Table of Content

25 January 1999, Volume 10 Issue 1

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Articles

Indicative value of bryophytes on forest eco-boundary

Guo Shuiliang, Han Shijie, Cao Tong

1999, 10(1):  1-6. 

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Investigation of bryophytes at the edges of Pinus sylvestriformis and dark conifer forests as well as the ecotone from Vaccinium uliginosum shrub to Larix olgensis forest near round lake in Changbai Mountain revealed that the cover and diversity indices of bryophytes could be applied to identify the forest eco-boundary in the field. The relationships between these indices (y) with distance (x) on eco-boundary followed y=b·a^x. The informative values of the indices were calculated, and their ecological significance was also discussed.

Dynamic seedling life table of Liriodendron chinense

Fang Yanming, Cao Hangnan, You Luxiang

1999, 10(1):  7-10. 

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The emergence and survival rates of Liriodendron chinense in a seedling nursery were investigated, and dynamic life table was complied based on the periodical observation data. The result shows that the emergence rates of four kinds of provenance were quite low (1.64～3.05%), much lower than those of their full-seeds. The emergence rate of natural provenance was higher than that of cultivated provenance, but the rate of seedlings to full-seeds for the natural provenance was lower than that for the cultivated one. After a growth season, the rate of seedling survival to emergence was 16～27%, whereas that of the later generation of mating by Huangshan and Lusha provenance was 60%, significantly higher than that of their parents and other provenance. The size of seeds had no direct effect on seedling emergence and survival. The effect of genetic and environmental factors on seedling survival was also discussed. It is suggested that the low fitness of seeds and seedlings is one of the important factors causing the species being endangered.

Above-ground biomass and nutrient accumulation and distribution in different type Sonneratia carseolaris-Kandelia candel mangrove plantations

Liao Baowen, Zheng Dezhang, Li Yun, Zheng Songfa, Zheng Xinren, Huang Zhongqi

1999, 10(1):  11-15. 

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The total above-ground biomass was 38.527, 20.012 and 29.405t·hm^-2,respectively in Sonneratia carseolaris(6-year-old)-Kandelia candel(11-year-old) mixed plantation(type Ⅰ), S. carseolaris pure plantation(type Ⅱ) and K.candel pure plantation (type Ⅲ). In type Ⅰ, the biomass of tree layer accounted for 41.0%, shrub layer for 59.0%; in type Ⅱ, tree layer for 93.3%, shrub layer for 6.7%; and type Ⅲ, 100% for shrub layer. The annual mean net accumulation of dry matters was 4.701,3.380 and 2.673t·hm^-2, respectively for these three types. The total accumulation of 10 elements in three plantations was 765.570,343.935 and 555.886kg·hm^-2 respectively, signifcantly different with different stand types; among them, 41.8% distributed in the tree layer and 58.2% in the shrub layer for type Ⅰ, 92.3% in the tree layer and 7.7% in the shrub layer for type Ⅱ, and 100% in the shrub layer for type Ⅲ. The amount of nutrient elements absorbed for an unit net accumulated dry matter production and their return rate varied with stand types. In types Ⅰ,Ⅱ and Ⅲ, the total amount of 10 elements absorbed for producing a ton net accumulated dry matter was 39.860, 36.834 and 18.904kg respectively; and their return rate was 61.3%, 40.4% and 72.2%, respectively.

Effect of simulated drought inducement on drought-resistance of Chenopodium album

SUN Cunhua

1999, 10(1):  16-18. 

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To search after the approach of improving plant drought-resistance, the morphological and physiological indexes of drought-resistance of Chenopodium album were measured by five-years simulated drought inducement. The result shows that after simulated drought inducement, C.album could increase its leaf's typical drought-resistance characteristics: the blade thickness and succulence added, the specific leaf area, saturation osmotic potential and transpiration rate dropped, the osmotic regulation and water-holding capacities enhanced, and meanwhile, the critical saturation deficit value and transpiration efficiency increased. When the seeds with drought-resistance characterisitics, which were harvested after drought inducement, were planted in normal watered soil, the plants could keep the formed drought-resistance characteristics. The drought-resistance indexes were significant different(P<0.01) between induced and control plants when they were planted in critical drought-stressed soil. It is suggested that C.album is a species with variable drought-resistance, and its drought-resistance could be improved by drought training.

Effect of plant community succession on soil chemical properties in Tiantong, Zhejiang Province

Zhang Qingfei, You Wenhui, Song Yongchang

1999, 10(1):  19-22. 

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Comparative studies on the chemical factors in humus layer and 0～10 and 10～20cm soil layers at the main succession stages of evergreen broad-leaved forest in Tiantong, Zhejiang Province show that as succession proceeded, the total N content increased distinctly,but the contents of NO₃^--N,NH₄⁺-N and available N,P and K had no distinct increase. No obvious variation was found for soil pH. Soil organic matter content increased distinctly, and the amounts of humic acid(HA) and fulvic acid(FA) were relatively high in Castanopsis fagasii and C.fagasii＋Schima superba forests and lowest in bare land. The HA/FA in humus layer didn't show any obvious pattern, but decreased in 0～10 and 10～20cm soil layers. The results suggested that the secondary succession of evergreen broad-leaved forest could increase soil organic matter, and promote its mineralization and re-synthesis. On the other hand, the improvement of soil chemical properties could also provide better prerequisite for progressive succession of evergreen broad-leaved forest.

Correlation analysis of Aeluropus littoralis var.sinensis population density and biomass with its sexual reproduction characteristics

Wang Renzhong, Li Jiandong

1999, 10(1):  23-25. 

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Correlation analysis of Aeluropus littoralis var.sinensis population on Songnen salinized grassland shows that the density and biomass of sexual shoots, Re₁ and Re₂ had a significant positive correlation with the density and biomass of vegetative shoots, but a significant negative correlation with the density and biomass of stolons, and with the density and biomass of vegetative shoots of stolon.

Morphological characteristics and growth redundancy of spring wheat root system in semi-arid regions

Li Hua, Zhang Dayong

1999, 10(1):  26-30. 

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Six spring wheat cultivars bred at different years in semi-arid regions were selected to comparatively study the numbers and morphological characteristics of their seminal root systems, and to analyse the relationship of these indexes with crop drought-resistance and yield production. The results show that in semi-arid regions of loess plateau, the cultivars had a growth redundancy of root systems, which was unfavourable to the yield production. With the lapse of breeding years, the cultivars tended to have less root, shorter root length, larger active root absorption area, and smaller diameter of metaxylem vessel of seminal roots. These features made the cultivars bred at recent years use water more savingly at their earlier vegetative growth period, and conserve certain amount of soil water to satisfy their water needs at flowering and seed-filling stages, and hence, enhance their yield production.

Genetics of resistance of Oryza sativa to increased UV-B radiation and its physiobiochemical characteristics

Lin Wenxiong, Liang Yiyuan, Kilung Kim

1999, 10(1):  31-34. 

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The results show that UV-B (280～330nm) radiation strongly affected the growth and development of rice (Oryza sativa) seedlings, and thus, induced dwarf plants, wilted leaves, decreased chlorophyll content and dry matter of individual plants, and even death. The response of different rice genotypes to UV-B radiation was quite different. Among the three tested rice cultivars (HR, M63 and Hr), HR had the best resistance to UV-B radiation. The genetic analysis indicates that the resistance of rice UV-B radiation was the quantitative genetic trait mainly controlled by recessive polygenes. The biochemical analysis demonstrates that the activity of protective enzymes in rice seedlings treated with UV-B radiation significantly increased within 0～3days, then decreased gradually, and the content of malondialhyde (MAD) consequently enhanced. The resistant cultivar HR had a higher activity of protective enzymes than sensitive Hr, but a lower extent of lipid peroxidation, implying that the protective enzymes played an important role in resistance to UV-B radiation.

Impact of photoperiod-temperature conditions on male-sterile gene expression of photoperiod-temperature sensitive genic male-sterile wheat line ES-8

Zhou Meilan, Tang Qiyuan, He Juemin, Chen Jianming

1999, 10(1):  35-38. 

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Through changing sowing date, the impact of photoperiod-temperature conditions on the male-sterile gene expression of photoperiod-temperature sensitive genic male-sterile wheat line ES-8 was studied. The results show that in Changsha, when ES-8 was sowed from September 5 to October 15, the percentage of its pollen abortion and that of sterile plants were all 100%. When sowed from December 5 to December 15, its self seeding rate ranged in 71.6～72.7%, while from October 25 to November 25, it showed partly sterile and partly fertile. ES-8 had two critical dates of fertility alteration, one on October 25, from sterile to semi-sterile, and another on December 5, from partly fertile to completely fertile. The critical day-length of fertility alteration was less than 11.5 hours.

Mathematical description and three-dimensional reconstruction of maize canopy

Guo Yan, Li Baoguo

1999, 10(1):  39-41. 

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Based on Lang's principle, a spatial coordinate apparatus was constructed to determine the spatial coordinates of maize canopies. According to the determinations, a general quadratic equation was proposed to characterize the curvature and shape of maize leaf, and the coefficients of the equation were determined by least square regression, which makes it possible to describe the true structure of maize colony with a few parameters. In addition, a computer-based three-dimensional reconstruction of maize canopy was realized, which provided a new method for studying agroecological system.

Effect of organic materials on the composition characteristics of micro-aggregates in albic soils and their nutrient contents

Xing Xuerong, Li Fayun

1999, 10(1):  42-44. 

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A long term pot experiment shows that the composition of various particle sizes of micro-aggregates in albic soils could be altered through adding organic materials. The content of＜1μm and 1～2μm micro-aggregates was decreased, while that of 2～5μm and 5～10μm micro-aggregates increased. The contents of organic C and total N were markedly increased in all sizes micro-aggregates after organic materials amendment, which mainly distributed in small sizes of micro-aggregates. The P content was higher in small sizes of micro-aggregates, while the 10～50μm micro-aggregates had the least P content. There was a significant positive relationship between total P and Olsen P in ＜1, 1～2 and 5～10μm micro-aggregates. The effect of cow manure was better than that of wheat straw.

Evapotranspiration of soil-plant-atmospheric continuum - a simulation study with lysimeter

Chen Jianyao, Liu Changming, Wu Kai

1999, 10(1):  45-48. 

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Evapotranspiration (ET) and evaporation from ground water surface (Eg) are the two factors most difficult to determine in all components of field water balance. In regions with shallow ground water, the ground water plays an obvious role on supplying the soil water in unsaturated zone by capillary rise, which is of significant importance to the crop growth. The experimental data of water balance components and relevant parameters of soil-plant-atmospheric continuum model were obtained by lysimeter, Bowen ratio meter, hydraulic evapotranspirometer, etc. Based on the data measured by lysimeter, the simulation value of soil-plant-atmospheric continuum model was verified. The observed data of ET and Eg were comparatively analyzed with their simulation data, and the causes of difference between them were discussed.

A system dynamic model about the impact of rural industry on agroecosystems in southern Jiangsu Province

Chen Xin

1999, 10(1):  49-52. 

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A system dynamic model was used to analyze the impact of development in rural industry on agroecosystems in Wujiang city, a rural industrialized region of southern Jiangsu Province. The results show that there are both positive and negative impacts of rural industrialization on agroecosystem. The positive impacts display an increase of farmer's income and agricultural input, and a transference of promoting rural labors, while the negative impacts show a decrease of cultivated land and a result of environmental pollution. The negative impacts could be weakened or avoided, and the rural industry could be coordinately developed with agriculture, if a proper proportion of profit gained from rural industry would be used for agricultural development and environmental control after the actual strength of the rural industry was increased.

Relationships between soil water content and N₂O production

Huang Guohong, Chen Guanxiong, Han Bin, Oswald Van Cleemput

1999, 10(1):  53-56. 

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Studies on the effect of soil water content on N₂O production and emission indicated that different soil water contents induced different N₂O fluxes. It was demonstrated by the technique of acetylene inhibition, that around the period of sowing when the climate was dry and soil water content was low,N₂O production came from nitrification; after raining when soil water content was high, N₂O production mainly came from denitrification; and at medium water content, a half of N₂O emission came from nitrification, and another half from denitrification. It was suggested that the ways of N₂O production from upland fields mainly depended on the control and regulation of soil water.

Photochemical degradation of butachlor in different water

Hua Rimao, Li Xiangqiong, Li Xuede, Yue Yongde, Fan Defang

1999, 10(1):  57-59. 

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The photodegradation dynamics of herbicide butachlor in different water was studied under xenon lamp and high pressure mercury lamp illuminating. The result shows that under xenon lamp illuminating, the photodegradation rate of butachlor was in order of pure water＞river water＞pond water＞paddy water. Butachlor photodegraded slower under xenon lamp than under high pressure mercury lamp, and the speed was negatively correlated to the dosage. Moreover, the photodegradation rate was slowed down by filling nitrogen and de-oxygen.

Characteristics of diapause induction of cotton bollworm

Jiang Mingxing, Xie Liqun, Zhang Xiaoxi

1999, 10(1):  60-62. 

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Studies on the effect of temperature and illumination on the diapause induction of cotton bollworm (Helicoverpa armigera) population in Jiangsu show that temperature below 24℃ and illumination of < 12h were optimal for diapause induction. The critical length of illumination at 20,22,24 and 26℃ were 13h and 43min, 13h and 8min, 12h and 4min, and 12h and 7min, respectively. The fifth and sixth instar larvae were the sensitive stages of diapause indution. Their critical length of illumination was about 13h, which occurs in mid-September in Nanjing region, and the temperature in early September was found to be greatly related with the diapause rate.

Lifetable of natural citrus leafminer populationits —— its construction and analysis

Wang Liande, You Minsheng

1999, 10(1):  63-66. 

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Based on the sequence of its growth and development, the population of citrus leafminer (Phyllocnistis citrella) was divided into such stages as eggs, 1st instar larvae, 2nd instar larvae, 3rd instar larvae, 4th instar larvae, pupae and adults. The affecting factors of each stage were divided into relatively independent status. Based on field investigation and indoor experimental observation, the survivals of each stage were recorded, and their affecting factors were estimated by synthesizing Berryman and Gongxia methods, which would reduce the errors of the natural population lifetable due to generation overlapping. The lifetable of the 9th generation of the population was constructed, and the index of population tendency was 1.32. The analysis of important factors shows that the parasite enemies were the important factor affecting the natural population of citrus leafminer.

Trophic niche of flea in the southern slope of the Himalaya Mountains

Guo Tianyu, Xu Rongman

1999, 10(1):  67-70. 

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Studies on the trophic niche breadth and overlap of 46 species of flea in the southern slope of the Himalayas Mountains show that there were 23 species of flea only parasitized one kind of host, and their trophic niche breadth was the narrowest(B=0). Amphipsylla quadratedigita had the widest(B=0.6694) trophic niche breadth, and then, Neopaylla stevensi the second(B=0.4968). Among 12 dominant flea species lived on 9 small animal species, Xenodaeria telis, X. angustiproceria and Palaeopsylla tauberi mainly lived on Soriculus nigrescens, a kind of small insectivorous mammal, so the trophic niche overlaps among them were the highest.

Microecology of cotton seedlings I. Endophyte isolation and measurement of some biochemical characters of normal cotton seedling

Zhao Faqing, Ma Haiyan

1999, 10(1):  71-73. 

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503 strains of endophytic bacteria were isolated from four cotton varieties after a strict surface-sterilization among which, 102 strains were subordinate to Pseudomonas, Erwinia, Xanthomoas and Bacillus genera. The concentration of soluble proteins and the activities of superoxide dismutases (SOD) and peroxidases(POD) in the four cotton varieties were measured at three different growth stages, and the results show that the SOD activities tended to decrease from seeds, sprouts to seedlings. A significant difference of eigher soluble protein concentration or SOD activity was found among different varieties and different growth stages, and there was an interaction between cotton variety and growth stage.

Ecological distribution and biochemical properties of soil microorganisms in Gaoligong Mountains

Zhang Ping, Guo Huijun, Yang Shixiong, Dao Zhiling

1999, 10(1):  74-78. 

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This paper studied the quantities and some biochemical properties of soil microorganisms in natural forests of different elevations, collectively-owned forests representing varying degrees of anthropogenic disturbance and elevations, forests under different tenures, and soils of different landuse types in eastern slope of Gaoligong Mountatins. At the upper part of the mountain, the quantities and activities of soil microorganisms in natural forests increased with decreasing elevation, but at the lower part, those in collectively-owned forests were decreased with decreasing elevation, due to the increasing intensity and frequency of anthropogenic disturbance. The quantities and activities of soil microorganisms declined as the forest tenure varied from state-run to collective and to individual. After natural forests were replaced by pure plantations, the quantities and activities of soil microorganisms rapidly declined. However, in some cases, soils under cultivation appeared to be favorable to microorganism reproduction. In mid-elevation(about 2000m) natural forest soils, microorganisms were abundant and highly active. High elevation and low temperature was unfavorable to microbial reproduction and biochemical processes. Intensive felling and utilization of forests could also reduce the quantities and activities of soil microorganisms to a lower level.

Effects of salinity on VA mycorrhiza formation and of inoculation with VAM fungi on saline-tolerance of plants

Feng Gu, Bai Dengsha, Yang Maoqiu, Li Xiaolin, Zhang Fusuo

1999, 10(1):  79-82. 

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At different soil saline contents, the effect of inoculation with different vesicular-arbuscular mycorrhizal (VAM) fungal isolates on saline-tolerance of cotton, corn, soybean and melon plants were investigated with pot experiment. The results show that the infection rate of fungi to the four plants and the biomass of them were declined with increasing NaCl level in soil, while the dependency of these plants on VAM fungi were enhanced. At a given NaCl level, cotton, maize and soybean plants inoculated with VAM fungi had a higher biomass than that of non-mycorrhizal plants. With application of 0～3g·kg^-1 NaCl, the dry weight of cotton inoculated with M₁ isolate was increased by 4.6～80.9%; with application of 0～2.5g·kg^-1 NaCl,the dry weight of maize inoculated with M₁ isolate was increased by 20.0～109.6%; and with application of 1g·kg^-1 NaCl, the dry weights of soybean inoculated with M₁ and M₂ isolates were increased by 22.1% and 10.2%, respectively. Different fungal isolates had different effects on saline-tolerance of same plants, and same isolate had different effects on saline-tolerance of different plants. It is suggested that the VAM fungi-plant symbiosis might play an important role on plant survival on saline soil, and that inoculation with VAM fungi could enhance plant production on saline soil and reduce the loss of plant yield causing by salt.

Efficient expression of bacterial haloalkane dehalogenase gene in Arabidopsis thaliana

Hao Lin, John Mundy

1999, 10(1):  83-85. 

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This paper dealt with efficient expression of haloalkane dehalogenase gene(dhlA) from Xanthobacter autotrophicus in Arabidopsis thaliana. The dhlA was transferred and integrated into genomes of A. thaliana mediated by Agrobacterium tumefaciens, and homozygous dhlA seeds were obtained after several generations selection on a special medium. Northern blotting and gas chromatography (GC) assay shows that the dhlA was expressed efficiently, the amount of the enzyme accounted for 8% of total cellular soluble protein, and the enzyme activity reached 7.8 mU·ml^-1 cellular extract. The transgenic plants could not grow on the medium with 1,2-dichloroethane.

Fish diversity in Honghu Lake

Song Tianxiang, Zhang Guohua, Chang Jianbo, Miao Zhiguo, Deng Zhonglin

1999, 10(1):  86-90. 

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On the basis of fisheries resources investigations in 1992～1993 and in combing them with previous data in 1959 and 1982, the changes of fish species diversity and community structure diversity in Honghu Lake were analyzed. During the early years of blockage, the dominant fish species in Honghu Lake was lake-dwellers, and the river-lake migratory species and a few river-sea migratory species occupied certain amounts in catches. The dominants were the large and middle sized species, among which, the percentage of herbivorous species was 23%～35%, and carnivorous species around 10%～20%. In 1990s, the catches were dominated by Carassius orates, Pelteobagrus fulvidraco, Cultrichthys erythropterus and Hemiculter leucusculus, which were all small-sized ones. The majority in catches was omnivorous, and the herbivorous species almost disappeared in the lake. It was inferred that before the lake was blocked, there were over 100 fish species living in the lake, but the species reduced to about 50 species in 1990s, of which, only 30 or so could fulfill their life history in the closed lake environment. The species diversity indices and evenness were degraded to varying degrees.

Preliminary studies on the relative fatness and weight/length of wild and domestic Rana chensinensis from Liaoning

Wang Shoubing, Jiang Chaoguang, Qu Yunfang, Jing Zuoqin, Wu Qianhong

1999, 10(1):  91-94. 

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The study on relative fatness(K) and weight/length index(K_wl) of wild and domestic Rana chensinensis indicates that the K value of wild female R. chensinensis had no marked difference among different age groups, but that of male was opposite between sub-adult and adult groups; K didn't change evidently in different sex groups except the adult age groups. K_wl became larger with increasing age, and had a notable sex difference in all groups of wild R. chensinensis. The K value of one-year old domestic R.chensinensis had no evident change in variant sex groups, but K_wl had. Compared with that of the same age and same sex wild R.chensinensis, the K_wl value of the domestics was higher, but K had no evident difference. Because of K_wl being more sensitive than K in statistics, it is reasonable to use both of the two indexes to study the relative fatness of amphibian.

Effect of artificial wastewater on some eco-physiological characteristics of Avicennia marina seedlings

Chen Guikui, Chen Guizhu, Yuk-Shan Wong, Nora F.Y.Tam

1999, 10(1):  95-98. 

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A simulated study with different concentration of artificial wastewater shows that the wastewater with normal concentration and five times of it had no harmful effect, but promoted the growth of Avicennia marina seedlings. While with ten times of normal concentration, the wastewater had an obvious impact on the eco-physiological indexes of plant, e.g., the chlorophyll content, catalase activity, free proline content, water content and relative electric conductivity of leaves, the plant biomass, and the stem diameter and its hight growth, but the seedlings could still maintain its normal growth. It is indicated that A.marina had a stronger adaptability and endurance to wastewater.

Forest Eco-Network System in China

Peng Zhenhua, Jiang Zehui

1999, 10(1):  99-103. 

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Based on the current status of nature, economy and society, and in the light of interconnected patterns of material, energy and information flows, the Forest Eco-Network System in China (CFENS) is to be established to harmonizes the development of human, nature and society in this country, which is of integrity, multi-function, high efficiency and operability, and views the whole mainland as an ecosystem with different big parches consisting of different types of forests, grasslands, fields, barren hills and wastelands, waters, cities and villages. All parches are as individual ecological spots; human activity, precipitation distribution and heat quantity are as three major lines; and the functional characteristics of ecosystems are as surfaces. CFENS is formed by the combination of spots, lines and surfaces. The integral roles of forests should be maintained in a manner of safeguarding the long-term multi-functions, multi-effects and multi-directions, so that the water and soil loss, sandification and desertification in China could be controlled and improved, to decrease the damages from natural disasters of windy sand, drought and waterlogging, typhoon and sea tide, to enhance the capacity of territory security, to safeguard the Chinese people to live and work in peace and contentment, to enhance social civilization and progress, and to promote the sustainable development of resources, environment, society and economy.

Thinkings on flood in Yangtze valley and its countermeasures

Peng Zhenhua

1999, 10(1):  104-108. 

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The floods in Yangtze valley are of long-standing and induced by many factors. Besides global and regional environmental factors, the increasing human population is one of the most important affecting factors. Since Qing Dynasty, the forest ecosystems with water-conservation capacity have been seriously destroyed, which tends to be increasingly aggravated. The facts that forest ecosystems lost their water-conservation capacity, large amounts of topsoils were run off, and the riverbeds were leveled up, were the root causes of the exceptionally serious flood in 1998. It is suggested that the role of forest as the major part of terrestrial ecosystems should be fully played, and the key work in forestry should be adjusted. The functions of forest in improving environment, preventing water and soil loss and ensuring sustainable development should be placed in first importance. Around the central task of harmonizing the development of man and nature, and in combination with the problems challenging the development of economy and the conservation of natural resources in Yangtze valley, the sustainable development of its population, resources and environment should be scientifically programmed. The information system and decision-making support system for the sustainable development should be constructed, the management of forestry should be strengthened, and the governments should secure to gradually increase the fiscal investment on forestry year by year through laws and tax revenue, truly playing the key roles of forest in environment protection, territory security and sustainable development of society and economy.

Major issues in restoration ecology researches

Zhang Jia'en, Xu Qi

1999, 10(1):  109-113. 

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The basic concepts and their connotations of restoration ecology and its general situation of researches, as well as the objectives, principles, procedures and techniques of ecological restoration, were discussed in this paper. It is suggested that the restoration ecology research should give consideration both to the basic theories including the succession of ecosystem and its damage process and reaction mechanism under disturbance, and to the applied techniques, including the restoration of soil, water body, atmosphere and vegetation, the conservation of bio-diversity, and the assemblage and integration of ecosystem. The ecological restoration and reconstruction is a systematic engineering, which is in the light of ecological principles and by the certain biological, ecological and engineering techniques, to artificially control the key factors and processes of ecosystem degradation, and regulate and optimize the flow processes and their spatial and temporal sequences of matter, energy and information among the ecosystem and its environment, by the aim of successfully restoring the structure, function and ecological potentials of degraded ecosystem to their original or higher level.

A review on ecological models of soil N mineralization

Mu Xingmin, Fan Xiaolin

1999, 10(1):  114-118. 

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The mineralization of soil organic nitrogen is one of the most important factors reflecting soil nitrogen-supply capability and one of the hot subjects of soil ecology in home and abroad, which could be referred as a function of soil organic content, duration of its mineralization, and soil environmental factors affecting the process of mineralization. There are three basic model types of soil nitrogen mineralization, namely, the kinetic, thermodynamic and empirical types. Soil temperature, moisture, pH and organic N forms are the soil environmental elements which impact the mineralization process and could be quantified.

Disaster-causing characters and disaster-reducing strategies of crop pests in China

Dai Xiaofeng, Ye Zhihua, Cao Yazhong, Guo Yuyuan

1999, 10(1):  119-122. 

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Crop pest is an important biological disaster in agricultural production in China, which has become one of the key factors limiting the sustainable development of high yield, good quality and high efficient agriculture. This paper gave a review on the roles of integrated control techniques in crop pest disaster reduction in the past decade. China is facing several serious challenges in crop pest control, such as continuous pest occurrence, less developed key control techniques, poor forecasting techniques and weak basic researches, etc., and strategies and approaches to continuously control crop pest disaster are given as follows: to increase research input; to explore disaster causes and regulations; to study mid-term and long-term forecast methods; to develop key techniques of integrated control; to pay more attentions to applied research of high-technology, etc.

Review on bioassay methods for allelopathy research

Zeng Rensen

1999, 10(1):  123-126. 

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Bioassay is an important link in allelopathy study, but lacks standardized methods. This paper reviewed the widely used bioassay methods, their suitability and the factors affecting determined results, such as collection methods of allelochemicals, influences of microbes, solution osmotic pressure, and selection of receptors. Suggestions on the expression of bioassay results are also provided.

Nodulation of flavonoid-stimulated rhizobia on oilseed rape and nitrogen fixation

Hu Xiaojia, Zhang Xuejiang, Edward C. Cocking, Gordon S. Webster

1999, 10(1):  127-128. 

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Flavonoid-stimulated rhizobia were used to inoculate the seedling roots of oilseed rape, making the rhizobia intrude into the roots, form para-nodules and fix nitrogen. The results show that rhizobia stimulated by flavonoid could effectively invade root cells and form para-nodules containing rhizobia, with nodulation rate of 100%. The strains isolated from para-nodules of oilseed rape could successfully re-inoculated to original host. The determination of antiserum show that the strains could agglutinate with test rhizobia. Electron microscopic observation shows that the cells of para-nodule were full of bacteria. The activity of N-fixing enzyme in para-nodules determined by acetylene reduction method was 142.01 nmol C₂H₄·g^-1·h^-1.