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Table of Content
    Volume 34 Issue 11
    01 November 2010

    The landscape of subalpine vegetation in Western Sichuan, China, where Yan et al. investigate the pattern of plant community and its driver (Pages 1294–1302 of this issue). (Photographed by LIU Yang)

      
    Research Articles
    Short-term impacts of Ocnerodrilus occidentalis and Evodia lepta on soil CO2 fluxes in an Acacia auriculaeformis plantation in Guangdong Province, China
    GAO Bo, ZHANG Wei-Xin, LIU Su-Ping, SHAO Yuan-Hu XIONG Yan-Mei, ZHOU Cun-Yu, FU Sheng-Lei
    Chin J Plan Ecolo. 2010, 34 (11):  1243-1253.  doi:10.3773/j.issn.1005-264x.2010.11.001
    Abstract ( 1843 )   PDF (604KB) ( 1840 )   Save
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    Aims The exotic earthworm Ocnerodrilus occidentalis is widespread in plantation and abandoned areas in Guangdong, China. Its distribution is gradually expanding due to insensitivity to temperature, moisture, soil pH and soil organic matter. Study of the processes of soil carbon dynamics affected by O. occidentalis can provide new insights for the reduction of soil carbon emissions. Our objective was to investigate the short-term impacts of this exotic earthworm and native plants on soil CO2 fluxes. Methods A field experiment was conducted in an Acacia auriculaeformis plantation at the Heshan Hilly Land Interdisciplinary Experimental Station. CO2 fluxes were measured for 15 days in situ using the static chamber technique and analyzed with a gas chromatogram. Important findings Both O. occidentalis and Evodia lepta had no significant effects on soil CO2 fluxes. The effects of plant physical processes (such as shading), plant biological processes (such as secretion of root exudates) and overall processes on soil CO2 fluxes were –32.1%, 40.9% and 8.8%, respectively, in treatments without earthworm addition, and were –7.2%, 30.7% and 23.5%, respectively, in treatments with earthworm addition. Plant physical processes inhibited soil CO2 emissions, but enhanced the effects of the earthworm on soil CO2 emissions (increased by 39.3%). Plant biological processes enhanced soil CO2 emissions, but inhibited the effects of earthworms on soil CO2 emissions (decreased by 23.5%). Earthworm addition showed almost no significant impacts on most soil physical and chemical properties, but enhanced the activity of soil bacteria and led to a closer correlation between soil CO2 fluxes and soil physical and chemical properties. Meanwhile, earthworm activities changed the relationships between soil CO2 fluxes and soil hydrothermal factors. Hence, soil CO2 fluxes were not only influenced by hydrothermal factors, but also regulated by above- and below-ground biological processes. Therefore, it was difficult to determine an effective way to reduce forest soil CO2 emissions if only the amount of soil CO2 is considered and the impact of plant biological processes on soil CO2 fluxes is ignored. In order to reduce soil carbon efflux, it will be useful to note the potential of the independent and interactive effects of plant physical processes, plant biological processes and earthworm activity on soil CO2 flux.

    Short-term effects of night warming and nitrogen addition on soil available nitrogen and microbial properties in subalpine coniferous forest, Western Sichuan, China
    CHEN Zhi, YIN Hua-Jun, WEI Yun-Yan, LIU Qing
    Chin J Plan Ecolo. 2010, 34 (11):  1254-1264.  doi:10.3773/j.issn.1005-264x.2010.11.002
    Abstract ( 1776 )   PDF (586KB) ( 1682 )   Save
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    Aims The subalpine coniferous forest in eastern Qinghai-Tibet Plateau provides a natural laboratory for studying effects of climate change on terrestrial ecosystems. Research on responses of soil nitrogen availability and microbial properties to experimental warming and nitrogen addition can provide insights into their C resource/sink function under future climates. Methods We used an infrared heater combined with nitrogen addition to determine the short-term influences of two level of air temperature (ambient and warmed) and nitrogen addition (0 and 25 g N·m–2·a–1) on soil chemical properties, available nitrogen and microbial biomass. Important findings The warming manipulation increased mean air temperature and soil temperature at 5-cm depth by 1.93 and 4.19 °C, respectively, and the temperature increment was larger in summer and winter. Warming generally had no significant effects on soil pH, organic C, total N and microbial biomass, but it decreased soil ammonium nitrogen and increased nitrate nitrogen content. The warming effect was reduced with time. Nitrogen addition significantly increased available nitrogen and microbial biomass, but decreased soil pH, acidifying the soil. Compared with individually warming or adding nitrogen, the interaction of the two factors significantly increased organic C, available N and microbial biomass. Results suggest that soil nitrogen availability and microbial properties were sensitive to N status. Although soil nitrogen availability and microbial properties may adapt to temperature increase to some extent, the interaction of the warming and nitrogen addition significantly changed their response mode. Therefore, nitrogen deposition and multiple factors have interacting effects on the ecosystem and these should be further studied in this region.

    Soil heterotrophic respiration and its temperature sensitivity in different-aged orange plantations in Three Gorges Reservoir area of China
    ZHANG Wen-Li, LIU Ju, WANG Jian-Zhu, CHEN Fang-Qing
    Chin J Plan Ecolo. 2010, 34 (11):  1265-1273.  doi:10.3773/j.issn.1005-264x.2010.11.003
    Abstract ( 1850 )   PDF (455KB) ( 1720 )   Save
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    Aims Orange (Citrus reticulate) plantations, as the primary industry of the Three Gorges Reservoir area of China, play a significant regulatory role in the maintenance of ecological balance in the region. Our objectives were to examine the main factors controlling soil heterotrophic respiration and its temperature sensitivity in three different-aged orange plantations and discuss their potential responses to future climate change in this region. Methods A laboratory simulation was conducted with soil samples collected at 0–10 cm depth from three different-aged orange plantations in Yichang. Samples were incubated in the laboratory at 5, 15, 25, and 35 °C, respectively, and the alkali absorption method was applied to measure soil respiration. Soil physical and chemical properties were also measured. Important findings With increasing age of the plantation, soil organic content and total nitrogen content increased, while soil pH and microbial biomass carbon decreased. The younger orange plantations released less CO2 from soil heterotrophic respiration under all temperature conditions. Compared with other studies, temperature sensitivity coefficients of soil heterotrophic respiration (Q10) in the orange plantations in this region were relatively low (1.45–1.69). All Q10 value changed with culture time. The temperature sensitivity coefficient of soil heterotrophic respiration of the plantations decreased with planting years, indicating that younger orange plantations will be more sensitive to future global warming than the older ones.

    Relationship between woody plants phenology and climate factors in Xi’an, China
    BAI Jie, GE Quan-Sheng, DAI Jun-Hu, WANG Ying
    Chin J Plan Ecolo. 2010, 34 (11):  1274-1282.  doi:10.3773/j.issn.1005-264x.2010.11.004
    Abstract ( 2445 )   PDF (616KB) ( 2252 )   Save
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    Aims Few studies have investigated phenological response to climate change in Western China to understand ecological responses to climate change and evaluate phenological differences on a regional scale. We analyzed spring phenological data from 34 woody plants for the past 45 years in Xi’an. Our objectives were to determine the relationships between plant phenology and air temperature change and to explore the response of spring phenophases to abrupt climate change in Xi’an. Methods The Mann-Kendall test was used to describe the trend of temperature change and the specific point of climate change. The trends of spring phenophases were described by simple linear regression. The significance of correlation coefficients between phenophases and both temperature and precipitation were examined by t-tests. Important findings Four spring phenophases generally showed advancement, and the characters of phenological change were consistent with climate change, even abrupt climate change. Statistically significant correlation was found between the changes of spring phenophases and the temperatures of one or several months before the phenophase onset. The mean monthly temperature of the onset month or the prior month was the key factor impacting the spring phenophase. Moreover, there was a strong correlation between leaf phenophase and monthly precipitation of one month before the phenophase onset, while the correlation between flower phenophase and precipitation is not obvious.

    Diversity and distribution of vascular epiphytes in the tropical natural coniferous forest of Hainan Island, China
    LIU Guang-Fu, DING Yi, ZANG Run-Guo, XU Yang-Yu, LIN Chong, LI Xiao-Cheng
    Chin J Plan Ecolo. 2010, 34 (11):  1283-1293.  doi:10.3773/j.issn.1005-264x.2010.11.005
    Abstract ( 2087 )   PDF (478KB) ( 1834 )   Save
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    Aims As one of the most distinctive components of tropical forests, vascular epiphytes play vital roles in maintaining biodiversity and ecosystem functioning. The diversity and distribution of vascular epiphytes in tropical natural coniferous forest are reported systematically for the first time in this study. Our objective was to explore species richness, abundance, distribution patterns, and relationship between vascular epiphytes and host trees in the only Pinus latteri natural forest with large area in China. Methods Twelve plots of 10 m × 50 m were established in the tropical natural coniferous forest in Bawangling National Nature Reserve, Hainan Island, China. We recorded species, individuals and height of attachment of vascular epiphytes on each tree ≥ 5 cm diameter at breast height (DBH). Based on two datasets (individuals in each subplot of 10 m × 10 m and on each host tree), the horizontal distribution pattern of vascular epiphytes was analyzed using Kolmogorov-Smirnov test and Variance-to-mean Ratio. Based on species and individuals at 5 m intervals from the forest bottom to the top, the vertical structure of vascular epiphyte assemblages was analyzed. The relationship between vascular epiphytes and host tree size was assessed using Spearman correlation. Important findings We recorded 769 individual vascular epiphytes belonging to 27 species, 17 genera and 7 families in the total sample 0.6 hm2. The Orchidaceae and Asclepiadaceae were dominant. The vascular epiphytes were clumped horizontally. Vertically, 49.3% were at intermediate heights (10–20 m) and 19.0% at 0–5 m, but only 7.2% were at >25 m. Most vascular epiphytes showed no preference for host trees, but a few species, e.g., Phlegmariurus fordii, Eria rosea, Dischidia chinensis and Hoya pottsii had higher occurrence rates on the host tree of Pinus latteri. Vascular epiphyte abundance and species richness were both significantly positively correlated with host tree size.

    Plant community assembly rules across a subalpine grazing gradient in western Sichuan, China
    YAN Bang-Guo, WEN Wei-Quan, ZHANG Jian, YANG Wan-Qin, LIU Yang, HUANG Xu, LI Ze-Bo
    Chin J Plan Ecolo. 2010, 34 (11):  1294-1302.  doi:10.3773/j.issn.1005-264x.2010.11.006
    Abstract ( 2027 )   PDF (419KB) ( 2168 )   Save
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    Aims Community assembly rules are poorly understood, especially in subalpine areas. Plant communities are thought to be organized from a regional species pool through environmental filtering and competition. Environmental filtering will result in the formation of groups of species with similar traits, while competition will limit similarity of coexisting species. Environmental filtering and competition can also affect community phylogenetic structure when species niches are phylogenetically conservative. Our object was to uncover how these processes affected community assembly and their responses to grazing. Methods We sampled plant communities in six sites across a grazing gradient and calculated functional group evenness to test effects of environmental filtering and competition. For investigating community phylogenetic structure, we calculated nearest taxon index and net relatedness index using phylocom software. We examined community phylogenetic structures and functional group evenness under a grazing gradient using null model and phylogenetic indexes. Important findings We found strong nonrandom patterns in species richness distributions among functional groups in non-grazed plots, and functional group evenness significantly decreased with increased grazing pressure. There was a significant phylogenetic cluster in intensively grazing communities and this gradually became dispersion toward primary forest. As a filtering effect, grazing increased species richness of a few lineages and decreased others. This process resulted in community phylogenetic cluster or reductions in functional group evenness. Functional group evenness increasing and phylogenetic over-dispersion might stem from competition, which could limit similarity of coexisting species. Results indicated that both habitat filter and competition simultaneously shaped community structure. Findings suggest that grazing affected functional group evenness and phylogenetic structure through changing the balance between environmental filtering and competition in communities. The negative relationship between functional group evenness and species richness suggests that competition might suppress plant diversity in local communities. Results support that species functional divergence and their competition have important roles in community assembly.

    Reproductive characteristics of three different shaped stigma in flowers of the fig tree Ficus altissima
    ZHANG Yuan, YANG Da-Rong, PENG Yan-Qiong
    Chin J Plan Ecolo. 2010, 34 (11):  1303-1309.  doi:10.3773/j.issn.1005-264x.2010.11.007
    Abstract ( 1702 )   PDF (437KB) ( 1455 )   Save
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    Aims Conflicts of interest can be seen in the mutualism between fig trees and their species-specific fig wasp pollinators, where tree reproduction depends on pollen-carrying wasps whereas wasp fitness depends only on the latter. The factors that influence the balance of seed and fig wasp production are still debated. We have found flowers with three different shaped stigmas in the monoecious fig tree Ficus altissima at Xishuangbanna, China, and our objectives were to investigate whether these differences are related to the production of either seeds or fig wasps. Methods Flowers with different stigmal shapes were identified and counted using a dissecting microscope. We measured the style lengths associated with each stigma type and also the ovipositor length of the fig wasps Eupristina altissima and Eupristina sp. that attempt to lay their eggs down the styles. We identified the fate of flowers with each type of stigma using ovule differences after wasp entry and their style lengths. Important findings Based on their shape, we refer to the three types of stigma as globular, hook-like and torch-like. They accounted for 54.00%, 36.93% and 9.07% of the total female flowers, respectively. The style lengths of flowers with globular stigmas were significantly shorter than the others, but 85.73% and 96.01% of the styles were shorter than the lengths of the ovipositors of E. altissima and Eupristina sp., respectively. Most of their eggs were laid in short styled flowers, with globular stigmas (60.64%), whereas most of the seeds were produced by flowers with long styles and hook-like or torch-like stigmas. Flowers producing seeds therefore tend to have a different shaped stigma to those that produce wasps, and stigma shape reflects specialization for either male (pollen-carrying wasp) or female reproductive function. Consequently, it may be one of the factors that influence the balance between fig and fig wasp reproduction in F. altissima.

    Environment-dependent phenotypic variation among natural populations of Arabidopsis thaliana in the northern Tianshan Mountains
    LI Lei, LIU Tong, LIU Bin, SI Lang-Ming, LIU Zhong-Quan, SUN Qin-Ming, and SHEN Xue-Ying
    Chin J Plan Ecolo. 2010, 34 (11):  1310-1318.  doi:10.3773/j.issn.1005-264x.2010.11.008
    Abstract ( 1811 )   PDF (671KB) ( 1715 )   Save
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    Aims Little research has been done on natural environmental factors that impact phenotypic characters of Arabidopsis thaliana populations in their natural habitat. Our objective was to determine the distribution patterns of phenotypic characters and the relationship of phenotypic characters and environmental factors of A. thaliana populations. Methods From May to June 2009, we studied ten populations in the northern Tianshan Mountains. We placed 10 m × 10 m quadrats at each population plot, each comprised of about 400 smaller (0.5 m × 0.5 m) quadrats, and investigated the distributional patterns of populations and nine environmental factors. Twenty A. thaliana plants were selected, and ten phenotypic characteristics (branch number, plant height, plant biomass, root biomass, single fruit weight, fruit number per plant, fruits weight per plant, fruit length, fruit dehiscence force, fruit weight per plant/total weight) were measured. Variance, principal component and regression analyses were used. Important findings All phenotypic characteristics except branch number showed significant differences among populations, which indicated that there is strongly plasticity in the nine characters. The results of the analysis of variance and coefficients of variance indicated that fruit length and fruit dehiscence force have little variation within and among populations. Phenotypic characters varied little among different mountains, altitudes, latitudes and longitudes. The results indicated that A. thaliana populations mainly distributed on sandy soils that contained lower HCO3, pH values and higher soil organic carbon (SOC). The distribution frequencies of A. thaliana within populations are very low, ranging from 1.56% to 10.69%, with spatial autocorrelation distances being 15.4 to 46.7 cm and variable. Ten populations were all highly clumped in their distribution (p < 0.01), which was significantly correlated with the fruit dehiscence force, while the fruit dehiscence force increased as environmental stress increased. Results suggested that the growth and distribution of A. thaliana in the northern Tianshan Mountains are influenced mainly by microenvironments. In dry environments, A. thaliana would increases the ratio of reproduction distribution and produce poorly dehiscent fruits that make seeds disperse around maternal plants and utilize feasible habitats.

    Fine-scale spatial patterns of Stellera chamaejasme population in degraded alpine grassland in upper reaches of Heihe, China
    ZHAO Cheng-Zhang, GAO Fu-Yuan, WANG Xiao-Peng, SHENG Ya-Ping, SHI Fu-Xi
    Chin J Plan Ecolo. 2010, 34 (11):  1319-1326.  doi:10.3773/j.issn.1005-264x.2010.11.009
    Abstract ( 1917 )   PDF (502KB) ( 1706 )   Save
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    Aims The formation and changes of patches has an important effect on population patterns. Our objectives are to determine 1) how patches are formed during the process of Stellera chamaejasme population dispersion, 2) what is the effect on pattern during forming and changing of the patch and 3) what roles the formation and changes of the patches play in population dispersion. Methods We studied five 2 m × 2 m plots of different S. chamaejasme cover in the upper reaches of Heihe, China, using the point pattern method to analyze population pattern, size and density. Important findings With increasing cover, the population density and territory density tended to increase, decrease, and then increase and the number of the S. chamaejasme population tended to increase and decrease in turn. In the study area, the pattern under 31%–40% cover at all scales was a random distribution. Under the cover of 41%–50%, 51%–60%, 61%–70% and 71%–80%, the distribution pattern was random—clumped—random or regular—random—clumped—random and the clumped density was different. It formed patches during the process of S. chamaejasme population dispersion, which was clumped for external and random or regular for internal S. chamaejasme population dispersion through which patches combine and annex.

    Predicting potential geographical distributions and patterns of the relic plant Gymnocarpos przewalskii using Maximum Entropy and Genetic Algorithm for Rule-set Prediction
    MA Song-Mei, ZHANG Ming-Li, ZHANG Hong-Xiang, MENG Hong-Hu, CHEN Xi
    Chin J Plan Ecolo. 2010, 34 (11):  1327-1335.  doi:10.3773/j.issn.1005-264x.2010.11.010
    Abstract ( 2132 )   PDF (591KB) ( 2260 )   Save
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    Aims Understanding the geographical distribution and patterns of endemic species is critical to biodiversity conservation and biogeographical history reconstruction of the area occupied by the species. The ecological niche models (ENMs) are useful techniques to explore the links between the species distribution and the environmental data. The displayed potential habitats for the species, in turn can enable the examination of the predictive abilities of various ENMs. We attempt to determine the potential geographic distributions of the Tertiary relic plant Gymnocarpos przewalskii based on the model of maximum entropy (MAXENT) and genetic algorithm for rule-set prediction (GARP). Methods Based on sixteen sampled localities and seven environmental layers (isothermality, maximum temperature, minimum temperature, annual precipitation, potential evapotranspiration ratio (PER), altitude and soil types), we conducted predictions of G. przewalskii using MAXENT and GARP models. The spatial distribution maps of G. przewalskii with the different environmental suitable values (MAXENT) or overlap index (GARP) displayed the distribution patterns clearly. Important findings The potential distributions of G. przewalskii with the highest environment suitability are predicted at first in the middle of Hexi corridor and the western Yumen of Gansu Province, the north of Ningxia-Hui Autonomous Region, and the part of the Wulate banner of Inner Mongolia in China. The others are mainly in northwestern Tarim Basin and small isolated areas in northwestern Qaidam Basin. Both MAXENT and GARP produced good predictions for G. przewalskii. However, GARP predicted larger and more continuous suitable habitats around the species’ locations and some isolated and fragmented spatial predictions where the species has never been found or collected before. MAXENT predicted a distribution that is a logical proportion of the study area and removed most of the unlikely isolated habitats.

    Variations of morphology, anatomical structure and nitrogen content among first-order roots in different positions along branch orders in tree species
    LIU Ying, GU Jia-Cun, WEI Xing, XU Yang, WANG Zheng-Quan
    Chin J Plan Ecolo. 2010, 34 (11):  1336-1343.  doi:10.3773/j.issn.1005-264x.2010.11.011
    Abstract ( 1860 )   PDF (533KB) ( 1619 )   Save
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    Aims First-order roots play a key role in water and nutrient uptake from soil, and their positions along the branch orders may display differences in functions. However, few studies focused on the structure and functions of first-order roots with different positions in trees. Our objective was to explore the differences in morphological, anatomical and chemical properties among first-order roots with different branching positions and to understand the correlation between root structure and functions. Methods First-order root samples from plantations were separated into three categories, Ar (from 2nd-order roots), Br (from 2nd–4th-order root tips) and Cr (from 3rd–5th-order roots). We made paraffin slices stained by safranin and fast green to observe anatomical traits, including cortex proportion, development of stele and protoxylem type. We also examined morphology and tissue nitrogen concentrations among these roots. Important findings The first order roots in different branch positions showed differences in morphology and anatomy in three hardwood trees. Compared with root Br and root Cr, root Ar have larger root numbers, shorter length, lower stele/root diameter ratio, higher cortex proportion and N concentration, and more diarch roots. Root Br and Cr have smaller root numbers, longer length, higher stele/root diameter ratio, lower cortex proportion and N concentration, and more triarch-pentarch roots. These results suggest that the differences of the first-order roots in morphology, anatomy and tissue chemistry are related to root positions along branch orders, and are important in understanding root structures and functions in trees, particularly in revealing the roles of fine root longevity and turnover in forest ecosystems.

    Review
    A review of protective ant-plant interaction and its mediation mechanism
    ZHANG Shuang, ZHANG Yu-Xin, MA Ke-Ming
    Chin J Plan Ecolo. 2010, 34 (11):  1344-1353.  doi:10.3773/j.issn.1005-264x.2010.11.012
    Abstract ( 2067 )   PDF (391KB) ( 2441 )   Save
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    The mutualistic relationship between ants and plants is one of the model systems in ecological and evolutionary research. We review the protective ant-plant interaction and its mediation mechanisms. Plants often offer rewards such as food bodies, domatia or honeydews for ants; in return ants protect the host plant from animal herbivory, increase seed production and quality and enhance the competitive dominance of host plants. The protection effect is positive in most cases even though many biotic and abiotic factors vary significantly. The interaction has a broad range of ecological influences, especially on the species richness and abundances of canopy arthropods. Future research should address the origin and maintenance mechanisms of the mutualism, its impacts on partner ants, its relationship with species invasion and its evolutionary ecology significance.

    A review of progress in roles of organic acids on heavy metal resistance and detoxification in plants
    FU Xiao-Ping, DOU Chang-Ming, HU Shao-Ping, CHEN Xin-Cai, SHI Ji-Yan, CHEN Ying-Xu
    Chin J Plan Ecolo. 2010, 34 (11):  1354-1358.  doi:10.3773/j.issn.1005-264x.2010.11.013
    Abstract ( 2106 )   PDF (289KB) ( 2490 )   Save
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    Mechanisms of heavy metal tolerance and detoxification in plants can be divided into two categories, external exclusion and internal tolerance. We reviewed the effects of organic acids as a kind of metal chelators in both processes in plants. In the external detoxification process, organic acids excreted from plant roots may form stable metal-ligand complexes with heavy metal ions and change their mobility and bioavailability, thus preventing the metal ions entering plants or avoiding their accumulation in the sensitive sites of roots. In internal metal detoxification, organic acids may chelate with heavy metal in cytosol, where the ions can be transformed into a non-toxic or less toxic form.


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