• Volume 28,Issue 3,2008 Table of Contents
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    • Response of carbon and nitrogen content in plants and soils to vegetation cover change in alpine Kobresia meadow of the source region of Lantsang, Yellow and Yangtze Rivers

      2008, 28(3):885-894. DOI: 10.1016/S1872-2032(08)60031-1

      Abstract (327) HTML (0) PDF 230.51 K (433) Comment (0) Favorites

      Abstract:We conducted this study in lightly and severely degraded Kobresia pygmaea meadow in Gande County, Qinghai Province of China. The purpose of this research was to compare carbon and nitrogen concentrations, content and dynamics of aboveground tissue, belowground roots and soil (0-40 cm) between lightly and severely degraded Kobresia meadow. The results showed that C and N concentrations and C:N ratio of the aboveground tissue were significantly higher in lightly degraded grassland than in severely degraded grassland. In addition, total carbon and nitrogen concentrations of the aboveground tissue were ranked in order of forbs > grasses > sedges in the same grassland type. Total carbon and nitrogen concentrations of belowground roots were significantly higher in severely degraded grassland than in lightly degraded grassland. Total carbon and nitrogen concentrations were higher in the aboveground tissue than in the belowground roots. Total soil organic carbon concentration in severely degraded grassland was significantly lower than that in lightly degraded grassland, and decreased with depth. C and N content per unit area was ranked in order of 0-40 cm soil depth > belowground roots > aboveground issue in the same grassland type. The total carbon content per unit area of aboveground tissue, roots and 0-40 cm soil depth declined by 7.60% after degradation from lightly (14669.2 g m-2) to severely degraded grassland (13554.3 g m-2), i.e., 0-40 cm soil depth declined by 4.10%, belowground roots declined by 59.97% and aboveground tissue declined by 15.39%. The nitrogen content per unit area of aboveground tissue, roots and 0-40 cm soil depth increased after degradation by 12.76% from lightly (3352.7 g m-2) to severely degraded grassland (3780.6 g m-2), i.e., 0-40 cm soil depth increased by 13.07%, belowground roots declined by 55.09% and aboveground tissue declined by 16.00%. As a result of grassland degradation, the total carbon lost by 11149 kg hm-2, and the total nitrogen increased by 4278 kg hm-2.

    • Analysis on Jinghe watershed vegetation dynamics and evaluation on its relation with precipitation

      2008, 28(3):925-938. DOI: 10.1016/S1872-2032(08)60032-3

      Abstract (304) HTML (0) PDF 590.96 K (842) Comment (0) Favorites

      Abstract:Vegetation degradation is one of the key subjects in the study of global environmental changes, and the Normalized Difference Vegetation Index (NDVI) is generally recognized as a good indicator of terrestrial vegetation productivity and growth status. To evaluate the vegetation dynamic changes in the Jinghe watershed on Loess plateau from 1982 to 2003, major methods of change slope, principal component analysis and correlation analysis were employed with 8 km resolution NOAA-NDVI time series data. Based on these analyses, the relationship between precipitation and NDVI was discussed. Results show that there has been little change in both amplitude and variety of NDVI during the past 22 years. Vegetation in the upper stream areas, typically the watershed marginal mountain areas, changes significantly. A trend analysis shows that the similar finding on vegetation dynamics in different areas tends to be induced by climate changes and human land use transformation. A standardized principal component analysis indicates that the first two components, PC1 and PC2, are closely related to vegetation and climate changes, while PC3 and PC4 are connected with floodwater in flooding seasons, and PC5 and PC6 reflect the effects of human activities. Finally, the correlation analysis shows that there is a close positive relationship in this region between NDVI and precipitation. The rainfall sensitivity threshold reaches 550 mm or even higher.

    • Influence of nematodes and earthworms on the emissions of soil trace gases (CO2, N2O)

      2008, 28(3):993-999. DOI: 10.1016/S1872-2032(08)60033-5

      Abstract (119) HTML (0) PDF 147.11 K (32) Comment (0) Favorites

      Abstract:To determine effects of soil fauna on greenhouse gas emissions, soil inoculated with different populations of nematodes and earthworms was incubated for 15 d. Soil with greater populations of nematodes and earthworms enhanced CO2 and N2O emissions. Cumulative emission fluxes of the two gases in the treatment of greater populations of nematodes and the treatment of greater populations of nematodes and earthworms were increased by 4.3 and 5.2 times for CO2, 1.8 and 2.7 times for N2O, respectively in comparison of the nematode-killed treatment. The emission fluxes of CO2 and N2O in soil treated with greater populations of nematodes were 19% for CO2 and 21% for N2O higher than those in soil treated with lower populations of nematodes. Meanwhile, the emission fluxes of the two gases in soil treated with greater populations of nematodes and earthworms were 12% for CO2 and 27% for N2O higher than those in soil treated with lower populations of nematodes and earthworms. The two gas fluxes were significantly correlated (R2 = 0.9414; p < 0.001). Cumulative emissions of CO2 and N2O from soil treated with different populations of nematodes were positively correlated with DOC (dissolved organic carbon) concentration measured at the start of gas sampling (p < 0.05).

    • Effects of a rainwater-harvesting furrow/ridge system on spring corn productivity under simulated rainfalls

      2008, 28(3):1006-1015. DOI: 10.1016/S1872-2032&#40;08&#41;60034-7

      Abstract (323) HTML (0) PDF 344.30 K (1624) Comment (0) Favorites

      Abstract:A field experiment was conducted to determine the effects of a rainwater-harvesting furrow/ridge system (RHFRS) on water use efficiency (WUE) and grain yield of spring com in different simulated rainfall treatments. Our results showed that when rainfall supply ranged between 230 and 440 mm, the rainwater-harvesting furrow/ridge system increased surface temperature by 0.7–1°C at the depth of 10 cm and increased soil water storage by 5%–12% in the soil layer of 0–120 cm compared with the control. Emergence was also more rapid in the furrow-ridge system. Spring corn yield in the rainwater-harvesting furrow/ridge system was 83% higher in the 230 mm rainfall treatment, 43% higher in the 340 mm rainfall treatment, and 11% higher in the 440 mm rainfall treatment compared with the control. Similarly, WUE was 77% higher in the 230 mm rainfall treatment, 43% higher in the 340 mm treatment, and 10% higher in the 440 mm treatment than those of the control under the corresponding rainfalls. In summary, results from this study indicate that 440 mm rainfall during the spring corn growing season is the upper limit for which the rainwater-harvesting furrow/ridge system should be adopted.+

    • Sex-linked photosynthetic physiologic research and the evolutionary ecological analysis in living fossil plant, Ginkgo biloba L.

      2008, 28(3):1128-1136. DOI: 10.1016/S1872-2032&#40;08&#41;60035-9

      Abstract (642) HTML (0) PDF 289.37 K (844) Comment (0) Favorites

      Abstract:Ginkgo is an ancient dioecious plant. At present, only Ginkgo biloba L. still exists as a living fossil plant. Botanists have studied it from different aspects in the world due to its unique characteristics. Plant sex physiological ecology is still a knowledge gap in plant ecology. This article measured the photosynthetic traits of adult male and female ginkgoes which grew in suitable environment condition. The result indicated that male and female ginkgoes had similar response to light. The light saturate points (LSP), light compensate point (LCP) and dark respiration rate (Rd) between male and female were also of insignificant differences. However, the net photosynthetic rate (Pn) of female ginkgo was significantly higher than male. From the view of evolution and through comparison with other gymnosperms and angiosperms, the photosynthetic capacity of ginkgo is not obviously lower than that of other plants. It gave us a clue that the photosynthetic capacity was not the direct reason, which restricted the distribution of ginkgo in the Tertiary.

    • Microbial diversity in surface sediments of the Xisha Trough, the South China Sea

      2008, 28(3):1166-1173. DOI: 10.1016/S1872-2032&#40;08&#41;60036-0

      Abstract (535) HTML (0) PDF 334.96 K (368) Comment (0) Favorites

      Abstract:Microbial communities were obtained from the surface sediments of the Xisha Trough using the culture-independent technique. The characteristics of the 16S rDNA gene amplified from the sediments indicated that archaeal clones could be grouped into Euryarchaeota and Crenarchaeota, respectively. Two archaeal groups, Marine Crenarchaeotic GroupI and Terrestrial Miscellaneous Euryarchaeotal Group, were the most dominant archaeal 16S rDNA gene components in the sediments. The remaining components were related to the members of Marine Benthic Group B, Marine Benthic Group A, Marine Benthic Group D, Novel Euryarchaeotic Group and C3. The bacterial clones exhibited greater diversity than the archaeal clones with the 16S rDNA gene sequences from the members of Proteobacteria, Planctomycetes, Actinobacteria, Firmicutes, Chloroflexi, Acidobacteria, candidate division OP8, Bacterioidetes/Chlorobi and Verrucomicrobia. Most of these lineages represented uncultured microorganisms. The result suggests that a vast amount of microbial resource in the surface sediments of the South China Sea has not been known.

    • Biomass size spectra of net plankton in the adjacent area near the Yangtze River Estuary in spring

      2008, 28(3):1174-1182. DOI: 10.1016/S1872-2032&#40;08&#41;60037-2

      Abstract (192) HTML (0) PDF 471.21 K (689) Comment (0) Favorites

      Abstract:Based on data from survey carried out in spring 2005, the biomass size spectra of net plankton were explored in the adjacent sea of Yangtze River Estuary. Results revealed an approximately continuous size distribution of plankton individuals, from phytoplankton (5–250 μm cell-1 in equivalent sphere diameter (ESD), 15 pg–146 ng C cell-1) to zooplankton (120 μm–2 cm ESD, 115 ng–7.5 mg C ind-1). The normalized spectra (carbon scale) were linear with slope ranged from –0.889 to –0.445, and intercept ranged from 12.866 to 16.863 (all stations together, slope = –0.606, intercept = 19.448), indicating strong deviations from the ideal value (slope = –1.22) of a steady pelagic ecosystem. Correlation analysis presented that intercept and regression coefficient of net plankton size spectra had significant relationship with plankton biomass size diversity.

    • Selection of benthic macroinvertebrate-based multimetrics and preliminary establishment of biocriteria for the bioassessment of the water quality of Taihu Lake, China

      2008, 28(3):1192-1200. DOI: 10.1016/S1872-2032&#40;08&#41;60038-4

      Abstract (223) HTML (0) PDF 169.73 K (591) Comment (0) Favorites

      Abstract:To develop benthic macroinvertebrate-based multimetrics for the bioassessment of the water quality of Taihu Lake, benthic macroinvertebrate assemblages were sampled at 60 sites in 8 subareas of Taihu Lake. A total of 24 species of benthic macroinvertebrates were obtained: 14 species of Mollusca, 5 species of Arthropoda and 5 species of Annelida. A comprehensive evaluation of the metrics was carried out. The results showed that 7 metrics (i.e., total number of taxa, the number of Mollusca & Crustacea taxa, % Mollusca & Crustacea, % Gastropoda, Goodnight-Whitley index, Hilsenhoff biotic index and % Collector-gatherers) were sensitive. A score of 5, 3 or 1 was assigned to every metric for standardization of the metrics, and a multimetric on a scale ranging from 7 to 35 for bioassessment was developed. Four-level discriminatory biocriteria for water quality were eventually proposed by quartation: 7–14, very poor; 15–21, poor; 22–28, fair; 29–35, good. The re-scored results from the 60 sites showed that the water quality of southeastern Taihu Lake was relatively good, whereas that of northwestern Taihu Lake was relatively poor. Basically, the discriminatory biocriteria are suitable for the assessment of the water quality of Taihu Lake.

    • Behavioral mechanisms of parasitic wasps for searching concealed insect hosts

      2008, 28(3):1257-1269. DOI: 10.1016/S1872-2032&#40;08&#41;60039-6

      Abstract (278) HTML (0) PDF 162.30 K (1912) Comment (0) Favorites

      Abstract:Wood borers are important forest insect pests and difficult to be controlled owing to their concealed behavior. However, parasitic wasps can effectively ascertain and parasitize wood borers as well as other concealed pests by using special searching, finding and attacking mechanisms, which have been developed during the course of long-term coevolution with their hosts. The present paper summarizes the behavioral mechanisms of parasitic wasps involved in searching and locating their concealed hosts. Parasitic wasps can accurately find the location of their hidden hosts and then parasitize them, usually by using olfactory semiochemicals from hosts (lavare and adults), host frass and symbiotic microorganisms in host galleries; visual signals from color contrast of plant surface; contact stimuli from characters of host physical defense; substrate vibrations produced by host feeding and movement; infrared radiation from host activities and metabolizability. Some parasitic wasps may integrate the information of several stimuli from different sources to enhance the reliability and accuracy of host locations. In addition, the potentials for utilizing the host location signals of parasitoids in biological control are discussed.

Editor in chief:冯宗炜


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Unified domestic issue:CN

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