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    15 August 2002, Volume 13 Issue 8
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    Characteristics of vegetation, soil, and their coupling of degraded grasslands
    HOU Fujiang, NAN Zhibiao, XIAO Jingyu, CHANG Shenghua
    2002, (8):  915-922. 
    Asbtract ( 0 )  
    This paper presented the characteristics of the vegetation, soil, and their coupling in the gradient of grazing pressure of the degraded alpine grassland in Sunan county and of the typical arid grassland in Huanxian county, Gansu province.The abundance index of species, Simpson index, Shannon Wiener index, Cody index, nutrient functional diversity index and life type diversity index increased, while the Bray Curtis index and nitrogen fixation diversity index decreased with the reduced grazing intensity in both types of degraded grassland.With reduced grazing pressure, the contents of total nitrogen, available nitrogen and organic matter in both grasslands and the content of available phosphorus in arid grassland at 0～40cm soil depth were increased, and that of total phosphorus in alpine grassland was decreased, while phosphorus concentration in arid grassland showed no regular pattern of change.The total and available nitrogen, available phosphorus and the ratio of available phosphorus to total phosphorus and of organic carbon to nitrogen were all higher in alpine grassland than in arid grassland. The grey correlativity of vertical distribution pattern between soil elements and living root biomass was positively related to grazing pressure,while the coupling intensity of soil herbage subsystem was increased with decreased grazing pressure.There existed a significant correlation between poor soil elements and abundance of poisonous and poor nutritional plants in both degraded grasslands.The degradation process of grassland resulted not only from the degeneration of vegetation and soil subsystems, but also from the disappearance of coupling between both subsystems and the development of their discordance. The ecological process could be quantified by coupling intensity and discordance intensity.It is concluded that the studied arid grassland was degraded more seriously than alpine grassland.
    Eco-restoration of abandoned farmland in the Loess Plateau
    HOU Fujiang, XIAO Jinyu, NAN Zhibiao
    2002, (8):  923-929. 
    Asbtract ( 0 )  
    The vegetation on abandoned farmland was succeeded from Agriophyllum arenarium community to Lespedeza davurica community under cutting conditions. More plant species was recruited at the initial stage of restoration.The new plant species established earlier were annual Agriophyllum arenarium and perennial Pennisetum flaccidum which could be the dominant species or sub dominant species. The perennial Artemisia capillaris established in early middle stage could be the sub dominant species,and leguminous plants appeared in late middle stage could only be the associated species. The aboveground biomass of annual species reduced by 8.8% annually,while the perennial species increased with the similar rate. The aboveground biomass of leguminous species increased continuously. As the restoration proceeded, more underground biomass was distributed in upper soil layer. In 1～7 years of restoration of abandoned land,the clay and silt in 0～30cm soil profile reduced, while grit increased, but the inverse trend occurred after 7 years. The water content in 0～100cm soil profile increased continuously, especially during middle stage. Total and available nitrogen in 0～100cm soil profile reduced in early stage, but increased in late stage. Total and available phosphorus and organic carbon in soil profile reduced continuously under cutting conditions. For the restoration of abandoned farmland to the current stable community,it would take 8～9 years for dominant population,9～11 years for vegetative community and 11～12 years for soil system.
    Regrowth of different plant populations in mixed pasture
    YU Yingwen, JIANG Wenlan, RAN Fanjun, XU Zhen, WAN Yuansu
    2002, (8):  930-934. 
    Asbtract ( 0 )  
    The number of tillers and leaf regrowth of perennial ryegrass (Lolium perenne) and that of branches and stolon growth of white clover (Trifolium repens) in mixed ryegrass/white clover pastures under different cutting frequency were monitored from 1998 to 2000,and the herbage yields and the proportion of each component in total yields were also determined. The results showed that cutting could stimulate perennial ryegrass leaf regrowth and white clover branching, maintain proper proportions of perennial ryegrass and white clover in the mixed pasture, and create the environments for the coexistence of the two species. Therefore, the total annual dry matter yields of the pasture was increased. However, cutting frequency had no significant effects on herbage yields and vegetative composition (P>0.05). More leaf regrowth of perennial ryegrass was found in theplots cut in June than in August, whereas white clover exhibited an inverse trend. The herbage yield of perennial ryegrass depended on its leaf regrowth, while the dry matter accumulation of white clover relied on its stolon branching numbers. During the period of three year experiment, the proportion of perennial ryegrass and white clover in total herbage yields obtained from the plots under cutting was 50% and 15%, respectively, approximately 10% or 5% lower than its initial value,while CKwas 39% and 6%,respectively.
    Effect of soil compaction on Vicia faba of growth in the Loess Plateau
    NAN Zhibiao, ZHAO Hongyang, NIE Bin
    2002, (8):  935-938. 
    Asbtract ( 0 )  
    The effect of soil compaction on the growth of Vicia faba was studied by pot experiment,field plot experiment, and farmers'field production during two consecutive years.The results showed that increasing soil bulk density at 0～7 cm depth significantly decreased the root and shoot dry weight per plant, increased plant mortality caused by Fusarium species, and decreased seed yields.Field experiments indicated that compared to the plants grown on the plots with soil bulk density of 1.55 and 1.64 g·cm-3,the root and shoot dry weight of plants grown on the plots with soil bulk density of 1.84g·cm-3 decreased by 30.8% and 27.9%, respectively, while the plant mortality rate increased by 21.0～48.7%,and seed yields decreased by 19.8%.The trials conducted on eight farmers'land illustrated that there existed significant negative correlations between soil bulk density in Spring and root and shoot dry weight of Vicia faba seedlings, and between soil bulk density in Autumn and seed yields. The causes of high soil compaction were discussed,and suggestions for improving soil quality were presented.
    Regulation of fertilizer application on yield and root growth of spring wheat-faba bean intercropping system
    ZHANG Enhe, LI Lingling, HUANG Gaobao, HUANG Peng, CHAI Qiang
    2002, (8):  939-942. 
    Asbtract ( 0 )  
    The effects of Nand Pfertilizer application on the multiple population yield and root growth of spring wheat (Triticum aestivum) spring faba bean(Vicia sativa)intercropping system were studied by two field experiments with 0,150 and 225 kgN·hm-2, three pot and pool experiments with 2 Napplications (0,100mg N·kg-1 soil)and 3 Papplications (0,100 and 200 mg P·kg-1 soil).The results showed that this intercropping system had a significant advantage of yield and beneficial effects.Compared to Po supply, Pfertilization increased the seed yield by 48.39% for intercropped spring wheat and 16.69% for intercropped faba bean in field experiment.Furthermore,the total seed yield of both crops was increased by 20.07% to 43.14% in pool culture,and the grain yield of intercropped faba bean was increased by 58.46% to 78.78%. In the intercropping system,the growth peak of root density of both crops was appeared alternately, the peak of wheat root growth being earlier than that of faba bean. The maximum root weight of intercropped wheat was in its early heading periods, whereas that of faba bean appeared at its maturity periods,which reduced the competition for water and nutrients between the crops, and resulted in yield increase. The weight,length and surface area of wheat roots in Psupply were increased by 54.33%, 48.88% and 47.00%,and in Nsupply,they were increased by 15.25%, 11.61% and 11.46%,respectively. About 57.61% of wheat root weight and 69.20% of faba bean root weight were distributed at 0～30cm soil depths in the treatments of receiving Pfertilizer at various rates,which indicated that Psupply increased root weight and length of both crops in the intercropping system.
    Effect of pesticides on field-controlling root rot of Vicia faba
    NAN Zhibiao, GE Gaozu, LI Chunjie
    2002, (8):  943-947. 
    Asbtract ( 0 )  
    The effect of pesticides on field controlling root rot of Vicia faba was studied in two consecutive years by seed treatment of fungicides and their combination.The results of the first year field experiments showed that among the 11 treatments tested,triadimefon of 0.01 g a.i穔g-1 seeds was more effective than other fungicides applied singly or in combinations.The other test fungicides included thiophanate methyl, thiram, oxadixyl and metalaxyl.Compared to the control, triadimefon treatment reduced the root rot index of 6-week-old seedlings by 51.5%,and plant accumulated percent mortality by 36%.Consequently,the treatment increased seed yield/plant by 21% and seed yield/ ha by 97.6%.In the trials carried out in the following year,the plant percent mortality was reduced by 31.9% and seed yield increased by 19.6% under triadimefon seed treatment.It is demonstrated that seed treatment by triadimefon effectively controlled root rot,promoted plant growth, and increased seed yield of faba bean in the fields.
    Variation in seed yield components among varieties of Poa pratensis
    SUN Jianhua, WANG Yanrong, GUO Yuxia
    2002, (8):  948-952. 
    Asbtract ( 0 )  
    Seed yield and its characteristics of 28 varieties of Poa pratensis in field plots at Lanzhou,China were evaluated in2001.The results showed that the seed yields among the varieties were significantly different (P<0.01) by LSDtest.The highest yield was 643.4～650.2kg·hm-2 obtained from varieties of Balin and Monoply, the lowest was 90.1kg·hm-2 obtained from Elysee, and the other varieties were in the middle groups with the yields varied from 114.7kg·hm-2 to 435.1kg·hm-2.Correlation analysis between seed yield and yielding characteristics indicated that the main factors affecting seed yield were the number of fertile tillers per plant (r=0.785),the height of fertile tiller (r=0.712), the length of inflorescence (r=0.743), and the number of spikelets/fertile tiller (r=0.786).Cluster analysis for seed production capacity based on seed yield and above mentioned 4 main characteristics showed that the 28 varieties could be divided into 6 grades.
    Response of seed germination of three xeromorphic shrubs to drought stress
    ZENG Yanjun, WANG Yanrong, SA Ren, TIAN Xuemei
    2002, (8):  953-956. 
    Asbtract ( 0 )  
    The seed germination, seedling growth and water absorption characteristic of Caragana korshinskii, Hedysarum scoparium, and Artemisia sphearocephala were investigated under different osmotic potentials (PEG 6000, -0.3～-2.7MPa). The results showed that under drought stress, C.korshinskii had the highest germination rate, while A.sphearocephala had the lowest one.Under -0.3～-0.6MPa, the root length of 10 day old A.sphearocephala seedling was significantly longer than that of H. scoparium and Caragana korshinskii (P<0.05),and the length reached 7.9, 4.5 and 3.1cm, respectively. There existed a significant positive correlation between seed germination rate and 72h water absorption rate of the three shrub seeds(P<0.01). The relationships among germination characteristics, root length, and survive percentage of seedlings were also discussed.
    Response of alfalfa seed to stress storage conditions
    LI Chunjie, WANG Yanrong, ZHU Tingheng, YU Ling
    2002, (8):  957-961. 
    Asbtract ( 0 )  
    The seed germination rate, seed mortality, seedling length, and infection rate of alfalfa (Medicago sativa L.cv.'Longdong') were measured at constant temperature 20℃ every 60 days during one year storage period after inoculated or no inoculated by Fusarium avenaceum under room temperature (RT),35℃,and 35℃ and +10% seed moisture content (SMC) conditions. Field emergence rates of seeds under above treatments were also observed,and seed borne fungi were detected under the conditions mentioned above and controlled deterioration (CD) as well. The results showed that the percentage of isolated alfalfa seed borne fungi was increased from 10% under room temperature and 35℃ to 29% under 35℃+10%SMC.Disease resistance was declined, and seed mortality and seedling infection rate under 35℃+10%SMCwere significantly higher than those under room temperature and 35℃ respectively (P<0.05). The seed germination rate and field emergence rate were also decreased significantly (P<0.05). Seedling shoot and root length under 35℃+10%SMCwere significantly less than those under RTand 35℃ respectively (P<0.05).The percentages of both seed borne fungi isolated and field emergence were decreased,and that of seedling infection was increased with storage period extending from 60 to 360 days. Compared to no inoculated control,the percentage of seed germination, seedling shoot and root length were decreased, and seed mortality and seedling infection rate were increased after inoculated by F.avenaceum.
    Water distribution patterns in different degraded desert grasslands of Reaumuria soongorica
    WANG Yanrong, ZENG Yanjun, ZHANG Baoling, TA Lateng
    2002, (8):  962-966. 
    Asbtract ( 0 )  
    Water distribution pattern and water use efficiency in soil plant atmosphere system for light,medium,and heavy degraded Reaumuria soongorica grasslands were studied in Alashan region of Inner Mongolia.The total precipitation in2001 was 124.3mm,of which 119.4mm occured during experimental period. Soil water content (SWC) in 10～40cm layer was greatly affected by the evapotranspiration. The SWCin10～20cm layer of medium degraded grassland paddock was significantly lower (P<0.05), and the SWC in 20～40cm layer of light degraded paddock was lower than that of other paddocks due to different transpiration rate and root distribution depth between the main co existing plant species of R. soongorica and Cleistogenes soongorica in the paddocks. The annual average bare land evaporation and R. soongorica population transpiration were 30.6mm and 11.9mm, respectively. As the grassland further degraded, the bare land evaporation and transpiration through Peganum nigellastrum population, a degradation indicating plant species, increased, while the transpiration of R. soongorica decreased.In addition, the water use efficiency of the grassland and dominant plant species markedly decreased with the increasing grassland degradation.Compared to the light degraded paddocks, for instance,the water use efficiency of medium and heavy degraded paddocks were reduced by 14.6% and 46.1 % for total biomass production, and by 37.8% and 73.8% for R. soongorica,respectively.
    Dynamics of forage supplement and nutrition requirements of grazing sheep in alpine grasslands
    XIAO Jinyu, HOU Fujiang, GUO Zhenggang, LI Juncheng, WANG Qing ; AN Yufeng
    2002, (8):  967-970. 
    Asbtract ( 0 )  
    The dynamics of forage supply and nutrition requirements of sheep were monitored for a whole year under alpine grassland conditions in Sunan County,Gansu Province.The digestion and metabolism of grazed sheep were determined in different seasons. The results showed that the DE(9.76MJ),CP(21.53%) and the ratio of crude protein to digestible energy (22.06g稭J-1) of forage were the highest in Spring,while the herbage dry matter yield and dry matter intake (60.51?3.42 g稺 0.75 kg-1穌-1) by grazed sheep were the lowest.Supplementary DMespecially in energy should be provided. The ratio of crude protein to digestible energy was 17.62g稭J-1 in Summer,and was somewhat higher. The nitrogen utility of the forage would be improved,if energy feed was supplemented. Both the quality and quantity of forage produced in grasslands in Autumn could meet the sheep requirement. Whereas during Winter, neither forage yield nor nutritive value was sufficient for sheep, and the contents of the DEand CPof forage were the lowest in the year, which were 4.30MJand 4.63%, respectively. The nitrogen metabolism of sheep was negative. Therefore, DM,especially DEand CP,should be supplemented. To improve the conditions, it was necessary to develop seasonal animal husbandry,and combine the subsystems into coupling systems.
    Characteristics of vegetation, soil, and their coupling of degraded grasslands
    HOU Fujiang, NAN Zhibiao, XIAO Jingyu, CHANG Shenghua
    2002, (8):  915-922. 
    Asbtract ( 2746 )   PDF (1317KB) ( 499 )  
    This paper presented the characteristics of the vegetation, soil, and their coupling in the gradient of grazing pressure of the degraded alpine grassland in Sunan county and of the typical arid grassland in Huanxian county, Gansu province.The abundance index of species, Simpson index, Shannon Wiener index, Cody index, nutrient functional diversity index and life type diversity index increased, while the Bray Curtis index and nitrogen fixation diversity index decreased with the reduced grazing intensity in both types of degraded grassland.With reduced grazing pressure, the contents of total nitrogen, available nitrogen and organic matter in both grasslands and the content of available phosphorus in arid grassland at 0～40cm soil depth were increased, and that of total phosphorus in alpine grassland was decreased, while phosphorus concentration in arid grassland showed no regular pattern of change.The total and available nitrogen, available phosphorus and the ratio of available phosphorus to total phosphorus and of organic carbon to nitrogen were all higher in alpine grassland than in arid grassland. The grey correlativity of vertical distribution pattern between soil elements and living root biomass was positively related to grazing pressure,while the coupling intensity of soil herbage subsystem was increased with decreased grazing pressure.There existed a significant correlation between poor soil elements and abundance of poisonous and poor nutritional plants in both degraded grasslands.The degradation process of grassland resulted not only from the degeneration of vegetation and soil subsystems, but also from the disappearance of coupling between both subsystems and the development of their discordance. The ecological process could be quantified by coupling intensity and discordance intensity.It is concluded that the studied arid grassland was degraded more seriously than alpine grassland.
    Eco-restoration of abandoned farmland in the Loess Plateau
    HOU Fujiang, XIAO Jinyu, NAN Zhibiao
    2002, (8):  923-929. 
    Asbtract ( 1071 )   PDF (862KB) ( 500 )  
    The vegetation on abandoned farmland was succeeded from Agriophyllum arenarium community to Lespedeza davurica community under cutting conditions. More plant species was recruited at the initial stage of restoration.The new plant species established earlier were annual Agriophyllum arenarium and perennial Pennisetum flaccidum which could be the dominant species or sub dominant species. The perennial Artemisia capillaris established in early middle stage could be the sub dominant species,and leguminous plants appeared in late middle stage could only be the associated species. The aboveground biomass of annual species reduced by 8.8% annually,while the perennial species increased with the similar rate. The aboveground biomass of leguminous species increased continuously. As the restoration proceeded, more underground biomass was distributed in upper soil layer. In 1～7 years of restoration of abandoned land,the clay and silt in 0～30cm soil profile reduced, while grit increased, but the inverse trend occurred after 7 years. The water content in 0～100cm soil profile increased continuously, especially during middle stage. Total and available nitrogen in 0～100cm soil profile reduced in early stage, but increased in late stage. Total and available phosphorus and organic carbon in soil profile reduced continuously under cutting conditions. For the restoration of abandoned farmland to the current stable community,it would take 8～9 years for dominant population,9～11 years for vegetative community and 11～12 years for soil system.
    Regrowth of different plant populations in mixed pasture
    YU Yingwen, JIANG Wenlan, RAN Fanjun, XU Zhen, WAN Yuansu
    2002, (8):  930-934. 
    Asbtract ( 1052 )   PDF (277KB) ( 237 )  
    The number of tillers and leaf regrowth of perennial ryegrass (Lolium perenne) and that of branches and stolon growth of white clover (Trifolium repens) in mixed ryegrass/white clover pastures under different cutting frequency were monitored from 1998 to 2000,and the herbage yields and the proportion of each component in total yields were also determined. The results showed that cutting could stimulate perennial ryegrass leaf regrowth and white clover branching, maintain proper proportions of perennial ryegrass and white clover in the mixed pasture, and create the environments for the coexistence of the two species. Therefore, the total annual dry matter yields of the pasture was increased. However, cutting frequency had no significant effects on herbage yields and vegetative composition (P>0.05). More leaf regrowth of perennial ryegrass was found in theplots cut in June than in August, whereas white clover exhibited an inverse trend. The herbage yield of perennial ryegrass depended on its leaf regrowth, while the dry matter accumulation of white clover relied on its stolon branching numbers. During the period of three year experiment, the proportion of perennial ryegrass and white clover in total herbage yields obtained from the plots under cutting was 50% and 15%, respectively, approximately 10% or 5% lower than its initial value,while CKwas 39% and 6%,respectively.
    Effect of soil compaction on Vicia faba of growth in the Loess Plateau
    NAN Zhibiao, ZHAO Hongyang, NIE Bin
    2002, (8):  935-938. 
    Asbtract ( 936 )   PDF (238KB) ( 314 )  
    The effect of soil compaction on the growth of Vicia faba was studied by pot experiment,field plot experiment, and farmers'field production during two consecutive years.The results showed that increasing soil bulk density at 0～7 cm depth significantly decreased the root and shoot dry weight per plant, increased plant mortality caused by Fusarium species, and decreased seed yields.Field experiments indicated that compared to the plants grown on the plots with soil bulk density of 1.55 and 1.64 g·cm-3,the root and shoot dry weight of plants grown on the plots with soil bulk density of 1.84g·cm-3 decreased by 30.8% and 27.9%, respectively, while the plant mortality rate increased by 21.0～48.7%,and seed yields decreased by 19.8%.The trials conducted on eight farmers'land illustrated that there existed significant negative correlations between soil bulk density in Spring and root and shoot dry weight of Vicia faba seedlings, and between soil bulk density in Autumn and seed yields. The causes of high soil compaction were discussed,and suggestions for improving soil quality were presented.
    Regulation of fertilizer application on yield and root growth of spring wheat-faba bean intercropping system
    ZHANG Enhe, LI Lingling, HUANG Gaobao, HUANG Peng, CHAI Qiang
    2002, (8):  939-942. 
    Asbtract ( 981 )   PDF (220KB) ( 319 )  
    The effects of Nand Pfertilizer application on the multiple population yield and root growth of spring wheat (Triticum aestivum) spring faba bean(Vicia sativa)intercropping system were studied by two field experiments with 0,150 and 225 kgN·hm-2, three pot and pool experiments with 2 Napplications (0,100mg N·kg-1 soil)and 3 Papplications (0,100 and 200 mg P·kg-1 soil).The results showed that this intercropping system had a significant advantage of yield and beneficial effects.Compared to Po supply, Pfertilization increased the seed yield by 48.39% for intercropped spring wheat and 16.69% for intercropped faba bean in field experiment.Furthermore,the total seed yield of both crops was increased by 20.07% to 43.14% in pool culture,and the grain yield of intercropped faba bean was increased by 58.46% to 78.78%. In the intercropping system,the growth peak of root density of both crops was appeared alternately, the peak of wheat root growth being earlier than that of faba bean. The maximum root weight of intercropped wheat was in its early heading periods, whereas that of faba bean appeared at its maturity periods,which reduced the competition for water and nutrients between the crops, and resulted in yield increase. The weight,length and surface area of wheat roots in Psupply were increased by 54.33%, 48.88% and 47.00%,and in Nsupply,they were increased by 15.25%, 11.61% and 11.46%,respectively. About 57.61% of wheat root weight and 69.20% of faba bean root weight were distributed at 0～30cm soil depths in the treatments of receiving Pfertilizer at various rates,which indicated that Psupply increased root weight and length of both crops in the intercropping system.
    Effect of pesticides on field-controlling root rot of Vicia faba
    NAN Zhibiao, GE Gaozu, LI Chunjie
    2002, (8):  943-947. 
    Asbtract ( 1162 )   PDF (770KB) ( 367 )  
    The effect of pesticides on field controlling root rot of Vicia faba was studied in two consecutive years by seed treatment of fungicides and their combination.The results of the first year field experiments showed that among the 11 treatments tested,triadimefon of 0.01 g a.i穔g-1 seeds was more effective than other fungicides applied singly or in combinations.The other test fungicides included thiophanate methyl, thiram, oxadixyl and metalaxyl.Compared to the control, triadimefon treatment reduced the root rot index of 6-week-old seedlings by 51.5%,and plant accumulated percent mortality by 36%.Consequently,the treatment increased seed yield/plant by 21% and seed yield/ ha by 97.6%.In the trials carried out in the following year,the plant percent mortality was reduced by 31.9% and seed yield increased by 19.6% under triadimefon seed treatment.It is demonstrated that seed treatment by triadimefon effectively controlled root rot,promoted plant growth, and increased seed yield of faba bean in the fields.
    Variation in seed yield components among varieties of Poa pratensis
    SUN Jianhua, WANG Yanrong, GUO Yuxia
    2002, (8):  948-952. 
    Asbtract ( 927 )   PDF (712KB) ( 295 )  
    Seed yield and its characteristics of 28 varieties of Poa pratensis in field plots at Lanzhou,China were evaluated in2001.The results showed that the seed yields among the varieties were significantly different (P<0.01) by LSDtest.The highest yield was 643.4～650.2kg·hm-2 obtained from varieties of Balin and Monoply, the lowest was 90.1kg·hm-2 obtained from Elysee, and the other varieties were in the middle groups with the yields varied from 114.7kg·hm-2 to 435.1kg·hm-2.Correlation analysis between seed yield and yielding characteristics indicated that the main factors affecting seed yield were the number of fertile tillers per plant (r=0.785),the height of fertile tiller (r=0.712), the length of inflorescence (r=0.743), and the number of spikelets/fertile tiller (r=0.786).Cluster analysis for seed production capacity based on seed yield and above mentioned 4 main characteristics showed that the 28 varieties could be divided into 6 grades.
    Response of seed germination of three xeromorphic shrubs to drought stress
    ZENG Yanjun, WANG Yanrong, SA Ren, TIAN Xuemei
    2002, (8):  953-956. 
    Asbtract ( 1190 )   PDF (578KB) ( 521 )  
    The seed germination, seedling growth and water absorption characteristic of Caragana korshinskii, Hedysarum scoparium, and Artemisia sphearocephala were investigated under different osmotic potentials (PEG 6000, -0.3～-2.7MPa). The results showed that under drought stress, C.korshinskii had the highest germination rate, while A.sphearocephala had the lowest one.Under -0.3～-0.6MPa, the root length of 10 day old A.sphearocephala seedling was significantly longer than that of H. scoparium and Caragana korshinskii (P<0.05),and the length reached 7.9, 4.5 and 3.1cm, respectively. There existed a significant positive correlation between seed germination rate and 72h water absorption rate of the three shrub seeds(P<0.01). The relationships among germination characteristics, root length, and survive percentage of seedlings were also discussed.
    Response of alfalfa seed to stress storage conditions
    LI Chunjie, WANG Yanrong, ZHU Tingheng, YU Ling
    2002, (8):  957-961. 
    Asbtract ( 957 )   PDF (685KB) ( 339 )  
    The seed germination rate, seed mortality, seedling length, and infection rate of alfalfa (Medicago sativa L.cv.'Longdong') were measured at constant temperature 20℃ every 60 days during one year storage period after inoculated or no inoculated by Fusarium avenaceum under room temperature (RT),35℃,and 35℃ and +10% seed moisture content (SMC) conditions. Field emergence rates of seeds under above treatments were also observed,and seed borne fungi were detected under the conditions mentioned above and controlled deterioration (CD) as well. The results showed that the percentage of isolated alfalfa seed borne fungi was increased from 10% under room temperature and 35℃ to 29% under 35℃+10%SMC.Disease resistance was declined, and seed mortality and seedling infection rate under 35℃+10%SMCwere significantly higher than those under room temperature and 35℃ respectively (P<0.05). The seed germination rate and field emergence rate were also decreased significantly (P<0.05). Seedling shoot and root length under 35℃+10%SMCwere significantly less than those under RTand 35℃ respectively (P<0.05).The percentages of both seed borne fungi isolated and field emergence were decreased,and that of seedling infection was increased with storage period extending from 60 to 360 days. Compared to no inoculated control,the percentage of seed germination, seedling shoot and root length were decreased, and seed mortality and seedling infection rate were increased after inoculated by F.avenaceum.
    Water distribution patterns in different degraded desert grasslands of Reaumuria soongorica
    WANG Yanrong, ZENG Yanjun, ZHANG Baoling, TA Lateng
    2002, (8):  962-966. 
    Asbtract ( 873 )   PDF (273KB) ( 242 )  
    Water distribution pattern and water use efficiency in soil plant atmosphere system for light,medium,and heavy degraded Reaumuria soongorica grasslands were studied in Alashan region of Inner Mongolia.The total precipitation in2001 was 124.3mm,of which 119.4mm occured during experimental period. Soil water content (SWC) in 10～40cm layer was greatly affected by the evapotranspiration. The SWCin10～20cm layer of medium degraded grassland paddock was significantly lower (P<0.05), and the SWC in 20～40cm layer of light degraded paddock was lower than that of other paddocks due to different transpiration rate and root distribution depth between the main co existing plant species of R. soongorica and Cleistogenes soongorica in the paddocks. The annual average bare land evaporation and R. soongorica population transpiration were 30.6mm and 11.9mm, respectively. As the grassland further degraded, the bare land evaporation and transpiration through Peganum nigellastrum population, a degradation indicating plant species, increased, while the transpiration of R. soongorica decreased.In addition, the water use efficiency of the grassland and dominant plant species markedly decreased with the increasing grassland degradation.Compared to the light degraded paddocks, for instance,the water use efficiency of medium and heavy degraded paddocks were reduced by 14.6% and 46.1 % for total biomass production, and by 37.8% and 73.8% for R. soongorica,respectively.
    Dynamics of forage supplement and nutrition requirements of grazing sheep in alpine grasslands
    XIAO Jinyu, HOU Fujiang, GUO Zhenggang, LI Juncheng, WANG Qing ; AN Yufeng
    2002, (8):  967-970. 
    Asbtract ( 911 )   PDF (510KB) ( 350 )  
    The dynamics of forage supply and nutrition requirements of sheep were monitored for a whole year under alpine grassland conditions in Sunan County,Gansu Province.The digestion and metabolism of grazed sheep were determined in different seasons. The results showed that the DE(9.76MJ),CP(21.53%) and the ratio of crude protein to digestible energy (22.06g稭J-1) of forage were the highest in Spring,while the herbage dry matter yield and dry matter intake (60.51?3.42 g稺 0.75 kg-1穌-1) by grazed sheep were the lowest.Supplementary DMespecially in energy should be provided. The ratio of crude protein to digestible energy was 17.62g稭J-1 in Summer,and was somewhat higher. The nitrogen utility of the forage would be improved,if energy feed was supplemented. Both the quality and quantity of forage produced in grasslands in Autumn could meet the sheep requirement. Whereas during Winter, neither forage yield nor nutritive value was sufficient for sheep, and the contents of the DEand CPof forage were the lowest in the year, which were 4.30MJand 4.63%, respectively. The nitrogen metabolism of sheep was negative. Therefore, DM,especially DEand CP,should be supplemented. To improve the conditions, it was necessary to develop seasonal animal husbandry,and combine the subsystems into coupling systems.
    Change of moisture retention in sandy soil after planting mixed forest of Populus spp.and Robinia pseudoacacia
    ZHANG Dinghua, ZHAI Mingpu, JIA Liming, LIN Ping
    2002, (8):  971-974. 
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    The change of soil moisture retention after planting mixed forest of Populus spp.and Robinia pseudoacacia was studied by comparative method. The results showed that soil moisture retention, spatial distribution of soil pore, and soil water capacity were improved and increased in sandy soil after Populus spp. and Robinia pseudoacacia being planted, and the improvement in the mixed forest of Populus spp. and R. pseudoacacia was greater than that in the pure forest of Populus spp.or R. pseudoacacia.The basic reason of soil moisture retention being improved was the increment of soil organic matter,which improved soil pore condition.
    Landscape pattern and productivity characteristics of the oasis landscape ecosystem in Linze,Gansu,China
    LIU Xuelu, REN Jizhou, ZHANG Zihe
    2002, (8):  975-978. 
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    Oasis landscape ecosystem is composed of 10 landscape elements,i.e,residence land,cultivated land,grassland,forestland,water area, water system, road, rocky desert, sandy desert, and gravel desert. Among the elements, cultivated land formed by human being production covers the most of the area,is most connected, and hence,is the matrix of the oasis landscape ecosystem. Residence land, grassland, forestland, water area, rocky desert, sandy desert, and gravel desert are patches. Residence land and forestland generate from human being production,while rocky desert, gravel desert and sandy desert are the remnant with the human being disturbance. Water region and grassland are the environmental resources remnant after natural disturbance. Water system and road are corridors.Cultivated land dominated in plant production should be utilized with more productive layers through developing animal production other than expanding used area to maintain the landscape heterogeneity and diversity of the oasis landscape ecosystem. For remnant and environmental resource patches, it should be profitable in preserving and stabilizing landscape heterogeneity and diversity, exploiting the functions of water and soil conservation, tourism, windbreak and sand fixation. For landscape elements remnant only, it should be fruitful in avoiding degeneration of the landscape pattern to explore their preceding plant production with moderate plant production.
    Landscape ecological mechanism on system coupling of the meta-ecosystem consisted of mountain,desert and oasis in Hexi corridor,Gansu,China
    LIU Xuelu, REN Jizhou
    2002, (8):  979-984. 
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    The fundament of system coupling is heterogeneity,and the basic prerequisite is that there are connective corridors in the same type between ecosystems.The landscape ecological mechanism of system coupling is the spatial difference of non biotic environment and the heterogeneity caused by disturbances.The force or energy of system coupling is disturbances.From in the view of landscape ecology,system coupling is the merging process of different landscape elements between different landscape ecosystems followed by the process of character changing of landscape elements with scale changing.Based on the essence of disturbances,system coupling can be divided into two types as natural system coupling and artificial system coupling.Natural system coupling is the base of artificial system coupling,and hence,the enhance of eco productivity of coupling system is based on the optimization of artificial system coupling.
    Influence of saltwater irrigation on the yield and quality of Cynodon dactylon under desert conditions
    ZHOU Ruilian, Paternak Dov, ZHAO Halin
    2002, (8):  985-989. 
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    Responses of six varieties (Suwannee, Coast cross, Tifton44, Tifton68, Tifton78 and Tifton85) of Cynodon dactylon to irrigation water salinity were investigated in field by means of a double line source experimental design. The digestibility of the grass by goat was analyzed using the rumen gastric justice digestion method. The results showed that the six varieties grew well, and had a high yield of fresh grass when eletro conductivity (Eci)<10 ds穖-1. Particularly when Eci = 4.4 ds穖-1, the fresh grass yield of Coast cross, Suwannee, Tifton44, Tifton68, Tifton78 and Tifton85 was respectively increased by 142.1%, 611%, 136%, 121.1%, 202.3% and 109.7%, in comparison with fresh water (Eci=1.2) irrigation. Dry matter yield was also elevated with the increasing salinity of irrigated water. There was no obvious effect of salinity on crude protein, fiber and ash contents in the six varieties. Goats were fond of eating the hay irrigated by saline water, perhaps because of its higher digestibility. At least, the yield and quality of Cynodon dactylon were not effected by saltwater irrigation.
    Temporal pattern of arthropod community on cultivated alfalfa grassland
    LIU Changzhong, WANG Wanxiong, WU Xiaogang, SHANG Jinwen
    2002, (8):  990-992. 
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    The variation of species and diversities of the arthropod community on cultivated alfalfa grassland was investigated and studied.Principal component analysis and optimal sorting method were used to study its temporal patterns.The results showed that the difference and regularity of species richness,and the diversity and evenness of the arthropod community at different time were obvious.The numbers of the species of insect pests and their natural enemies were the most in the last ten days of June,but the peak period of individual numbers of the natural enemies was later than that of insect pests.The main factors and temporal patterns of arthropod community in the course of seasons were obvious.Based on the results,the temporal patterns of arthropod community on cultivated alfalfa grassland could be divided into four stages:before the first ten days of May,the middle ten days of May to the first ten days of June,the middle ten days of June to the middle ten days of July,and after the middle ten days of July.Considering the climatic and phenological development,the characteristics of the pests and the natural enemies occurring in each stage were analyzed,and the corresponding management tactics were discussed.
    Spatial pattern of Tetranychus urticae population in apple tree garden
    LIU Changzhong, WANG Gang, WANG Wanxiong, ZHOU Shurong
    2002, (8):  993-996. 
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    Spatial pattern of insect population is an important aspect of insect ecology. It reveals the spatial structure characteristics of populations, and provides a basis for relevant sampling techniques and data transformation. Tetranychus urticae Koch is a serious pest of apple tree.Its spatial pattern and time series dynamics were analyzed by calculating four indices of aggregation, and parameters of Iwao model. The results showed that the spatial pattern of T. urticae in apple tree garden belonged to an aggregated distribution pattern. The aggregation intensity was the highest in upper and southern part of crown, and the lowest in its lower and inner part.The aggregation was due to the biological habits of T. urticae and environmental heterogeneity.No matter T. urticae was in the upper, middle, or lower crown of apple tree, its aggregation intensity was higher before first ten days of June,and then gradually decreased after the middle ten days of June.
    Effect of seedling stage shading on cotton yield and its quality formation
    ZHOU Zhiguo, MENG Yali, SHI Pei
    2002, (8):  997-1000. 
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    The effect of shading during symbiotic stage of inter cropped cotton and wheat on cotton yield and its quality formation was examined by simulated shading at the seedling stage of cotton.The results showed that the effect of shading on the cotton boll formation depended upon the position of frurting branch and fruiting bud.For the bolls at low(1～3 fruiting branches) and middle(4～6 fruitng branches) parts and the inside bolls(1～2 fruiting buds)on upper(7～9 fruiting branches)fruiting branch,shading favored boll formation, but for the outside bolls(≥3 fruiting buds),especially at the top fruiting branch position, shading was unfavorable to boll formation.The effect of shading on the weight of individual boll also depended upon the position of fruiting branch and fruiting bud,but shading did not affect the mean boll weight per plant. For seed cotton yield per plant,the inside boll yield of shaded low and middle fruiting branches was higher than the control, but that of the upper and top fruiting branches was just contrary,the yield of outside bolls of all branches was lower than the control.For the distribution of the inside and outside bolls, shaded cotton was 1:0.36,versus 1:0.58 for the control.For the yield distribution,shaded cotton was 1:0.42,versus 1:0.72 for the control.The effect of shading on the cotton fiber and seed quality was mainly restricted on the bolls of top fruiting branches and the outside bolls of upper fruiting branches.The results also showed that different cotton varieties were different in their shade tolerance,according to comprehensive analysis of the yield and quality formation, and the shade tolerance of variety Zh9418 was stronger than that of Zh19 and CAZ.
    Element contents of biofilm and suspended particulate in natural aquatic ecosystem
    WANG Wenjun, ZHANG Xuelin, WANG Wenhua, WANG Donghong
    2002, (8):  1001-1006. 
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    The element contents of biofilms and suspended particulates in the natural aquatic ecosystem were studied, and the samples were collected in Kunming Lake of the Summer Palace in July and October 1999. The biofilm samples were observed through microscope and scanning electron microscope. Various inhabitants such as sessile bacteria, algae, and protozoa existed in the biofilms. The dry weights of biofilms increased with the longer growth period. The dry weight of biofilm at 1 m depth of water reached to 5.19 mg穋m-2 after the growth time of 78 days. The element contents in biofilm, suspended particulate, and lake water were analyzed by ICP AES, and the results indicated that the element contents in biofilms were higher than those in the particulates. There was not an evident trend in the element contents of biofilms at the different water depth in the same site and growth time. At three sampling sites, the contents of Ca, Mg, K, Na, Al, Fe, and Sin the biofilm samples were similar between1 m and 1.5 m depth of water, but the contents of Mn, Sr, Ti, P, La, Co, Cu, Pb, Li, Ni, B, Ce, V, Be, and Cr were different in the biofilm samples of 1m and 1.5 m depth of water. The element contents of biofilms increased with the longer growth time.
    Root system development ability of several alfalfa cultivars in the hilly and valley regions of Loess Plateau
    GUO Zhenggang, ZHANG Zihe, XIAO Jinyu, HOU Fujiang, LU Ni
    2002, (8):  1007-1012. 
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    Afield study was conducted in the hilly and valley regions of Loess Plateau in Gansu Province to analyze the root system development ability of several alfalfa (Medicago sativa) cultivars.Eight introduced cultivars and one local cultivar were arranged in the same site.The secondary roots of alfalfa cultivars grew mainly from the taproot underground 10～20 cm depth,and there were no secondary roots below 50 cm depth.The total amount of secondary roots of Sandili and Ameristand 201 was the biggest,and that of Longdong alfalfa was the lowest. The volume and biomass of different cultivars were decreased from 0～10cm depth to below 50 cm depth, except those of Sandili and Ameristand 201 at 20～30cm depth was bigger than at 10～20cm depth. The biomass of Ameristand 201 was 170.54g and bigger than that of others, and that of Longdong alfalfa, which was 22.4% of Ameristand 201, was the lowest. According to cluster analysis on9 alfalfa cultivars, Sandili, Ameristand 201 and Amerigraze 401 were suitable for planting on the hills and valleys of Loess Plateau due to their root system development ability.
    Bio-geological temporal zonation and its agricultural significance
    REN Jizhou, LIU Xuelu, HOU Fujiang
    2002, (8):  1013-1016. 
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    Bio geological temporal zonation can be defined as a subsistent spatial temporal style that the organisms clip from a geographical zone to break through its limit,and extend their survival extent with the strategy of excluding the environmental period of time which is not suitable to live and intercepting it which is suitable. It is the consequence that organisms temporally adapt the heat distribution pattern caused by the rotation and revolution of the Earth. Bio geological temporal zonation relies on spatial zone,and the zonation spectrum changes in different spatial zones and has different basal heat zone.It appears as spiral loop based on its own spatial zone,and implies temporally seasonal change of the heat. Similarly, bio geological temporal zonation relies on the distribution process of water and heat under spatial and temporal scale.The component, range and hierarchy of zonation spectrum change with spatial and temporal scale, and organisms adapt this kind of change with different ecological strategy depended on different ecological strategy.Human being can tune up bio geological temporal zonation only in small scale.
    Research progress and trend on grassland agroecology
    REN Jizhou, LI Xianglin, HOU Fujiang
    2002, (8):  1017-1021. 
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    The connotation, progress, research frontiers and developmental trend of grassland agroecology are discussed in this paper.The interface theory, structure and function, coupling and discordance, and health assessment of grassland agroecosystems were recognized as the four research frontiers of the discipline. There exist three primary interfaces in a grassland agroecosystem, i.e.,vegetation site, grassland animal and production management. Research into a series of the ecological processes that occured at these interfaces is the key to revealing the features of the system behavior. There are four sections in a grassland agroecosystem, i.e.,pre-plant, plant, animal and post biotic sections. System coupling and discordance are the two important concepts to describe interactions among the production sections. System coupling among the sections can lead to system improvement by exerting the potential of system capacity. Health of an ecosystem is a reflection of its structure and function, and health assessment is a measurement of its orderliness and service value.
    Research directions of agroecosystem health in the early21st century
    LIANG Wenju, WU Zhijie, WEN Dazhong
    2002, (8):  1022-1026. 
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    Agroecosystem health refers to the state of an agroecosystem where it is free from‘distress syndrome’and to cope with stress, or capability to produce agricultural products in a sustainable way. At present, the research of agroecosystem health focuses on assessment methods, soil and water quality, human health, ecologically based pest managernent,integrated weed management, ecopathology, nematode communities, transgenic crops, agricultural input policy, landscape ecology and green food development. Firstly, the present state of agroecosystem health research was described; then a case study of agroecosystem health, biological indicators of soil health, was introduced; finally, the research directions of agroecosystem health were put forward. This paper could provide a basis for ensuring agricultural product security and increasing human health.
    Development of APSIM (Agricultural Production Systems Simulator) and its application
    SHEN Yuying, NAN Zhibiao, Bill Bellotti, Michael Robertson, CHEN Wen, SHAO Xinqing
    2002, (8):  1027-1032. 
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    Soil crop simulator model is an effective tool for providing decision on agricultural management.APSIM (Agricultural Production Systems Simulator) was developed to simulate the biophysical process in farming system,and particularly in the economic and ecological features of the systems under climatic risk.The current literatures revealed that APSIMcould be applied in wide zone,including temperate continental,temperate maritime,sub tropic and arid climate,and Mediterranean climates,with the soil type of clay,duplex soil,vertisol,silt sandy,silt loam and silt clay loam.More than 20 crops have been simulated well.APSIMis powerful on describing crop structure,crop sequence,yield prediction,and quality control as well as erosion estimation under different planting pattern.
    Advance in researches on vegetation cover and management factor in the soil erosion prediction model
    ZHANG Yan, YUAN Jianping, LIU Baoyuan
    2002, (8):  1033-1036. 
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    Vegetation cover and land management are the main limiting factors of soil erosion,and quantitative evaluation on the effect of different vegetation on soil erosion is essential to land use and soil conservation planning. The vegetation cover and management factor (C) in the universal soil loss equation (USLE) is an index to evaluate this effect,which has been studied deeply and used widely. However, the Cfactor study is insufficient in China. In order to strengthen the research of C factor, this paper reviewed the developing progress of Cfactor,and compared the methods of estimating C value in different USLEversions. The relative studies in China were also summarized from the aspects of vegetation canopy coverage, soil surface cover, and root density. Three problems in C factor study were pointed out.The autors suggested that cropland C factor research should be furthered,and its methodology should be unified in China to represent reliable Cvalues for soil loss prediction and conservation planning.
    Molecular response of plant to drought stress
    SONG Songquan, WANG Yanrong
    2002, (8):  1037-1044. 
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    Drought stress is a bottleneck factor for plant growth and development. Synthesis and accumulation of osmoprotectants,up regulation of gene expression implicated in repair of desiccation injury,free radical scavenging enzymes and late embryogenesis abundant(LEA)protein could increase the drought tolerance of plant. There are at least four pathways of signal transduction in plant subjected to drought stress,two are abscisic acid(ABA) dependent,and two are ABAindependent. In the signal transduction of plants encountered drought stress,two component His protein kinase could act as an osmosensor,and Ca2+ and inositol triphosphate(IP3)could be the second messenger for dehydration signaling. Transgenic plant is an excellent system in evaluating function of encoded protein.
    Review on water eco-environment in vegetation restoration in Loess Plateau
    HU Liangjun, SHAO Mingan
    2002, (8):  1045-1048. 
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    Water is the crucial factor influencing vegetation restoration and eco-environmental reconstruction in Loess Plateau region. In this paper,the previous studies on water eco-environment under vegetation construction were summarized from seven aspects,i.e.,soil water resource, background of soil water, dynamics of soil water, dry soil layer, relationship between soil water and vegetarian productivity,classification of soil water position, and strategy for vegetation construction.Meanwhile,some problems in the relevant researches were pointed out and discussed.
    Physiological indices of grazed grassland under health management
    HOU Fujiang, LI Guang, CHANG Shenghua
    2002, (8):  1049-1053. 
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    Evaluation of the function and health of grazed grassland is an important aspect of grazing ecology.Based on analyzing the physiological response of grassland to grazing,a double factor method of physiological threshold was developed.Physiological low limit (PLL),physiological ultimate limit (PUL), and duration ratio of regrowth to grazing stage (R/Gratio) were feasible to evaluate the sustainable management on the function and health of grazed grasslands. The reasonable threshold values of PLL, PULand R/Gratio could play an important role on the complete recovery of the function and health of grassland after grazing, which was the goal of sustainable management of grassland ecosystems.
    Application of fuzzy cluster in analyzing population dynamics of Chorthippus fallax
    LIU Changzhong, ZHOU Shurong, WANG Gang, WANG Wanxiong
    2002, (8):  1054-1056. 
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    The population dynamics includes quantity dynamics,space dynamics and temporal dynamics. They are interdependent and mutually influential.Fuzzy cluster analysis was carried out with the data of mean densities,indices of patchiness and occupied plot rates of Chorthippus fallax (Zubovsky)on Ganjia High Mountain Grassland in Xiahe County,Gansu Province. The results showed that the population dynamics of this grasshopper could be divided into four distinct periods,i.e.,the initial stage of hatching and the last stage of adult,the peak stage of nymph,the initial stage of adult,and the peak stage of first nymph and the adult. The peak period of nymph was in the middle ten days to the last ten days of July. In this period,the eggs were completely hatched,the population was mainly composed of nymphs of 2 and 3 instars,and the population size was related to the numbers and harmful levels of this grasshopper in the same year.Therefore,this period was the key time for population prediction and chemical control.
    Influence of soil humidity and vegetation coverage on wind erosion
    HAI Chunxing, LIU Baoyuan, ZHAO Ye
    2002, (8):  1057-1058. 
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    Wind erosion is becoming a constraining factor to agriculture and animal husbandry in the arid and semiarid area of Luanhe River. In this paper, wind erosion process was studied through simulation experiments. The results showed that soil humidity and vegetation coverage were the main factors affecting wind erosion.The wind erosion rate was decreased with increasing soil humidity and vegetation coverage,and hence, the wind erosion process was reduced by modulating soil humidity and vegetation coverage in human activities.