Table of Content

03 April 2007, Volume 26 Issue 04

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Articles

Effects of applying indole-3-acetic acid （IAA） and potassium on carbon and nitrogen metabolism of flue-cured tobacco after topping

XU Zi-cheng¹; ZHANG Ting^1,2; LU Xiu-ping³; ZHANG Yan-jun¹

2007, 26(04):  461-465 . 

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This paper studied the carbon and nitrogen metabolism of flue-cured tobacco under effects of six treatments, i . e . , no topping (T₁), topping (T₂), topping+topdressing K₂SO₄ (T₃), topping+spraying IAA （indole-3-acetic acid）1 time (T₄), topping+topdressing K₂SO₄+ spraying IAA 1 time (T₅), and topping+topdressing K₂SO₄+ spraying IAA 2 times (T₆). The results showed that from the day of topping to the following 30 days, the amylase activity of flue-cured tobacco had a trend of decreasing first and increasing slightly then, while invertase (INV)activity decreased gradually. The activities of these two enzymes were the highest in T₆ and the lowest in T₁, with a significant difference. Except in T₁ , the starch content in all treatments increased gradually, and the total sugar content increased first but decreased then. At the 30th day after topping, the starch and total sugar contents were the highest in T₆, and the lowest in T₁. Nitrate reductase (NR) activity and protein content had a decreasing trend with the growth of tobacco, and were the highest in T₆ at the 30th day after topping. Treatment T₅ had the highest ratio of NR/INV after 30 days of topping. Spraying IAA at the top of tobacco plant on the day of topping combined with K topdressing could promote the growth and the carbon and nitrogen metabolism of flue-cured tobacco.

Accumulation features of nitrogen and phosphorus in plants of Liangzi Lake wetland

XIONG Han-feng¹; HUANG Shi-kuan¹; CHEN Zhi-ping¹; LIAO Qing-zhou²; TAN Qi-lin³; WANG Yun-hua³

2007, 26(04):  466-470 . 

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Different plant species in Liangzi Lake wetland had different accumulation features of nitrogen and phosphorous. Floating-leaved macrophyte accumulated the largest amount of nutrients, with an average content of total nitrogen and phosphorus being 29.07 and 9.53 g·kg^-1, respectively. The plant nitrogen and phosphorus contents were in the order of phytoplankton>floating-leaved macrophyte>submersed macrophyte>rice>emerged macrophyte. The nitrogen and phosphorus accumulation in plant was in the order of floating-leaved macrophyte>emerged macrophyte>submersed macrophyte>swamp plant>rice. Hydrophyte could absorb more nitrogen and phosphorus, and the nitrogen absorption by various kinds of plant in the wetland was greater than that of phosphorus absorption.

Niche characteristics of main plant species in desert areas of north Gulang County, Gansu Province

ZHANG De-kui; WANG Ji-he; MA Quan-lin; LIU Hu-jun

2007, 26(04):  471-475 . 

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By using Shannon-Wiener index of niche breadth and Pianka index of niche overlap, this paper studied the niche characteristics of main plant species at different succession stages of vegetation in desert areas of north Gulang County, Gansu Province. The results showed that on mobile sand, Hedysarum scoparium had the widest niche breadth, followed by Artemisia arenaria. On semi-fixed sand, Nitraria tangutorum had the widest niche breadth, while on fixed sand, whether on unclosing fixed sand or on closing fixed sand, the niche breadth of H. scoparium was the widest. The niche breadth of the same plant species varied with vegetation succession stage, which reflected the effect of restored vegetation under different succession stages. Dominant species and the species with wide niche breadth had large niche overlap, while the niche overlaps of the same pair of species at different vegetation succession stages were inconsistent. Because of the habitat patch of species distribution, some species with narrow niche breadth also had large niche overlap.

Characteristics of nighttime sap flow and water recharge in Acacia mangium trunk

WANG Hua¹; ZHAO Ping¹; WANG Quan²; CAI Xi-an¹; MA Ling¹; RAO Xing-quan¹; ZENG Xiao-ping¹

2007, 26(04):  476-482 . 

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To research the nighttime water recharge in Acacia mangium trunk is helpful to improve the preciseness of canopy transpiration- and stomatal conductance estimation, and to further understand the time lag between canopy transpiration and stem sap flow. In this study, the whole-tree sap flow in A. mangium forest was measured by Granier’s thermal dissipation probe for over two years in Heshan Mountain of Guangdong Province, and the environmental factors, including relative humidity (RH), rainfall, vapor pressure deficit (VPD), photosynthetically active radiation (PAR), and air temperature (T) were recorded simultaneously. The nighttime water recharge of A. mangium trunk was analyzed on daily scale and monthly scale, and the results indicated that the sap flow density was smaller at nighttime than at daytime, and the range of nighttime sap flow density was wider in dry season than in wet season. The major duration of water recharging was from sunset to midnight. No significant differences were observed among inter-annual nighttime water recharges. Nighttime water recharge had no significant correlation with environmental factors, but correlated well with the diameter in the breast, height, and crown width of A. mangium. In dry season, the contribution of nighttime water recharge to total transpiration had significant correlations with daytime transpiration, total transpiration, VPD, PAR and T; while in wet season, it was significantly correlated with daytime transpiration and total transpiration.

Niches of dominant plant species of natural secondary forests in Zhuhai City, Guangdong Province

PENG Yi-sheng; ZHENG Ming-xuan; MO Luo-jian; TANG Guang-da; ZHUANG Xue-ying; CHEN Xi-mu

2007, 26(04):  483-488 . 

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A total of one hundred and twelve 10 m×10 m quadrats were set up in ten terrestrial secondary forest communities of Zhuhai City, Guangdong Province to study the niche breadth and niche overlap of the dominant plant species. The results indicated that the Shannon-Wiener’s niche breadth and Levins’s niche breadth of 23 dominant species in the communities were 0.4049—0.7736 and 0.0551—0.3086, respectively. The species with larger niche breadth were Acronychia pedunculata, Gordonia axillaris, Aporosa dioica, Microdesmis casearifolia, Gironniera subaequalis, and Sterculia lanceolata, which were the widespread species in natural forests. The niche similarity of dominant species varied between 0 and 0.3810, and the highest one occurred between A. dioica and Cinnamomum burmanii. A. pedunculata had different degree niche overlaps with other 22 species, but G. axillaris only had niche overlaps with a few dominant species. There were no niche overlaps in 20.6% of species-pairs. It was suggested that some widespread and well-adapted species with larger niche breadth, e . g . , A. pedunculata, G. axillaris, G. subaequalis and Endospermum chinense, should be selected in prior in the restoration of natural forests and the reconstruction of plantations.

Floristic characteristics and spatial distribution patterns of alien plants in Shandong Province

WU Tong¹; LI Jun-xiang^1，2; DAI Jie¹; WANG Ren-qing³

2007, 26(04):  489-494 . 

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Alien plants and their ecological invasion have negative impacts on indigenous species diversity and ecosystems, being one of the hotspots in current ecological research. Based on literature consultation and field survey, the database of alien plants in Shandong Province was established, with their components, geographical flora and spatial distribution patterns statistically analyzed. The results showed that there were 827 species of alien plants, belonging to 122families and 416 genera, among which, 348 species were imported from other countries. The alien plant species had a higher proportion, occupying 39.03% of the flora in the province, and were of the obvious dominant families and typical families. The diverse geographic distribution patterns of genera were characterized by 52.51% of temperate zone components and 44.06% of tropical zone components. The relatively centralized origins and distribution of alien species suggested the co-impacts of environment factors and human actions. Alien plants originated from temperate zone were more invasive in Shandong Province than those from other origins.

Effects of fertilization on nitrogen and phosphorus run-off loss from Qingzini paddy soil in Taihu Lake region during rice growth season

JIAO Shao-jun^1,2; HU Xia-min³; PAN Gen-xing¹; ZHOU Hong-jie³; XU Xiang-dong³

2007, 26(04):  495-500 . 

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A field observation on the nitrogen (N) and phosphorus (P) loss from a gley paddy soil (clayey illitic thermic typic Epiaqualf) in the Taihu Lake region during rice growth season showed that under conventional fertilization, the concentration of N and P in soil surface water and runoff was high at the early stage of rice growth, and then decreased quickly. The rainfall following fertilization caused a great decrease of N and P in soil surface water. During the whole growth season, the total runoff loss of N and P reached as high as 38.8 kg N·hm^-2 and 0.95 kg P·hm^-2, mainly through soil surface water. The majority of lost N was in NH₄⁺-N form, and that of lost P was particulate-P.Under no fertilization, the N and P loss was 47% and 60% of that under fertilization, respectively. At the early growth stage of rice, the runoff loss within 2 weeks after fertilization contributed about 50% of the total N loss and about 33% of the total P loss. The N and P loss after rain gave great contribution to the farmland non-point sources pollution. It was suggested that in the Taihu Lake region, fertilization by turns on the paddy soil with higher fertility could mitigate the N and P loss from paddy soil and the pollution risk of water system.

Profile distribution of alkali-hydrolyzed nitrogen in farmland soils of Northeast China along a latitudinal gradient

SHI Chun-jian^1,2; ZHUANG Qiu-li^1,2; LI Qi^1,2; LIANG Wen-ju¹; JIANG Yong¹

2007, 26(04):  501-504 . 

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The vertical distribution and latitudinal differentiation of alkali-hydrolyzed nitrogen in the profile down to 100 cm depth of maize soils in Northeast China was investigated along a latitudinal gradient. The results showed that soil alkali-hydrolyzed N was mainly distributed at the depth of 0—60 cm, and decreased with soil depth. Except for the Gongzhuling site, the soil alkali-hydrolyzed N content in other sampling sites was significantly different (P<0.05) among the 3 layers at the depth of 0—60 cm. Soil alkali-hydrolyzed N had a significant positive correlation (P<0.01) with soil organic carbon and total N, indicating that its content and distribution was mainly affected by soil organic matter and total N levels. Soil alkali-hydrolyzed N content increased with increasing latitude, and climate condition and soil type were considered as the main reasons that induced the latitudinal differentiation of soil alkali-hydrolyzed N.

PCR-SSCP genetic polymorphism and its genetic effect of 3′ side of pig MyoG gene

XUE Hui-liang¹; ZHOU Zhong-xiao²; Bo Wen³

2007, 26(04):  505-508 . 

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By using PCR-SSCP, the single-nucleotide polymorphism of 3′ side of MyoG gene in pig breeds Landrace, Large White, Duroc, Shanxi Black and Mashen was tested, with the effects of the MyoG gene on the test pigs birth mass, weaning mass, 6-month body mass, and backfat thickness analyzed. On the basis of published sequence of 3′ side of pig MyoG gene, three pairs of primers were designed, and one polymorphism was found in the PCR product amplified with F1/R1 primers. The results showed that in the breeds Landrace, Large White and Duroc, allele B was the dominant gene and its frequency was 0.8807, 0.7256 and 0.8581, respectively, while in breeds Shanxi Black and Mashen, allele A was the dominant gene and its frequency was 0.9359 and 10000, respectively.Breeds Landrace, Large White and Duroc differed significantly (P<0.01) in their genotype frequencies from breeds Shanxi Black and Mashen. Based on the analysis with fixed effect model, significant differences among different MyoG genotypes were observed in birth mass (P<0.05), whereas no significant differences existed in weaning mass, 6-month body mass, and backfat thickness. Least square analysis indicated that the individuals of BB genotype had significantly higher (P<0.01) birth mass than those of AA and AB genotypes, with the sequence of BB>AB>AA. These results suggested that genotype had significant effects on the individual’s birth mass, and selecting the individuals with B allele could be favorable to the birth mass.

Genetic diversity of Lithocarpus harlandii populations in three forest communities with different succession stage

LI Jian-hui^1,2; JIN Ze-xin²; LOU Wen-yan³; LI Jun-min²

2007, 26(04):  509-514 . 

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By using random amplified polymorphic DNA (RAPD) technique, this paper studied the genetic diversity and genetic differentiation of Lithocarpus harlandii populations in three forest communities (coniferous forest, coniferous and broad-leaved mixed forest, and evergreen broad-leaved forest) with different succession stage in Tiantai Mountain of Zhejiang Province. The results showed that a total of 173 repetitive loci were produced in 60 individuals of L. harlandii by 12 random primers, among which, 152 loci were polymorphic, and the total percentage of polymorphic loci was 87.86%. The average percentage of polymorphic loci of the populations was 65.32%, and their total genetic diversity estimated by Shannon information index was 0.4529, with an average of 0.3458, while that judged from Nei index was 0.3004, with an average of 0.2320.The percentages of polymorphic loci, Shannon information index, and Nei index of the populations were in the sequence of coniferous forest community>coniferous and broad-leaved mixed forest community>evergreen broad-leaved forest community. Analysis of molecular variance (AMOVA) showed that 72.85% of genetic variance was found within the populations, and 27.15% of genetic variance resided among the populations. The coefficient of gene differentiation was 0.2277, and the gene flow was 1.6949. The genetic structure of L. harlandii was influenced not only by the biological characteristics of this species, but also by the microenvironment of different communities. The mean of genetic identity among 3 populations of L. harlandii was 0.8662, and the mean of their genetic distance was 0.1442. The genetic similarity between coniferous and broad-leaved mixed forest community and evergreen broad-leaved forest community was the highest, while that between evergreen broad-leaved forest community and coniferous forest community was the lowest. The unweighted pair group method with arithmeticmean (UPGMA) cluster analysis based on Nei’s genetic distance showed that coniferous and broad-leaved mixed forest community first gathered with evergreen broad-leaved forest community, and then with coniferous forest community.

Relationships between Phodopus campbelli age and population density and Capillaria hepatica infective rate

WAN Xin-rong¹; JING Yu¹; WANG Guang-he¹; SA Ren-hua²; LUO Jian-ping²; GUAN Qi-ge³; YU Cheng³; DU Sen-yun⁴

2007, 26(04):  515-518 . 

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Capillaria hepatica is one of the popular parasites to Campbell’s hamster (Phodopus campbelli). An investigation was made on the infection of C. hepatica on P. campbelli populations in Xilinguole, Inner Mongolia from 2004 to 2005. The results showed that there was a significant positive correlation between P. campbelli age and C. hepatica infective rate (r=0.97, P<0.05). Older age groups suffered more infection than relatively younger groups,while the juveniles were rarely infected. The infection index was also significantly positively correlated with age (r=0.93, P<0.05). Body mass was another indicator, which had significant positive correlations with both infective rate (r=0.99, P<0.05) and infection index (r=0.95, P<0.05). However, the population density of P. campbelli had no apparent correlation with the infective rate (r=0.27, P>0.05) and infection index (r=0.41, P>0.05).

Diversity in functional group and nutritional class of arthropod community on cultivated lucerne grassland

JIANG Shuang-lin

2007, 26(04):  519-522 . 

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An investigation was made on the composition and structure of arthropod community on cultivated lucerne grassland in Qingyang City, Gansu Province. A total of 81 species belonging to 38 families and 15 orders were collected. According to the trophic level and feeding mode, three nutritional classes and fourteen functional groups were established, and the temporal dynamics of the diversities in species, functional group, and nutritional class were analyzed. The results indicated that during the growth season of lucerne, the species of arthropod community had the highest diversity, followed by functional group, and nutritional class. Both species diversity and nutritional class diversity had significant correlations with functional group diversity (P<0.01). Functional group biodiversity had a similar temporal variation trend with species biodiversity, while functional group diversity had less fluctuation. In studying the composition and structure of arthropod communities, species study could be replaced by functional group study to simplify the complicated network relationships among the species in the community, while functional group diversity could be used in evaluating the community similarity and stability.

Niche and interspecies competition of four Limacodidae species on green belt plants in Shanghai

JU Rui-ting¹; WANG Feng^1,2; LI Yue-zhong¹; WU Shi-ying³; DU Yu-zhou²

2007, 26(04):  523-527 . 

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To understand the interspecies relationships among common Limacodidae species on Shanghai green belt plants, the niche breadth, niche overlap, niche similarity, and interspecies competition of Cnidocampa flavescens, Setora postornata, Parasa lepida and Parasa consocia were studied in trophic, temporal, and spatial resources series. The results showed that P. consocia could use more host resources than other three species, and its niche breadth index was 0.5447. C. flavescens and S. postornata occupied more time resources, with the niche breadth index being 0.4304 and 0.4415, respectively. C. flavescens cocoons manifested the greatest spatial resources predominance, and the niche breadth index was 0.5441. As for the interspecies relationships, S. postornata and P. lepida were more adjacent in the utilization of trophic resources, and the indices of their niche overlap (2.6647), niche similarity (0.5199) and interspecies competition (0.7015) were all higher than those of other co-existing species. C. flavescens and S. postornata were more similar in using time resources, with the niche overlap and interspecies competition indices being 0.4846 and 0.5222, respectively, while S. postornata and P. consocia were more adjacent in the utilization of spatial resources, and had the highest indices of niche overlap (2.7495), niche similarity (0.9165), and interspecies competition (0.9959).

Ecological investigation and restoration strategies of spring- and autumn pastures in Yili River valley

ZHOU Bin; QIAO Mu; FENG Ying

2007, 26(04):  528-532 . 

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Aimed at the severe degradation of spring- and autumn pastures in Yili River valley, an investigation was made on these pastures under different managements (fencing, irrigating, and fencing and irrigating), and their degradation causes and restoration strategies were discussed from the aspects of plant biomass, species composition, biodiversity, and proportion of high quality grass. The results showed that the plant biomass on the pastures under proper irrigation was 1 540.5 g·m^-2, while that without irrigation was 188.13 g·m^-2, indicating that drought was an important factor limiting the vegetation growth. However, it was not enough to only improve the water condition of the pastures under over-grazing. With an overloading rate of 123%, the proportion of high quality grass on the pastures under irrigation decreased from 62.38% with fencing to 2.08% without fencing. Therefore, moderate grazing supplemented with irrigation could be the prerequisite for the effective restoration of natural pasture in Yili River valley.

Variation of grassland biomass and its relationships with environmental factors in Hulunbeier, Inner Mongolia

ZHENG Xiao-xuan^1,3; ZHAO Jia-ming²; ZHANG Yu-gang²; WU Ya-qiong^1,3; JIN Tian-tian^1,3; LIU Guo-hua¹

2007, 26(04):  533-538 . 

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Based on field investigation and experimental data, the variation pattern of grassland biomass and its relationships with environmental factors in Hulunbeier of Inner Mongolia were studied. The results indicated that there existed a significant difference in the biomass of plant communities along an environmental gradient. The variation of the biomass had no significant correlation with precipitation and air temperature, but positively correlated with soil organic carbon content in 0—20 cm layer and negatively correlated with soil bulk density. According to multiple regression, the main factor restricted the biomass was soil organic carbon. The utilization patterns of grassland in study area possibly made the soil nutritive condition become the limiting factor on the growth of grassland vegetations, which in turn affected grassland biomass.

Human activity intensity and its spatial distribution pattern in upper reach of Minjiang River

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

2007, 26(04):  539-543 . 

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Based on the self-correlation theory in geography and the National GIS database (1∶250000), the human activity intensity (HAI) and its spatial characteristics in the upper reach of Minjiang River were quantified and spatialized by calculating the weighted factors of roads, settlements and terrain. The results showed that the size and distribution pattern of HAI varied with the counties in the study area. In Heishui County, HAI was the strongest and had the most uniform distribution; in Lixian and Maoxian Counties, both the size and the distribution of HAI were close to the average; in Wenchuan County near Chengdu Plain, the HAI was rather low and distributed unevenly because of its covering Wolong Giant Panda Natural Reserve; while in Songpan County, it was low in HAI due to the low density of roads and settlements. It was a realistic and efficient way to delineate and analysis the HAI by gaining and integrating the factors of roads, settlements and terrain, which would benefit the further research of landscape pattern change.

Effects of human activities on seagrass bed ecosystem services value in Hepu of Guangxi Province

HAN Qiu-ying^1,2; HUANG Xiao-ping¹; SHI Ping¹; ZHANG Jing-ping^1,2

2007, 26(04):  544-548 . 

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In recent years, seagrass ecosystem in China has been degraded seriously. Taking the seagrass bed ecosystem in Hepu of Guangxi Province as example, and employing the basic theories of eco-economics, its services value loss caused by human activities was primarily estimated based on the local statistic data from 1980 to 2005. The evaluation indices system included food production, atmosphere regulation, ecosystem nutrient circulation, water purification, biodiversity maintenance, and functions of scientific research. The results showed that the total services value loss of seagrass bed ecosystem in Hepu of Guangxi was 34 657.95×10⁴ Yuan RMB from 1980 to 2005, and the loss ratio reached 71.97%, in which, the direct use value increased 4452.88×10⁴ Yuan RMB, while the indirect use value loss was 39 110.83×10⁴ Yuan RMB, with the loss ratio accounted for 81.82% from 1980 to 2005, proving that the increasing trend of human exploitation intensity was evident.

Characteristics and formation causes of temperate sparse forest grassland ecosystem in Inner Mongolia Plateau

YU Shun-li¹; CHEN Hong-wei²

2007, 26(04):  549-554 . 

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Temperate Ulmus pumila sparse forest grassland ecosystem in Inner Mongolia Plateau is a special ecosystem in China, and even in the world. Its study is of significance in deeply understanding the vegetation distribution patterns in the earth, and favoring the protection of this ecosystem. In this paper, the geographical distribution, species composition, community structure, and natural regeneration of this ecosystem as well as the related climate and soil conditions were analyzed, and a comparison on the characteristics of this ecosystem with those of grassland- and forest ecosystems was made. It was indicated that the temperate U. pumila sparse forest grassland ecosystem in Inner Mongolia Plateau could be regarded as a kind of longitudinal zonal (water gradient) climax vegetation formed under unique climate, soil and topographic conditions. The key factors deciding its existence were annual precipitation and soil moisture, while sandy soil was the secondary factor. This ecosystem was neither forest nor grassland, but a transition between them. In our opinion, The Vegetation of China should add a new vegetation type, temperate sparse forest grassland.

Urban wetland: Its concept, ecological services and protection

WANG Jian-hua^1,2,3; LU Xian-guo¹

2007, 26(04):  555-560 . 

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With the development of urbanization, urban wetland protection has become an increasingly important issue. Based on the review of related literatures, the concept of urban wetland was addressed, and its ecological service functions were analyzed. Under the intense human disturbance, the area of China’s urban wetland is reducing, with its ecological services deteriorated and pollution and eutrophication getting serious. Owing to the lack of study, there exist deviations in understanding the functions and worthiness of urban wetland, and higher opportunity cost in its protection. In this paper, the strategies for urban wetland protection in China were put forward, and some basic issues about the study and protection of China’s urban wetland were discussed.

Disturbance effect of rodents on soil and vegetation in desert ecosystem

JIANG Hui-ping^1,2; YANG Wei-kang¹; HU Zuo-jun³

2007, 26(04):  561-566 . 

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Disturbance-caused patch is of significance in the development and maintenance of temporal and spatial heterogeneity in desert ecosystem, while rodents are the important representatives of bio-disturbance, being a major source of patch formation in desert ecosystem. Rodents have evolved a series of physiological, morphological, and behavioral characteristics to adapt the asperity of desert environment, and their excavating and feeding activities also deeply affect the environment of desert ecosystem. This paper summarized the disturbance effect of rodents on soil (pedogenesis, patch formation, and physical and chemical properties) and vegetation (species diversity, productivity, and seed dispersion), aimed to illustrate the contributions of rodents activities to desert ecosystem.

Research progress on inhibitory effects of silicon on cadmium absorption by plants

CHEN Cui-fang^1,2,3; ZHONG Ji-hong²; LI Shu-yi²

2007, 26(04):  567-570 . 

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Applying chemical amendments is an effective way to mitigate soil heavy metals pollution. To study the effects and action mechanisms of applying silicon on inhibiting the cadmium absorption by plants is of significance in developing the techniques of controlling soil heavy metals pollution through applying silicon fertilizer as amendment. In recent years, a great deal of studies about the management of soil heavy metals pollution by using silicon fertilizer sprang up. This paper summarized the research progress on the inhibitory effects and action mechanisms of exogenous silicon on plant cadmium absorption, distribution and transfor-mation, and the plant physiological and biochemical responses to cadmium stress induced by silicon. Some issues for further study were suggested.

Research advances in simulation models of ozone impact on crops

YAO Fang-fang; WANG Xiao-ke; FENG Zong-wei; OUYANG Zhi-yun

2007, 26(04):  571-576 . 

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The impact of increasing ozone (O₃) concentration in troposphere on crops has being drawn more and more concern, and its simulation study has become a hotspot. To build effectual simulation models to evaluate and predict the crop loss by O₃ would help to the ozone pollution control and agriculture safety. According to the relationships between crop growth and O₃, the models could be classified as statistical models and mechanism models. In this paper, concentration-, dose/exposure- and flux-based statistical models were introduced, based on their development process, and three influential mechanism models (CLASS, Martin, and AFRCWHEAT2-O₃) were discussed in pivot. The limitations of each model were pointed out, and the development trends of related studies in China were put forward.

Microbes and their functions in sulfur cycle of coastal salt marsh sediments

XING Ying; LIU Chang-hong; AN Shu-qing

2007, 26(04):  577-581 . 

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Sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria (SOB) play important roles in the sulfur cycle of coastal salt marsh sediments. SRB can reduce sulfate to sulfide, while SOB can oxidize the reduced sulfur compounds to sulfate and decrease the accumulation of sulfide. Both of them can keep the dynamics of sulfur cycle in balance. This paper summarized the research progress on the existent forms of sulfur in coastal salt marsh sediments, its geochemical cycle, and the biodiversity, bioactivity, and ecological significance of SRB and SOB. Some issues involved in the sulfur cycle in coastal salt marsh ecosystem and the ongoing research on the functions of SRB and SOB in this ecosystem were discussed.

Ecological effects and economic benefits of rice-duck farming

DENG Qiang-hui; PAN Xiao-hua; WU Jian-fu; SHI Qing-hua

2007, 26(04):  582-586 . 

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Rice-duck farming is a low-cost eco-agricultural technique with noherbicides and less insecticides application. In general, 20 day-old ducklings are released into recently transplanted rice fields at a density of 225 ducks per hectare. Their feeding and moving could help the control of weeds, insect pests and even plant diseases in the fields, and have definite effects on rice growth, soil characters, and oxygen content in field water. This paper reviewed the ecological effects and economic benefits of rice-duck farming, and suggested that the studies on precision fertilization and rice later growth stage pest management should be strengthened.

A research review on forest gap disturbance

TAN Hui^1,2; ZHU Jiao-jun¹; KANG Hong-zhang^1,2; HU Li-le^1,2

2007, 26(04):  587-594 . 

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Forest gap is ubiquitous in both undisturbed and disturbed forest ecosystems, which drives the development of forest ecosystem, and affects the composition of plant species, stand structure and succession phase. The study of forest gap is of significance for the restoration and management of disturbed forest ecosystem. Based on a wide range of literature collection, the concept and characters of forest gap, variations of habitat conditions after gap formation, as well as the responses of plant species to forest gap and the research means on forest gap were summarized, which could be helpful to the forest ecosystem management and other related studies of forest science.

Roles of plants in biogeochemical cycling of silicon

WANG Xiu-fang¹; CHEN Sheng-bin²; SONG Ai-qin¹; YE Wen¹; LI Zhen-ji¹

2007, 26(04):  595-600 . 

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Silicon is an important mineral element on the earth, because of its crucial role in many biogeochemical processes. Traditionally, silicon cycling is thought to be mainly controlled by rock weathering, subsequent mineral dissolution, and final aggradation in waters. Actually, plants react on the biogeochemical cycling of silicon. A great pool of silicon is contained as the accumulations of amorphous silica (SiO₂·nH₂O) in living plant tissues, known as biogenic silica (BSi), phytolith or opal. The annual fixation of BSi by terrestrial plants ranges from 1.68×10⁹ to 5.60×10⁹ t. After decomposition, about 92.5% of the BSi from litterfall is absorbed by plants again, and the rest 7.5% remains in soil. Because the silicon absorbed by plants from soil BSi pool is far more than that released by weathering, plant-soil internal cycling can greatly affect the dissolved silicate fluxes from terrestrial ecosystem to rivers and oceans. The annual fixation of BSi by diatom in ocean is from 5.60×10⁹ to 7.84×10⁹ t, about 97% of which is absorbed by diatom again before reaching seabed, and only 1.43×10⁸—2.55×10⁸ t (about 3%) is buried in sediment yearly. In this way, diatom plays an important role in the aquatic cycling of silicon. In conclusion, plants are very important in both terrestrial and aquatic biogeochemical cycling of silicon, and thus, the effects of plants must be considered in the study of global biogeochemical cycling of silicon.

Biological characteristics and multiplication techniques of Sepia esculenta

HAO Zhen-lin; ZHANG Xiu-mei; ZHANG Pei-dong

2007, 26(04):  601-606 . 

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Sepia esculenta (Cephalopoda: Sepioidea) is widely distributed in the sea areas of Russian Far East, China, Japan, Korea and Philippines. It is not only one of the most important species of coastal fisheries resource in China, but also a good wild species with high commercial value. This paper reviewed the research advances on the biological characteristics and multiplication techniques of S. esculenta, with the focus on its morphology, fishery biology, behavior ecology and genetics, as well as the artificial hatching of fertilized egg, paedomorphosis, and effects of material quality, shape, stability and color of spawning substrates on attachment of fertilized egg, and discussed the existing problems and future directions in researching the multiplication techniques of S. esculenta.

Community structure of soil macro-fauna at different restoration stages of an opencast coalmine

CUI Yan^1,2; BAI Zhong-ke¹; LI Jin-chuan³; HAN Li-jun²; FAN Wen-hua²

2007, 26(04):  607-610 . 

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An investigation was made on the compositions of soil macro-fauna in Antaibao Opencast Coalmine ecosystems at three restoration stages in Pingshuo of Shanxi Province. A total of 316 individuals belonging to 30 families, 8 orders and 4 classes of soil macro-fauna were collected, and the community structure was analyzed by using DIG index, DG index, and Gower similarity index. The results indicated that the community structure of soil macro-fauna in restored ecosystems tended to be complex with the time of land reclamation and ecological reconstruction. At the restoration stage from the 1st to the 13th year after reclamation, the biomass of soil macro-fauna increased, with a speed of fast-slow-fast. Higher values of Gower index were observed among the ecosystems with longer term restoration, indicating that soil macro-fauna had a relatively higher similarity in the ecosystems with longer term restoration than in those with shorter term restoration.

An extraction method of fungal DNA from soils in North China

WU Min-na^1,2; ZHANG Hui-wen¹; LI Xin-yu¹; SU Zhen-cheng¹; ZHANG Cheng-gang¹

2007, 26(04):  611-616 . 

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Owing to the complexity of soil physical and chemical properties and the structural particularity of fungal cell wall, the extraction of fungal DNA is more difficult than that of bacterial DNA from soil samples. The soils in North China have their own special properties, compared with the others. Therefore, it is necessary to optimize the extraction method of fungal DNA from soils in North China to study their fungal diversity and composition. Based on the 28S rDNA-PCR-DGGE analysis with fungal universal primers, seven extraction methods were evaluated by adding twelve fungi with greater difference in taxonomy into sterilized black soil. The results showed that two methods were more efficient for the study of soil fungal diversity, i . e ., (1) grinding soil samples in liquid nitrogen, treating them with cellulase, snailase and lysozyme (6, 3, and 1mg·ml^-1, respectively) for 60 minutes at 37 ℃, and lysing with 2% SDS for 30 minutes in 65 ℃ water bath, and (2) freezing and thawing soil samples at -65 ℃ for three times, treating them with cellulase, snailase and lysozyme (6, 3 and 1 mg·ml^-1, respectively) at 37 ℃ for 180 minutes, and lysing with 2% SDS for 30 minutes at 65 ℃. The fungal DNA was extracted from three natural soils with greater differences in physical and chemical properties in North China by using the second method, and the 28S rDNA-PCR-DGGE profiles showed that the fungal DNA bands were comparatively rich, suggesting that this method could be used in fungal diversity research of North China soils.