Table of Content

08 May 2007, Volume 26 Issue 05

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Articles

Changes of soil biological activity in desertification process of Horqin sandy grassland.

CAO Cheng-you¹; ZHU Li-hui²; FU Yao¹; CHEN Jia-mo¹; CUI Zhen-bo¹;GAO En-liang¹

2007, 26(05):  622-627 . 

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With the adjacent plots of fixed, semi-fixed, and moving sand dunes in west Horqin sandy land as test objects, this paper studied the change characteristics of soil microbial biomass, enzyme activities and nutrients as well as the relationships among the three indices in the process of desertification. The results showed that soil nutrient contents, microbial biomass, and enzyme activities all decreased gradually with increasing soil depth. In the process of desertification, soil nutrient contents had a heavy loss, and soil microbial biomass C , N and P as well as the activities of urease, protease, saccharase, phosphatase, dehydrogenase, polyphenol oxidase, nitrate reductase decreased significantly. Soil biological activity was very sensitive to desertification, and its decrease was the quickest in the phase from fixed to semi-fixed sand dune. There existed significant correlations among soil microbial biomass, enzyme activities and nutrient contents.

Spermatophyte flora of Dafang Fokienia hodginsii National Reserve.

CHEN Kun-hao;LUO Qiang;LIU Ci-chang;SHAO Shu-gang

2007, 26(05):  628-633 . 

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Based on specimen collection and identification;and referring related literatures,this paper studied the composition of spermatophyte flora and its geographic elements in Dafang Fokienia hodginsii National Reserve. The results showed that the spermatophyte flora in the reserve belonged to the Central China region;and was the core of Sino-Japan forest flora. There were 132 families,476 genera and 1 060 species of wild spermatophyte. The basic features of the flora were abundant in species and complex in geographical elements;with a relatively higher connection on family level by 61.11% and a relatively higher connection on genus level by 55.61%. The origin of the flora was very ancient,with many monotypic genera and oligotypic genera;and of typical calcicoles.

Changes of forest resources type and structure in Lushuihe Forest Bureau of Changbai Mountains.

JIANG Ping^1,2，3; YU De-yong³; DONG Bai-li¹; YE Ji¹; YAN Xiao-wang⁴; WU Gang³

2007, 26(05):  634-638 . 

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By using remote sensing and GIS, this paper studied the temporal changes of forest resources in Lushuihe Forest Bureau of Changbai Mountains. The results showed that in 1985, mature broadleaved and coniferous forests occupied 68.52% of the forest resources, but in 1999, medium-age broadleaved and coniferous forests occupied 65.96%. During the fifteen years, forest area increased by 17.6%, and the proportion of mature forests decreased from 68.52% to 48.72%. The forest resources in the study area changed greatly under the effects of human activities and natural factors. Some forest management measures adopted were not rational, and harmful to the progressive succession of forests. The volume structure of the forests was relatively single, and some forest management measures should be modified, with the cultivation of more local forest species to be strengthened.

Responses of vegetation in ecotone of North Yinshan Mountain area to precipitation.

XIA Hong¹; FAN Jin-long²; WU Jian-jun¹

2007, 26(05):  639-644 . 

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The eco-environment in northern China is vulnerable and changeful, and drought is one of the main affecting factors. By using NOAA/AVHRR NDVI and SPI (standard precipitation index) as the proxies of vegetation activity and water resource, the effects of precipitation on the vegetation change in agro-pasture ecotone of North Yinshan Mountain area was investigated. The correlation coefficient between monthly NDVI in growth season (May to October) and corresponding one month SPI (1-SPI) was calculated, and a 1983—2003 data series was created.It was found that the correlation coefficient between NDVI and 1-SPI during May-October differed with months, but was generally the highest in May. The velocity of NDVI change (VNDVI) could indicate the vegetation growth rate, and had influence on the responses of vegetation to precipitation.

Effects of elevated ozone concentration on Ginkgo biloba photosynthesis.

ZHANG Wei-wei¹; ZHAO Tian-hong¹; WANG Mei-yu¹; HE Xing-yuan²; FU Shi-lei²

2007, 26(05):  645-649 . 

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With open-top chamber, this paper studied the photosynthetic characteristics of Ginkgo biloba, a main greening tree species in Shenyang, under elevated ozone concentration. The results showed that after 50 days exposure to 80±8nmol·mol^-1 elevated ozone, the net photosynthestic rate of G. biloba leaf decreased significantly, with a decrement of 33.90%. The leaf carotenoid content increased notably, while chlorophyll content changed a little, with the ratio of chlorophyll a to chlorophyll b declined first and ascended then. No significant change was observed in leaf soluble sugar, while soluble protein and starch contents decreased obviously with time. The leaf malondialehyde (MDA) content was increased with time, and the increment was 79.53% on the 80th day of exposure. The decline of G. biloba photosynthesis had no correlation with the changes of chlorophyll content, but correlated markedly with membrane lipid peroxidation. The decline of the photosynthesis caused the decrease of leaf soluble protein and starch contents, resulting in a slow growth of the tree.

Growth and physiological responses of Bruguiera gymnorrhiza seedlings to waterlogging stress.

LAI Ting-he; HE Bin-yuan

2007, 26(05):  650-656 . 

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From September 2004 to September 2005, the effects of waterlogging on the seedlings growth and physiological characteristics of Bruguiera gymnorrhiza were studied in the diurnal tide region of Yingluo Bay in Guangxi.Eight tidal flat altitude (TFA) treatments were installed, with the surface plane of seedlings substrates ranged from 320 to 390 cm and a 10 cm difference between each other. The growth characteristics and some physiological parameters of the seedlings were measured, and the results showed that both the lower and the higher TFA treatments promoted the longitudinal development of stem significantly, while moderate TFA treatments did not. The seedlings in moderate TFA treatments had fewer knots on the stems. The leaf number, leaf area and leaf conservation rate presented congruously a rapid decline as the TFA fell. A slight promotion to the chlorophyll contents was found in lower TFA habitats, while a stronger promotion occurred in the higher ones. The Chl-a /Chl-b ratio in lower TFA treatments was higher than that under higher TFAs, while the SOD and POD activities in leaves and roots were both promoted significantly in lower TFAs. At the same TFA, the activities of SOD and POD in roots were several times higher than those in leaves. Higher TFA habitats were more beneficial to the biomass accumulation of the seedlings, especially for their leaves. The biomass partition tended to transfer from leaf to stem with increasing degree of waterlogging stress. Seedlings death occurred in all treatments, but the survival rate decreased from 73.6% to 35.0% as the TFA lowered. It was suggested that the critical tidal level for B. gymnorrhiza in terms of forestation with hypocotyls directly in Beibu Gulf region was 21 cm higher than the altitude of local mean sea level.

Lost value of Chinese grassland ecosystem due to degradation: An estimate based on remote sensing.

WANG Rui-jie¹; QIN Zhi-hao^1,2; JIANG Li-peng¹; YE Ke¹

2007, 26(05):  657-661 . 

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Chinese grassland ecosystem plays an important role in economic development and ecological services of this country. In recent decades, this ecosystem is facing challenges of degradation due to heavy population pressure and overgrazing. Based on the conventional evaluation on the lost value of rangeland due to degradation, an improved model was used to reevaluate the lost value with the MODIS data of 2003 and 2005, and the spatial distribution pattern of the lost value of Chinese grassland ecosystem was developed. The results showed that from 2003 to 2005, the total lost value of Chinese grassland ecosystem services due to degradation was 66.603×10⁸US$. The area with a lost value of 0-1000 US$·km^-2 was about 1/4 of the total area of measured grasslands, and that with a lost value of 1 000-3 000 US$·km^-2 was about 1/3 of the total. The seven provinces of West China including Inner Mongolia, Xinjiang, Tibet, Qinghai, Gansu, Yunnan and Sichuan had a lost value of 52.219×10⁸US$, accounting for 78.41% of the total, among which, Inner Mongolia had the largest loss, occupying 25.89% of the total.

Hydrogen production from molasses fermentation by a novel hydrogen-producing strain Ethanoligenens sp. B49.

XU Li-ying^1，2; REN Nan-qi¹; WANG Ai-jie¹; WANG Xing-zu¹;JIE Yong-feng2

2007, 26(05):  662-667 . 

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With used molasses as substrate, this paper studied its zymolytic characteristics by a novel hydrogen-producing strain Ethanoligenens sp. B49, and the effects of nitrogen nutritional condition on the hydrogen yield. The results showed that B49 could use molasses as the substrate for its cell growth when the COD was within the range of 10.3-20.6 g·L^-1, and the cell growth rate and hydrogen yield increased with increasing COD. When the COD of molasses was above 20.6 g·L^-1, the growth of Ethanoligenens sp. B49 was limited , and the hydrogen yield was decreased gradually with increasing COD. When the COD of molasses was up to 41.2 g·L^-1, cell growth was restrained. The feasible COD of molasses for Ethanoligenens sp. B49 was 20.6 g·L^-1, and the addition of organic nitrogen could significantly increase the hydrogen production by Ethanoligenens sp. B49 via molasses fermentation. The effect of added organic nitrogen was decreased in the order of yeast extract>beef extract>peptone>carbamide, and the optimal concentration of yeast extract for B49 growth and hydrogen yield was 4 g·L^-1. At the optimal concentrations of molasses and yeast extract, the hydrogen yield was increased from 44.82 mmol·L^-1 to 78.97 mmol·L^-1, with an increment of 76.2%.

Effects of burial and coating on acorn survival of Quercus variabilis and Quercus serrata under rodent predation.

CHENG Jin-rui^1,2,3; XIAO Zhi-shu¹; ZHANG Zhi-bin¹

2007, 26(05):  668-672 . 

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Rodent predation on acorn is very intensive, which affects the regeneration of plant. Quercus variabilis and Q. serrata are the dominant tree species in evergreen broadleaved forests in Southwest China. They are not only of great economic value, but also favorable for local forestation. In this paper, their acorns were under four treatments,i. e. , coated but not buried, coated and buried, buried but not coated, and neither coated nor buried, and the fates of these acorns were followed up. The results showed that the median survival time of the acorns differed significantly with the treatments. The survival duration of coated and buried acorns was significantly longer than that of the acorns neither coated nor buried. Burial significantly reduced the predation of acorn by rodents, and coating effectively protected the acorns from predation. Both coating and burial increased the probability of acorns survival and seedlings recruitment. The results of this study could be used for artificial seeding plantation to increase the survival rate of forestation.

Relationships between forest insect pest occurrence area and meteorological factors in Great Xing’an Mountains of Heilongjiang Province, Northeast China.

WANG Juan^1,2; JI Lan-zhu¹; Marina Khomutova³

2007, 26(05):  673-677 . 

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Based on the meteorological data of six observatories in the Great Xing’an Mountains of Heilongjiang Province, a total of seven meteorological factors affecting the occurrence area of forest insect pest were selected, and their correlations were analyzed, aimed to investigate the effects of meteorological factors on the insect pest population quantity, and to build the forecast equation of the insect pest occurrence area. The results showed that the meteorological factors closely related to the insect pest occurrence area were the yearly accumulated temperature of ≥10℃, yearly precipitation and dryness, with the Pearson coefficient being 0.701, -0.814 and 0.937, respectively. The analysis on the relationships between extreme climate phenomena and insect pest occurrence area suggested that the overcast and rainy days in spring had a significant positive correlation with the insect pest occurrence area, while the coldness in winter and spring had no direct effect on it.

Effects of pesticides on Paramecium caudatum individual’s growth and population dynamics.

GU Yan-fang^1，2; LIU Ai-lian¹;DING Sheng-yan^1，2; XIAO Bao-lin²; PENG Ling²; SU Jiang-feng²

2007, 26(05):  678-681 . 

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With continuous culture in laboratory, this paper studied the individual’s growth and population dynamics of Paramecium caudatum under the stress of methamidophos, fen-propathrin and 2,4-D buiylate, with the population growth curves analyzed by using Logistic model. The results indicated that methamidophos and fen-propathrin could alter the cell size and form of P. caudatum.After treated with different concentrations of test pesticides, the population growth curves were all sigmoid, and accorded well with Logistic model (R²＞0.8). The K value was decreased significantly under the stress of pesticides, and the maximal population growth rate was lower under methamidophos and fen-propathrin stress than under 2,4-D buiylate stress and the control.

Fish fauna and its ecological types of Qingshui River in Guizhou Province, Southwest China.

DAI Ying-gui¹; CHEN Yi-feng²

2007, 26(05):  682-687 . 

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A total of more than 2500 specimen of fish belonging to 71 species (subspecies) in the Qingshui River, Guizhou Province were collected in 2002—2004, and their ecological habits were surveyed. Of the 71 species (subspecies), 52 species (subspecies) including Cobitis sinensis, Culter oxycephaloides, Coreosiniperca roulei and Leiocassis longirostris were newly recorded in the river, and Paracobitis variegates, Leptobotia elongate, Pseudohemiculter hainanensis, Glyptothorax fukiensis, and Pelteobagrus eupogon were first found to be distributed in the Yuanjiang River system. Based on the historical records and this survey, it was concluded that the fish fauna in the Qingshui River comprised 86 species (subspecies), 57 genera, 13 families and 4 orders. Of the 86 species (subspecies), only Clarias fuscus was exogenous, and the rest were indigenous. The fish fauna in the river presented the characters of dominant by indigenous species and companying with special species and vulnerable and endangered species, and of complex components and sharing the fish species with that in the Pearl River system. The fish in the Qingshui River belonged to different ecological types in migration, feeding, reproduction, and inhabitation.

Effects of phenanthrene toxicity on histopathology of Brachydanio rerio gill and liver.

WU Ling-ling¹; CHEN Ling¹; ZHANG Ya-lei²; LI Jian-hua²; ZHAO Jian-fu¹

2007, 26(05):  688-692 . 

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In this study, Brachydanio rerio was exposed to three concentrations of phenanthrene (0, 0.05 and 100.0 μg·L^-1) for 36 days,and the histopathological effects of phenanthrene on B. rerio gill and liver were examined under light microscope. The results showed that at 0.05 and 100.0 μg·L^-1 of phenanthrene, the most common changes of B. rerio gill were epithelial hypertrophy and edema. The thickening of filament epithelium and the lifting of lamellar epithelium were the other histopathological effects of 100.0 μg·L^-1 phenanthrene. When exposed to 0.05 μg·L^-1 phenanthrene, the hepatic lesions of B. rerio were characterized by the hypertrophy of hepatocytes and vacuolization. After exposure to 100.0 μg·L^-1 phenanthrene for 36 days, the shape of hepatocytes was irregular, some nuclei were atrophy and deformation or in a lateral position close to the cell membrane, hepatocytes were highly vacuolated, and focal necrosis occurred after cytolysis and karyolysis. 0.05 μg·L^-1 of phenanthrene already had toxic effect on B. rerio gill and liver, and the damage was more severe when exposed to 100.0 μg·L^-1 of phenanthrene. The impairment of B. rerio gill and liver was increased with increasing phenanthrene concentration.

Environmental evolution of Longgan Lake sediments recorded by carbon and nitrogen isotopes.

ZHOU Zhi-hua^1,2; LI Jun¹; ZHU Zhao-zhou³

2007, 26(05):  693-699 . 

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Through the determinations of δ¹³C_org, δ¹⁵N, total organic C, total N and C/N ratio in Longgan Lake sediments, this paper analyzed the sources of sedimentary organic matters in the Lake, variations of lake productivity, and evolution process of sediment since 1948. The results showed that the sedimentary organic matters mainly derived from native aquatic organic matters. The aquatic plants were float grasses accompaning with algae. Land matters and city pollutants had little influence, while large amounts of applied chemical fertilizers had great effects on the lake sediments. With the input of nutrients, the primary productivity of the lake increased, and algae began to flourish. In the sedimentary history, algae started to grow earlier in site L₂ than in site L₁, but the sediment in site L₁ could fix more nutrients.

Landscape pattern change in Minjiang River upper reach under effects of anthropogenic activities.

HU Zhi-bin; HE Xing-yuan; LI Yue-hui; ZHU Jiao-jun; LI Xiao-yu

2007, 26(05):  700-705 . 

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By using multiple data resources and 3S techniques, this paper analyzed the landscape patterns of Minjiang River upper reach in 1986, 1995 and 2000, with the focus on the responses of main landscape types to the anthropogenic activities. The results showed that in the study area, grassland and forestland were the main landscape types, occupying 96.1%, 96.38% and 95.23% of the total in 1986, 1995 and 2000, respectively, and other landscape types were scattered in them. These two landscape types controlled the landscape pattern change and ecological processes of the whole study area. Different landscape types had great differences in their responses to anthropogenic activities intensity (AHI). Low AHI was beneficial to the landscape restoration of forestland; high coverage grassland was sensitive to all grades AHI except grade 1, and only strictly decreasing AHI could maintain its landscape; while medium coverage grassland was sensitive to lower and medium AHI, with the landscape degraded and the area decreased. High intensity management activities could change the landscape patterns to a desirable direction.

Urban landscape pattern of Xi’an City based on GIS.

ZHAO Xiao-yan; LIU Kang; QIN Yao-min

2007, 26(05):  706-711 . 

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With the QuickBird RS images of the Three Circles of Xi’an City as the basis and under the support of GIS, a 20-m unit was taken as the appropriate grain size based on the sensitivity analysis of different grain size landscape pattern indices, and the present landscape pattern of the city was analyzed. The results indicated that in this city, residential and industrial areas were concentrated and artificial landscapes were congregated, which affected the natural ecological processes. Greenbelts and water bodies were highly fragmented, and distributed separately. The landscape structure within the 1st circle was unreasonable, different type landscapes between the 1st and 2nd circles had no uniform distribution, and the potential economic and ecological effects of land use between the 2nd and 3rd circle were quite high. It was suggested that the urban space structure and distribution of Xi’an City should be adjusted, and the continuity of landscape ecological processes and patterns should be maintained from the aspects of green belt landscape construction and water system protection.

Comparison of runoff coefficient of watersheds with different landscape structure in Heishui River basin of Minjiang River upper reach.

XU Shen-lai^1,2,3;LI Xiu-zhen¹;HU Yuan-man¹;HE Xing-yuan¹;ZHOU Hao⁴

2007, 26(05):  712-717 . 

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By using the 1988—2002 data of annual mean precipitation and evapotranspiration in the Heishui River basin of Minjiang River upper reach, and with the help of GIS, a comparison was made on the annual mean runoff coefficient of the watersheds with different landscape structure in the Heishui River basin. The results showed that the magnitude of the annual mean runoff coefficient was in the sequence of forest-shrub watershed<forest-grass-shrub watershed<forest watershed<forest-grass watershed, which was related to the land cover type, mean altitude and windward slope direction. For forest watershed and shrub watershed, the annual mean runoff coefficient was affected by mean annual precipitation, mean annual evapotranspiration and mean slope grade. For forest-grass and forest-grass-shrub watersheds, the annual mean coefficient was affected by mean annual precipitation , mean annual evapotranspiration, and the ratio of forest/grass area.

Emergy analysis of agroecosystems in Shandong Province of China.

WANG Jian-yuan; XUE De-qiang; TIAN Xiao-ping; CHEN Yan-chun

2007, 26(05):  718-722 . 

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In this paper, the emergy input and output, environmental loading, and running effect of agroecosystems in Shandong Province were quantitatively analyzed, aimed to better evaluate the agricultural utilization of solar energy resources and the sustainable development of agriculture in this province. The results showed that in emergy input, the contribution of freely used environmental emergy, unrenewable industrial emergy, and renewable organic emergy was 21.0%, 54.5% and 24.5%, respectively. The net emergy yield rate was 5.31, environmental loading was 6.42, emergy density was 7.22×10¹¹ sej·m^-2, and the sustainability index based on emergy analysis was 1.52. The agroecosystems in Shandong Province had higher efficiency of emergy output and better effect of running, but were still at the stage of petroleum agriculture, which should be paid great attention to. To promote the sustainable development of agriculture in this province, the investment proportion of fossil energy should be reduced gradually, and the research and extension of agricultural science and technology should be strengthened.

Assessment of ecosystem integrity in headwaters of Yangtze River.

YAN Nai-ling; ZHAO Xiu-hua

2007, 26(05):  723-727 . 

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The concept of ecosystem integrity was proposed to protect the biological and ecological resources against the interference of human activities, and has being turned into a basis of public policy and decision making in environmental issues. Many of the ecosystem management and planning activities are taking ecosystem integrity as the principle and goal. In this paper, a hierarchical ecosystem framework of the headwaters of Yangtze River was established, and an indices system for the assessment of the ecosystem integrity of the headwaters was developed. According to the assessment results of ecosystem integrity, the headwaters of Yangtze River could be divided into three units, i. e. , ecologically good, ecologically vulnerable, and to be ecologically restored with priority.

Effects of Leonurus heterophyllus extracts on Oncomelania hupensis and its esterase isoenzyme.

HU Xing-yi¹; TANG Wan-peng¹; WANG Wan-xian²; ZHANG Xu-dong³

2007, 26(05):  728-731 . 

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The study showed that both the aqueous and the stachydrine extracts of Leonurus heterophyllus’s root, stem and leaf had good effect on controlling Oncomelania hupensis, but their toxic activity was somewhat slower than that of niclosamide. The effect was in the sequence of leave＞stem＞root. After treated with the aqueous extracts of L. heterophyllus, the esterase isoenzyme activity of O. hupensis was higher than that of the control in 1-2 days, but decreased markedly in 3-4 days. During this process, some new bands of the enzyme appeared, and some bands disappeared. This change was mainly occurred in positive area, which accorded with the normal pathological reaction.

Regional planning of functional zones for coal exploitation based on resources and environment protection.

GENG Hai-qing

2007, 26(05):  732-736 . 

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In the traditional planning of coal exploitation, no sufficient consideration was made on the development of recycling economy and the protection of eco-environment, which was disadvantageous to the regional scale environment protection. Based on the integrated analysis of regional ecological condition, geographical characteristics and economic development level, and from the viewpoint of resources and environment protection, the coal mine-enrichment areas in China were planned into three functional zones, i. e. , key exploitation zone, moderate exploitation zone, and restrictive exploitation zone, and further divided into five typical zones, i. e. , Loess Plateau hilly and gully zone, plain mine-grain complex zone, Yunnan-Guizhou mountainous zone, Northwest desert grassland and East Mongolia forest grassland and meadow grassland zone, according to their physical geographic and ecological characteristics. Different countermeasures were brought forward to solve different environment problems in each zone.

Identification, monitoring and forecasting of Locusta migratoria manilensis outbreak and its affecting ecological factors.

JIANG Yan¹; HUO Zhi-guo¹; LI Shi-kui¹; WU Rui-fen²; DU Hai-jiang³

2007, 26(05):  737-742 . 

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Based on previous researches, this paper analyzed the disaster-pregnant environments and key ecological factors of Locusta migratoria manilensis outbreak in China. The results showed that there was a close relationship between Locusta migratoria manilensis outbreak and climate change. The distribution of the locust was limited by climatic zones, and its outbreak centers had the similar disaster-pregnant environmental characteristics. The outbreak and development of the locust was closely related to the thresholds of the main ecological factors such as hydrological and climate conditions, soil, and vegetation. Traditionally, the forecasting of locust outbreak was paid more attention to the correlativity between the quantitative dynamics of the locust and related ecological factors, but recently, a medium- and long term forecasting was approached based on large-scale climatic observation, with modern technologies such as remote sensing adopted in monitoring large-scale locust outbreak.

Roles of vegetation in wind erosion control: A research review.

HE Shan-feng^1,2; JIANG De-ming¹; Alamusa¹

2007, 26(05):  743-748 . 

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Wind erosion is a leading factor of land desertification and sandstorm disaster, and one of the most serious environment problems in the world. Many researches indicated that planting vegetation is an economical and effective measure in controlling wind erosion. This paper discussed the mechanisms and affecting factors of vegetation in wind erosion control, and introduced three main approaches, i. e. , wind tunnel test, field investigation, and model simulation. Some problems needed to be solved and improved in the further study were put forward.

Reductive dechlorination of polychlorinated biphenyls by zero-valent metal.

HE Na^1,2; LI Pei-jun¹; FAN Shu-xiu^1,2; REN Wan-xia^1,2; ZHANG Hai-rong¹

2007, 26(05):  749-753 . 

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Polychlorinated biphenyls (PCBs) are the toxic organic compounds widely and massively distributed in the environment, and have great environmental impacts. Many scientists endeavored to devise remediation techniques to effectively treat the PCBs-contaminated matrices including water, oil, sediment, and soil. This paper summarized the research progress and development trend of reductive dechlorination of PCBs by zero-valent metal. Zero-valent metal can effectively promote the reductive dechlorination of PCBs under high temperature or the existence of Pd, Pt, Ni and Cu as catalyzers. There are three possible pathways of PCBs dehalogenation by zero-valent metal. The first pathway involves the metal directly, and the reduction occurs by electron transfer from Fe⁰ surface to the PCBs. The second pathway involves Fe²⁺,which is an immediate product of corrosion in aqueous systems. Dissolved Fe²⁺ is a reductant capable of causing PCBs dehalogenation. The third athway for reductive dehalogenation by iron involves the hydrogen produced as a product of corrosion with water. In this paper, the effective, low-cost, and facile characteristics of PCBs reductive dechlorination by zero-valent metal were commented, and the further research areas were prospected.

Evaluation method of agro-ecosystem vulnerability.

ZHAO Yan-xia¹; HE Lei²;LIU Shou-dong²; LIU Wen-quan³; HE Yong⁴; ZHANG Jian-ping⁵

2007, 26(05):  754-758 . 

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Evaluation of agro-ecosystem vulnerability is of significance in mitigating the negative impacts of climate and environment changes. Many researches aiming at different ecosystems have been made in recent ten years, but no generally recognized and identical methods were put forward. The farming-pastoral ecotone in northern China is a typical agro-ecosystem vulnerable region. Taking this area as an example and based on the analysis of the main factors affecting the vulnerability, an evaluation indices system of agro-ecosystem was built, with 17 indices of 4 types included. The weight of each index was determined by using analytical hierarchy process, and the method for comprehensively and quantitatively evaluating the vulnerability of agro-ecosystem was established based on the principles of fuzzy estimate.

Ecological security evaluation of Chaohu Lake basin based on attribute recognition model.

WU Kai-ya¹; ZHANG Li-bing²; JIN Ju-liang²; SUN Shi-qun³

2007, 26(05):  759-764 . 

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By using AHP weight method and attribute recognition model, a comprehensive ecological security evaluation of Chaohu Lake basin and its secondary appraisal units was made, aimed to build an efficient model for basin ecological security evaluation. The results indicated that the ecological security level of Chaohu Lake basin declined in the sequence of Hefei, the basin as a whole, Juchao, Wuwei, Hexian, Hanshan, Shucheng, Lujiang, Feidong, and Feixi. Among them, Hefei and Feixi were in grades Ⅳ and Ⅰ, respectively, and other districts all fell into grade Ⅱ. Because of its explicit meanings and simple computational process, this model could sort and rank the test objects according to their ecological security level, and be applied to the comprehensive evaluation of other ecological systems.

Species diversity under effects of temporal heterogeneity of habitat destruction.

LIU Hui-yu^1，2; LIN Zhen-shan^1，2

2007, 26(05):  765-770 . 

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Habitat destruction is one of the main factors inducing the decrease of species diversity. By using a non-autonomous multi-species competition-coexistence model and Shannon diversity index, the responses of different metapopulation species diversity to the temporal heterogeneity of different rates and velocities of habitat destruction were analyzed. The results showed that under instantaneous destruction, the species diversity decreased rapidly first, recovered to a definite extent sooner, and went to equilibrium then. Under continuous and complete destruction, habitat destruction rate had obvious effects on species diversity when q was lower, but few effects when q was higher. Under continuous and partial destruction, the higher velocity the habitat destruction,the greater amplitude the species diversity had, which was not beneficial to the stabilization of community.

Development models of ecotourism in wetland areas.

XU Fei-fei¹; WAN Xu-cai¹; YANG Da-yuan²

2007, 26(05):  771-774 . 

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With the rapid development of ecotourism and owing to the special features of wetland resources, wetland ecotourism has become a research focus. It was considered that different types of wetland should have different ecotourism development models, and the establishment of these models should be based on the analyses of historical and cultural background, integrity of ecosystem, competitive capability of market, and regional economy. In this paper, an analysis model with 16 second class indicators for the development of wetland ecotourism was built, and used in a case study of Yancheng Red Crowned Crane Wetland Nature Reserve in Jiangsu Province, from which, the advantages and disadvantages of developing ecotourism could be found in time. The further development direction of ecotourism was discussed.