Sep 2007, Volume 2 Issue 3
    

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  • Health diagnoses of ecosystems subject to a typical erosion environment in Zhifanggou watershed, north-west China
    DAI Quanhou, LIU Guobin, XUE Sha, LAN Xue, TIAN Junliang, WANG Guoliang, ZHAI Sheng
    2007, 2(3): 241-250. https://doi.org/10.1007/s11461-007-0040-1
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    Ecosystem health is the object of water and soil conservation and ecological building in loess hilly areas under erosion environment. Using principles of ecosystem health quantitative assessment and diagnosis index selection, 17 factors were considered from three aspects: resource and environmental capacity, social and economic impact, and ecological services. An evaluation index system on ecosystem health was established for a small watershed under erosion conditions. Mean-square deviation was employed to determine the weight of each factor and then step-up multilayer synthesis with linear weighting function was used to build a two-level hierarchy and collection index health consultation model. The health dynamics of the ecosystem in the small watershed under erosion conditions was analyzed. Results show that the watershed ecosystem is relatively stable and has an increasing annual fluctuation (0.370 in 1985 to 0.573 in 2003) for the health index. This increasing trend indicates an adequately strong ability for sustainable development. At the same time, obstacles and advantages to the watershed ecosystem health were studied by introducing the concepts of obstacle degree and advantage, and path analysis method, considering the real economic optimal level as the uppermost goal. Finally, suggestions on ecological building were provided as a scientific basis for ecosystem rehabilitation in the small watershed.
  • C and N stocks under three plantation forest ecosystems of Chinese fir, Michelia macclurei and their mixture
    WANG Hua, HUANG Yu, FENG Zongwei, WANG Silong
    2007, 2(3): 251-259. https://doi.org/10.1007/s11461-007-0041-0
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    Chinese fir (Cunninghamia lanceolata), a type of subtropical fast-growing conifer tree, is widely distributed in South China. Its plantation area covers more than 7?106 hm2, accounting for 24% of the total area of plantation forests in the country. In recent decades, the system of successive plantation of Chinese fir has been widely used in southern China due to anticipated high economic return. However, recent studies have documented that the practice of this system has led to dramatic decreases in soil fertility and forest environment as well as in productivity. Some forest ecologists and managers recognize the ecological role performed by broadleaf trees growing in mixtures with conifers, and a great deal of studies on mixture effects have been conducted, particularly on mixture species of temperate and boreal forests, but these research results were not completely consistent. Possibilities include dependence of the mixture effects in large part to specific site conditions, the interactions among species in mixtures and biological characteristics of species. Although some researchers also studied the effects of mixtures of Chinese fir and broadleaf tree species on soil fertility, forest environment and tree growth status, little information is available about the effects of Chinese fir and its mixtures with broadleaves on carbon and nitrogen stocks.The experimental site is situated at the Huitong Experimental Station of Forest Ecology, Chinese Academy of Sciences, Hunan Province (26º40′–27º09′ N, 109º26′–110º08′ E). It is located at the transition zone from the Yunnan-Guizhou Plateau to the low mountains and hills of the southern bank of the Yangtze River at an altitude of 300 1,100 m above mean sea level. At the same time, the site is also a member of the Chinese Ecosystem Research Network (CERN), sponsored by the Chinese Academy of Sciences (CAS). This region has a humid mid-subtropical monsoon climate with a mean annual precipitation of 1,200 1,400 mm, most of the rain falling between April and August, and a mean temperature of 16.5?C with a mean minimum of 4.9?C in January and a mean maximum of 26.6?C in July. The experimental field has red-yellow soil. After a clear-cutting of the first generation Chinese fir (Cunninghamia lanceolata) plantation forest in 1982, three different plantation forest ecosystems, viz. mixture of Michelia macclurei and Chinese fir (MCM), pure Michelia macclurei stand (PMS) and pure Chinese fir stand (PCS), were established in the spring of 1983. A comparative study on C and N stocks under these three plantation forest ecosystems was conducted in 2004. Results showed that carbon stocks were greater under the mixtures than under the pure Chinese fir forest and the pure broad-leaved forest, and the broadleaves and the mixtures showed higher values in nitrogen stocks compared with the pure Chinese fir forest. The spatial distribution of carbon and nitrogen stocks was basically consistent, the value being greater in soil layer, followed by tree layer, roots, understory and litter layer. The carbon and nitrogen stocks in soil layer were both highly correlated with the biomass in understory and litter layer, indicating that understory and forest litterfall exerted a profound effect on soil carbon and nitrogen stocks under plantation ecosystems. However, correlations among soil carbon, nitrogen stocks and below ground biomass of stand have not been observed in this study.
  • Nitrification and denitrification in subalpine coniferous forests of different restoration stages in western Sichuan, China
    LIU Yi, CHEN Jinsong, LIU Qing, WU Yan
    2007, 2(3): 260-265. https://doi.org/10.1007/s11461-007-0042-z
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    Nitrification is the biological conversion of organic or inorganic nitrogen compounds from a reduced to a more oxidized state. Denitrification is generally referred to as the microbial reduction of nitrate to nitrite and further gaseous forms of nitric oxide, nitrous oxide and molecular nitrogen. They are functionally interconnected processes in the soil nitrogen cycle that are involved in the control of longterm nitrogen losses in ecosystems through nitrate leaching and gaseous N losses. In order to better understand how nitrification and denitrification change during the process of ecosystem restoration and how they are affected by various controlling factors, gross nitrification rates and denitrification rates were determined using the barometric process separation (BaPS) technique in subalpine coniferous forests of different restoration stages. The results showed that forest restoration stage had no significant effects on gross nitrification rates or denitrification rates (One-way ANOVA (analysis of variance), ρ⟨0.05). There was no significant difference in the temperature coefficient (Q10) for gross nitrification rate among all the forest sites (One-way ANOVA, ρ⟨<0.05). Gross nitrification rates were positively correlated with water content ( ρ⟨0.05), but not with soil pH, organic matter, total nitrogen, or C/N ratios. Denitrification rates in all the forest soils were low and not closely correlated with water content, soil pH, organic matter, or total nitrogen. Nevertheless, we found that C/N ratios obviously affected denitrification rates ( ρ⟨0.05). Results from this research suggest that gross nitrification is more responsible for the nitrogen loss from soils compared with denitrification.
  • Characteristics of carbon and nitrogen of soil microbial biomass and their relationships with soil nutrients in Cunninghamia lanceolata plantations
    HE Youjun, WANG Qingkui, WANG Silong, YU Xiaojun
    2007, 2(3): 266-271. https://doi.org/10.1007/s11461-007-0043-y
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    The soil microbial biomass and nutrient status under the native broadleaved forest and Cunninghamia lanceolata plantations at the Huitong National Research Station of Forest Ecosystem (in Hunan Province, midland of China) were examined in this study. The results showed that after the native broadleaved forest was replaced by mono-cultured C. lanceolata or C. lanceolata, soil microbial biomass and nutrient pool decreased significantly. In the 0–10 cm soil layer, the concentrations of soil microbial carbon and nitrogen in the broadleaved forest were 800.5 and 84.5 mg/kg, respectively. These were 1.90 and 1.03 times as much as those in the first rotation of the C. lanceolata plantation, and 2.16 and 1.27 times as much as those in the second rotation of the plantation, respectively. While in the 10–20 cm soil layer, the microbial carbon and nitrogen in the broadleaved forest were 475.4 and 63.3 mg/kg, respectively. These were 1.86 and 1.60 times as much as those in the first rotation, and 2.11 and 1.76 times as much as those in the second rotation, respectively. Soil nutrient pools, such as total nitrogen, total potassium, NH4+-N, and available potassium, also declined after the C. lanceolata plantation replaced the native broadleaved forest, or Chinese fir was planted continuously. Less litter and slower decay rate in pure Chinese fir plantation were the crucial factors leading to the decrease of soil microbial biomass and nutrient pool in this area. Human disturbance, especially slash-burning and site preparation, was another factor leading to the decrease. There were significant positive correlations between soil microbial carbon and nitrogen and soil nutrients. To improve soil quality and maintain sustainable productivity, some measures, including planting mixed conifer with hardwood, preserving residues after harvest, and adopting scientific site preparation, should be taken.
  • Retention of available P in acid soils of tropical and subtropical evergreen broad-leaved forests
    CHEN Jianhui, YANG Xiaodong, ZOU Xiaoming
    2007, 2(3): 272-277. https://doi.org/10.1007/s11461-007-0044-x
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    Precipitation of mineral phosphate is often recognized as a factor of limiting the availability of P in acidic soils of tropical and subtropical forests. For this paper, we studied the extractable P pools and their transformation rates in soils of a tropical evergreen forest at Xishuangbanna and a subtropical montane wet forest at the Ailao Mountains in order to understand the biogeochemical processes regulating P availability in acidic soils. The two forests differ in forest humus layer; it is deep in the Ailao forest while little is present in the Xishuangbanna forest. The extractable P pools by resin and sodium-bicarbonate decreased when soil organic carbon content was reduced. The lowest levels of extractable P pools occurred in the surface (0–10 cm) mineral soils of the Xishuangbanna forest. However, microbial P in the mineral soil of the Xishuangbanna forest was twice that in the Ailao forest. Potential rates of microbial P immobilization were greater than those of organic P mineralization in mineral soils for both forests. We suggest that microbial P immobilization plays an essential role in avoiding mineral P precipitation and retaining available P of plant in tropical acidic soils, whereas both floor mass accumulation and microbial P immobilization function benefit retaining plant available P in subtropical montane wet forests.
  • Ramet population structure of Fargesia nitida in different canopy conditions of the subalpine dark coniferous forest in the Wolong Nature Reserve, China
    TAO Jianping, SONG Lixia, LI Yuan, WANG Yongjian, YU Xiaohong
    2007, 2(3): 278-283. https://doi.org/10.1007/s11461-007-0045-9
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    The bamboo Fargesia nitida, one of the giant panda s main food sources and the dominant shrub species of the forest understory, is mainly distributed in the dark coniferous belt in western Sichuan and southern Gansu in China. To study the impact of different forest canopy conditions on subalpine dwarf bamboo populations, ramet population structures of clonal Fargesia nitida were surveyed in: forest understory (FU), moderate gap (MG), large gap (LG) and marginal open space (MOS). In order to determine how the ramet structures could be affected and its effects on these four canopy conditions, a field survey of the age structure of Fargesia nitida population, its morphological traits and biomass was conducted in the Abies faxoniana forest situated in the Wolong Nature Reserve, western Sichuan, China. The main results were as follows. First, at the ramet level, the structures of the ramet populations in four canopy conditions were significantly different, and as the canopy density decreased, the mean height, basal diameter and biomass of the populations increased following the order: LG⟨MG⟨FU. Second, the biomass proportions of ramets modularly varied with different canopy conditions and leaf biomass proportion was positively related to the canopy density except for the MOS where the biomass proportions of rhizome and roots were both higher than those in the three other canopy conditions. Third, ramet specific leaf weight increased in parallel with the decrease in canopy density. In the MG, the values of the individual leaf biomass and leaf area were the largest, followed by those in the MOS. Both the individual leaf biomass and leaf area were significantly different from those in the FU and LG. Leaf number per ramet was significantly different among the four different canopy conditions and the biggest in the LG. Fourth, the ramet population mortality was the lowest in the FU (Chi-square test, ρ⟨0.01), while there was no significant difference in the average population age (Mann-Whitney test, ρ⟩0.05). All the results indicated that it was not ramet age, but the morphological changes and biomass distribution that exhibited the response of the ramet population of Fargesia nitida to the changed canopy conditions.
  • A model for vertical distribution of fine roots in Robinia pseudoacacia plantations on the Loess Plateau
    CHENG Xiangrong, ZHAO Zhong, WANG Dihai, GUO Mancai, YUAN Zhifa
    2007, 2(3): 291-297. https://doi.org/10.1007/s11461-007-0047-7
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    Based on a detailed investigation of vertical distributions of fine roots in Robinia pseudoacacia plantations at the Ansai Soil and Water Conservation Station, Shaanxi Province, a model was developed for the deep distribution of fine roots of R. pseudoacacia, which reflects the growth of fine roots affected by the mixed process of infiltration water and deep soil water. The maximum depth of the distribution hmax and the depth of the highest fine root density (FRD) hp were determined and the maximum depth of infiltration water supplied for fine root growth hq could also be calculated, hq was considered as the approximate boundary between infiltration water and deep soil water in support of the growth of fine roots. According to the model, the soil water of R. pseudoacacia woodland in the profile could be classified into three layers: the first layer from the soil surface to hp was the active water exchange layer, very much affected by precipitation; the second was the soil water attenuation layer, between hp and hq and largely affected by the vertical distribution of fine roots;.the third was the relatively stable soil water layer below hq, below which soil water did not change much. The percentage of infiltration water supplied for the growth of fine roots reached a level of 88.32% on the shaded slopes and 85.21% on sunny slopes. This indicated infiltration of precipitation played a crucial role in the growth of R. pseudoacacia in the gully region of the Loess Plateau. The research of interaction between the distribution of fine roots and soil water in the profile will help to explain the reasons for the complete drying out of soils and provide a theoretical basis for continuing the policy of matching tree species with sites on the Loess Plateau.
  • Impact factors on fine root seasonal dynamics in Fraxinus mandshurica plantations
    MEI Li, YU Shuiqiang, SHI Jianwei, WANG Zhengquan, HAN Youzhi
    2007, 2(3): 298-304. https://doi.org/10.1007/s11461-007-0048-6
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    Fine root turnover plays important roles in carbon allocation and nutrient cycling in forest ecosystems. Seasonal dynamics of fine roots is critical for understanding the processes of fine root turnover. From May to October 2002, soil core method was used for estimating the seasonal pattern of fine root (diameter<1 mm) parameters (biomass, specific root length (SRL) and root length density (RLD)) in a Manchurian ash (Fraxinus mandshurica) plantation located at the Maoershan Experiment Station, Heilongjiang Province, northeast of China. The relationships of fine root biomass, SRL and RLD with available nitrogen in soil, average soil temperature per month in 10 cm depth and soil moisture content were analyzed. Seasonal variation of fine root biomass was significant (P<0.05). The peak values of fine root biomass were observed both in spring and in autumn, but SRL and RLD were the highest in spring and lowest in autumn. Specific root length and root length density were higher in spring and summer, which means that fine root diameter was thinner. In autumn, both parameters decreased significantly due to secondary incrassation of fine root diameter or the increase of tissue density. Seasonal dynamics of fine roots was associated with available nitrogen in soil, soil temperature in 10 cm depth and moisture content. Fine root biomass has a significant relationship with available NH4+-N in soil. Available NO3--N in soil, soil temperature in 10-cm depth and moisture content have a positive correlation with fine root biomass, SRL and RLD, although these correlations are not significant (P⟩0.05). But the compound effects of soil available N, soil temperature and soil moisture content are significant to every root parameter. The variations of these three root parameters in different seasons show different physiological and ecological functions in different growing periods.
  • Shear strengths of undisturbed and remolded soil under typical forests in Jinyun Mountain, Chongqing City, southwest China
    ZHANG Xiaoming, WANG Yujie, WANG Yunqi, XIA Yiping, WU Yun, CHEN Lin
    2007, 2(3): 305-309. https://doi.org/10.1007/s11461-007-0049-5
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    To find the controlling measures in preventing soil and water loss from soil mechanics, according to the prescribed methods of soil engineering test regulations, shear strengths of undisturbed and remolded soils under five typical forests in Jinyun Mountain, Chongqing City were measured using the direct shear apparatus. Shear difference of both undisturbed and remolded soils was compared at the same vertical loading, under the condition of the same dry density and water content from the same forest land. The effect of roots (the finest roots) in soil-root composites (undisturbed soils) was analyzed. The results indicate that undisturbed soils have higher shear resistance and less shear displacement than remolded soils at the same vertical loading, when both soils have the same dry density and water content under the same vegetations. It has been shown that shear failure of undisturbed soils approximately indicate plastic failure, while shear failure of remolded soils is of the elastic nature. Shear strength of undisturbed soils has a positive correlation with root content, and relevant regression models about undisturbed soil were established from this.
  • Photosynthetic physio-response of Taxodium ascendens seedlings to different soil water gradients
    LI Changxiao, ZHONG Zhangcheng
    2007, 2(3): 310-315. https://doi.org/10.1007/s11461-007-0050-z
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    Four different kinds of water treatments were applied to study the photosynthetic eco-physiological characteristics of Taxodium ascendens seedlings in the environment of the Three Gorges hydro-fluctuation belt. The four kinds of water treatments were: normal growth water condition (CK), light drought stress (T1), soil water saturation (T2), and soil submersion (T3). The results showed that different water treatments could effectively influence the content of the photosynthetic pigment, leaf gas exchange and apparent resources use efficiency of T. ascendens seedlings. It was also demonstrated that the T. ascendens seedlings could not only tolerate water submersion and wet conditions but also endure a certain degree of drought. To establish a protection forest system in the hydro-fluctuation belt in the Three Gorges Reservoir Area, the species T. ascendens is suitable for planting in conditions of root submersion or water-saturated soil. In case it is planted in drought conditions, this tree species should be watered appropriately in order to keep its normal net photosynthetic rate.
  • Change of trunk sap flow of Ginkgo biloba L. and its response to inhibiting transpiration treatment
    SUN Shoujia, GU Runze, CONG Richen, CHE Shaochen, GAO Junping
    2007, 2(3): 316-322. https://doi.org/10.1007/s11461-007-0051-y
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    For this paper, GREENSPAN sap flow system was used to monitor the dynamics of trunk sap flow of Gingkgo biloba. Results indicate that sap flow velocity is significantly different among different heights, depths, and directions of the trunk. Sap flow velocity at the upper position of the trunk is higher than that of the middle and lower position, but cumulative flux is not significantly different among the upper, middle and lower sections. Sap flow velocity at 10 mm reached the most and that at 20 mm the least. However, sap flow velocity at 5 mm and 15 mm was similar and was second among the four depths. Results also showed that sap flow velocity of the south was the highest, and that of the west was next. An Automatic Weather Station of HOBO was synchronously applied to measure these meteorological parameters, and the relationship between these parameters and the changes of trunk sap flow velocity were analyzed. We found that the change of sap flow velocity was a single-crest curve on clear days and multi-crest curve on cloudy and rainy days. In addition, it is also revealed that by stepwise regression analyses photosynthetical active radiation (PAR), temperature and wind speed are the main environmental factors affecting sap flow velocity. The efficient methods of reducing water transpiration of trees, including leaf pruning, overshadowing and antitranspirant spraying, were found by investigating the effects on inhibiting transpiration, which indicated that spraying of antitranspirants, leaf pruning and overshadowing could significantly reduce transpiration but the effects of leaf pruning and overshadowing were far better than that of antitranspirant spraying.
  • Evaluation of the sap flow using heat pulse method to determine transpiration of the Populus euphratica canopy
    ZHANG Xiaoyou, KANG Ersi, ZHOU Maoxian
    2007, 2(3): 323-328. https://doi.org/10.1007/s11461-007-0052-x
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    The sap flow of the sampled Populus euphratica stems at different radial depths and directions had been studied in Ejina Oasis, in the lower reaches of the Heihe River. Based on sap flow measurements, the transpiration of the entire canopy was calculated. Results showed a linear correlation between the sap flow and the sapwood area of the P. euphratica. Through the analysis of the diameter at breast height in the sample plot, it was found that the distribution of the diameters and the corresponding sapwood area was exponentially correlated, with the coefficient of correlation being 0.976,7. The calculated transpiration of the Populus euphratica canopy was 214.9 mm based on the specific conductivity method.
  • Transfer characteristics of nutrient elements through hydrological process of a Pinus tabulaeformis stand in the West Mountain of Beijing
    NIE Lishui, WANG Dengzhi, LI Jiyue
    2007, 2(3): 329-334. https://doi.org/10.1007/s11461-007-0053-9
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    Forest precipitation chemistry is a major issue in forest hydrology and forest ecology. Chemical contents in precipitation change significantly when different kinds of external chemical materials are added, removed, translocated and transformed to or in the forest ecosystem along with precipitation. The chemistry of precipitation was monitored and analyzed in a 31-year-old Pinus tabulaeformis forest in the West Mountain of Beijing. Movement patterns of nutrient elements in hydrological processes can be discovered by studying this monitored data. Also, the information is useful for diagnosing the function of ecosystems and evaluating the impact of the environment on the ecosystem. Samples of rainfall, throughfall and stemflow were collected on the site. In the lab, Ca2+ and Mg2+ were analyzed by flame atomic absorption and K+ and Na+ by flame emission. NH4+-N was analyzed by indophenol blue colorimetry and NO3--N was analyzed by phenoldisulfonic acid colorimetry. The results showed that: 1) The concentration gradient of nutrient elements clearly changed except for Na+. The nutrients in stemflow were significantly higher than those of throughfall and rainfall as the precipitation passed through the P. tabulaeformis forest. The monthly patterns showed distinct differentiation. There are indications that a large amount of nutrients was leached from the canopy, which is a critical function of intra-ecosystem nutrient cycling to improve the efficiency of nutrient use. 2) The concentrations of NO3--N and K+ changed more than those of the other nutrient elements. The concentration of NO3--N in throughfall and stemflow was 4.4 times and 9.9 times higher than those in rainfall, respectively. The concentration of K+ in throughfall and stemflow was 4.1 times and 8.1 times higher than those in rainfall, respectively. 3) The leaching of nutrient elements from the stand was an important aspect of nutrient return to the P. tabulaeformis forest, which returned a total amount of nutrient of 54.1 kg/hm2, with the contribution of Ca2+ and K+ much greater than that of other elements. Also, K+ was the most active element in leaching intensity. 4) Nutrient input through precipitation was the main source in the West Mountain of Beijing and the amount of nutrient added was 66.4 kg/hm2, of which Ca2+ and N contributed much more than the other nutrient elements. When precipitation passes through the P. tabulaeformis forest, 121 kg/hm2 of nutrient is added to the forest floor. Ca2+ recorded the greatest nutrient increase, with 61.2 kg/hm2, followed by N (NH4+-N and NO3--N), K+ and Mg2+, with 31.3 and 16.5, and 8.11 kg/hm2, respectively. The least was Na+, 3.34 kg/hm2.
  • Risk management: A probe and study on forest fires
    YUE Jinzhu, FENG Zhongke, JIANG Wei, YANG Xiaoqin
    2007, 2(3): 335-339. https://doi.org/10.1007/s11461-007-0054-8
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    The subject of risk management is attracting more and more attention around the world. The risk of forest fire disasters should be faced and dealt with for forest fires cannot be avoided. Treating forest fire disasters as a risk management issue promotes important measures and methods for fire fighters to prevent, reduce and control the risks of forest fires. In this paper, the risk concept and risk connotation as well as the management risks for forest fire suppression are discussed clearly. Issues such as risk judgments, risk analysis, risk control and the assessment of risk, including their contents and corresponding methods are clarified.
  • Variation analysis and fine family selection on half-sib progenies from clonal seed orchard of Pinus massoniana
    JI Kongshu, XU Li′an, FAN Minliang
    2007, 2(3): 340-346. https://doi.org/10.1007/s11461-007-0055-7
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    Variation of traits that include height, diameter at breast height (DBH), stem volume, crown width, straightness, wood basic density, tracheid length and width of open-pollinated progenies from clonal seed orchard of Pinus massoniana was analyzed. Differences in traits such as growth, tree form and wood quality among families was significant, which indicated that the improvement potential was notable. Heritability of height and wood basic density reached 0.691 and 0.640, respectively. According to a correlation analysis between traits, stem straightness could be improved indirectly when growth traits are improved; growth traits were significantly correlated with wood basic density; and wood basic density was not significantly correlated with length and width of the tracheid. Under the selection ratio of 10%, genetic gains were 19.74% and 19.32% respectively, and selected families from the progeny test stands at the age of five years and eight years were the same. Genetic correlation of height, DBH and stem volume was also significant at the level of 0.01. These show that selection of the short rotation of P. massoniana for pulp and paper use would be efficient for five-year-old trees. According to the comparison of the heritability of all the traits and taking into account the result of canonical correlation analysis, height could be considered as the most important index for selection. Given wood quality of all the families, and flowering and fruit settings of the clones in a seed orchard, twelve fine families were selected at 10% selection ratio of height growth and stem volume.
  • Impact of coupling agent on properties of wood-plastic composite
    XU Min, LI Shuai
    2007, 2(3): 347-349. https://doi.org/10.1007/s11461-007-0056-6
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    The impact of two coupling agents, maleic anhydride (coupling agent 1) and isocyanate (coupling agent 2) on the properties of wood-plastic composites (WPC) was studied. Wood-plastic composites were made with coupling agents 1 and 2 and properties were tested under the condition that the ratio of wood fiber to thermoplastic polymer was 7:3, target density was 0.7 g/cm3, press temperature was 175vH, press time was 8 min, and adding amount of coupling agent 2%. Results show that coupling agent 2 was superior to coupling agent 1 and had great effect on the physical and mechanical properties of WPC. When using the same coupling agent, the impact on their properties varied with different thermoplastic polymers.
  • Power spectrum density and experimental modal analysis of wide belt sander applied in domestic wood industry
    WANG Zheng, ZHU Dianxiang
    2007, 2(3): 350-354. https://doi.org/10.1007/s11461-007-0057-5
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    This paper took the upper-lower wide belt sander B229 with four-feet wide belts, manufactured in China, as the study target. By means of framework dynamic design, we study its vibration characteristics by commencing from the place having horizontal defects and used experimental modal analysis (EMA) and power spectrum density (PSD) to observe the sanding parts and the whole machine, respectively. In the modal test, we mainly adopted the cross spots testing method to get the frequency response function of the fixed spots to every excitation vibration spot, then applied the SISO frequency response function and the frequency response function fitting method to identify and complete parameter recognition, respectively. The typical frequency response function chart of the whole machine and its sanding parts, as well as its second-order mode charts of contacting roller, were obtained. Through PSD analysis, we can get the amplitude-frequency spectrum and drive frequency.

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