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Table of Content
    Volume 33 Issue 4
    30 July 2009
    Research Articles
    ZHANG Chong-Bang, WANG Jiang, KE Shi-Xing, JIN Ze-Xin
    Chin J Plan Ecolo. 2009, 33 (4):  629-637.  doi:10.3773/j.issn.1005-264x.2009.04.001
    Abstract ( 2302 )   PDF (818KB) ( 1577 )   Save
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    Aims Our objectives are to 1) evaluate the transformation of heavy metal speciations, the mineralization of soil microbial community and diversity of soil microbial community along an inhabitation gradient of Miscanthus floridulus and 2) test relationships between heavy metal speciations and microbial parameters during natural inhabitation by M. floridulus. This is the first step towards large scale application of M. floridulus to the revegetation of mine tailings.
    Methods On the basis of the cover of M. floridulus, four levels of inhabitation were selected, along with one bare site for comparison. Three sample plots were randomly placed in each of the five sites, and rhizosphere soil samples were collected from five randomly selected plants in each plot. Heavy metal speciations were analyzed using Tessier’s sequent extraction techniques plus ICP-OES apparatus. Mineralization of the microbial community was determined using soil-culturing methods, and diversity of the microbial community was tested using BIOLOG-Ecoplate.
    Important findings Natural inhabitation by M. floridulus significantly increased ratios of individual heavy metal content bound to carbonates and sulfide-organic matter to total corresponding heavy metal content (p < 0.05), but decreased the heavy metal ratios bound to residual fraction (p < 0.05). Cellulose decomposition, phenol transformation, nitrogen fixation, ammonification, nitrification, organic phosphorus decomposition, functional diversity of the soil community and utilization by the soil microbial community of four carbon substrate groups (carbohydrates, polymers, amines/amides and miscellaneous) significantly increased with inhabitation by M. floridulus (p < 0.05), but the utilization of amino acids significantly decreased (p < 0.05). Canonical correlation analysis showed that the aggregated changes in microbial functional parameters were significantly and positively related to the heavy metal ratios bound to carbonates and sulfides-organic matter, but were significantly and negatively related to the heavy metal ratios bound to residuals fractions. Our results indicated that natural inhabitation by M. floridulus not only promoted transformation of heavy metals in the mine tailing sand to precipitated and chelated speciation, but also significantly improved functioning of the microbial community. Therefore, M. floridulus exhibited potential for the revegetation of abandoned mining lands contaminated with heavy metals.
    LIANG Sheng-Wei, HU Xin-Wen, DUAN Rui-Jun, FU Shao-Ping, GUO Jian-Chun
    Chin J Plan Ecolo. 2009, 33 (4):  638-645.  doi:10.3773/j.issn.1005-264x.2009.04.002
    Abstract ( 2254 )   PDF (557KB) ( 1360 )   Save
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    Aims Mercury pollution is a global environmental problem, and heavy metal hyperaccumulator and plant detoxicity is a promising method and current research area. Our objective was to study the halophyte Sesuvium portulacastrum to determine its Hg tolerance and accumulation in order to find a new phytoremediation plant.
    Methods Cuttings of S. portulacastrum with one node and two opposite leaves were cultivated on 1/10 Hoagland nutrient solution supplemented with HgCl2 (0, 5, 10, 25, 50 μmol·L–1). After 30 d of treatment, we measured growth phenotype and physiological changes such as proline, chlorophyll, electrolyte leakage and Hg2+ concentration.
    Important findings Under low Hg2+ concentration stress (10 μmol·L–1), plants showed vigorous growth. The levels of proline, malondialdehyde and electrolyte leakage were similar to those in the untreated plants, but the chlorophyll content was increased. The species could accumulate Hg2+, especially in roots, which reached 33.9 μg·g–1 DW with 50 μmol·L–1 Hg2+ stress. The plants that accumulated 12.02 μg·g–1 DW Hg2+ in roots grew well. Thus, S. portulacastrum shows strong Hg2+ tolerance and accumulation.
    MA Jiang-Ming, LIU Shi-Rong, SHI Zuo-Min, ZHANG Yuan-Dong, MIAO Ning
    Chin J Plan Ecolo. 2009, 33 (4):  646-657.  doi:10.3773/j.issn.1005-264x.2009.04.003
    Abstract ( 2341 )   PDF (1027KB) ( 1227 )   Save
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    Aims Subalpine dark coniferous forests in western Sichuan, China include natural old-growth forests and successional forests that regenerated mainly following logging over the past 50 years. Both the bamboo and moss forest types are comprised of three different restoration stages: broad-leaved forest 20–40 years old, conifer/broad-leaved mixed forest 50 years old and old-growth dark coniferous forest 160–200 years old. Our objectives were to understand how subalpine dark coniferous forests naturally regenerated following disturbance and determine key factors influencing natural regeneration.
    Methods We investigated densities of seedlings, saplings and small trees of the climax dominant tree species Abies faxoniana in 50 quadrats along a gradient of the different successional stages in both the bamboo and moss forest types located at 3 100–3 600 m elevation on north or northwest aspects.
    Important findings The densities of seedlings, saplings and small trees of A. faxoniana were generally relatively low in both the bamboo and moss forest types, but higher than that in moss forest types. Key factors enhancing natural regeneration of A. faxoniana in the bamboo forest types were density of seed-bearing trees and the stock of fallen wood. Negative factors were coverage of bamboo and thickness of moss. In the moss forest types, the coverage of shrubs and thickness of moss enhanced the occurrence of seedlings of A. faxoniana but limited the development of saplings and small trees.
    LI Xiao-Liang, WANG Hong, ZHENG Zheng, LIN Lu-Xiang, DENG Xiao-Bao, CAO Min
    Chin J Plan Ecolo. 2009, 33 (4):  658-671.  doi:10.3773/j.issn.1005-264x.2009.04.004
    Abstract ( 2524 )   PDF (1029KB) ( 1212 )   Save
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    Aims Tree seedlings are a vital component of forest ecosystems because they determine natural regeneration; however, they are poorly understood, especially in tropical areas. Our objectives were to examine the characteristics of seedling composition, spatial distribution of the dominant seedlings and changes in survival of newly established seedlings during the dry season in a tropical forest in Xishuangbanna, China.
    Methods In late October 2007, we established 450 1-m2 seedling plots in a 20 hm2 tropical forest dynamics plot and completed the first survey, in which tree seedlings with DBH <1 cm were tagged, measured and identified to species. We re-censused the seedlings in late February and again in early May 2008. We selected newly established seedlings (height ≤30 cm) in 2007 to analyze survival of seedlings during the dry season from 2007 to 2008.
    Important findings The plot had relatively high tree seedling richness and differences in numbers of seedlings among species. The 6 367 tree seedlings identified and recorded represented 49 families, 116 genera and 161 species (277 other seedlings were unidentified). The seedlings had values of Simpson, Shannon-Wiener and Pielou indexes of 0.69, 2.29 and 0.45, respectively. Species with <5 individuals accounted for 50.31% of the total number of species. At the 1-m2 scale, the seedling density and species richness were (14.15 ± 0.72) ind.·m–2 and (3.73 ± 0.10) sp.·m–2 (Mean ± SE, n = 450), respectively. Dominant seedlings included Parashorea chinensis, Castanopsis echidnocarpa and Pittosporopsis kerrii, which displayed different spatial distribution patterns closely associated with the topography, altitude and spatial patterns of their parent trees. During the dry season, 26.49% of the seedlings died, mainly dominant species. Mortality patterns varied widely among seedlings, e.g., mortality rates were 62.65% and 35.87% for Litsea panamanja and Parashorea chinensis, respectively. However, low mortality rates (<9%) occurred in the seven dominant seedlings (Pittosporopsis kerrii, Mezzettiopsis creaghii, etc.). In addition, except for the 13 dominants (Parashorea chinensis, etc.), seedlings of the other 129 species had a combined mortality of 10.40%, and 91 of these 129 species lost no individuals.
    JIAN Min-Fei, LIU Qi-Jing, ZHU Du, YOU Hai
    Chin J Plan Ecolo. 2009, 33 (4):  672-680.  doi:10.3773/j.issn.1005-264x.2009.04.005
    Abstract ( 2325 )   PDF (518KB) ( 1416 )   Save
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    Aims The Jiulianshan Mountain National Nature Reserve of Jiangxi is rich in typical natural evergreen broad-leaved forest communities; however, little is known about the interspecific relationships of the species that dominate the tree layer. Our objective was to investigate how the dominant species in the tree layer interact with each other and with other species.
    Methods We sampled 7 600 m2 with 19 plots in the typical evergreen broad-leaved communities, selected 28 dominant species according to importance values and studied interspecific associations and correlations by using variance ratio (VR) analysis of the overall association and χ2 test, Pearson correlation coefficient test and Spearman rank correlation coefficient test based on 2×2 contingency tables of species presence/absence data.
    Important findings Significantly positive correlations exist among the 28 dominant species, which suggests that the evergreen broad-leaved forest is stable. The interspecific correlations among 378 species-pairs of the 28 dominant tree species showed that 140, 104 and 144 species-pairs were positively correlated, while 238, 274 and 234 species-pairs had negative correlations, and the ratios of positive and negative correlations were 0.588, 0.380 and 0.615, based on χ2-test for 2 ×2 contingency table, Pearson correlation coefficient test, and Spearman rank correlation coefficient test, respectively. The Spearman rank correlation coefficient test was more sensitive than the Pearson correlation coefficient test. Most of the total 378 species pairs did not show significant association, which may be related to the seral stage of the forest and the ecological characteristics of the species. The forest was at a stable late-successional stage. According to their adaptability to the environment and relationships between plants and environment, the 28 species were divided into two ecological species groups: shade-intolerant and shade-tolerant plants.
    WANG Yang, DU Guo-Zhen, GUO Shu-Qing, ZHAO Zhi-Gang
    Chin J Plan Ecolo. 2009, 33 (4):  681-688.  doi:10.3773/j.issn.1005-264x.2009.04.006
    Abstract ( 2379 )   PDF (456KB) ( 1571 )   Save
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    Aims We predict that limited resources can enhance the trade-off between size and number of capitula and seeds, showing a strategy of plants. We used Saussurea japonica to investigate the relationship under different levels of light and nutrition. Our objectives are to determine 1) effects of different light and nutrition levels on characters of capitula and seeds, 2) the relationship between size and number of capitula and seeds under different light and nutrition levels and 3) whether the limitation of light and nutrition enhances the trade-off between size and quantity of capitula and seeds.
    Methods We planted S. japonica in pots under four treatments: combination of two light levels (high and low) and two nutrition levels (high and low). We counted and weighed (after oven-drying at 80 °C for 72 h) capitula and seeds.
    Important findings The treatments of light and nutrition had no significant effects on the number of capitula, while the effects on the mass of capitula were significant. The different treatments had significant effects on both size and number of seeds. Moreover, the relationships between size and number were influenced by different treatments of light and nutrition: under control and low nutrition level, significant positive correlations were observed between size and number for the capitula and seeds; however, significantly negative correlations between size and number were found for the capitula and seeds at the low light treatment and the low light + low nutrition treatments, exhibiting the size-number trade-off. Results suggest that environmental stress (such as low soil nutrition and limited light) enhanced the trade-off between size and number of capitula and seeds, consistent with our prediction. The trade-off can be a response of S. japonica to varied environments, which may improve the adaptability of this plant.
    LI Qiu-Hua, HE Wei-Tian, CHEN Chuan
    Chin J Plan Ecolo. 2009, 33 (4):  689-697.  doi:10.3773/j.issn.1005-264x.2009.05.007
    Abstract ( 2408 )   PDF (706KB) ( 1163 )   Save
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    Aims Our objectives were to understand the structure of the phytoplankton community and the relationships between phytoplankton abundance and environmental factors in wetlands of Macao.
    Methods Water and phytoplankton samples were collected in July and October 2007 and January 2008 at the four sites of Fai Chi Kei Bay, Taipa-colonva mudflats, Lotus Flower Bridge and Praia Grande Lake. Phytoplankton was fixed with formaldehyde with a final concentration of 3%–5% (v/v). Water temperature, conductivity, dissolved oxygen were measured in situ with 85-ⅡYSI Multiparameter Water Quality Monitor. Water transparency was determined with Secchi Disk Depth. Water pH was measured with pHS-3C acid-alkalinity parameter Water Quality Monitor. Chlorophyll a was obtained from a sample of 400 ml water filtered through a Whatman GF/A filter. Concentrations were determined after <8 h extraction in 90% acetone. Nutrient concentrations were measured by using GB3838-2002.
    Important findings Cyanobacteria, chlorophytes and diatoms had the largest numbers of species. We identified 76 species of algae, including 13 species of Cyanophyta, 30 species of Chlorophyta and 25 species of Bacillariophyta. Maximum abundance was at Lotus flower bridge (3 922.33×104 cells·L–1) and maximum abundance of Cyanophyta was in July and Bacillariophyta was in January. Minimum abundance was at Praia Grande Lake (1.58×104 cells·L–1). Values of the Shannon-Wiener Index of diversity indicated that Fai Chi Kei Bay was seriously polluted in January and Lotus Flower Bridge in July and October, while others were little or moderately polluted. Water transparency was the most important environmental factor affecting phytoplankton dynamics at the four wetlands and was strongly positively correlated to Chlorophyta (r = 0.683, p < 0.05), Pyrrophyta (r = 0.715, p <0.05), Cryptophyta (r = 0.707, p <0.05) and Chrysophyta (r = 0.701, p <0.05). Bacillariophyta was negatively correlated to pH value (r = – 0.674, p <0.05) and positively correlated to total nitrogen (r = 0.895, p <0.05), total phosphorus (r = 0.920, p <0.05) and soluble reactive phosphorus (r = 0.668, p <0.05).
    LIU Chang-Cheng, WEI Ya-Fen, LIU Yu-Guo, GUO Ke
    Chin J Plan Ecolo. 2009, 33 (4):  698-705.  doi:10.3773/j.issn.1005-264x.2009.04.008
    Abstract ( 2222 )   PDF (360KB) ( 1205 )   Save
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    Aims Information on community biomass is very important for understanding the structure, function and productivity of ecosystems; however, the biomass of karst forests is difficult to measure because of high habitat heterogeneity, complex and irregular growth forms, etc., and it seldom has been studied. Our objective was to study the biomass of karst forests to learn the structure and function of the ecosystems.
    Methods We estimated biomass and allocation of tree and shrub layers in three karst forest communities at an ecological research station in Puding, Guizhou, using allometric analysis and sampling harvest methods.
    Important findings Biomass regression models were established for three diameter classes (<1, 1–5 and >5 cm) and 15 abundant species: Platycarya longipes, Lithocarpus confinis, Itea yunnanesis, Kalopanax septemlobus, Machilus cavaleriei, Quercus aliena, Lindera communis, Lindera pulcherrima var. hemsleyana, Rhamnus hetrophylla, Stachyurus obovatus, Rhamnus leptophylla, Zanthoxylum esquirolii, Zanthoxylum planispinum, Myrsine africana and Zanthoxylum dimorphophyllum var. spinifolium. Average biomass of canopy and shrub layers was 88.7×103 kg·hm–2, with the tree layer accounting for about 98% of the total. Biomass allocation among different diameter classes was concentrated in the individuals > 10 cm diameter at breast height. Ten species made up about 98% of the total biomass of canopy and shrub layers, and the total biomass was concentrated in the dominant trees.
    LIU Chen-Feng, ZHANG Zhi-Qiang, SUN Ge, ZHA Tong-Gang, ZHU Jin-Zhao, SHEN Li-Hua, CHEN Jun, FANG Xian-Rui, CHEN Ji-Quan
    Chin J Plan Ecolo. 2009, 33 (4):  706-718.  doi:10.3773/j.issn.1005-264x.2009.04.009
    Abstract ( 2504 )   PDF (955KB) ( 1405 )   Save
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    Aims Using field data from an eddy-covariance (EC) flux tower and sap-flow sensors installed in a poplar (Populus euramericana) plantation, we investigated the magnitudes and changes of evapotranspiration (ET) under different soil moisture and climatic conditions. Our objectives were to quantify the energy partitioning and energy balance, explore the dynamic process and regulatory mechanisms on ET, and understand primary biophysical regulations, especially soil moisture.
    Methods An open path EC system, sap-flow sensors, soil water balance monitoring system, and microclimatic station were installed to record various components of energy fluxes and water budget at an 11-year-old poplar plantation in Daxing District, Beijing, China. We used data collected at 30-min intervals in the growing season of 2006 in this study.
    Important findings The overall energy closure of the study site was high (86%) during the growing season, but with notable dependence on soil water conditions. The ratio between sensible heat and net radiation (Hs:Rn) was much higher during dry conditions than that during moist conditions. With dry soils, net radiation and soil physical properties played important roles in transpiration, which was less than evaporation prior to rain events. In contrast, transpiration exceeded evaporation when the soil water content in the deep layers was more abundant following rain events. The total ET rates quantified by the soil water balance and sap-flow methods were comparable and lower than that determined by the EC method. The ratio between transpiration and ET appeared to be more dependent on net radiation and vapor pressure deficit (VPD) during wet periods than that during dry periods.
    ZANG Chun-Xin, YANG Jie, YUAN Jie, LIU Xin, SONG Bing-Yu
    Chin J Plan Ecolo. 2009, 33 (4):  719-727.  doi:10.3773/j.issn.1005-264x.2009.04.010
    Abstract ( 2389 )   PDF (817KB) ( 1285 )   Save
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    Aims Caragana intermedia is an excellent wind-breaking and sand-fixing shrub species. There are many reports of transpiration measurements of C. intermedia, most of which extrapolated the transpiration water consumption of entire shrubs from measurement of a single leaf or shoot. Our objective was to study diurnal changes of sap flow for entire individuals of C. intermedia.
    Methods We selected three C. intermedia plants in the Mu Us Sandy Land of north-central China and measured sap flow with a thermal dissipation probe, also called Granier sap-flow probe. The sap-flow sensor includes two probes, each of them containing a copper constantan thermocouple. We inserted the probes into the taproot, with one probe about 4–5 cm above the other, used solar film to seal the top of the cover against the bark to prevent rainwater from entering and obtained continuous measurements.
    Important findings The diurnal changes of sap flow in C. intermedia individuals can be divided into 4 phases: 1) rapid ascending phase (8:00–11:30), 2) stationary high phase (12:00–18:00), 3) rapid descending phase (18:30–21:00) and 4) stationary low phase (21:30–8:00) of the next day, accounting for 21.21%, 58.84%, 10.62% and 9.32% of the sap flow, respectively. From 12:00 to 14:00, however, transpiration fluctuated slightly because of the environment (e.g., clouds), but there was no obvious “noon break”, as the transpiration rate remained high. The sequence of environmental factors that impacted sap flow was: solar radiation > air temperature > vapor pressure deficit > air relative humidity > soil temperature > wind, and there was an obvious time lag between the sap flow and the environment factors. Based on the diurnal change data, we calculated that the transpiration water consumption of an individual C. intermedia shrub is 2.2 kg · d-1.
    TU Li-Hua, HU Ting-Xing, HUANG Li-Hua, LI Ren-Hong, DAI Hong-Zhong, LUO Shou-Hua, XIANG Yuan-Bin
    Chin J Plan Ecolo. 2009, 33 (4):  728-738.  doi:10.3773/j.issn.1005-264x.2009.04.011
    Abstract ( 2351 )   PDF (744KB) ( 1844 )   Save
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    Aims Our objectives were to determine the effect of increased nitrogen deposition on total soil respiration and microbial respiration of Pleioblastus amarus forest, and whether increased nitrogen deposition alters the temperature sensitivity of soil respiration.
    Methods For one year starting November 2007, we conducted a simulated nitrogen deposition field experiment in P. amarus forest, Rainy Area of West China. The levels of nitrogen deposition were control (CK, 0 g N·m–2·a–1), low nitrogen (5 g N·m–2·a–1), medium nitrogen (15 g N·m–2·a–1) and high nitrogen (30 g N·m–2·a–1). At the end of each month, soil respiration was measured by infrared gas analyzer, and NH4NO3 was added to N-treated plots. Natural wet nitrogen deposition was measured in 2008, and 0–20 cm horizon soil was collected for soil respiration sampling in November 2008. These soil samples were maintained in the laboratory at 20 ℃, and we measured soil microbial respiration (by infrared gas analyzer) and microbial biomass carbon and nitrogen.
    Important findings The wet nitrogen deposition of Liujiang, Hongya County is 8.241 g·m–2; it exceeds the local nitrogen deposition critical loads. Root respiration accounts for about 60% of the total soil respiration of P. amarus forest from April to October. Nitrogen deposition promotes soil respiration of P. amarus forest, and CO2 release from forest soil is increased by 9.4%–28.6%. Microbial respiration, microbial biomass carbon and nitrogen were stimulated by nitrogen deposition, and respiration rate rises with increased nitrogen deposition. The soil respiration rate exhibited positive exponential relationships with air temperature and soil temperature at 10 cm depth. Exponential relationships between temperature and soil respiration were highly significant in all plots. Nitrogen deposition may increase temperature sensitivity of soil respiration. With increasing rates of anthropogenic N deposition and global warming, nitrogen combined with temperature may increase the release of CO2 from P. amarus forest soil.
    WANG Guang-Jun, TIAN Da-Lun, YANG Wen-De, ZHU Fan, XIANG Wen-Hua, LIANG Xiao-Cui
    Chin J Plan Ecolo. 2009, 33 (4):  739-747.  doi:10.3773/j.issn.1005-264x.2009.04.012
    Abstract ( 2317 )   PDF (495KB) ( 1282 )   Save
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    Aims Soil respiration is the largest carbon flux in forest ecosystems except for canopy photosynthesis, but the effect of litter on soil respiration in Cunninghamia lanceolata plantations is poorly understood. Our objectives were to examine quantitative differences in changes in soil respiration induced by litter exclusion and addition and to determine how litter manipulation affects soil CO2 flux in C. lanceolata plantation ecosystems.
    Methods We measured soil respiration with an infrared gas exchange analyzer (Li-6400-09) in Tianjiling National Forestry Park, Changsha, Hunan, China from January to December 2007. In the litter exclusion treatment, all ground litter was removed and aboveground litter input was excluded. In the litter addition treatment, litter removed from litter exclusion plots was added to produce double litter. Soil temperature and moisture were measured at 5 cm depth at the same time as soil respiration measurements.
    Important findings The treatments of litter exclusion and addition had significantly different seasonal patterns of CO2 flux processes. Average soil respiration rates of litter exclusion and addition plots were 159.2 and 216.8 mg CO2·m–2·h–1, respectively. The soil respiration rate with litter exclusion was 15.0% lower than the control (180.9 mg CO2·m–2·h–1) and with litter addition was 17.0% higher than the control. Significant exponential relationships were found between soil temperature and soil respiration rate under both treatments, and soil temperature could explain 85.3% and 89.6% of the seasonal changes in soil respiration in the litter exclusion and litter addition plots, respectively. The relationship between soil respiration rate (y) and soil temperature (t) was described by the regression equations: y=27.33e 0.087 2t (R2=0.853, p﹤0.001) and y=37.25e 0.088 8t (R2=0.896, p﹤0.001) in the litter exclusion and addition plots, respectively. The Q10 values in the litter exclusion and litter addition plots were 2.39 and 2.43, higher than the control (2.26). The results indicated that litter-fall is an important factor affecting soil CO2 efflux in forests.
    URIANKHAI Tselmeg, LIU Mao-Song, HUANG Zheng, CHEN Bin, ZHANG Ming-Juan, XU Chi
    Chin J Plan Ecolo. 2009, 33 (4):  748-754.  doi:10.3773/j.issn.1005-264x.2009.04.013
    Abstract ( 2472 )   PDF (1392KB) ( 1149 )   Save
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    Aims Linking spatial patterns to ecological processes is a central topic in ecology. Inter-specific relationships in arid plant communities have been extensively studied by investigating aboveground patterns, but research on underground distribution patterns is inadequate. Our objective was to explore the inter-specific relationships between two dominant species, Achnatherum splendens (grass) and Sophora alopecuroides (forb), in a typical grass-forb community of arid/semi-arid regions of China.
    Methods We selected a 30 m × 30 m plot in a representative A. splendens-S. alopecuroides community in Sand Lake, Ningxia Hui Autonomous Region, Northwest China. The two dominant species usually spatially assemble as clumps aboveground. We partitioned the spatial gradient from the base of the assemblages to the non-vegetated open spaces between assemblages into under-canopy, transitional and open subareas to characterize the horizontal differences of microhabitat. Five assemblages of the two species were randomly chosen, and a 150 cm deep soil profile with coverage of 100 cm ×100 cm was excavated in each subarea. Root biomass in terms of fine roots (diameter < 2 mm) and coarse roots (diameter ≥ 2 mm) of the two species was investigated at soil depths of 0–10, 10–30, 30–60, 60–100 and 100–150 cm.
    Important findings Horizontally, biomass density of the total roots of A. splendens decreased along the gradient from under-canopy to open subareas. Also, ANOVA showed that biomass density of the total roots significantly differed among the three subareas for A. splendens, but no significant differences were detected for S. alopecuroides. Vertically, the soil layers with the highest biomass density of the total and fine roots of A. splendens increased in depth from under-canopy to open subareas, while that of the total roots of S. alopecuroides remained at 10–30 cm depth and that of the fine roots of S. alopecuroides tended to decrease in depth along the gradient. Also, the fine roots of the two species were different in the highest biomass density layer in the under-canopy subareas where root systems were densely distributed, but showed similar vertical patterns in the transition and open subareas. Niche separation in the under-canopy subareas and discrepancy in horizontal patterns of the two dominant species could represent an important adaptive strategy of avoiding direct competition and facilitating coexistence in arid communities.
    HUANG Gang, ZHAO Xue-Yong, HUANG Ying-Xin, LI Yu-Lin, SU Yan-Gui
    Chin J Plan Ecolo. 2009, 33 (4):  755-763.  doi:10.3773/j.issn.1005-264x.2009.04.014
    Abstract ( 2227 )   PDF (465KB) ( 1034 )   Save
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    Aims Although the availability of soil resources is related to fine root longevity, contradictory conclusions regarding the relationship might be clarified by comparing fine root longevity of the same species living in different habitats with contrasting soil resource availabilities. Our objectives were to 1) compare fine root longevity of Artemisia halodendron in mobile and fixed sandy lands and analyze the effects of soil resource availability on fine root longevity, 2) determine the patterns of fine root longevity in different soil depths, and 3) analyze seasonality of fine root longevity.
    Methods We established three plots in mobile and fixed sand lands and installed two tubes (clear plexiglass, 1 m long and 5 cm inner diameter) in each plot in April 2007. Images were taken at intervals of 20–30 d for each tube during July 13-September 10, 2007 and April 20-August 10, 2008. We recorded the length and width of new roots present on the minirhizotron screen and monitored them until they disappeared. Root survival time was defined as the period from appearance to disappearance. The proportion of roots surviving as a function of their age was described by the Kaplan-Meier survival function. Log-rank test was used to determine differences in fine root longevity between mobile and fixed sandy lands, two soil depths and appearance month.
    Important findings Cumulative survival rate of fine roots in mobile sandy land was higher than fixed sandy land in each observation time, with median root longevity (MRL) of 47 days in mobile sandy land and 35 d in fixed sandy land. MRL had significant negative relationships with soil total nitrogen content and soil bulk density, and a positive relationship with soil volumetric water content. Multiple regression analysis indicated soil water content was the key factor influencing fine root longevity. MRL of deep soil layer (30–50 cm) was significantly longer than shallow soil layer (10–30 cm) in both habitats. The two habitats had similar seasonal patterns of fine root longevity. The lifespan of fine roots in spring (70 d) was longer than autumn (61 d), and it was shortest in summer (39 d) due to high temperature and drought. These results suggested variations of soil water content play an important role in fine root longevity.
    XUN Jun-Jie, LI Jun-Ying, CHEN Jian-Wen, SHI Jian-Wei, WANG Meng-Ben
    Chin J Plan Ecolo. 2009, 33 (4):  764-771.  doi:10.3773/j.issn.1005-264x.2009.04.015
    Abstract ( 2220 )   PDF (964KB) ( 1357 )   Save
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    Aims Fine root growth dynamics is a key aspect of the functions of forest ecosystems. Our objective was to analyze the seasonal growth pattern of fine root standing length of Caragana korshinskii, an important shrub species in the Loess Plateau, China.
    Methods We used the minirhizotron technique to investigate fine root growth dynamics of C. korshinskii in a 5-year old plantation in the Loess Plateau area, Northwest Shanxi and, based on data of root length density (RLD, mm·cm–3) from May to September 2007, analyzed relationships of fine root standing length (RLDst, mm·cm–3) with environment factors such as ≥10 ℃ accumulated air temperature, accumulated soil temperature, accumulated precipitation and soil water content.
    Important findings The 40–90 cm soil layer was the main area of growth and distribution of fine roots, accounting for 59.7% of the total. From May to early September, RLDst increased gradually, followed by a slight decrease in late September. The seasonal growth pattern of fine roots was closely related to ≥10 ℃ accumulated air temperature, accumulated soil temperature and accumulated precipitation.
    YE Zi-Piao, YU Qiang
    Chin J Plan Ecolo. 2009, 33 (4):  772-782.  doi:10.3773/j.issn.1005-264x.2009.04.016
    Abstract ( 2916 )   PDF (1282KB) ( 1684 )   Save
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    Aims The stomatal conductance model of Ball-Berry and its subsequent refinements is an important tool to evaluate performance of stomatal regulation of plant leaves. Our objective was to derive the mechanism model of stomatal conductance and provide a theoretical basis for these empirical models of stomatal conductance.
    Methods By means of the diffusion and collision theory of CO2 gas in physics, hydromechanics and plant physiology, we derived a relationship between stomatal conductance of leaves, net photosynthetic rate and intercellular CO2 concentration. We measured the light-response of photosynthetic rate and stomatal conductance of Triticum aestivum under different chamber CO2 concentrations and different air temperatures in North China Plain using a gas analyzer Li-6400. The measured data of stomatal conductance of T. aestivum to irradiance in North China Plain were simulated by coupling the mechanism model of stomatal conductance and non-rectangular hyperbola model, rectangular hyperbola model and modified model of light-response of photosynthesis.
    Important findings A mechanism model of stomatal conductance was derived without additional hypotheses. It determined that the Ball-Berry stomatal conductance model had sound theoretical basis despite the model having deficiencies. The mechanism model shows advantages over the Ball-Berry model and model of Tuzet et al. for T. aestivum. If the mechanism model of stomatal conductance is coupled with a modified model of light-response of photosynthesis, the coupled model could simulate well the light-response data of stomatal conductance of T. aestivum. The fitted results show that stomatal conductance of T. aestivum to irradiance increases with light intensity until saturation light intensity, and then decreases with light intensity. The saturation light intensity and maximum stomatal conductance of T. aestivum can be calculated directly by the coupled model. Furthermore, we can use the coupled model to study whether maximum stomatal conductance coincides with maximum net photosynthetic rate. The fitted results also show that the maximum stomatal conductance and the maximum net photosynthetic rate are not synchronous at 30 °C and 560 μmol·mol–1 CO2 or 32 °C and 370 μmol·mol–1 CO2. Additionally, the coupled model can describe not only part of the light-response curve of stomatal conductance below light saturation, but also the range of levels above the saturation light intensity under different environmental conditions.
    ZHAO Xin, SONG Rui-Qing, YAN Xiu-Feng
    Chin J Plan Ecolo. 2009, 33 (4):  783-790.  doi:10.3773/j.issn.1005-264x.2009.04.017
    Abstract ( 2354 )   PDF (424KB) ( 1509 )   Save
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    Aims Camptotheca acuminata is a Chinese tree that produces camptothecin (CPT), a monoterpenoid indole alkaloid that inhibits tumor cells. Our purpose was to determine effects of arbuscular mycorrhizal (AM) fungi on the growth and photosynthesis of C. acuminata seedlings.
    Methods Potted seedlings were inoculated with one of six AM fungi (Glomus manihot, G. versiforme, G. diaphanum, Acaulospora mellea, A. laevis and Sclerocystis sinuosa) and grown under greenhouse conditions.
    Important findings All seedling roots were colonized by the six AM fungi and formed typical mycorrhizal structures. Except the G. versiforme inoculated seedlings, the biomass of mycorrhizal seedlings was significantly higher than non-mycorrhizal (CK) seedlings. Moreover, biomass of A. mellea, S. sinuosa and G. diaphanum inoculated seedlings reached 1.6, 1.4 and 1.3 times that of CK, respectively. Compared with non-mycorrhizal seedlings, the net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) of A. mellea inoculated seedlings were significantly increased, while the intercellular CO2 concentration (Ci) and stomatal limitation value (Ls) of mycorrhizal seedling leaves did not change significantly. The chlorophyll a content, total chlorophyll content, chlorophyll a/b value and carotenoid content of G. diaphanum, A. mellea, A. laevis and S. sinuosa inoculated seedlings were significantly higher than that of CK, as was the chlorophyll b content of G. manihot and S. sinuosa inoculated seedlings. Effects of AM fungal inoculation on the parameters of chlorophyll fluorescence of Camptotheca acuminata seedlings were small. Only the maximal photochemical efficiency of PSII in the dark (Fv/Fm) of G. diaphanum inoculated seedlings was significantly higher than that of CK. For G. manihot and S. sinuosa inoculated seedlings, the effective quantum yield (EQR) was higher than that of the non-mycorrhizal seedlings. The photochemical quenching (qP) of S. sinuosa inoculated seedlings was higher and the non-photochemical quenching (NPQ) was lower than in non-mycorrhizal seedlings.
    TIAN Yong-Chao, YANG Jie, YAO Xia, ZHU Yan, CAO Wei-Xing
    Chin J Plan Ecolo. 2009, 33 (4):  791-801.  doi:10.3773/j.issn.1005-264x.2009.04.018
    Abstract ( 2408 )   PDF (1015KB) ( 1237 )   Save
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    Aims Quantifying the relationship between red edge area parameter and canopy leaf nitrogen status is the foundation for real-time and non-destructive monitoring of crop growth status and precision nitrogen fertilization in rice (Oryza sativa). Our objectives were to analyze 1) characteristics of the first-derivative reflectance spectra in red edge area and 2) the quantitative relationship of red edge area shape parameters to canopy leaf nitrogen concentrations, using different nitrogen levels and rice varieties and based on canopy hyper-spectral reflectance of field-grown rice in different years.
    Methods Spectrum in the red edge area was significantly affected by different nitrogen levels and different rice varieties, and a “three-peak” feature could be observed with the first derivative spectrum at about 700, 720 and 730 nm. The maximum heights of the three peak bands changed with different nitrogen levels, so sub-areas surrounded by the first derivative spectra curve and x coordinate were formed by dividing the red edge area with the “three-peak band line”. Two random sub-areas were selected to calculate ratio (double peak symmetry, DPS) and normalization (normalized double peak symmetry, NDPS), which were related to canopy leaf nitrogen concentrations.
    Important findings DPS based on the ratio of two different red edge sub-areas, and NDPS with normalization of the two different red edge sub-areas were significantly related to leaf canopy nitrogen concentrations in rice. Results of model calibration and validation indicated that DPS (A675-700, A675-755) and NDPS (A675-700, A675-755), ratio and normalized difference of areas in 675–700 to 675–755 nm red edge region, respectively, performed the best in estimating leaf canopy nitrogen concentration. Thus, these two spectral indices were suitable red edge area shape parameters for monitoring leaf canopy nitrogen concentrations in rice.
    ZHANG Tao, AN Li-Zhe, CHEN Tuo, DAI Chun-Yan, CHEN Nian-Lai
    Chin J Plan Ecolo. 2009, 33 (4):  802-811.  doi:10.3773/j.issn.1005-264x.2009.04.019
    Abstract ( 2268 )   PDF (591KB) ( 1084 )   Save
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    Aims The antioxidative defense capacity of plants plays an important role in extreme environments. We investigated the antioxidative system in Picea crassifolia and Sabina przewalskii leaves along an altitudinal gradient in Sidalong forests of Qilian Mountains to study the response of antioxidative systems in evergreen xylophytes to subalpine environment.
    Methods We determined the contents of malonaldehyde (MDA), praline (Pro), ascorbic acid (AsA) and glutathione (GSH), as well as the activities of superoxide dismutase (SOD) , peroxidase (POD) , catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) in leaves of P. crassifolia and S. przewalskii from different altitudes (2 665–3 365 m).
    Important findings The MDA contents in P. crassifolia and S. przewalskii leaves positively and significantly correlated with altitude. At the same altitude, the MDA content in S. przewalskii leaves was significantly higher than that in P. crassifolia leaves. With increasing altitude, the content of Pro, AsA and GSH and the activities of SOD, POD, CAT, APX and GR in leaves of both P. crassifolia and S. przewalskii increased. The sensitivity of AsA, GSH and Pro in S. przewalskii leaves along the altitudinal gradient was higher than those in P. crassifolia, although the AsA content was lower than the later. Those results suggested that S. przewalskii suffered greater oxidative stress than P. crassifolia, but its capacity to cavenge O2–· was similar. POD was a main enzyme in S. przewalskii as decomposing H2O2, but P. crassifolia was CAT, APX and GR. The action of AsA-GSH circulatory system in P. crassifolia was greater than that in S. przewalskii, and Pro was the most important antioxidant substance in S. przewalskii.
    FENG Yuan-Jiao, WANG Jian-Wu, LUO Shi-Ming
    Chin J Plan Ecolo. 2009, 33 (4):  812-823.  doi:10.3773/j.issn.1005-264x.2009.04.020
    Abstract ( 2115 )   PDF (1092KB) ( 1432 )   Save
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    Aims Our objectives were to investigate temporal dynamics of the contents of direct defense chemicals (DIMBOA and total phenolics) and the expression levels of their corresponding key genes (Bx1, Bx9 and PAL), direct defense protein-related genes (PR-1, PR-2a and MPI), and indirect defense chemical volatile-related genes (FPS and TPS) in leaves and root systems of Zea mays seedlings under the application of exogenous jasmonic acid (JA) on leaf surface.
    Methods Leaves of Z. mays cultivar Gaoyou 115 were treated with JA with concentrations of 1, 2.5, 5 and 10 mmol·L–1. We examined contents of the defense chemicals and expression dynamics of their synthesis-mediated genes, direct defense protein-related genes and indirect defense chemical volatile-related genes in both leaves and roots from 3 to 48 h after the application.
    Important findings Exogenous JA application resulted in significant timing and concentration effects on the chemical defense response. Gene expression of Bx9 and PAL in the leaves could be induced 3 to 6 h after treatment, resulting in an apparent increase in the content of DIMBOA and total phenolics. The increase was positively correlated with JA concentrations, but the inductive effect gradually decreased afterward. Gene expression of PR-2a and MPI in the leaves was also dramatically induced by JA up to 24 and 48 h, respectively. High JA concentrations induced the expression of FPS gene, whereas low JA concentrations had inducible effects on the expression of TPS after 3–6 h. In addition, JA treatment to leaves could indirectly induce the defense response in roots. Most parameters measured in the indirect induction mainly occurred in the later phase (after 24–48 h) of the treatment. For example, JA systematically increased the contents of DIMBOA and total phenolics in the roots and enhanced the expression of PR-2a, MPI, FPS and TPS genes in the roots 48 h after the treatment, showing a tendency of positive relationship with JA concentrations. These findings provided evidence that the indirect induction by JA application to Z. mays leaves on roots was not as strong as on leaves. Leaves started the defense response earlier than roots, and the induction of defense response both in leaves and roots was increased with increasing JA concentrations.
    YANG Qi-Liang, ZHANG Fu-Cang, LIU Xiao-Gang, YANG Zhen-Yu
    Chin J Plan Ecolo. 2009, 33 (4):  824-832.  doi:10.3773/j.issn.1005-264x.2009.04.021
    Abstract ( 2306 )   PDF (454KB) ( 1066 )   Save
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    Aims Hydraulic conductance, which is characterized by root water uptake and xylem water transport efficiency, is a physiological response of plants to different environmental factors, such as salt-stress and water deficit. However, there is little research on relationships between different drip irrigation modes and hydraulic conductance. Our objectives were to determine 1) the impact on growth and hydraulic conductance of different drip irrigation modes and salinity treatments and 2) the relationship between apple seedling growth and hydraulic conductance.
    Methods The experiment used a NaCl concentration gradient of 0 (CK), 0.2% (S1), 0.3% (S2) and 0.4% (S3) and three drip irrigation modes: alternate partial root zone drip irrigation (ADI, alternate watering on both sides of the root zone), fixed partial root zone drip irrigation (FDI, fixed watering on one side of the root zone) and conventional drip irrigation (CDI, simultaneous watering on both sides of the root-zone).
    Important findings Drip irrigation modes and NaCl concentration significantly affect apple seedling growth and hydraulic conductance. Dry matter, leaf area, net growth and hydraulic conductance of apple seedlings were significantly inversely related to NaCl concentration under the same drip irrigation treatment. Root hydraulic conductance (Kr) was significantly linearly correlated with total root dry weight, shoot hydraulic conductance (Ksh) and shoot dry weight. Under the same NaCl concentration treatment and compared with CDI, ADI had a water savings of up to 50%, but average root dry weight, shoot dry weight, total dry weight, leaf area, plant net growth and root hydraulic conductance of ADI only decreased by 8.7%, 19.24%, 13.47%, 11.87%, 32.96% and 10.72%, respectively, showing that ADI has an obvious promoting effect on apple seedling growth and hydraulic conductance. Compared with CDI, high NaCl concentrations S2 and S3 led to decreases in Kl+p of ADI of 33.56% and 44.26%, respectively, while the Kr of ADI treatment increased by 1.13% and 10.91%, respectively, indicating that the root hydraulic signal transmission efficiency of ADI treated seedlings, the ability of seedlings to regulate water balance and resistance stability to salt-stress could be enhanced. The growth and hydraulic conductance of ADI were all higher than FDI. Use of ADI not only improved water-saving regulation ability, but also strengthened resistance stability to salt-stress.

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