Table of Content

18 July 2014, Volume 25 Issue 7

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Treering growth responses of Mongolian oak (Quercus mongolica) to climate change in southern Northeast: A case study in Qianshan Mountains.

LI Teng1,2, HE Xing-yuan1, CHEN Zhen-ju1,3,4

2014, 25(7):  1841-1848. 

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Mongolian oak is one of the most important broad-leaved tree species in forests, Northeast China. Based on the methodology of dendrochronology, the variations of tree ring radial growth of Mongolian oak in Qianshan Mountains, south of Northeast China, were analyzed. Combined with the temperature and precipitation data from meteorological stations since 1951, the relationships between standardized tree ring width chronology and main climatic factors were analyzed. In this region, the precipitation between April and July of the current year had an  significant relationship with the tree ring width of Mongolian oak, and was the main factor limiting the radial growth. The extreme maximum temperature of May was also a key factor influencing the tree ring width, which had a significant  on the tree ring width of Mongolian oak. The precipitation in April had a significant and stable relationship with  the growth of Mongolian oak since the 1950s. The ‘divergence problem’ was found in the study area, which the sensitivity of tree growth to summer temperature reduced since the 1980s. The tree growth response to temperature showed a seasonal change from summer to spring.

High altitude Pinus taiwanensis Hayata growth response to climate in Jiulongshan and Guniujiang, Southeastern China.

LI Ling-ling1, SHI Jiang-feng1,2,3, HOU Xin-yuan1, YE Jin-shui4, MAO Hai-bo4, ZHAO Xin-wei1, LU Hua-yu1

2014, 25(7):  1849-1856. 

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Two robust Pinus taiwanensis Hayata treering width chronologies were developed at high elevation sites in Jiulongshan Natural Conservation Area (JLS01), southeastern Zhejiang Province and Guniujiang (GNJ01), southern Anhui Province, China. The reliable period was 1884-2010 for JLS01 and 1837-2008 for GNJ01, based on subsample signal strength (SSS) threshold value of 0.8. Meteorological data were monthly mean temperature, monthly total precipitation and monthly mean relative humidity, monthly total cloud cover, as well as monthly sunshine duration. The data from the meteorological stations around the sampling sites were averaged to represent regional climate, which were used in the correlation analyses with the treering chronologies. The correlation analyses indicated that summer (prior June-July and current June) hydrothermal condition was the main limiting factor on radial tree growth at the two high elevation sites. For JLS01 chronology, significant positive correlations were found with prior June-July temperature and sunshine duration, significant negative correlations with prior June-July and current June precipitation and relative humidity, and total cloud cover of prior July. GNJ01 chronology was significantly positively correlated with prior July temperature as well as prior July and current June sunshine duration, negatively correlated with prior July and current June precipitation and relative humidity, as well as total cloud cover of prior June. These results showed that relatively high temperature could promote radial growth, whereas high precipitation, together with high relative humidity, high cloud cover and low sunshine duration, could limit the photosynthesis and thus restrain the radial tree growth.

Dendroclimatic potentials for the tree rings of Huangshan pine (Pinus taiwanensis) at Xiaolinhai in the western Dabie Mountains, China.

PENG Jian-feng, LI Guo-dong, LI Ling-ling

2014, 25(7):  1857-1862. 

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By using the dendrochronology research methods, this paper developed the 1915-2011 tree ringwidth standard chronology of the Huangshan pine (Pinus taiwanesis) at the north slope of western Dabie Mountains in the junction of Hubei, Henan and Anhui provinces. High mean sensitivity (MS) indicated that there was conspicuous highfrequency climate signals and high firstorder autocorrelation (AC) showed there were significant lageffects of tree previous growth. The higher signaltonoise ratio (SNR) and expressed population signal (EPS) indicated that the trees had high levels of common climate signals. Correlations between the tree ringwidth standard chronology and climatic factors (1959-2011) revealed the significant influences of temperature, precipitation and relative humidity on the tree width growth of Huangshan pine by the end of growing season (September and October). Significant positive correlations were found between the treering indices and the Palmer drought severity index (PDSI) of current September and October. In conclusion, the combination of water and heat of September and October is the major effect factor for the growth of Huangshan pine in western Dabie Mountains.

Sexual differences in climatic response of dioecious Populus davidiana tree.

GAO Lu-shuang, ZHAO Xiu-hai, WANG Xiao-ming, ZHANG Chun-yu

2014, 25(7):  1863-1869. 

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The treering width series and standardized chronologies of Populus davidiana trees in broad-leaved and Korean pine forest in Changbai Mountains were developed separately for male and female trees. Their differential radial growth and their relationship with climatic conditions were analyzed to reveal the effect of gender on radial growth and their climatic responses. It was found that there was a significant differential growth pattern before and after climate change for dioecious trees. The differential responses of the females and males to climate were also observed. The radial increment of female trees before 1980 was significantly higher than that of male trees, and the growth of female was negatively related with the monthly minimum temperature at the end of current growing season and precipitation in the previous and current growing season. The male was significantly positively related with the current growing season temperature. After 1980, the monthly temperature significantly increased, especially the monthly minimum temperature. The increment of dioecious trees decreased. The annual radial growth rate of the female was significantly lower than that of the male. Compared with  the male tree, the female was more sensitive to the monthly minimum temperature. The female was significantly positively related with the spring minimum temperature and significantly negatively with the minimum temperature at the end of previous growing season. There was no significant correlation between the male and monthly minimum temperature. The monthly minimum temperature had an important impact on female P. davidiana trees in Changbai Mountains. Under the condition of stable precipitation, the increase of minimum temperature would restrain the growth of females, but lightly influenced the males’ growth.

Effect of climate change on net primary productivity of Korean pine (Pinus koraiensis) at different successional  stages of broad-leaved Korean pine forest.

QIU Yang, GAO Lu-shuang, ZHANG Xue, GUO Jing, MA Zhi-yuan

2014, 25(7):  1870-1878. 

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Pinus koraiensis in broadleaved Korean pine forests of Changbai Mountain at different successional stages (secondary poplarbirch forest, secondary coniferous and broadleaved forest and the primitive Korean pine forest) were selected in this paper as the research objects. In this research, the annual growth of net primary productivity (NPP) (1921-2006) of P. koraiensis was obtained by combining the treering chronology and relative growth formulae, the correlation between NPP of P. koraiensis and climatic factors was developed, and the annual growth of NPP of P. koraiensis at different successional stages in relation to climatic variation within different climate periods were analyzed. The results showed that, in the research period, the correlations between climatic factors and NPP of P. koraiensis at different successional stages were different. With increasing the temperature, the correlations between NPP of P. koraiensis in the secondary poplarbirch forest and the minimum temperatures of previous and current growing seasons changed from being significantly negative  to being significantly positive. The positive correlation between NPP of P. koraiensis in the secondary coniferous and broadleaved forest and the minimum temperature in current spring changed into significantly positive correlation  between NPP of P. koraiensis and the temperatures in previous and current growing seasons. The climatic factors had a stronger hysteresis effect on NPP of P. koraiensis in the secondary coniferous and broad-leaved forest, but NPP of P. koraiensis in the primitive Korean pine forest had weaker correlation with temperature but stronger positive correlation  with the precipitation of previous growing season. The increases of minimum and mean temperatures were obvious, but no significant variations of the maximum temperature and precipitation were observed at our site. The climatic variation facilitated the increase of the NPP of P. koraiensis in the secondary poplarbirch forest at the initial successional stage and in secondary coniferous and broad-leaved forest  at the  intermediate successional stage, and this effect was especially obvious for the secondary coniferous and broad-leaved forest, but very small for the primitive Korean pine forest which was at the climax phase.

Research advances in dendrochronology.

FANG Ke-yan1, CHEN Qiu-yan2, LIU Chang-zhi2, CAO Chun-fu1, CHEN Ya-jun1, ZHOU Fei-fei1

2014, 25(7):  1879-1888. 

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Tree-ring studies in China have achieved great advances since the 1990s, particularly for the dendroclimatological studies which have made some influence around the world. However, because of the uneven development, limited attention has been currently paid on the other branches of dendrochronology. We herein briefly compared the advances of dendrochronology in China and of the world and presented suggestions on future dendrochronological studies. Largescale tree-ring based climate reconstructions in China are highly needed by employing mathematical methods and a high quality tree-ring network of the ring-width, density, stable isotope and wood anatomy. Tree-ring based field climate reconstructions provide potentials on explorations of climate forcings during the reconstructed periods via climate diagnosis and process simulation.

Nutrient accumulation and cycling in pure and mixed plantations of Azadirachta indica and Acacia auriculiformis in a dryhot valley, Yunnan Province, southwest China.

GAO Cheng-jie1, LI Kun1,2, TANG Guo-yong1,2, ZHANG Chun-hua1,2, LI Bin1

2014, 25(7):  1889-1897. 

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To ease the implementation of effective nutrient management for plantations with different vegetation restoration patterns and to assist in the selection of appropriate species and forestation patterns, nutrient (N, P, K, Ca and Mg) accumulation and cycling were investigated and compared in three plantations (10-year-old Azadirachta indica, Acacia auriculiformis and mixed A. indica-A. auriculiformis plantations) in Yuanmou Valley, a dry-hot valley of Yunnan Province, Southwestern China. The result showed that total nutrient accumulations were 333.05, 725.61 and 533.85 kg·hm^-2 in pure plantations of A. indica and A. auriculiformis, and in A. indica-A. auriculiformis mixed plantation, respectively. The nutrient accumulation of various organs was ranked as branches > stems > roots > leaves > bark in the A. indica plantation and branches > stems > leaves > roots > bark both in the A. auriculiformis plantation and in the mixed plantation. Changes in accumulation of various nutrients in the mixed plantation were similar to that in the A. auriculiformis plantation (Ca > N > K > Mg > P), which were different from the A. indica plantation (Ca > K > N > Mg > P). Annual net nutrient accumulation, return and absorption in these plantations ranged from 62.72 to 162.19 kg·hm^-2·a^-1, 48.82 to 88.86 kg·hm^-2·a^-1 and 111.54 to 251.05 kg·hm^-2·a^-1, respectively, which were all the highest in the A. auriculiformis plantation, followed by the mixed plantation, and were the lowest in the A. indica plantation. The nutrient utilization coefficient, the cycling coefficient and the recycling period were estimated to be from 0.34 to 0.39, 0.35 to 0.44, and 6.54 to 8.17 a, respectively. The lower nutrient return and circulation rate of N or P in the A. indica plantation showed that this plantation had a poor ability to maintain soil fertility, while the highest nutrient circulation rate of N or P was observed in the A. auriculiformis plantation that displayed the advantage  in maintaining soil nutrients and stand productivity. The nutrient return and nutrient absorption in the mixed plantation were 167.2% and 186.2%, of those in the A. indica plantation, and the circulation rate of N, P and K were higher than those in the A. indica plantation, while the recycling period of Ca in mixed plantation was 50% shorter than that in A. auriculiformis plantation. Soil fertility and  nutrient supply were improved in the A. indica and A. auriculiformis mixed plantation.

Long-term effects of thinning on carbon storage in Cunninghamia lanceolata plantations.

XU Jin-liang1, MAO Yu-ming1, CHENG Xiang-rong2, YU Mu-kui2

2014, 25(7):  1898-1904. 

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The stand environment and tree growth could be changed as well as carbon storage be affected by thinning. Thus it is important to conduct the research on changes of carbon stock in plantations after thinning for assessing the dynamics of forest ecosystem carbon pool. The carbon storage and its distribution of various components in 22-year-old Cunninghamia lanceolata plantations were studied with control and different treatments such as moderate and heavy thinning. Moderate (thinning intensity was 35%) and heavy (thinning intensity was 50%) thinning treatments were conducted twice at the age of 7 and 14 years, respectively. The stand of control was thinned 15% in the 14th year. The results showed that the proportion of stem carbon storage increased with the increasing thinning intensity, while the proportion of carbon storage in branches, leaves and roots slightly decreased, which suggested that thinning was beneficial for carbon stocking in stem. However, the carbon storage in arbor layer decreased with the thinning intensity in C. lanceolata plantation under moderate and heavy thinning treatments, accounted for 89.0% and 83.1% of the control, respectively. The arbor carbon storage decreased in followed two years after the first thinning. The carbon storage in arbor layer had a fast recovery rate within eight years after the second thinning, and the increment of carbon storage in arbor layer had no difference with the control for the heavy thinning treatment. The carbon storage in understory vegetation, litter and soil layers also had no significant difference under the different thinning treatments. Generally total ecosystem carbon storage under the control, moderate and heavy thinning treatments reached 169.34, 156.65 and 154.37 t·hm^-2, respectively. There was no significant difference among the three treatments. Therefore, it could be concluded that the carbon storage in C. lanceolata plantation did not reduce after thinning in more than 15 years.

Distribution of fine root biomass of main planting tree species in Loess Plateau, China.

JIAN Sheng-qi, ZHAO Chuan-yan, FANG Shu-min, YU Kai

2014, 25(7):  1905-1911. 

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The distribution of fine roots of Pinus tabuliformis, Populus tomentosa, Prunus armeniaca, Robinia pseudoacacia, Hippophae rhamnoides, and Caragana korshinskii was investigated by using soil core method and the fine root was defined as root with diameter less than 2 mm. The soil moisture and soil properties were measured. The results showed that in the horizontal direction, the distribution of fine root biomass of P. tabuliformis presented a conic curve, and the fine root biomass of the other species expressed logarithm correlation. Radial roots developed, the fine root biomass were concentrated within the scope of the 2-3 times crown, indicating that trees extended their roots laterally to seek water farther from the tree. In the vertical direction, the fine root biomass decreased with the increasing soil depth. Fine root biomass had significant negative correlation with soil water content and bulk density, while significant positive correlation with organic matter and total N contents.

Stand density estimation based on the measurement of spatial structure.

WANG Hong-xiang, HUI Gang-ying, ZHANG Gong-qiao, LI Yuan-fa, LIU En

2014, 25(7):  1912-1918. 

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This study estimated stem density by combining distance sampling with stand spatial structure investigation techniques. We tested the statistical performance of two investigative methods (selecting the fourth or sixthnearest tree to the sample location) and three different density estimators (Prodan, Persson and Thompson). Different spatial distribution patterns influenced the performance of these estimators. Prodan’s estimator was unbiased for uniform patterns, and it produced increasing bias with increasing spatial clustering. Persson’s estimator produced consistent positive bias for uniform and random patterns, with the smallest bias for clustered patterns. Thompson’s estimator was robust for random or near-random patterns, and it produced positive and negative bias for uniform and clustered patterns, respectively. No significant performance difference was found between selecting the fourth and the sixthnearest trees with the same sample size of 49. Thus, we could combine distance sampling with spatial structure investigation techniques.

Impacts of land-use types on soil C mineralization and temperature sensitivity of forests in Qianyanzhou, Jiangxi Province, China.

LI Jie1,2, WEI Xue-hong1, CHAI Hua1, WANG Ruo-meng2, WANG Dan2, HE Nian-peng2

2014, 25(7):  1919-1926. 

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Decomposition of soil organic matter plays an important role in the regulation of carbon (C) cycles at ecosystem or regional scales, and is closely related to temperature, moisture, and landuse types. The influences of soil temperature, moisture, and landuse types on soil C mineralization in Citrus reticulata and Pinus elliottii forests were investigated at the Qianyanzhou Ecological Experiment Station, Chinese Academy of Sciences, by conducting incubation experiments at 5-level temperatures (5, 10, 15, 20 and 25 ℃) and 3-level moistures (30%, 60% and 90% saturated soil moisture, SSM). The results showed that soil temperature, moisture, and land-use types had significant effects on soil C mineralization and they had significant interaction effects. Soil C mineralization was positively correlated with incubation temperature in the two forests, and the maximum of soil C mineralization was in the 60% SSM treatment. The accumulation of soil C mineralization was higher in the C. reticulata forest than in the P. elliottii forest under the same temperature and moisture conditions. The temperature sensitivity (Q₁₀) of soil C mineralization was influenced by landuse type and soil moisture. Q₁₀ increased with the increasing soil moisture in both C. reticulata and P. elliottii forests at incubation 7 and 42 d. Q₁₀ in the C. reticulata forest was higher than in the P. elliottii forest in the same moisture level, and the deviation increased with the increasing soil moisture. The model including temperature and moisture could depict the response of soil C mineralization to temperature and moisture. Temperature and moisture together explained 79.9%-91.9% of the variation in soil C mineralization.

Effects of light condition on structure and photosynthetic characteristics of leaves in ‘Hanfu’ apple.

MA Hui-li1, LU De-guo2

2014, 25(7):  1927-1932. 

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By using microscope technique and gas exchange method, the effects of light conditions on structure and photosynthetic characteristics of the leaves were studied with potted and fielded ‘Hanfu’ apple as materials. The results showed that the palisade tissue, spongy tissue and the total leaf thickness of ‘Hanfu’ apple was declined under the weak light environment, the palisade tissue were declined by 34.5% (pot) and 25.0% (field), and the total leaf thickness were declined by 27.1% (pot) and 18.3% (field). The light compensation point (LCP) of the field shading leaves was lowest (30.8±1.3 μmol·m^-2·s^-1), the saturation point (LSP) in full light was 22.7% (pot) and 48.2% (field) higher than in shading, respectively. The adaptability of the potted ‘Hanfu’ apple leaves built under different light conditions had different resistivity after exposing to high light, the startup time of maximum photosynthetic rates (15.4 μmol·m^-2·s^-1 in full light and 12.7 μmol·m^-2·s^-1 in shading) were different, which was 23 min and 33 min, respectively. Longtime shading impacted on the quality and photosynthetic capacity of ‘Hanfu’ apple leaves.

Effects of photoperiod on photosynthesis and PSⅡ performance in peach during dormancy induction.

LI Dong-mei, TAN Qiu-ping, GAO Dong-sheng, CHEN Xiu-de, LI Ling

2014, 25(7):  1933-1939. 

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Long-day and shortday photoperiods were set artificially, with natural condition as the control, to examine photosynthetic parameters and chlorophyll fluorescence transient kinetics of 6-year-old ‘Chunjie’ peach cultivar (Prunus persica cv. Chunjie), and to investigate the effects of photoperiod on photosynthesis of the northern deciduous fruit trees. The tree advanced into the dormancy induction period under the shortday condition, and delayed under the longday condition. In the dormancy induction period, the leaf net photosynthetic rate (P_n) and stomatal conductance (g_s) decreased, and the intercellular CO₂ concentration (C_i) increased, suggesting that the P_n decreased because of nonstomatal limitation. Maximum quantum yield for primary photochemistry (φ_Po, or F_v/F_m), potential activity (F_v/F_o), probability that a trapped exciton moved an electron into the electron transport chain beyond Q_A^-(ψ_o) and performance index on absorption basis (PI_ABS) decreased in the dormancy induction period, suggesting that the electron transport capacity of photosynthetic electron transport chain was inhibited, possibly due to the damage to downstream electron transport chain (after Q_A^- acceptor) of PSⅡ reaction center. Longday photoperiod improved P_n in the dormancy induction period, and reduced the range of decline in PI_ABS and the injured degree of photosystem. Shortday photoperiod deepened and accelerated the damage to photosynthetic apparatus significantly. The induced effect of photoperiod was associated with the dormancy processes.

Effects of shade on photosynthetic characteristics and chlorophyll fluorescence of Ardisia violacea.

ZHANG Yun1,2,3, XIA Guo-hua2,3, MA Kai4, LI Gen-you2, DAI Ying-chao2， YAN Cai-xia1,2

2014, 25(7):  1940-1948. 

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Ardisia violacea is one of the rare and endangered species, and distributes only in Zhejiang and Taiwan Provinces in China. In order to understand the light requirement and adaptability of A. violacea, the effects of different light intensities (shading rate of 90%, 60%, 25%, and the full light) on leaf photosynthetic characteristics and chlorophyll fluorescence of A. violacea were studied. The photosynthetic rate (P_n) and stomatal conductance (g_s) of A. violacea varied as a bimodal curve with a ‘midday depression’ phenomenon in full bright light, and as a unimodal curve in the shading treatments. With the increasing shading rate, the P_n and apparent quantum efficiency (AQY) first increased, and then decreased, the light compensation point (LCP) and light saturation point (LSP) decreased,  and the g_s, transpiration rate (T_r), original light energy conversion (F_v/F_m) and potential activity of PSⅡ (F_v/F_o) increased. The total quantity of chlorophyll and the carotenoid (Car) content increased, and Chl a/b decreased under shading conditions. When the shading rate was 25%, the specific leaf mass (LMA) and root to shoot (R/T) ratio of A. violacea reached the maximum. A. violacea possessed a strong flexibility to different light environments, suggesting that light could not be the main limiting factor for natural regeneration of A. violacea populations.

Effects of different perlite additions on physical and chemical properties of sewage sludge compost and growth of Tagetes patula.

HU Yu-tong1,2, SHI Lian-hui1,2,3, LIU Deng-min1,2, TONG Shao-wei1,2,WEI Mei-yan1,2, SUN Jie1,2

2014, 25(7):  1949-1954. 

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In order to resolve the problem of poor permeability of sewage sludge compost (SSC) which was used as the substitution of peat, perlite was used to regulate the permeability of the sewage. The pure SSC was used as control. The proportions of perlite in the mixtures with SSC were 20%, 40%, 60%, 80% and 100% (V/V), respectively. The effects of different perlite ratios on the physical and chemical properties and the growth of Tagetes patula were studied. The bulk density, water holding porosity and water holding porosity to aeration porosity decreased, but the total porosity and aeration porosity increased with the increasing addition of perlite to the SSC. For the chemical properties, the pH increased, and the EC and nutrient contents decreased with the increasing addition of perlite to the SSC. The aboveground biomass and flowers of T. patula were the highest in the 60% perlite treatment, and the lowest in the pure SSC treatment. The root morphology and activity were the best in the 40%, 60% and 80% perlite treatments. Aeration was the strongest factor to impact the maximum root length and average root diameter. Perlite promoted the growth of T. patula mainly through impacting the physical properties of the SSC. The addition of 60% perlite to the SSC could significantly improve the poor aeration and decrease the high salinity greatly in the SSC and regulate the growth of the root and  aboveground of  T. patula.

Effects of different LED light qualities on growth, photosynthetic characteristics and nutritional quality of savoy.

CHEN Xiang-wei, LIU Shi-qi, WANG Yue, LIU Jing-kai, Feng Lei

2014, 25(7):  1955-1962. 

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LED lighting has several unique advantages over traditional lighting, including the ability to control spectral composition, the ability to produce very high light levels with low radiant heat output when cooled properly, and the ability to maintain useful light output for years without replacement. LED light sources have the capability of controlling true spectral composition, allowing wavelengths to match plant photoreceptors to provide more optimal production to regulate plant morphology and nutritional quality. In this paper, the effects of different light qualities on the growth, photosynthetic response and nutritional quality of savoy were studied. With ‘JuhuaXiaobaye’ savoy as the test plant, full red light, full blue light, red/blue (3/1) light, red/blue (7/1) light and white/red/blue (3/2/1) light generated by lightemitting diodes were applied with white light generated by fluorescent lamps as control. The results showed that red light could increase biomass and stem diameter, but blue light showed the opposite effect. The chlorophyll (a+b) content was the highest in the red/blue (7/1) light treatment, and chlorophyll (a+b) content was correlated with the red/blue ratio positively. Blue light decreased chlorophyll (a+b) content of savoy, and increased chlorophyll a/b. The photosynthetic rate (P_n) and transpiration rate  under red light were the highest, and increased by 43.8% and 55.1% compared with the control. Intercellular CO₂ concentration  and conductance  were the highest under blue light. The fluorescence parameters of the plant were significantly affected by light quality. Values of the maximal photochemical efficiency of PSⅡ (F_v/F_m), F_v/F_o and Φ_PSⅡ were the highest under white light. Soluble sugar, soluble protein and vitamin C contents were the highest under red, blue and white light, respectively. Comprehensive analysis indicated that red/blue (7/1) light was the best light combination to increase leaf chlorophyll (a+b) content and net photosynthetic rate, as well as plant growth and nutritional quality.

Characteristics of phosphorus uptake and use efficiency of rice with high yield and high phosphorus use efficiency.

LI Li, ZHANG Xi-zhou, LI Ting-xuan, YU Hai-ying, JI Lin, CHEN Guang-deng

2014, 25(7):  1963-1970. 

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A total of twenty seven middle maturing rice varieties as parent materials were divided into four types based on P use efficiency for grain yield in 2011 by field experiment with normal phosphorus (P) application. The rice variety with high yield and high P efficiency was identified by pot experiment with normal and low P applications, and the contribution rates of various P efficiencies to yield were investigated in 2012. There were significant genotype differences in yield and P efficiency of the test materials. GRLu17/AiTTP//Lu17_2 (QR20) was identified as a variety with high yield and high P efficiency, and its yields at the low and normal rates of P application were 1.96 and 1.92 times of that of Yuxiang B, respectively. The contribution rate of P accumulation to yield was greater than that of P grain production efficiency and P harvest index across field and pot experiments. The contribution rates of P accumulation and P grain production efficiency to yield were not significantly different under the normal P condition, whereas obvious differences were observed under the low P condition (66.5% and 26.6%). The minimal contribution to yield was P harvest index (11.8%). Under the normal P condition, the contribution rates of P accumulation to yield and P harvest index were the highest at the jointingheading stage, which were 93.4% and 85.7%, respectively. In addition, the contribution rate of P accumulation to grain production efficiency was 41.8%. Under the low P condition, the maximal contribution rates of P accumulation to yield and grain production efficiency were observed at the tilleringjointing stage, which were 56.9% and 20.1% respectively. Furthermore, the contribution rate of P accumulation to P harvest index was 16.0%. The yield, P accumulation, and P harvest index of QR20 significantly increased under the normal P condition by 20.6%, 18.1% and 18.2% respectively compared with that in the low P condition. The rank of the contribution rates of P efficiencies to the yield was in order of P uptake efficiency > P utilization efficiency > P transportation efficiency. The greatest contribution rate of P accumulation to the yield was noticed at the jointingheading stage with the normal P application while it reached the maximal value at the tilleringjointing stage with the low P application. Therefore, these two stages may be the critical periods to coordinate high yield and high P efficiency in rice.

Characteristics of dry matter production and nitrogen accumulation in barley genotypes with high nitrogen utilization efficiency.

HUANG Yi1, LI Ting-xuan1, ZHANG Xi-zhou1, JI Lin2

2014, 25(7):  1971-1978. 

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A pot experiment was conducted under low (125 mg·kg^-1) and normal (250 mg·kg^-1) nitrogen treatments. The nitrogen uptake and utilization efficiency of 22 barley cultivars were investigated, and the characteristics of dry matter production and nitrogen accumulation in barley were analyzed. The results showed that nitrogen uptake and utilization efficiency were different for barley under two nitrogen levels. The maximal values of grain yield, nitrogen utilization efficiency for grain and nitrogen harvest index were 2.87, 2.91 and 2.47 times as those of the lowest under the low nitrogen treatment. Grain yield and nitrogen utilization efficiency for grain and nitrogen harvest index of barley genotype with high nitrogen utilization efficiency were significantly greater than low nitrogen utilization efficiency, and the parameters of high nitrogen utilization efficiency genotype were 82.1%, 61.5% and 50.5% higher than low nitrogen utilization efficiency genotype under the low nitrogen treatment. Dry matter mass and nitrogen utilization of high nitrogen utilization efficiency was significantly higher than those of low nitrogen utilization efficiency. A peak of dry matter mass of high nitrogen utilization efficiency occurred during jointing to heading stage, while that of nitrogen accumulation appeared before jointing. Under the low nitrogen treatment, dry matter mass of DH61 and DH121+ was 34.4% and 38.3%, and nitrogen accumulation was 54.8% and 58.0% higher than DH80, respectively. Dry matter mass and nitrogen accumulation seriously affected yield before jointing stage, and the contribution rates were 47.9% and 54.7% respectively under the low nitrogen treatment. The effect of dry matter and nitrogen accumulation on nitrogen utilization efficiency for grain was the largest during heading to mature stages, followed by sowing to jointing stages, with the contribution rate being 29.5% and 48.7%, 29.0% and 15.8%, respectively. In conclusion, barley genotype with high nitrogen utilization efficiency had a strong ability of dry matter production and nitrogen accumulation. It could synergistically improve yield and nitrogen utilization efficiency by enhancing the ability of nitrogen uptake and dry matter formation before jointing stage in barley.

Faba bean fusarium wilt (Fusarium oxysporum) control and its mechanism in different wheat varieties and faba bean intercropping system.

DONG Yan1, DONG Kun2, ZHENG Yi1,3, TANG Li1, YANG Zhi-xian1

2014, 25(7):  1979-1987. 

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Field experiment and hydroponic culture were conducted to investigate effects of three wheat varieties (Yunmai 42, Yunmai 47 and Mianyang 29) and faba bean intercropping on the shoot biomass, disease index of fusarium wilt, functional diversity of microbial community and the amount of Fusarium oxysporum in rhizosphere of faba bean. Contents and components of the soluble sugars, free amino acids and organic acids in the root exudates were also examined. Results showed that,  compared with monocropped faba bean, shoot biomass of faba bean significantly increased by 16.6% and 13.4%, disease index of faba bean fusarium wilt significantly decreased by 47.6% and 23.3% as intercropped with Yunmai 42 and Yunmai 47, but no significant differences of both shoot biomass and disease index were found as intercropped with Mianyang 29.  Compared with monocropped faba bean, the average well color development (AWCD value) and total utilization ability of carbon sources of faba bean significantly increased, the amount of Fusarium oxysporum of faba bean rhizosphere significantly decreased, and the microbial community structures of faba bean rhizosphere changed as intercropped with YM42 and YM47, while no significant effects as intercropped with MY29. Total contents of soluble sugar, free amino acids and organic acids in root exudates were in the trend of MY29＞YM47＞YM42. Contents of serine, glutamic, glycine, valine, methionine, phenylalanine, lysine in root exudates of MY29 were significantly higher than that in YM42 and YM47. The arginine was detected only in the root exudates of YM42 and YM47, and leucine was detected only in the root exudates of MY29. Six organic acids of tartaric acid, malic acid, citric acid, succinic acid, fumaric acid, taconitic acid were detected in root exudates of MY29 and YM47, and four organic acids of tartaric acid, malic acid, citric acid, fumaric acid were detected in root exudates of YM42. Malic acid content in root exudates of YM47 and MY29 was significantly higher than that of YM42. In conclusion, intercropping influenced the microbial activity and substrate utilization of soil microorganisms, altered the microbial community diversity in rhizosphere of faba bean, reduced the amount of F. oxysporum and disease index of faba bean fusarium wilt, and promoted faba bean growth. Effects of intercropping on disease control were influenced by the intercropped wheat variety,  suggesting that the differences of root exudates of wheat were important factors that affected soilborne diseases control in intercropping.

Leaf physiological traits at pod-setting stage in peanut cultivars with different drought resistance.

LI Guang-hui, ZHANG Kun, LIU Feng-zhen, LIU Dan-dan, WAN Yong-shan

2014, 25(7):  1988-1996. 

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With twelve peanut cultivars grown under artificial water control, the drought resistance related physiological and biochemical traits and the drought resistance mechanism of peanut leaves were studied. Two water treatments were designed, that were 50% and 70% of the soil relative water content of the 0-80 cm soil layer, respectively, at podsetting stage. The results showed that the twelve peanut cultivars could be grouped into three different resistance levels based on their yield drought resistance coefficient. The A596, Shanhua 11 and Rugaoxiyangsheng were grouped as cultivars with high resistance, while Huayu 20, Nongda 818, Haihua 1, Shanhua 9 and 79266 with moderate resistance, and the ICG6848, Baisha 1016, Hua 17 and Penglaiyiwohou with weak resistance. The mechanism of high drought resistance in peanut cultivars of A596, Shanhua 11 and Rugaoxiyangsheng were due to more powerful antioxidant capacity, higher activity of photosystemⅡ (PSⅡ) and photosynthetic rate (P_n). By contrast, the moderate resistant cultivars Haihua 1 had stronger antioxidant protection capability, and the Shanhua 9 had much higher PSⅡ activity. The P_n, stomatal limitation value (L_s), maximal photochemical efficiency of PSⅡ (F_v/F_m), photochemical quenching coefficient (q_P), content of malondialdehyde (MDA), relative electric conductivity and superoxide dismutase (SOD) activity of leaves were  very significantly correlated with the drought resistance coefficient. Therefore, they were important indicative traits for the drought resistance at podsetting stage of peanuts. These traits could be evaluated under normal irrigation condition except that the SOD activity should be identified under drought stress. Based on this study, we proposed that Shanhua 11 and 79266 could serve as standard cultivars of high drought resistance and weak drought resistance, respectively. Shanhua 11 could also serve as a standard cultivar for identification of leaf drought resistance traits in peanut.

Change of Bt protein in soil after growing Bt corns and returning corn straws to soil and its effects on soil nutrients.

ZENG Ping1,2,3, FENG Yuan-jiao1,2,3, ZHANG Wan-chun1,2,3, ZHANG Yan-fei 1,2,3, DONG Wen-chao1,2,3, WANG Jian-wu1,2,3

2014, 25(7):  1997-2003. 

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The spatiotemporal dynamics of Bt protein in soil and the change of soil nutrients in rhizosphere soil, root surface soil and soils at 0-20, 20-40 and 40-60 cm were measured in greenhouse experiments. Two Bt corns, 5422Bt1 and 5422CBCL, and their near isogenic nonBt variety 5422 were grown for 90 days and the crop residues were retained to soil. Results showed that 1.59 and 2.78 ng·g^-1 Bt protein were detected in the rhizosphere soil with Bt corns 5422Bt1 and 5422CBCL immediately after harvest. However, there were only trace amounts of Bt protein (<0.5 ng·g^-1) were detected in root surface soil after 90 days and in bulk soil in the two Bt corn treatments after 30, 60 and 90 days. When corn residues returned to soil, Bt protein declined rapidly within 3 days and only trace amounts of Bt protein were measured after 7 days. There were no significant differences in organic matter, available nutrient (alkaline hydrolytic N, available P, available K) or total nutrient (total N, total P, total K) in root surface soils and soils at 0-20 cm, 20-40 cm and 40-60 cm among the Bt and nonBt corns after 90 days. Sixty days after returning crop residues of 5422Bt1 to soil, the contents of organic matter and total N increased and the content of available K reduced significantly in the 0-20 cm soil depth. There were no significant differences in any other parameter at the 0-20 cm depth, neither for any parameter in the 20-40 cm and 40-60 cm soil depths compared to those in the nonBt corn 5422 treatment. There were no significant differences in soil nutrient contents in Bt corn 5422CBCL treatment compared to those in nonBt corn 5422 treatment except that available phosphorus content was reduced in root surface soils, and total P content increased at the 0-20 cm soil depth after 90 days. When crop residues of Bt corn 5422 CBCL were returned to soil, only available P content in the 0-20 cm soil layer was evidently higher compared to the soil receiving crop residues of nonBt corn 5422. Results suggested that Bt protein released from root and crop residues of Bt corns would not accumulate in soil, and growing Bt corns and returning crop residues to soil would have no significant effect on soil nutrients in general.

Effects of straw mulching on soil moisture and watermelon yield in dryland.

SUN Hong-xia1, WANG Wei1,2, ZHANG Peng1, WANG Zhi-wei1, JIA Zhi-kuan1,3, YANG Bao-ping1, HAN Qing-fang1,3

2014, 25(7):  2004-2010. 

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To explore the effects of straw mulching on soil moisture and yield of watermelon, corn straw was used as mulching materials, and three straw mulch treatments were performed, i.e., whole mulch (WM), rows mulch (SM) and root domain mulch (RM), and nonmulching as control. The results indicated that WM and RM treatments increased significantly soil water storage in 0-120 cm of soil layer under root domain and rows compared with the control during watermelon growth period, and soil water storage of RM was higher than that of SM after growing tendril. Effects of all straw mulch treatments on soil moisture were most obvious from watermelon postgrowing tendril to preswelling and maturity. With the growth and development of watermelon, the three straw mulch treatments improved soil moisture around root domain, resulting in increased watermelon yields. Compared with the CK, the WM, SM and RM treatments significantly improved the yield and the water use efficiency of watermelon by 24.8%, 11.5% and 15.1%, and 42.7%, 24.3% and 29.4%. The WM with 13500 kg·hm^-2 straw was recommended for watermelon production in arid areas due to its favorable effect on soil storage moisture, yield and water use efficiency.

Influence of exogenous γ-aminobutyric acid (GABA) on GABA metabolism and amino acid contents in roots of melon seedling under hypoxia stress.

WANG Chun-yan, LI Jing-rui, XIA Qing-ping, WU Xiao-lei, GAO Hong-bo

2014, 25(7):  2011-2018. 

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This paper investigated the influence of γ-aminobutyric acid (GABA) on GABA metabolism and amino acid content under hypoxia stress by accurately controlling the level of dissolved oxygen in hydroponics, using the roots of melon ‘Xiyu 1’ seedlings as the test material. The results showed that compared with the control, the growth of roots was inhibited seriously under hypoxia stress. Meanwhile, the hypoxia-treated roots had significantly higher activities of glutamate decarboxylase (GAD), glutamate dehydrogenase (GDH), glutamate synthase (GOGAT), glutamine synthetase (GS), alanine aminotransferase (ALT), aspartate aminotransferase (AST) as well as the contents of GABA, pyruvic acid, alanine (Ala) and aspartic acid (Asp). But the contents of glutamic acid (Glu) and α-keto glutaric acid in roots under hypoxia stress was obviously lower than those of the control. Exogenous treatment with GABA alleviated the inhibition effect of hypoxia stress on root growth, which was accompanied by an increase in the contents of endogenous GABA, Glu, α-keto glutaric acid and Asp. Furthermore, under hypoxia stress, the activities of GAD, GDH, GOGAT, GS, ALT, AST as well as the contents of pyruvic acid and Ala significantly decreased in roots treated with GABA. However, adding GABA and vinyγ-aminobutyric acid (VGB) reduced the alleviation effect of GABA on melon seedlings under hypoxia stress. The results suggested that absorption of GABA by roots could alleviate the injury of hypoxia stress to melon seedlings. This meant that GABA treatment allows the normal physiological metabolism under hypoxia by inhibiting the GAD activity through feedback and maintaining higher Glu content as well as the balance of carbon and nitrogen.

 

Calculating method for crop water requirement based on air temperature. 

TAO Guo-tong1,2, WANG Jing-lei1,3, NAN Ji-qin1,3, GAO Yang1,3, CHEN Zhi-fang1,3, SONG Ni1,3

2014, 25(7):  2019-2025. 

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The importance of accurately estimating crop water requirement for irrigation forecast and agricultural water management has been widely recognized. Although it has been broadly adopted to determine crop evapotranspiration (ET_c) via meteorological data and crop coefficient, most of the data in whether forecast are qualitative rather than quantitative except air temperature. Therefore, in this study, how to estimate ET_c precisely only using air temperature data in forecast was explored, the accuracy of estimation based on different time scales was also investigated, which was believed to be beneficial to local irrigation forecast as well as optimal management of water and soil resources. Three parameters of Hargreaves equation and two parameters of McClound equation were corrected by using meteorological data of Xinxiang from 1970 to 2010, and Hargreaves equation was selected to calculate reference evapotranspiration (ET₀) during the growth period of winter wheat. A model of calculating crop water requirement was developed to predict ET_c at time scales of 1, 3, and 7 d intervals through combining Hargreaves equation and crop coefficient model based on air temperature. Results showed that the correlation coefficients between measured and predicted values of ET_c reached 0.883 (1 d), 0.933 (3 d), and 0.959 (7 d), respectively. The consistency indexes were 0.94, 0.95 and 0.97, respectively, which showed that forecast error decreased with the increasing time scales. Forecasted accuracy with an error less than 1 mm·d^-1 was more than 80%, and that less than 2 mm·d^-1 was greater than 90%. This study provided sound basis for irrigation forecast and agricultural management in irrigated areas since the forecasted accuracy at each time scale was relatively high.

Influence of green roof application on water quantity and quality in urban region.

WANG Shu-min1,2, LI Xing-yang1, ZHANG Jun-hua2, YU Hui1, HAO You-zhi2, YANG Wan-yi1

2014, 25(7):  2026-2032. 

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Green roof is widely used in advanced stormwater management as a major measure now. Taking Huxi catchment in Chongqing University as the study area, the relationships between green roof installation with runoff volume and water quality in urban region were investigated. The results showed that roof greening in the urban region contributed to reducing the runoff volume and pollution load. In addition, the spatial distribution and area of green roof also had effects on the runoff water quality. With the conditions that the roof area was 25% of the total watershed area, rainfall duration was 15 min and rainfall intensity was 14.8 mm·h^-1, the peak runoff and total runoff volume were reduced by 5.3% and 31%, the pollution loads of total suspended solid (TSS), total phosphorus (TP) and total nitrogen (TN) decreased by 40.0%, 31.6% and 29.8%, their peak concentrations decreased by 21.0%, 16.0% and -12.2%, and the EMCs (event mean concentrations) were cut down by 13.1%, 0.9% and -1.7%, respectively, when all impervious roofs were greened in the research area. With the increase of roof greening rate, the reduction rates of TSS and TP concentrations increased, while the reduction rate of TN concentration decreased on the whole. Much more improvement could be obtained with the use of green roofs near the outlet of the watershed.

 

Analysis on the ecosystem structure and function of Lake Taihu based on Ecopath model.

LI Yun-kai1, LIU En-sheng2, WANG Hui2, GONG Yi1

2014, 25(7):  2033-2040. 

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Based on the data of lake survey conducted during 2008-2009 and the published data of the trophic ecology of key species, the exploited freshwater ecosystem of Lake Taihu was described using Ecopath with Ecosim 6.1 with the aim of characterizing its functioning and structure. The model comprised 20 functional groups including primary producers, the main species of fishes, nonfish vertebrates, and detritus. Results showed that the functional groups were organized into four aggregated trophic levels with the highest levels corresponding to the top predators, culters. Two trophic pathways were found in Lake Taihu, the detrital pathway and grazing pathway. The detrital pathway dominated in the ecosystem. As a consequence of the low ecotrophic efficiency of primary producer and detritus (trophic level Ⅰ), the accumulating detrital sediments continually released waste nutrients back into the system, resulting in its internal pollution. Considering Odum and Ulanowicz’s theory of ecosystem development, the ecosystem was placed on a low developmental stage with high net primary production (NPP), net primary production/total respiration (NPP/R) and lower connectance index (CI), system omnivory index (SOI), and Finn’s cycling index (FCI). The results of mixed trophic impacts and keystone species selection showed that the increasingly intensive fishing exerted a negative effect on the ecosystem, and the topdown effects of top predators were becoming much obviously reduced.

Ecological risk assessment and its management of Bailongjiang watershed, southern Gansu based on landscape pattern.

GONG Jie, ZHAO Cai-xia, XIE Yu-chu, GAO Yan-jing

2014, 25(7):  2041-2048. 

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Watershed ecological risk assessment is an important research subject of watershed ecological protection and environmental management. Research on the ecological risk focuses on addressing the influence of human activities and its spatial variation at watershed scale is vital to policymaking to control the impact of human activity and protocols for sustainable economic and societal development. A comprehensive ecological environment index, incorporating a landscape index and an assessment of ecological vulnerability, was put forward to assess the spatiotemporal characteristics of ecological risk of the Bailongjiang watershed, southern Gansu Province, Northwest China. Using ArcGIS and Fragstats software and a land use map of 2010, an ecological risk map was obtained through spatial sampling and disjunctive Kriging interpolation. The results indicated that there were some obvious spatial differences of ecological risk levels in the watershed. The ecological risk level of the north and northwest of the Bailongjiang was higher than that of the western and southern extremities of the watershed. Ecological risk index (ERI) of Wudu and Tanchang was higher than that of Wenxian and Diebu. Some measures for ecological risk management were put forward on the basis of ERI of Bailongjiang watershed. To strengthen the integrated management of human activities and land use in the watershed, to carry out the vegetation restoration and ecological reconstruction, and to reduce the ecological risks and hazards of irrational human disturbance, are vital to the realization ‘multiplewin’ of the economic, social and ecological protection and for the sustainable development in the hilly area in southern Gansu.

Prediction of litter moisture content in Tahe Forestry Bureau of Northeast China based on FWI moisture codes.

2014, 25(7):  2049-2055. 

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Canadian fire weather index system (FWI) is the most widely used fire weather index system in the world. Its fuel moisture prediction is also a very important research method. In this paper, litter moisture contents of typical forest types in Tahe Forestry Bureau of Northeast China were successively observed and the relationships between FWI codes (fine fuel moisture code FFMC, duff moisture code DMC and drought code DC) and fuel moisture were analyzed. Results showed that the mean absolute error and the mean relative error of models established using FWI moisture code FFMC was 14.9% and 70.7%, respectively, being lower than those of meteorological elements regression model, which indicated that FWI codes had some advantage in predicting litter moisture contents and could be used to predict fuel moisture contents. But the advantage was limited, and further calibration was still needed, especially in modification of FWI codes after rainfall.

Ecological risk assessment of land use based on exploratory spatial data analysis (ESDA): A case study of Haitan Island, Fujian Province.

WU Jian1, CHEN Peng1, WEN Chao-xiang2, FU Shi-feng1, CHEN Qing-hui1

2014, 25(7):  2056-2062. 

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As a novel environment management tool, ecological risk assessment has provided a new perspective for the quantitative evaluation of ecological effects of landuse change. In this study, Haitan Island in Fujian Province was taken as a case. Based on the Landsat TM obtained in 1990, SPOT5 RS images obtained in 2010, general layout planning map of Pingtan Comprehensive Experimental Zone in 2030, as well as the field investigation data, we established an ecological risk index to measure ecological endpoints. By using spatial autocorrelation and semivariance analysis of Exploratory Spatial Data Analysis (ESDA), the ecological risk of Haitan Island under different landuse situations was assessed, including the past (1990), present (2010) and future (2030), and the potential risk and its changing trend were analyzed. The results revealed that the ecological risk index showed obvious scale effect, with strong positive correlation within 3000 meters. Highhigh (HH) and lowlow (LL) aggregations were predominant types in spatial distribution of ecological risk index. The ecological risk index showed significant isotropic characteristics, and its spatial distribution was consistent with Anselin Local Moran I (LISA) distribution during the same period. Dramatic spatial distribution change of each ecological risk area was found among 1990, 2010 and 2030, and the fluctuation trend and amplitude of different ecological risk areas were diverse. The low ecological risk area showed a risetofall trend while the medium and high ecological risk areas showed a falltorise trend. In the planning period, due to intensive anthropogenic disturbance, the high ecological risk area spread throughout the whole region. To reduce the ecological risk in landuse and maintain the regional ecological security, the following ecological risk control strategies could be adopted, i.e., optimizing the spatial pattern of land resources, protecting the key ecoregions and controlling the scale of construction land use.

Assessment of ecological environment effects of coastal development in Hebei Province, China.

CUI Li-tuo1, LI Zhi-wei2

2014, 25(7):  2063-2070. 

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Through the analysis of the development activities and the ecological environment in coastal of Hebei Province, China, an index system for evaluating the ecological environment effect, composed of 28 indices, was set up by the pressure, state and response subsystems. Using the comprehensive index evaluation method, the integrated effects of ecological environment index (EI) was calculated and its grading criterion was founded. The results showed that the ecological environment effect of Hebei Province coastal development varied from being relatively small, normal and then relatively large from 1984 to 2010, and its acceptance degree evolved from being acceptable to being unacceptable. Because the resource and environment pressures caused by coastal development were serious and a delay existed in the state relative to the response, the improvement of various measures in the response subsystem did not show a positive effect on the state, and the environmental quality of ocean showed a degrading trend. Due to the differences in coastal development pattern and strength, the ecological environment effect of development activities showed some spatial differences. The ecological environment effect of Qinhuangdao coastal development was the minimum, followed by Cangzhou and Tangshan. Cangzhou and Tangshan had reached unacceptable levels and needed to further strengthen the restoration and protection of ecological environment.

Diversity and community structure of endophytic fungi from Taxus chinensis var. mairei.

ZANG Wei1, SUN Xiang2, SUN Jian-qiu1, YU Wen-xi3, WANG Xue-song4, YIN Jun-xia1, SONG Rui-qing3

2014, 25(7):  2071-2078. 

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A total of 628 endophytic fungi were isolated from 480 tissue segments of needles and branches of Taxus chinensis var. mairei. According to morphological characteristics and ITS sequences, they represented 43 taxa in 28 genera, of which 10 Hyphomycetes, 20 Coelomycetes, 12 Ascomycetes and 1 unknown fungus. Phomopsis mali was confirmed as the dominant species. In accordance with relative frequency, Alternaria alternata, Aureobasidium pullulans, Colletotrichum boninense, C. gloeosporioides, Epicoccum nigrum, Fungal sp., Fusarium lateritium, Glomerella cingulata, Magnaporthales sp., Nigrospora oryzae, Pestalotiopsis maculiformans, P. microspora, Peyronellaea glomerata and Xylaria sp.1 were more common in T. chinensis var. mairei. T. chinensis var. mairei were severely infected by endophytic fungi. Endophytic fungi were found in 81 percent of plant tissues with a high diversity. Distribution ranges of endophytic fungi were influenced by tissue properties. The colonization rate, richness, diversity of endophytic fungi in needles were obviously lower than in branches, and kinds of endophytic fungi between branches were more similar than those in needles, thus endophytic fungi had tissue preference. In addition, tissue age influenced the community structure of endophytic fungi. The elder branch tissues were, the higher colonization rate, richness, diversity of endophytic fungi were. Systematic studying the diversity and community structure of endophytic fungi in T. chinensis var. mairei and clarifying their distribution regularity in plant tissues would offer basic data and scientific basis for their development and utilization. Discussing the presence of fungal pathogens in healthy plant tissues would be of positive significance for source protection of T. chinensis var. mairei.

Phosphate solubilization of Aureobasidium pullulan F4 and its mechanism.

WANG Dan, ZHAN Jing, SUN Qing-ye

2014, 25(7):  2079-2084. 

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The Aureobasidium pullulans F4 was isolated from the rhizosphere of Hippochaete ramosissimum in Tongguanshan mine wasteland in Tongling City, Anhui Province. Liquid culture was conducted with four kinds of phosphorus sources, calcium phosphate, aluminum phosphate, ferric phosphate and rock phosphate to determine the pH, dissolved phosphorus, phosphorus in the bacteria and organic acid in the solution. The results showed that the phosphate solubilization by A. pullulans F4 varied with phosphorus sources, which decreased in order of aluminum phosphate > ferric phosphate, calcium phosphate > rock phosphate. The amounts of dissolved phosphorus in the different treatments were all higher than 200 mg·L^-1. The pH of the medium dropped immediately in 48 h, and the aluminum phosphate and ferric phosphate treatments showed a greater decrease in pH than the calcium phosphate and rock phosphate treatments. The organic acid synthesized by A. pullulans F4 included oxalic acid, citric acid and tartaric acid, and oxalic acid, among which oxalic acid was the dominated component. The phosphate dissolving capacity of A. pullulans F4 showed no significant correlation with organic acid, but significantly correlated with the pH. The available phosphorus was significantly improved with the combined application of A. pullulans F4 and glucose, suggesting A. pullulans F4 was a potent candidate for remediation of copper mine wastelands.

Growth-promoting effect of inoculating Klebsiella variicola DX120E on different sugarcane cultivars.

WEI Chun-yan1,2, XING Yong-xiu1,2, LIN Li3, YANG Li-tao1,3,4, LI Yang-rui1,2,3, HU Chun-jin4

2014, 25(7):  2085-2092. 

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In order to investigate the growth promoting effect of inoculating Klebsiella variicola DX120E, a bacterial strain with high activity of associative nitrogen fixation, on sugarcane, the strain was inoculated through roots into the pathogen free micropropagated seedlings of two sugarcane cultivars B8 and GT21. The bacterial numbers colonized in sugarcane plants, the activities of the key enzymes for nitrogen metabolism, the nitrate concentration and nutrient uptake were analyzed. The results indicated that the DX120E strain could live, propagate and colonize in the roots and aerial parts of sugarcane seedlings. The DX120E inoculation could effectively promote the plant growth and nutrient uptake, significantly improve the nitrate reductase (NR) activities, and increase the glutamine synthetase (GS) activities and nitrate concentration in certain degree in the leaves, compared with the uninoculated seedlings. It was suggested that Klebsiella variicola DX120E possesses a significant growth promoting effect on sugarcane plants which has a great application potential in developing biological nitrogen fixation fertilizer for sugarcane.

Lethal effects of Trichoderma longibrachiatum on Heterodera avenae.

ZHANG Shu-wu1,2,3,4, XU Bing-liang1,2,3,4, XUE Ying-yu1,4, GU Li-jun1,2

2014, 25(7):  2093-2098. 

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The lethal effect of the conidia suspension of Trichoderma longibrachiatum against second stage juveniles of Heterodera avenae was observed under microscopic conditions and studied in vitro to preliminarily determine the potential and mechanism of the conidia suspension of T. longibrachiatum against H. avenae. Microscopic observation results showed that the conidia suspension of T. longibrachiatum adhered to or parasitized on the surface of second stage juveniles, even some parasitized nematodes were deformed at the initial stage. Later, the second stage juveniles were wrapped and the integuments were penetrated by a large number of hyphae germinated from the conidia suspension of T. longibrachiatum. Even the body of dead second stage juveniles was completely lysed. In vitro studies showed that different concentrations (1.5×10⁵-1.5×10⁷ cfu·mL^-1) of T. longibrachiatum (conidia suspension) had strong lethal and parasitic effects on the second stage juveniles of H. avenae, and significant differences existed among the treatments with different concentrations of T. longibrachiatum. In addition, the lethal and parasitic effects increased with increasing the T. longibrachiatum concentration. The mortality and corrected mortality of the second stage juveniles treated with the concentrations of 1.5×10⁷ cfu·mL^-1 were 91.3% and 90.4% after 72 hours, and the second stage juveniles were parasitized by 88.7% after 14 days. Therefore, the conidia suspension of T. longibrachiatum had a great lethal effect on H. avenae, and the strain could be considered as a potential bio-control agent against H. avenae.

Supercooling capacity and cold hardiness of the Pararcyplera microptera meridionalis (Orthoptera: Acrididae) eggs.

LI Na, ZHOU Xiao-rong, PANG Bao-ping

2014, 25(7):  2099-2104. 

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Using the thermocouple method, the  supercooling point （SCP） and cold hardiness of Pararcyplera microptera meridionalis eggs were measured in the laboratory. The soil water content significantly affected the water content of prediapause eggs， but had no significant effect on the SCP, and the water content of prediapause eggs rose with the increasing soil water content. There were highly significant differences  among the SCPs, water contents or fat contents in the eggs at different developmental stages. With the egg’s development, the water content decreased from 51.5% at oviposition to 46.8%  in 120 days after oviposition, the fat content increased from 10.5% (fresh mass)/19.0% (dry mass) to 14.5% (fresh mass)/28.9% (dry mass), and the SCP declined from -23.5 ℃ to -30.0 ℃. There was a significant correlation  between the SCP and the water content or fat content. The SCPs of deepdiapause eggs were lower than those of pre and earlydiapause eggs. The different low temperatures and treatment durations significantly affected the survival rate of diapause eggs. The lethal low temperature (L_temp50) for 12 h exposure was -27.3 ℃ and the lethal time (L_time50) at -25 ℃ was 22.73 days. As the mean SCPs of diapause eggs was much similar to their L_temp50, the SCP could be considered as a good indicator of cold hardiness for P.  m. meridionalis eggs and this species is a freeze intolerant insect.

Effects of salinity on spawning and larval development of Exopalaemon carinicauda.

LIANG Jun-ping1, LI Jian2, LI Ji-tao2, LIU Ping2, ZHAO Fa-zhen2, NIE Guo-xing1, LI Xue-jun1, KONG Xiang-hui1

2014, 25(7):  2105-2113. 

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Female Exopalaemon carinicauda at ovarian maturation stage Ⅱ rearing by artificial propagation in the laboratory were chosen as test material. The shrimps were gradually acclimated to the experimental salinity levels of 2, 5, 10, 15, 20, 25 and 30 to determine the effects of salinity on spawning, embryonic development and larval growth of E. carinicauda. The results showed that the ovaries of female E. carinicauda could mature at all test salinity levels. However, it failed to spawn at salinity 2. Salinity levels from 10 to 20 were the most favorable for female E. carinicauda spawning. Although larval development was most successful in eggs incubated at salinity levels of 5 to 30, embryonic development were significantly affected by salinity, and the egg incubation period was shorter at salinities of 15, 20 and 25 than at the other salinities. There were no significant effects of salinity on the rates of larval metamorphosis and survival, but the dry mass of individuals was significantly affected by salinity. The dry mass of shrimps reared at salinities of 15 and 20 were significantly higher than at the other salinities. The growth of 20day old shrimps was significantly affected by salinity. The specific growth rate increased with the increasing  salinity level from 5 to 20, and then decreased at the salinity above 20. The mRNA level of gill Na⁺-K⁺ATPase was high at high and low salinities, and the lowest at the theoretical salinity 17.5, which might be equal to the hemolymph osmotic pressure of E. carinicauda. It was implied that female parent E. carinicauda could reproduce in a wide range of salinities, while 20-day old shrimps presented higher growth rates at salinities near its theoretical isosmotic point.

Community structure of planktonic rotifers in the Pearl River Delta.

GAO Yuan1，2, LI Xin-hui1, LAI Zi-ni1, YU Jing2, WANG Chao1, ZENG Yan-yi1, LIU Qian-fu1, YANG Wan-ling1

2014, 25(7):  2114-2122. 

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Four ecological investigations were carried out on planktonic rotifers in Pearl River Delta in 2012. The community structure, including spatial and temporal patterns of species composition, dominant species, biomass and biodiversity, was investigated. The correlation between the community structure of rotifers and the environmental factors was discussed. Moreover, the aggregation structures of rotifers were analyzed. A total of 53 rotifer species were found. Dominant species changed markedly with season and space. Polyarthra trigla had higher dominance. In terms of seasonal changes, the density and biomass were higher in dry season than in wet season, while the biodiversity and evenness indices were vice versa. The biomass and biodiversity of rotifers showed highly significant differences among seasons. In terms of spatial distribution, the average density and the average biomass showed an increase from the southwest to the northeast. The highest density and biomass were recorded in Shiqiao. The biodiversity and evenness indices had an opposite spatial distribution, with the highest values being recorded in Qingqi. The rotifer density was significantly different among the investigated sites, while the biomass and biodiversity were not significantly different. Correlation analysis demonstrated a highly significant positive correlation between rotifer density and biomass, as well as between biodiversity and evenness indices, and a highly negative correlation between biodiversity and biomass. The biodiversity and evenness indices both decreased markedly with the increase of biomass. Principal component analysis indicated that the rotifer density was closely correlated with environment factors, such as water temperature, pH, dissolved oxygen, chlorophyll a content, total phosphorus, and total nitrogen, in different seasons. Aggregation analysis based on rotifer density revealed five aggregation structures in the investigated sites, indicating significant differences in water quality among the investigated sites.

Community structure of phytoplankton in Haizhou Bay and adjacent waters and its relationships with environmental factors.

YANG Xiao-gai, XUE Ying, ZAN Xiao-xiao, REN Yi-ping

2014, 25(7):  2123-2131. 

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Based on the data collected from four seasonal surveys in 2011 in Haizhou Bay and adjacent waters, community structure of phytoplankton was studied and their relationships with environmental factors were evaluated by canonical correlation analysis (CCA). A total of 113 phytoplankton species belonging to 3 phyla and 44 genera were collected, among which Bacillariophyta species were the most abundant species, which included 39 genera and 99 species, accounting for 87.6%  of total taxa, followed by Pyrrophyta, which included 4 genera and 13 species, accounting for 11.5 percent of total taxa. And the least abundant species were Chrysophyta species, which had only 1 species belonging to 1 genus.Among these dominant species, Coscinodiscus and Chaetoceros were the dominant groups in Bacillariophyta, while Ceratium was the dominant group in Dinophyta, and the dominant species were Meuniera membranacea, Coscinodiscus subtilis var. subtilis, Eucampia zodiacus and Bacillaria paxillifera. There were obvious seasonal variations in the species composition and predominant species. The abundances of phytoplankton in all the stations ranged from 0.08×10⁵ cells·m^-3 to 108.48×10⁵ cells·m^-3 in Haizhou Bay. The average annual density of phytoplankton was 10.71×10⁵ cells·m^-3, being the highest in autumn (29.08×10⁵ cells·m^-3) and the lowest in summer (1.69×10⁵ cells·m^-3). The Shannon index, Pielou index and Margalef index of the phytoplankton community were higher in summer and autumn than in winter and spring. CCA suggested that the main factors affecting the phytoplankton community were sea surface temperature (SST), followed by nutrients (NO₃^--N, PO₄^3--P, SiO₃^2--Si) and dissolved oxygen (DO). The abundances and distribution of some dominant species were closely related with these main factors.

Impact of salinity on nitrification in the process of biological nitrogen removal and its mechanism: A review.

XU Han-li, LIANG Zhi-wei, MAO Wei, WANG Cun-bao, WU Wei-xiang

2014, 25(7):  2132-2140. 

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Wastewater with high salinity is widely distributed, biological nitrogen removal process is inhibited by salt when it is used to treat wastewater containing high concentration of salt and ammonium. Nitrification is the key step of biological nitrogen removal process, thus researching the effect of salinity on nitrification is significant. In this article, the research progress of the impact of salinity on wastewater biological nitrification process  was summarized. The influences of salinity stress on various aspects of nitrification process, including the efficiency of ammonia oxidation and nitrite oxidation processes, and the structure of aggregates, the characteristics of flocs and microbial community structure, were analyzed. The mechanism of nitrification process under high salinity was elaborated, providing a theoretical advice for designing biological nitrogen removal system of wastewater with high concentration of salt and ammonium.

Influence of sulfur on the speciation transformation and phyto-availability of heavy metals in soil: A review.

SUN Li-juan, DUAN De-chao, PENG Cheng, HE Jun-yu, SHI Ji-yan

2014, 25(7):  2141-2148. 

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The biogeochemical cycle of sulfur can directly affect the speciation transformation of heavy metals in soils and their accumulation in plants. The toxicity of heavy metals in plants can be alleviated by their complexation with sulfur compounds like phytochelatins or metallothiones, consisting of the major mechanisms of phytodetoxification. Sulfur deficiency is becoming one of the limiting factors that influence Chinese agricultural production. Although the applications of sulfur fertilizer in soil have received much attention in recent years, the interaction mechanism of heavy metal with sulfur metabolism has not been studied extensively. In this paper, we reviewed current research advance on the impact of sulfur on the speciation transformation of soil heavy metals and their accumulation in plants, discussed the effect of sulfur on the detoxification mechanism of heavy metal in plants and provided further research prospective in this field.