Table of Content

10 August 2005, Volume 24 Issue 08

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Pollination biology of endangered Magnolia sieboldii

WANG Lilong, WANG Guanglin, LIU Dengyi, WANG Xingming, SHEN Zhangjun

2005, (8):  853-857. 

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Bases on fixed plants observation,this paper studied the flowering phenology of wild and artificial Magnolia sieboldii populations.The results showed that the blooming time lasted about 20 days,from the middle and last ten day of May to the middle and last of June.Full blooming time was from June 1 to 5,and the flower parts changed distinctly in blooming time.Pollens were not mature at beginning flowering,when the pistil had already matured,with pistil stem elongated.After about 20 hours,the stigmas which had already turned black at basal part were wet.After about another 40 hours,pollens turned to mature and anther became splitting.The stigmas at basal and middle parts of the receptacle received more pollens than those at the apical.Pollen lost vigor after 6 days,with 65% of pollination rate.The mean number of per accepted pollen stigma was 3.5,and the rate of fruit set was 13.5% under natural conditions,20.1% in planting,11.3% as taking out the perianth,10.7% if there was no stamen,and 25.0% in condition of pollination by manpower.The pollination efficiency passed by the insects of M.sieboldii was low because of fewer visiting insects and fewer visiting frequency.Bee and a species of Aphididae were the most effective pollinators.Cornus controversa,whose flowering phase was the same as M.sieboldii,had a competition with the passing pollen insects.The insect-visiting rate was affected by several environment factors such as light,temperature,rain and altitude,and the visitation peak was different in different habitats and under different weather conditions.The brighter the sky was,the higher the visitation rate and visiting peak came earlier.

Piuns sylvestris community on Honghuaerji sandy land and its relationship with environmental factors

LIU Kang, WANG Xiaoke, YANG Fan, GUO Ran, WU Qingbiao

2005, (8):  858-862. 

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Based on field investigation and employing two-way indicator species analysis (TWINSPAN) and canonical correspondence analysis (DCCA),this paper classified and collated the Pinus sylvestris community on Honghuaerji sandy land.Quantitative analysis was carried out on the spatial pattern of the community and its relationship with environmental factors.The results showed that P.sylvestris community could be classified into 6 types.Altitude,physiognomy,canopy of community,overall contents of soil C and N,and chest area of arbor influenced the plant community and its spatial pattern distinctly.The spatial pattern of the community species presented obvious collective pattern in DCCA taxis,which could be divided into different swarm and reflect significant correlation with environmental factors.Environmental factors contributed to the vegetation distribution pattern were quantitatively analyzed,among which,topography was the strongest variable.The reasons which were not able to explain were discussed.

Growth status of man-sowed Alstonia scholaris in southern Yunnan,China

HU Zongda, WU Zhaolu, ZHOU Yuanqing, ZHANG Zhiming

2005, (8):  863-866. 

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Based on the field- measured data of the base diameter,diameter at 50 cm from the bottom,total height,height from the base to the first branch,substations,branches in each substation,and crown diameters of man-sowed A.scholaris,and employing double analysis,variance analysis,and compare means methods,this paper studied the growth status of the tree in three areas with different environmental conditions.The results indicated that A.scholaris growth had highly positive correlations with mean annual temperature,mean temperature of the coldest month,and relative humidity,but a highly negative correlation with altitude.

Effects of Cistanche deserticola inoculation on undergrowth vegetation of natural Haloxylon ammodendron forest

GUO Quanshui, TAN Deyuan, WANG Chunling, SHI Zuomin, MA Chao

2005, (8):  867-871. 

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In this paper,the effects of Cistanche deserticola inoculation on the undergrowth vegetation of natural H.ammodendron forest were studied in low-lying land,slow and gentle desert,and semi-mobile dune,the three different habitats of natural H.ammodendron forest at the eastern edge of Zhunger Basin in Xinjiang Autonomous Region,.The results showed that C.deserticola inoculation had different effects on the vegetation composition,plant number,vegetation coverage,species diversity,biomass,and naturally regenerated sapling under natural H.ammodendron forest.In the natural H.ammodendron forest in low-lying land,the amount of lost vegetation was 41 000 ind·hm^-2,accounting for 18% of total undergrowth vegetation before inoculation,the loss of biomass was 35.64 kg·hm^-2,accounting for 14.9% of the total,and the amount of lost sapling was 1320 ind·hm^-2,accounting for 24.2% of the total.In the natural H.ammodendron forest in slow and gentle desert,the loss of plant individuals under the forest was 26000 ind·hm^-2,accounting for 49% of total amount of undergrowth vegetation before inoculation,the loss of biomass was 39.87 kg·hm^-2,accounting for 19.0% of the total,and the amount of lost sapling was 345 ind·hm^-2,accounting for 18.8% of the total.In the natural H.ammodendron forest in semi-mobile dune,the loss of plant individuals under the forest was 2000 ind·hm^-2,accounting for 5% of total number of plants before the inoculation,the loss of biomass was 9.98 kg·hm^-2,accounting for 6.0% of the total,and the amount of lost regenerated H.ammodendron sapling was 256 ind·hm^-2,accounting for 3.8% of the total.In the survey quadrate directly influenced by inoculation,the number of plants was reduced by 26%～53%,overall vegetation coverage reduced by 46%～52%,species diversity decreased by 5%～13%,biological advantage increased by 2%～6%,naturally regenerated H.ammodendron sapling reduced by 40%～75%,and biomass loss of aerial and ground parts under the forest lost by 25.2%～55.7%.

Floristic characteristics of seed plants in Ziwuling of Loess Plateau

ZHANG Xibiao, SHANGGUAN Zhouping

2005, (8):  872-877. 

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Ziwuling(107°30′～109°40′E,33°50′～36°50′N) is situated in the center part of Loess Plateau.the transitional zone between semi-humid and semi-dry climate,and its flora belongs to Loess Plateau subregion,North China region,Sino-Japan forest subkingdom,Holarctic kingdom.There are 689 species of seed plants belonging to 361 genera and 94 families,among which,big families and big genera play important roles.The Ziwuling's flora could be divided into 15 distribution types and 12 subtypes,among which,the North temperate,old world temperate,pantropic,and e-Asia are important types.The analysis of the Ziwuling's basic floristic characteristics of seed plants showed that the flora was comparatively rich in species,geographical elements were diversiform,transitional characters of geography were obvious,and temperate components were dominant.The northern flora was different from the southern one,but there was no evident distinction in the dangling flora.

Soil fractal features of subalpine coniferous forests in Western Sichuan under different anthropogenic disturbances

LIAO Yongmei, CHEN Jjingsong

2005, (8):  878-882. 

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Fractal theory which is used to study the natural figures and images with self-similarity but without characteristic length offers an effective tool to quantitatively investigate the complex systems such as soil.This paper studied the fractal features of soil particles and micro-aggregates under the subalpine coniferous forests with different intensity anthropogenic disturbance in Miyaluo area of West Sichuan,and approached the effects of the disturbance on the forest soils attributed to different fractal dimensions.The study introduced a new way to research the recovery and reestablishment of subalpine coniferous forests.

Effect evaluation of air negative ions under different vegetation arrangements in Nanning city

FAN Yamin, HE Ping, LI Jianlong, SHEN Shouyun

2005, (8):  883-886. 

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In this paper,the concentrations of air negative ions above urban area,suburb green space,and farmland in Nanning city were measured.The results indicated that from the viewpoint of air negative ions,the air quality was in order of large scale suburb green space > farmland > urban area.Vegetation with multi-structure was the best,followed by vegetation with simple structure,and single vegetation pattern.Creek and waterfall could raise the concentration of air negative ions effectively.The concentrations of air negative ions increased with ascending altitude and canopy density,and fluctuated with season.

Organic carbon fractions and aggregate stability in aquatic soil under different fertilization

YANG Changming, OUYANG Zhu, DONG Yuhong

2005, (8):  887-892. 

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As an essential indicator of soil quality,soil organic carbon (SOC) and its fractions play an important role in many soil chemical,physical,and biological properties.A field experiment was conducted to determine the effects of different nutrient regimes on aquatic soil organic carbon fractions and aggregate stability in Northern China Plain.Seven nutrient regimes were installed:(i) control,(ii) NP,(iii) NK,(iv)PK,(v)NPK,(vi) NPK+S (wheat straw),(vii) NPK+M (farmyard manure).The results showed that soil total organic carbon (TOC) and total nitrogen (TN) were markedly higher in combined application of organic and chemical fertilizers than in chemical fertilization.By fractionalizing SOC,it was observed that in comparing with treatment NPK,treatment NPK+M had significantly higher soil easily-oxidizable C (EOC),particulate organic C (POC),light fraction organic C (LFOC) and water-soluble organic C (WSOC),being increased by 23.8%,39.9%,42.5% and 32.1%,respectively.The proportions of LOC,POC,LFOC and WSOC to TOC in chemically fertilized soil,especially in treatment PK,were observably lower than those in organically fertilized soil.Incorporation of organic sources into aquatic soil showed the highest microbial biomass C (MBC) and mineralizable organic C (MNC),followed by treatments NPK,NP and NK,and treatments PK and CK had the lowest MBC and MNC.A combined application of organic and inorganic fertilizers increased the content of > 250 μm water stable aggregate (WSA) significantly (P<0.05),but decreased the clay dispersion rate (CDR).Correlation analysis showed that WSA was significantly (P<0.01 or P<0.05) and positively related to the determined organic fractions,and positively related to LFOC,POC and MBC,with the correlation coefficient r=0.87^**,0.92^** and 0.84^**,respectively.There were significantly negative correlations of clay dispersed rate (CDR) to TOC,POC and LFOC,with r=-0.70^*,-0.78^* and -0.73^*,respectively.

Effects of seed soaking with La³⁺ on seed germination and seedling growth of rice

ZHANG Jie, LIU Dengyi, HUANG Yongjie, LIU Xueyun

2005, (8):  893-896. 

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An experiment with JinYou No.63 rice seeds was installed to study the effects of La³⁺ soaking on the seed germination and seedling growth of the rice.The results showed that within the range of 120 mg稬^-1,La³⁺ increased the vigor of seed and its proteinase,amylase and lipase activities,and promoted the growth of plant shoot and root.The optimal concentration of La³⁺ was 10 mg稬^-1.When the La³⁺ concentration was higher than 30 mg稬^-1,seed germination and seedling growth were depressed.The effect of lanthanum on root was much more apparent than on shoot,and the sensitivity of enzymes to La³⁺ was in the order of proteinase>lipase>amylase.

Effects of road on landscape and its ecological risk assessment:A case study of Lancangjiang River valley

LIU Shiliang, YANG Zhifeng, CUI Baoshan, GAN Shu

2005, (8):  897-901. 

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Road and road networks bring forth many ecological effects,as they run through all kinds of landscapes,while road ecological risk analysis is to comprehensively assess various potential ecological effects and their accumulative effects trough pattern and process research.Focused on the impact of roads on landscape,the road effects were divided into construction period and passage period,with two indexes based on different effects on pattern and process to describe the effects put forward and the comprehensive ecological risk index deduced.Taking three case areas at upper,middle,and lower reaches of Lancanjiang River valley as examples,this paper analyzed that the road impact on landscape,and calculated their ecological risk index.The results indicated that though ecological risk distributed differently in each area,road density had high positive linear correlations with risk indexes.

Emergy analysis of agricultural eco-economic system in Chaoyang City,Liaoning Province

FU Xiao, WU Gang, SHANG Wenyan, LIU Yang, WANG Hongchang, FU Haiwei

2005, (8):  902-906. 

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By the method of emergy analysis,this paper studied the emergy input and output of agricultural eco-economic system in Chaoyang City,semi-arid region of western Liaoning Province,and analyzed the development status of the system through calculation and comparison.The results showed that the local ecological environment was worsened by the excessive utilization of natural resources,which resulted in the severe loss of non-renewable natural resources and the emergy output from the eco-system.Insufficient use of renewable organic energy was the other main cause of the resources waste and environment destruction in the area.

Land cover and landscape pattern changes of costal wetland in Yellow River Delta

GUO Dufa

2005, (8):  907-912. 

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Regional land use and land cover change is an important part of global change.Based on the land cover data in 1986,1996 and 2001,and employing ARC/INFO software and landscape ecology method,this paper studied the past 15 years' land use and landscape pattern changes (LULPC) in coastline buffer zone (3 km) of Bohai Sea,with the affect degree and scope analyzed.The results showed that spatially,the land use degree comprehensive index (Y) of Bohai Sea coastline buffer zone in 1986 and 2001 increased with the distance to Bohai Sea coastline (X),with the linear correlation equations Y₈₆=7.728X+96.584,R=0.979^**,and Y₀₁=19.156X+112.2,R=0.983^**.While in 1996,the index did not change dramatically.Temporally,the index increased from 1986 to 1996,as well as from 1996 to 2001.Other landscape pattern indexes except dominance index had no significant correlation with the distance to the Bohai coastline.

Effects of retinoic acid on regenerated distro-proximal formation of Eisenia fetida

XIAO Nengwen, GE Feng, LIU Xianghui

2005, (8):  913-916. 

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To prrobeinto the effects of exogenous retinoic acid (RA) on the regeneration of invertebrate,this paper measured the survival rate,biomass,and regenerated length of E.fetida segments amputated from its different position and treated with RA.The results showed that RA had little effect on the survival rate of anterior segments,but a higher effect on that of posterior segments.After treated with RA for 30 days,the regenerated length was shorter than the control.Exogenous RA disrupted and delayed the regeneration of earthworm and the formation of its head,but not the posterior regeneration.It was suggested that the regional specification during regeneration was distro-proximal,and retinoic acid played an important role in pattern formation during regeneration.

Ecological disturbance of field Phyllotreta striolata population occurrence

FU Jianwei, CHENG Qin, Lin Zeyan, YOU Minsheng

2005, (8):  917-920. 

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With yellow trap board as monitoring tool,this paper studied the quantitative dynamics of striped flea beetle (SFB) P.striolata adults in field.The results showed that from Nov.2002 to Oct.2003,there were four insect occurrence peaks and three vales,which meant that SFB occured a year around,with no evident overwintering phenomena.The occurrence of SFB population was not significantly affected by rainfall or temperature,while joint effect of the two factors was existed.The quantitative dynamics of SFB were various on different host plants,as well as in different growth stages of vegetables,indicating the host discrimination of SFB adults.

Optimization of RAPD conditions for soil microbes

JIAO Xiaodan, WU Fengzhi, GAO Haijun

2005, (8):  921-924. 

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With orthogonal experiment,this paper studied the effects of the concentrations of Mg²⁺,dNTP and primer,the anneal temperature,and the extending time and cycling times on RAPD of soil microbes.The results showed that the feasible PCR reaction system for soil microbes should be carried in 25 μl volume,which was composed of 7 ng soil microbial DNA template,20 pm random primer,l.5 uTaq enzyme,3.0 mmol·L^-1 Mg-CL₂,and 0.2 mmol·L^-1dNTP.The PCR reaction procedure was firstly,keeping 94 for 3 min to make soil microbial DNA denatualize followed by 39 cycles,each including 94 for 1 min,37 for 40 s,and 72 for 1.5 min,and finally,keeping 72 for 7 min for extending.

Effects of environmental factors on key carbon-nitrogen metabolizing and antioxidizing enzyme activities of Amaranthus

SUI Yihu, ZHU Shidong, ZHANG Zixue, HU Deping, SHU Yingjie

2005, (8):  925-929. 

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This paper studied the physiological indexes of Amaranthus cultivated in a big vinyl house in early spring under different combinations of five levels of sunlight intensity,air temperature,soil temperature,carbon dioxide concentration,and nitrogen fertilization.The results showed that for carbon and nitrogen metabolism,nitrate reductase activity (NRA) had significantly positive correlations with sunlight intensity and air temperature at different nitrogen application levels,and the order was A (no net and no film)>B (no net and one layer film)>C (one layer net and one film)>D (two layers net and one film)>E (three layers net and one film).Compared with A (control),the NRA of the other four treatments was decreased by 6.45%,34.21%,61.54% and 63.78% respectively.CO₂ concentration and air and soil temperature affected the activity of PEPC significantly.Of all treatments,the PEPC activity in treatment B was the highest,and that of B,C,D and E was 59.69%,28.57%,-10.71% and -17.86% higher than A,respectively.For the metabolism of active oxygen system,SOD activity was positively correlated with sunlight,but negatively correlated with CO₂ concentration,and the order was A>B>C>D>E.POD activity was negatively correlated with sunlight and air temperature,with the order of A<B<C<D<E,and CAT was positively correlated with sunlight and air temperature,with the order of B>A>C>D>E in all combinations.The enzyme activities of B with 20 kg·667 m^-2,17 800 lx sunlight intensity,21.2 ℃ soil temperature,23.5℃ air temperature and 1 500 μmol CO₂·mol^-1 were the most cooperative,which made the Amaranthus cultivation technical system of "high yield,high efficiency and excellent quality" be possible.

Optimization of main designed parameters of artificial rapid infiltration land treatment system-COD removal

GUO Wei, LI Peijun, TAI Peidong, YIN Wei, LI Haibo, XU Huaxia

2005, (8):  930-934. 

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In this paper,the Artificial Rapid Infiltration System (ARI) was simulated under laboratory conditions,and the main designed parameters including the component of artificial soil (quartzite/soil) and running circle (flooding time and flooding time/drying time) for the highest removal rate of COD were optimized. The stable removal rate of COD was obtained by the reciprocal equation method,and the model of multi-linear regression equation was established by stepwise regressive method.The optimizing parameters of ARI were x₁ (quartzite/soil)=1.073,x₂ (flooding time)=4 h,and x₃ (flooding time/drying time) =1/8,and the highest theoretical removal rate of COD was 84.73%,which was accordant with the practical value,indicating that the method was feasible.The model also suggested that there was an interaction between the component of artificial soil and the flooding time /drying time.

MDA accumulation and antioxidation capacity of two Elsholtzia splendens populations under copper stress

XIE Mingji, KE Wenshan, WANG Wanxian, XIONG Zhiting, WU Mingyu, CHEN Jianjun

2005, (8):  935-938. 

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Elsholtzia splendens is the most widely distributed copper-tolerant plant along the middle and lower streams of Yangtze River.Two populations of E.splendens,one from Chimashan mining area and the other from a normal soil of Hongan,all in Hubei Province,were chosen to investigate their MDA accumulation and antioxidation capacity.The results showed that E.splendens from normal soil accumulated more MDA than that from mining area,which indicated the serious peroxide harm to the plant.The concentrations of AsA,GSH and T-AOC were much higher in the plant from mining area than that from normal soil,suggesting that E.splendens from mining area had been evolved to copper-tolerant ecotype,and low molecular antioxidant played an important role in tolerance of the plant.

CH₄ emission flux from early rice field of laterite and its affecting factors

DU Yaodong, LIU Jinluan, YANG Ning, WANG Tianlong, MAK Khalil, MJ Shearer

2005, (8):  939-942. 

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The measurement of CH₄ emission flux from an early rice field of laterite in Guangdong Province with closed chamber technique showed that the CH₄ emission had a significant seasonal pattern,with three peaks at late tillering,booting-heading and milky stages,and an average of 5.7 mg穖^-2穐^-1.During the period of measurement,there was a significantly positive correlation between CH₄ flux and soil temperature at 5 cm and 10 cm soil depths,and a significantly negative correlation between CH₄ flux and soil Eh.No significant correlation was found between CH₄ flux and soil pH or water depth.

Research advances in forest landscape ecology

BAI Jiangli, PENG Daoli, YU Xiaohong, ZHENG Xiaoxian

2005, (8):  943-947. 

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This paper reviewed the four domains in forest landscape and its dynamics research,i.e.,forest landscape management and environmental quality control,relationship between forest landscape pattern and its function,simulation and decision-making models of forest landscape ecology processes,and riparian landscape ecology research.Several main problems in these research domains were pointed out,i.e.,insufficiency of basic research,backwardness of methodology,and finity of case study,which needed to be improved.The prospective development of forest landscape ecology research was also put forward.

A review on persistent soil seed bank study

YAN Qiaoling, LIU Zhimin, LI Rongping

2005, (8):  948-952. 

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Soil seed bank includes all live seeds existed both in litter and in soil,which is simply classified into transient soil seed bank with seeds germinated within a year of initial dispersal,and persistent soil seed bank with seeds remained in soil more than one year.Even giving ideal germination conditions such as season,temperature and moisture,some seeds in soil,including persistent soil seed bank,still remain dormant.Investigation of soil seed bank has always been paid attention by plant ecology,and has been an active research area.Persistent soil seed bank confers the potential for regeneration in circumstances where unpredictable disturbance happened to the established vegetation temporally and/or spatially,and accordingly,plays a key role in vegetation restoration and management after disturbance.Researches on persistent soil seed bank can make the content of biodiversity abundant,and provide more ways to understand vegetation regeneration deeply.This paper reviewed the methodologies of persistent soil seed bank study,the classification and indication factors of persistent soil seed bank,and the significance of its study.The problems and further work of the study were pointed out.

Effects of urbanization on biodiversity:A review

LI Junsheng, GAO Gixi, ZHANG Xiaolan, ZHENG Xiaomei

2005, (8):  953-957. 

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Urbanization is being developed rapidly in the world.Urban development not only seriously changed the living environment of organisms,but also caused the rapid variance in biodiversity.In this paper,the characters of urban habitats were summarized,with the effects of urbanization on biodiversity reviewed.The pattern of biodiversity distribution along a gradient from village to urban was analyzed,and further study on the relationship between urbanization and biodiversity was suggested.

Landscape ecological planning of green food base

GAO Qiong, HU Yuanman, ZHENG Qinyu, LI Yuehui

2005, (8):  958-962. 

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Based on the concepts of landscape ecological planning and green food,this paper discussed the significance of landscape ecological planning in constructing green food base,with emphasis on the basic principles complied in the course of green food base-landscape ecological planning,such as sustainable development and resources use,systemtic integration,adjusting measures to local conditions,landscape heterogeneity,etc..Taking the landscape ecological planning of green food base in Fushun city as an example,the paper analyzed the basic operational processes of the planning,i.e.,confirmation of the scope and objective,ecological investigation,spatial pattern and ecological process analysis,ecological suitability evaluation,functional zoning,etc..The successful experience of the planning was identified,which provided theoretical and methodological references for other areas to develop sustainable green food industry and ecological agriculture in the future.

A preliminary study on weed-suppressing rice breeding

LU Decheng, ZHOU Shaochuan, LI Hong, HUANG Daoqiang

2005, (8):  963-966. 

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A set of new breeding materials derived from PI312777 were established by using PI312777 rice accessions as weed-suppressing parents,and a rice breeding nursery was founded.Weed-suppressing rice plants were selected by evaluating their weed-suppressing effects and focusing on their agronomic characters in the field,and new varieties (or lines) of weed-suppressing rice were developed by evaluating the allelopathic potential of rice plants with applying specific secondary metabolite markers at late generations (after F4).A rice breeding method for weed-suppressing in South China,in which,main evaluation in the field and assistant evaluation by applying secondary metabolite markers,was mentioned.

Determination of aflatoxins in maize by combining high performance liquid chromatography with florisil column

GAO Junxia, NI Yuwen, WAN Haolei, LI Guifang, LIU Zuoxin

2005, (8):  967-969. 

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Aflatoxins in maize were determined by combining high performance liquid chromatography with florisil column in this paper.The main components,aflatoxin B₁,G₁,B₂ and G₂,were separated in short time (10 min).The regressive equations and detection limits of them were given.Some existed problems were analyzed based present study.Peak sequences were discussed according to the results.It may contribute to make the method perfected in the practice.

Multiple headspace solid phase microextraction and analysis of volatiles from Arabidopsis green leaf

DENG Xiaojun, DU Jiawei

2005, (8):  970-974. 

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Headspace solid phase microextraction (HS-SPME) has been widely used in qualitative characterization of volatile or semi-volatile organic compounds released by plant samples.The quantitative determination of volatile components in headspace analysis was proved to be difficult due to the so-called "matrix effect" and the complicated diffusion and adsorption processes of analytes.In this paper,a direct quantitative method for monitoring volatiles from Arabidopsis thaliana green leaf was presented,based on multiple HS-SPME.The chemical composition of emissions from Arabidopsis was firstly investigated by using SPME coated with DVB/CAR/PDMS fiber.After the extraction parameters were optimized,the total mass of three main green leaf volatiles was calculated by using the peak area of the first single extraction,combined with the calibration of standard solution.The absolute mass of three green leaf volatiles was from 78.6 to 158.4 ng穏^-1.

Single cell gel electrophoresis technique and its applications in soil ecotoxicology

LIN Aijun, GENG Chunn, ZHU Yongguan, TONG Yiping

2005, (8):  975-979. 

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The single cell gel electrophoresis technique (comet assay) is a simple,sensitive,reliable,and rapid method to detect DNA damage in eukaryotic cells.The paper reviewed the principles,advances and methodology of comet assay,and its applications in soil ecotoxicology,with its development in future predicted.Nuclei embedded in low-melting-point agrose in an agar gel sandwich migrated towards the anode under an electrical current with a different rate from that of DNA strands presented the appearance of a "comet".Different techniques are available with different sensitivity to detect DNA damages such as double strand breaks,single strand breaks,delay DNA repair sites and alkali labile sites.The basic procedure of the technique included cell suspension preparation,slide preparation,lysis,unwinding,electrophoresis,neutralization,dying and view.The method has been widely used in several areas in the past few years,especially in genotoxicology research in environmental biomonitoring.

Tourism development in cropland-converting to woodland (grassland) district of Loess Plateau

HUANG Jinhuo

2005, (8):  980-984. 

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The environment of cropland- converting to woodland (grassland) district of Loess Plateau is relatively fragile,and the local economy is undeveloped.It is very important to choose a reasonable model for its economic development,which deeply relates the effect of "developing the West" strategy.Based on the survey of the district,the models of converting cropland to woodland (grassland) were analyzed.The results showed that the models of present environment protection and environment economy did not consider enough the advantages of local community,which in turn resulted in the inefficiency for sustainable development.The model of eco-tourism could solve these problems.With the resources and sustainable systems analyzed,it was indicated that the resources,location,policy,traffic,and service facility were all enough for tourism development.The phases and tasks of tourism development and the frame of zoning were put forward.