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Table of Content

    29 April 2011, Volume 26 Issue 4 Previous Issue    Next Issue
    Resources Utilization and Management
    Discussion on Beach Quality Standards Rating System in China
    YU Fan, CAI Feng, LI Wen-jun, A Dong
    2011, 26 (4):  541-551.  doi: 10.11849/zrzyxb.2011.04.001
    Abstract ( )   PDF (1565KB) ( )   Save
    Based on beach quality standards and rating systems abroad, the paper proposes a new beach quality standards rating system adaptable to the specific situations of China. This system includes 54 factors grouped into two subsystems (natural and socioeconomic). The former includes three subtypes of geomorphology, hydrology, eco-environment, and the latter includes all types of human activities. In order to rate the beaches quality, different factor scores were evaluated to beaches with different developing levels, from which five rating indicators of Diamond, Gold, Silver, Bronze and Disqualification were resulted. The rating system was applied to six beaches in Shandong and Fujian provinces which can be grouped into two different development stages (developed and developing), and the rating sores ranged from 84% (Huangcuo at Xiamen) to 47% (Dajing at Xiapu). Applicability of the rating system and management strategies for beach resources sustainable development were also discussed.
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    Regional Differences and Evolution of Livestock Farming Patterns in China
    LIU Ai-min, QIANG Wen-li, WANG Wei-fang, ZHAO Ming-yang
    2011, 26 (4):  552-561.  doi: 10.11849/zrzyxb.2011.04.002
    Abstract ( )   PDF (3625KB) ( )   Save
    The output of China's meat and eggs for many years ranked first in the world, and livestock husbandry has become a significant industry in China. The pattern of the livestock farming in China has changed from free-range farms to scale farms, which has influenced a lot in the demand of the industrial feedstuff and soybean meal. Based on the systematic analysis of farming patterns and their influencing factors, this paper studied the dynamic mechanism and stage evolution process of livestock farming patterns in China; and also made the quantitative simulation of the hog, egg and broiler in the main production areas according to construction of the Logistic Function. The results showed the followings: 1) The changes of farming patterns generally experienced low-speed transformation in the early stage, rapid transformation in the medium-term stage, slow developing process in the later period and the stage of the total intensive farming. 2) The suburban areas with rapid economic development cities such as Beijing, Tianjin and Shanghai have almost accomplished the transformation process, and the developing trend in these areas will be highly efficient, pollution-free and sustainable in the future; the areas such as Heilongjiang, Jilin and Liaoning own good agriculture resource conditions, and the suburban areas of the relatively high level of economic development provinces such as Shandong, Hebei, Jiangsu, Guangdong and Henan, are at the stage of rapid-speed transformation; however, most regions in the Central and Western China are in the early stage of the evolution process and the transformation speed is relatively slow. 3) On the whole, hog farming patterns went through the transition from the stage of low-speed transformation to medium-term stage of rapid transformation, and at present, farming patterns are still in the medium-term stage of rapid transformation in most of the major hog producing provinces, so the farming level is relatively low during the period, but the room for the growth will be much bigger in the future. However, the broilers and layers both are in the late stage of slow transformation, and the intensive farming industry is relatively developed but it's difficult to promote more. 4) The main reason that soybean demand rapidly increases in the past ten years is the change of livestock farming patterns. The scale of live hog farming in Central and Western China will constantly increase in the next decade. Meanwhile, the slaughter of live hog, broilers and layers will continue to rise in most regions. So the gap between soybean supply and demand will continually expand with the limited production capacity of domestic soybean.
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    Controls over Soil Desiccation for Management of Artificial Vegetation in Dryland Areas of Northern China
    WANG Han-sheng
    2011, 26 (4):  562-577.  doi: 10.11849/zrzyxb.2011.04.003
    Abstract ( )   PDF (671KB) ( )   Save
    Artificial vegetation is of great significance in the dryland areas of northern China, but water balance must be thought over in its construction under droughty conditions of less precipitation. Based on this, the paper dealt with the matching of artificial vegetation to its environment from the angle of soil moisture by investigating long-term management practices. After presenting the unfavorable feedback effects of soil desiccation occurring universally by artificial vegetation and its controllability, the author further analyzed the controlling ways and measures. It is shown that the phenomenon of soil desiccation might be controlled by artificial measures, such as partial afforestation or cultivation of forage grasses in strips or patches, thinning, rotation cropping, fallowness, irrigation, etc. On the basis of carrying out the principle of planting in accordance with site conditions, drought-resistant and water-saving plants that consume less water and community density or coverage to maintain soil reservoir level would need to be chosen, which is another important aspect to deserve to be taken seriously for guaranteeing vegetation stability. Preventing soil desiccation is the most important, and some controlling ways should be integrated. Controlling soil desiccation is actually equivalent to effectively managing artificial vegetation. The managing goal is one of the main factors to assess the stability of artificial vegetation.
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    Resources Safety
    Regional Ecological Security Assessment Based on Land-Use Change—A Case Study in Ordos City
    MENG Ji-jun, ZHAO Chun-hong, LIU Ming-da
    2011, 26 (4):  578-590.  doi: 10.11849/zrzyxb.2011.04.004
    Abstract ( )   PDF (1404KB) ( )   Save
    The cumulative effects of human activities on regional ecological security have attracted much attention in recent years. Land use/cover change plays a decisive role to regional ecological security. In this research, we chose Ordos which is located in northern agro-grazing eco-tone as the study area. Basing on GIS and SPSS software platform, we constructed indicators system of ecological security assessment, calculated the threshold and constructed model of ecological security assessment in 1988, 2000 and 2008. From the studies above, the following conclusions can be drawn: 1)The ecological security situation of the study area got worse at first, but then improved in the year of 2000, which was directly related to the policies of returning farmland to forest (grass) and fencing and delaying grazing. This phenomenon indicates that economic activities such as land use and the enacting of policies affect regional ecological security level significantly. In addition, policies are playing a more and more important role in not only the development of agriculture and livestock, but also guiding the overall ecology. 2) Grassland with high coverage rate got the highest level of ecological security among all land-use types, and grassland with middle coverage rate got the second. Ecological security of forestland was very steady. Water and low coverage grassland were often at a critical stage, and could be easily affected by precipitation, saline soil, as well as desertification. In contrast, farmland, built-up land and unutilized land were at the lowest ecological security level. 3) Otog Banner was at the level of better security. Otog Front Banner and Jungar Banner were at the level of critical stage of security. Dalad Banner and Dongsheng District were at the lowest ecological security level. During the past 20 years, the ecological security has been getting better in Dongsheng District and Ejin Horo Banner, it first decreased and then increased in Otog Front, Otog, Hanggin, Uxin and Jungar banners to different degrees. The results could be beneficial for providing references to regional ecological management for the local government.
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    Resources Ecology
    Index System and Criteria for Diagnosing the Status of River Health
    WANG Shu-ying, WANG Hao, GAO Yong-sheng, YAN Yan
    2011, 26 (4):  591-598.  doi: 10.11849/zrzyxb.2011.04.005
    Abstract ( )   PDF (391KB) ( )   Save
    Based on the meaning of river health reflecting the natural and social attributes, an index system for diagnosing the status of river health was constructed. This index system included three first-grade indexes,namely river morphology, river social economic function and river ecologic function, and 18 second-grade indexes. This paper chose multiobjective multilayer fuzzy model to diagnose the river health. It put forward the index standard characteristics value and gave the method to determine the index weight. Taking East River as an example, it diagnosed the river health by determining the index weight and value. The diagnosis result demonstrated that East River health is at the lower edge of good condition. The key factor that influenced the river health is the changed river morphology. It put forward the suggestion for river restoration.
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    Water Ecological Function of Green Space in Anji City, Taihu Lake Basin
    YANG Li-yun, WU Song-tao, LI Wen-hua, LI Yuan, DANG Zhi-hong, YANG Xiao-ling
    2011, 26 (4):  599-608.  doi: 10.11849/zrzyxb.2011.04.006
    Abstract ( )   PDF (970KB) ( )   Save
    In this paper, we studied the water ecological function of green space in Anji County Seat of the upper Taihu Lake Basin. Basing on data collection and fieldwork, we divided green space into attached and residential quarter green area, park green area, street green area, and green area for environmental protection. These systems generate a range of water ecological services which can intercept precipitation, reduce surface runoff, and purify water. In the paper, the green space has intercepted precipitation 400.3×104 m3, and reduced COD 16.0 t, TN 7.91 t, NH4-N 0.22 t, and TP 0.29 t in Anji County Seat in 2008. The water ecological function is affected by green space area and vegetation type, therefore, the attached and residential quarter green area and the park green area have higher water ecological functions.
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    Special Column:Celebration of the 70th Anniversary of IGSNRR, CAS
    Spatial-temporal Characteristics of Vegetation Cover Change in Mountain-Oasis-Desert System of Xinjiang from 1982 to 2006
    WANG Zhi, SHI Qing-san, WANG Tao, SHI Qing-dong, CHANG Shun-li, ZHANG Lü-bing
    2011, 26 (4):  609-618.  doi: 10.11849/zrzyxb.2011.04.007
    Abstract ( )   PDF (4507KB) ( )   Save
    Dynamics of vegetation cover plays an important role in the coexistence and balance evolution mechanism of mountain-oasis-desert system (MODS) in Xinjiang. Based on the satellite-derived NDVI data, produced by GIMMS (Global Inventory Monitoring and Modeling Studies) group, derived from the NOAA/AVHRR (National Oceanic and Atmospheric Administration/the Advanced Very High Resolution Radiometer) land dataset, the fractional vegetation cover (fvc) was calculated at a spatial resolution of 8 km×8 km and at a 15-day interval, for the period January 1982 to December 2006 and then the annual maximum fvc was obtained by the maximum value composites (MVC) method. Under the basic pattern of MODS in Xinjiang, the fvc spatial-temporal dynamics characteristics of trends, rate, amplitude, and variability of 25 years in Xinjiang were analyzed by dividing the whole region into four subregions in terms of regional differentiation, and mountain, oasis, desert system in every subregion by altitude and landuse. The results showed that the fvc dynamics increased significantly in general, but fluctuated remarkably in the period from 1982 to 1995 and relatively stable from 1996 to 2006, varied significantly with different subregions, and subsystems of mountain, oasis and desert, in which the vegetation cover of oasis increased mostly rapidly, but desert decreased most obviously. On the amplitude and variability, the eastern and southern subregions exceed the northern and Yili subregions, desert > mountain > oasis, and the lower fvc is larger than the higher fvc. The significant improved subregions are located in oasis, its surrounding areas and part of mountains, but the degenerated subregions are mostly situated in desert of eastern and southern Xinjiang. There are different change characteristics in different fvc subregions, that is, the vegetation degenerated in lower fvc subregions and improved in higher fvc subregions.
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    Resources Ecology
    Modeled Effects of Changes in the Amount and Diffuse Fraction of PAR on Forest GPP
    HE Xue-zhao, ZHOU Tao, JIA Gen-suo, ZHANG Zi-yin, LI Xiu-juan, ZHAO Chao, FENG Sheng-hui
    2011, 26 (4):  619-634.  doi: 10.11849/zrzyxb.2011.04.008
    Abstract ( )   PDF (1776KB) ( )   Save
    The scattering and absorption of solar radiation by anthropogenic aerosols reduce the amount of photosynthetically active radiation (PAR) reaching the earth's surface and increase the fraction of PAR that is diffuse (FDIFF), with the counteracting effects on plants photosynthesis which determines terrestrial ecosystem's gross primary production (GPP). For the complex interactions among the total PAR amount, FDIFF, temperature and humidity, it's difficult to derive the quantitative relationship between FDIFF and GPP from present field and experimental measurements, leading to substantial uncertainty and dispute about the projection of the production and carbon assimilation of terrestrial biosphere influenced by emissions of anthropogenic aerosols. Using a process-based canopy photosynthesis model (MAESTRA), we explored respective and combined effects of changes in PAR amount and the FDIFF on GPP in three typical forests among the North-South Transect of Eastern China (NSTEC). The results showed that the responses of GPP to PAR amount changes were consistently positive in all three sites, while the magnitudes of GPP change were determined not only by the degrees of PAR amount change but also the sensitivity of GPP to these changes, which was generally depressed to nearly naught by higher PAR amount and/or lower temperature from about 0.6 g C mol-1 when incident PAR was lower and temperature was not limited. The increase of FDIFF stimulated absorption and use efficiencies of incident PAR in the three forests, as a result of the difference, which was depressed by lower temperature and/or fewer leaf area, between the efficiencies of direct and diffuse PAR, leading to the magnitudes of GPP change responding to FDIFF changes were also influenced by the temperature and leaf area as well as the degree of FDIFF changes and the total PAR amount. Investigating the relations between the changes of diffuse PAR and total amount was necessary in quantifying the combined effects of these changes on GPP, which were generally the consequence of the counteraction of respective effects of the changes. In our results, the counteraction was usually significant under conditions with greater PAR amount, but the direction of GPP changes was still mainly controlled by the changes of PAR amount. The year-around offset was about 1/3 - 1/2 of the degree of the effect of total amount changes.
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    Resources Evaluation
    Evolution and Driving Forces of Water Consumed Structure in Beijing during the Past 30 Years
    ZHAI Yuan-zheng, WANG Jin-sheng, ZHENG Jie-qiong, HUAN Huan
    2011, 26 (4):  635-643.  doi: 10.11849/zrzyxb.2011.04.009
    Abstract ( )   PDF (930KB) ( )   Save
    During the past 30 years, average annual precipitation and total water resources of Beijing have decreased by 6.89% and 31.37% compared with those during 1956-2000, while total water resources consumed in this period reached pinnacle historically. The exact analysis and scientific forecast of water consumed structure are not only the basic premise and foundation for establishing the development plan of water resources utilization, but also the main warranty for industrial structure adjusting and optimizing. Accordingly, it’s of great significance for the harmonious development between socioeconomy and resources environment. Based on the analysis of total water resources consumed, agricultural, industrial, domestic and environmental water consumed, and evolution of water consumed structure, further driving forces of evolution of total water resources consumed and water consumed structure are revealed, and finally the prediction and discussion are made for the evolution of total water resources consumed and water consumed structure and supply-demand situation of water resources in the near future, the total water consumption of each year in the near future will go on to decline steadily and slowly based on the present amount (around 35×108 m3/a) influenced by the decrease of agriculture and industry water consumption, and the increase of resident and ecological water consumption; the pressure of Beijing from water supply will reduces obviously within a certain period in the near future after the reach of water from South-to-North Water Transfer Project. We hope that these endeavor will provide scientific basis for harmonizing the relationship between socio-economic development and water resources, establishing rational strategic plan of water resources, and social sustainable development.
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    Multiple Time Scales Analysis of Temperature and Precipitation Variation in Shanghai for the Recent 136 Years
    SHEN Qian-qian, SHU Jiong, WANG Xing-heng
    2011, 26 (4):  644-654.  doi: 10.11849/zrzyxb.2011.04.010
    Abstract ( )   PDF (1352KB) ( )   Save
    Mexican Hat form wavelet transformation and Empirical Mode Decomposition (EMD) are mainly used to investigate the 1873-2008 data of Shanghai yearly average temperature and annual precipitation at multi-time scales.The oscillating structure and periodic characteristic of Shanghai climate at multi-scales are expected to be understood. The result shows that, the increasing trend of Shanghai annual temperature is obvious, especially after the 1980s when the increasing speed is faster than ever before. The warm period of the 1940s and the cold period of the 1960s constitute the main features of the 20th century temperature changes in Shanghai. The influence of temperature variations between urban and suburban area caused by urbanization is obvious. Annual precipitation of Shanghai is oscillating mainly at micro-scale while fluctuation cycles are around 40 years. The wavelet transform results show that the precipitation will be increasing in large-scale but declining in micro-scale.
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    Carbon Storage of Forest Vegetation and Its Geographical Pattern in China's Jiangxi Province During 2001-2005
    LI Xin, OUYANG Xun-zhi, LIU Qi-jing
    2011, 26 (4):  655-665.  doi: 10.11849/zrzyxb.2011.04.011
    Abstract ( )   PDF (2579KB) ( )   Save
    Based on the second-class forest inventory data of Jiangxi Province during the Tenth Five-year Plan period (2001-2005), the carbon storage of forest ecosystems was estimated by regression equations between biomass and timber volume for dominant tree species, and its spatial pattern was analyzed. The total carbon storage of forest vegetation (including understory) was 263.87 Tg C (0.26387 billion tons), including 214.70 Tg C of forest stands (tree layer only). Among the 11 prefectures or cities,Ganzhou City possessed the largest amount of 70.11 Tg C, followed by Ji’an, Shangrao and Yichun counties in sequence. The average carbon densities of forest vegetation and forest stands were 26.27 t/hm2 and 27.20 t/hm2, respectively. The densities varied among districts, with the highest in Jingdezhen city, 31.65 t/hm2, followed by Yichun, Ji’an and Yingtan, in sequence. Among the forest categories, Cunninghamia lanceolata plantation had the largest storage of 73.77 Tg C or 34.36% of the total carbon storage. The carbon density of broad-leaved forest was 42.64 t/hm2,1.5 times of the average value of the whole province. Increasing with developing stage, the carbon storage of young and middle age forest stands accounted for 81.95% of the total storage in the province.
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    Spatial-temporal Pattern to Fishing Ground of White Croaker in Bohai, Yellow and East China Seas
    CHEN Jia-jie, XU Zhao-li
    2011, 26 (4):  666-673.  doi: 10.11849/zrzyxb.2011.04.012
    Abstract ( )   PDF (1567KB) ( )   Save
    The distribution and spatial patters of white-croaker fishing grounds in Bohai, Yellow and East China Seas were studied according to the capture production from 1971 to 1982. It shows that there are three types of white-croaker fishing ground, that is the spawning grounds which were mainly located in coastal waters of the East China Sea during spring, feeding grounds which were concentrated on the northern part of the East China Sea and the southern of the Yellow Sea during summer, and the wintering grounds, including two parts: the northern one locating in the eastern offshore of the Yellow Sea and the southern one concentrating on the southern nearshore of the East China Sea. The capture production of white-croaker in the East China Sea had increased insignificantly and exceeded the production of the Bohai and Yellow Seas since 1978. In addition, the main fishing grounds for white-croaker in the East China Sea were located in the Changjiang River estuary during May-September and the northern nearshore of the Yellow Sea and center of the Bohai Sea during November. During the fishing season, these places, with intensive fish group and concentrated production, were high-quality fishing grounds. The spatial distribution pattern of the fishing grounds for white-croaker in 1971-1982 was similar to the current, hence the research on white-croaker in the characteristics of fishing grounds, fishing season and the contribution of fish distribution pattern mode is of important reference value to the present protection of the fish resource.
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    Contribution Characteristics of Wind Erosion to the Sediment Yield in the Kuyehe River Watershed at Time Scales
    LI Qiu-yan, CAI Qiang-guo, FANG Hai-yan
    2011, 26 (4):  674-682.  doi: 10.11849/zrzyxb.2011.04.013
    Abstract ( )   PDF (1790KB) ( )   Save
    Wind erosion plays an important role on sediment yield in complex erosion zone by wind and water of the Loess Plateau. Contribution characteristics of wind erosion to the sediment yield in the Kuyehe River watershed at time scales was estimated based on the sediment discharge records at Shenmu Hydrological Station and meteorological measurements recorded at meteorological stations in and around the watershed. The results reveal that wind erosion is a principal contributor to sediment yield of the Kuyehe River watershed. At the monthly scale, sediment yield from wind erosion had a restore-release process. Wind erosion contribution rate was the highest in March and November-December, and was lower from April to September. Alluvial sediment in winter and spring was gradually discharged in summer. The wind erosion contribution rate at the monthly scale was consistent with the wind erosion climatic factor. The amount of sediment of July and August from wind erosion occupied 80.5% of the total amount of a year. At the seasonal scale, wind erosion contribution rate in summer was the lowest of 7.8%, and gradually increased in autumn and winter, then reached the highest in spring of 28.6%. At yearly scale, wind erosion contribution rate is about 17.2% at catchments upstream of Shenmu Hydrological Station in the Kuyehe River watershed during the period 1956-1970.
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    Nonlinear Characteristics of Runoff Processes of the Manas River in Xinjiang
    LING Hong-bo, XU Hai-liang, ZHANG Qing-qing, SHI Wei
    2011, 26 (4):  683-693.  doi: 10.11849/zrzyxb.2011.04.014
    Abstract ( )   PDF (715KB) ( )   Save
    Based on the monthly stream discharge data of Kenswat Station and the climate data of ten meteorological stations from 1954 to 2007 in the Manas River Basin, the paper studied the nonlinear characteristics of the Manas River runoff and affecting factors by using methods of wavelet transform, chaotic theory and the periodic trend superposition model. The results show that: 1) The primary periods of the annual runoff are respectively 15,18 and 22 years, but are most significant at just 18 years; 2) the annual runoff change of the Manas River presents a complex nonlinearity, and the correlative dimension is 3.3178 which is non-integral, indicating that the variation process of the annual runoff has fractal and chaotic characteristic; 3) based on the periodic trend superposition model,the annual runoff will keep an increasing trend in the coming seven years after 2007; 4) the NAO has the best positive relationships with the runoff in winter, while in summer the relationships are negative and in annual the worst; and 5) the NAO has strong impacted on the climate variations which are caused by the atmospheric circulation in the Manas River Basin, then the runoff of the Manas River is affected.
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    Resources Research Methods
    Moisture Content of Sand Layer and Its Origin in a Mega-dune Area in the Badain Jaran Desert
    ZHAO Jing-bo, SHAO Tian-jie, HOU Yu-le, Lü Xiao-hu, DONG Zhi-bao
    2011, 26 (4):  694-702.  doi: 10.11849/zrzyxb.2011.04.015
    Abstract ( )   PDF (930KB) ( )   Save
    In order to identify sand moisture of the mega-dune area and water sources in the mega-dune formation in Badain Jaran Desert, a sampling study on 15 boreholes with a depth of 5 m belonging to a 1610 m mega-dune located in the east of Nuoetu with the largest height difference was conducted in May 2009. The results showed that, the depth of distribution of dry sand layer of mega-dune area in Badain Jaran Desert is deeper than that of the distribution of dry sand layer depth of the precipitation areas. Moisture of wet sand layer is lower than that of the area with more precipitation, which indicates that it is a normal phenomenon in the area that the moisture content of wet sand layer under the local climate conditions is less than 2%. Sand layer of water in Nuoetu mainly exists in the form of thin film of water. With the thin film of water down the process of infiltration, some gravity water appears changed by thin film of water. This shows that moisture in mega-dune area may be one of the sources of the lake and groundwater. Spatial differences of sand moisture in mega-dune area are significant. The high moisture is in low-lying land and flat, which is beneficial to the precipitation infiltration. Especially the existence of thin dry sand layers showed that the effect depth of evaporation on sand moisture was very small, and can effectively promote the atmospheric precipitation transforming into groundwater through infiltration, which is the reason for infiltration of precipitation to reach groundwater level and become the import source of lake water in extreme drought conditions. Moisture in the area has a positive balance of the display, which is caused by a quick sand moisture infiltration and the effect depth of evaporation was very small. This phenomenon belongs to the positive equilibrium of moisture which is decided by the attribute conditions of sand moisture.
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    Urban Fringe Division and Feature Analysis Based on the Multi-criterion Judgment
    WANG Hai-ying, ZHANG Xin-chang, KANG Ting-jun, ZHAO Yuan
    2011, 26 (4):  703-714.  doi: 10.11849/zrzyxb.2011.04.016
    Abstract ( )   PDF (2173KB) ( )   Save
    On the basis of summarizing the predecessor's research, this article proposes the urban characteristic attribute concept, and constructs a set of evaluation index system and urban fringe division method based on the multi-criterion judgment. Using the accumulation frequency histogram and the K Means space cluster method, the urban fringe division standard is identified, and finally the urban fringe division result of the Guangzhou City is obtained. The result shows that, the urban fringe areas are mainly distributed around the main city zone and some center town zones, radiatively distributed along with the city transportation lines, and the average urban characteristic attribute is 0.292. The urban fringe area accounts for 46.73% of the total area of Guangzhou, mainly distributing in Panyu, Baiyun and Huadu districts, and is 76. 511% of the total urban fringe area. The Haizhu and Liwan's urban fringe shape is compact, with the compactness index being 4.1272 and 3.4725 respectively. The Baiyun, Panyu and Huadu's urban fringe shape is fragmentized, with compactness index being 7.8472, 7.1993 and 7.5255 respectively.
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    Special Forum
    Advances in Studies on Organic Nitrogen Uptake by Terrestrial Plants
    XU Xing-liang, BAI Jie-bing, OUYANG Hua
    2011, 26 (4):  715-724.  doi: 10.11849/zrzyxb.2011.04.017
    Abstract ( )   PDF (747KB) ( )   Save
    Traditional concept of nitrogen cycling in terrestrial ecosystems has assumed that organic nitrogen can be used by terrestrial plants only after it is decomposed by soil microorganisms into inorganic nitrogen (NH4++NO3-). Recent studies have confirmed that a variety of plant species have the capacity to take up soil organic nitrogen in the form of low molecular weight substances, e.g. free amino acids, challenging the core of the traditional concept of nitrogen cycling. We here reviewed major advances made in the studies of organic nitrogen uptake by plants from five aspects: nitrogen forms in soil, evidence of organic nitrogen uptake by plants, mechanisms responsible for organic nitrogen uptake by plants, main plants and ecosystems with importance of organic nitrogen uptake and the balance between exudates and uptake of organic nitrogen by roots. We also assessed advantages and limits of research approaches. According to the central question within this research field, we suggested several directions we should focus on in future studies. We call for new research for a better understanding of organic nitrogen uptake by plants.
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