2; LI Xiu-zhen1; HU Yuan-man1; WANG Xian-wei1,2; SUN Ju1,2
    2008, 19(10):  2271-2276 . 
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    Based on the 1981-2000 observation data of climate factors and snow depth in Northeast China, frost number model was applied to approach its applicability in the regionalization of the permafrost in this area. The results indicated that the permafrost in Northeast China was dominated by discontinuous permafrost, including large piece permafrost, large piece and island-like permafrost, and alpine permafrost. The comparison of permafrost regionalization maps in different periods showed that the simulation results of the model could reflect the recent distribution status of the permafrost in Northeast China. The southern boundary of the discontinuous permafrost could reach to Aershan Mountain region, and the other alpine permafrost as well as the permafrost of Yichun in Xiaoxing’an Mountains could be also distinguished by the model.
    Simulation model on the formation of greenhouse sweet pepper leaf area index.
    DIAO Ming1,2; DAI Jian-feng1; LUO Wei-hong1,3; YUAN Chang-mei1; BU Chong-xing3; XIAN Kai-mei2; ZHANG Sheng-fei1; XU Rui1
    2008, 19(10):  2277-2283 . 
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    Leaf area index (LAI) is one of the most important crop parameters in photosynthesis- driving crop growth simulation model and canopy evapotranspiration simulation model, while air temperature and radiation are the important climate factors affecting crop leaf growth. In this paper, experiments with different sweet pepper (Capsicum annuum L.) cultivars and sowing dates were conducted in greenhouse to quantitatively analyze the relationships of the number of unfolding leaves per plant, the number of old leaves removed per plant, and the length of each leaf with air temperature and radiation. Based on these quantitative relationships, a leaf area simulation model for greenhouse sweet pepper was developed, and the independent experimental data were used to validate the model. The results showed that the number of unfolding leaves per plant was a positive exponential function of the product of thermal effectiveness and PAR (TEP) accumulated after emergence, and the length of each leaf was a negative exponential function of the TEP accumulated after emergence. The coefficient of determination (R2) and the root mean squared error (RMSE) between simulated and measured leaf number, leaf length, and LAI were 0.94, 0.89, and 0.93, and 3.4, 2.15, and 0.15, respectively. The model could use air temperature, radiation, planting density, and emergence date to satisfactorily predict the LAI of greenhouse sweet pepper, and supply required LAI information for the sweet pepper growth and canopy evapotranspiration simulation models.
    Characteristics of ichthyoplankton assemblages in Yangtze Estuary and adjacent waters in spring.
    LIU Shu-de1,2; XIAN Wei-wei1; LIU Dong1
    2008, 19(10):  2284-2292 . 
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    Based on the investigation data of ichthyoplankton assemblages and environmental factors in Yangtze Estuary and adjacent waters in May 1999 and 2001, the characteristics of ichthyoplankton assemblages in these areas in spring were studied by using TWINSPAN (two-way indicator species analysis) and CCA (canonical correspondence analysis). A total of 11 540 ichthyoplankton individuals were taxonomically identified, belonging to 11 orders, 18 families and 32 species, of which, Coilia mystus, Engraulis japonicus, Chaeturichthys hexanema, Allanetta bleekeri, and Trachidermis fasciatus were the dominant species. The ichthyoplankton communities were classified into three assemblages by using TWINSPAN, i.e., estuarine assemblage dominated by C. mystus, coastal assemblage dominated by A. bleekeri and T. fasciatus; and shelf assemblage featured by E. japonicus and C. hexanema. The CCA ordination of the interrelations among the three assemblages and their correlations to the environmental variables revealed that salinity, depth, dissolved oxygen, and total suspended particulate matter were the major factors affecting the ichthyoplankton assemblages in the study areas.
    Simulation of algae bloom under different flow velocity.
    HUANG Yu-ling1; LIU De-fu1; CHEN Ming-xi2
    2008, 19(10):  2293-2298 . 
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    The construction of a river-type reservoir will normally cause a change of hydrodynamic condition and a decrease of flow velocity in branch bays, leading to the formation of algae bloom when appropriate environmental conditions and sufficient nutrient supply are encountered, and thereby, causing the deterioration of fluvial ecosystem therein. To investigate the effects of hydrodynamic conditions on algae bloom, flow velocity was taken as the characteristic parameter, and controlled differently in the closed and recurrent models under identical environmental and nutrient conditions. The results showed that the increase of the flow velocity in a range of <0.4 m·s-1 would accelerate the growth of algae and the occurrence of bloom. Under the conditions of different flow velocity, the growth of algae was similar to the common process of other microorganisms, namely, lag phase firstly,exponential phase secondly, stationary phase thirdly, and decline phase lastly. Accordingly, the outbreak peak and regression floor of the algae bloom would occur. Therefore, the increase of flow velocity in a range of <0.4 m·s-1 would not inhibit the growth of algae and the occurrence of bloom. The effective characteristic parameter of the hydrodynamic conditions would be studied in depth in future.
    Distribution characteristics of benthic algae in intertidal zone of Ma’an Archipelago of Zhejiang Province.
    ZHANG Shou-yu; LIANG Jun; WANG Zhen-hua; WANG Kai
    2008, 19(10):  2299-2307 . 
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    Based on the survey of benthic algae in the intertidal zone of Ma’an Archipelago from March to July 2007, the algal species composition, distribution, and temperature feature were studied. The dominant algal species in the study area were preliminarily analyzed by using similarity indices (Sc) and index of relative importance (IRIc). A total of 31 species sampled in sublittoral area were identified, among which, 7 species of 5 genera belonged to Chlorophyta, 8 species of 5 genera belonged to Phaeophyta, and 16 species of 14 genera belonged to Rhodophyta. Topical and selective distribution species influenced by wave and tide were identified in the intertidal zone. Ulva pertusa and Sargassum thunbergii were found in all survey area. Rhodophyta was the dominant species, with the occurring frequency being up to 61.1%, and Chlorophyta showed quite uniformed horizontal distribution. In addition, 81% of sampled species were from low-tide zone, and some were extended from mid-tide zone to low-tide zone. The composition comparability between mid-tide and low-tide species was 0.47, and the convergence effect in mid-tide and low-tide zone was higher than that in high-tide and mid-tide zone. The sublittoral area of Ma’an Archipelago showed obvious vertical zoning character, with temperate species being absolute abundant, and the warm-water species dominant. The marine floral texture of Ma’an Archipelago belongs to warm temperate-subtropical transitional marine flora.
    Silviculture of poplar plantation in China: A review.
    FANG Sheng-zuo
    2008, 19(10):  2308-2316 . 
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    There are more than 7.0 million hm2 of poplar plantation in China, ranking top one in the world. To meet the needs of a growing world for social-economic development, environmental improvement, and sustainable development through poplar plantation establishment is a main research interest in the globe. This paper introduced the regionalizing cultivation, key planting clones, and productivities of poplar plantations in China, and summarized the recent 10 years research progress in China in the site quality evaluation, seedling propagation techniques, management patterns, mixed plantation establishment, agroforestry management system, water and nutrient management techniques, site productivity maintenance, and ecological functions of poplar plantation. The potential productivity, general allocation, oriented silviculture, and environmental function study of poplar plantation were also discussed and prospected. The contents of this paper would provide some references for the silviculture and sustainable management of poplar plantation in China.
    Toxicological effects of omethoate on leaf photosystem Ⅱ of cole.
    LI Wei-juan; GAO Zhi-kui; WANG Mei; CAO Yan-po; XUE Zhan-jun
    2008, 19(10):  2317-2321 . 
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    After spraying different concentrations of two brands pesticide omethoate on cole (Brassica campestris L.) leaves, the leaf chlorophyll a fluorescence transients were measured by a Plant Efficiency Analyzer (PEA), and the toxicological effects and rudimental dynamic courses of omethoate on the leaf photosystem Ⅱ (PSⅡ) were investigated by JIP-test. The results showed that after spraying omethoate except at the concentration of 0.50%, the maximal efficiency of photochemistry (Fv/Fm) did not have a remarkable change. However, with increasing omethoate concentration, the minimal fluorescence Fo, maximal fluorescence Fm, relative variable fluorescence at the J-step (VJ), and electron transport flux perreactive center in PSⅡ(ETo/RC) increased remarkably, but ψo, the efficiency that a trapped exciton in PS Ⅱ moved an electron into the electron transport chain beyond QA-, decreased remarkably. The test two brands of pesticide omethoate had almost alike effects on the PSⅡ of cole, and the residual effect of the pesticide was the strongest at the third day after spraying and petered out from the ninth to twelfth day. The main targets of omethoate on the PSⅡ of cole could be listed as promoting the reduction from QA to QA- (increasing of VJ) and the electron transmission from QA- to QB (increasing of ETo/RC).
    Allelopathic effects of Corallina pilulifera on red tide microalgae Heterosigma akashiwo.
    WANG Ren-jun1,2; TANG Xue-xi1; SUN Jun-hua2
    2008, 19(10):  2322-2326 . 
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    Different concentration methanol-, acetone-, ether-, and chloroform extracts of Corallina pilulifera were used to study their growth inhibitory effects on red tide microalgae Heterosigma akashiwo. The results showed that methanol extract at relatively higher concentrations had the highest growth inhibitory activity and killed all H. akashiwo cells, while the other three kinds of organic solvent extracts had no apparent inhibitory effects, suggesting that the growth inhibitory substances in C. pilulifera had relatively high polarity. The methanol extract was partitioned to petroleum ether phase, ethyl acetate phase, butanol phase, and distilled water phase by liquid-liquid fractionation, and the bioassays on the activity of each fraction were carried out on H. akashiwo. It was found that petroleum ether phase and ethyl acetate phase had strong algicidal effects on H. akashiwo, suggesting that the fatty acids in C. pilulifera tissues might be one of the main allelochemicals.