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Table of Content
    Volume 31 Issue 6
    30 November 2007
      
    Research Articles
    REVIEW OF ADVANCES IN ECOLOGY OF SEED MASS
    YU Shun-Li, CHEN Hong-Wei, LI Hui
    Chin J Plant Ecol. 2007, 31 (6):  989-997.  doi:10.17521/cjpe.2007.0126
    Abstract ( 3549 )   Full Text ( 10 )   PDF (312KB) ( 2708 )   Save
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    Seed mass is a key attribute of plant species, and study of relationships between seed mass and other plant traits and ecological characteristics has become a practical problem and an interesting topic in evolutionary biology. Seed mass (or size) is related to other plant traits and community characteristics, including seed dispersal capacity, seed dispersal mode, plant growth form, leaf area index, abundance of seeds or plant individuals in a community, seed predation, seed dormancy and seed persistence in soil seed banks, net primary productivity, etc. Variations in seed mass have been related to latitude, longitude, altitude, temperature, precipitation, slope aspect, light environment, etc. Seed mass is thought to have evolved as a compromise between seed mass and number for a given amount of energy. Many studies support that seed mass has a closer relationship with plant growth types than other characteristics. Species that establish in shade have large seeds. Three patterns were found in the relationship between seed mass and seed predation. Four patterns were found in the relationship between seed mass and persistence in soil seed banks. During establishment, seedlings from larger-seeded species are better able to survive competition from established vegetation, deep shade, defoliation, mineral nutrient shortage, burial under soil or litter, drought, etc. Among species with seeds unspecialized for spatial dispersal, seed mass is unrelated to dormancy. However, in species with wind- or animal-dispersed seeds those with heavy seeds typically have less dormancy. This is consistent with heavy seeds having better establishment success and/or suffering higher levels of herbivory. Future research should focus on relationships between seed mass ecology and 1) plant phylogeny and plant taxonomy, 2) latitude, longitude and altitude, 3) community succession, 4) number of plant individuals and seeds, 5) microhabitats or microtopography such as forest gaps and slope aspect and 6) global climate changes.

    STUDY OF DISTANCE-DEPENDENCE ON CASTANOPSIS CHINENSIS SEED IN CONIFEROUS AND BROAD-LEAVED MIXED FOREST OF DINGHUSHAN, CHINA
    DU Yan-Jun, PENG Shan-Jiang, XU Guo-Liang, HUANG Zhong-Liang, HUANG Yu-Jia
    Chin J Plant Ecol. 2007, 31 (6):  998-1006.  doi:10.17521/cjpe.2007.0127
    Abstract ( 2845 )   Full Text ( 4 )   PDF (482KB) ( 1461 )   Save
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    Aims The Janzen-Connell hypothesis is that seed survival improves with increased distance from the parental plant. Our objectives were to determine whether the Janzen-Connell hypothesis (1) is supported by Castanopsis chinensis seed survival, (2) can forecast the population's distribution pattern, and (3) explains the reason for limited recruitment.

    Methods We selected three mature C. chinensis trees in coniferous and broad-leaved mixed forest of Dinghushan, China and recorded seed mortality with Open treatments (OP), Small Mammal Exclusion experiments (EM) and pathogen infection treatments at 3, 10, and 15 m from the trees.

    Important findings In the OP treatment, the number of missing seeds was largest at 10 m; however, seed predation was not significantly affected by distance from tree and seed size. In the EM treatment, few seeds were missing in the first week, and seed predation was not significantly affected by distance and seed size during the study period. In the first two months, seeds with Caoton treatment remained intact, and from the third to the sixth month, the number of seeds infected by pathogens was significantly affected by distance and disinfecting action. After the sixth month, the number of seeds infected by pathogens was relatively constant. These results illustrate that pathogens are related to mortality of seeds of C. chinensis and that this mortality is distance dependent, while the mortality caused by vertebrate animals is not distance dependent.

    SELECTIVE ABORTION AND ITS EVOLUTIONARY, ECOLOGICAL SIGNIFICANCE IN SEED PLANTS
    ZHAO Xue-Jie, TAN Dun-Yan
    Chin J Plant Ecol. 2007, 31 (6):  1007-1018.  doi:10.17521/cjpe.2007.0128
    Abstract ( 3926 )   Full Text ( 15 )   PDF (606KB) ( 2454 )   Save
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    Selective abortion in seed plants means selective abortion of developing fruits/seeds based on pollen source, order of pollination, location of fruits on plant, number of developing seeds, or some combination of these. In species with linearly arranged ovules, such as occurs in members of Fabaceae, embryos at the peduncular, stigmatic, or both ends of the fruit can be selectively aborted. Position of fruit within the inflorescence also has a marked effect on abortion. Selective abortion has been documented in many species of Fabaceae, Brassicaceae and Boraginaceae. The primary factor causing selective abortion of fruit and/or seeds is resource limitation. Competition for limited maternal resources occurs among fruits and seeds. Thus, those that are initiated first and have the faster rate of growth can capture more maternal resources and thus are less likely to be aborted than those that are initiated later.+++Genetically correlated factors also can result in selective abortion. In some species, fruits from cross-pollinated flowers tend to have more seeds that are more likely to mature than fruits from self-pollinated flowers. Methods used to investigate selective abortion include 1) removing a fraction of the ovules at an early stage, 2) hand-thinning some young fruits or flowers, and 3) using molecule techniques of RAPD and isoenzyme analyses. Selective abortion can increase offspring quality. Progenies that are selectively matured have higher vigor, germinate to higher percentages, produce more leaves, inflorescences and flowers, and mature more seeds than those that are randomly matured. Aborting some seeds also can reduce wing load (ratio of fruit weight to fruit surface area), improve dispersal distance, and decrease sibling rivalry. Thus, selectively aborting some selfed and/or inferior genotype fruits/seeds increases the fitness of the maternal plant, its offspring, or both. Therefore, research on selective abortion is important to understanding patterns of fruit-set and/or seed-set and its evolutionary pattern and mechanism in angiosperms.+++We review recent advances in selective abortion research in angiosperms, with emphasis on 1) patterns of selective abortion; 2) factors affecting selective abortion; 3) evolutionary, ecological significance of selective abortion; and 4) primary methods used to investigate selective abortion. We also discuss prospects for further research.

    DIASPORE CHARACTERISTICS AND DISPERSAL STRATEGIES OF 24 EPHEMERAL SPECIES OF BRASSICACEAE IN THE JUNGGAR DESERT OF CHINA
    LIU Xiao-Feng, TAN Dun-Yan
    Chin J Plant Ecol. 2007, 31 (6):  1019-1027.  doi:10.17521/cjpe.2007.0129
    Abstract ( 3318 )   Full Text ( 8 )   PDF (620KB) ( 2212 )   Save
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    Aims Members of Brassicaceae are one of the most important groups of ephemeral plants in the Junggar Basin and serve many ecological roles in the desert. However, studies on dispersal syndromes of Brassicaceae, especially the ephemerals, are rare. This study addresses the following questions: 1) what are the dispersal unit and the dispersal mode of these species, 2) what are the spatio-temporal patterns of dispersal of these species and 3) how are these characters adaptive to the arid desert environment?

    Methods The study was conducted on 24 ephemeral species of Brassicaceae from June to October 2005 and 2006. We observed and recorded 1) morphology of the fruits and seeds, 2) dehiscence mode of the fruit, type of dispersal unit and accessory structures and 3) dispersal mode and its duration in natural habitats.

    Important findings The dehiscence mode of fruit depends on degree of lignification. There are three types of dispersal units of the species whose pods cannot dehisce. Species whose dispersal unit is the fruit node are autochorous. Species in which dispersal occurs by the whole fruit have silicula. Some do not have accessory structures to dispersal, and the dispersal mode is autochorous. Others have wings or hairs and disperse by wind. Species whose dispersal unit is a section of the infructescence also have silicula with a hard and hook-like beak that can attach to the coat of animals. Species with pods that dehisce easily only disperse by seeds. Their seeds have three types. One type is tiny without any accessory structures for dispersal, and seeds are dispersed by wind. Seeds in the second type have wings, and their modes of dispersal are diverse, but the main one is hydrochory. Seeds in the third type have wings and mucilage and are dispersed by anemochory and hydrochory. There are two types of dispersal patterns, depending on duration of dispersal. The first type is the short-term dispersal pattern in which all dispersal units on the plant are dispersed from the mother plant mainly in June and July. In the second type, dispersal units are shed from the mother plant from June to October or even the next spring. In this pattern, pods in the upper and lower positions of one infructescence differ in morphology, degree of lignification, kind of dispersal unit, dispersal time and dispersal mode.

    EFFECTS OF LIGHT ON SEED GERMINATION AND SEEDLING ESTABLISHMENT OF A TROPICAL RAINFOREST CANOPY TREE, POMETIA TOMENTOSA
    YU Yang, CAO Min, ZHENG Li, SHENG Cai-Yu
    Chin J Plant Ecol. 2007, 31 (6):  1028-1036.  doi:10.17521/cjpe.2007.0130
    Abstract ( 3014 )   Full Text ( 4 )   PDF (526KB) ( 1635 )   Save
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    Aims Pometia tomentosa is the major dominant species in the tropical seasonal rain forests of Xishuangbanna, Southwest China. It is listed in the rare and endangered species in China. Research on seed and seedling ecology of P. tomentosa may provide information for rare and endangered species conservation and forest restoration.

    Methods Shade house and forest experiments were designed to investigate light effects on seed germination and seedling establishment of P. tomentosa. Seedling growth, biomass allocation and physiological properties of P. tomentosa were examined in neutral-density shade houses, which were used to mirror different light levels in centers of forest gaps, at edges of forest gaps and forest understory.

    Important findings Results showed that final seed germinations in all treatments were greater than 95% and occurred within six days. Seedlings in 30% light treatment had the highest root mass ratio (RMR) and stem mass ratio (SMR). However, seedlings in 10% and 3.5% light treatments had the highest leaf mass ratio (LMR). Seedlings grown in low light environments (such as 10% and 3.5% light treatments) had a higher leaf area ratio (LAR) than those in high light (30% light treatment). Seedlings in 30% light treatment had the highest maximum photosynthetic rate (Pnmax), dark respiration (Rd) and light saturation point (Isat), but the compensation point (Icomp) was not significantly different among the three light treatments. Seedlings of P. tomentosa were able to grow slowly and survive for a long time; therefore, it is a shade tolerant species. Also, seedlings of shade houses showed increased RGRM and RGRH in high light comparing with low light. It is concluded that gaps in the forest canopy are probably necessary for successful regeneration of P. tomentosa. Soil moisture also may affect the habitat selection of P. tomentosa seedlings.

    COMPARATIVE STUDY OF SEED GERMINATION, SEED SIZE AND THEIR RELATIONSHIPS IN MESAD AND SICCOCOLOUS
    WANG Ju-Hong, CUI Xian-Liang, CHEN Xue-Lin, DU Guo-Zhen
    Chin J Plant Ecol. 2007, 31 (6):  1037-1045.  doi:10.17521/cjpe.2007.0131
    Abstract ( 3539 )   Full Text ( 8 )   PDF (418KB) ( 2669 )   Save
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    Aims Seed germination and seed size are crucial plant life history traits related to seedling establishment, survival, competition and fitness. Study of germination ecology of native species not only increases understanding of seed traits, reproductive strategy and physiological adaptation, but also can be applied in ecological restoration. Mesad and siccocolous species with different water requirements may have different life-history strategies to respond to different selective pressures. Our main purposes were to determine: 1) differences in germination characteristics between mesad and siccocolous species in the arid and semiarid zone and 2) relationship of germination to seed size.

    Methods Seeds of 42 mesad and 22 siccocolous species from the Hexi Corridor of Northwest China were air-dried, cleaned and stored at room temperature about 3-4 months and then stored at 2-4 ℃ for 40 d. Germination was determined under an alternating temperature regime (25 ℃/5 ℃; 12 h light/dark). Four main germination indices were recorded: germination percentage, germination rate, days to first germination and germination period. PCA was used to survey the germination patterns of the 64 species, and Pearson Correlation Analysis was used to determine the relationship of seed size and germination.

    Important findings There are four main germination patterns: rapid, intermediate, slow and low germination. Low germination percentages (≤20%) were found in 14.28% mesad and 50% siccocolous. There are significant differences in seed size between mesad and siccocolous (p=0.003). There also is a significant negative correlation between germination and seed size in mesad, with smaller-seeded species having higher germination percentages (r=-0.467**, p=0.002) than larger-seeded ones, but not in siccocolous (p>0.05). Findings indicate that mesad and siccocolous species under different water conditions are subjected to different selective pressures and have evolved different life-history strategies.

    SEED POLYMORPHISM AND GERMINATION BEHAVIOR OF SALSOLA BRACCHITA, A DOMINANT DESERT ANNUAL INHABITING JUNGGAR BASIN OF XINJIANG, CHINA
    WANG Hong-Fei, WEI Yan, HUANG Zhen-Ying
    Chin J Plant Ecol. 2007, 31 (6):  1046-1053.  doi:10.17521/cjpe.2007.0132
    Abstract ( 2882 )   Full Text ( 1 )   PDF (429KB) ( 1829 )   Save
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    Aims Salsola bracchita has four types of perianth-enclosed utricles, utricles and seeds. We investigated the role of utricle polymorphism in seed dispersal and germination to better understand how S. bracchita is adapted to its desert habitat.

    Methods Twenty plants of S. bracchita were selected randomly to observe the morphology of perianth-enclosed utricles, including persistence of perianth and wings, utricle shape and color and location of fruit on mother plant. Seeds of the four types were germinated in incubators with 12 h photoperiod and 12 h thermoperiods (dark/light) of 5 ℃/15 ℃, 5 ℃/25 ℃, and 15 ℃/25 ℃ for 20 d. Type D seed was scarified and then germinated for 20 d at the three different thermoperiods to determine its dormancy characteristics.

    Important findings Salsola bracchita produces four types of fruits (utricles) that differ in shape, size, seed color and external structure. Type A and B fruits can be dispersed by wind far from mother plants. Germination percentages of type A seeds at all three thermoperiods were >70%, and there were no significant differences (p>0.05). Germination percentages of type B seeds were all >68%, and there were significant differences (p<0.05), with highest germination percentage and germination index at 5 ℃/25 ℃ (dark/light) (>80%). Type C fruits have tepals without wings and are dispersed near mother plants. Germination percentages of type C seeds were all >80%, and there were no significant differences (p>0.05). Rate and final percentages of germination of type B and type C seeds were higher than that of type A seeds. Type D fruits also are mainly dispersed near mother plants. Freshly matured type D seeds are in physiological dormancy because its germination is slow and low (<20%). Seed coat scarification of type D seeds can hasten and increase the seed germination percentage (p<0.01) and germination index (p<0.01) in each of the thermoperiods.

    TEMPORAL RESPONSES OF VEGETATION TO CLIMATE VARIABLES IN TEMPERATE STEPPE OF NORTHERN CHINA
    LI Xia, LI Xiao-Bing, CHEN Yun-Hao, YING Ge
    Chin J Plant Ecol. 2007, 31 (6):  1054-1062.  doi:10.17521/cjpe.2007.0133
    Abstract ( 3232 )   Full Text ( 8 )   PDF (339KB) ( 1784 )   Save
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    Aims Vegetation has strong temporal response to climate variables in some regions. The normalized differential vegetation index (NDVI) is generally recognized as a good indicator of terrestrial vegetation, so it can be used to analyze temporal responses of vegetation to climate variables. This study addresses two key questions: a) How quickly and over what time period does NDVI respond to different patterns of climate variables? b) How does NDVI respond to weather variation for different temperate steppe types of northern China?

    Methods We calculated 1) linear correlations between monthly climate variables and NDVI for 1983-1997, 2) NDVI-precipitation correlation coefficients, with precipitation in four different time periods (1-4 months) and four different time lags (0-3 month lags) to evaluate the time period over which precipitation most strongly influences on NDVI and 3) NDVI-temperature correlation coefficients for the current and previous month.

    Important findings The correlation coefficients between NDVI and concurrent climate variables were all significant in three temperate steppe types. There is a strong relationship between precipitation and NDVI in temperate steppe of northern China. Correlation coefficients between NDVI and precipitation are high for specific combinations of time duration and lag. In terms of time lag, NDVI was most strongly related to the previous month, although differences existed among different steppe types. In terms of time duration, NDVI was most strongly related to the sum of precipitation over three months than one, two or four month periods. Precipitation from February back to November of the previous year was positively correlated with NDVI early in the growing season in meadow steppe, and there was a strong correlation between NDVI and precipitation for the preceding 1-2 months in the mid and late growing season in desert steppe and typical steppe. Temperature was moderately correlated with NDVI during the growing season, but differences existed among steppe types. For typical steppe and meadow steppe, temperature was positively correlated with NDVI early in the growing season. For desert steppe, NDVI was moderately related with temperature early in the growing season and negatively correlated with temperature in the mid growing season.

    LANDSCAPE CHANGES IN A DEGRADED SANDY LAND ECOSYSTEM—A CASE STUDY IN THE OTINDAG SANDY LAND, INNER MONGOLIA, CHINA
    LIU Hai-Jiang, CHENG Wei-Ming, LONG En
    Chin J Plant Ecol. 2007, 31 (6):  1063-1072.  doi:10.17521/cjpe.2007.0134
    Abstract ( 2614 )   Full Text ( 3 )   PDF (1226KB) ( 1176 )   Save
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    Aims Landscape pattern can indicate ecosystem changes. The Otindag Sandy Land, which is located in the southeastern Inner Mongolia Plateau, has been degraded by overgrazing in the past two decades. The purposes of this study are to 1) analyze spatial-temporal dynamics of landscape pattern, 2) determine whether landscape pattern can be used as an indicator of ecological degradation, and 3) explore underlying ecological processes that triggered alteration of landscape pattern.

    Methods Our approach integrated remote sensing and geographic information system (GIS). The basic sources of data were two Landsat TM/ETM+satellite images from 1987 and 2000 and field data collected in summer 2001 and 2002. From the images, we distinguished six landscape types within our study area: grassland, fixed sandy land, semi-fixed sandy land, mobile sandy dune, shrub and water body. We performed a supervised classification procedure to derive landscape maps. Using GIS, we analyzed the resultant landscape maps by change detection analysis and transition matrix analysis.

    Important findings Great change occurred at our study area from 1987 to 2000. Total area of grassland, fixed sandy land and semi-fixed sandy land decreased and patch fragmentation increased. Total area of mobile sandy dune increased about 2.5 times and patches expanded and combined into two sand belts. Change detection showed the same tendencies. Transition of landscape types included grassland converted mainly to sandy land, fixed sandy land transformed into semi-fixed sandy land and semi-fixed sandy land changed mainly to active sandy land. The ecosystem in this region seriously degraded from 1987 to 2000, and effective measures should be taken to prevent further environmental deterioration.

    EFFECTS OF LAND DEGRADATION AND REHABILITATION ON VEGETATION CARBON AND NITROGEN CONTENT OF ALPINE MEADOW IN CHINA
    WANG Wen-Ying, WANG Qi-Ji, WANG Gang, JING Zeng-Chun
    Chin J Plant Ecol. 2007, 31 (6):  1073-1078.  doi:10.17521/cjpe.2007.0135
    Abstract ( 2953 )   Full Text ( 2 )   PDF (270KB) ( 1370 )   Save
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    Aims Our objectives were to compare vegetation biomass and total carbon and nitrogen content of severely degraded grassland and undisturbed Kobresia meadow, and to measure the relative influence of various rehabilitation practices on vegetation biomass and carbon and nitrogen content in early secondary succession.

    Methods The research was conducted on alpine meadows in Dari County, Qinghai Province, China, using five treatments: undisturbed native meadow, severely degraded grassland, and three grasslands rehabilitated by different practices (mixed seeded, single seeded and natural recovery). In each treatment, vegetation C and N contents were calculated on an area and depth basis from biomass samples and plant concentration analyses.

    Important findings In the undisturbed native meadow treatment, total aboveground biomass was 265.1 g·m-2 and root biomass in the uppermost 30 cm averaged 6 982 g·m-2. In the severely degraded grassland treatment, above ground biomass was only 139.9 g·m-2 and root biomass was only 916 g·m-2. Total aboveground biomass in the mixed seeded, single seeded and natural recovery treatments was 307.1, 179.9 and 200.4 g·m-2, and root biomass was 1 323, 1 169 and 1 412 g·m-2, respectively, after seven growing seasons. Total C content of vegetation in the undisturbed native meadow was 3 067.42 g·m-2, while that of the severely degraded grassland treatment was only 414.07 g·m-2. Therefore, land degradation leads to loss of 86.5% of the original plant tissue C. In addition, land degradation leads to loss of 68.3% of the original plant tissue N. Compared with the severely degraded land, mixed seeded and natural recovery treatments partly recover C and N content, indicating that they may be alternative approaches to sequestering C in former degraded alpine meadow.

    PREDICTING POTENTIAL DISTRIBUTIONS OF DOMINANT WOODY PLANT KEYSTONE SPECIES IN A NATURAL TROPICAL FOREST LANDSCAPE OF BAWANGLING, HAINAN ISLAND, SOUTH CHINA
    ZHANG Zhi-Dong, ZANG Run-Guo
    Chin J Plant Ecol. 2007, 31 (6):  1079-1091.  doi:10.17521/cjpe.2007.0136
    Abstract ( 3105 )   Full Text ( 5 )   PDF (563KB) ( 1654 )   Save
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    Aims Our major objectives were to 1) identify keystone species within the context of functional groups, 2) develop potential distributional predictions for keystone species using ecological niche model, 3) confirm factors determining potential distributions of keystone species, and 4) test if the performances of ecological niche model are better than those of a random model and differ in predicting different keystone species.

    Methods Based on the investigation of 135 plots in a natural tropical forest landscape, we classified woody plant functional groups based on successional status and potential maximum height. Keystone species within each functional group were identified using a dominance index (DI). We used the genetic algorithm for rule-set prediction (GARP) to estimate the keystone species' potential distribution and then used the receiver operating characteristics to evaluate predictive performance. Applying multiple linear regression analysis, we identified major factors determining potential distributions of keystone species.

    Important findings Identification of keystone species within pioneer species, climax shrub and emergent tree functional groups was clearer than within climax subcanopy and climax canopy tree functional groups. Generally, among the eight keystone species, pioneer species Melastoma sanquiueum, Aporosa chinensis and Liquidambar formosana (but not Adinandra hainanensis) have high probability of occurrence in the north, west and southwest regions of Bawangling. However, climax species Psychotria rubra, Ardisia quinquegona and Castanopsis hainanensis (but not Pinus merkusii) have high probability of occurrence in the central, southeast and south regions. Minimum and maximum temperature, mean annual temperature and precipitation, aspect and altitude were the key factors determining potential distributions of keystone species. Evaluation of GARP model's performance indicated excellent predictive ability of all eight keystone species' distribution. This study suggests the DI method is more suitable to identify keystone species within woody plant functional groups in which a single or a few species are dominant. Findings will assist decision makers in planning conservation and management policies in tropical rainforest areas.

    INFLUENCE OF ECOLOGICAL FACTORS ON DISTRIBUTION OF WOODY PLANT FUNCTIONAL TYPES IN A NATURAL TROPICAL FOREST LANDSCAPE, BAWANGLING, HAINAN ISLAND, SOUTH CHINA
    ZHANG Zhi-Dong, ZANG Run-Guo
    Chin J Plant Ecol. 2007, 31 (6):  1092-1102.  doi:10.17521/cjpe.2007.0137
    Abstract ( 2838 )   Full Text ( 3 )   PDF (433KB) ( 1503 )   Save
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    Aims The relative influence of ecological factors on the distribution of woody plant functional types in a natural tropical forest landscape is rarely explored. The three major objectives of this study were to 1) determine the relative importance of environment, anthropogenic disturbance and spatial influences on the distribution of woody plant functional types, 2) determine which variables influence distribution of woody plant functional types, and 3) examine the distribution of woody plant functional types in different habitats.

    Methods Using data from 135 plots in a natural tropical forest landscape of Hainan Island, South China, we classified woody plant functional types using the characteristics of species wood density and potential maximum height. Three sets were used, presence-absence, species richness and abundance. Their relations to environment, anthropogenic disturbance and spatial factors were analyzed with redundancy analysis (RDA). We then used a partial RDA with variation partitioning to specify which proportion of the variation in functional types distribution pattern is explained by each of the three factors individually and which proportion is attributable to interactions between factors.

    Important findings We found that environmental influence, anthropogenic disturbance and interaction between environmental and anthropogenic disturbance factors were of similar importance in functional types distribution. However, spatial influence and interaction between spatial and other factors were less important. Furthermore, we found that anthropogenic disturbance types, topographical factors, soil types, grit content, soil depth and X, Y coordinates all impacted the distribution of functional types. Generally, hardwood functional types are abundant in better, undisturbed sites, but softwood functional types occur in opposite settings. The distributional range of medium hardwood functional types is wider than the other two. Except for softwood shrub functional types, the others have high species richness and abundance in better sites, especially where soils are deep. This study suggests that the plant functional type approach enhances understanding of the relative influence of environment, anthropogenic disturbance and spatial factors on species distribution. Environment and anthropogenic disturbance are more important than spatial influence in the variation of species distribution. These conclusions can aid in developing large-scale conservation and management policies in tropical rainforest areas.

    CALORIC VALUES AND ENERGY ALLOCATION OF A TROPICAL SEASONAL RAIN FOREST AND A MONTANE EVERGREEN BROAD-LEAVED FOREST IN SOUTHWEST CHINA
    LIN Hua, CAO Min, ZHANG Jian-Hou
    Chin J Plant Ecol. 2007, 31 (6):  1103-1110.  doi:10.17521/cjpe.2007.0138
    Abstract ( 2965 )   Full Text ( 5 )   PDF (415KB) ( 1633 )   Save
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    Aims Energy allocation pattern is the basis for understanding energy flow processes in ecosystems. High structure complexity and species diversity of tropical forests, however, have resulted in little research on caloric values and energy allocation patterns in tropical rain forests. Tropical seasonal rain forest (TSRF) in Xishuangbanna, Southwest Yunnan is distributed on the northern edge of tropical Asia, and montane evergreen broad-leaved forest (MEBF) is located in subtropical mountain areas of middle Yunnan. Our objectives are to examine the energy allocation pattern of the two forests and test the hypothesis of Golley (1961, 1969) that caloric values of vegetation tend to increase with the altitude and latitude.

    Methods Caloric values were measured with a SDCM-Ⅲa oxygen bomb calorimeter. Energy allocation and sequestration were estimated based on biomass and biomass increment in a 1 hm2 plot in each forest.

    Important findings The caloric value of the TSRF plot was lower than that of the MEBF plot. Caloric values decreased from tree layer to shrub layer to herb layer. Leaves showed the highest caloric values of any plant part. Due to an understory plantation of Amomum villosum, which had removed almost all saplings and seedlings, the TSRF plot stored less energy than the MEBF plot, although it still maintained a high energy sequestration rate for tropical habitats with high temperature, humidity and intensive solar radiation. The tree layer stored 97% of the energy in the TSRF plot and 88% in the MEBF plot, suggesting that tree layer plays a key role in the maintenance of energy structure in the two forests. Our results support Golley's hypothesis.

    BIOMASS CARBON ACCOUNTING FACTORS OF LARIX FORESTS IN CHINA BASED ON LITERATURE DATA
    LUO Yun-Jian, ZHANG Xiao-Quan, HOU Zhen-Hong, YU Peng-Tao, ZHU Jian-Hua
    Chin J Plant Ecol. 2007, 31 (6):  1111-1118.  doi:10.17521/cjpe.2007.0139
    Abstract ( 2839 )   Full Text ( 5 )   PDF (441KB) ( 1609 )   Save
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    Aims Larix forest is important in northern China. Our objective was to understand its biomass carbon accounting factors: biomass conversion and expansion factor (BCEF), biomass expansion factor (BEF), root-shoot ratio (R) and community biomass expansion factor (CBEF).

    Methods We collected data on biomass and related parameters for natural forests and plantations from published literature, calculated carbon accounting factors, and analyzed their relationships to stand age (A), diameter at breast height (DBH) and stand density (D). Natural forests and plantations were analyzed separately.

    Important findings Mean BCEF for Larix forests was 0.683 4 t·m-3 (n=113, SD=0.355 1), and BCEF for natural stands (0.555 1 t·m-3 (n=56, SD=0.058 2)) was significantly smaller than for plantations (0.809 5 t·m-3 (n=57, SD=0.465 0)) (p<0.05). MeanBEF was 1.349 3 (n=134, SD=0.384 4), and plantations had larger mean BEF value (1.176 3 (n=63, SD=0.039 9)) than natural stands (1.502 9 (n=71, SD=0.478 0)) (p<0.05). Values ofBCEF and BEF for natural forests increased exponentially with increasing A and DBH and decreased exponentially with increasing D. Mean R was 0.245 6 (n=156, SD=0.092 6), and there was no significant difference between natural forests (0.237 6 (n=64, SD=0.061 8)) and plantations (0.251 1 (n=92, SD=0.109 0)) (p<0.05).R value of natural stands increased exponentially with increasing A and DBH, but decreased with increasing D. Moreover, R values of plantations had no significant correlations to A, DBH and D. Mean CBEF was 1.102 0 (n=51, SD=0.150 5), and the CBEF value of natural forests (1.139 8 (n=31, SD=0.177 8)) was larger than plantations (1.043 4 (n=20, SD=0.061 4)) (p<0.05). Due to significant differences between natural forests and plantations, it is better to account biomass carbon stock for natural forests and plantations separately. The relationships of these biomass factors (i.e.BCEF vs. D and BEF vs. D of plantations and CBEF of natural forests and plantations) deserve further study.

    MODELING SEASONAL VARIATION OF CO2 FLUX IN A SUBTROPICAL CONIFEROUS FOREST USING THE EALCO MODEL
    MI Na, YU Gui-Rui, WANG Pan-Xing, WEN Xue-Fa, SUN Xiao-Min, ZHANG Lei-Ming, SONG Xia, WANG Shu-Sen
    Chin J Plant Ecol. 2007, 31 (6):  1119-1131.  doi:10.17521/cjpe.2007.0140
    Abstract ( 2533 )   Full Text ( 3 )   PDF (940KB) ( 1607 )   Save
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    Aims Seasonal drought frequently occurs in the mid-subtropical region of China and commonly combines with high temperature. Our objectives were to test the sensitivity of carbon exchange to this seasonal drought and discuss the influence of seasonal drought on carbon assimilation.

    Methods We used flux measurements obtained from eddy covariance technology since October 2002 over a human-planted forest ecosystem at Qianyanzhou (QYZ) (26°44' N, 115°03' E, 110.8 m als.). The EALCO (ecological assimilation of land and climate observations) model is parameterized to simulate the ecosystem carbon exchange process in the human-planted evergreen forest. Simulation results were validated using half-hourly carbon fluxes and daily and annualGPP (gross primary production), NEP (net ecosystem production) and TER (total ecosystem respiration) estimated from eddy covariance measurements.

    Important findings In general, the model can effectively simulate the two years' carbon fluxes among soil-plant-atmosphere on hourly, daily and annual scales. Both simulations and observations showed strong impact of drought on GPP in 2003. Compared with 2004, the annual GPP in 2003 was 12.9% lower according to observations (1 610 vs. 1 865 g C·m-2) and 11.2% lower according to model results (1 637 vs. 1 844 g C·m-2). The diurnal variations of NEP from both observations and simulations during the period of soil water deficit showed asymmetric format, i.e., the peak value of carbon exchange accrued at a certain time in the morning and then decreased with time. Modeling results indicated that water stress has more influence on photosynthesis than TER, which led to the decrease of NEP. Further analysis suggested that deep soil water content controls canopy photosynthesis in sunny days before noon during soil water stress. Afternoon, both high temperature and deep soil water content eliminate the GPP, and their elimination percents are equal. On cloudy days, radiation and deep soil water content primarily determine the photosynthesis, and temperature becomes a generally minor controlling factor.

    LATENT AND SENSIBLE HEAT FLUXES AND ENERGY BALANCE IN A MAIZE AGROECOSYSTEM
    LI Yi-Jun, XU Zhen-Zhu, WANG Yun-Long, ZHOU Li, ZHOU Guang-Sheng
    Chin J Plant Ecol. 2007, 31 (6):  1132-1144.  doi:10.17521/cjpe.2007.0141
    Abstract ( 3097 )   Full Text ( 9 )   PDF (859KB) ( 1844 )   Save
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    Aims Agroecosystems are influenced strongly by human activity and climate change. In order to scientifically manage agroecosystems under climate change, it is important to understand water exchange and energy transfer between agroecosystems and the atmosphere. We analyze latent and sensible heat fluxes of a maize agroecosystem as a case study.

    Methods Latent and sensible heat fluxes were measured in a maize agroecosystem using a 3.5 m eddy covariance tower from June 2004 to December 2005 at the Jinzhou maize agricultural ecosystem field observation station (Liaoning Province, China). Meteorological factors were recorded using sensors at 2.3 and 4.1 m using a micrometeorological tower.

    Important findings Diurnal and annual variations of latent heat fluxes and sensible heat fluxes had the same characteristics as net radiation and could be expressed as hyperbola curves. Their peak values appeared at 12∶00-13∶00. The maximum latent heat flux was about 655 w·m-2 (at 13∶00 July 8,2004), and the maximum sensible heat flux was 369 w·m-2 (at 13∶00 May 31,2004). The intensities of latent heat fluxes and sensible heat fluxes had close relationships with environmental factors. Latent heat flux was negatively correlated with atmospheric pressure, and sensible heat flux was positively correlated with air temperature. Fluxes of latent and sensible heat were very sensitive to precipitation. Latent heat flux was greatly affected by the intensity and timing of precipitation, regardless of seasonal and daily changes. Energy of the maize agroecosystem was unbalanced with the loss of about 15.5%, possibly because of lack of knowledge of 0-5 cm soil heat reserve and canopy heat reserve. The energy balance had obvious differences between cloudy and rainy days, with the loss of energy much less on rainy than cloudy days, especially with a surplus of energy on rainy days in August.

    DENSITY IN ARTEMISIA ORDOSICA SUCCESSIONAL COMMUNITY IN RESPONSE TO SPATIAL HETEROGENEITY OF SOIL MOISTURE AND ORGANIC MATTER
    WANG Hai-Tao, HE Xing-Dong, GAO Yu-Bao, LU Jian-Guo, XUE Ping-Ping, MA Di
    Chin J Plant Ecol. 2007, 31 (6):  1145-1153.  doi:10.17521/cjpe.2007.0142
    Abstract ( 2814 )   Full Text ( 4 )   PDF (594KB) ( 1569 )   Save
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    Aims Using environmental spatial heterogeneity to explain the heterogeneity of vegetation is an important issue in ecology. We approached relationships between the spatial heterogeneity of soil moisture, organic matter and densities of Artemisia ordosica and A. frigida in a successional community of A. ordosica. Our objective was to discuss stability mechanisms of the plant community based on changes in spatial heterogeneity.

    Methods The study area is located at Tengri Desert (arid zone), which belongs to Alashan League of Inner Mongolia. Our sample plot was 80 m× 80 m, which contained 400 quadrats (4 m×4 m). In every quadrat, we determined soil moisture at 40 cm depth (oven-drying method) and soil organic matter at 0-5 cm top soil (potassium dichromate volumetric method), and recorded density ofA. ordosica and A. frigida. We analyzed densities in response to the spatial heterogeneity of soil moisture and organic matter using statistics and geostatistics.

    Important findings The spatial heterogeneities of densities of A. ordosica and A. frigida were related to soil moisture and organic matter at the plot-scale (80 m×80 m). There were a significant positive linear correlation between the heterogeneities of the density ofA. frigida and moisture and a significant positive power cortelation between heterogeneties of the density of A. ordosica and soil organic matter. We suggest that A. ordosica enriched the content of organic matter, thus promoting establishment of A. frigida. Both A. frigida and A. ordosica had clumped distributions, which enhanced soil spatial heterogeneity. Findings indicate a competitive displacement relationship between the two species. Thus, changes of soil spatial heterogeneity are factors in A. ordosica community succession in semi-desert zone.

    PROPERTIES OF COMMUNITY STRUCTURAL COMPLEXITY DESCRIBED BY MEAN LENGTH OF HUFFMAN CODE
    JIN Sen
    Chin J Plant Ecol. 2007, 31 (6):  1154-1160.  doi:10.17521/cjpe.2007.0143
    Abstract ( 2638 )   Full Text ( 0 )   PDF (395KB) ( 1285 )   Save
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    Aims Anand & Orlóci ( 1996) proposed a method measuring the total, disordered and organized complexity of community structure using the mean length of Huffman code, the 12th order of Rényi entropy, and the difference between these two measures, respectively. This method is quite different from measures based on community biodiversity and is potentially of great significance. Although some properties of the measures were discussed by Anand & Orlóci (1996), a thorough study has not been conducted, especially on their ecological meaning. The purpose of the paper is to reveal: 1) factors affecting the measures and their ecological meaning, 2) relationship between complexity and biodiversity, and 3) effect of species number on structural complexity.

    Methods First, >4 000 000 simulated communities with different structures were constructed by two methods: evenly distributed mode and dominated mode. Then the three complexity measures were computed. Correlation analyses were conducted between these measures and potentially related factors such as Shannon-Wiener index, coefficient of variation and logarithmic proportion of most dominated species. Multiple linear regressions between the complexity measures and combination of these factors were carried out to explore the relationship between complexity and biodiversity. Communities with different species number were then constructed and tested to explore the effect of species number on complexity measures.

    Important findings The three complexity measures are strongly correlated with the Shannon-Wiener index, coefficient of variation and logarithmic proportion of the most dominated species. For total complexity, the correlation coefficient between it and the Shannon-Wiener index is nearly 1 (0.996), so is that between the 12th order of Rényi entropy and logarithmic proportion of the most dominated species. The determining coefficient of multiple linear regression between organized complexity and Shannon-Wiener index and logarithmic proportion of the most dominated species is also near 1 (0.97). These findings suggest that all three measures of community structural complexity are affected by the Shannon-Wiener index, coefficient of variation and logarithmic proportion of the most dominated species. For organized structural complexity, it can be expressed as a linear combination of Shannon-Wiener index and logarithmic proportion of the most dominated species. Biodiversity can explain 41~46% of variation of organized structural complexity. Although the three complexity measures increase with number of species, they do not increase as much as described by Anand & Orlóci (1996), and it does not affect the relationship between the complexity measures and related factors.

    ROOT DYNAMICS OF THREE GRASSES IN HORQIN SANDY LAND OF CHINA
    HUANG Gang, ZHAO Xue-Yong, SU Yan-Gui
    Chin J Plant Ecol. 2007, 31 (6):  1161-1167.  doi:10.17521/cjpe.2007.0144
    Abstract ( 3533 )   Full Text ( 4 )   PDF (307KB) ( 1680 )   Save
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    Aims We selected three representative grasses in Horqin Sandy Land and measured their root dynamic by minirhizotrons, a nondestructive, in situ method for directly viewing and studying root dynamics.

    Methods The experiment was conducted on three quarters (2 m×2 m) of Naiman Desertification Research Station, Chinese Academy of Sciences during the 2005 growing season. The sandy soil was transported from a sandy dune and sifted through a 0.5 mm sieve. On May 15, seeds ofSetaria viridis, Artemisia scoparia and Agriophyllum squarrosum were cultivated in each quarter, respectively. Three minirhizotrons (50 cm long and 7 cm outer diameter) per treatment were installed at right angles. A black cover blocked light from entering the section of the transparent tube left above ground. For each treatment, three tubes were installed in the center parallel to the plant row, 10 cm from the row. Each quarter was supplied with enough water until June 5, and thereafter precipitation was the only water source. According to plant needs, seedlings of three grasses were kept 15 cm apart in rows and 20 cm apart between rows. The number of roots on the minirhizotron wall was obtained using a mirror, and root length was estimated counting the number of intersections of roots with a 1 cm-mesh grid, using the modified Newman-Line-Intersect method.

    Important findings The curves of total root number of S. viridis and Artemisia scoparia after seed germination fitted a cubic regression model, while that of Agriophyllum squarrosum showed exponential increase. The production of S. viridis and Artemisia scoparia peaked by the end of July or the beginning of August and then decreased, while Agriophyllum squarrosum showed an opposite trend. Roots of S. viridis were concentrated within the top 30 cm of the soil profile where the maximum root length intensity achieved 2.23 cm·cm-2. Vertical root distribution of S. scoparia had an almost symmetrical pattern. At the prophase of growth period, it preferentially developed superficial roots, while at the end of the growth period, roots occurred dominantly in deep soil. In contrast, Agriophyllum squarrosum showed an opposite growth process. S. viridis had the highest root length intensity during the prophase and early in the growth period, but root length intensity of Agriophyllum squarrosum was higher than S. viridis at the end of the growth period.

    CONTENTS AND ISOTOPIC COMPOSITION OF C AND N IN MOSS (HAPLOCLADIUM MICROPHYLLUM) TISSUES AND SOIL RHIZOSPHERE
    LIU Xue-Yan, XIAO Hua-Yun, LIU Cong-Qiang, LI You-Yi
    Chin J Plant Ecol. 2007, 31 (6):  1168-1173.  doi:10.17521/cjpe.2007.0145
    Abstract ( 2947 )   Full Text ( 2 )   PDF (272KB) ( 1779 )   Save
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    Aims We investigated the new and senescent tissues of moss and the soil rhizosphere to determine 1) the elemental and isotopic composition characteristics during senescence and 2) the final contribution to soil.

    Methods C and N contents and isotopic composition (δ13C and δ15N) of Haplocladium microphyllum and its soil rhizosphere were analyzed at Guiyang, China.

    Important findings The C and N contents were higher in new growing tissues than in senescent tissues, and there were significant correlations between the two types of tissues, indicating physiological malfunction (e.g., loss of photosynthesis) and internal element redistribution during moss senescence. No significant difference was found between new and senescent tissues in isotopic composition, but their δ13C values or δ15N values were correlated, suggesting special isotopic regulation in the simple and nonvascular structure of mosses. In contrast, there was no C or N correlation between the moss tissues and soil. This was attributed to long-term nutrient retention and slow deposition to form soil, indicating the moss layer in this area has a small contribution to soil carbon and nitrogen.

    ECOLOGICAL AND BIOLOGICAL DIFFERENCES BETWEEN SPRING AND AUTUMN PLANTS OF TWO DESERT EPHEMERALS
    ZHANG Tao, SUN Yu, TIAN Chang-Yan, FENG Gu
    Chin J Plant Ecol. 2007, 31 (6):  1174-1180.  doi:10.17521/cjpe.2007.0146
    Abstract ( 2881 )   Full Text ( 1 )   PDF (337KB) ( 1378 )   Save
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    Aims Ephemerals are important in desert ecosystems, playing a key role in ecosystem stabilization. Previous research has concentrated on spring ephemerals. Little is known about biological and ecological characteristics of ephemerals that germinate in spring and autumn and about the significance of autumn ephemerals in stabilizing desert ecosystems.

    Methods We marked plants of Plantago minuta and Erodium oxyrrhynchum, species that germinate in spring and autumn. We investigated their crowns, leaves and phenological characteristics in the field during their growing seasons and measured their dry weights and mean arbuscular mycorrhizal colonization rates in the laboratory.

    Important findings Leaves, flowers, fruits, seeds and dry weights of autumn plants are larger than those of spring plants. For example, in autumn P. minuta and E. oxyrrhynchum produced 13.0 and 4.4 times as many seeds and flowered 14 and 7 days earlier, respectively, than spring plants. In addition, mean arbuscular mycorrhizal colonization rates were higher in autumn than spring plants, accelerating the absorption of phosphorus. Autumn plants had greater capability of reproduction and ecosystem stabilization, allowing them to play an important role in stabilizing the desert ecosystem.

    CHANGES OF CHARACTERISTICS OF THE LEAF EPIDERMIS AND GENETIC DIVERSITY OF CARAGANA DAVAZAMCII IN DIFFERENT HABITATS IN ERDOS PLATEAU, CHINA
    YANG Ming-Bo, YANG Jie, YANG Jiu-Yan, LIANG Na, QING Hua
    Chin J Plant Ecol. 2007, 31 (6):  1181-1189.  doi:10.17521/cjpe.2007.0147
    Abstract ( 2701 )   Full Text ( 6 )   PDF (457KB) ( 1159 )   Save
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    Aims Although Caragana davazamcii is an important nitrogen-fixing plant in North China, few studies have focused on its epidermal structure and genetic diversity along a precipitation gradient. Our aims are to determine how changes of epidermal structure of C. davazamcii leaves are related to changes of genetic diversity in different habitats, what role environments play in this relationship, and whether these populations have potential to become adapted to their local environments in different ways.

    Methods We established 20 m×20 m plots along the precipitation gradient and randomly collected leaves ofC. davazamcii from natural populations. We studied leaf epidermal structure using a light microscope (LM) and a scanning electron microscope (SEM) and used ISSR-PCR genetic diversity analysis to study differentiation among populations.

    Important findings The leaf epidermis of C. davazamcii in different habitats was significantly different as a result of environmental effects. Trichome density, stomatal density, stomatal index and cuticle coarseness increased with changes in average annual rainfall from east to west, as did genetic diversity of populations. Caragana davazamcii showed significant phenotypic plasticity in different habitats, and this may play a critical role in the ecological adaptability of C. davazamcii populations.

    GENETIC DIVERSITY OF TILIA AMURENSIS POPULATIONS IN DIFFERENT GEOGRAPHICAL DISTRIBUTION REGIONS
    MU Li-Qiang, LIU Ying-Nan
    Chin J Plant Ecol. 2007, 31 (6):  1190-1198.  doi:10.17521/cjpe.2007.0148
    Abstract ( 2642 )   Full Text ( 1 )   PDF (366KB) ( 1910 )   Save
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    Aims Tilia amurensis is one of the II-grade Chinese protected plants with an important economic value and ecological significance. The population of T. amurensis has gradually declined due to overdrafting. Our objectives were to 1) study the genetic diversity of six natural populations varying in longitude and latitude and six varying in altitude and 2) discuss strategies to conserve germplasm resources.

    Methods The newly developed inter-simple sequence repeats (ISSR) marker was used to examine genetic diversity.

    Important findings The results of 14 ISSR primers showed that polymeric percentage of the six populations was 93.85%, the gene diversity (H) was 0.243 3 and Shannon Index of diversity (I) was 0.380 3. The genetic diversities of T. amurensis decreased with increasing altitude, had a single-peak curve with increasing latitude, and were higher in the central region than in the edges. Analysis of molecular variance (AMOVA) revealed that the majority of genetic variation occurred within populations. Genetic distance and geographic distance were uncorrelated. We concluded that the genetic diversity of T. amurensis was high and mainly within populations. Also, the major factors threatening the development of T. amurensis included direct damage to natural populations due to destruction of habitat and poor regeneration ability caused by innate biological and ecological characteristics. Habitat should be protected, as individuals, especially in core areas.

    POLLEN VIABILITY AND VARIATION IN CATHAYA ARGYROPHYLLA
    WANG Hong-Wei, DENG Hui-Sheng, TAN Hai-Ming, QIN Kun, ZHANG Ding-Heng, GE Song
    Chin J Plant Ecol. 2007, 31 (6):  1199-1204.  doi:10.17521/cjpe.2007.0149
    Abstract ( 2663 )   Full Text ( 3 )   PDF (264KB) ( 1124 )   Save
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    Aims Cathaya argyrophylla is one of the most endangered conifers endemic to China. Previous studies showed that this species was characterized by unusually low fertility and high embryonic mortality, which may be factors leading to its endangerment. Because knowledge of pollen viability is important for successful reproduction of plant species, we investigated pollen viability in natural populations of C. argyrophylla.

    Methods We collected pollen samples from 16 individuals of seven populations in two locations, Dayaoshan (DYS) in Sichuan and Huaping (HP) in Guangxi. We evaluated pollen viability using the TTC method and analyzed its variation based on ANOVA.

    Important findings Pollen viability of C. argyrophylla is comparable to other gymnosperms. Viability was stable in dry and low temperature conditions, and the optional sucrose concentration for pollen germination was about 13%. We found low variation of pollen viability among individuals within populations (p>0.05) but significant differentiation between populations within regions and among regions (p<0.05). The pollen viability ofC. argyrophylla is normal and thus not likely relevant to its endangerment. We proposed artificial crossings between genetically distinct populations as a potential conservation strategy for the population recovery of this endangered species.

    REVIEW OF PLANT RESPONSES TO OZONE POLLUTION
    XU Hong, YANG Jing-Cheng, CHEN Sheng-Bin, JIANG Gao-Ming, LI Yong-Geng
    Chin J Plant Ecol. 2007, 31 (6):  1205-1213.  doi:10.17521/cjpe.2007.0150
    Abstract ( 2613 )   Full Text ( 6 )   PDF (376KB) ( 1907 )   Save
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    Ozone (O3) is highly beneficial in many ways, such as filtering ultraviolet radiation in the upper atmosphere, but O3 at ground level is a serious pollutant. High O3 concentration causes the damage to plants ranging from minimal visible symptoms to substantial inhibition of productivity, and species- or cultivar-specific responses exist. Interactions between plants and herbivorous insect pests or plant pathogens may be affected by O3. Decreased carbon flow above- and below-ground in high O3 environment could significantly decrease biodiversity. Therefore, O3 will affect terrestrial ecosystems substantially. The following aspects are suggested to be further studied in China: 1) the comparison and selection of plant species or cultivars with high O3 resistance, 2) the possible methods which can alleviate O3 damage to plants, 3) O3 effects on the natural ecosystems in China, and 4) the positive function of vegetation in decreasing O3 pollution.


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