Table of Content

20 April 2009, Volume 18 Issue 2

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Influence of seasonal exclosure on plant and soil characteristics in typical steppe

SHAN Gui-lian, XU Zhu, NING Fa, JIAO Yan

2009, 18(2):  1-2. 

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Influence of seasonal exclosure on plant and soil characteristics in typical steppe

SHAN Gui-lian1,2, XU Zhu1,3, NING Fa1,2, JIAO Yan4

2009, 18(2):  3-10. 

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To discuss the restoration and reasonable utilization of degraded typical steppe, we chose natural grasslands which were exclosed during the growing season (Apr. to Sep.) for hay production then lightly grazed for the rest of the year. Continuously grazed land was chosen as the control to carry out comparative research on the influence of exclosure on plant and soil characteristics in typical degraded steppe. 1) Compared with continuous grazing, the above-ground biomass, coverage, density, under-ground biomass, litter biomass, and soil nutrients of degraded steppe increased after exclosure, while the soil bulk density, soil compaction, and coarse particle (＞0.25 mm) content decreased. The community structure and soil environment improved. The plants and soil formed a reciprocal interactions benign circulatory system, and the typical degraded grassland improved. 2) If the land was used continuously for hay production over many years then the process of recovery, productivity, coverage, density, and soil nutrients decreased, and the recovered grassland underwent a second retrogressive succession. 3) Seasonal exclosure could allow full use of grassland resources while ensuring that the degraded grassland recovered to some extent. Seasonal exclosure was a feasible grassland management method in pastoral areas, but some problems such as suitable exclosure season and reasonable mowing systems require further study.

Nitrogen mineralization in alfalfa stands

HAN Fang-hu, SHEN Yu-ying, WANG Xi, ZHOU Shao-ping, YANG Jing, GENG Li-ying

2009, 18(2):  11-17. 

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Greenhouse incubation experiments (12 weeks) were used to explore the influence of leaching initial mineral N, N fertilizers, and vegetation coverage on soil nitrogen mineralization of 5- and 9-year alfalfa (Medicago sativa) grasslands in the Qingyang Loess Plateau. The initial mineral N affected N mineralization and the net N mineralization rate increased by 0.05-0.07 mg/(kg·d) after the initial N was taken away. When N fertilization was adopted, the content of NO₃^--N in 5- and 9-year alfalfa grassland increased by 56 and 2 times respectively and net N mineralization rate increased by 200% in 5-year alfalfa grassland, but decreased by 62.5% in 9-year alfalfa grassland. Moreover, planting ryegrass (Lolium perenne) significantly affected N mineralization rate. For instance, net N mineralization rates in treatments with ryegrass were 12 to 18 times higher than in the control, and reached the highest values in the treatment N+Rye, where they were 18 to 25 times higher than in the controls. N mineralization potential in 9-year alfalfa stands was higher than in 5-year alfalfa. In grass-crop rotation systems on the Loess Plateau, succession plants should be sowed immediately after alfalfa is removed as dense plant coverage should reduce the risk of losing NO₃^-and thus enhance N availability in the rainy season.

Study on dynamics of aboveground biomass of Poa pratensis var. anceps Gaud. cv. Qinghai

LIU Wen-hui, ZHOU Qing-ping, YAN Hong-bo, LIANG Guo-ling

2009, 18(2):  18-24. 

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The accumulation dynamics of aboveground biomass of second year Poa pratensis var. anceps Gaud. cv. Qinghai was studied to understand the regulation of aboveground biomass accumulation in Alpine Regions of Qinghai province. The accumulation of stem (S), leaf (L), ear (E) and above ground biomass (Ba) of Poa all fitted to monofactorial cubic equations:S∧=21.04-2.12 d+0.10 d²-0.00062 d³,L∧=2.71+0.55 d+0.031 d²-0.00022 d³,E∧=3.17-1.27 d+0.070 d²-0.00051 d³,B∧a=26.92-2.84 d+0.20 d²-0.014 d³ respectively. From greening up to mid May, the Poa are in a nutritional growth period with tiller number, leaf area, and leaf number increasing rapidly. Mid May to mid June, the speed of above ground biomass accumulation of the Poa reached a climax with the highest stem, leaf, ear and above ground biomass of 6.836, 2.611, 2.409 and 11.876 g/(m²·d) respectively, and a stem/leaf ratio of 1∶1.61. Stem, leaf and above ground biomass of the Poa reached the maxima of 220.3, 151.7 and 406.1 g/m² respectively in mid July while ear accumulation reached a maximum of 92.3 g/m² in mid June. The relationship between total aboveground biomass (Ba) and plant height (H), leaf areas (LA), and stem number (N_T) can be represented by the equation B∧a=-4.44+6.44 H-58.88 LA-0.065 N_T+0.029 N_L, Plant height had the greatest direct effect on aboveground biomass accumulation while LA, NT, NL influenced aboveground biomass accumulation indirectly by affecting H.

Genetic variation of asexual reproduction characteristics of Cynodon dactylon

WANG Zhi-yong, LIU Jian-xiu, GUO Hai-lin

2009, 18(2):  25-32. 

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The study utilized 5 asexual reproductive traits (coefficient of expansion, level growth rate, vertical growth rate, the number of stolons per unit perimeter and the longest stolon) in order to make a preliminary assessment of genetic variation of asexual reproduction characteristics among the 33 different geographical distributions of wild Bermuda grass accessions from China and of 22 Bermuda grass cultivars from China, Australia, and the USA. There was a rich diversity in asexual reproduce of Bermuda grass from both China and overseas. The coefficient of variation was from 35.10％－82.31% (average 57.26%), and that of domestic accessions was higher than that of overseas cultivars. Vertical growth rates of domestic accessions and breeding materials were significantly lower than those of overseas cultivars. There were significant correlations (maximal correlation coefficient of 0.957) among asexual reproduction-related characteristics of Bermuda grass in both domestic and overseas cultivars with the exception of vertical growth rate. Based on five characteristics, SPSS 13.0 was used to divide Bermuda grass accessions into three asexual reproduction types: rapid propagation of stolons, intermediate and low-speed reproduction of stolons. The rapid propagation of stolons type are domestic accessions.

The effect of the population properties and stress-tolerance physiological characteristics of Zoysia grass under water stresses

WANG Qi, SUN Ji-xiong, AN Yuan

2009, 18(2):  33-39. 

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The population properties and stress-tolerance physiological characteristics of Zoysia japonica under 3 levels of water stress (none, light, and heavy), were studied in a field experiment. Zoysia growth was restricted by water stress, but it had a physiological and biochemical self-adjustment mechanism to reduce the damage caused by water stress. The density, height and biomass of Zoysia declined as the stress increased. Relative conductivity, proline content and MDA content of Zoysia leaves gradually increased in conditions of no water stress while the response trend of wavy change was found when both light and heavy water stress were present. Density, height and biomass of Zoysia increased during the recovery phase. Both density and biomass of Zoysia a grown in areas of water stress were higher than those in areas with no water stress, and the relative conductivity, proline content and MDA content of the Zoysia leaves were also lower. There were no significant differences in any of the indexes between light water stress and heavy water stress.

Research on fungal endophytes on Brachiaria spp. and their resistance to pathologenic fungi

HUANG dong-yi, HUANG Xiao-long, SEGENET kelemu

2009, 18(2):  39-45. 

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Plate confrontation test of 7 isolates of fungal endophytes on Brachiaria spp. against pathogenic fungi Drechslera sp. and Rhizoctonia solani on PDA showed that most of the isolates had inhibition effect to the both pathogenic fungi. Different isolates had different antagonistic effect to the same pathogenic fungi, and the same isolate also had different antagonistic effect to different pathogenic fungi. Among of endophyte isolates, EB6780.501 and EH32a showed the best inhibition effect to both D. sp. and R. solani. In vivo test showed endophyte infected plants clearly resistance to foliar blight caused by R. solani. But the effectiveness became less as time going on after inoculation of R. solani. There was correlation between in vitro and in vivo test, the isolates with strong in vitro inhibitory effects also showed strong plant protection. Since in vitro inhibition test is much easier and simpler to do than in vivo test, it is better to make an inhibition in vitro test before in vivo in the selection of endophyte strains with disease-resistance.

Dynamic simulation of wheat and alfalfa rust, based on metapopulation model

LI Wen-long, GUO Shu-mao, WANG Jing, LIANG Tian-gang

2009, 18(2):  46-51. 

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An infection dynamics model of wheat and alfalfa rust was established using ecological modeling and the concept of metapopulation ecology. Parameters of infection were determined and analysed from the experimental data. Next, we simulated the dynamic processes of infection using mathematical modeling software. The Results should represent the characteristics of disease prevalence in farmland and provide a scientific basis for effective farmland disease control.

Effect of adding ethanol on fermentation quality of elephant grass (Pennisetum purpureum) silage

ZHANG Lei, SHAO Tao

2009, 18(2):  52-59. 

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The effect of adding ethanol on fermentation quality of elephant grass (Pennisetum purpureum) silage was studied. Ethanol was added at 0, 1.5%, 2.5%, 3.5%, 4.5% of fresh weight, and the silos were opened after 1, 3, 5, 7, 14, or 30 days of ensiling and the fermentation quality was analyzed. Ethanol addition inhibited protein break down and significantly (P<0.05) reduced the ammonia nitrogen/total nitrogen as compared with the controls. The pH of silage with ethanol decreased slowly during initial 3 days of ensiling and then dropped faster. The lactic acid content tended to increase during ensiling and reached its highest value on about day 7. The lactic acid content of silage with ethanol addition was higher than that of the control on the 30th day of ensiling. At an early stage of fermentation the WSC (water soluble carbohydrate) content declined very quickly. The WSC utilization efficiency of silage with ethanol was higher than that of the control. Addition of ethanol significantly (P<0.05) lowered the acetic acid content compared with the control on days 1 and 14 of ensiling, but there was no marked (P>0.05) difference between the silages with ethanol added. The above experiments suggested that addition of ethanol inhibited the use of protein and WSC by aerobic bacteria and thereby reduced silage losses during the early stages of ensiling. This provided more fermentation substrate for lactic acid bacteria, which produced more lactic acid, and improved the fermentation quality of elephant grass.

Analysis of heat tolerance in Poa pratensis produced by heat stress

WANG Ting-ting, XU Guo-rong, ZHANG Ju-ren, YANG Ai-fang

2009, 18(2):  60-65. 

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A number of Poa pratensis buds with heat tolerance were selected after a heat stress treatment of 49℃ while at the multiple bud clumps stage in vitro. When the buds had developed into seedlings, they were transferred into pots to grow under natural conditions. After about half a year, several of these lines and the donor variety were treated by heat stress, and changes of chlorophyll fluorescence (Fv/Fm photochemical efficiency of PSII), MDA content, rate of ion leakage, and the chlorophyll content were measured. The stressed lines had less damage than the donor variety showing that we obtained P. pratensis with improved heat tolerance, and created a new heat tolerant germplasm of P. pratensis.

Identification of SRAP molecular markers linked to salt tolerance in Zoysia grasses

CHEN Xuan, GUO Hai-lin, XUE Dan-dan, ZHENG Yi-qi, LIU Jian-xiu

2009, 18(2):  66-75. 

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In this paper, bulked segregant analysis was used to identify SRAP molecular markers linked to salt tolerance in Zoysia grasses using two salt-tolerant, extreme types of DNA pools. From 400 pairs of SRAP primer combinations, 111 were found with polymorphic bands. These were further screened using two extreme salt-tolerant samples of Zoysia japonica and 22 pairs of polymorphism primer combinations were selected. Finally, the primer combinations with specific bands were verified using salt-tolerant individuals and 7 SRAP molecular markers closely linked to salt tolerance were obtained. Based on the size of the amplified bands they were named: Me9-Em4₂₆₀, Me9-Em18₇₂₀, Me13-Em18₅₀₀, Me5-Em20₁₈₀, Me14-Em7₂₂₀, Me6-Em17₅₅₀, Me2-Em18₂₆₀. This research will accelerate zoysia grass marker-assisted selection breeding and lay the foundation for salt-tolerant gene cloning.

Application on classification of Qinghai grassland by advanced comprehensive and sequential classification

LI Hong-mei, MA Yu-shou

2009, 18(2):  76-82. 

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Meteorological data of fifty observation stations from 1961 to 2006 were analyzed. Based on the principles of advanced comprehensive and sequential classification, the first grade grasslands of Qinghai, were classified into 11 classes, which agreed with the features of Qinghai grasslands. This showed that it was feasible to classify Qinghai grasslands and three typical regions were chosen to analyse their trends, K value (wetness degree), accumulated temperature over 0℃, and grassland succession.

Restoration dynamics after waterlogging of Carex thunbergii on leaf physiological indexes and above-ground nutritions

LIU Shou-feng, ZHOU Shou-biao, ZHENG He-quan, ZHU Xiao-feng,YANG Ji-hui

2009, 18(2):  83-88. 

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Some leaf physiological indexes and above-ground nutrition of Carex thunbergii were compared with the CK after prolonged waterlogging and the restoration situation is discussed. 1) The content of MDA, soluble sugar and proline in leaves were considerably higher than in the CK during the first four phases of restoration but significantly decreased with time and returned to the level of the CK about one month later. 2) The chlorophyll content in leaves was significantly lower than in the CK during the whole restoration phase, but increased with prolonged time. 3) The crude fibre content, SOD, and POD activity did not differ significantly from the CK during the whole restoration process. 4) The crude fat and crude protein contents increased with prolonged time in the whole restoration phase, but had decreased significantly compared with each CK. 5) The above-ground water contents were considerably lower than in the CK during the first four phases of restoration, but decreased with prolonged time, and were restored to the level of the CK about forty days later. This indicates that C. thunbergii has some restoration ability after waterlogging.

Components and age structures of Calamagrostis pseudophragmites population modules in the Yily River Valley area, China

ZHAO Yu, LI Hai-yan, Janar, REN Yan-li, ZHANG Wei, JIA Feng-qin, YANG Yun-fei

2009, 18(2):  89-94. 

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Calamagrostis pseudophragmites is a perennial, rhizomatic, and typical clonal grass. Components and age structure of modules of C. pseudophragmites populations were studied at the end of the growing season in different habitats in the Yily River Valley area of Xinjiang, China. The populations were only composed of vegetative tillers in three habitats, while the fourth had both vegetative and reproductive ones. There were three age classes of tillers with an increasing age structure. There were two age classes of rhizomes and the 2nd was dominant. The potential populations consisted of winterness tillers, apical buds of rhizomes, and dominant buds growing upwards from tiller nodes. Each potential population had an increasing age structure but of all the age classes of buds, the 1st age was the most common. Livestock feeding and trampling all reduced storage of dry matter in tillers and rhizomes.

Allelopathic potential of Xanthium sibiricum on seeds germination and seedling growth of different plants

GAO Xing-xiang, LI Mei, GAO Zong-jun, ZHANG Hong-jun, ZHANG Jia

2009, 18(2):  95-101. 

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Allelopathic effects of water extract from Xanthium sibiricum were tested with a petri dish cultivation method. The extract strongly inhibited germination, and seedling growth of sorghum(Sorghum vulgare), cucumber (Cucumis sativus), wheat(Triticum aestivum), rape(Brassica campestris), and radish (Raphanus sativus). The inhibition of rape was the strongest followed by radish. Roots were inhibited more strongly than shoots at the same concentrations of the extract. Allelopathic effects of extract on photosynthesis activity and malondialdehyde (MDA) content were also tested. The inhibitions of X. sibiricum extract to embryo and root of endosperm-removed wheat were 58.33%, 67.31% at 0.025 0 g/mL respectively, while they were 5.58%, 32.34% to sorghum cultivated in the dark. The MDA contents of cucumber and radish increased after treatment with X. sibiricum extract. These Results indicate that the allelopathic effects of X. sibiricum could inhibit photosynthesis activity and MDA, and could also inhibit non-photosynthesis activity to some extent.　

The effect of propionic acid addition on the dynamic fermentation changes of Italian ryegrass (Lolium multiflorum) silage

ZHANG Zeng-xin, SHAO Tao

2009, 18(2):  102-107. 

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The ensiling of Italian ryegrass (Lolium multiflorum) silage was carried out under laboratory conditions and propionic acid was added to give a series of different concentrations (0, 0.20%, 0.25% and 0.30%) to investigate the effect on dynamic changes in the fermentation process. Adding propionic acid to the L. multiflorum silage did not influence the VFAs during ensiling, but increased the lactic acid, WSC and LA/AA at the late stages of ensiling. The propionic acid additive decreased lactic acid and the pH value during the early stages of the fermentation. The AN/TN value and acetic acid content were also decreased in the silage. The propionic acid content was always high during the whole process of ensiling. These Results suggest that adding propionic acid to the silage at a rate of 0.25% is the optimum for fermentation quality of L. multiflorum.

Interspecific relationships of bryophytes and vascular plants in two habitats of Hani Peatland in Changbai Mountain

CHEN Xu, BU Zhao-jun, WANG Sheng-zhong, LI Hong-kai, ZHAO Hong-yan

2009, 18(2):  108-114. 

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A series of techniques including the analysis of variance, χ²-test, Spearman rank correlation and Jaccard Index based on a 2×2 contingency table were used to determine the interspecific association of the 20 dominant bryophytes and vascular plants in the Hani Peatland of Changbai Mountain. Our Results indicate that in open areas the interspecific associations are similar between Sphagnum magellanicum,S. fuscum,Polytrichum juniperinum and three vascular plants including Rhododendron parvifolium, Smilacina japonica, Ledum palustre var. ngustum. In contrast, at the forest edge the interspecific associations between S. capilifolium,S. fallax and vascular plants are mainly negative. The relationships between bryophytes and vascular plants at the forest edge are significantly positive, but are not significantly positive in open areas. Through a comparison of interspecific associations in the two habitats, we found that canopy density was an important environmental factor that influenced vegetation distribution patterns in Hani Peatland. Furthermore, in one habitat the species-pairs with larger plant important values appear to have a positive association and the species-pairs which have significantly different plant important values in the two habitats appear to have a negative association.

Effect on turf hyperspectral reflectance and color of spraying fertilizer on leaves

ZHANG Wen, ZHANG Jian-li, CHEN Gong

2009, 18(2):  115-121. 

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Color is a key component of the aesthetic quality of turf and is often evaluated in field studies. Hyperspectral parameters were used to develop improved and objective Methodsto quantify turf color and they were tested to determine if they could be used to measure turf canopy chlorophyll density and to evaluate correlations between hyperspectral parameters and visual ratings. Tall fescue (Festuca arundinacea cv. Watchdog), Kentucky Bluegrass (Poa pratensis cv. Liberator), Bermudagrass (Cynodon dactylon cv. Common), and Creeping bentgrass (Agrostis stolonifera cv. Putter) were managed during the 2007 growing season. Turf canopy hyperspectral reflectance, chlorophyll density and visual ratings were measured after spraying fertilizers (N and Fe) on turfgrass leaf surfaces. The canopy hyperspectral reflectance of four different turfgrasses significantly differed in chlorophyll density. Nitrogen or nitrogen +Fe significantly increased chlorophyll density and decreased spectral reflectance in visible wavebands. There was a significant negative correlation between turf chlorophyll density and green band (531 nm) reflectance value. Furthermore, step regression analysis indicated that the reflectance of green wavebands 531 nm and 562 nm were the most sensitive to turf chlorophyll density. A strong agreement was observed between visual assessment of turfgrass color and color value estimated by hyperspectral analysis when both Methodswere done. Therefore, hyperspectral reflectance analysis can be used to estimate turfgrass chlorophyll density and to quantify color differences among different turf species.

Seedling emergence of three Chenopodiaceae annuals in response to different sand burial depths and irrigation regimes

LUO Ya-yong, ZHAO Xue-yong, HUANG Ying-xin, ZUO Xiao-an,
WANG Shao-kun, ZHANG Yong-feng

2009, 18(2):  122-129. 

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The interactive effects of irrigation and seed burial depth in sand on seedling emergence and seedling survival in 3 annuals (Agriophyllum squarrosum, Corispermum macrocarpum and C. elongatum) which commonly grow on sand dunes in the experimental region of Inner Mongolia were investigated. Seedling emergence was examined for seeds sown on the surface, or at depths of 10, 20, 30, 40 and 50 mm in sand-filled pots. There were 4 different watering regimes in pots was: Treatments A (30 mm, initial irrigation), B (10 mm), C (10 mm), and D (30 mm). Subsequently, water equivalent to 5 mm of irrigation at 1, 2, or 6-d intervals was added to treatments A, B, and C, respectively, but no further irrigation was applied to treatment D. No seed dormancy was found in any species. A. squarrosum and C. elongatum seedling emergence was most favoured when seeds were buried at a depth of 10 mm, but for C. macrocarpum 30 mm was the most favourable depth. The average of the 4 different irrigation regimes for the 3 species was 50.63％ (A. squarrosum), 77.29％ (C. macrocarpum), and 75.21％ (C. elongatum). When seeds sown on the sand surface were irrigated, seed germination of A. squarrosum, was considerably suppressed, but many seeds of C. macrocarpum and C. elongatum, germinated though few seedlings survived due to water deficiency. The effectiveness of sand burial depth was decreased in the order C. macrocarpum, A. squarrosum and C. elongatum. The more irrigation, the greater the seedling emergence in all species but it was more after one heavy irrigation than after an accumulation of several light irrigations for A. squarrosum and C. macrocarpum , but was vice versa for C. elongatum. It is suggested that precipitation is the most crucial factor in determining the seasonal emergence of seedlings of the three species tested in the field. The vertical distribution of seeds in sand determines the proportion of seeds that germinate after precipitation and acts to maintain seed banks over multiple years.

Study on the dormancy type of seeds of four species of wild Iris in China

LU Tan-tan, ZHANG Jin-zheng, SUN Guo-feng, JIANG Chuang-dao, LI Xiao-dong, SHI Lei

2009, 18(2):  130-137. 

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The seeds of Iris ensata, Iris setosa, Iris chrysographes, and Iris bulleyana (the four species of Apogon Iris), all exhibit dormancy, but the germination varies from species to species. We researched the hygroscopicity of Iris seeds, different scarification treatments, the mechanical resistance to embryo growth (by Instron 5848 MicroTester), the growth potential of the embryo (by placing excised embryos in osmotica of PEG-6000), and cold stratification treatment. The growth potentials of the embryos were not enough to break the mechanical resistances of the micropylar structure and this was the main reason why Iris seeds failed to germinate. Excised embryos had 100% germination and the seedlings grew well, that is, the excised embryos were not dormant. Proper scarification, especially the removal of endosperm at the micropylar end broke dormancy. Cold stratification or exogenous GA treatment alone also greatly promoted germination. In summary, the four species of Iris seeds conformed to non-deep physiological dormancy.

Screening of biocontrol Trichoderma from potato rhizosphere of Western Gansu against Fusarium sambucinum and their identification

ZHANG Ru, LI Jin-hua, CHAI Zhao-xiang, WANG Di

2009, 18(2):  138-145. 

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The 108 isolates of Trichoderma were acquired from potato rhizosphere in farming-pasturing zone of Western Gansu, 10 isolates of them had been acquired via the method of face to face on PDA to the pathogen Furuisam sambucinum causing potato dry rot. Through the identification based on morphology and analysis of ITS sequencing, these 10 isolates were identified as 4 species including Trichoderma harzianum, T. longibrachiatum, T. atroviride and T. virens. T. harzianum and T. longibrachiatum are super Trichoderma species from potato rhizosphere in farming-pasturing zone of western Gansu, and these Trichoderma species had the best inhibition against F. sambucinum in this study. T. longibrachiatum showing superior inhibition effect against F. sambucinum is the first report in China.

Diversity and spatial distribution of arbuscular mycorrhiza fungi of phalanx clonal plant in the Mu Us desert

SHAN Bao-qin, HE Xue-li, DUAN Xiao-yuan

2009, 18(2):  146-154. 

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Three typical sites were chosen in the Mu Us sandland: A Research Station (110°11′22″E, 39°29′40″N), Yuling (109°42′54″E,38°20′07″N), and Wuhai (106°48′76″E , 39°46′47″N). Six colonization indexes (hypha, vesicular, arbuscular, hyphal coils, colonization potential, and spore density ) were used on roots of Artemisia ordosica and A. sphaerocephala in Auguest 2007. Colonizations of AM fungi were correlated with soil depth and sites. The species, distribution, and activity of AM fungi were affected by both the host plant and soil factors. Spore density in the rhizosphere of A. ordosica was higher then in that of A. sphaerocephala, and had a maximum value at the Yuling site. In Pearson’s correlation analysis, spore density was significantly negatively correlated with soil depth. Hyphal colonization was significantly positively correlated with vesicular colonization, but not with arbuscular colonization. The percentage of hyphal coils was significantly correlated with arbuscular colonization. The relativity of arbuscular in different sites and fine roots of host plant was remarkable. Both A. ordosica and A. sphaerocephala were excellent sand fixation plants which benefited from the mutualistic arbuscular-mycorrhizal symbiosis.

Analysis of the external economic effects of animal husbandry in the agro-pastoral transition zone of North China

FENG Li-xiao, DU Xiong, ZHANG Li-feng

2009, 18(2):  155-162. 

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Representative villages of the practice and problems of animal husbandry in the agro-pastoral transitional zone of North China, were selected and the external economic effects of their animal husbandry were determined by surveys and analysed. The existing animal husbandry in the area was based on quantity and the agricultural industry was characterized as a residue-foodchain, value-added that externalized environmental costs by utilizing agricultural byproducts and freely grazing public grassland. Livestock numbers were increased by about 40% with reduced diet feeding. The negative externality of the existing animal husbandry was expressed as grassland overgrazing and farmland over-harvesting, with grassland as the main sufferer for this external diseconomy. The overgrazing condition was further aggravated by the artificial forage input represented by silage maize. The development of low-profit animal husbandry was the basis of this external diseconomy. This illusive, superficial representation of quantity-scale-type animal husbandry, suggested it was not feasible to develop animal husbandry as a dominant industry. Further study is required to establish an eco-compensation system based on an alternative agricultural system to resolve the problem of the external diseconomy.

Analysis of the influence of discounting on grazing behavior in the late grassland contract stage

XIN Yong-liang, SUN Chun-bao, SONG Bo

2009, 18(2):  163-168. 

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By introducing a discount effect into a biomass growth and consumption model, comparisons and analysis could be made of the strategies herdsmen might take in the late grassland contract stage. The study showed that with a positive discount rate, herdsmen would take moderate grazing intensity in the contract but in order to have optimal economic income they would graze as heavily as they could at the end of the contract. Compared with not having a discount rate, the overgrazing starting time in this strategy is earlier and the extent is positively related to the discount rate. Having experienced rapid economic development for more than twenty years, discount rates in china are at a relatively high level. To prevent devastating overgrazing, the contract should be redesigned to vary the discount rate before the deadline with herdsmen.

Karyomorphology of 3 Saussurea species from the eastern of Qinghai-Tibeten Plateau

GAO Tian-peng, WANG Zhuan-li, GUO Huai-qing,
WANG Yi-feng, FANG Xiang-wen

2009, 18(2):  169-174. 

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Chromosome numbers and the karyotypes of 3 Saussurea species are studied in the eastern edge of Qinghai-Tibeten Plateau. The chromosome numbers and the karyotypes were as follows: karyotype of S. kansuensis was diploid (2n=2x=32=12m+16sm+4st) and belongs to stebbings 2B type; karyotype of S. macrota was diploid (2n=2x=26=10m+14sm+2st) and belongs to stebbings 2A type; karyotype of S. undulata was diploid (2n=2x=26=6m+20sm) and belongs to stebbings 2B type. No satellites and B chromosomes have been found in these 3 species.

Review of soil seed bank studies——soil seed bank function in natural ecosystem

SHANG Zhan-huan, XU Peng-bin, REN Guo-hua, LONG Rui-jun

2009, 18(2):  175-183. 

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Soil seed banks have an important significance in vegetation systems. Memory is an important function of soil seed banks since it can reflect the history and process of vegetation succession, and be used as a means to trace vegetation development. A main use of soil seed banks is in vegetation restoration, so soil seed banks have been widely used by restoration workers. Normal vegetation regeneration depends on the potential vegetation supply of soil seed banks and that determines the trend of vegetation succession or development. In a degraded vegetation system, the theory and technology of soil seed bank donors should be emphasized in studies as a significant base from which to practice and rebuild soil seed bank function (SSBF) for vegetation restoration.

Review of soil respiration and the impact factors on grassland ecosystem

ZHOU Ping, LIU Guo-bin, XUE Sha

2009, 18(2):  184-193. 

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Soil respiration plays an important part in the balance of the global carbon budget. This paper reviews the function of the global carbon balance, the classification of soil respiration, and the impact factors on grassland ecosystems. The ratios of each proportion of grassland ecosystem soil respiration differed because of different spatial and temporal scales. This respiration also responded differently to biotic, abiotic, and human activity factors. The abiotic impact factors included soil temperature (potentially important with climate warming), soil water content, precipitation, aridification and carbon/nitrogen elements. The biotic impact factors involved leaf area index, photosynthesis, litters, and human activities included land use change, grassland reclamation and fertilizer use. The Q₁₀ of soil respiration, key controlling factors and interaction among different impact factors are discussed. In Conclusion, soil respiration of the grassland ecosystem is a complex biochemical process. The complex biochemical process is controlled by certain major factors and regulated by interactions among multi-factors. This summary, highlights existing problems of grassland ecosystem soil respiration and suggests future directions for progress together with some future topics for research.

Status and research advances on fungicide resistance in turfgrass pathogens

HU-Jian, JIANG Qin-jun, HAN Lie-bao, WANG Li

2009, 18(2):  194-204. 

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Applying fungicide is still a most important measure for managing turfgrass diseases and maintaining turfgrass health and beauty. However, the resistance development in pathogens had easily led to failures of modern fungicides for turfgrass diseases control. Research on fungicide resistance had been developed in the field of turfgrass abroad from 1960s,but none were found in China. This paper reviewed the research advances in the fungicide resistance of pathogenic fungi on turfgrass, including the status of fungicides resistance on turfgrass, the traditional research fields, the modern molecular research fields and the management strategies of fungicide resistance.

Progress in research on Trifolium genetic engineering

LIANG Zhe, JIANG San-jie, WEI Li, TANG Yi-xiong, WU Yan-min

2009, 18(2):  205-211. 

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Trifolium is an important forage that is widely cultivated in the world, and is characterized by its dietary rich nutrition and excellent quality. Genetic transformation has launched a new era in Trifolium breeding and germplasm creativity. This paper reviews recent progress in quality-improvement, promoting resistance to viruses, fungi, insects, and stress and in work on genetic transformation of Trifolium problems and prospects for application of genetic engineering in Trifolium are discussed.

A study on callus induction and redifferentiation of clover

WANG You-sheng, WANG Ying, LI Yang-chun

2009, 18(2):  212-215. 

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The hypocotyls, leaf and cotyledon of four varieties of clover (Trifolum) were used to study the effect of hormone concentrations on callus induction and redifferentiation. Different varieties and explants each had different induction requirements. The hypocotyl callus induction rate of Trifolium hybridum was high (96.7%), while that of somatic embryogenesis was 33.4%. The best medium for embryogenic callus induction was modified SH+2,4-D 4.0 mg/L+KT 1 mg/L, while for embryoid redifferentiation and plant regeneration it was MSO.