Jun 2008, Volume 3 Issue 2
    

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  • Effects of elevated CO concentrations on soil microbial respiration and root/rhizosphere respiration in forest soils
    ZHOU Yumei, HAN Shijie, ZHENG Junqiang, ZHANG Haisen, XIN Lihua
    2008, 3(2): 131-138. https://doi.org/10.1007/s11461-008-0027-6
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    The two main components of soil respiration, i.e., root/rhizosphere and microbial respiration, respond differently to elevated atmospheric CO2 concentrations both in mechanism and sensitivity because they have different substrates derived from plant and soil organic matter, respectively. To model the carbon cycle and predict the carbon source/sink of forest ecosystems, we must first understand the relative contributions of root/rhizosphere and microbial respiration to total soil respiration under elevated CO2 concentrations. Root/rhizosphere and soil microbial respiration have been shown to increase, decrease and remain unchanged under elevated CO2 concentrations. A significantly positive relationship between root biomass and root/rhizosphere respiration has been found. Fine roots respond more strongly to elevated CO2 concentrations than coarse roots. Evidence suggests that soil microbial respiration is highly variable and uncertain under elevated CO2 concentrations. Microbial biomass and activity are related or unrelated to rates of microbial respiration. Because substrate availability drives microbial metabolism in soils, it is likely that much of the variability in microbial respiration results from differences in the response of root growth to elevated CO2 concentrations and subsequent changes in substrate production. Biotic and abiotic factors affecting soil respiration were found to affect both root/rhizosphere and microbial respiration.
  • Biomass of fine roots and its relationship with water-stable aggregates in a composite ecosystem of triploid in the conversion of farmland to forest
    FANG Chuan, LI Xianwei, ZHANG Jian, FANG Bing, DONG Huixia
    2008, 3(2): 158-164. https://doi.org/10.1007/s11461-008-0031-x
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    A study on the biomass of fine roots and its relationship with water-stable aggregates (WSA) was conducted in two herbaceous models, triploid Populus tomentosa + Lolium multiflorum (TL) and triploid P. tomentosa + natural grass (TN). Both of the model triploid P. tomentosa stands were four years old converted from agriculture. Unconverted steep slope farmland was used as a control site. Results showed that the biomass of fine roots (≤1 mm) in different layers varied in the following descending order: upper layer, middle layer and lower layer, at approximate ratios of 50:30:20. The average annual biomass of fine roots in ryegrass was twice that of the mixed natural grass-forest land. The total amount of natural grass roots was 4.4 times that of the ryegrass model. Water-stable aggregates of the upper, middle and lower layers and the unconverted farmland did not show any significant differences, whereas the amounts of water-stable aggregates of big-particles in the upper and middle layers were much larger than those of unconverted lands. The amounts of water-stable aggregates of natural grass-forest lands (TN model) were higher than those of managed grass-forest lands (TL model). Two-way analysis of variance indicated that fine roots (≤1 mm) could significantly enhance water-stable aggregates and total water-stable aggregates. We conclude that the program of converting agricultural lands to forest-grass lands is an effective way in improving soil anti-erosion capability.
  • Factors affecting distribution of microbiotic crusts in the grain-for-green land of the loess region, northern Shaanxi, China
    WANG Na, ZHU Qingke, ZHANG Yuqing, WU Xiuqin, JIAO Wenjun
    2008, 3(2): 165-170. https://doi.org/10.1007/s11461-008-0024-9
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    A field survey was conducted in the grain-for-green land of the loess region, northern Shaanxi, China, from July to August of 2005 to provide a scientific evaluation of the grain-for-green project, including its soil and water conservation and other ecological benefits for the region. The distribution of microbiotic crusts were studied, while human disturbance, aspect, topography, vegetation structure and other factors affecting it were obtained from the analysis of survey data from 78 sample plots. Results show that crust coverage is larger on less-disturbed plots than on highly-disturbed ones, on north-facing plots than on south-facing ones and on gully-slopes than on ridge-slopes. Coverage increases with herbal coverage and trees can provide better conditions for distribution of crusts than shrubs. Therefore, crust coverage is larger in herb-dominated plots than in tree-dominated ones and crusts in shrub-dominated plots are smaller. However, we made no progress in our study on deciding how slope degrees and herb species affect the distribution of crusts. We believe that more studies are necessary for a further exploration of the relationship between them.
  • Growth rate of mosses and their environmental determinants in subalpine coniferous forests and clear-cuts at the eastern edge of the Qinghai-Tibetan Plateau, China
    WANG Qian, WU Ning, LUO Peng, YI Shaoliang, BAO Weikai, SHI Fusun
    2008, 3(2): 171-176. https://doi.org/10.1007/s11461-008-0030-y
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    Mosses cover most of the forest floor of subalpine forests at the eastern edge of the Qinghai-Tibetan Plateau, the origin of many important rivers in China. They play a crucial role in preventing soil erosion and conserving large amounts of water thereby regulating the water budget of local ecosystems. This area has a harsh climate due to low temperatures and low air pressure at high elevations. But the temperature varies considerably during the growing season, which does not favor the regeneration of spruce seedlings on clear-cuts after logging. Leaves of mosses have a single layer of cells and are thus sensitive to environmental changes. This attribute may be useful for monitoring environmental conditions and guide artificial regeneration. The growth of mosses has never been studied in this area and the variables indicating their growth in the subalpine forest ecosystems still needs investigation.Growth rates of mosses have been rarely studied worldwide because the methods are time consuming and often inaccurate. A more simple and accurate method for measuring moss growth would help and encourage relevant research. We have found a method that will promote the efficiency in field measurements. Because of the special growth properties of mosses, the apical cell of branches initiates growth and the preceding leaves will stay where they were as the tips grow. Once mosses are marked with red oil at the tip of branches surrounded by young leaves, that portion of the branch above the marked leaves represents growth after labeling.Two plots, one in an old-growth spruce forest and another in a nearby clear-cut, were selected to label mosses in a subalpine area of western Sichuan Province during the growing season in 2001. The labeling was done on May 7 and measurements were made on August 7. Microclimate measurements on both sites were simultaneously carried out.Of the six mosses, five species were present in both the forest and on the clear-cut. One species, Entodon conncinus, was found only on the clear-cut. The growth rates of mosses varied among species and habitats. Hylocomium splendens grew the fastest while Dicranum assamicum had the slowest growth rate. Habitat conditions have a distinct effect on the growth of Hylocomium splendens, Dicranum assamicum and Thuidium lepidoziaceum and their growth rates were higher in forests than on clear-cuts. The growth rates of these mosses increased as their habitat approached the forest. Actinothuidium hookeri and Rhytidiadelphus triquetrus have moderate growth rates and is almost entirely independent of the type of habitat. The mosses can therefore be classified into habitat-sensitive and habitat-insensitive types. Analysis of microclimate characteristics shows that from May to July, the solar radiation level is lower and the environment is drier in the forest than those on the clear-cut. But a vapor pressure deficit (VPD) regime shows that the VPD in the morning is almost always lower in the forest than that on the clear-cut. With lower radiation and VPD, forests are more favorable to moss growth. For habitat-insensitive species, favorable micro-topographic factors might have offset the effect of habitat type.VPD is strongly correlated with the growth of mosses. Eco-physiological characteristics, such as poikilohydry, play an important role in the survival and growth of mosses under harsh climatic conditions. Temperature and humidity are two factors critical for seedling establishment in artificial regeneration processes in the subalpine areas of western Sichuan. Since the growth of mosses is a function of the two factors, moss growth rates can be used to indicate the more favorable habitats. Therefore, the status of moss growth can be used to indicate habitats potentially favorable to the growth of tree seedlings.
  • Assessment of the effect of a fully closed hillside afforestation mode on the natural forest
    HOU Lin, LEI Ruide, ZHANG Shuoxin
    2008, 3(2): 183-188. https://doi.org/10.1007/s11461-008-0023-x
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    The Huanglong Mountain forest zone is one of the major natural secondary forest zones in the southern Loess Plateau in Shaanxi Province, China. Since 1950, a mode of fully closed hillside afforestation (FHA) has been applied in the forest. On some special sites, the forest age exceeds 80 years. Pinus tabulaeformis forests form the most important vegetation cover in the warm temperate regions of China. Similarly, populations of P. tabulaeformis are dominant in existing forest ecosystems. Quercus liaotungensis, Syringa oblata, Populus davidiana, Prunus davidiana, Betula platyphylla and Toxicodendron vernicifluum can be occasionally found in the tree layer and shrub species are abundant. Based on the data collected from 31 plots and 93 soil samples, the state of health of the forest ecosystem is discussed and the appropriate FHA age has been determined. Twelve indices representing vegetation and soil properties in natural, secondary P. tabulaeformis forest ecosystems were generated by sensitivity analysis and an assessment index system for the FHA mode was established. According to the equal distance method, a clustering technique and five grades of an integrated index for evaluating the FHA mode were compartmentalized. The effect of the FHA mode on natural secondary P. tabulaeformis forests was evaluated by an integrated index method with the aid of an analytical hierarchy process (AHP). The results are as follows: values of the integrated index in the FHA mode of 16, 25, 30, 45, 60 and 75 year old stands were 7.25, 6.88, 7.82, 5.51, 4.78 and 2.79 respectively. With an increase over age of the FHA stands, the effect of the FHA mode deteriorated. We conclude that natural forests should not be protected in the FHA way after 45 years. At that stage, mixing suitable tree species, selection cutting and other silvicultural and management measures should be adopted.
  • Rainfall redistribution of a virgin forest and secondary forest in Northeast China
    CAI Tijiu, SHENG Houcai, CUI Xueqing
    2008, 3(2): 189-193. https://doi.org/10.1007/s11461-008-0022-y
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    A virgin Pinus koraiensis forest in the Xiaoxing’an Mountains was selected to study its rainfall redistribution effect via 97 rainfall occurrences during a growing season. The following results were obtained: 1) The canopy interception of the P. koraiensis virgin forest amounted to 98168 mm during a growing season (May to September), which was 19.6 per cent of the total rainfall and 1.3 times that of a secondary Betula platyphylla forest. Compared with other forest types in China (11.4%–36.5%), the ratio of the canopy interception in the virgin pine forest was at a medium level. 2) The throughfall of the virgin pine forest was 395.77 mm, which accounted for 78.7% of total precipitation, and the stem-flow was 8.78 mm, accounting for 1.74% of total precipitation. Compared with the secondary birch forest, the virgin pine forest had lower throughfall but higher stem-flow. 3) Cubic regression equations (p < 0.01) which describe the relation between throughfall, stem-flow and canopy interception in the virgin pine forest and rainfall in an open field were fitted. A linear regression equation (p < 0.01) was found to be a better fit for the relationship between throughfall of the secondary birch forest and rainfall outside the forest. Factors affecting throughfall and stem-flow were analyzed, with results providing a good reference to the study of rainfall redistribution in coniferous and broadleaved mixed forests.
  • Factors affecting transpiration of in a semi-arid region of the Loess Plateau
    ZHANG Weiqiang, ZHOU Yi, GAN Xianhua, WANG Yunqi, HE Kangning
    2008, 3(2): 194-199. https://doi.org/10.1007/s11461-008-0026-7
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    The effects of soil water and meteorological factors affecting transpiration of Pinus tabulaeformis were studied under different levels of soil water content to offer a scientific basis for increasing efforts in afforestation survival and management of soil water in forested land. Under artificial control methods for soil water and potting experiments, the transpiration rate (Tr) of P. tabulaeformis and environmental factors were measured using a portable steady porometer (Li-1600) and a speedy weight method (BP-3400) during a representative fine day in the growing season of 2004. The results indicated that the diurnal course of Tr and Rst of P. tabulaeformis displayed a double-peaked curve and a “W” curve under different levels of soil water content. Given a representative fine day, the Tr could be represented as a cubic relation with soil water content (SWC). The SWC which caused maximum Tr values of P. tabulaeformis was 17.7%, 19.8%, and 17.5% in July, August and October respectively. Tr was affected not only by physiological characteristics, but also by SWC and meteorological factors. Tr was significantly correlated with meteorological factors when the soil water was sufficient, but this correlation would decrease under conditions of serious water stress. Under such stress conditions, air temperature was the primary factor to affect Tr in July and August and photosynthetically active radiation (PAR) was the primary factor in October. When soil water is sufficient, the main factors affecting Tr were relative humidity (RH), air temperature (Ta) and leaf temperature (Tl) in July, August and October respectively.
  • Sap flow of and its relationship with environmental factors in a tropical montane rainforest
    ZHANG Ganghua, CHEN Bufeng, LIN Mingxian, NIE Jiezhu
    2008, 3(2): 200-205. https://doi.org/10.1007/s11461-008-0025-8
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    Using thermal dissipation and the ICT-2000TE equipment made in Australia, the sap flow of Castanopsis jianfengensis and various environmental factors were measured simultaneously in a mixed tropical montane rainforest at Jianfengling Nature Forest Reserve (18°36′N, 108°52′E, 860 m elevation) during the dry and rainy seasons of 2002. The results show that sap flow velocity of C. jianfengensis exhibited a mono-peak pattern on clear days and a multi-peak pattern on cloudy or rainy days. Sap flow velocity had significant positive correlations with solar radiation, air temperature, vapor pressure deficit and wind speed and a negative correlation with air relative humidity. In the dry season, sap flow velocity had a significant positive correlation with soil temperature and poor correlation with soil moisture; it was the opposite in the rainy season, indicating that precipitation clearly affected sap flow. Linear regression models between sap flow and environmental factors were established and were significant at the 0.005 level of probability. The mean transpiration rates of C. jianfengensis were 103.5 and 41.3 kg/d in our single tree and 1.94 and 0.77 mm/d in stand level in the dry and rainy season, respectively.
  • Forest biomass at Xiaolong Mountain in Gansu Province, China
    CHENG Tangren, FENG Jing, MA Qinyan, FENG Zhongke, LUO Xu, WANG Yutao, ZHANG Yanlin
    2008, 3(2): 206-212. https://doi.org/10.1007/s11461-008-0037-4
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    In order to accurately estimate the size of the carbon pool and the capacity of the carbon sink in the forested areas of Xiaolong Mountain in Gansu Province, we have established regression equations of organ biomass of eight tree species. We measured and investigated the biomass of different forest stand types based on data from 1259 standard sample plots and 836 standard sample trees. The results show that stand biomass, expressed in t·hm-2 for eight types of forest stands on Xiaolong Mountain, are as follows: Quercus aliena var. acuteserrata 84.05, Pinus tabulaeformis 62.44, Quercus variabilis 81.77, Populus sp. and Betula sp. combined 77.44, Larix sp. 69.00, Pinus armandii 70.07, Picea sp. 96.49 and Abies sp. 98.72. We also looked at other broad-leaved mixed forests. Our study shows that the biomass of a single tree of each tree species is closely related to the diameter at breast height (DBH) and to tree height. The biomass of single trees as well as stand volumes is closely related to average DBH, average tree height and to stand density.
  • Structural diversity of forest communities on Baihuashan Mountain, Beijing
    ZHENG Jingming, ZHAO Xiuhai, ZHANG Chunyu
    2008, 3(2): 213-218. https://doi.org/10.1007/s11461-008-0034-7
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    The structural diversity of forests on Baihuashan Mountain, Beijing, was surveyed by a plotless method combined with branch and leaf coverage estimation in the different layers. New structural indices were constructed, calculated and compared among different communities. On the basis of previous work, structural diversity of forest communities at the stand level was described by a vertical complexity index and a horizontal heterogeneity index. From a correlational analysis among the new indices and other commonly used biodiversity indices, we concluded that the new indices are closely related to a tree height inequality index and the Shannon-Wiener index of the tree and shrub layer, which indicated that the new indices were good at indicating structural diversity in the different forests on Baihuashan Mountain. The results show that, in natural forests, structural diversity of pioneer communities is much lower than in late successive communities. In plantations, structural diversity is determined by the stage of development and tree species. Tending would increase horizontal heterogeneity and decrease vertical complexity.
  • Molecular detection and drought resistance analysis of B-transgenic poplars ( × )
    LI Yiliang, SU Xiaohua, ZHANG Bingyu, ZHANG Zhiyi
    2008, 3(2): 226-231. https://doi.org/10.1007/s11461-008-0029-4
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    The propagation of drought-resistant transgenic poplars is one of the more effective ways to improve the ecological state of arid regions. The expression of SacB gene in transgenic lines of Populus alba × P. glandulosa was analyzed by a semi-quantitative RT-PCR. Drought resistance of these transgenic lines was evaluated by water stress trials in a greenhouse. Results showed that the mRNA transcription of SacB was found in all transgenic lines and fructan has accumulated in the leaves of these plants. The growth, biomass and leaf water content of some transgenic lines were significantly higher than those of the control plants under drought stress. Correlation analysis indicated that the said factors were significantly and positively related to the concentration of fructan in the leaves of the transgenic lines. Results revealed that the expression of SacB gene in transgenic poplars enhanced its resistance to water stress.
  • Allelopathic effects of essential oil from × . on pathogenic fungi and pest insects
    LIU Xiaoxiang, CHEN Qiubo, WANG Zhenhui, XIE Longlian, XU Zhi
    2008, 3(2): 232-236. https://doi.org/10.1007/s11461-008-0036-5
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    This study on the allelopathic effects and chemical components of the essential oil from Eucalyptus grandis × E. urophylla shows that the leaf oil emulsion of E. grandis × E. urophylla can inhibit the proliferation of pathogenic fungi Fusarium oxysporum, Pyriculerie grisea, Glorosprium musa rum and Phytophthora capsici. Pupation and feeding of the pest insects Spodopteralitura Fabricius and Helicoverpa armigera Hubner are shown to be affected with restraining effects which increase with the increasing levels of oil concentration. A GC/MS analysis of the leaf oil indicated that the main components, with a relative content of ≥3%, were allo-ocimene (43.22%), ?-pinene (13.63%), ?-terpinene (5.49%), (E)-3,7-dimethyl-2,6-octadien-1-ol (3.58%), ?-fenchyl alcohol (4.58%), and 2-amino-3,5-dicyano-6-(4-methoxyphenoxy)-pyridine (3.67%). Terpenes played an important role in the inhibitory effects of E. grandis × E. urophylla essential oil on pathogenic fungi and pest insects. Poor biodiversity of eucalyptus plantations is a function of allelopathy.
  • Electroantennogram responses of (Lepidoptera: Lasiocampidae) to six volatiles of
    YAN Shanchun, LIU Yingsheng, WANG Qi, CHENG Hong, ZHANG Jian, CHI Defu
    2008, 3(2): 237-242. https://doi.org/10.1007/s11461-008-0028-5
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    Dendrolimus superans is one of the important pests feeding on the needles of Larix gmelinii. Six standard compounds, (1R)-(+)-?-pinene, (1S)-(-)-?-pinene, ocimene, (1S)-(-)-?-pinene, R
  • Improvement in compatibility and mechanical properties of modified wood fiber/polypropylene composites
    DANG Wenjie, SONG Yongming, WANG Qingwen, WANG Weihong
    2008, 3(2): 243-247. https://doi.org/10.1007/s11461-008-0021-z
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    To improve the interfacial compatibility between wood fibers and polypropylene and the toughness of wood-fiber/polypropylene composites, maleic anhydride grafted polypropylene (PP-g-MAH) and maleic anhydride grafted styrene-ethylene-butadiene-styrene copolymers (SEBS-g-MAH) were used as modifiers. Mechanical properties of wood-fiber/polypropylene (WF/PP) composites were improved when PP-g-MAH or SEBS-g-MAH was added. When either of these copolymers was added, the composites had better interfacial compatibility than the unmodified composite. This was verified by scanning electron microscope (SEM) observations and dynamic mechanical analysis (DMA). The mechanical properties of the composites were significantly improved because of the good interfacial bonding between wood fibers and polypropylene when PP-g-MAH and SEBS-g-MAH were added.