Table of Content

18 July 2015, Volume 26 Issue 7

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Soil organic carbon pools and their turnover under two different types of forest in  Xiaoxing’〖KG-*3〗an Mountains, Northeast China.

2015, 26(7):  1913-1920. 

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Soil samples collected from virgin Korean pine forest and broadleaved secondary forest in Xiaoxing’〖KG-*3〗an Mountains, Northeast China were incubated in laboratory at different temperatures (8, 18 and 28 ℃) for 160 days, and the data from the incubation experiment were fitted to a threecompartment, firstorder kinetic model which separated soil organic carbon (SOC) into active, slow, and resistant carbon pools. Results showed that the soil organic carbon mineralization rates and the cumulative amount of C mineralized (all based on per unit of dry soil mass) of the broadleaved secondary forest were both higher than that of the virgin Korean pine forest, whereas the
mineralized C accounted for a relatively smaller part of SOC in the broadleaved secondary forest soil. Soil active and slow carbon pools decreased with soil depth, while their proportions in SOC increased. Soil resistant carbon pool and its contribution to SOC were both greater in the broadleaved secondary forest soil than in the virgin Korean pine forest soil, suggesting that the broadleaved secondary forest soil organic carbon was relatively more stable. The mean retention time (MRT) of soil active carbon pool ranged from 9 to 24 d, decreasing with soil depth; while the MRT of slow carbon pool varied between 7 and 24 a, increasing with soil depth. Soil active carbon pool and its proportion in SOC increased linearly with incubation temperature, and consequently, decreased the slow carbon pool. Virgin Korean pine forest soils exhibited a higher increasing rate of active carbon pool along temperature gradient than the broadleaved secondary forest soils, indicating that the organic carbon pool of virgin Korean pine forest soil was relatively more sensitive to temperature change.

Traitbased responses and adaptation of Artemisia sacrorum to environmental changes.

QI De-hui1, WEN Zhong-ming1，2，3, YANG Shi-suo2, WANG Hong-xia2, GUO Ru3

2015, 26(7):  1921-1927. 

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The paper focused on Artemisia sacrorum in the stable natural plant community in three vegetation zones (forest, forest steppe and steppe) in the Yanhe River catchment. The following plant functional traits were measured at each sample site, i.e., specific leaf area (SLA), leaf tissue density (LTD), leaf nitrogen concentration (LNC), leaf phosphorus concentration (LPC), leaf nitrogen phosphorus ratio (LNP), specific root length (SRL), root tissue density (RTD), root nitrogen concentration (RNC), root phosphorus concentration (RPC) and root nitrogen phosphorus ratio (RNP). These 10 plant functional traits were chosen because they were easily measurable and adequately reflected plant survival strategies. We analyzed intraspecific differences in A. sacrorum functional traits in the different habitat zones, and the influence of climate and terrain factors on A. sacrorum functional traits. We also studied the relationships among A. sacrorum plant functional traits. The results showed that some A. sacrorum functional traits were significantly different among sample sites, such as LPC, LNP, SRL, RTD and RNP, while the other 5 functional traits had no significant differences. The functional traits were not significantly different between sites with different slopes and aspects. SLA was very significantly negatively correlated with LTD, SRL was significantly negatively correlated with RTD and RNP, RTD was significantly positively correlated with RNC and RNP, and there were no significant relationships among LTD, LNC and LNP and the other functional traits. This showed that A. sacrorum adapted to the environment by coordinating adjustment among leaf and root functional traits. Different climate factors had different effects on plant traits, with the effects of mean annual precipitation > mean annual temperature > annual average evaporation capacity.

Characteristics of leaf carbon, nitrogen and phosphorus stoichiometry in relation to plant size of Machilus pauhoi.

ZHANG Lei-lei1,2,3, ZHONG Quan-lin1,2,3, CHENG Dong-liang1,2,3, ZHANG Zhong-rui1,2,3, FEI Ling1,2,3, XU Chao-bin1,2,3, HE Li-zhong4, WANG Wei-jun5

2015, 26(7):  1928-1934. 

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To explore the effects of stand age on variation patterns of leaf C, N, P stoichiometric characteristics of Machilus pauhoi, two stands, i.e., 9 and 13 years old, were selected. The relationships between leaf nutrient contents (C, N and P) and diameters at breast height (DBH) of individual plants were analyzed. The data revealed that the individual variations of seedlings in M. pauhoi stands were strengthened with the stand development. The stand age had significant effects on leaf C, N, P contents and C：N ratio but not on C：P and N：P ratios. Specifically, the mean values of leaf C, N, P contents and N：P ratio in the 9-year-old stand were lower than those in the 13-year-old stand, whereas, inverse pattern of C：N and C：P ratios were found in the two stands. Furthermore, leaf N and P stoichiometry varied significantly within the stand. Specifically, leaf N and P contents, as well as their stoichiometric ratios, linearly correlated with DBH in the 9-year-old stand. On the contrary, leaf N and P stoichiometry showed quadratic correlation in 13-year-old stand (except leaf C：N which linearly correlated with DBH). Lastly, nutrient transfer rates of leaf N and P in the 9-year-old stand were higher than that in 13-year-old stand, and the discrepancies of leaf nutrient transfer strategy between growing and non-growing seasons were caused by the different growth phases and environmental conditions.

Climategrowth relationships of Picea koraiensis and causes of its recent decline in Xiaoxing’an Mountains, China.

YAO Qi-chao1, WANG Xiao-chun2, XIAO Xing-wei1,3

2015, 26(7):  1935-1944. 

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Two treering width chronologies of Picea koraiensis at two altitudes in Fenglin National Nature Reserve of Xiaoxing’〖KG-*4〗an Mountains, China were developed by using dendrochronological methods. To identify main limiting factors of P. koraiensis radial growth at the two altitudes, the relationships between the chronologies and local temperature, precipitation, Palmer drought severity index (PDSI), and largescale climatic factors were investigated. Meanwhile, the reasons of P. koraiensis growth decline in recent years were also explored. Results showed that radial growth of P. koraiensis in Xiaoxing’〖KG-*4〗an Mountains was mainly limited by temperatures, especially by the minimum temperature in growing season, while the limiting effect of precipitation was relatively weak. Climate responses of P. koraiensis growth at the different altitudes showed significant differences. Radial growths of P. koraiensis at the low altitude were positively correlated with precipitation in the current growth season (June-September) and whole year, and negatively correlated with soil temperatures at different depths, especially at 80 cm depth in growing season. Meanwhile, it was significantly positively correlated with PDSI in growing season. However, the relationships between radial growth of P. koraiensis at the high altitude and precipitation, air and soil temperatures, and PDSI were not significant as that at the low altitude. Growth decline of P. koraiensis in Xiaoxing’〖KG-*4〗an Mountains could be related to the phase changes in Atlantic multidecadal oscillation (AMO) and Pacific decadal oscillation (PDO) and the significant global warming since 1980. The coupling effects of the above changes might result in increased soil evaporation and exacerbated warming and drying phenomena, consequently causing the growth decline of P. koraiensis at the low altitude.

Evaluation of the tree form quality of middleaged Pinus tabuliformis plantation under different canopy densities in Huanglong Mountains, Northwest China.

YOU Jian-jian, ZHANG Wen-hui, DENG Lei

2015, 26(7):  1945-1953. 

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To clarify the effects of different canopy densities on tree form quality of Pinus tabuliformis, a hierarchical indicator system was structured, which brought about a set of grading criteria to evaluate tree form quality of the middleaged P. tabuliformis plantation under four canopy densities in Huanglong Mountains by using the analytic hierarchy process (AHP). Plots were divided into four classes according to the stand canopy density (CD): CD＜0.65(type 1)， 0.65≤CD＜0.75(type 2)， 0.75≤CD＜0.85 (type 3)  and CD≥0.85 (type 4). The results indicated that, by comprehensive analysis of ten related indicators, i.e.,  diameter at breast height (DBH), tree height, diameter height ratio, taperingness, stem straightness, forking ratio, height under living branch, number of branches, maxbranch base diameter and average base diameter of branches, the tree form quality could be evaluated. Among these factors, stem straightness, forking ratio and DBH were the most important ones influencing the tree form quality with a total weight of 0.7382. So, these three indicators were the major determinants of tree form quality. The comprehensive scores of the tree form quality evaluations fluctuated as the canopy density decreased and topped at 90.28 when CD was valued at 0.75 (type 2). The indicators and evaluation system developed in this study were easy to operate, and quite fit for solving the quantity problem of the tree form quality evaluation. Our system would be capable for applications in evaluating the tree form quality of other tree species on the Loess Plateau.

Effects of biochar on CO₂ and N₂O emissions and microbial properties of tea garden soils.

HU Yun-fei, LI Rong-lin, YANG Yi-yang

2015, 26(7):  1954-1960. 

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To clarify the effects of biochar addition (0.5%, 1.5%, 2.5%, 3.5%) on the emission of carbon dioxide (CO₂) and nitrous oxide (N₂O), pH and microbial communities of the tea garden soil, an indoor incubation experiment was conducted using the acidulated teaplanted soil. Results showed that the emissions of CO₂ and N₂O and the rate of C, N mineralization were increased in a short term after the addition of biochar  compared with the control, while the promoting effect was weakened along with increasing the addition of biochar. The pH, dehydrogenase activity and  microbial biomass carbon were increased in the biochar treatments. Phospholipid fatty acid (PLFA) with different markers was measured and the most PLFA was detected in the group in the 1.5% biochar treatment with significant differences (P<0.05) compared with the control. In addition, the higher levels of 16:0, 14:0 (bacteria), 18:1ω9c (fungi), 10Me18:0 (actinomycetes) groups were observed and there were significant differences (P<0.05) in individual phospholipid fatty acid among the different treatments. Taken together, the acidulated teaplanted soil, soil microbial biomass and microbial number were improved after addition of biochar.

Distribution and enrichment characteristics of organic carbon and total nitrogen in mollisols under long-term fertilization.

XU Xiang-ru1,2, LUO Kun2, ZHOU Bao-ku3, WANG Jing-kuan1, ZHANG Wen-ju2, XU Ming-gang2

2015, 26(7):  1961-1968. 

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The characteristics and changes of soil organic carbon (SOC) and total nitrogen (TN) in different size particles of soil under different agricultural practices are the basis for better understanding soil carbon sequestration of mollisols. Based on a 31-year long-term field experiment located at the Heilongjiang Academy of Agricultural Sciences (Harbin), soil samples under six treatments were separated by sizefractionation method to explore changes and distribution of SOC and TN in coarse sand, fine sand, silt and clay from the top layer (0-20 cm) and subsurface layer (20-40 cm). Results showed that long-term application of manure (M) increased the percentages of SOC and TN in coarse sand and clay size fractions. In the top layer, application of nitrogen, phosphorus and potassium fertilizers combined with manure (NPKM) increased the percentages of SOC and TN in coarse sand by 191.3% and 179.3% compared with the control (CK), whereas M application increased the percentages of SOC and TN in clay by 45% and 47% respectively. For subsurface layers, the increase rates of SOC and TN in corresponding parts were lower than that in top layer. In the surface and subsurface layers, the percentages of SOC storage in silt size fraction accounted for 42%-63% and 48%-54%, TN storage accounted for 34%-59% and 41%-47%, respectively. The enrichment factors of SOC and TN in coarse sand and clay fractions of surface layers increased significantly under the treatments with manure. The SOC and TN enrichment factors were highest in the NPKM, being 2.30 and 1.88, respectively, while that in the clay fraction changed little in the subsurface layer.

Effects of biochar on water thermal properties and aggregate stability of Lou soil.

SHANG Jie, GENG Zeng-chao, ZHAO Jun, GENG Rong, ZHAO Ying-cui

2015, 26(7):  1969-1976. 

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A field trail was carried out to study the impact of biochar on soil bulk density, soil moisture content, soil temperature and soil aggregate stability in Lou soil. Five treatments of different biochar amounts were set in this study as follows: 0 (B₀), 20 (B₂₀), 40 (B₄₀), 60 (B₆₀), 80 (B₈₀) t·hm^-2. The results showed that, after applying biochar two years, compared with the control(B₀), the soil bulk density in 0-30 cm soil layer significantly decreased by 7.7%-10.9%, and the soil moisture content significantly increased by 10.0%-13.4%. Applying biochar at 40-60 t·hm^-2 could buffer the change of soil temperature, and increase the soil thermal capacity. The water stable aggregates (WR_0.25) with diameters  greater than 0.25 mm significantly increased by 30.3%, the mean mass diameter (MWD) under dry sieving and wet sieving significantly increased by 15.2% and 31.6%, respectively, and the proportion of aggregate destruction (PAD) and unstable aggregate index (E_LT) significantly decreased by 19.1% and 17.5%, respectively. The results indicated that applying biochar could significantly improve the  water thermal properties of Lou soil and increase soil aggregate stability, and the best applying amount was 40-60 t·hm^-2.

Effects of tobacco garlic crop rotation and intercropping on tobacco yield and rhizosphere soil phosphorus fractions.

TANG Biao1, ZHANG Xi-zhou1, YANG Xian-bin1,2

2015, 26(7):  1977-1984. 

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A field plot experiment was conducted to investigate the tobacco yield and different forms of soil phosphorus under tobacco garlic crop rotation and intercropping patterns. The results showed that compared with tobacco monoculture, the tobacco yield and proportion of middle/high class of tobacco leaves to total leaves were significantly increased in tobacco garlic crop rotation and intercropping, and the rhizosphere soil available phosphorus contents were 1.3 and 1.7 times as high as that of tobacco monoculture at mature stage of lower leaf. For the inorganic phosphorus in rhizos phere and non-rhizosphere soil in different treatments, the contents of O-P and Fe-P were the highest, followed by Ca₂-P and Al-P, and Ca₈-P and Ca₁₀-P were the lowest. Compared with tobacco monoculture and tobacco garlic crop intercropping, the Ca₂-P concentration in rhizosphere soil under tobacco garlic crop rotation at mature stage of upper leaf, the Ca₈-P concentration at mature stage of lower leaf, and the Ca₁₀-P concentration at mature stage of middle leaf were lowest. The Al-P concentrations under tobacco garlic crop rotation and intercropping were 1.6 and 1.9 times, and 1.2 and 1.9 times as much as that under tobacco monoculture in rhizosphere soil at mature stages of lower leaf and middle leaf, respectively. The OP concentrations in rhizosphere soil under tobacco garlic crop rotation and intercropping were significantly lower than that under tobacco monoculture. Compared with tobacco garlic crop intercropping, the tobacco garlic crop rotation could better improve tobacco yield and the proportion of high and middle class leaf by activating O-P, Ca₁₀-P and resistant organic phosphorus in soil.

Dynamics of soil phosphorus adsorption-desorption in maize/soybean relay intercropping system in purple hilly area.

XU Min1, SONG Chun1,2, DAI Wei2, XIAO Xia1, MAO Lu1, WANG Xiao-chun2, YANG Wen-yu2

2015, 26(7):  1985-1991. 

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Field plot experiment was carried out to study the effect of phosphorus application on soil phosphorus adsorptiondesorption characteristics under three cropping patterns including maize/soybean relay intercropping (M/S), maize monoculture (M), and soybean monoculture (S). Results showed that without phosphorus fertilization, the system crop yield under M/S was increased by 9.8% and 79.1% compared with that of M and S, respectively, and the land equivalent ratio (LER)  was 1.58. With phosphate fertilizer application, the system crop yield under M/S was increased by 10.4% and 80.3% compared with that of M and S, respectively, and the  LER was 1.62. The system crop yields under M/S, M and S with phosphate fertilizer application were increased by 12.7%, 12.2% and 17.6%, respectively, compared with that without phosphorus fertilization. Among three cropping patterns, the soil buffer capacity (SBC) values were in the order of M/S>M>S regardless of phosphate fertilizer applied or not. The SBC values of M/S, M and S without phosphate fertilizer application were reduced by 19.6%, 30.3% and 12.0% compared with phosphate fertilizer application treatments, respectively. The soil desorption per absorption (b) values of the three cropping patterns with phosphate fertilizer application were in the order of M/S>M>S, and the  b values increased by 10.9%, 39.1% and -9.6%, respectively, compared with non phosphate fertilizer application. The soil phosphorus maximum absorption (Q_m) and soil phosphorus desorption rate also showed the same trend.

Characteristics of farmland eco-environment at the intercropping stage of maize intercropped with winter wheat and their effects on seedling growth of summer maize.

ZHU Yuan-gang1,2, LI Hong-jie2, CUI Xin-yan3, JIA Chun-lan4, YANG Jin-sheng4, LIU Shao-kun4, ZHANG Ji-wang1, DONG Shu-ting1

2015, 26(7):  1992-1998. 

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To study the farmland eco-environment of intercropping maize with wheat at the intercropping stage and its influence on maize seedling growth, two summer maize cultivars, Zhengdan 958 and Denghai 661, were either intercropped with wheat or directly seeded. The result demonstrated that there was little difference for the soil water content of the farmland between the two cultivation methods. The highest soil temperature of intercropped maize was 4.8-5.2 ℃ lower than the soil temperature of directlyseeded maize, and the lowest temperature of the intercropped maize was 1.4-1.7 ℃ lower. But, the temperatures for both planting methods met the requirement for seed germination. Light intensity on the ground surface of the intercropped maize was 4.4%-10.6% less than natural light, and insufficient light was the main reason for the weak and late seedling. Compared to the directlyseeded maize, the speeds of seed germination and accumulation of dry matters of the intercropped maize were relatively slow. On the whole, the seedling of intercropped maize was not strong, which presented small leaves, short height and low chlorophyll content. The restraint on the growth of intercropped maize was enhanced with the extension of intercropping period. For farm planting, directseeding could improve the seed germination and seedling growth of summer maize.

Effects of dicyandiamide combined with nitrogen fertilizer on N₂O emission and economic benefit in  winter wheat and summer maize rotation system.

WANG Yan-qun1, LI Ying-chun2, PENG Zheng-ping1, WANG Chao-dong1, LIU Ya-nan1

2015, 26(7):  1999-2006. 

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Aiming at the problems of excessive and unreasonable fertilizer application, lower nitrogen use efficiency, increasing N₂O emission from soil and fertilizer in current intensified agricultural productions, a field experiment was conducted to study the effects of dicyandiamide (DCD) combined with nitrogen fertilizer application at different levels, i.e., 150, 225, 300 kg·hm^-2, on N₂O emission and relevant economic benefit in a typical winter wheatsummer maize rotation system in North China Plain. The results showed that DCD application decreased N₂O emission fluxes and cumulative emissions by 25.6%-32.1% and 23.1%-31.1% in the yearround. There was a significant positive exponential correlation between N₂O flux and soil surface temperature or soil moisture content. The effect of soil moisture on  N₂O emission was stronger in wheat season than in maize season, while the effect of temperature on N₂O emission was on the contrary. The yields of winter wheat and summer maize with DCD addition were increased by 16.7%-24.6% and 29.8%-34.5%, respectively, and the average economic income of two seasons was increased by 7973.2 yuan·hm^-2. Therefore, appropriate rate of N fertilizer combined with DCD could not only increase crop yield and economic income, but also reduce N₂O emission. Considering environmental and economic benefit under this experimental condition, DCD combined with nitrogen of moderate level (total N amount 225 kg·hm^-2) was a good nitrogen management mode in North China.

Effects of low temperature on formation of spikelets and grain filling of indica inbred rice during panicle initiation in early-season.

ZENG Yan-hua1,2, ZHANG Yu-ping2, XIANG Jing2, WANG Ya-liang2, CHEN Hui-zhe2, ZHU De-feng2

2015, 26(7):  2007-2014. 

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A pot experiment in phytotron with controlled temperature was conducted to examine the effects of low temperature (LT) on differentiation and retrogression of branches and spikelets and grain filling of rice during panicle initiation (PI). In this study, indica inbred rice called Zhongjiazao17 was planted and treated at 17 and 20 ℃ of LT during primary branches anlage differentiation (Ⅱ) and pollen mother cell meiosis stage (Ⅵ) of PI. The results showed that the numbers of differentiated and survived branches per panicle were significantly reduced under LT treatment compared with control, and the number of survived spikelets was significantly decreased by 7.2%-12.4%, but the numbers of retrograded branches and spikelets were increased. Moreover, LT affected significantly the development of floral organ such as pollen activity and anther dehiscence, and caused harmful grain filling, particularly at 17 ℃. The numbers of total differentiated and survived branches and spikelets were lower during Ⅵ (PI) than during Ⅱ (PI) under LT stress, but more retrograded secondary branches and spikelets (increased by 11.6%) were found during Ⅵ (PI) compared with Ⅱ (PI). Meanwhile, in contrast to Ⅱ (PI), the seed setting rate was significantly lowered by 3.7% during Ⅵ (PI), which was attributed to reductions in pollen activity, pollen grains on stigma, anther dehiscence coefficient and grain filling rate. LT stress impact on rice panicles was higher at 17 ℃ than at 20 ℃ during Ⅱ and Ⅵ (PI). The cultivation measure could be correspondingly strengthened and improved in practice.


 

Changes of endogenous hormone contents and antioxidative enzyme activities in wheat leaves under low temperature stress at jointing stage.

LI Chun-yan, XU Wen, LIU Li-wei, YANG Jing, ZHU Xin-kai, GUO Wen-shan

2015, 26(7):  2015-2022. 

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Low temperature stresses (-3 and -5 ℃) were simulated using artificial temperaturecontrolled phytotrons to study the freezing rate, the contents of endogenous hormones, and the activities of antioxidative enzymes in the leaves of wheat plants of Yangmai 16 (YM 16) and Xumai 30 (XM 30) at jointing stage. The grade and index of freezing injury increased with lower temperature and longer stress. The freezing rate was at the 5th level and the main stems and tillers of both cultivars were finally dead under -5 ℃ lasting for 72 h. On the last day of stress initiation, the contents of abscisic acid (ABA) and zeatin riboside (ZR), and the activities of superoxide dismutase (SOD), peroxide dismutase (POD), and catalase (CAT) in leaves increased at the beginning and then declined as low temperature progressed. On the 3rd day after stress, the contents of ABA and ZR and the activities of antioxidative enzymes were higher than those on the last day of cold stress, and then reduced to the level of the control on the 6th day after stress. The content of gibberellins (GA₃) was lowered by cold stress. For YM 16, GA₃ content increased from the 3rd day to the 6th day after cold stress, whereas, for XM 30, it increased first and then decreased. For the treatment of -5 ℃ lasting for 72 h, the contents of hormones and the activities of antioxidative enzymes were significantly lower than those of the other treatments. Correlation analyses showed that higher ABA and ZR contents,  and higher SOD, POD and CAT activities as well as lower GA₃ content could alleviate the low-temperature injury in wheat plants under low temperature stress.

Ecological adaptability evaluation of peanut cultivars based on biomass and nutrient accumulation.

WANG Xue1, CUI Shao-xiong1, SUN Zhi-mei1, MU Guo-jun2, CUI Shun-li2, WANG Peng-chao2, LIU Li-feng2

2015, 26(7):  2023-2029. 

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To identify the good peanut cultivars with the properties of high yield, high nutrient use efficiency and wide adaptability, 19 selected peanut cultivars were planted in the low champaign area and piedmont plain area of Hebei Province. By using principal component analysis, the adaptability of these 19 cultivars was evaluated for different ecological regions through comparing their 16 main traits including biomass and nutrient parameters. According to the critical value of principal component (>1.0), the 16 biomass and nutrient characteristics were integrated into 4 principal components which accounted for 85% of the original information. The results indicated that there were obvious differences in yield and nutrient use efficiency for the peanut cultivars in different ecological regions. The 19 peanut cultivars were classified into 2 groups according to their ecological adaptability, and the cultivars from the group with wide adaptability could further be divided into 3 categories  according to their yield and nutrient use efficiency. Among these cultivars,  Yuhua 9719, Jihua 0212-4, Weihua 10, Yuhua 15, Puhua 28 and Jihua 10 were selected as the better peanut cultivars with the properties of high yield, high nutrient use efficiency and wide adaptability.

Effects of different water potentials on leaf gas exchange and chlorophyll fluorescence parameters of cucumber during postflowering growth stage.

LIN Lu1,2, TANG Yun2, ZHANG Ji-tao2, YAN Wan-li2, XIAO Jian-hong2, DING Chao2, DONG Chuan1, JI Zeng-shun2

2015, 26(7):  2030-2040. 

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Impacts of different substrate water potentials (SWP) on leaf gas exchange and chlorophyll fluorescence parameters of greenhouse cucumber during its postflowering growth stage were analyzed in this study. The results demonstrated that -10 and -30 kPa were the critical values for initiating stomatal and nonstomatal limitation of drought stress, respectively. During the stage of no drought stress (-10 kPa<SWP≤0 kPa), gas exchange parameters and chlorophyll fluorescence parameters were not different significantly  among treatments. During the stage of stomatal limitation of drought stress (-30 kPa<SWP≤-10 kPa), with the decrease of SWP, the stomatal conductance (g_s), intercellular carbon dioxide concentration (C_i), net photosynthetic rate (P_n), apparent quantum efficiency (ε), transpiration rate (T_r), carboxylation efficiency (CE), maximum Rubisco
limited rate of carboxylation (V_{c max}), maximum rate of electron transport (J_max), rate of triosephosphate utilization (V_TPU), maximum and actual quantum efficiency of PSII (Φ_PSⅡ and F_v/F_m) and photochemical quenching (q_P) decreased, but the light compensation point (LCP), dark respiration rate (R_d), carbon dioxide compensation point (CCP), stomatal limitation value (L_s), instantaneous water use efficiency (WUE_i) and non-photochemical quenching (q_N) increased. In this stage, gas exchange parameters changed faster than chlorophyll fluorescence parameters and differed significantly among treatments. During the stage of nonstomatal limitation of drought stress (-45 kPa≤SWP≤-30 kPa), with the decrease of SWP, light saturation point (LSP), R_d, CE, V_{c max}, V_TPU, L_s, WUE_i, Φ_PSII, F_v/F_m and q_P decreased, while CCP, C_i and q_N increased. In this stage, chlorophyll fluorescence parameters changed faster than gas exchange parameters and differed significantly among treatments. In production of greenhouse cucumber, -10 and -5 kPa should be the lower and upper limit value of irrigation, respectively. The stomatal limitation of drought stress could be relieved by irrigation before SWP decreased to -30 kPa. While, the non-stomatal injury of drought stress would be unrecoverable once SWP decreased to lower than -30 kPa.

Roles of phenylalanine ammonia-lyase in low temperature tolerance in cucumber seedlings.

DONG Chun-juan, LI Liang, CAO Ning, SHANG Qing-mao, ZHANG Zhi-gang

2015, 26(7):  2041-2049. 

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To reveal the roles of phenylalanine ammonia-lyase (PAL) in low temperature tolerance in cucumber seedlings, a specific PAL inhibitor (AOPP) was sprayed to the seedlings, and then the stress tolerance was determined. The results suggested that both gene expression and enzymatic activity of PAL in cucumber leaves were induced under low temperature. The seedlings pretreated with AOPP showed lower PAL activity and less accumulation of phenolics and flavonoids. Low temperature caused damages in cucumber seedlings, and pretreatment of AOPP aggravated these damages. Compared to the control, the seedlings pretreated with AOPP showed significantly higher relative electrolyte leakage and MDA production, lower maximum photochemical efficiency of PSII (F_v/F_m) but higher photochemical quenching coefficient Y(NO)， and reduced expression of low temperatureresponsive genes (PR1-1a, COR47, P5CS and HSP70). In cucumber seedlings, low temperature stress induced the accumulation of H₂O₂, increased the contents of ascobate (AsA) but decreased the contents of dehydroascobate (DHA), and thus reduced the value of AsA:DHA. In the AOPPpretreated seedlings, the activities of antioxidant enzymes (CAT and APX) were significantly repressed, and excess H₂O₂ accumulated. The value of AsA:DHA was also lower than the control. Furthermore, coapplication of H₂O₂ scavenger alleviated the low temperatureinduced damages in the AOPPpretreated seedlings, while coapplication of a CAT inhibitor made the seedlings more sensitive to low temperature stress. These results indicated that under low temperature stress, the enhanced activities of PAL could increase the biosynthesis of phenylpropanoid compounds and activate the cellular antioxidant enzymes, which could scavenge the excess ROS and maintain the cellular redox status, and thereby reduce the photo and oxidative damages caused by low temperature stress.

Effects of selenite addition on selenium absorption, root morphology and physiological characteristics of rape seedlings.

LIU Xin-wei1,2, WANG Qiao-lan3, DUAN Bi-hui1,2, LIN Ya-meng1,2, ZHAO Xiao-hu1,2, HU Cheng-xiao1,2, ZHAO Zhu-qing1,2

2015, 26(7):  2050-2056. 

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The rape (Brassica napus L. cv. Xiangnongyou 571) was chosen as the experimental material to undergo solution cultivation at seedling stage to investigate the effects of selenite addition on the selenium (Se) absorption and distribution, root morphology and physiological characteristics of rape seedlings. The results showed that the bioaccumulation ability of Se decreased significantly with increasing the Se application rate, but the Se distribution coefficient remained around 0.9 with no significant influence. The application of 10 μmol·L^-1 selenite stimulated the growth of rape seedlings through improving the root physiological characteristics and root morphology significantly, including significantly increasing the production of superoxide radical (O₂^-_·) rate and the activities of superoxide dismutase (SOD), peroxidase (POD) and fungal catalase (CAT) in the root system, which resulted in a reduction of the lipids peroxidation (MDA) content as much as 26.0%, consequently increasing the root activity as much as 17.4%. The promoting degrees of selenite on root morphological parameters were from strong to weak in such a tendency: root volume > total surface area > number of root forks > total root length > number of root tips > average diameter. However, such positive effects had no significant difference with those in treatment with 1 μmol·L^-1 selenite, indicating that small amounts (≤10 μmol·L^-1) of selenite were able to increase the activity of antioxidant enzymes and reduce the content of MDA in root system, which could increase root activity and improve root morphology, hence increased the biomass of rape seedlings.

Effect of atmospheric CO₂ concentration and nitrogen application level on absorption and transportation of nutrient elements in oilseed rape.

WANG Wen-ming1, ZHANG Zhen-hua1, SONG Hai-xing1, LIU Qiang1, RONG Xiang-min1, GUAN Chun-yun2, ZENG Jing1, YUAN Dan1

2015, 26(7):  2057-2062. 

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Effect of elevated atmosphericCO₂〖KG*3〗(780 μmol·mol ^-1) on the absorption and transportation of secondary nutrient elements (calcium, magnesium, sulphur) and micronutrient elements (iron, manganese, zinc, molybdenum and boron) in oilseed rape at the stem elongation stage were studied by greenhouse simulated method. Compared with the ambient CO₂ condition, the content of Zn in stem was increased and the contents of other nutrient elements were decreased under the elevated atmosphericCO₂ with no nitrogen (N) application; the contents of Ca, S, B and Zn were increased, and the contents of Mg, Mn, Mo and Fe were decreased under the elevated atmosphericCO₂ with N application (0.2 g N·kg^-1 soil); except the content of Mo in leaf was increased, the contents of other nutrient elements were decreased under the elevated atmosphericCO₂ with two levels of N application. Compared with the ambient CO₂ condition, the amounts of Ca and S relative to the total amount of secondary nutrient elements in stem and the amounts of B and Zn relative to the total amount of micronutrient elements in stem were increased under the elevatedCO₂ treatment with both levels of N application, and the corresponding values of Mg, Fe, Mn and Mo were decreased; noN application treatment increased the proportion of Ca distributed into the leaves, and the proportion of Mg distributed into leaves was increased by the normalN application level; the proportions of Mn, Zn and Mo distributed into the leaves were increased at both N application levels. Without N application, the elevation of atmospheric CO₂ increased the transport coefficients of S_Fe,Mo and _SS,B, but decreased the transport coefficients of S_Mg,Fe, S_Mg,Mn and S_S,Fe, indicating the proportions of Mo, S transported into the upper part of plant tissues was higher than that of Fe, and the corresponding value of B was higher than that observed for S, the corresponding value of Mg was higher than that of Fe and Mn. Under normalN application, the elevation of atmospheric CO₂ increased the transport coefficients of S_Mg,Fe, S_Mg,Mn and S_S,B, but decreased the transport coefficients of S_Ca,Mg, S_Fe,Mo and S_S,Fe, indicating the proportions of Fe, Mn and Ca transported into the upper part of plant tissues was higher than that of Mg; the corresponding value of B was higher than that observed for S, the corresponding value of Fe was higher than that of Mo, and the corresponding value of S was higher than that of Fe.

Mechanism of dwarfing effect of tomato (Solanum lycopersicon) seedlings induced by cold-shock treatment under high temperature stress.

LI Sheng-li1, BI Ming-ming1, CHEN Fei2, SUN Zhi-qiang1

2015, 26(7):  2063-2068. 

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To explore the dwarfing mechanism of tomato seedlings induced by coldshock treatment followed by high temperature, tomato seedlings were subjected to coldshock treatment once a day at 8:00 with temperature of 5, 10 and 15 ℃ for 10, 20 and 30 min, respectively, and ethylene production rate was measured. Plant height, ethylene production and gibberellin (GA₃) content of the seedlings treated with T10 ℃D10 min (coldshock with 10 ℃ for 10 min), coupled with utilization of growth regulators, were also evaluated. The results showed that the release of ethylene was increased with the decrease of coldshock temperature and extension of treatment time. The coldshock treatment of 5 ℃ and 30 min had the highest ethylene production rate of 60.3 nL·h^-1·g^-1, which was 6.5 times of the control. None of ethephon (ETH), silver thiosulphate (STS), GA₃ or paclobutrazol (PP333) could completely block high ethylene production induced by coldshock treatment. Tomato seedlings with coldshock treatment (T10 ℃D10 min) resulted in reduction in GA₃ content by 38.1% compared with the value of control (130.6 μg·g^-1). Neither ethephon nor STS had significant effect on the dwarfing induced by coldshock. However, GA₃ weakened the dwarfing effect induced by coldshock treatment (T10 ℃D10 min), while PP333 greatly enhanced it. The dwarfing effect by coldshock treatment of T10 ℃D10 min was equivalent to that of application of 4.0 mg·L^-1 PP333 based on the seedling height as an evaluation indicator. It was concluded that coldshock treatment stimulated shoot ethylene production and blocked GA₃ synthesis. GA₃ played a vital role in dwarfing effect on tomato seedling induced by cold-shock treatment. Coldshock with 10 ℃ and duration of 10 min could promote the growth of tomato seedlings with shorter stem and higher dry mass accumulation.

Effect of root-zone CO₂ enrichment on tomato photosynthetic physiology.

ZHAO Xu1, LIU Yan-zhi2, LI Tian-lai3, SUN Zhou-ping3

2015, 26(7):  2069-2073. 

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The root system of tomato plant (Lycopersicon esculentum L. cv. Liaoyuanduoli) was treated with CO₂ enrichment by aeroponical culture for 60 days. The experiment showed that the chlorophyll content and leaf area of tomato plant were significantly lower under 2500 μL·L^-1 or above CO₂ condition of root zones than under 370 μL·L^-1 CO₂ condition. At the same time the Ca²⁺ATPase, Mg²⁺ATPase and phosphoenolpyruvate carboxylase (PEPC) of plant leaf were significantly reduced while the PEPC of root increased significantly, which resulted in the significant decreases of net photosynthetic rate, stomatal conductance and intercellular CO₂ concentration of plant leaves. The results indicated that under a longterm root-zone CO₂ enrichment condition, the decline of photosynthetic physiological parameters of tomato leaf maybe mainly result from the increased PEPC of root, and the decreased CO₂ fixation, Mg²⁺ATPase and Ca²⁺ATPase of leaves.

 

Response of cotton seeding date to climate warming in Northern Slope Economic Zone of Tianshan Mountain, China.

ZHI Juan1, ZHANG Shan-qing2, XU Wen-xiu3, TIAN Yan-jun3，ZHANG Na3， SU Li-li3

2015, 26(7):  2074-2082. 

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Based on the meteorological date acquired from 11 meteorological stations in Northern Slope Economic Zone of Tianshan Mountain during 1971-2010 and by using the methods of linear regression, ttest technique and IDW interpolation, this paper analyzed the spatial distribution of each tenday average temperature from late March to late April and beginning date of ≥12 ℃ to understand the effect of climate change on the cotton seeding date. Results showed that each tenday average temperature from late March to late April increased by 0.8, 0.5, 0.1 and 0.5 ℃·(10 a)^-1, but the beginning date of ≥12 ℃ advanced by 0.5 d·(10 a)^-1 during 1971-2010. All meteorological elements in this research ascended abruptly in the 1990s. The abrupt climate change made each tenday average temperature increasing by 2.5, 1.9, 1.1 and 1.5 ℃, to 7.2, 10.0, 13.2 and 15.6 ℃, respectively from late March to late April. The high values of each tenday average temperature from late March to late April expanded the scope of main cotton producing areas in Northern Slope Economic Zone of Tianshan Mountain, such as Wusu, Sawan and Manasi, and the low values were observed in Urmuqi. The spatial distribution of the beginning day of ≥12 ℃ was significant different in different regions. During this study period, the early beginning dates of ≥12 ℃ expanded the scope of Jinghe and Manasi as cotton producing areas, and the late beginning dates of ≥12 ℃ narrowed to areas around Urumqi. With the advance of the beginning day of ≥12 ℃, the seeding date of cotton could start from 22nd to 28th April in most of the counties, and mulch cover could bring forward the suitable sowing date to 15th through 21st April.

Effects of future climate change on climatic suitability of rubber plantation in China.

LIU Shao-jun1,2, ZHOU Guang-sheng3, FANG Shi-bo3, ZHANG Jing-hong2

2015, 26(7):  2083-2090. 

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Global warming may seriously affect the climatic suitability distribution of rubber plantation in China. Five main climate factors affecting rubber planting were mean temperature of the coldest month, mean extremely minimum temperature, the number of monthly mean temperature ≥18 ℃, annual mean temperature and annual mean precipitation. Climatic suitability areas of rubber plantation in 1981-2010, 2041-2060, 2061-2080 were analyzed by the maximum entropy model based on the five main climate factors and the climate data of 1981-2010 and RCP4.5 scenario data. The results showed that under the background of the future climate change, the climatic suitability area of rubber plantation would have a trend of expansion to the north in 2041-2060, 2061-2080. The climatic suitability areas of rubber plantation in 2041-2060 and 2061-2080 increased more obviously than in 1981-2010. The suitable area and optimum area would increase, while the less suitable area would decrease. The climatic suitability might change in some areas, such as the total suitable area would decrease in Yunnan Province, and the suitability grade in both Jinghong and Mengna would change from optimum area to suitable area. However, the optimum area of rubber plantation would increase significantly in Hainan Island and Leizhou Peninsula of Guangdong Province, and a new less suitable area of rubber planting would appear in Taiwan Island due to the climate change.

Spatial and temporal characteristics of flue-cured tobacco water requirement and irrigation requirement index in Yunnan Province, China.

2015, 26(7):  2091-2098. 

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Based on the daily meteorological data of 124 agricultural meteorological sites during 1977-2010 in Yunnan Province, using recommended PenmanMonteith formula by FAO, water requirement and irrigation requirement index in the growth period of fluecured tobacco were calculated to analyze their spatial and temporal characteristics and change patterns. The results showed that water requirements of fluecured tobacco in root extending, vigorous, mature periods and field growth period during 1977-2010 were 76.73-174.73, 247.50-386.64, 180.28-258.14 and 528.18-764.08 mm, respectively, and the water requirement of vigorous period was the highest. The average irrigation demand index of each period was -0.02, 0.38, 0.17 and 0.26, respectively. Effective precipitation could meet the demand of fluecured tobacco in root extending period. Water requirement of fluecured tobacco in Yunnan Province decreased annually, and the rates of water requirement under the climate change trend in the four periods abovementioned were -12.42, -21.46, -7.17 and -47.15 mm·(10 a)^-1, respectively. The smallest irrigation demand index was observed in Dehong, and the largest in Diqing. The irrigation demand indexes of Dehong, Xishuangbanna and Puer regions were negative in fluecured tobacco field growth period. The reference crop evapotranspiration, water requirement and effective precipitation decreased, but the irrigation requirement and irrigation requirement index increased with the increase of latitude. The effective precipitation decreased, but the irrigation requirement and irrigation requirement index increased with the increase of altitude.

Prediction model of human-caused fire occurrence in the boreal forest of northern China.

GUO Fu-tao1, SU Zhang-wen1, WANG Guang-yu2, WANG Qiang3, SUN Long3, YANG Ting-ting1

2015, 26(7):  2099-2106. 

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The Chinese boreal forest is an important forest resource in China. However, it has been suffering serious disturbances of forest fires, which were caused equally by natural disasters (e.g., lightning) and human activities. The literature on humancaused fires indicates that climate, topography, vegetation, and human infrastructure are significant factors that impact the occurrence and spread of humancaused fires. But the studies on humancaused fires in the boreal forest of northern China are limited and less comprehensive. This paper applied the spatial analysis tools in ArcGIS 10.0 and Logistic regression model to investigate the driving factors of humancaused fires. Our data included the geographic coordinates of humancaused fires, climate factors during year 1974-2009, topographic information, and forest map. The results indicated that distance to railway (x₁) and average relative humidity (x₂) significantly impacted the occurrence of humancaused fire in the study area. The logistic model for predicting the fire occurrence probability was formulated as P=1/［1+e^{-(3.026-0.00011x1-0.047x₂)}］  with an accuracy rate of 80%. The above model was used to predict the monthly fire occurrence during the fire season of 2015 based on the HADCM2 future weather data. The prediction results showed that the high risk of humancaused fire occurrence concentrated in the months of April, May, June and August, while April and May had higher risk of fire occurrence than other months. According to the spatial distribution of possibility of fire occurrence, the high fire risk zones were mainly in the west and southwest of Tahe, where the major railways were located.

Prediction of total nitrogen and alkali hydrolysable nitrogen content in loess using hyperspectral data based on correlation analysis and partial least squares regression.

LIU Xiu-ying1,2, WANG Li1, CHANG Qing-rui1, WANG Xiao-xing1, SHANG Yan1

2015, 26(7):  2107-2114. 

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Wuqi County of Shaanxi Province, where  the vegetation recovering measures have been carried out for years, was taken as the study area. A total of 100 loess samples from 24 different profiles were collected. Total nitrogen (TN) and alkali hydrolysable nitrogen (AHN) contents of the soil samples were analyzed, and the soil samples were scanned in the visible/nearinfrared (VNIR) region of 350-2500 nm in the laboratory. The calibration models were developed between TN and AHN contents and VNIR values based on correlation analysis (CA) and partial least squares regression (PLS). Independent samples validated the calibration models. The results indicated that the optimum model for predicting TN of loess was established by using first derivative of reflectance. The best model for predicting AHN of loess was established by using normal derivative spectra. The optimum TN model could effectively predict TN in loess from 0 to 40 cm, but the optimum AHN model could only roughly predict AHN at the same depth. This study provided a good method for rapidly predicting TN of loess where vegetation recovering measures have been adopted, but prediction of AHN needs to be further studied.

Factors influencing soil moisture at different scales of the Lhasa River basin, China.

FU Guo-zhen1,2, BAI Wan-qi1, YAO Li-na3

2015, 26(7):  2115-2122. 

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The scale difference and role of factors influencing soil moisture regime are the basis of scale dependency study. This study, which selected farmland soils in the Lhasa River basin of the Tibetan Plateau as the research object, identified the main factors affecting the soil moisture using ecological redundancy analysis (RDA) and statistic analysis methods, based on data obtained by remote sensing technology and field surveys. The soil layers of 0-20, 20-40 and 40-60 cm were collected with the soildrilling method at each of 115 sampling sites distributed in the whole basin of the Lhasa River and 49 sampling sites in one of its subwatersheds. The results showed that soil moisture content in the Lhasa River basin, under the influence of climate and altitude, increased from southwest to northeast, and was higher in the lower soil layer than the upper layer due to water supplement by lateral seepage of the river. At subwatershed scale, farmland soil water content decreased with increasing the altitude and slope, and soil water storage capacity decreased with increasing the gravel content. The results were a significant support for the farmland expansion to higher altitude, adjustment of cropping structure, land consolidation, and construction of irrigation facilities in the region.

Near surface CO₂ concentration and its quantitative relationship with character of underlying surface in Shanghai City, China.

PAN Chen1,2, ZHU Xi-yang1,3, JIA Wen-xiao1,3, YANG Fang1,3, LIU Min1,3, XIANG Wei-ning1,3

2015, 26(7):  2123-2130. 

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Land use change and fossil fuel combustion due to urbanization have a significant effect on global carbon cycle and climate change. It’s important to have an explicit understanding of the spatial distribution of CO₂ to recognize and control GHG emission, which is helpful to reduce humaninduced contribution to global climate change. The study area of this project was set in the city of Shanghai with intensive human activity and rapid urbanization. The monitoring of near surface CO₂ concentration along 3 transects was conducted across an urbanrural gradient by means of near infrared gas analyzer Li840A in spring, 2014. Remote sensing data were also used to derive underlying surface information. Further quantitative analysis of the mechanism of CO₂ concentration’s response to the characteristics of underlying surface was presented in this paper. The results showed that the average near surface CO₂ concentration was (443.4±22.0) μmol·mol^-1. CO₂ concentration in city center was in average 12.5% (52.5 μmol·mol^-1) higher than that in the suburban area. Also, CO₂ concentration showed a significant spatial differentiation, with the highest CO₂ concentration in the northwest, the second highest in the southwest, and the lowest in the southeast, which was in accordance with the urbanization level of the underlying surface. The results revealed that the vegetation coverage rate (C_Veg) was an important indicator to describe near surface CO₂ concentration with a negative correlation, and the impervious surface area coverage rate (C_ISA) had lower explanatory power with a positive correlation. The study also found that the determination coefficient (R²) between CO₂ concentration (C_CO2) and C_ISA or C_Veg achieved its highest value when the buffer distance was 5 km, and their quantitative relationships be described by a stepwise regression equation: C_CO2=0.32C_ISA-0.89C_Veg+445.13 (R²=0.66, P<0.01).

Driving force analysis of land use change in the developed area based on Probit regression model: A case study of Nanjing City, China.

LIU Kang1, LI Yue-e2, WU Qun1, SHEN Jian-fen3

2015, 26(7):  2131-2138. 

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Based on the remote sensing image in 1996, 2002 and 2010, with the help of RS and GIS technology, and using the Probit regression model, this paper analyzed the characteristics of land use change in Nanjing City from 1996 to 2010, and the driving factors of land use change. The results showed that the cultivated land and woodland decreased, constructive land, garden plot and grassland continued to increase, and the comprehensive land use change rate was rising since 1996. The results of regression model for cultivated land and woodland change indicated that the change of cultivated land in the years 1996-2002 was mainly affected by the factors of “distance to the nearest rural settlement” and “farmers’ population density”. However, in the years 2002-2010 it was mainly affected by the factors of “change of per area GDP”, “distance to the rural settlement” and “distance to the nearest road”. The change of woodland in the years 1996-2002 was mainly affected by the factors of “the elevation” and “distance to the rural settlement”. However, in the years 2002-2010 it was mainly affected by the factors of “change of per area GDP”, “population density” and “distance to the nearest road”. By comparison, the early driving factors of land use change were mainly natural factors, but in recent years, they were mainly social, economic and demographic factors.

Application of stationary wavelet transformation to winter wheat SPAD hyperspectral monitoring.

YAO Fu-qi1,2, CAI Huan-jie2, SUN Jin-wei3, QIAO Wei1

2015, 26(7):  2139-2145. 

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By field trials, the canopy hyperspectral reflectance and chlorophyll content (SPAD) for winter wheat during 2010 and 2011 growth periods were measured by the ASD portable spectrometer and portable chlorophyll meter SPAD-502, respectively. The canopy spectral characteristics of different SPAD values were analyzed in different growth periods. The winter wheat SPAD estimation models based on normalized difference vegetation index (NDVI), ratio vegetation index (RVI) and wavelet energy coefficients were established in different growth periods. The results showed that green peak and red valley characteristics became more and more obvious with the increase of the SPAD. The SPAD estimation models based on NDVI performed better at the regreening stage, elongation stage, heading stage and filling stage with determination coefficients (R²) being 0.7957， 0.8096， 0.7557 and 0.5033, respectively. The winter wheat SPAD estimation models based on wavelet energy coefficients could greatly improve the SPAD estimation accuracy, with regression determination coefficients (R²) of the PVC estimation models based on high frequency energy coefficient and low frequency energy coefficient being 0.9168, 0.9154, 0.8802 and 0.9087 at the regreening stage, elongation stage, heading stage and filling stage, respectively.

 

Effects of Funneliformis mosseae on endogenous hormones and photosynthesis of Sorghum haipense under Cs stress.

HUANG Ren-hua1,2, YANG Hui-ling1,2, HUANG Wei1,2, LU Yun-mei2, CHEN Ke2

2015, 26(7):  2146-2150. 

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A pot experiment was conducted to analyze the effects of Funneliformis mosseae on endogenous hormones and photosynthesis in leaves of Sorghum haipense grown in soil contaminated with Cs. The results showed that Cs stress profoundly promoted abscisic acid (ABA) synthesis and decreased indoleacetic acid (IAA), gibberellin (GA), and zeatin riboside (ZR) contents in Sorghum haipense leaves, which led to significant increases in ABA/IAA and ABA/GA ratio. However, F. mosseae inoculation reduced the IAA, GA and ZR decreasing amplitudes and the ABA increasing range, which would maintain the ratio of ABA/IAA, ABA/ GA and ABA/（IAA+GA+ZR）. Radionuclide cesium pollution significantly reduced the photosynthetic rate (P_n), stomatal conductance (g_s), intercellular CO₂ concentration (C_i) and transpiration rate (T_r), which caused the plant photosynthetic efficiency to be lower than control. F. mosseae could alleviate the negative effect caused by cesium pollution on plant photosynthetic efficiency. It is suggested that to improve the efficiency of photosynthesis and anabolin, enhance plant tolerance and improve bioremediation efficiency, arbuscular mycorrhizal fungi (AMF) such as F. mosseae could be introduced into the field of phytoremediation in radionuclide contaminated soils.

Soil microbial community structure of two types of forests in the mid-subtropics of China.

HAN Shi-zhong1, GAO Ren1,2, LI Ai-ping1, MA Hong-liang1,2, YIN Yun-feng1,2, SI You-tao1,2, CHEN Shi-dong1,2, ZHENG Qun-rui3

2015, 26(7):  2151-2158. 

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Soil microbial community structures were analyzed by biomarker method of phospholipid fatty acid (PLFA) for a natural forest dominated by Castanopsis fabri (CF) and an adjacent plantation of Cunninghamia lanceolata (CL) in the midsubtropics of China. The results showed that the amounts of total PLFAs, bacterial PLFAs, fungal PLFAs, grampositive bacterial PLFAs and gramnegative bacterial PLFAs in the 0-10 cm soil layer were higher than in the 10-20 cm soil layer, and each type of PLFAs in CF were higher than in CL. In either soil layer of the two forest types, the contents of bacterial PLFAs were significantly higher than those of fungal PLFAs. In the two
forests, the contents of bacterial PLFAs accounted for 44%-52% of total PLFAs, while the contents of fungal PLFAs just accounted for 6%-8%, indicating the bacteria were dominant in the soils of the two vegetation types. Principal component analysis showed that the influence of vegetation types was greater than soil depth on the microbial community structures. Correlation analysis showed that gramnegative bacterial PLFAs, grampositive bacterial PLFAs and bacterial PLFAs were significantly negatively correlated with pH, positively with water content, and the PLFAs of main soil microorganism groups were significantly positively correlated with soil total nitrogen, organic carbon, C/N and ammonium.

Responses of soil microbial carbolic metabolism characteristics to home-field advantage of leaf litter decomposition in Liaoheyuan Nature Reserve of northern Hebei Province, China.

LI Tian-yu, KANG Feng-feng, HAN Hai-rong, GAO Jing, SONG Xiao-shuai, YU Shu

2015, 26(7):  2159-2166. 

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Using litter bag method, we studied the responses of soil microbial biomass carbon (MBC), microbial respiration (MR) and microbial metabolic quotient (q_CO2) in 0-5 cm, 5-10 cm and 10-20 cm soil layers to homefield advantage of Betula platyphlla and Quercus mongolica leaf litter decomposition in Liaoheyuan Nature Reserve, northern Hebei Province. The results showed that the contents of MBC in Betula platyphlla and Quercus mongolica leaf litter treatments in home environment (Bh and Qh treatments) were significant higher than that in B. platyphlla and Q. mongolica leaf litter treatments in nonhome environment (Ba and Qa treatments). There was no significant difference in MR between home and nonhome environments. Response degree of MBC and MR to homefield advantage of different litter decomposition was inconsistent. The MBC of the different soil layers in Qa treatment fell by 39.6%, 34.9% and 33.5% compared to Qh treatment, respectively, and that in B. platyphlla treatment was decreased by 31.6%, 27.1% and 17.0%, respectively. MR of the different soil layers in Qa treatment accounted for 96.3%, 92.4% and 83.7% of Qh treatment, respectively, while MR in B. platyphlla treatment was 99.4%, 97.3% and 101.3%, respectively. In contrast to MBC, qCO2 in soil showed a reverse pattern. Our study suggested that rich nutrients in soil enhanced microbial activity and weakened the conflict of nutrient uptake between plants and microorganisms, which led to the result that MBC and q_CO2 had an obvious response to homefield advantage of litter decomposition, when litter decomposed in its home environment. There was a weak response between MR and homefield advantage of litter decomposition, because of influence of soil temperature, water content and their interaction. Furthermore, MBC, MR and q_CO2 had a higher response degree to homefield advantage of Q. mongolica litter than B. platyphlla litter, since lower quality litter exhibited higher homefield advantage of litter decomposition.

Community structure of phytoplankton and its relationships with environmental factors in surface water of Ankang Reservoir, Northwest China.

YUAN Cong, TAO Shi-yu, ZHANG Ying-ying, GAO Jian-cao, YANG Yan-ping, WANG Zai-zhao

2015, 26(7):  2167-2176. 

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To evaluate trophic state and biotic community as well as the relationship between phytoplankton community composition and environmental factors in surface water of Ankang Reservoir, the water and phytoplankton were sampled monthly from January to December in 2012. The phytoplankton distribution and the physical and chemical indicators were analyzed. The characteristics of phytoplankton community were studied via Shannon diversity index (H) and Pielou evenness index (J). The trophic level was assessed via physical and chemical indicators, and trophic state index (TSI). One hundred and ten genera belonging to seven phyla were identified. The abundance of phytoplankton ranged from 0.11×10⁴ to 2.08×10⁴ cells·L^-1. The composition of phytoplankton and distribution of pollution indicator species, biodiversity and TSI indicated that surface water of Ankang Reservoir belonged to the ecological middling pollution type and was at a mesotrophic level. Highdensity feeding aquaculture and direct discharge of domestic wastewater had adverse effects on water quality. The water quality of Lanhe River, a tributary of Hanjiang River, was poor. Canonical correspondence analysis (CCA) showed that the impacts of the eight tested environmental factors on phytoplankton community composition and distribution varied in different seasons. Moreover, nitrogen was the main nutrient factor affecting the community composition of the phytoplankton. The physical and chemical indicators showed that the water quality of surface water of Ankang Reservoir was generally good and satisfied the standard of class Ⅱ water. However, the quality of total nitrogen poorer than the standard of class Ⅱ water in several sampling sites suggested that the water quality of Ankang Reservoir had the trend to be deteriorated.

Toxicity thresholds and predicted model of Pb added to soils with various properties and its leaching factors as determined by barley root-elongation test.

LI Ning1, GUO Xue-yan2, CHEN Shi-bao1, LIU Bin1, SONG Wen-en1

2015, 26(7):  2177-2182. 

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Ten field soils with various properties were added with Pb at 8 levels, and treated with or without leaching using simulated rain to test the Pb toxicity threshold (EC_10, EC₅₀) according to the ISO 11269-1 root elongation toxicity testing method. The leaching factors of Pb toxicity to barley root elongation were determined and the predicted models of Pb toxicity thresholds in soils with various properties were developed. The results indicated that the determined toxicity threshold (EC₁₀, EC₅₀) of Pb varied significantly (P<0.01) among the soils, and the EC₁₀ and EC₅₀ of Pb to barley in the soils ranged from 300-4130 mg·kg^-1 and 55-633 mg·kg^-1, respectively. The Pb toxicity decreased sharply after leaching treatment. The determined leaching factors (LF) ranged from
0.96-1.96 (LF_EC50) and 1.03-1.81 (LF_EC10) respectively, and the obvious effect was observed for the Pb toxicity decreasing in the soils with pH<6.81. The predicted models for Pb toxicity thresholds in soils were developed based on main soil properties (soil pH, organic carbon content and cation exchange capacity), and the determined Pb toxicity thresholds (EC_x,x=10,50) in soils fell in the range of mean values with ± 2 standard error (SD) prediction interval for the leached and unleached soils except for the red soil of Jiangxi Province, which indicated that the models based on the main soil properties could well predict the Pb toxicity in soils with various soil properties.

Multiple time scales analysis of spatial differentiation characteristics of non-point source nitrogen loss within watershed.

LIU Mei-bing1,2,3, CHEN Xing-wei2,3, CHEN Ying1,3

2015, 26(7):  2183-2191. 

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Identification of the critical source areas of non-point source pollution is an important means to control the non-point source pollution within the watershed. In order to further reveal the impact of multiple time scales on the spatial differentiation characteristics of non-point source nitrogen loss, a SWAT model of Shanmei Reservoir watershed was developed. Based on the simulation of total nitrogen (TN) loss intensity of all 38 subbasins, spatial distribution characteristics of nitrogen loss and critical source areas were analyzed at three time scales of yearly average, monthly average and rainstorms flood process, respectively. Furthermore, multiple linear correlation analysis was conducted to analyze the contribution of natural environment and anthropogenic disturbance on nitrogen loss. The results showed that there were significant spatial differences of TN loss in Shanmei Reservoir watershed at different time scales, and the spatial differentiation degree of nitrogen loss was in the order of monthly average > yearly average > rainstorms flood process. TN loss load mainly came from upland Taoxi subbasin, which was identified as the critical source area. At different time scales, land use types (such as farmland and forest) were always the dominant factor affecting the spatial distribution of nitrogen loss, while the effect of precipitation and runoff on the nitrogen loss was only taken in no fertilization month and several processes of storm flood at no fertilization date. This was mainly due to the significant spatial variation of land use and fertilization, as well as the low spatial variability of precipitation and runoff.

Research progress on ecological function of arbuscular mycorrhizal network.

WANG Qian1, WANG Qiang1, WANG Xiao-juan1,2, ZHANG Liang1, JIN Liang1,2

2015, 26(7):  2192-2202. 

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Arbuscular mycorrhizal (AM) fungi are one of the most important soil microorganisms in terrestrial ecosystems. Through hyphal fusion, the mycelium of AM fungi could form arbuscular mycorrhizal network (AMN) widely in the underground habitats. It has been demonstrated that AMN plays important roles in ecosystems. AMN could change the soil physical and chemical properties directly and change the microenvironment for soil microorganisms. Thus, AMN could influence the soil microbial community structure. AM fungi also could absorb nutrients through the external hyphae from soil. Then the nutrition could transport to different host plants through the mycelium with AMN, which could affect the dynamics of plant community structure. In order to discover the role of AMN in ecosystem, we reviewed the function of AMN in ecosystem, including: 1) the formation strategy of AMN through the external hyphae of AM fungi fusion in the soil; 2) the regulation of AMN on soil microorganism community structure and  ecological function; 3) the mechanism of AMN to adjust the soil  resources distribution, and their influence on intra and interspecific plant competition, as well as the host plant species diversity and abundance in ecosystem; 4) the relationship between AMN and global changes in the atmospheric nitrogen deposition, atmospheric CO₂ and temperature, and the role of AMN in the stability of ecosystem. The future development directions and application prospects were also discussed.

Research advances in the calculating method of nitrogen use efficiency (NUE) in cultivated lands.

YANG Xian-long1,2, TONG Yan-an1,2, LU Yong-li1,2, MA Hai-yang3

2015, 26(7):  2203-2212. 

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Nitrogen use efficiency (NUE) has received worldwide concern in the sphere of agronomic science and environmental science, and it is fundamentally important for evaluating N utilization status and optimizing N fertilization management in cultivated lands. In recent years, in consideration of low values and great variations of NUE in China’s cultivated lands, some scholars have discussed on the traditional concept and calculating method of NUE, and also have proposed some substituted NUE calculating methods. In this paper, we summarized some disadvantages of both conventional concept and calculating method of NUE, i.e. the subtraction method and the ^15N labeling method. Furthermore, we particularly introduced several substituted NUE calculation methods and discussed research directions in the future. In summary, we strongly suggested the establishment of a comprehensive evaluation index system of N utilization in good accordance with the current agricultural production status in China, based on a correct understanding of the dialectical relationships among N application rate, crop yield, N utilization and N loss.

Advances in copepod resting egg ecology in estuarine and coastal waters.

WANG Qing, LUAN Lei-lei, CHEN Liang-dong, YANG Yu-feng

2015, 26(7):  2213-2224. 

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Copepods are the key group in aquatic ecosystems, and play an important role in energy flow, the cycle of materials and information transfer. This paper summarized the distribution and composition of the copepods that spawn resting eggs in the estuarine and coastal marine areas. It also reviewed the survival time, hatching rates, abundance of resting eggs in the sediments, and the potential recruitment into the plankton population as correlated with environmental factors. The prospects of copepod resting egg ecology were also proposed in order to provide new ideas for future research.

A review on urban metabolism research based on physical space entities for environmental management.

LIU Ye1，2, LIU Dan3

2015, 26(7):  2225-2236. 

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Urban metabolism is a basic theory for coping with global environmental problems, which is coherent with the aims of national environmental management. This paper analyzed the concept of urban metabolism, and pointed out the meaning for urban metabolism in physical space entities; reviewed the current methods for urban metabolism and its merits and shortages; analyzed the system boundaries, connotation, and methodologies; and summarized the advances on urban metabolism practices in physical space entities. At last, we made conclusions that there were shortages, including conception system, basic theory system, and interdisciplinary integrated theory system in current urban metabolism research, and the current cases studied in urban metabolism were limited and not suitable to the harmony development between society, economy, and environment. In the future, we need to strengthen comparison between different case studies from different countries, develop the prior modes of typical urban metabolism research, identify the mechanism for urban ecosystem, and strengthen the spatial decision support system of environmental management taking urban spatial entity spaces as units.