Table of Content

20 November 2008, Volume 19 Issue 11

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Articles

Chemical components and their allelopathic effects of the volatiles from Larix principis-rupprechtii leaves and branches.

HAN Fen; WANG Hui; BIAN Yin-xia; LI Yong-bing

2008, 19(11):  2327-2332 . 

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The chemical components of the volatiles from the leaves and branches of Larix principis-rupprechtii were analyzed by GC-MS, with their allelopathic effects on the seed germination and growth of L. principis-rupprechtii itself investigated. The results indicated that the volatiles contained 20 major components, and the main constituents were terpenes and their oxidized derivatives, in which, there were 5 monoterpenes and 12 sesquiterpenes. The volatiles from the leaves and branches of L. principis-rupprechtii had significant inhibitory effects on the germination rate, germination speed index, radical length, hypocotyl length, and fresh mass of L. principis-rupprechtii itself, indicating that these volatiles contained potential allelochemicals, which might be related to the higher contents of terpenes and their oxidized derivatives. The allelopathic effects of the volatiles affected the regeneration of L. principis-rupprechtii, which should be a reason for the degeneration of artificial pure L. principis-rupprechti forest.

Natural inducing factors of peach bud dormancy and roles of Ca²⁺ in the dormancy inducetion.

WANG Hai-bo^1,2; WANG Xiao-di¹; CHENG Cun-gang¹; WANG Bao-liang¹; LI Min¹; GAO Dong-sheng²; LIU Feng-zhi¹

2008, 19(11):  2333-2338 . 

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Taking two-year-old peach tree of cv ‘Chunjie’ as test material, the natural inducing factors of peach bud dormancy and the roles of Ca²⁺ in the dormancy induction were studied. The results revealed that peach plant was very sensitive to short sunlight and/or natural low temperature. These two factors could induce growth cessation, dormancy, and freezing-resistance development, but their action mechanisms differed with each other. Short sunlight induced the dormancy first and the freezing-resistance then, whereas natural low temperature was in adverse. In case of the co-function of short sunlight and low temperature, i.e., under the natural condition, short sunlight was the main factor inducing growth cessation, dormancy, and freezing-resistance development, while natural low temperature was the secondary one. The inducement effect of short sunlight was closely related to the actions of Ca²⁺, because Ca²⁺ played a messenger role in the signal transduction of short sunlight. In the experiment of supplemental light, it was found that with the decrease of temperature, the Ca²⁺ had an increasing influx from the vacuole, intercellular space, and cell wall to the cytosol and nuclei. At the same time, plant growth slowed down and finally ceased, dormancy started then, and freezing-resistance developed, which indicated that as a messenger in the signal transduction of natural low temperature, Ca²⁺ played an important role in the inducement of growth cessation, dormancy, and freezing-resistance development by natural low temperature.

Dendrochronology of Chinese pine in Mulan-Weichang, Hebei Province: A primary study.

CUI Ming-xing^1,2; HE Xing-yuan¹; CHEN Wei¹; CHEN Zhen-ju¹; ZHOU Chang-hong³; WU Tao⁴

2008, 19(11):  2339-2345 . 

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Dendroclimatic methods were used to investigate the relationships between the growth of Chinese pine (Pinus tabulaeformis Carr.) and the climatic parameters in Mulan-Weichang of Hebei Province. The results showed that Chinese pine presented high sensitivity to climatic changes, and its earlywood width showed the highest sensitivity. There was a significant negative correlation between the tree-ring width chronology of Chinese pine and the air temperature in May-June. The precipitation and relative humidity in June had strong positive effects on the growth of earlywood, the precipitation from September to next September had significant positive effects on Chinese pine growth, and the relative humidity in winter more strongly affected the growth of latewood than of earlywood. There was a definite correlation between the tree-ring width chronology of Chinese pine and the large scale climate fluctuation. From 1951 to 2006, the increase of air temperature in study area was significant, and the sensitivity of Chinese pine to the variations of local temperature and precipitation decreased, presenting an inverse transforming trend with increasing temperature. Greater differences were observed between the reconstructed and observed data of mean temperature in May-June in a century scale, suggesting that the tree-ring growth of Chinese pine in study area had a greater fluctuation of sensitivity to the variation of climatic factors.

Water-holding characteristics of coniferous forest litters in west Qinling Mountains.

CHANG Ya-jun¹; CAO Jing¹; MA Jian-wei²; CHEN Qi¹; ZHAO Lin¹

2008, 19(11):  2346-2351 . 

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By the methods of field survey and soaking extraction, the storage, water-holding capacity, water-holding rate, and water-absorption rate of the litters in Larix principis-ruprechtii, Larix kaempferi, Picea asperate, and Picea abies plantations in west Qinling Mountains were studied. The results showed that the litter storage in the four similar aged coniferous forests decreased in the order of P. asperate (29.81 t·hm^-2)> P. abies (26.17 t·hm^-2)> L. kaempferi(13.30 t·hm^-2)>L. ruprechtii (8.46 t·hm^-2). The water-holding capacity and water-holding rate of the litters at different decomposition degree changed logarithmically with soaking time while the water-absorption rate assumed a power function, but all the test water-holding characteristics had less correlation with forest type and litter decomposition degree. Under the four coniferous forests, the litters in semi-decomposed layer had a stronger water-holding capability than those in decomposed layer, and the water-holding capability of the litters under larch forest was stronger than that under spruce forest.

Dynamics of autumn phenophase of woody plants in Beijing region in 1962-2007.

ZHONG Shu-ying^1,2; ZHENG Jing-yun¹; GE Quan-sheng¹

2008, 19(11):  2352-2356 . 

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The responses of the autumn phenophase of 20 woody plants to climate warming in Beijing in 1962-2007 were analyzed by using the plant phenological data and the meteorological data obtained from Chinese Phenology Observation Network of Chinese Academy of Sciences. The results showed that in Beijing region, the end date of autumn defined by phenology was extended remarkably at an average rate of 3.2 d·10 a^-1, while the onset of autumn defined by phenology remained essentially unchanged, resulting in a 14 d prolongation in autumn in 1962-2007. The timing of first leaf coloring change for the woody plants showed an average delaying rate of 4.9 d·10 a^-1, and the main affecting factor was the mean minimum temperature. Climate warming was probably the main reason for the delaying trend in autumn phenophase of woody plants in Beijing during the study period.

Seasonal variation and temperature sensitivity of soil respiration under different plant communities along an elevation gradient in Wuyi Mountains of China.

SHI Zheng^1,4;WANG Jia-she²;HE Rong^1,3;WANG Guo-bing¹;FANG Yan-hong²;XU Zi-kun²;ZHANG Zeng-xin¹;RUAN Hong-hua¹

2008, 19(11):  2357-2363 . 

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Taking the National Nature Reserve in Wuyi Mountains as experimental site, the seasonal variation and temperature sensitivity of soil respiration under four plant communities along an elevation gradient were studied, with their relations to the main environmental factors analyzed. The results showed that the soil respiration under the four plant communities had the same seasonal pattern, with the maximum (3.10-6.57 μmol CO₂·m^-2·s^-1) occurred in summer and the minimum (0.27-1.15 μmol CO₂·m^-2·s^-1) in winter. Soil respiration rate had a significant exponential correlation with soil temperature, but its correlations with soil moisture and litter input differed with plant communities. The Q₁₀ value of soil respiration was higher at high elevation than at low elevation. In mid-subtropical regions, the seasonal variation of soil respiration at different elevations was mainly controlled by soil temperature, indicating that in the case of global warming in the future, soils at higher elevation might release more CO₂ to the atmosphere.

Relationships between belowground biomass of alpine grassland and environmental factors along an altitude gradient.

LI Kai-hui¹;WANG Wan-lin²;HU Yu-kun¹;GAO Guo-gang^1,3;GONG Yan-ming^1,3;YIN Wei^1,3

2008, 19(11):  2364-2368 . 

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Taking Bayanbulak alpine grassland on the southern slope of Tianshan Mountain, Xinjiang as test object, the relationships between belowground biomass and environmental factors along an altitude gradient were analyzed. The results showed that with increasing altitude, the belowground biomass of alpine steppe dominated by Stipa purpurea and Festuca ovina, alpine steppe meadow dominated by Kobresia capillifolia and S. purpurea, and alpine meadow dominated by Carex stenocarpa, Alchemilla tianschanica, and K. capillifolia all increased gradually. There was a significant positive correlation between altitude and belowground biomass (P<0.01). The belowground biomass decreased with soil deep and with a ‘T’ shape distribution. In alpine steppe, alpine steppe meadow, and alpine meadow, the belowground biomass in 0-10 cm soil layer occupied 68.1%, 84.1% and 86.7% of the total, respectively. The belowground biomass of the alpine grassland was negatively correlated with air temperature and positively correlated with relative humidity and soil water content (P<0.01), but had no significant correlation with soil organic matter, available nitrogen, and pH value.

Effects of leaf damage and sediment type on compensatory growth of submerged macrophyte Vallisneria spiralis.

LI Kuan-yi^1,2;LI Yan-min^1,2;LIU Zheng-wen^1,3

2008, 19(11):  2369-2374 . 

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Through a 2 × 2 factorial outdoor experiment, the effects of leaf damage and sediment type on the compensatory growth of submerged macrophyte Vallisneria spiralis were examined. The results showed that leaf damage and sediment type had significant effects on the cumulative biomass, biomass allocation, and ramet number of V. spiralis. Compared with undamaged plant, the strongly damaged one had a decrease of cumulative biomass and ramet number and an increase of biomass allocation, but no evident difference was observed between weakly damaged and undamaged plants. The cumulative biomass of undamaged and strongly damaged plants was lower in infertile sediments (bank sediment) than in fertile sediments (lake sediment), but that of weakly damaged plant was almost the same in the two sediments. The biomass allocation and ramet number of V. spiralis were higher in bank sediment than in lake sediment. Leaf damage and sediment type also affected the relative growth rate (RGR) of V. spiralis. Leaf damage resulted in an increase of RGR, but the difference of RGR between weak damage and strong damage was not evident. The RGR of undamaged and strongly damaged plants was significantly higher in lake sediment than in bank sediment, but that of weakly damaged plant was almost the same in the two sediments. The mechanisms of the compensatory growth of V. spiralis were discussed.

Effects of long-term fertilization on soil particulate organic carbon and nitrogen in a wheat-maize cropping system.

GONG Wei^1,2;YAN Xiao-yuan¹;CAI Zu-cong¹;WANG Jing-yan²;HU Ting-xing²;GONG Yuan-bo²;RAN Hua²

2008, 19(11):  2375-2381 . 

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0-20 cm soil samples were collected from an 18-year wheat-maize rotation field on the North China Plain to study the effects of long-term fertilization on the contents and storages of soil particulate organic carbon (POC), particulate organic nitrogen (PON), incorporated organic carbon (IOC), and incorporated organic nitrogen (ION). The long-term fertilization experiment was designed to include 7 treatments, i.e., chemical NPK (NPK), organic manure (OM), 1/2 organic manure plus 1/2 chemical NPK (1/2OMN), chemical NP (NP), chemical PK (PK), chemical NK (NK), and control (CK). After 18 years experiment, all the fertilization treatments showed higher contents of soil POC, PON, IOC and ION, higher proportions of soil POC to soil total organic carbon (TOC) and of soil PON to soil total nitrogen (TON), and higher C/N ratio of soil particulate organic matter. The storages of soil POC and PON under fertilization treatments were increased by 11.7%-196.8% and 13.0%-152.2%, respectively, compared with the control. The contribution of soil POC to the increased storage of soil TOC ranged from 31.5% to 67.3%, and that of soil PON to the increased storage of soil TON ranged from 14.3% to 100.0%. The storages of soil IOC and ION under fertilization treatments increased by 2.0%-75.0% and 0.0%-69.8%, respectively, compared with the control. Among the fertilization treatments, treatment OM had the highest storages of soil POC, PON, IOC and ION, followed by treatment 1/2OMN, and the treatments of applying chemical fertilizers alone. Balanced application of chemical fertilizers (treatment NPK) showed higher storages of soil POC, PON, IOC and ION than imbalanced application (treatments NP, PK, and NK). It was suggested that applying organic manure or its combination with chemical NPK and the balanced application of chemical NPK could be the keys for the increase of soil POC, PON, IOC and ION contents and storages.

Effects of application time and basal/topdressing ratio of nitrogen fertilizer on the spatiotemporal variation of soil NO₃^--N and NH₄⁺-N contents and the grain yield and its quality of wheat.

WU Ji^1,2,3;GUO Xi-sheng^1,2,3;YANG Xiao-hu⁴;HUANG Xiao-rong²

2008, 19(11):  2382-2387 . 

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Field trials were conducted to study the effects of different application time and basal / topdressing ratio of nitrogen fertilizer on the spatiotemporal variation of soil NO₃^--N and NH₄⁺-N contents and the grain yield and its quality of wheat. The results showed that soil NO₃^--N and NH₄⁺-N contents decreased with increasing soil depth. Both the application time and the basal / topdressing ratio of nitrogen fertilizer had significant effects on the NO₃^--N and NH₄⁺-N contents in 0-20 cm soil layer. Compared with basal application, later fertilization and higher topdressing ratio could promote the nitrogen uptake by wheat plant and increase the plant nitrogen recovery significantly, decrease the soil nitrogen recovery during wheat growth, and improve the grain quality significantly, while had less effects on the grain yield. Topdressing too much nitrogen fertilizer at booting stage could result in a significant decrease of grain yield. Under the condition of this experiment, the optimal nitrogen fertilization mode for good wheat grain yield and its quality and good ecological benefits was 5 ∶3∶2 of basal application ∶topdressing at jointing stage ∶topdressing at booting stage.

Effects of nitrogen application rate and post-anthesis soil moisture content on the flag leaf senescence and kernel weight of wheat.

ZHAO Chang-xing^1,2;MA Dong-hui¹;WANG Yue-fu¹;LIN Qi¹

2008, 19(11):  2388-2393 . 

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A rain-proof pool culture experiment was conducted to study the effects of nitrogen (N) application rate and post-anthesis soil moisture content on the flag leaf senescence and kernel weight of wheat. The results indicated that in all N fertilization treatments, the flag leaf SPAD value, soluble protein content, SOD and CAT activities, and photosynthetic rate decreased in the order of 60%-70% >80%-90%>40%-50% post-anthesis soil moisture content, while the MDA content decreased in reverse order, suggesting that over high or low post-anthesis soil moisture content could cause the early senescence of flag leaves, impact grain filling, and decrease kernel weight. Under the same post-anthesis soil moisture content, the SPAD value, soluble protein content, SOD and CAT activity, and photosynthetic rate increased, while the MDA content decreased with increasing N application rate, indicating that increased N fertilization could postpone the senescence of wheat flag leaves. However, over N application was not favorable to the increase of kernel weight, especially under the condition of post-anthesis soil moisture deficiency. It was concluded that appropriate N application and post-anthesis soil moisture content control could postpone the plant senescence and increase the kernel weight of wheat.

Regulation effects of grafting on cinnamic acid and vanillin in eggplant root exudates.

CHEN Shao-li¹;ZHOU Bao-li¹;WANG Ru-hua²;FU Ya-wen¹

2008, 19(11):  2394-2399 . 

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Cinnamic acid and vanillin are the allelochemicals commonly existed in eggplant root exudates. With pot culture experiment, the regulation effects of grafting on the cinnamic acid and vanillin in eggplant root exudates were studied, and the results showed that grafting decreased the amount of the two substances, especially of vanillin, in eggplants root system. The maximum reduction amount of cinnamic acid reached 68.96%, and that of vanillin reached 100%. Under the stress of exotic cinnamic acid and vanillin, especially of exotic cinnamic acid, grafting relieved the autotoxicity of the two substances on eggplants. Compared with own-rooted eggplant, grafted eggplant had a higher plant height and a larger stem diameter, its leaf chlorophyll content increased by 5.26%-13.12%, root electric conductivity and MDA content decreased, and root SOD activity enhanced.

Soil hydraulic properties and their influences on soil water content under different land uses in Liudaogou watershed of Loess Plateau.

LIU Chun-li^1,2,3;SHAO Ming-an¹

2008, 19(11):  2400-2407 . 

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By the method of cross correlation coefficient in geo-statistics, this paper studied the soil hydraulic properties and their influences on soil water distribution under four land uses, i.e., farmland, waste-grassland, forestland, and alfalfa land in Liudaogou watershed of Loess Plateau. The results showed that farmland soil and waste-grassland soil had the similar physical characteristics, as did forestland soil and alfalfa land soil. For any given soil suction, farmland soil had the highest water content, while forestland soil had the lowest one. The opposite was observed for the saturated hydraulic conductivity of soil water. In forestland and alfalfa land, soil water content increased with increasing depth during water consumption period, but decreased with soil depth at any other time. The influence range of saturated hydraulic conductivity on soil water content depended on soil water condition. During the compensation period of soil water, the influenced lag distance of saturated hydraulic conductivity to water content was 0-40 cm, and that of water content to saturated hydraulic conductivity was 0-50 cm; while during the stable period of soil water, the influenced lag distances of saturated hydraulic conductivity and water content were both 0-60 cm. There were positive correlations between the two properties under all land uses during these two periods. During water consumption period, saturated hydraulic conductivity was positively correlated with soil water content in farmland and waste-grassland. The influence range of saturated hydraulic conductivity to water content was about 0-80 cm, while that of water content to saturated hydraulic conductivity was 0-60 cm. However, negative correlation was observed in forestland and alfalfa land, and the influence ranges were also about 0-60 cm.

Correlations between spectral characteristics and diurnal CO₂ budget of winter wheat field on Loess Plateau.

LI Shuang-jiang^1,2;LIU Zhi-hong^1,3;LIU Wen-zhao¹;SUHIRO Takahashi⁴;ATSUSHI Higuchi⁵;TETSUYA Hiyama⁶;YOSHIHIRO Fukushima⁴

2008, 19(11):  2408-2413 . 

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Based on the continuous observation on the spectral reflectance and CO₂ flux during the whole growth period of winter wheat, the correlations between the variations of spectral characteristics and the diurnal CO₂ budget of winter wheat field on Loess Plateau were analyzed. The results showed that the spectral reflectance at different wavelengths and the NDVI changed with the growth stages of winter wheat, and the diurnal spectral reflectance changed with solar altitude angle, with the wavelengths at which the reflectance changed most being at 550 nm and 700-1 050 nm. At the same time period of different growth stages, the spectral reflectance changed little at 350-670 nm but varied greatly at 700-1 050 nm. The red edge position shifted to longer wavelengths at seedling and tillering stages and by the end of wintering while to shorter wavelengths at the beginning of wintering, but the shift to shorter wavelengths was not obvious at ripening stage. No spectrum shift was observed at other growth stages. The diurnal NDVI changed in U-shape, reaching to the minimum at about 13:00 and fluctuating after 16:00, and the change pattern could be fitted by a parabola. Therefore, for winter wheat field, the best time for remote sensing observation should be selected at about 13:00 when the NDVI changed little, except in winter. After the 140th day of seeding, the reflectance and NDVI at 11:00 were symmetrical, and NDVI changed in M-shape, being able to be simulated by a quartic polynomial. There was a significant negative correlation between the NDVI and the diurnal CO₂ budget during the whole growth period of winter wheat, but the correlation was weaker around midday.

Light competition and productivity of agroforestry system in loess area of Weibei in Shaanxi.

PENG Xiao-bang¹;CAI Jing^1,4;JIANG Zai-min^2,4;ZHANG Yuan-ying³;ZHANG Shuo-xin^1,4

2008, 19(11):  2414-2419 . 

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Agroforestry is the most effective way for the restoration of disturbed land on Loess Plateau and the development of poorly local economy. Taking the tree-based intercropping systems of walnut or plum with soybean or pepper in the loess area of Weibei as test objects, the photosynthesis, growth, and yield of soybean (Qindou 8) and pepper (Shanjiao 981) in the systems were studied. The results showed that the photosynthetic active radiation (PAR), net photosynthetic rate (P_n), growth, and yield of individual soybean or pepper plants were significantly decreased, with the effects increased with decreasing distance from tree rows. Leaf water potential was not significantly or poorly correlated with the P_n, growth, and yield of the two crops. However, there were significant positive correlations between the soil moisture content in 10-20 cm layer and the biomass and yield of soybean, and the above-ground biomass of pepper. PAR was highly correlated with the yield of both crops, which indicated that light competition was one of the key factors leading to the decrease of crop yield.

Oxygen consumption rate and effects of hypoxia stress on enzyme activities of Sepiella maindron.

WANG Chun-lin;WU Dan-hua;DONG Tian-ye;JIANG Xia-min

2008, 19(11):  2420-2427 . 

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The oxygen consumption rate and suffocation point of Sepiella maindroni were determined through the measurement of dissolved oxygen in control and experimental respiration chambers by Winkler’s method, and the changes of S. maindroni enzyme activities under different levels of hypoxia stress were studied. The results indicated that the oxygen consumption rate of S. maindroni exhibited an obvious diurnal fluctuation of ‘up-down-up-down’, and positively correlated with water temperature (16 ℃-28 ℃) and illumination (3-500 μmol·m^-2·s^-1) while negatively correlated with water pH (6.25-9.25). With increasing water salinity from 18.1 to 29.8, the oxygen consumption rate had a variation of ‘up-down-up’, being the lowest at salinity 24.8. Female S. maindroni had a higher oxygen consumption rate than male S. maindroni. The suffocation point of S. maindroni decreased with its increasing body mass, and that of (38.70±0.52) g in mass was (0.9427±0.0318) mg·L^-1. With the increase of hypoxia stress, the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) decreased after an initial increase, lipase activity decreased, protease activity had a variation of ‘decrease-increase-decrease’, and lactate dehydrogenase (LDH) activity had a trend of increasing first and decreasing then. The enzyme activities were higher under hypoxia stress than under normal conditions.

Distribution of picophytoplanktons in Qingdao offshore and its adjacent waters in winter.

WANG Min;LIANG Yan-tao;BAI Xiao-ge;JIANG Xue-jiao;WANG Fang;QIAO Qian

2008, 19(11):  2428-2434 . 

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Picophytoplankton (0.2-2.0 μm in size) is the smallest group of autotrophic plankton, being abundant and widespread in the world ocean and playing an important role in the organic matter cycling in ocean. By the method of epifluorescence microscopy (EFM), the abundance and its spatial and diurnal variations of the picophytoplanktons in Qingdao offshore and its adjacent waters in winter were investigated. The results showed that in the study area in winter, phycoerythrin-rich (PE) Synechococcus cells were dominant, followed by Picoeukaryote (Euk) cells, while the abundance of phycocyanin-rich (PC) Synechococcus cells was low and no Prochlorococcus (Pro) cells were observed. The abundance of Synechococcus (Syn) and Euk varied from 8.97×10³ to 1.95×10⁵ cells·ml^-1(averaged 4.67×10⁴ cells·ml^-1) and from 1.95×10² to 1.01×10⁴ cells·ml^-1(averaged 2.39×10³ cells·ml^-1), respectively. There was a high-value of Syn abundance in Jiaonan offshore and a low-value in Jimo and southeast Laoshan off-shores, while a high-value of Euk abundance in Rizhao offshore and a low-value in Laoshan offshore. No significant difference was observed in the vertical distribution of Syn and Euk abundance among four water layers (P>0.05) at a continuous station located in the center of Jiaozhou Bay, the abundance had an obvious diurnal fluctuation. Pearson correlation analysis indicated that Syn was positively correlated with water temperature and electrical conductivity (P<0.01) but negatively correlated with dissolved oxygen concentration (P<0.01), and Euk was negatively correlated with water salinity and dissolved oxygen concentration. In the study area in winter, picophytoplankton contributed about 20％ to the total phytoplanktonic biomass.

Phytoplankton assemblages on the continental shelf of East China Sea in autumn 2006.

WANG Dan¹;SUN Jun¹;AN Bai-zheng¹;NI Xiao-bo²;LIU Su-mei³

2008, 19(11):  2435-2442 . 

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Based on the survey from November 19 to December 24, 2006, the species composition, assemblage structure, and cell abundance of phytoplankton on the continental shelf of East China Sea (24.0°-32.0°N，120.0°-128.0°E) were studied. The phytoplankton flora in the survey area included 145 taxa, belonging to 64 genera of 4 classes (including uncertain species). Bacillariophyta was the dominant functional group, followed by Pyrrophyta. The dominant species in turn were Thalassionema nitzschioides, Thalassiosira rotula, Leptocylindrus danicus, Guinardia striata, Pseudo-nitzschia pungens, and Trichodesmium thiebautii. The cell abundance of the phytoplankton ranged from 0.09 to 35.11cells·ml^-1, with an average of 4.92 cells·ml^-1. In the autumn, Bacillariophyta abundance discriminated the surface pattern of the phytoplankton, and the higher abundance area was located at the northeast part of offshore regions, with the cell abundance reached 30 cells·ml^-1. On the whole, the cell abundance of Bacillariophyta and Pyrrophyta was concentrated in surface water, and it reduced rapidly from surface layer down to the bottom. According to the section distribution, the phytoplankton mainly concentrated in surface water, and also, in the middle and bottom layers for some stations. The average of Shannon-Wiener indices of phytoplankton assemblage was 2.80, with the higher values occurred in the northeast and southeast of the survey area. The average of Pielou’s evenness of phytoplankton assemblage was 0.81, and the higher value was located at the middle of the survey area. The surface horizontal distribution of Shannon-Wiener indices was coincided with that of phytoplankton cell abundance. According to the Pearson correlation analysis, the factors that significantly affected the growth of the phytoplankton were nitrite, dissolved organic nitrogen (DON), and temperature.

Spatial distribution of macroinvertebrates in Xiangxi River.

JIANG Wan-xiang^1,2;CAI Qing-hua¹;TANG Tao¹;WU Nai-cheng¹;FU Xiao-cheng¹;LI Feng-qing¹;LIU Rui-qiu¹

2008, 19(11):  2443-2448 . 

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An investigation was made from July 2005 to June 2006 to understand the spatial distribution of macroinvertebrates in Xiangxi River, the largest tributary in Hubei portion of Three Gorges Reservoir. The results showed that Ephemeroptera baetis spp., Ephemeroptera epeorus spp., and Plecoptera nemoura spp. were the dominant taxa. There existed greater differences in the habitat characters and in the community structure of macroinvertebrates among the major tributaries of Xiangxi River, and the relative abundance of functional feeding groups could reflect the characters of different habitats. A comparison of the diversity of dominant taxa and their tolerance towards pollution among the major tributaries showed that Jiuchong River had the best habitat, followed by the main stream of Xiangxi River, and Gaolan River and Gufu River. Canonical correspondence analysis showed that the NH₄⁺-N concentration in the main stream of Xiangxi River, the pH, turbidity, water depth, SiO₂, conductance, and alkalinity in Jiuchong River, the turbidity in Gaolan River, and the NH₄⁺-N and NO₃^--N concentrations in Gufu River had significant impact on the community structure of macroinvertebrates.

Relative fitness of Tetranychus cinnabarinus resistant strains at different temperatures.

HE Lin;XUE Chuan-hua;ZHAO Zhi-mo;WANG Jin-jun

2008, 19(11):  2449-2454 . 

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Based on resistance selection, the life tables of abamectin-resistant (AbR), fenpropathrin-resistant (FeR), and susceptible (S) strains of Tetranychus cinnabarinus at 15 ℃, 20 ℃, 25 ℃, 28 ℃, 31 ℃, 34 ℃, and 36 ℃ were constructed, and the development duration, fertility, and intrinsic rate of increase (r_m) of the strains were compared, aimed to understand the relative fitness of T. cinnabarinus resistant strains at different temperatures. The results indicated that compared with S strain, AbR and FeR strains had longer development duration at 15 ℃ but lower fertility at 20 ℃-28 ℃, and their relative fitness (represented by r_m) was smaller at 15 ℃ but similar at 20 ℃-31 ℃. For AbR and FeR strains, the fitness cost was moderate at 15℃ but lower at 20 ℃-31 ℃. However, at high temperatures (≥34 ℃), FeR strain possessed remarkable fitness cost while AbR strain showed better fitness.

β diversity of successional series in mash communities of Sanjiang Plain,China.

XING Fu^1,2;Lü Xian-guo¹;NI Hong-wei³;GAO Yu-hui³;XU Kun²;YU Li-li²;ZHANG Liang²

2008, 19(11):  2455-2459 . 

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Four typical successional series in the marsh communities of Sanjiang Plain were selected to investigate the changes of their β diversity. The results indicated that from the ‘starting community’ to the‘end community’, which had the most and the least moisture level in the series, respectively, the similarity coefficient between each community and ‘starting’ community decreased with decreasing moisture gradient and increasing horizontal distance. The species turnover speed among the communities in each series had an increasing trend from lowland to upland. In the process of succession, the general trend was that the total number of plant species increased while the common species decreased, with the β diversity between communities increased gradually. The analysis of succession mechanism supported the ‘initial floristics composition hypothesis’, and the plant Calamagrostis angustifolia would intensify its dominance in the mash of Sanjiang Plain.

Evaluation of view points in forest park based on landscape sensitivity.

ZHOU Rui^1,2;LI Yue-hui¹;HU Yuan-man¹;LIU Miao¹

2008, 19(11):  2460-2466 . 

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Based on topographical characteristics, five factors including comparative slope, comparative distance, mutual visibility, vision probability, and striking degree were chosen to assess the landscape sensitivity of major view points in Houshi National Forest Park. Spatial analysis in GIS was used for exploring the theory and method of landscape sensitivity of view points. The results showed that in the Park, there were totally 23 view points, but none of them reached up to class I. Among the 23 points, 10 were of class Ⅱ, accounting for 43.5% of the total, 8 were of class Ⅲ, accounting for 34.8%, and 5 were of classes IV and V, accounting for 21.7%. Around the view points of class Ⅱ, the landscape should be strictly protected to maintain their natural feature; around the view points of class III, human-made landscape points should be developed according to the natural landscape feature, and wide tourism roads and small-size buildings could be constructed but the style of the buildings should be harmonious with surrounding nature landscape; while around the view points of classes IV and V, large-size multifunctional items and roads could be built to perfect the natural landscape. Through the multi-perspective and quantitative evaluation of landscape sensitivity, this study enriched the theory of landscape visual assessment and landscape apperception, and provided scientific base and direction for the planning and management of forest parks and other tourism areas.

Relationships between landscape structure and rocky desertification in karst region of northwestern Guangxi.

ZHANG Xiao-nan^1,2,3;WANG Ke-lin^1,2;CHEN Hong-song^1,2;ZHANG Wei^1,2

2008, 19(11):  2467-2472 . 

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By using canonical correspondence analysis (CCA), sixteen landscape indices were adopted to quantitatively analyze the relationships between the landscape structure and rocky desertification in karst region of Huanjiang County, Guangxi Province. The results showed that the first and the second ordination axis of CCA were strongly correlated to the factors of average patch area, average dry land patch area, landscape shape index, and landscape aggregation index. The potential rocky desertification in the region was highly positively correlated with the average dry land patch area and the average fractal dimensions of dry land and shrub land, but negatively correlated with the patch numbers of dry land. Light rocky desertification had obvious positive correlations with the fractal dimension index, average fractal dimension of unused land, and patch numbers of shrub land; while moderate and strong rocky desertification had high positive correlations with the average unused land patch area but negative correlation with the average fractal dimension of shrub land. To some extent, rocky desertification degree might be represented by the values of landscape indices. The gradient variation in karst rocky desertification along landscape structure was clearly presented by the results of CCA.

Evaluation of ecosystem resilience in the regions across Qinghai-Tibet railway based on GIS.

GAO Jiang-bo¹;ZHAO Zhi-qiang^1,2;LI Shuang-cheng¹

2008, 19(11):  2473-2479 . 

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Based on GIS technique and the methods of mean-squared deviation weight decision and catastrophe progression, a more clear definition and associated evaluation for ecosystem resilience were given, with a case study in the regions across Qinghai-Tibet railway by using the indices of plant community coverage, species diversity, and biomass. It was shown that the areas with high ecosystem resilience were mainly located in the Qilian Mountain meadow grassland, Huangshui Valley needle-leaved and deciduous broad-leaved forest, and south Tanggula Mountain kobresia swamp meadow, while those with the lowest resilience were in the central part of Qaidam Basin, and the Kunlun Mountains. Most areas in the regions had higher or medium ecosystem resilience, with a trend of that in the south of Kunlun Mountains, the resilience in the north of the railway was lower, while in the east of Qaidam Basin (especially in the Qinghai Lake area), the resilience was lower in the south than in the north of the railway. Through the evaluation of ecosystem resilience, the key issues in the process of ecological resilience could be found, and corresponding effective measures would be pointed out to manage alpine ecosystems. Moreover, combining with the evaluation of vulnerability, scientific basis for regional development could be provided to avoid or mitigate the negative effects of human activities on eco-environment.

Degradation of soil phenolic acids by Phanerochaete chrysosporium under continuous cropping of cucumber.

XU Shu-xia;ZHANG Shi-min;YOU Xiao-yan;JIA Xin-cheng;WU Kun

2008, 19(11):  2480-2484 . 

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With inoculation of Phanerochaete chrysosporium in shaking flask, this paper studied the degradation of soil p-hydroxybenzoic acid, vanillic acid and ferulic acid under continuous cropping of cucumber, and evaluated the effect of this inoculation in overcoming the continuous cropping obstacle of cucumber. The results showed that after 8 days of inoculation, more than 99% of soil phenolic acids were decomposed by P. chrysosporium. Compared with the control, the contents of soil phenolic acids under 7 years continuous cropping of cucumber declined, with a degradation rate of 54.46%. After inoculating P. chrysosporium, soil fungal population and the plant height, stem width, and fresh and dry mass of cucumber had less change, but the occurrence of cucumber root diseases reduced greatly, with the relative disease index of wilt and root knot nematode declined by 10.2% and 14.6%, respectively. It was suggested that inoculation of P. chrysosporium had definite effect in overcoming the continuous cropping obstacle of cucumber.

Effects of elevated ozone on rice (Oryza sativa L.) leaf lipid peroxidation and antioxidant system.

ZHANG Wei-wei;ZHENG Fei-xiang;WANG Xiao-ke;FENG Zhao-zhong;OUYANG Zhi-yun;FENG Zong-wei

2008, 19(11):  2485-2489 . 

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With rice (Oryza sativa L.) cultivar 3694 Fan as test material, and by using open top chambers, the effects of different ozone (O₃) concentration on the leaf soluble protein content, lipid peroxidation, and antioxidant system were applied. Three treatments were applied, i.e., charcoal-filtered air (CF, 20 nl O₃·L^-1), non-filtered ambient air (NF, 40 nl O₃·L^-1), and elevated O₃ (EO, 75 nl O₃·L^-1). The results showed that there were no significant differences in the test variables between treatments CF and NF. Compared with CF, EO induced a significant decrease of soluble protein content and significant increases of H₂O₂ and ASA contents and SOD, CAT and POD activities. In treatment EO, the SOD, CAT and POD activities increased by 93.7%, 39.9% and 312.4%, respectively, as compared with treatment CF, while the APX activity tended to increase at first and decrease then. MDA content had no significant differences among the treatments, indicating that leaf antioxidant system could significantly prevent the lipid peroxidation induced by elevated O₃, and rice cultivar 3694 Fan could resist O₃ to some extent.

CH₄ absorption and its affecting factors in a wheat field with conservation tillage.

ZHAO Jian-bo;LI Zeng-jia;CHI Shu-jun;NING Tang-yuan;GU Shu-bo;QIU Li-qun;WANG Yun;JIANG Xiao-dong

2008, 19(11):  2490-2496 . 

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In order to understand the relationships between CH₄ fluxes and its affecting factors in a wheat field with conservation tillage, the CH₄ fluxes in two wheat fields, one with conservation tillage and the another with conventional tillage, were measured in situ by static chamber-GC method, with soil temperature and soil moisture and inorganic nitrogen contents determined at the same time. The results showed that these two fields had an obvious and similar seasonal variation pattern of CH₄ fluxes, but the average and seasonal CH₄ absorption fluxes differed significantly. In the growth period of wheat, the fields were the sink of CH₄, and the CH₄ absorption fluxes was in the order of conventional tillage with no straw returning (CN)>conventional tillage with straw returning (CS)>subsoiling with straw returning (PS)>harrowing with straw returning (HS)>rotary tillage with straw returning (RS)>no tillage with straw covered (NS). Comparing with conventional tillage, conservation tillage reduced the CH₄ absorption fluxes. In conservation tillage, the CH₄ absorption fluxes was positively correlated with soil temperature but negatively correlated with soil moisture content; while in conventional tillage, the CH₄ absorption fluxes had no significant correlations with the two factors. In all treatments, there was a significant negative correlation between CH₄ absorption fluxes and soil NH₄⁺-N content.

Simulation of rice canopy evapotranspiration and water use efficiency under free-air CO₂ enrichment.

WANG Ming-na^1,2;LUO Wei-hong³;SUN Yan-kun²;ZHU Jian-guo¹

2008, 19(11):  2497-2502 . 

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By using FACE system, the microclimate in rice canopy and related physiological indices were observed continuously from the elongation to the maturing stage of rice growth, and the effects of FACE on the rice canopy evapotranspiration and water use efficiency were studied and simulated with energy balance analysis. The results showed that using P-M equation to describe the quantitative relationships of rice leaf stomatal conductance with photosynthetically active radiation (PAR) and vapour pressure deficit (VPD) could better simulate rice canopy evapotranspiraton under FACE and ambient conditions. During observation period, the total water use of rice in FACE plot had a 10 mm decrease, compared with that in control plot. Considering of the 12% increase of total biomass, the water use efficiency of rice under FACE condition was increased by 12%.

Effects of NaCl stress on Hovenia dulcis and Gleditsia sinensis seedlings growth, chlorophyll fluorescence, and active oxygen metabolism.

FENG Lei^1,2;BAI Zhi-ying³;LU Bing-she¹;CAI Sheng-wen¹;FENG Li-na¹

2008, 19(11):  2503-2508 . 

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With potted Hovenia dulcis and Gleditsia sinensis seedlings as test materials, their plant growth, chlorophyll fluorescence characteristics, and active oxygen metabolism under stress of different concentration (0, 0.15%, 0.30%, 0.45%, and 0.60%) NaCl were studied. The results showed that with increasing concentration of NaCl, the plant growth, leaf chlorophyll content, photochemical efficiency of PSⅡ (F_v/F_m), quantum yield of PSⅡ(Φ_PSⅡ), and photochemical quenching (q_P) decreased gradually, while the non-photochemical quenching of fluorescence (q_N) was in adverse. After 10 days of 0.15% NaCl stress, the leaf chlorophyll content, F_v/F_m, Φ_PSⅡ, and q_P of H. dulcis seedlings decreased by 19.77%, 2.94%, 29.03%, and 8.16%, respectively, with significant differences (P<0.05) to the control, while no significant differences were observed for G. sinensis seedlings. Compared with the control, the F_v/F_m and Φ_PSⅡ of G. sinensis seedlings in treatment 0.30% NaCl decreased significantly by 1.91% and 14.66%, and the chlorophyll content and q_P of the seedling in treatment 0.45% NaCl decreased significantly by 29.28% and 11.36%, respectively (P<0.05). With increasing concentration of NaCl, the SOD activity of G. sinensis seedlings showed a consistent increasing trend, and that of H. dulcis seedlings increased first and decreased then. The POD and CAT activities of G. sinensis and H. dulci seedlings tended to increase first and decrease then, with the increment being higher for G. sinensis than for H. dulci, while the MDA content of the seedlings had an increasing trend, with the increment being higher for H. dulcis than for G. sinensis, suggesting that the cell membrane lipid peroxidation of H. dulcis was more serious than that of G. sinensis. It was concluded that G. sinensis had greater salt tolerance than H. dulcis, which was related to its higher anti-oxidation enzyme activities.

Impact of glyphosate and acetochlor on Dugesia japonica ingestion and regeneration.

LIU Chang-li^1,2;XI Yi-long²;HUANG Lin¹;WANG Jin¹

2008, 19(11):  2509-2514 . 

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In this paper, the acute toxicity of glyphosate and acetochlor on Dugesia japonica and the impact of these two chemicals on the ingestion and regeneration of D. japonica were studied. The results showed that the 24 h and 48 h LC₅₀ of glyphosate and acetochlor on D. japonica was 41.78 and 12.22 mg·L^-1, and 35.48 and 8.41 mg·L^-1, respectively. Glyphosate at the concentration of >6.20 mg·L^-1 and acetochlor at the concentration >1.0 mg·L^-1 impact the regeneration of D. japonica（P<0.05）significantly, but the impact decreased gradually with exposure time. If taking 84 hours after operation as a standard, D. japonica could regenerate well in glyphosate and acetochlor solutions at most of test concentrations except at 1.40 mg·L^-1 and 2.00 mg·L^-1 of acetochlor. It was indicated that comparing with glyphosate, acetochlor had stronger acute toxicity and stronger impact on D. japonica and its ingestion and regeneration, and D. japonica could be used as a bio-indicator to monitor glyphosate and acetochlor contamination.

Subcellular distribution and chemical forms of Cd and Zn in Sedum jinianum.

ZHOU Shou-biao¹;XU Li-sheng^1,2;WU Long-hua²;LUO Yong-ming²;LI Na²;CUI Li-qiang²

2008, 19(11):  2515-2520 . 

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With water culture and by using differential centrifugation technique and sequential extraction, the subcellular distribution and chemical forms of Cd and Zn in the root, stem and leaf of Sedum jinianum were studied. In treatment 10 μmol Cd·L^-1, most of Cd in S. jinianum was in the soluble fraction of cell; while in treatment 100 μmol Cd·L^-1, the Cd in root was mainly deposited on cell wall, the Cd in stem was mainly on cell wall and in soluble fraction, and over 90% of Cd in leaf were in soluble fraction. In treatment 100 μmol Cd·L^-1, the proportion of Cd on the cell walls of root, stem and leaf increased, while that in soluble fraction decreased. In treatments 1 and 800 μmol Zn·L^-1, the Zn in root, stem and leaf mainly presented in soluble fraction; while in treatments with the Zn level between 1.0 and 800 μmol·L^-1, there were no differences in the proportions of Zn in the soluble fraction and on the cell walls of root, stem and leaf. Very low proportions of Cd and Zn were found in cell organelle. The Cd in the root, stem and leaf was predominated with NaCl- and water-extractable forms, while Zn in the plants were existed in numerous chemical forms.

Roles of exogenous spermidine in improving Salvinia natans tolerance towards cadmium stress.

XU Qin-song;SHI Guo-xin;WANG Hong-xia;YANG Hai-yan;ZHAO Juan;XU Ye

2008, 19(11):  2521-2526 . 

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In this study, the effects of foliar spraying different concentration (0.05-1 mmol·L^-1) spermidine (Spd) on the photosynthetic pigments, soluble protein content, antioxidant system, and mineral nutrition of Salvinia natans leaves under cadmium (Cd) stress were investigated, aimed to approach the action mechanisms of exogenous polyamines (PAs) in improving the adaptability of aquatic plants to heavy metals stress. The results showed that exogenous Spd could markedly mitigate the Cd stress to S. natans. It retarded the chlorosis, with chlorophyll a/b and total chlorophyll content increased by 18.97% and 43.96%, respectively, and increased the soluble protein content by 27.83%, compared with the control. SDS-PAGE revealed that the increase of soluble protein content was mainly of the expression increase of 5 polypeptides with apparent molecular weights 202.15, 77.67, 52.69, 41.83, and 25.35 kD. Exogenous Spd increased the activities of antioxidant enzymes SOD, POD and CAT and the contents of low molecular weight protective compounds AsA, GSH and Car, with an average increase of 12.44%, 66.90% and 51.23%, and 11.21%, 17.60% and 24.81%, respectively, and effectively maintained the balanced absorption of P, K, Fe, Na, Mg, Zn and Mn (with exception of Ca). In general, the optimum concentration range of exogenous Spd was 0.05-0.1 mmol·L^-1, which could enhance the resistance of S. natans to Cd toxicity by improving photosynthesis, stimulating the expression of protein, promoting the activity / content of antioxidant system, and keeping the balanced absorption of nutrient elements, etc.

Effects of sub-lethal dosages abamectin on food intake and digestive enzyme activities of silkworm Bombyx mori L.

ZHU Jiu-sheng^1,2;WANG Jing¹;GAO Hai-yan^1,2;QIN Shu¹;QIAO Xiong-wu¹;HAN Ju-cai²

2008, 19(11):  2527-2532 . 

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Mulberry leaves treated with sub-lethal dosages (LC₅, LC₁₀ and LC₂₀) abamectin were fed to the 5th instar larvae of silkworm (Bombyx mori L.), and the food intake and digestive enzyme activities of the larvae were studied by using gravimetric method and measuring enzyme activities. The results showed that sub-lethal dosages abamectin significantly inhibited the growth and food intake of the larvae, with their body mass and its increase rate as well as their relative growth rate being significantly lower than the control, and accompanied with the decreases of food intake, its relative consumption rate, and feces amount. The efficiency of the conversion of ingested food (ECI) and that of the conversion of digested food (EDI) also reduced, but the approximate digestibility (AD) increased significantly. The amylase and sucrase activities in the midgut of the larvae treated with abamectin decreased significantly for a longer time at the beginning, and then recovered to the same as or a higher level than the control, whereas the trehalase activity decreased significantly for a shorter time at the beginning, then increased significantly, and finally recovered to the normal. It was suggested that sub-lethal dosages abamectin had definite toxicity to the silkworm, and the toxic effect was increased with increasing dosage, which could result in the turbulence of silkworm’s digestive system, and further, affect its food intake and its growth and development.

Synergism of plant volatiles to insect pheromones and related mechanisms.

WANG zhen-hua;ZHAO hui;Li jin-fu;ZENG xian-dong;CHEN jian-jun;FENG han-li;XU jia-wen

2008, 19(11):  2533-2537 . 

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Host plant volatiles and insect pheromones are the most important semiochemicals for insects, and their synergism can modulate insect behaviors. The attraction to sex- and aggregation pheromones of insects can be greatly enhanced by specific plant volatiles through the increased electroantennogram, pheromone incepting neuron action potential, and pulse-frequency. When the specific plant volatiles are bound with octopamine receptors, the threshold of sex pheromone incepting neuron to sex pheromones is decreased, while the sensibility of sex pheromone incepting neuron is increased, which may be the main mechanism for the synergism of plant volatiles to insect pheromones.

Landscape planning approaches for biodiversity conservation in agriculture.

LIU Yun-hui;LI Liang-tao;YU Zhen-rong

2008, 19(11):  2538-2543 . 

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Biodiversity conservation in agriculture not only relates to the sustainable development of agriculture, but also is an essential part of species conservation. In recent years, the landscape planning approach for biodiversity was highlighted instead of species-focused approach. In this paper, the landscape factors affecting the biodiversity in agriculture were reviewed, and the possible landscape approaches at three different scales for more efficient conservation of biodiversity in agro-landscape were suggested, including: 1) the increase of the proportion of natural or semi-natural habitats in agriculture, diversification of land use or crop pattern, and protection or construction of corridor at landscape level; 2) the establishment of non-cropping elements such as field margin at between-field level; and 3) the application of reasonable crop density,crop distribution pattern and rotation, and intercrop etc. at within-field level. It was suggested that the relevant policies for natural conservation, land use planning, and ecological compensation should be made to apply the landscape approaches for biodiversity conservation at larger scale.

Comparison of sustainable development status in Heilongjiang Province based on traditional ecological footprint method and emergy ecological footprint method.

CHEN Chun-feng¹; WANG Hong-yan¹; XIAO Du-ning²; WANG Da-qing¹

2008, 19(11):  2544-2549 . 

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By using traditional ecological footprint method and its modification, emergy ecological footprint method, the sustainable development status of Heilongjiang Province in 2005 was analyzed. The results showed that the ecological deficits of Heilongjiang Province in 2005 based on emergy and conventional ecological footprint methods were 1.919 and 0.6256 hm²·cap^-1, respectively.The ecological footprint value based on the two methods both exceeded its carrying capacity, which indicated that the social and economic development of the study area was not sustainable. Emergy ecological footprint method was used to discuss the relationships between human’s material demand and ecosystem resources supply, and more stable parameters such as emergy transformity and emergy density were introduced into emergy ecological footprint method, which overcame some of the shortcomings of conventional ecological method.

Habitat factor analysis for Torreya grandis cv. Merrillii based on spatial information technology.

WANG Xiao-ming^1,2,3;WANG Ke^1,2;AO Wei-jiu^1,2;DENG Jin-song^1,2;HAN Ning^1,2;ZHU Xiao-yun^1,2

2008, 19(11):  2550-2554 . 

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Torreya grandis cv. Merrillii, a tertiary survival plant, is a rare tree species of significant economic value and expands rapidly in China. Its special habitat factor analysis has the potential value to provide guide information for its planting, management, and sustainable development, because the suitable growth conditions for this tree species are special and strict. In this paper, the special habitat factors for T. grandis cv. Merrillii in its core region, i.e., in seven villages of Zhuji City, Zhejiang Province were analyzed with Principal Component Analysis (PCA) and a series of data, such as IKONOS image, Digital Elevation Model (DEM), and field survey data supported by the spatial information technology. The results showed that T. grandis cv. Merrillii exhibited high selectivity of environmental factors such as elevation, slope, and aspect. 96.22% of T. grandis cv. Merrillii trees were located at the elevation from 300 to 600 m, 97.52% of them were found to present on the areas whose slope was less than 30°, and 74.43% of them distributed on sunny and half-sunny slopes. The results of PCA analysis indicated that the main environmental factors affecting the habitat of T. grandis cv. Merrillii were moisture, heat, and soil nutrients, and moisture might be one of the most important ecological factors for T. grandis cv. Merrillii due to the unique biological and ecological characteristics of the tree species.