Table of Content

    15 December 1996, Volume 51 Issue s1 Previous Issue    Next Issue
    Li Kerang
    1996, 51 (s1):  1-14.  doi: 10.11821/xb1996S1001
    Abstract ( )   PDF (823KB) ( )   Save
    The paper introduces the main research progress of global climate change and its impact and futuredirections based on the IPCC second assessment, the climate Agenda and other articles. The paper is outlined in five parts:1. International programs associated with climate① The world climate programme(WCP) is organized into four major sub-programs.② The international Geosphere-Biosphere Programme (IGBP) is organized into six core projects andthree activities.③ The Human Dissensions of Global Environmental Change (HDP).④ The Global Climate Observing System (GCOS)2. The new progress of the climate change science.3. The new progress of the impact of climate change.4. The four critical climate thrusts are:① Climate services for sustainable development② New frontiers in climate science and prediction ③ Dedicated observations of the climate system④ Studies of climate impact assessments and response strategies to reduce vulnerability.5. Future prospect
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    Chen Shupeng, Shao Yubin
    1996, 51 (s1):  15-25.  doi: 10.11821/xb1996S1002
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    At present, global change is the hot area in geo-science, at the same time, it is also one of the core pans ofgeo-informatics. Global change emphasizes the research on the interaction between the geo-spheres, such as theatmosphere, the biosphere and the hydrological sphere,and on the environmental impacts caused by human beings.Geographic information system(GIS), which has been developing very quickly since 1970s, has been applied to many areas of management of earth resources and environment. But now, GIS is still at its primary stage especially in China, for example only very few of GIS function has been used in the built GIS systems, such assome urban GIS systems built recently in China.From the historical view, that men observe and understand the earth is accelerating in many fields, such as advancement of observing techniques, acquired data amounts and quality etc.. In the space, the earth observingsatellites have been keeping on eyeing our planet and its changes. Much data has been gathered pretty enough formonitoring our environment, and only in this time the each could be studied and understand systematically and onthe global scale.The earth is a very complicated system. In the system much physical process, including gradual changes andsudden changes, exist and sometimes seem hard to predict, and in the unique system, human migration, materialflow, energy flow and information flow interact in its own wad. Observed dsta from space, which is vast andtheme diverse, becomes the base material source to understand global change systematically. But unfortunatelythese data are not fully studied at the present time because of data vastness and method deficiency. As a geospatial information system, GIS should be applied to solve complex problems in geo-science. In global change study, based on observed data of different scales, GIS should be applied tot nature modeling; human-earthrelationship study; pro.jecting and forecasting, and therefore facilitate the global change studies and decisionmakings in the sustainable development planning at present and in the future.
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    Chen Yufeng, Li Kerang
    1996, 51 (s1):  26-39.  doi: 10.11821/xb1996S1003
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    In this paper, the micro-static model of climate-vegetation response in China based on soil classification is used. At present, the model has been programmed by Visual Basic 4.0 language and has been coupled with theGIS/ICCF system developed by the authors. On the support of GIS/ICCF, the changes in distribution of vegetationtype in China based on scenarios for 2×CO2 are studied.(1) The percentage change in the area of each type is relatively small, with the biggest negative change(3.68%) in no vegetation region and the biggest positive change (6.39%) occurs in the cold prata, which is basedon GISS produced scenario. However, as for the relative change of absolute area ailer CO2 concentration isdoubled, there are great difference between the increase and decrease in the area of each vegetation type. Theareas of such types as temperate deciduous broadleaf forest and shrub, subtropical and tropical mountainousconiferous forest, tropical broadleaf forest, cold prata, annually double harvested or biannually tripe harvestedcrops, annually single(double) harvested cold-demanding rice etc., tend to expand, while the areas of such typesas cold temperate and temperate mountainous coniferous forest, subtropical evergreen broadleaf and deciduousbroadleaf mixed forest and shrub, mountainous shrub, temperate desert, cold desert, temperate prata, temperateprata and marsh, annually single harvested crop, annually double harvested rice or warm-demanding dry cropaccompanied with rice tend to shrink.(2) Based on GFDL and GISS produced scenarios of doubled CO2, the lower limit of distribution ofsubtropical and tropical mountainous coniferous forests, tropical broadleaf forest etc., will slightly increase byabout 150m~350m and 280m~560m, respectively; the lower limit of distribution of temperate deciduous broadleafand shrub, mountainous shrub, annually double harvested rice or warm-demanding dry crop accompanied withrice and no vegetation region will decrease by about 60m~900m; the lower limit of distribution of other typesbasically keeps unchanged. Meanwhile, the upper limit of distribution of such types as temperate deciduousbroadleaf forest and shrub, temperate desert, annually single harvested irrigated and dry crops etc., will increaseby 100m~600m; the upper limit of distribution of such types as subtropical and tropical coniferous forests, andtropical broadleaf forest, will decrease by 100m~1000m; the upper of limit of distribution of other types basicallykeeps unchanged.(3) Four indices of eastern, western, southern and northern boundaries is used to describe the horizontaldistribution of vegetation types in China.(I) Based on various scenarios of doubles CO2, the changes in eastern boundary are similar. Except the typessuch as annually double harvested irrigated and dry crops will shift toward west by 4.6° longitude, the other typeswill extend toward east to some extents, among which temperate deciduous broadleafforest and shrub shift towardeast to the largest extent, by about 8°~9°longitude, cold temperate and temperate mountainous coniferousforested shift toward eaSt to the least extent, by only 0.5°~1°longitude.(II) On the average, based on GFDL produced scenario, the Western boundary of vegetation in China willshift towards west by 0.5°~12° longitude, with the average of about 3.6° longitude, based on GISS producedscenario. the western boundary of .vegetation will shift by 0.I°~12° longitude toward west. with the average ofabout 5.2° longitude: based on OSU produced scenario, the western boundary of vegetation will shift by about0.5°~5° longitude toward west, with the average of about 2.4° longitude.(III) The change in the southern boundary of vegetation in China. based on various scenarios produced byGCMs, are also similar. Due to doubled CO2, mountainous shrub. temperate desert, cold desert and temperategrassland will move toward south. The southern boundaries of other types will either keep unchanged or shrinkback toward north. In general, the range of extending toward south is mostly within 0.5-2.5
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    Li Kerang, Chen Yufeng
    1996, 51 (s1):  40-49.  doi: 10.11821/xb1996S1004
    Abstract ( )   PDF (517KB) ( )   Save
    The analysis of vulnerability of ecosystem in response to global climate change is one of the most concerned issues in ecology and climatology. We discussed the concept of vulnerability, sensitivity, adaptability and their assessment method. The vulnerability is affected not only by climate sensitivity but also by structure, functioning and succession of the system as well as its self-adjusting and recovering abilities. In the assessment ofvulnerability, two aspects are usually included, i.e., present and future vulnerability, in the former assessment, theimpact of various present factors on self-adjusting and recovering abilities of vulnerable forest ecosystem isassessed, while in the latter assessment the impact of future climate change is assessed. Indexes of presentvulnerability include quality of forest land, forest age, supply and demand of fire-wood and forest fire. The qualityof forest land reflects the appropriate land condition for forest growth and potential of production, especially theconditions of soil, moisture and temperature. Here we use the third grade of land quality as the vulnerable index.In the timber, the area and amount of growing stock of young-aged and middle-aged forest make up too largeproportion while those of over-matured forest make up too little proportion, indicating the forest is easily affectedby environmental factors and extreme events. Forest fire is a kind of very dangerous disaster. Because of itsserious damage, it becomes the direct cause leading to vulnerability. The region with too tow of firewood is easilydamaged by human activities. Therefore it is the potential vulnerable area.Indexes of change of vulnerability in response to future climate change include the change in the vegetationtype, the decreasing of the forest productivity and forest fire. Comparing the indices of forest type, productivityand tbrest tire in doubled CO2 condition with present indices, we can calculate the coefficients of vulnerability.The results show that the regions of present and future vulnerability in China mainly distribute in thesouthwest China, south Chin4 central China, and the northeast China.
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    Deng Huiping, Wu Zhengfang
    1996, 51 (s1):  50-57.  doi: 10.11821/xb1996S1005
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    The changes of daily maximum, minimum temperature and daily precipitation are the basis of evaluating the climate change impacts on various extreme events in a CO2 doubling environment. In this paper, two stochasticsimulation models are developed for daily maximum and minimum temperature and daily precipitationrespectively.Based on present correlative equations between monthly averages of mean temperature and maximum or minimum temperature and scenario predicted by UKMO, monthly averages of maximum and minimum temperature are calculated in CO2 doubling situation. After that, A new set of annual cycle parameters are estimated while other two component's parameters are unchanged in CO2 doubling condition.As to daily precipitation simulation, monthly one-order Markovian chain transition matrices for wet and dry transition probabilities are derived from historical daily precipitation records. Then, precipitation values aregenerated by daily precipitation distributions. To reflect the climate change scenario, mean monthly precipitationis changed according to UKMO GCM outputs in daily precipitation distributions.The 100 year daily maximum and minimum temperatures can be decomposed three components. They areseasonal cycle, a sequence of several-day-time scale waves and random fluctuation components. Seasonal cyclecan be derived with a Fourier series. When higher harmonics are excluded, seasonal cycle is represented by theannual cycle. When the seasonal cycle is removed from the temperature data, short-time scale waves are apparent.A wave is approximated by a linear rising limb and a falling limb. After the annual cycle and short-time scalewaves are removed from temperature data, the residual value is random component. Each component can begenerated stochastically by producing various new parameter according to their probability distributions whichobtained from daily maximum or minimum temperature records of many years. After three components aresummed. the daily temperatures are produced. At present, GCMs only predict with some certainty a change in themonthly mean temperatures.100 year daily maximum, minimum temperature and precipitation values of seven stations in China aregenerated stochastically in present and CO2 doubling situations. The results have showed in CO2 doublingenvironment daily maximum and minimum temperature will increase 5 ℃~10℃ in seven places. The extremehigh temperature events will increase greatly while extreme low temperature events decrease obviously. Dailyprecipitation will change a little.
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    Chen Yufeng
    1996, 51 (s1):  58-65.  doi: 10.11821/xb1996S1006
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    In this study, we take the particular species of forest──Picea purpurea as an example to investigate the sensitivities of climate-forest response process using FOREC model. Thus we can evaluate the performance of our model.(1) Under climatological mean condition without annual change, from the beginning to 200th years, the competition among species is very intensive so that Picea purpurea, Picea asperata and Larix potaninii etc. formdominant species, constituting evergreen and deciduous broadleaf mixed forests, which is in reasonableagreement with observation and field investigation.(2) Under climatological mean condition with randomly annual changes, affected by the intensive climatechange, Picea purpurea community is in dynamic succession process from start to end. In the succession processBetula albo-siensis and Populus dovidiana firstly become pioneer species, then picea purpurea and Piceaasperata develop and grow, sometimes with continuously updating potential for Picea pumurea. The respondingtime of Picea purpurea community to the intensive climate change is about 20~40 years, during which period thestructure and biomass of Picea purpurea also change dramatically.(3) Under climatological mean condition with periodic annual change, the periodic changes in climatebackground produce substantially periodic changes in the succession of Picea purpurea community. Picea purpurea, Picea asperata and Betula albo-siensis are still the dominant species. However, in the composition offorest the propotion of Picea asperata is sometimes larger than Picea purpurea, which does not occur in the abovetwo experiments, indicating that climate change can have influence not only on the biomass of community butalso on the change of structure of forest in the community.In a word, the forest gap model (FOREC) can well reproduced the composition of forest stand of PiceQpurpurea and its succession, which is in reasonable agreement with observation, indicating that the model ispracticable in the study of forest community.
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    Zhu Zhihui
    1996, 51 (s1):  66-72.  doi: 10.11821/xb1996S1007
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    In this paper, the Beijing model was used to elucidate the distribution of the net primary productivity (NPP) of natural vegetation in China. The range of NPP in each vegetation region was given. A graphicmodel was proposed to explain the coupling relations among climatic factors, NPP and vegetation types.The results indicate that the functional combination of net radiation and radiative dryness index may not only determine NPP, but also elucidate basically the ordinal range of vegetation types. In study for vegetation distribution and regionalization, NPP index can be introduced as an effective tool by which somerelevant regulations may be elucidated simply and directly. Furthermore, Beijing model can also be used tostudy the impact of climate change on vegetation if we express the net radiation in terms of biotemperatureor potential evapotranspiration. In such a case, we can compare Beijing model with Holdridge's "life zones" scheme.
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    Chen Yufeng, Li Kerang
    1996, 51 (s1):  73-80.  doi: 10.11821/xb1996S1008
    Abstract ( )   PDF (326KB) ( )   Save
    FOREC model is a powerful tool in the study of response of forest community to climate change. It can simulate the change in forest composition and biomass due to climate change, and furthermore can assess possible impact of global climate changes on forest. Chinese scientists previously adopted macro-static models to study the influences of climate change on forest. Now, they started to develop dynamic models in the recent two years. In this paper, based on the studies using FQREC model, the possible changes in structure and biomass of forest community are simulated under climate change scenarios. PI’cea purpurea community is again used as an examples.The studies indicate that the different clilllatological states will lead to different changes in the succession aswell as the biomass of community. It is thought that one of the main reasons is due to the difference between thechanging rate of basic climate change state and the increase in global climate change.(1) If the increase in global climate change is greater than the changing rate of basic climate state, theecological phase of community will the general decrease in the biomass of species. In this typical study, the timeof succession among species in the community will fundamentally be shorter than the time of global climatechange (i.e., the time when CO2 concentration doubles).(2) If in case opposite above, the ecological phase of community will still be in the proper extent.At this time,ifthe climate is suitable for some species in the community, the succession of domain species as well as the basicwill happen among the existing species, instead of the intrusion of other species.(3) In this study, water capacity is the factor that has greatest impact on forest community in the mountainousarea in Southwest China. For any community types and structure oftbrest stand, decrease in precipitation will leadto reduce the capability of species in the community while warming and no change of precipitation will increasebiomass.
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    Wu Zhengfang, Deng Huiping
    1996, 51 (s1):  81-91.  doi: 10.11821/xb1996S1009
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    Based on the establishment of water-temperature function with GDD(Growing degree-days) and PER(Rate ofpotential evapotranspiration), this paper analyzed climatic suitability of current distribution of broad-leaved Pinus koraiensis forests and assess responses of the distribution to climate change(GCMs scenarios).The result show that distribution area of broad-leaved Pinus koraiensis forests will shrink greatly, and climatic suitability decreasewithin the area, and the southern boundary of the forests shift northward about l~2 latitude degrees under fourclimate change scenarios. By using Forest GaP Model, the dynamic responses of the forests to climate change aresimulated. Within 4℃ warming, the biomass(t/hm2), especially the biomass of Ptnus koraiensis, increase quickly,and biomass of some coniferous species, such as Picea jzoensis and Ables nephrolepis, will decrease and somebroad-leaved species increase during 100 modelling years. When warming over 4℃, the biomass decrease greatly,and Pinus koraiensis and other coniferous species will be replaced by broad-leaved species, and broad-leaved Pinus koraiensis forests change to broad-leaved forests.
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    Xu Xiaogding, Shao Xuemei
    1996, 51 (s1):  92-101.  doi: 10.11821/xb1996S1010
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    This article describes the preliminary analysis of the possible impact of air temperature increase on treegrowth using dendroclimatic methods. Residual tree ring-width chronologies of Changbai larch from the north slope of Changbai Mountain, Jinn province and of sargent spruce from the east slope of Gongga Mountain,Sichuan province are involved in this study. The relationships between tree groWth represented by ring-widthindex and climate elements including monthly mean air temperatures and monthly total precipitation were studiedby response function and correlation function of dendroclimatology. The results indicate that both species aresensitive to temperature. Based upon the regression equation developed between ring-width index and selectedmonthly mean temperatures, the percentages of increase in radical growth of tree were estimated with airtemperature going up 1℃, 2℃, 3℃, respectively. This estimation is upon the assumption that air temperaturewill go up due to CO2-induced climatic change. Using experiential equation of the two studied species, theincrease percentages in volume of tree were also estimated from changes in diameter of tree. The results show thatwhen air temperature goes up 1℃, 2℃, and 3℃, respectively, Changbai larch will increase by 9.2%, 15.7% and22.3% in diameter and 24.4%, 44.7% and 66.3% in volume. For sargent spruce, the percentages for diameterincrease arc 5.3%, 10. 1% and 14.9% and 13.g%, 27.3%, 41 .6% for volume increase. Obviously, with the samescenario Changbai larch grows more rabid than sargent spruce in the study area.
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    Wu Zhengfang, Deng Huiping
    1996, 51 (s1):  102-108.  doi: 10.11821/xb1996S1011
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    Accumulated temperatures and their lasting days are important indexes in agriculture. Due to doubling of CO2 concentration in the atmosphere, temperature will increase and will result in the changes of accumulated temperatures and lasting days, We applied a stochastic simulation model for daily mean temperatures to evaluate the impacts of climate changes on accumulated temperature and correspondent lasting days. Daily meantemperatures can be decomposed in to three components. They are seasonal cycle, a sequence of several- daytime scale waves and random fluctuation. Each component can be generated stochastically by producing variousnew parameters according to their probability distributions which are obtained from daily mean temperaturerecords of many years. After three components are summed, the daily temperatures are produced. At present,GCMs only predict with some certainty changes in the monthly mean temperatures. Thus, only the monthly andyearly mean temperatures will be modified under 2×CO2 situation.With the stochastic simulation models and scenario predicted by UKMO, 100 year daily mean temperaturesare generated in present and CO2 doubling situations respectively. With the generated daily mean temperaturevalues, the changes of lasting days and accumulated temperature are calculated. The results show in CO2 doublingenvironment, ≥0℃ and ≥10 ℃ accumulated temperatures and lasting days will increase with the mean monthlytemperature increase.The present correlative relationship between accumulated temperature and lasting days also will changes. Ifthis relationship is used in CO2 doubling condition, the present corrective equations should be adjusted.
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    Li Kerang, Chen Yufeng, Liu Shirong, Guo Quanshui, Yuan Jiazhu
    1996, 51 (s1):  109-119.  doi: 10.11821/xb1996S1012
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    Many studies indicated that global Climate change has a great impact on the horizontal and vertical distribution of forest, forest structure and forest productivity. However, as pointed out in IPCC reports, there are many uncertainties in the study of climate model and therefore their prediction of the climate impact. Because of the above facts, researches on mitigation and adaptation strategy and our actions are very important.Where there are threats of serious or irreversible damage, lack of full scientific certainty should not be used as a reason forpostponing such measures. We should prevent trouble before it happens. We should take precautionary measuresto anticipate, prevent or minimize the causes of climate change and mitigate its adverse effects.Six mitigation and adaptation strategies of forestry in China have been given in this paper. They are:Expanding afforestation and mitigating the frequency and intensity of climate change and climate disaster,Selecting and breeding fine variety and planting heliophilous drought-enduring species; Management andprotection of secondary regenerated forests and natural forests; Thinning and rotation management; Plantingfirewood forest; Prevention and control of forest fire, pests and diseases.
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    Dong Yunshe, Peng Gongbing, Li Jun
    1996, 51 (s1):  120-128.  doi: 10.11821/xb1996S1013
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    Using the enclosed chamber technique, CO2, CH4 and N2O soil fluxes were measured during one year in a forest near Darmstadt, Germany. Fluxes measurements were made before (undisturbed forest soil) and after the removing of soil litter (leaves and humus layer) form the forest floor (disturbed soil). Gas fluxes from the removed leaves and humus were also measured. CH4 and N2O soil air concentration and soil moisture profile were measured during the period July to December.The average Fluxes from undisturbed forest soils are: 2800gCO2/(m2.a),-0.64gCH4/(m2.a), and 0.05gN2O/(m2a). With the exception of N2O signific4nt seasonal variation were observed, with the higher fluxes during thesummer. In general, the fluxes obtained in Darmstadt are in agreement with values reported for similar temperateforests. CO2 and CH4 fluxes show a significant dependence to changes in ambient temperature, whereas N2Onuxes increase with soil moisture ranging between 7% and 20%, with an abrupt decrease at 22%. A goodcorrelation between CO2 production and CH4 consumption was observed, suggesting that methane uptake by soilsis related with the soil respiration process. No relationship was found between N2O emissions rates and CO2 orCH4 fluxes.Very similar profiles of CH4 in soil air (exponential concentration decrease with depth) were observed in allmeasurements, whereas N2O profiles were highly related to the changes in soil moisture, e.g. higher concentrationof N2O were found at the 20 to 50cm layer, during periods when the layer 0 to 15cm had relatively high soilmoistures.when the leaves and the layer of humus were removed from the forest floor, significant changes in thefluxes were observed, indicating that the litter layer plays an important role in the soil-atmosphere interaction. Inthe disturbed soil, CO2 and N2O emissions decrease in average by 23% and 50%, respectively, and CH4consumption increase by 17%. The decrease of CO2 emission is likely related to the activity of the removed humuslayer, that emits CO2, however, the reduction in N2O emission should to be mainly related to changes in theconditions (e.g. increase of oxygen concentration) in the active soil layer. Leaves and humus neither emit norconsume significant amounts of CH4 and the increase of CH4 consumption in the disturbed soil should be mainlydue to an increase of the transport of atmospheric CH4 (and O2) to the region where methane is consumed. Adecrease of the humus layer during last decades, due to effects of air pollution, has likely produced an increase ofthe consumption of atmospheric CH4 by forest soils.
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    Liu Shirong, Guo Quanshui, Wang Bing
    1996, 51 (s1):  129-140.  doi: 10.11821/xb1996S1014
    Abstract ( )   PDF (773KB) ( )   Save
    An introduction of methodology and techniques being adopted for experimental investigation of plants and ecosystems to elevated CO2, including genetically manipulation, controlled environmental facilities, branch bags or chambers, open-top chambers, free-air controlled enrichment system, natural CO2 vents, and eddy covariance measurement, was briefly made. The ultimate results of internationally current studies on elevated atmospheric CO2 was reviewed with respect to responses of cells, leaves, individual plants. Most early experiments on CO2 enrichment of trees were done in the same ways on agricultural crops, using potted juvenile seedlings and fixednutrient capital, leading to constrained root groWth, nutrient limitation, poor coupling to the atmosphere and lackof sustained active sinks for photosynthate. Also, these experiments were generally done in the short term, insteadof gradual adaptation and acclimation Processes. All these contribute to a large variations observed inphysiological and growth response of plants to elevated CO2. Elevated CO2 induced decrease in stomatalconductance by a range of 10%-69%, and increase in growth by a range of 20%-120%. Broad-leaved trees aremore sensitive to elevated CO2 than conifers. Interaction between the responses of plants to elevated CO2 and theavailability of nutrient raise important questions. Changes in the balance between rates of uptake of CO2 and ofinorganic nutrient, especially N, may result in changes in the translocation of carbon and nitrogen within plants.Although nutrient has been increasingly involved in studies of the impact of elevated CO2 on plant growth,andphysiology, the quantitative effects of the rate of supply of nutrients are often neglected in experiment design,leading to difficulties interpreting CO2 responses and interactions between CO2 and nutrition.Recent experiments, by adopting the steady-state nutrition approach, demonstrated that there was no effectof elevated CO, on allocation of carbon between roots and shoots with a high rate of N supply, but that a highfraction of plant dry mass was found in roots, primarily in fine roots when the rate of N-supply was low. Thedown regulation of photosynthesis in parallel by decrease in rubisco activities occurred regardless of nitrogensupply.The acclimation process of photosynthesis to elevated CO2, the mechanism of CO2 regulating stomatalaction, and the long term-effects of interaction between carbon and nitrogen on growth and physiologicalresponses of plants to elevated CO2 were strongly recommended for future research.
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    Liu Shirong, Wang Bing, Guo Quanshui
    1996, 51 (s1):  141-150.  doi: 10.11821/xb1996S1015
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    World-wide current studies on responses of growth and competition of plant population and communities,exchanges of CO2 and water vapor between forest ecosystems and atmosphere to rising atmospheric CO2, and modeling forest response processes were reviewed in this paper.Gas measurement on crop population in response to elevated CO2 showed that photosynthesis and instantaneous water use efficiency (the ratio f photosynthesis to transpiration) were increased with increasing atmospheric CO2 concentration, but canopy conductance to water and CO2 exchange were reduced. These responses were accompanied with an increase in leave area index, dry mass and seed yield. Population grown at elevated CO2 was found to develop more quickly, reaching the stage of fruit production. The effect of CO2 on thetiming of flowering and floral initiation Was not fully understood. The influence of the interaction between CO2 concentration and population density on seed production varied with plant species. With increasing populationdensity, the positive effect of elevated CO2 on seed production was increased, but negative response occurredwhen competitive species introduced. Very limited research on population differences in CO2 responses indicated that within-and between-population differences were observed in the responses of the root to shoot ratio,seed weight, seed germination, leaf expansion and growth rate.Ideal research on response of plant community to elevated CO2 was nearly impossible due to technical and practical problems as well as costs. Thus, the logical approach to study community responses to elevated CO2 depended on developing ideas and theories from the population level of study. The response of a C3 and C4community to elevated CO2 concentration was different regardless of using open-top chambers and in thecontrolled environment. In a community consisting of C3 and C4 species, the growth and productivity of the C3 species was increased at elevated CO2 concentration, particularly when in competition with the sensitive C4 species. The leaf C/N ratio with CO2 concentration resulting from a decrease in leaf nitrogen and protein wasincreased, and this increased the rate of leaf herbivore and the quantity of plant tissue consumed. These responsescould eventually lead to significant alterations in community structure and functioning.Experimental approaches can not directly employed to study ecosystem or biome response to risingatmospheric CO2 concentration such as those instituted for plants, populations and communities, but the effectscan alternatively be achieved by remote observations of ecosystem optical reflectance. The seasonal changes inatmospheric CO2 concentration were considered as a good estimators of ecosystem CO2 exchange. Finallyrecommendations for future research was discussed, in which development of appropriate bottom-up models ofecosystems incorporating ecological feedback processes was strongly signified.
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    Deng Huiping, Zhang Yi, Tang Laihua
    1996, 51 (s1):  151-160.  doi: 10.11821/xb1996S1016
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    For the purpose of evaluating impacts of climatic changes on hydrologic extremes, a stochastic simulationmodel for daily runoff is developed. As a stochastic variable, based on the linear model, daily runoff time series consists of a long-term climatic trend, seasonal cycles, a sequence of daily time scale waves, persistence andrandom fluctuation component. For analysis of effects of monthly average changes on daily scale events, thestatistical relationships between monthly runoff and daily maximum runoff are investigated. The results obviously show that there are statistical relationships between monthly runoff and daily time scale waves. Such statisticalrelationships are taken into account when stochastic functions between the rising range and the rising duration ofdaily scale waves. Thus, this daily stochastic model includes not only the effects of monthly average changes onseasonal cycle but also the effects of monthly average changes on extremes.At last, with this daily-runoff simulation model, a case study of impacts of climatic changes on flood anddrought frequencies is conducted. Results show that flood frequencies will decrease while various drought eventswill in crease.
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    Deng Huiping, Wu Zhengfang, Tang Laihua
    1996, 51 (s1):  161-170.  doi: 10.11821/xb1996S1017
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    One of the most important consequences of global climatic changes caused by increases in atmospheric trace gas concentrations is alterations in regional hydrologic cycles and subsequent effects on the quantity and quality of regional water resources. The impacts of climate change on hydrology and water resources have gained widespread attentions of scientists and governments since recent ten years. In this paper, We review the studies of the impacts on hydrology and water resources, including the researchmethodologies, research contents, achievements and inadequacies of past research works.The methodology of impact assessment is to use future climate scenarios, which can be generatedusing GCMs outputs, recent climate analogue data, paleoclimate data and hypothetical climate data, asinputs to more detailed regional models to assess the impacts of climate changes on hydrological cycles and water resources. In spite of different scenarios and hydrologic models employed by researchers, three research results are in common.Due to the complexity of water resource management and the uncertainty of future climate changes,little research has been done in assessment of effects of climate changes on water resource management.Past hydrologic assessments focused on monthly-time scale or longer time scale average changes,rather than on daily-time scale changes. How -climate changes will affect extremes is almost unknown.
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