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Table of Content
    Volume 32 Issue 3
    30 May 2008
    Original article
    YU Li, CAO Ming-Kui, TAO Bo, LI Ke-Rang, DONG Wen-Jie, LIU Hong-Bin, LIU Chang-You
    Chin J Plant Ecol. 2008, 32 (3):  521-530.  doi:10.3773/j.issn.1005-264x.2008.03.001
    Abstract ( 3280 )   Full Text ( 8 )   PDF (400KB) ( 1404 )   Save
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    Aims Assessment of the sensitivity and vulnerability of terrestrial ecosystem to climate change is one of the most important aspects of global change research. Our objective was to develop a new approach to assessing the vulnerability of terrestrial ecosystem using a process-based ecosystem model.

    Methods We developed a new quantitative approach to assess vulnerability of terrestrial ecosystems based on an ecosystem process model with two aspects: vegetation changes and ecosystem function changes. In accordance with the definition of vulnerability used by the Intergovernmental Panel on Climate Change (IPCC), we used change times and changing direction of vegetation as key indicators of sensitivity and adaptation of vegetation responses to climate change. We also used the function's annual variability and its trend as indicators of sensitivity and adaptation of ecosystem functions response to climate change, respectively. Based on these indicators, the integrated vulnerability was determined, including assessment under the contemporary climate condition and future climate change scenarios.

    Important findings The more vulnerable ecosystems were found in the north and west areas of China, with less vulnerable ecosystems mostly in the south and east. The vulnerability of ecosystems would increase with climate change, but the pattern of vulnerability would be little changed by the end of this century, depending on the scenarios. The percentage of non-vulnerable ecosystems would be reduced by about 22%, and the highly and exceedingly vulnerable ecosystems would be reduced by about 1.3% and 0.4%, respectively. Most highly vulnerable ecosystems are distributed in northwestern China, Inner Mongolia, south of the Tibet Plateau and some areas of northern and northeastern China, both under contemporary climate condition and the future climate change scenarios, and they were mainly scattered in transition eco-zones and grassland-desert ecosystems in northwestern China. When investigated regionally, the vulnerability would increase in southern, central, northwestern and southwestern China, but vulnerability would decrease in northern and northeastern China and Inner Mongolia of China.

    DONG Ming-Wei, YU Mei
    Chin J Plant Ecol. 2008, 32 (3):  531-543.  doi:10.3773/j.issn.1005-264x.2008.03.002
    Abstract ( 2854 )   Full Text ( 3 )   PDF (593KB) ( 1830 )   Save
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    Aims Water availability influences community composition and function in semi-arid areas. Habitat water availability may differentiate functional traits on water and carbon assimilation use efficiencies of dominant species, which may induce different response patterns of communities to climatic change. Our objectives are to 1) quantitatively analyze long-term net primary productivity (NPP) dynamics of typical grassland communities along a water gradient based on field measurements, long-time monitoring results and a process-based model; 2) analyze trends of temperature and precipitation based on local long-term meteorological data and predict future climate change scenarios and 3) predict NPP responses of the communities along the water gradient to climate change and interpret the results by means of water stress index (WSI) and carbon stress index (CSI).

    Methods We selected four grassland communities along a water gradient in the Xilingol River Basin of China as our study sites: Stipa baicalensis, Leymus chinensis, Stipa grandis, and Stipa krylovii. We conducted field surveys and measurements of physiological parameters and soil parameters in summer 2005 and used local meteorological data (1953 to 2005) to analyze trends of precipitation and temperature and prescribe future scenarios. A process-based model, BIOME-BGC, was parameterized and validated using field data and long-term monitoring data and run on daily steps to simulate NPP dynamics of the four communities under the current climate and future scenarios. We calculated water and carbon stress indices for each community under each scenario to interpret possible mechanisms.

    Important findings Minimum and maximum temperatures increased from 1953 to 2005, while the precipitation varied. Average NPP of the four communities decreased 14.2% under the scenario of increasing temperature, increased 13.2% under the scenario of increasing precipitation, and declined 2.7% under the scenario of increasing both. Precipitation is the predominant factor on NPP dynamics in this semi-arid area, while temperature mainly influences plant respiration and evapotranspiration and also affects NPP. Due to the differences in water availability and functional traits of dominant species, the four communities presented different responses and sensitivities to the climate changes in precipitation and temperature, which closely related to variations in WSI and CSI. Stipa krylovii community maintains a high WSI and temperature, reflected by variations in WSI and CSI, shows great dependence on precipitation mainly because of the poor habitat water availability. Stipa baicalensis community has higher NPP under both current and future climate change scenarios largely because it has 1) lower WSI because of better habitat water availability and 2) lower CSI because its higher carbon to nitrogen ratio contributes to less photosynthetic products consumed by maintenance respiration.

    ZHAO Liang, GU Song, ZHOU Hua-Kun, XU Shi-Xiao, ZHAO Xin-Quan, LI Ying-Nian
    Chin J Plant Ecol. 2008, 32 (3):  544-554.  doi:10.3773/j.issn.1005-264x.2008.03.003
    Abstract ( 2660 )   Full Text ( 10 )   PDF (641KB) ( 1239 )   Save
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    Aims It is important to the study of the carbon cycle and ecological issues to understand seasonal variation in CO2 flux and the influence of environmental factors on the artificial grassland in the source region of the three rivers on the Qinghai-Tibetan Plateau.

    Methods We utilized the eddy covariance method to observe net ecosystem CO2 exchange (NEE) and biological and environmental factors and their variation at the Elymus nutans artificial grassland from September 1, 2005 to August 31, 2006.

    Important findings The daily maximum uptake of CO2 was 2.38 g C·m-2·d-1 on July 30. The ratio of daily uptake and emission in August were observed, -6.82 and 2.95 μmol CO 2·m-2·s-1, respectively. In the growing seasons, daily NEE was dominated by the variation of photosynthetically active radiation (PAR). At the same time, daily NEE combined with leaf area and community diversity to control photosynthetic rate and photosynthetic efficiency. Maximum photosynthetic rate was 2.46-10.39 μmol CO 2·m-2·s-1, and the apparent quantum yield (denoting the maximum efficiency of light utilization in photosynthesis) was 0.013-0.070 μmol CO 2·μmol-1 PAR. The influence of temperature, Q10 (1.8) in the growing season was less than in the non-growing season. The respiration of the ecosystem was mainly dominated by temperature and leaf area. Carbon absorption was not dominated by the larger temperature difference of the day and night in the growing season. Our study proved that the artificial grassland ecosystem was a carbon sink with a carbon absorption of -49.35 g C·m-2·a-1. Our study also proved that the source and sink function of carbon was influenced by the amount, intensity and seasonal allocation of annual precipitation, as well as by plant community diversity.

    TAN Zheng-Hong, ZHANG Yi-Ping, YU Gui-Rui, SONG Qing-Hai, GAO Ju-Ming, YANG Zhen, SUN Xiao-Min, ZHAO Shuang-Ju
    Chin J Plant Ecol. 2008, 32 (3):  555-567.  doi:10.3773/j.issn.1005-264x.2008.03.004
    Abstract ( 2988 )   Full Text ( 3 )   PDF (611KB) ( 1645 )   Save
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    Aims Because of its highly diverse flora and unique climate, Xishuangbanna tropical seasonal rain forest (XTSRF) is one of few areas in China characterized by well-protected primary forest types considered to be tropical rainforest. Compared with other rainforests around the world, XTSRF occurs at higher latitude and altitude. Our aim was to investigate variation of CO2 concentration at different time scales under this unique climate and special geographical situation and determine how environmental variables formed the temporal pattern of CO2 concentration.

    Methods CO2 concentration in XTSRF was measured continuously by infrared gas analyzers (Li-7500, Li-Cor, Lincoln, NE, USA) and recorded every 30 min with a data-logger (CR5000); meteorological variables were also measured and recorded. The static chamber method was used to measure soil respiration weekly. Leaf area index was measured in the middle of every month using a forest canopy analyzer (LAI-2000).

    Important findings The diurnal pattern of CO2 concentration above canopy (AC) was consistent through the year, with higher values at daytime and lower values at night due to photosynthesis uptake and respiration release, respectively. In contrast, near the forest floor (NF) diurnal patterns were bimodal in most months, with a second peak in late afternoon. Average variation of CO2 concentration in a year was larger at AC (622.8-686.5 mg·m-3) than at NF (659-700 mg·m-3). Difference of CO2 concentration between AC and NF was higher in the rainy season than in the dry season, with the largest value (-62.9 mg·m-3) in October and the smallest (-8.4 mg·m-3) in December. The “flushing" phenomenon in the early morning was primarily affected by stability of the atmospheric boundary layer. In long foggy days and under low wind velocities, forests in the valley had little air circulation, but local circulation resulted in sharp increases of CO 2 concentration in the afternoon. CO2 concentration of NF and AC were dominated by soil respiration and canopy metabolism, respectively.

    FENG Yun, MA Ke-Ming, ZHANG Yu-Xin, QI Jian
    Chin J Plant Ecol. 2008, 32 (3):  568-573.  doi:10.3773/j.issn.1005-264x.2008.03.005
    Abstract ( 3129 )   Full Text ( 4 )   PDF (308KB) ( 1727 )   Save
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    Aims Our objective was to study the relationship between plant species and environmental factors for different strata of a Quercus liaotungensis forest along an altitudinal gradient in Dongling Mountain, Beijing, China.

    Methods We collected 119 vegetation samples separately in the tree, shrub and herb layers along an altitudinal gradient and recorded environmental factors such as altitude and slope inclination and position. We used detrended canonical correspondence analysis (DCCA; CANOCO 4.5) to determine the main environmental factors related to the distribution of plant communities.

    Important findings The DCCA axis 1 reflected the gradient in altitude, while axis 2 reflected slope position. Most species occurred at lower altitude. Species in the tree layer were distributed uniformly. A big overlap in the composition of the herb layer indicated that the microenvironment for species was similar. Species diversity increased from high to low altitude. According to the correlations among environment factors and results of the DCCA ordination, the most important factor affecting species distribution in this region was altitude.

    ZHU Yuan, KANG Mu-Yi, JIANG Yuan, LIU Quan-Ru
    Chin J Plant Ecol. 2008, 32 (3):  574-581.  doi:10.3773/j.issn.1005-264x.2008.03.006
    Abstract ( 3097 )   Full Text ( 6 )   PDF (309KB) ( 1663 )   Save
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    Aims Our objective was to reveal the altitudinal pattern of species diversity in woody plant communities of Mountain Helan, which is located on the ecotone between temperate steppe and desert regions in arid northwestern China.

    Methods We surveyed forests and shrublands with the quadrat method and used Generalized additive model (GAM) to model relationships between species richness of tree, shrub and herbaceous layers with altitude.

    Important findings Altitude accounted for 30%-40% of the variances of species richness patterns, including tree, shrub, herb and total species richness. Both for forest and shrubland communities, 60%-80% of the species were herbaceous and patterns of total species richness with altitude were almost determined by herbaceous species. In forest communities, species richness of the tree layer peaked at middle altitude, because of favorable precipitation and temperature. Species richness of shrub and herbaceous layers in forest communities decreased with altitude, showing a significant influence of forest canopy cover. For shrub communities, species richness of shrub and herb layers also peaked at middle altitude. Aridity at low altitude and cold at high altitude limited species' survival, and only at middle elevations could coexist large numbers of plant species.

    ZHANG Liang, XING Fu, YU Li-Li, XU Kun, SUN Zhong-Lin, LÁ Xian-Guo
    Chin J Plant Ecol. 2008, 32 (3):  582-590.  doi:10.3773/j.issn.1005-264x.2008.03.007
    Abstract ( 2850 )   Full Text ( 4 )   PDF (390KB) ( 1293 )   Save
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    Aims Island forest is a major vegetation type of the Sanjiang Plain in northeastern China. However, its species diversity is at risk of decline. Our objectives were to 1) describe the flora, 2) determine the level of plant diversity, and 3) determine relationships between diversity indices and patch characteristics (area, perimeter and shape index).

    Methods We used Quick Bird satellite image data to identify a 65 km2 study site. The quadrat method was used to investigate community patch characteristics such as area, perimeter and shape index, which were analyzed with Erdas Imagine 8.7. Four indices were selected to describe plant diversity: richness (R), Simpson (D), Shannon-Wiener (H'), and Pielou (Jsw).

    Important findings The 19 patches of the island forest had 140 species of vascular plants of 44 families and 102 genera dominated by cosmopolitan and temperate genera. Our data suggested that, compared with the neighboring community in the Honghe Nature Reserve, some plant species had disappeared. The diversity indices were significantly different among shrub layers of the Populus davidiana, Betula platyphylla and P. davidiana + B. platyphylla communities (p<0.05). Additionally,R, D and H' indices of different layers were as follows: herb layer > shrub layer > tree layer, with significant differences among them ( p<0.01). While statistically significant correlations were observed between theR index and patch area (r=0.591, p<0.01), perimeter (r=0.674, p<0.01) and shape index (r=0.584, p<0.01), no correlations were noted for theD, H' and Jsw indices. Diversity levels remained relatively high after human disturbance. The greatest difference among patches was noted in herb layers. Our data also suggested that gap disturbance was an important cause of higher understory diversity. Plant species richness increased with patch area, perimeter and shape index, most likely resulting from edge effects. Our results demonstrated that the island forest plays an important role in preserving plant diversity in the region.

    ZHAO Na, LI Yuan-Heng, WANG Zheng-Wen, LIU Rong-Tang
    Chin J Plant Ecol. 2008, 32 (3):  591-600.  doi:10.3773/j.issn.1005-264x.2008.03.008
    Abstract ( 2675 )   Full Text ( 5 )   PDF (478KB) ( 1051 )   Save
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    Aims Seedlings are central to population maintenance, community structure and succession, but the dynamics of seedling recruitment at the community level and responses of seedling dynamics to different disturbances in typical steppe are unclear. Our aims are to uncover the effects of mowing and/or grazing on the seasonal dynamics of seedling emergence, survival and mortality in three common grass species (Agropyron cristatum, Stipa krylovii and Cleistogenes squarrosa) in typical steppe communities, and to determine how dynamics are affected by temporal variation in air temperature and precipitation.

    Methods Four treatments were used in five 10 m × 20 m replicate blocks: control, mowing to 15 cm height, mowing to 5 cm height, and grazing (also annually mown by farmers). Seedlings were censused from May 20 to September 28. Plant species composition of each block was surveyed with conventional methods and dominance values were calculated for the three grass species. Differences in seedling density, mortality and emergence among treatments were tested using repeated measures define factor ANOVA in the SPSS package, but the mortality and emergence data were extracted and then arcsine-transformed before ANOVA analysis. One-Way ANOVA was adopted to compare the overall coverage of the community and the dominance of the three grass species among different treatments.

    Important findings Seedling densities of all three species increased from late May to mid-August. Mowing suppressed seedling emergence of tall-growing S. krylovii possibly by affecting seed availability due to removal of reproductive parts in the previous year. Mowing had a positive effect on low-growing C. squarrosa probably as a result of increased light availability and less competitive pressure from adult individuals as mowing lowered plant heights and densities. Relatively high seedling mortality during early and late growing season was thought to be associated with aridity and/or low air temperature, and a small peak from mid-June to early July probably was attributed to drought due to previous rainfall shortage. Seedling emergence in all species took place fairly synchronously from May to July, probably due to the relatively optimum environmental conditions in air temperature and water supply. More detailed and complex studies relating seedling recruitment to such processes as seed germination, seed dormancy and seed availability are required, especially under mowing and grazing practices, to uncover the roles of seed reproduction in community processes.

    TIAN Jia-Qian, ZHOU Zhi-Yong, BAO Bin, SUN Jian-Xin
    Chin J Plant Ecol. 2008, 32 (3):  601-610.  doi:10.3773/j.issn.1005-264x.2008.03.009
    Abstract ( 3259 )   Full Text ( 8 )   PDF (404KB) ( 1305 )   Save
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    Aims In this study, variations of soil particle size distribution and correlations with soil C and N were studied on sites representing six different land-use types in the steppe grasslands of Inner Mongolia, Northern China. The six land-use types are grazing exclusion by fencing (GE), mowing (MW), free grazing (FG), fallow (FL), alfalfa pasture (AP), and corn plantation (CP). Our objectives were to: (a) assess variability of soil particle size distribution across different land-use types in the steppe grasslands of northern China and (b) examine correlations of soil particle size distribution with soil C and N as affected by land-uses.

    Methods Twenty-four sampling plots, each 30 m×30 m, were established on sites representing the six land-use types. Measurements were made on soil particle size distribution, aboveground biomass, root biomass, litter, soil organic carbon (SOC) and soil total nitrogen (TN) in the 0-10, 10-20 and 20-30 cm soil layers. Data were evaluated by one-way analysis of variance and correlation analysis using SPSS. Fractal dimension of soil particle size distribution was calculated using the method of Yang et al. (1993).

    Important findings Fractal dimension of soil particle size distribution was lowest in the FG among the six land-use types. Soil clay (<0.005 mm) and silt (0.005-0.05 mm) content of the FL and AP were consistently higher than the other four land-use types; whereas those of the FG were consistently lower. Clay and silt content decreased with soil depth except for the AP and FG. Soil sand content was significantly negatively correlated withSOC and TN for all land-use types, while soil clay content was significantly positively correlated with SOC and TN except for FG and AP. Regardless of the land-use types, root biomass was found to be significantly positively correlated with SOC, TN and soil clay and silt content. Aboveground biomass and litter were significantly positively correlated with only clay content. Root biomass and clay content together explained 70% of the variance in SOC and soil TN, and separately only 20% of the variance each. The relationships were best described as: SOC = 1.08 × clay% + 0.01 × biomass roots-19.45,TN=0.079×clay%+0.001×biomassroots-1.143. Findings indicate that land-use types can have significant effects on soil physical properties as well as SOC and soil TN and consequently alter the relationships of soil particle size distribution with SOC and soil TN.

    WAN Hong-Wei, YANG Yang, BAI Shi-Qin, XU Yun-Hu, BAI Yong-Fei
    Chin J Plant Ecol. 2008, 32 (3):  611-621.  doi:10.3773/j.issn.1005-264x.2008.03.010
    Abstract ( 3340 )   Full Text ( 19 )   PDF (473KB) ( 1506 )   Save
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    Aims We conducted a field manipulation experiment to examine the underpinning mechanisms of variation in plant leaf functional traits along a nitrogen addition gradient in a mature typical steppe ecosystem in Inner Mongolia.

    Methods We selected six dominant and sub-dominant plant species for study: Leymus chinensis, Achnatherum sibiricum, Agropyron cristatum, Stipa grandis, Cleistogenes squarrosa and Carex korshinskyi. Together, they account for >90% of the total community aboveground biomass. We examined the effects of N addition on specific leaf area ( SLA), leaf N content, total chlorophyll content, and chlorophyll a/b ratio.

    Important findings Nitrogen addition lessened the N limitation while strengthening light competition among co-existing plant species. Plant species differed significantly in their responses to increased N addition rates. Leymus chinensis showed high plasticity in SLA, leaf N, and total chlorophyll content. Its area-based leaf N content increased linearly with N addition rate. Achnatherum sibiricum showed the highest plasticity in SLA and high mass-based leaf N and chlorophyll content to N enrichment, whereas its area-based leaf N content was relative stable. Compared to L. chinensis and A. sibiricum, A. cristatum had low plasticity in the three leaf functional traits investigated. Both S. grandis and C. korshinskyi illustrated low plasticity in SLA along with low SLA of S. grandis and short stature of C. korshinskyi, leading to reduced light competitive ability of the two species under N enrichment. Cleistogenes squarrosa had the highest SLA among the six species and a relatively high plasticity in mass-based leaf chlorophyll and N contents. The chlorophyll a/b ratio of C. squarrosa decreased significantly under N treatment, indicating declining light availability.

    ZHANG Rui-Qing, SUN Zhen-Jun, WANG Chong, YUAN Tang-Yu
    Chin J Plant Ecol. 2008, 32 (3):  622-631.  doi:10.3773/j.issn.1005-264x.2008.03.011
    Abstract ( 3126 )   Full Text ( 5 )   PDF (453KB) ( 1233 )   Save
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    Aims We tested the dynamics of nine enzymes during leaf litter decomposition in Xishuangbanna tropical rainforest both in the field and laboratory to explore the response of enzyme dynamics to decomposition under different food-web structures.

    Methods We used coarse and fine (1 mm and 100 μm mesh size, respectively) litterbags in the field to create different food-web structures during litter decomposition. Most soil macrofauna such as nematodes could access only the coarse mesh litterbags, leaving only microbiota such as mites in the fine mesh litterbags. In the laboratory, sterilization and inoculation were adopted to investigate different enzyme dynamics with nematodes or only microbiota participating in litter decomposition.

    Important findings Invertase and amylase increased more for shorter food webs at early stages of decomposition, while activities of endocellulase, β-glucosidase, xylanase and polyphenoloxydase increased to their maxima at later stages, but greater increase occurred with extended food webs. Invertase and amylase had negative and endocellulase, β-glucosidase, xylanase and polyphenoloxydase had positive relationships with litter decomposition (mass loss). Activities of enzymes responded to the process of litter decomposition. Invertase and amylase played key roles for microbiota utilizing the substrates at early stages of decomposition, while endocellulase, β-glucosidase, xylanase and polyphenoloxydase worked on the further decay of recalcitrant compounds at later stages. All enzymes related to C decay acted as effective indicators of litter decomposition. The decomposition of plant organic matter was essentially an enzymatic process.

    LI Zhi-Yong, CHEN Jian-Jun, WANG Yan-Hui, YU Peng-Tao, DU Shi-Cai, HE Ping, DUAN Jian
    Chin J Plant Ecol. 2008, 32 (3):  632-638.  doi:10.3773/j.issn.1005-264x.2008.03.012
    Abstract ( 3123 )   Full Text ( 3 )   PDF (288KB) ( 1050 )   Save
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    Aims In recent decades, frequent fires have destroyed large areas of coniferous Pinus massoniana forests in Chongqing, Southwestern China. Schima superba, a fire-resistant broadleaved tree species, has been widely planted on the burned areas. S. superba is thought to improve soil properties; however, little information is available from plantations exposed to acid deposition. Our objective was to examine the effects of S. superba plantations on soil chemical properties in the acid rain region.

    Methods We investigated soil chemical properties of a pure S. superba plantation planted on a burned area of a former pure P. massoniana plantation in the Tieshanping Forest Farm of Chongqing City using a soil core method. Results were compared with those from an adjacent unburned pure P. massoniana plantation, which was planted at the same time as the burned pure P. massoniana plantation.

    Important findings For 0-20 and 20-60 cm soil layers in the S. superba plantation, average pH values were 3.61 and 3.77 and average base saturation (BS) values were 4.68% and 7.92%, respectively. For these two soil layers in the P. massoniana plantation, average pH values were 3.78 and 3.88 and average BS values were 9.25% and 16.32%, respectively. Compared with the P. massoniana plantation, contents of exchangeable base cations (K+, Na+, Ca2+ and Mg2+) and total P were generally lower in the soil of the S. superba plantation, but contents of exchangeable Al3+, Fe3+ and H+ were significantly higher (p<0.05). This study suggested that theS. superba plantation accelerated soil acidification. Therefore, in the acid rain region of Chongqing, large areas of pure S. superba plantations should be avoided when using S. superba for establishment of fire-resistant forest belts or for regeneration and transformation of pure P. massoniana plantations.

    CHEN Ya-Jun, CAO Kun-Fang, CAI Zhi-Quan
    Chin J Plant Ecol. 2008, 32 (3):  639-647.  doi:10.3773/j.issn.1005-264x.2008.03.013
    Abstract ( 3096 )   Full Text ( 3 )   PDF (421KB) ( 1588 )   Save
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    Aims Lianas are an important component of forests, especially in the tropics. They strongly influence regeneration of trees and maintenance of species diversity in tropical forests, but little is known about competition between trees and lianas. In this study, we investigate the effects of lianas on the morphology, photosynthesis and growth of trees and examine the relative importance of above- and below-ground competition between tree and liana seedlings under different light irradiances.

    Methods We used four different competition treatments (AC: all competition; RC: root competition; SC: shoot competition; NC: no competition) between seedlings of one shade-intolerant liana (Byttneria grandif-olia) and three tree species (shade-tolerant Litsea dilleniifolia and Pometia tomentosa and shade-intolerant Bauhinia variegata). Seedlings were grown in a shade house under two levels of light availability (4% and 35% light intensity).

    Important findings Competition from lianas substantially reduced the growth of tree seedlings, but the relative importance of above- and below-ground competition differed between the two light levels. At low light intensity, the relative growth rate (RGR) and photosynthetic capacity (maximum net photosynthetic rate, Pmax) in seedlings of all three tree species were reduced more strongly by SC than RC. However, SC rather than RC greatly reduced RGR and Pmax of tree seedlings grown under high light intensity. Different competition combinations (above- and below-ground competition) of liana seedlings resulted in distinctive morphological traits in seedlings of the three tree species. The specific leaf area and leaf area ratio of the three tree species were significantly influenced by light intensity. Meanwhile, only those of the light demanding species, B. variegata, were affected by the liana competition. Tree seedlings had small diameter, low height, leaf numbers and leaf area with slight changes in slenderness (stem length/diameter) under the competitive environments of liana seedlings. In conclusion, our findings suggest that competition from liana seedlings can greatly suppress growth in tree seedlings of both shade-intolerant and shade-tolerant species and the effects of lianas on tree seedlings can differ with type of competition. Above- and below-ground competition can interactively limit the growth of tree seedlings.

    CHEN Zhi-Chao, SHI Zhao-Yong, TIAN Chang-Yan, FENG Gu
    Chin J Plant Ecol. 2008, 32 (3):  648-653.  doi:10.3773/j.issn.1005-264x.2008.03.014
    Abstract ( 2670 )   Full Text ( 2 )   PDF (250KB) ( 959 )   Save
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    Aims We investigated the effects of arbuscular mycorrhizal fungal (AMF) inoculation on growth and nutrient uptake in Plantago minuta and Erodium oxyrrhynchum, the most important ephemeral plants in Junggar Basin desert.

    Methods We inoculated with two AM fungi, Glomus etunicatum (BEG168) and G. mosseae (BEG167), as well as mixture of both species (M).

    Important findings Mycorrhizal colonization rates were 22%-60% and typical mycorrhizal structures were formed. Inoculation of both AM fungi improved plant vegetative growth by increasing biomass and plant height. Both plant species had significantly increased N and P concentrations. Seed number per potted plant of P. minuta inoculated with both AM fungi separately and together was significantly higher by 67%, 50% and 78%, respectively, than in non-inoculated plants. We conclude that AM fungi enhanced the two spring ephemeral plants in the extreme dry, nutrient-poor desert environments by improving N and P uptake and increasing seed number, which is important for maintaining populations.

    MENG Fan-Juan, WANG Qiu-Yu, WANG Jian-Zhong, LI Shu-Yan, WANG Jiang-Jiang
    Chin J Plant Ecol. 2008, 32 (3):  654-663.  doi:10.3773/j.issn.1005-264x.2008.03.015
    Abstract ( 2766 )   Full Text ( 2 )   PDF (466KB) ( 1164 )   Save
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    Aims Our objective was to compare tetraploid vs. diploid Robinia pseudoacacia for salt stress effects on their morphology, physiology, physiobiology, photosynthesis and anatomy.

    Methods We grew tetraploid and diploid R. pseudoacacia treated four times with two salts, NaCl and Na2SO4, and untreated diploid R. pseudoacacia as a control. After 30 days, we examined them every 7 days.

    Important findings The growth of diploid R. pseudoacacia was restrained, its water content and chlorophyll content had obvious differences to the control, and salt injury was eventually observed. The water content and chlorophyll content of tetraploid R. pseudoacacia had no obvious differences to the control, and salt injury was not observed. Relative REC (Relative conductivity) and Pro (Proline) activity of tetraploid R. pseudoacacia increased slightly, but were not different from the control. Relative REC and Pro activity in treated diploid R. pseudoacacia were higher than the control. The protective systems of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) retained higher activity at late periods in tetraploid R. pseudoacacia under salt stress, which contributed to salt tolerance, but they retained lower activity in treated diploid R. pseudoacacia. Photosynthesis in tetraploid R. pseudoacacia was not affected by salt stress, as net photosynthetic rate (Pn) and intercellular CO2 concentration (Ci) were unchanged, but changes did occur in diploid R. pseudoacacia. The leaf anatomy of tetraploid R. pseudoacacia changed, e.g., palisade cells were longer and more densely packed and spongy mesophyll cells were more densely packed. Based on these findings, tetraploid R. pseudoacacia had stronger salt tolerance.

    JU Chang-Hua, TIAN Yong-Chao, ZHU Yan, YAO Xia, CAO Wei-Xing
    Chin J Plant Ecol. 2008, 32 (3):  664-672.  doi:10.3773/j.issn.1005-264x.2008.03.016
    Abstract ( 2732 )   Full Text ( 1 )   PDF (394KB) ( 1128 )   Save
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    Aims Crop canopy reflectance, especially derivative spectrum, is a promising prospect for nondestructive rapid estimation of crop photosynthetic organ area and evaluation of crop growth status and yields. The purpose of our experiment was to investigate the quantitative relationships between derivative spectral parameters and photosynthetic organ area.

    Methods We used field experiments to study leaf area index (LAI), pod area index (PAI) and canopy hyperspectra reflectance of rapeseed (Brassica napus) under different nitrogen levels and in different cultivars and determined quantitative relationships between derivative spectral parameters and photosynthetic organ area.

    Important findings The correlation coefficient between photosynthetic organ area and derivative spectra was higher than that of canopy spectral reflectance of single band, with the best correlation at 750 nm (r=0.9). The correlation sequence of “three-edge parameters" to photosynthetic organ area was red edge>yellow edge>blue edge, area parameters>amplitude parameters>position parameters. Phenomenon of “two peak" at red edge of rape canopy spectra weakened the sensitivity of red edge position ( REP) to changes of biophysical parameters, but REP extracted from linear extrapolation method (REP(le)) strengthened it. Red edge area (SDr) and difference of SDr and blue edge area (SDb) (DSDr,b) from “three-edge parameters" and their derived parameters had the best correlation with LAI and PAI, and they were suitable for the different cultivars used in this study. Therefore, derivative spectral parameters, i.e., first derivative spectrum at 750 nm, SDr and DSDr,b could be used to effectively monitor area of photosynthetic organs in rapeseed.

    MIAO Bao-He, LI Xiang-Dong, LIU Bo, HE Qi-Ping, ZHU Tao, LIU Xing-Tan, ZHU Qi-Yu, QIAO Guang-Fa, FAN Ting-An, CHEN Cheng-Jun, DONG Qing-Yu, YU Song-Lie
    Chin J Plant Ecol. 2008, 32 (3):  673-680.  doi:10.3773/j.issn.1005-264x.2008.03.017
    Abstract ( 2998 )   Full Text ( 2 )   PDF (425KB) ( 1114 )   Save
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    Aims The objective of our study was better understanding of increased yield and economic benefits of high oil soybean with waving-canopy cultural type.

    Methods We used the high-oil soybean (Glycine max cv. Ludou 9) and studied the effects of waving-canopy cultural type on active oxygen and membrane lipid metabolism peroxidation in its leaves in field experiments and laboratory analyses during 2005-2006.

    Important findings The average content of soluble protein and soluble sugar was 1.56 and 3.82 mg·g-1 greater in the waving-canopy groups compared to CK (0.034% and 7.18%, respectively). Their contents increased 1.35% and 48.41% at podding and flowering growth stages, respectively, with all differences being statistically significant. Changes in the content of soluble protein and soluble sugar were much more favorable to C, N metabolism, and coordination of the source, storage and flow and metabolism of C was more meliorated and greater than that of N. Average activities of peroxidase (POD) increased by 20.13%, most increased by 46.53% at podding growth stages, and the difference was statistically significant. It was the key protective enzyme that had more effects than superoxide dismutase (SOD) and catalase (CAT). The average activities of SOD and CAT increased by 2.28% and 0.48%, respectively, while malondialdehype (MDA) content declined, and the ability for improvement against active oxygen increased and senility occurred slowly. POD, SOD and CAT all had the same trends, the activity of SOD appeared earlier than that of CAT and POD, and POD appeared lastly, i.e., these three enzymes had different effects at different growth stages. Therefore, this cultural type significantly affected the active oxygen and membrane lipid metabolism peroxidation of soybean, and it was much more favorable for the high oil soybean to gain high yield, fine quality and economic benefit.

    ZHANG Ya-Li, LUO Hong-Hai, ZHANG Wang-Feng, FAN Da-Yong, HE Za-Ju, BAI Hui-Dong
    Chin J Plant Ecol. 2008, 32 (3):  681-689.  doi:10.3773/j.issn.1005-264x.2008.03.018
    Abstract ( 3029 )   Full Text ( 1 )   PDF (644KB) ( 1280 )   Save
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    Aims Cotton (Gossypium hirsutum) is a major crop in Xinjiang Province, Northwest China. Because Xinjiang is characterized by deficiency of water resource and strong irradiance, study of water deficit on photoinhibition of cotton in this area is crucial not only for efficient irrigation, but also for physiological exploration of plant photo-protection strategy.

    Methods We investigated the effects of water deficit on physiological characteristics of cotton in the field. We measured diurnal variations of photon flux density (PFD), leaf temperature (Tleaf), pre-dawn maximal photochemical efficiency of PSⅡ (Fv/Fm), PSⅡ photochemical efficiency (ΦPSⅡ), electron transport rate (ETR), photochemical quenching (qp) and non-photochemical quenching (NPQ), as well as chlorophyll content and water potential of cotton leaves subjected to different water supplies.

    Important findings Compared to control (70%-75% of field capacity), the diurnal variation of leaf incident PFD was similar and Tleaf was higher with mild water deficit (55%-60% of field capacity). The diurnal variation of leaf incident PFD with moderate water deficit (40%-45% of field capacity) was similar before 12∶00 and then lower, as a result of leaf wilting than in the control. Leaf temperature with moderate water deficit was significantly higher than in the control during daytime. No significant effects were observed on pre-dawnFv/Fm; all values were between 0.83 and 0.84. There were no differences in diurnal variations of ΦPSⅡ, ETR and qp between mild water deficit and control. However, NPQ with mild water deficit was similar before noon and then lower than the control. At 12∶00,ΦPSⅡ, ETR and qp with moderate water deficit were significantly decreased and then recovered gradually to control values, possibly due to the decreased leaf incident PFD resulting from temporary and passive leaf wilting. However, NPQ with moderate water deficit was higher before 12∶00 and similar at 14∶00 but after that was lower than control. Water potential and chlorophyll content decreased with water deficits, but the Chl a/b ratio increased. All results showed that cotton leaves could acclimate to water deficit through changing leaf orientation and chlorophyll content to regulate light energy captured by leaves and changing electron transport rate and thermal dissipation ratio. We suggest that the risk of photosynthetic apparatus damage by excessive excitation energy could be decreased greatly through passive movement of cotton leaf wilting with moderate water deficit.

    LI Rong-Feng, CAI Miao-Zhen, LIU Peng, XU Gen-Di, CHEN Min-Yan, LIANG He
    Chin J Plant Ecol. 2008, 32 (3):  690-697.  doi:10.3773/j.issn.1005-264x.2008.03.019
    Abstract ( 2743 )   Full Text ( 3 )   PDF (354KB) ( 1065 )   Save
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    Aims Programmed cell death (PCD) plays an important role in plant growth and development, which correlates with adaptation of the plant to environment stress. Root border cells have many important biological functions in protecting the plant root tip from biotic and abiotic stress, which is a popular research topic recently. However, few studies have focused on PCD of root border cells and the phytoecological effect of aluminum on it. Our objective was to study the phytoecological and molecular ecological mechanism of root border cells in resisting aluminum (Al) toxicity.

    Methods We investigated change in viability of border cells, activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD), and PCD of root border cells by Al3+ induced in soybean (Glycine max) root tips with different Al3+ concentrations (0, 25, 50, 100, 200 and 400 μmol·L -1 Al3+) and treatment times (12 and 24 h). PCD was observed through Hoechst33342-PI fluorescent staining, DNA ladder and TdT-mediated dUTP nick end labeling (TUNEL) analysis.

    Important findings Aluminum can induce the death of root border cells. The viability of border cells decreases with increased Al3+ concentration and treatment time. The progressive delineation of fragmented DNA was coincident with the appearance of DNA ladder after being exposed to 400 μmol·L -1 Al3+ for 24 h. TUNEL analysis of border cells revealed that the nuclear DNA strand breaks can be identified by labeling free 3'-OH termini after treatment with 200 and 400 μmol·L -1 Al3+ for 12 h. Diaminobenzidine (DBA) staining indicated that the nucleus was positive and strong positive. Otherwise, CAT and SOD activities declined with increasing Al3+ concentration and treatment time under higher Al3+ concentration (>100 μmol·L-1), and we observed no significant differences in POD activity among different Al3+ concentrations and treatment times. These results indicated that border cell death may be a PCD under Al3+ stress. High Al3+ concentration induced PCD through enhancing reactive oxygen species (ROS), which is one of the ways of resisting adversity in plants.

    REN An-Xiang, HE Jin-Ming, XIAO Yan-Hui, WANG Yu-Mei
    Chin J Plant Ecol. 2008, 32 (3):  698-703.  doi:10.3773/j.issn.1005-264x.2008.03.020
    Abstract ( 2610 )   Full Text ( 2 )   PDF (264KB) ( 1181 )   Save
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    Aims The primary metabolism and secondary metabolism of plants are influenced by elevated CO2 concentration. There are many studies on primary metabolism, but few on secondary metabolism; therefore, we studied the effect of CO2 concentration on plant growth (primary metabolism), contents and components of essential oil (secondary metabolism) in fennel (Foeniculum vulgare).

    Methods After adding CO2 at three concentration levels (287.11, 532.88 and 780.46 μmol·mol -1) to a sealed phytotron for 70 days, we investigated plant growth, contents and components of essential oil in fennel.

    Important findings Plant height, inflorescence number, fresh and dry weight of inflorescence, whole plant dry weight and dry mass ratio increased, while node number and whole plant fresh weight did not change significantly. Soluble sugar and total carbon increased continuously, while total nitrogen and protein nitrogen exhibited the opposite trend. Pigment content in leaves decreased, but chlorophyll a/b ratio was not significantly different among plants. Contents of essential oil and yields of essential oil per plant were improved under elevated CO2 concentrations. We identified 22 kinds of components in essential oil, but there were no differences in components of essential oil among different CO2 concentration treatments. However, α-pinene, β-pinene, myrcene, p-cymene, tran-fenchyl acetate and (Z)-anethole were significantly different in relative contents of components (p<0.01), and sabinene, phellandrene, ocimene, γ-terpinene, 2,4,6-octatriene, 3,4-dimethyl-, estragole, fenchyl acetate, copaene, fanesene and germacrene were significantly different (p<0.05). Contents of (E)-anethole in essential oil increased under elevated CO2 concentrations, while contents of limonene decreased, but differences between contents of (E)-anethole and those of limonene were not significant.

    LIU Ya-Ling, LI Zuo-Zhou, JIANG Zheng-Wang, LIU Yi-Fei, HUANG Hong-Wen
    Chin J Plant Ecol. 2008, 32 (3):  704-718.  doi:10.3773/j.issn.1005-264x.2008.03.021
    Abstract ( 2898 )   Full Text ( 5 )   PDF (634KB) ( 2073 )   Save
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    Aims Gene introgression usually results from spontaneous hybridization in sympatric populations and has great impact on population genetic structure. Actinidia chinensis and A. deliciosa are two closely related species with different morphologies and polyploidy levels. Our objective was to analyze their genetic diversity, population genetic structure and hybridization introgression to clarify their evolutionary history and provide baseline data for conservation and management strategies.

    Methods We investigated five sympatric complex populations and two allopatric populations of A. chinensis and A. deliciosa using nine pairs of SSR primers and analyzed genetic diversity and differentiation indexes within and between species.

    Important findings We detected 196 alleles at the nine polymorphic loci among 432 individuals sampled from the seven locations. The percentage of alleles shared in the two species was 81.13%, and the percentage of species-specific alleles for A. chinensis and A. deliciosa was 13.27% and 5.61%, respectively. Intra-specific genetic diversity in both species was high. Nei's genetic differentiation among populations within or between species was low, indicating high gene flow among populations and between the two species. The UPGMA dendrogram clustered the sympatric complex populations. Individuals also were clustered into their own populations, whereas no correlation was found between population clustering and geographic distance. We discuss the combined impacts of wide-range distribution, outcrossing, late differentiation and other life history characteristics, as well as genome size of the genus, complex ploidy level and interspecific hybridization on the genetic variation and population structure of these two sympatric species. We concluded that the shared ancestral genetic polymorphisms and recent hybridization introgression between species in sympatric complex populations likely played a key role in formulating population structure of Actinidia species.

    HAN Guang-Xuan, ZHOU Guang-Sheng, XU Zhen-Zhu
    Chin J Plant Ecol. 2008, 32 (3):  719-733.  doi:10.3773/j.issn.1005-264x.2008.03.022
    Abstract ( 3163 )   Full Text ( 15 )   PDF (411KB) ( 1583 )   Save
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    Farmland ecosystems are important terrestrial ecosystems, representing about 10.5% of the earth's surface, and their CO2 emission amounts about 21%-25% of anthropogenic greenhouse gases emission. Farmland ecosystems are affected intensively by human activities; therefore, soil respiration of farmland ecosystems and their impacts are very important in the carbon budget of terrestrial ecosystems, as well as the global carbon cycle and carbon budget. With a long history of extensive agriculture, China provides a laboratory for soil respiration research. We review the previous decade of research advances in soil respiration of farmland ecosystems in China. Heat-water factors, crop biological characteristics and agricultural management activities played key roles in regulating the spatial and temporal variations of soil respiration. Root respiration accounts for 13%-77% of soil respiration, but the amounts are uncertain. Rational fertilization, straw return to soil and no-tillage are useful to soil CO2 emission reduction and soil carbon sequestration. We discuss key issues and further tasks, including comparison of soil respiration among typical farmland ecosystems in different areas, spatial variations of soil respiration, simulation of factors controlling soil respiration, and mitigation options of soil CO2 emission.

    WU Chao-Yang, NIU Zheng
    Chin J Plant Ecol. 2008, 32 (3):  734-740.  doi:10.3773/j.issn.1005-264x.2008.03.023
    Abstract ( 3261 )   Full Text ( 11 )   PDF (768KB) ( 2362 )   Save
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    Remote sensing technology has provided a rapid, nondestructive method for establishing relationships between photochemical reflectance index (PRI) and photosynthetic light use efficiency (LUE) that is an important parameter for estimating net primary productivity (NPP). Therefore, PRI opens a new era of estimating NPP that can overcome the shortcomings of the empirical model in obtaining LUE through information on temperature and water content. Many studies have demonstrated that a reliable relationship between PRI and LUE could be obtained at leaf, canopy and site scales. However, numerous confounding factors such as water content, leaf nitrogen concentration, leaf area index and sun zenith angle have emerged as scale changed, leading to disjunctive relationship betweenPRI and LUE. Thus, the functions of different factors on the relationship between PRI and LUE are important in understanding the mechanism for LUE estimation. This paper analyzes the confounding factors in establishing relationships between PRI and LUE and outlines possible improvements. Further research is needed on the different mechanism of reflectance at 526 nm and 545 nm relating to reflectance at 531 nm, the saturation problem of PRI with increase of LUE and the time and scale effects in estimating LUE with PRI.

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