Dec 2008, Volume 3 Issue 4
    

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  • CHEN Zhenju, SUN Yu, HE Xingyuan, CHEN Wei, SHAO Xuemei, SHAO Xuemei, ZHANG Huayu, WANG Zhongyu, LIU Xiaoyu
    Taking Chinese pine in Qianshan Mountains as a sample, the tree ring width chronology including Standard, Residual, and Arstan chronologies was established. The results show that the tree ring width of Chinese pine is highly correlated with the temperatures from May to July and from September to November. Statistically significant positive correlations were observed between tree ring width and the extreme minimum temperatures in July and mean minimum temperatures in September. The chronology was significantly or very significantly correlated with extreme minimum temperatures in December and the following January, with mean minimum temperatures in January, with annual precipitation and with precipitation in April, May and the following December. The Chinese pine responded strongly to the monthly/yearly water vapor pressure and relative humidity. Annual and largely monthly evaporation in April–July had a negative effect on tree growth, and was particularly striking for evaporation in April–July. The narrow tree rings recorded by the chronology demonstrated the 30 occasions of extreme drought since 1800. The growth of Chinese pine in the Qianshan mountains were also affected by climate changes on a hemispheric and global scale. There were 11-, 23- and 50-year-common periodicities between the chronology and solar activity and 10-, 20- and 45-year-common periodicities between the chronology and geomagnetic activity.
  • WU Jiabing, GUAN Dexin, SHI Tingting, HAN Shijie, JIN Changjie, SUN Xiaomin
    Turbulent exchange of CO2 was measured continuously via the open-path eddy covariance technique over a broadleaf-Korean pine forest in Changbai Mountain, northeast China. The results show that with near-neutral atmospheric stratification, CO2 and vertical wind components measured over the forest canopy in the inertial sub-range followed the expected -2/3 power law. The dominant vertical eddy scale was about 100 m. The frequency ranges of eddy contributions to CO2 fluxes were mostly within 0.01–2.0 Hz. Large eddies with low frequency over the canopy contributed more to CO2 fluxes than small eddies. The open-path eddy covariance system could satisfy the estimation of turbulent fluxes over the canopy, but the CO2 fluxes between forest and atmosphere were generally underestimated at night because of the increment non-turbulent processes, suggesting that the CO2 fluxes estimated under weak turbulence need to be revised correspondingly.
  • LI Yide, XU Han, CHEN Dexiang, LUO Tushou, MO Jinhua, LUO Wen, CHEN Huangqiang, JIANG Zhongliang
    Twenty-three sample plots dominated by Vatica mangachapoi at various elevations in the tropical lowland rainforest in the Jianfengling National Nature Reserve of Hainan Island were established. The interspecific association among the 32 dominant species was analyzed and the division of ecological species groups and functional groups are discussed. The results showed that these dominant populations had an overall positive interspecific association. The species pairs with significant, positive association accounted for only about 10% of the total 496 species pairs. Most of the other species pairs showed weak association or non-association, i.e., the dominant populations investigated had relatively independent distributions. The 32 dominant species were divided into four ecological species groups and ten functional groups according to their interspecific association coefficients, based on a cluster analysis of the species. Recognition characteristics of the ten functional groups are proposed.
  • SANG Weiguo, CHEN Sha, LI Guangqi
    Deciduous broad-leaved forests (DBF), Larix principis-rupprechtii (LF) and Pinus tabulaeformis plantations (PF) are three typical forest communities in the warm temperate zone of the Dongling Mountains. In this study, we used an indirect method, hemispheric photography, to measure and analyze the dynamics of leaf area index (LAI) and canopy openness of the three forest communities. The results show that the LAI values of DBF and LF increased gradually with plant growth and development. The highest LAI value appeared in August, while canopy openness changed inversely with LAI. The lowest value appeared in November. DBF maintained a higher LAI in August and had a more open canopy in November compared with LF. For PF, we observed little changes in the LAI and canopy openness which was attributed to the leaf retention of this evergreen species. However, a similar relation between LAI and canopy openness was found for the three forest communities: canopy openness varied inversely with LAI. The relation is exponential and significant. Therefore, canopy openness is a good indicator of LAI in forests. This result can be used to test the validity of the LAI based on remote sensing and to provide a reference for the study of the canopy heterogeneity and its effect. This also benefits modeling for fluxes of carbon, water and energy from the level of the stand to landscape.
  • ZHU Jiaojun, YAN Qiaoling, MAO Zhihong, ZHANG Caihong, LIU Zugen
    The effects of thinning on plant species diversity and composition of understory herbs in a larch plantation were investigated. The relationships between plant species diversity and composition of understory herbs and light conditions were established. Twenty-five 1 m × 1 m plots and fifteen 13 m × 1 m transects were set up in unthinned and thinned stands, respectively. All the transects in the thinned stands were set across the thinned rows and unthinned rows, and each of them was divided into nine 1 m × 1 m sub-plots. The herb diversity and light conditions were observed in each plot and sub-plot. The results show that there was a significant difference in herb diversity between the thinned and unthinned stands. All biodiversity indices except for evenness index in the thinned stand were higher than those of the unthinned stand, i.e., the herb diversity increased after thinning. According to the changes in herb densities and whether one species could be found in a stand or not before and after thinning, all herb species were classed into three types: positive, neutral and negative species, which referred to a species newly appeared and having an obviously increased density after thinning, with no obvious changes in its appearance and density after thinning, and disappeared and having an obviously decreased density after thinning, respectively. Many new species were found in the thinned stand like Corydalis pallida, Prenanthes tatarinowii, Vicia unijuga and Sonchus brachyotus etc. However, most species found in both the thinned and unthinned stands were negative species. In all nine sub-plots, only 11 and 10 species were found in spring and in autumn respectively, accounting for 17.74% and 15.15% of all the species in the thinned stand, respectively. All biodiversity indices were the highest in the center sub-plots and most of them tended to reduce from middle to side sub-plots. There was a close correlation between most of the three types of species and light conditions which was similar to each other in the thinned and unthinned stands.
  • SI Jianhua, FENG Qi, LI Jianlin, ZHAO Jian
    The soil-plant system is a very important subsystem of the soil-plant-atmosphere continuum (SPAC). The water uptake by plant roots is an important subject in the research on water transport in this SPAC and is also the most active study direction in the fields of ecology, hydrology and environment. The study of the spatial distribution pattern of fine roots of plants is the basis of constructing a water absorption model of plant roots. Our study on the spatial distribution pattern of fine roots of Populus euphratica in a desert riparian forest shows that the density distribution of its root lengths can be expressed horizontally as a parabola. The fine roots are concentrated within the range of 0–350 cm from the tree trunk and their amount accounts for 91.9% of the total root mass within the space of 0–500 cm. In the vertical direction, the density distribution of the fine root lengths shows a negative exponential relation with soil depth. The fine roots are concentrated in the 0–80 cm soil layer, accounting for 96.8% of the total root mass in the 0–140 cm soil layer.
  • HOU Ruiping, LI Rui, LIU Yunfang, ZHANG Kebin
    The edge effect of plant communities was investigated in a wetland-dry grassland ecosystem at the Siertan Wetland in Yanchi County, Ningxia Hui Autonomous Region, China. Four transects lines, with each about 1 km long, were established for a vegetation survey in July 2005, along biotope gradients in four directions: east, northeast, west and northwest. The data was analyzed using TWINSPAN classification method. The vegetation in this wetland was classified into three vegetation types: halophytic marsh vegetation, meadow vegetation and grassland vegetation. Based on the calculation of the community structure indices, the edge effect was studied which revealed distinct differences among those three vegetation zones along each transect line. The ecotone had high richness indices (R), a high diversity index (SW) and ecological dominance (SP). Evenness, as measured by the index (E), was less apparent. From the four transect lines, it appears that the ecotone in the northeasterly direction scored higher in each community structure indicator than any of the other directions and those towards the northwest were least. The variation in the edge effect between the different transect lines is caused by human disturbances and topographic uplift.
  • LIU Jiaomei, LI Shuhua, ZHANG Zhiguo
    We studied the ecological benefits of four types of urban green spaces (lawn, a Robinia pseudoacacia stand, a Pinus tabulaeformis stand and a mixed stand of both species) in Yuan Dynasty Wall Relics Park, Beijing. Each of the eight sampling sites was about 0.1 hm2. The experiment was carried out in June, 2006 over a period of eight consecutive days, during which we continuously measured air temperature, relative humidity (RH) and wind speed at the four green spaces in both horizontal and vertical directions. The results were as follows: in the horizontal direction, the all-day average temperature at the pine stand was the lowest and its RH was the highest under three different climate conditions. During the daytime high temperature period, the temperature of the lawn was the highest and its RH the lowest. The temperature was lowest for the mixed stand, and the RH was highest for the pine stand. The highest average daily temperature occurred in the locust stand. The temperature and RH of the four green spaces were statistically different at the 0.05 level of significance. In the vertical direction, the average daily temperature of the four green spaces increased with height. The average daily RH of the four green spaces decreased slightly with increased height. During the high temperature period of the day, the average temperature of the lawn and the P. tabulaeformis stand declined with the increased height, but the temperature at the R. pseudoacacia stand and the mixed P. tabulaeformis–R. pseudoacacia stand fluctuated greatly. With regard to the effect of lowering the wind speed, the mixed stand was better than the other green spaces. Based on these results, it can be concluded that the mixed Chinese pine and locust stand was the best choice for the establishment of urban green spaces.
  • LI Weicheng, SHENG Haiyan
    Anthriscus sylvestris, a weed found both in Europe and China, is a kind of representative clustered clonal plant and is a foe on dams and banks. It has been widely investigated in Europe for its powerful progenitive ability and tolerance to severely adverse environments. Our aims were to investigate and quantify its spatial distribution patterns in four types of community habitats, using a clustering method and adjacency lattice established by Greig-Smith. We concluded our environmental interpretation based on canonical correspondence analysis (CCA) appended to a Monte Carlo test with randomized seeding. The results indicate that the buds around the parent roots are in an aggregation distribution pattern in all scales (0.002–5.12 m2), but theoretical distribution fitting, like negative binomial and Poisson distribution, show that some sizes of several sampling locations are out of place. For this, spatial ordination gives a satisfactory answer implying the effect of environmental variables such as depth of humus layer, soil moisture, light condition, disturbance intensity and herb abundance. CCA accounts for 64.7% of the total environmental variation and the remaining variation may be counteracted in those five variances or can be interpreted by other factors like accumulating temperature, annual rainfall and altitude in landscape scale. With the aid of temporal sequencing, the suppressed type II (monodominant) may be the former mode of suppressed type I (stable type), where invasion is done with the help of disturbance from both humans and nature. The abundance of A. sylvestris can add to our cognition in diversity resistance hypothesis and our hypothesis on disturbance before or upon immigration.
  • HAN Lu, WANG Haizhen, ZHOU Zhengli, LI Zhijun
    One 50 m × 50 m standard plot was sampled in a natural forest of Populus euphratica in Awati County, situated at the edge of the Tarim Basin, Xinjiang Uygur Autonomous Region, China. The field investigation was conducted with a contiguous grid quadrate method. By means of a test of variance/mean value ratio, aggregation intensity index and theoretical distribution models, the spatial distribution pattern and the dynamics of primary populations in P. euphratica forest were studied. The results showed that the spatial distribution pattern of two dominant arbor populations conformed to clumped distribution. The aggregation intensity of the P. euphratica population was higher than that of P. pruinosa population. The spatial distribution pattern of two companion plant populations in the shrub layer also conformed to clump type, though the aggregation intensity of Tamarix chinensis was higher. In the herb layer, the distribution patterns of Glycyrrhiza uralensis and Asparagus persicus conformed respectively to a clumped pattern and a random pattern. The results of a Taylor power method test and Iwao’s m*-Graphic
    YIN Zengfang, FAN Ruwen
    Observing changes in plasma components during the development of sieve-tube elements (SE) in secondary-phloem is very important in the study of their physiological function. We investigated the development of SE in the secondary-phloem of Populus deltoides with the aid of an electron microscope. The developmental process of SE in secondary-phloem can be divided into three stages: immature, mature and degenerated, based on the changes of plasma components and cell structures. The immature stage is the development period before the vacuole membrane was ruptured. The radial extension of cells, cell wall incrassation and generation of plastid sieve elements and P-protein occurred during this period. The mature stage started when the vacuole membrane was ruptured. Selective autolysis of protoplasmic components formed mature SEs, with the characteristics that the organelles, such as dissociative ribosome, Golgi body, endoplasmic reticulum and nuclei were disassembled quickly. Two distinctive ways of nuclear degeneration occur. One is an early degenerated nuclear membrane, with dispersed karyoplasms, joined by P-protein. The other is early agglomerated chromatin and subsequently degenerate karyotin with two clear layer structures in the nuclear membrane. One sign in the degenerated stage is the disassembled plasma membrane. During this stage, plastid membranes become disorganized, the starch grains are dispersed in the chamber of SE and the mitochondria dissembled. The callose appears synchronously in sieve plates and P-protein disaggregates. Opened sieve plates are then formed because of callose autolysis, after the protoplasm disappears completely. Finally, the physiological function of SE is lost.
  • MA Lei, WU Xiaoqin, ZHENG Ling
    In order to discover which ectomycorrhizal- (ECM) fungi have better growth-promoting effects on poplars, cuttings from four poplar species were inoculated with nine species of ECM fungi by three methods. We investigated the status of mycorrhizal formation and the effects of these fungi on the growth of the poplars. The results show that Xrocomus chrysentero (Xc), Boletus edulis (Be), Pisolithus tinctorius (Pt) and Laccaria amethystea (La) formed clear ectomycorrhizal symbiosis with the poplar seedlings. Among these four ECM fungi, Xc had the greatest ability to develop mycorrhizae with all four poplar species. Be shows a greater ability to form mycorrhizae with Populus deltoides Bartr cv. ‘Lux’ (Poplar I-69). Pt and La had relatively weaker abilities of colonization. The other five ECM fungal species, i.e., Scleroderma luteus (Sl), Leccinum scabrum (Ls), Boletus speciosus (Bs), Calvatia craniiformis (Cc) and Rhizopogen luteous (Rl) could not easily form mycorrhizae with poplar seedlings grown in sterilized substrates, but could do so in non-sterilized soil. With the method of drilling and injecting liquid inoculum, a simple operation, the mycorrhizal infection rates were higher than with the other two methods, applying solid inoculum as fertilizer at the bottom of the pots and dipping roots in the inoculum slurry. P. simonii Carr. formed mycorrhizae with most of the nine ECM fungi. P. × euramericana (Dode) Guinier cv. ‘San Martino’ (Poplar I-72) and P. deltoids Harvard × P. deltoids Lux (Poplar NL-351) had the highest compatibility with Pt. Poplar I-69 shows the highest compatibility with Xc. The study indicates that the optimal ECM fungi for poplars I-69, I-72 and NL-351 were Be, Xc and Pt, respectively. The optimal fungi for P. simonii Carr. were Xc and Be. These ECM fungi promoted the growth of the poplar seedlings significantly.
  • SUN Yong, LIN Lu, DENG Haibo, PENG Hong, LI Jiazhe, SUN Runchang, LIU Shijie
    Bamboo fiber dissolution and hydrolysis in formic acid were studied. After hydrolysis, formic acid can be recovered in a clean state and reused. Solid water-soluble sugars were obtained. After being dipped into the formic acid solution for 30 min, the bamboo fibers started to swell. After one hour, the bamboo fibers gradually started to dissolve in the formic acid solution. The color of the liquor/solution turned green and dark. In the end, the bamboo fibers became thoroughly dissolved in the liquor after four hours. There was a clear hierarchical tissue structure on the fiber surface, as observed by AFM before treatment. The differential structure disappeared after 30 min of treatment. The fiber surface became plump and glossy. After six hours reaction at 60°C, the solid sugar mixture recovered contained glucose, cellobiose, cellotriose, cellotetrose, cellopentose and cellohexaose. A significant fraction of the sugar products consisted of monomeric glucose. More than 54.5% of the bamboo fiber mass had been transformed into monomeric glucose.
  • WANG Fengqiang, ZHANG Zhijun, WANG Qingwen, TANG Jiayin
    An intumescent waterborne amino-resin fire-retardant coating for wood (C) was synthesized and its fire-retardant and smoke-suppressant properties were investigated. The main film-builder of C was urea-formaldehyde resin blended with polyvinyl acetate resin. The intumescent fire-retardant system of C consisted of guanylurea phosphate (GUP), ammonium polyphosphate (APP), pentaerythritol (PER) and melamine (MEL). Specimens of plywood painted, respectively, with a commercial intumescent fire-retardant coating (A), a synthesized coating (C), and the main film-builder of coating C (B), as well as an unpainted plywood (S-JHB), were analyzed by cone calorimetry (CONE). The results show a marked decrease in the heat release rate (HRR) and the total heat release (THR), an increased mass of residual char (Mass), a marked postponement in time to ignition (TTI) and a reduced carbon monoxide production rate (PCO). The smoke production rate (SPR) and total smoke production (TSP) of the plywood painted with coating C were observed with the CONE test. The overall fire-retardant and smoke-suppressant performance of the synthesized coating C was much better than that of the commercial coating A. The thermo-gravimetric analysis (TGA) results of coating C and its film-builder B indicated that the thermal degradation process of B was slowed down by the addition of the intumescent fire-retardant system; the increase in the amount of charring of coating C was considerable.
  • SUN Fengwen, LI Xiaoke, ZHANG Qian
    The technology of liquefying processed-waste bamboo with phenol is investigated by single factor trials and an orthogonal design. We studied the preparation technology and properties of adhesives from this phenol-liquefied bamboo with formaldehyde (BPF). The results show that temperature has a significant effect on liquefaction. The effect of the mass ratio of phenol to bamboo comes second and the catalyst dosage within the range of 2%–4% is the least effective. The optimum conditions of liquefaction are as follows: a mass ratio of phenol to bamboo 3.5, a catalyst dosage of 4%, liquefying temperature 145°C and liquefying time 60 min. The liquefaction rate of bamboo reached 99.1%. For the preparation of the adhesive, a mass ratio of liquefied bamboo products to formaldehyde (37%) is 100 to 164.8–199.5, while the ratio 100 to 108.2 is the best. This adhesive has a lower curing temperature than that of normal PF resin. At a hot-press temperature of 130 or 140°C, this new adhesive provides excellent bonding strength of plywood. The most favorable temperature for hot-pressing is 140°C.
  • MA Yan, Alun
    We have studied the structural mechanism of micron flaky wood fiber light density board (MFLB), of which voids are an important structural characteristic. A new parameter called hole compressibility (?) was added to study the characteristics of MFLB further, in order to produce various levels of hole compressibility. A set of hot pressures was applied, and uniform parts at cross-sections of MFLB were selected to study the effects of hole compressibility on the modulus of elasticity (MOE) and modulus of rupture (MOR) of MFLB by microscopic analyses. The results showed that MFLB (0.3 g/cm3 in density) processed at various hot pressures (from 1.6 to 2.2 MPa) all meet the norms of the Japan Light Particleboard Industrial Standard JISA 5908, where ? ≤ 0 ranging from -0.0487 to -0.068. The critical value of hole compressibility at which the strength began to decrease was also obtained. We compared the void distribution, size and shape at different void contents and hole compressibility and discussed the effects of hole compressibility on MOE and MOR of MFLB as well. To a certain density of raw material and micro-fiber of a certain thickness, the strength of MFLB can be decreased with an increase in hole compressibility. When the hole compressibility of MLFB exceeds a certain critical value, loading at a lower level will decrease MOR and MOE of MFLB considerably.
  • DU Guanben, HUANG Linrong, SUN Zhaobin
    Surface treatment of bamboo was carried out by microwave plasma (MWP), surface contact angle of the sample was measured using glycerin and urea-formaldehyde resin (UFR) liquid, and the effects on the surface performance of the bamboo sample was evaluated. The results show that the surface contact angle of the sample presented a generally decreasing trend when prolonging the MWP treatment time and shortening the distance between the sample and the resonance cavity. The surface contact angle of the sample decreased by 49%–59% under the following conditions: MWP treatment for 30 s, the distance between the sample and resonance cavity at 40 mm, and measurement at 15 s after dripping with glycerin. The surface contact angle of the sample measured with the glycerin was lower than that with UFR. No matter whether we used glycerin or UFR, the contact angle of the sample at 15 s after dripping was lower than that at 5 s after dripping. The grinding treatment had little effect on the surface contact angle of the sample after MWP treatment, and the modification effect of MWP treatment after grinding was better than that of sole MWP treatment.
  • XU Ming, CHENG Shuna, FU Shenyuan
    By means of the analysis of TG-DSC curves, we studied the effect of temperature and several additives, i.e., H2SO4, HCl, NaOH, H2O2 and H3PO4 on the performance of the thermal decomposition of bamboo. The results indicated that the weightlessness of pure bamboo powder may be divided into three stages, up to 700°C. At each stage, the effect of each chemical additive on the weightlessness rate of bamboo was different. In the end, we analyzed the function of additives in practical applications of the thermal decomposition of bamboo.
  • FANG Hongxia, SUN Jinyu, ZHANG Lei
    Bamboo cellulose, lignin and starch have been molecularly blended to form homogeneous composite films by NMMO-technology. The structural properties of the films were investigated with FTIR, WAXD and AFM technologies, respectively. The results show that bamboo cellulose, lignin and starch have been molecularly blended through NMMO-technology. There was a two-phase system consisting of ternary composite components as one phase and pores as the other on the surface of the composite film. Because of the existence of homogeneous phase structure formed by the rearrangement of the natural polymer molecules, the film shows good properties originating from the mutual supplement of different natural components.