中国生态农业学报(中英文)

Participatory evaluation of rural historic landscape based on the 3D e-Sandbox:A case study in Duimenshan Village in Guizhou Province

ZHANG Xiaotong, DUAN Jinming, YU Linjun, LU Yongfei, WANG Xiaojun

2017, 25(10): 1403-1412. doi: 10.13930/j.cnki.cjea.170128

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Abstract:
Understanding the trend in historical rural landscape evolution could support decision-making and governance for sustainable rural development. Local villagers are the necessary source of knowledge on the changes in historical rural landscape, they can play an extremely important role in the restoration of rural landscapes. However, the platform for intuitively and interactively supporting various stakeholders in participating in the restoration of historical rural landscapes is still short. The objective of this study was to excavate the landscape memory and local knowledge, and then to restore and evaluate the rural historical landscape changes using more acceptable way for local villagers. This paper took Duimengshan Village, Zhenfeng County of Guizhou Province as the case study. The landscapes were analyzed in four historical periods (1958, 1980, 1995 and 2015) for restoration using the 3D e-Sandbox tool and participatory rural appraisal. The results showed that local villagers could easily participate in landscape restoration processes using the 3D e-Sandbox tool. Although the land was divided into households from 1980, the production and lifestyle of the villagers had no structural changes due to the local conditions, leading to insignificantly landscape changes. However, the proportion of paddy fields in Duimenshan Village decreased rapidly since the introduction of large-scale tobacco cultivation in 1995. This also directly led to the ecological services value decreased significantly as the paddy field (a type of wetland) as an important contributor to the value of ecological services. Moreover, because of the rapidly increase and uniform distribution of public service facilities in the past 20 years, the landscape diversity had increased significantly. It was concluded that the 3D e-Sandbox could solve technical problems in participatory rural historic landscape restoration like the poor communications between planner and local people.

Energy balance and closure of typical winter wheat farmland ecosystem in the North China Plain

WU Dongxing, LI Guodong, ZHANG Xi

2017, 25(10): 1413-1422. doi: 10.13930/j.cnki.cjea.170150

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Abstract:
The accurate quantification of energy and mass exchange between terrestrial ecosystem and the atmosphere is important for water resources management and sustainable agricultural development. Energy balance closure is also a vital index for assessing the accuracy of measurements data and analyzing surface energy balance. In order to evaluate energy balance and energy closure in farmland ecosystems, the open eddy covariance system and total factor automatic weather station were used to observe continuous surface energy flux and conventional meteorological elements of typical winter wheat in farmland ecosystems in the North China Plain for the period 2013-2014. In the study, four typical growth stages (seeding, overwintering, jointing and grain-filling stages) were investigated for diurnal and annual variations in energy flux of winter wheat. Also the diurnal variations in Bowen ratio for four typical growth stages were calculated. The results showed that the trends in diurnal variations in net radiation and energy component of the four growing stages of winter wheat were unimodal in shape. The peak values of net radiation, sensible heat flux and latent heat flux were observed between 12:00 and 13:00. The maximum value of sensible heat flux was at 11:30 and the peak value of soil heat flux occurred between 14:00 and 15:00; which was about 1.00 hour later than sensible heat flux and latent heat flux. For annual variation, the trends in net radiation and latent heat flux were strongly consistent. The minimum values of net radiation and latent heat flux at overwintering stage were 114.51 W·m^-2 and 13.47 W·m^-2, respectively. However, sensible heat flux at overwintering stage was relatively higher than latent heat flux. Sensible heat flux and soil heat flux were respectively 33.61 W·m^-2 and 13.05 W·m^-2. The maximum values of net radiation and latent heat flux were observed at grain-filling stage, with respective values of 327.02 W·m^-2 and 116.56 W·m^-2. After winter wheat harvest, sensible heat flux increased rapidly, while latent heat flux rapidly decreased. Energy closures of representative observation dates selected for the four growing stages were also good. The energy closure ratios were 0.49, 0.77, 0.81 and 0.76, respectively. The energy closure ratio was high in summer and relatively low in winter. Diurnal variations in Bowen ratio during the four growing stages had an inverted U-type curve. While Bowen ratio values for daytime were relatively stable, those for nighttime were negative and relatively unstable. The Bowen ratio curves agreed well with sensible heat flux curve. Bowen ratio was positive when sensible heat flux was positive and it increased with sensible heat flux. The maximum value of Bowen ratio at seeding stage (2.12) occurred at 14:00, while the maximum values of Bowen ratio at overwintering (1.48), jointing (0.31) and grain-filling stages (0.58) all occurred at 10:00. The results of the study set the basis for research on heat and water vapor fluxes in farmland ecosystems in the North China Plain.

Ecological characteristics of cultivated Haloxylon ammodendron communities in Gurbantunggut Desert

DING Gaigai, JIANG Jin, SONG Chunwu, LI Shengyu, WANG Haifeng, ZHOU Jie, LI Yaping

2017, 25(10): 1423-1432. doi: 10.13930/j.cnki.cjea.170111

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Abstract:
The ecological characteristics of Haloxylon ammodendron communities cultivated under rainfed conditions for 33 years in Mosuowan of Southern Gurbantunggut Desert were analyzed under two afforestation techniques-snow-sand dressing afforestation and autumn-irrigated afforestation. The growth potential, understory vegetation and soil water content were monitored and recorded. Results showed that:1) H. ammodendron had strong growth with an average plant height and canopy spread under both cultivation techniques exceeding 2 m and 2 m², respectively. The average length of new branches was more than 20 cm, with a survival rate of afforestation of 40% under snow-sand dressing and 63% under autumn irrigation. The den-sity was enhanced and uneven-aged mixed forest was formed due to natural regeneration. There were different kinds of dominant species herbs in the forest. The average soil water content under the two forest treatments both exceeded 2.00%, which was enough to support H. ammodendron growth. 2) There were obvious differences between the two forests cultivation techniques in terms of vegetation cover and species diversity and natural regeneration of H. ammodendron due to the differences in the treatments, site conditions and initial water supply. 3) The two communities were highly adaptable to the local ecological conditions. Compared with autumn irrigated afforestation, the density, vegetation cover and number of natural regeneration were lower in snow-sand dressing afforestation. The cost also was lower, but grew slowly under autumn irrigated afforestation after irrigated was stopped. There was the need for effective artificial measures to reduce the density of H. ammodendron. In conclusion, H. ammodendron growth under snow-sand dressing and autumn irrigated afforestation was both stable with the latter well-adapted to the local ecological conditions.

Effect of exogenous phosphorus input on the availability and turnover characteristics of soil carbon pool in agro-riparian wetlands

SUN Xingzhao, SHEN Jianguo, WANG Zhong, LIU Meng, LOU Liping, YUE Chunlei, ZHANG Zhijian

2017, 25(10): 1433-1443. doi: 10.13930/j.cnki.cjea.170266

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Abstract:
Exogenous nutrients significantly influence wetland ecosystems.In particular, the invasion of exogenous nitrogen (N) and phosphorus (P) significantly influences carbon cycle in wetland soils which further changes global carbon cycle in soil-atmosphere continuum.While there are currently several studies on exogenous N, the study of exogenous P is still lacking.To explore the effect of the input of exogenous P on the availability and turnover characteristics of soil carbon pool in wetlands, an experiment was designed for the simulation of the dynamics of exogenous P accumulation.The study simulated additive P gradient rates of 0(P-0), 5% (P-5), 10%(P-10), 20%(P-20), 30%(P-30) and 60%(P-60) relative to initial total phosphorus (TP) content of sampled soils.Superphosphate was the mode of addition of P to the soil coupled with the simulation of laboratory data.The changes in characteristics of soil carbon composition and biochemical indicators of P with the input of different levels of exogenous P were analyzed using conventional biochemical testing methods.The study also integrated several other factors for Pearson correlation analysis.The results showed that soil TP and Olsen-P contents strictly followed the loading rates of superphosphate, with a notable increase in microbial biomass phosphorus (MBP).The activity of acid phosphatase (AcP) was significantly suppressed by P addition.Dissolved organic carbon (DOC) and microbial biomass carbon (MBC) increased with increasing inputs of exogenous P, while total organic carbon (TOC) decreased at a maximum rate of 23%.For active organic carbon components of the soil, highly labile organic carbon (HLOC) was 54% higher under P-60 treatment than under the control group (P-0).Then recalcitrant organic carbon (ROC) content remarkably decreased with increasing input of exogenous P, with a maximum rate of decline of 22%.To certain extent, the results indicated that soil carbon pool was activated and the efficiency of availability increased.However, mid-labile organic carbon (MLOC) and labile organic carbon (LOC) almost had no change with increasing input of exogenous P.The MLOC and LOC ingredients were stable in the soil.The activities of β-1, 4-glucosidase (βG) and cellobiohydrolase (CBH) significantly increased with increasing levels of exogenous P, but the activity of dehydrogenase (DH) remained largely unchanged.For the analysis of mineralization characteristics of soil organic carbon (SOC), exogenous P addition significantly accelerated SOC mineralization rate.The cumulative mineralization increased with increasing addition of exogenous P.Potential mineralization potential of SOC was positively correlated with the addition of exogenous P.From the above, exogenous P input increased the consumption of soil carbon pool and transformed soil carbon pool from steady state to unstable state.It also increased the activity and content of biological enzyme by stimulating microbial activity.In summary, the availability and turnover rates of wetland soil carbon pool and the risk of wetland soil carbon output significantly increased under exogenous P input.

Isolation, identification and activity of ammonifiers, nitrosobacteria and microbial characteristics in tobacco-planted soils

ING Mengjiao, HUANG Ying, LI Chunshun, BIN Jun, LI Qiang, FAN Wei, ZHANG Yi, ZHOU Jiheng

2017, 25(10): 1444-1455. doi: 10.13930/j.cnki.cjea.170169

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Abstract:
The rate of organic nitrogen decomposition could be not controlled after organic fertilizer application in tobacco-planted soils. This problem could affect the normal growth and quality of tobacco leaves. In this study, chemical fertilizer, cow manure, maize straw and rapeseed cake were applied to the root-zone soil under tobacco. The study attempted to isolate highly active local ammonifiers and nitrosobacteria, and to determine the effects of the two bacteria types on the decomposition of organic nitrogen and ammonia. The study was to make possible the preparation of a microbial agent for the efficient decomposition of organic nitrogen. The results showed that the numbers of bacteria, fungi, actinomycetes and ammonifiers treated with organic fertilizer were higher than those treated with chemical fertilizer during the vigorous growth period of flue-cured tobacco. The numbers of ammonifiers, nitrosobacteria, fungi and actinomycetes treated with organic fertilizer were higher than those treated with chemical fertilizer in flue-cured tobacco at maturity period. Through analysis of soil samples of various strains, the dominant strains with high ammoniation intensity were all derived from soil samples treated with organic fertilizer. It was shown that soils treated with organic fertilizer had higher active ammonifiers than soils treated only with chemical fertilizer. The results showed that decline in organic nitrogen content was highest in Bacillus pumilus, Geobacillus stearothermophilus and B. megaterium, which was 84.74%, 92.74% and 79.52% lower than that of initial organic nitrogen. Stenotrophomonas sp. had the highest nitrosation and nitrification activity. After 7 days of culturing, nitrate nitrogen content in cultured medium was 0.617 mg·L^-1. S. maltophilia had the strongest nitrosation activity. After 7 days of culturing, nitrite content in the cultured medium was 0.518 mg·L^-1. Organic nitrogen decomposition activity of ammoniated bacteria decreased after 48 h of culturing. Then the nitrification and nitrification activities were still high 7 days after culturing. Thus the separation of different functions of bacteria in the preparation of nitrogen-containing composite microbial agents should be done at different times by adding fermentation strain to achieve high activity of microbial agents. In this study, eight strains (Naxibacter sp., Stenotrophomonas sp., B. pumilus, G. stearothermophilus, B. stratosphericus, Cellulosimicrobium cellulans, B. altitudinis and B. megaterium) were identified as high-efficiency strains of microbial agents for the decomposition of soil organic nitrogen.

Effects of Bemisia tabaci feeding on nutrients and resistance-related compounds of pepper varieties with different insect resistances

LI Chuanming, HE Jing, GU Ai'xiang, SU Honghua, WU Xiaoxia, ZHANG Haibo, XIE Yamei, WU Yahong, ZHOU Fucai

2017, 25(10): 1456-1462. doi: 10.13930/j.cnki.cjea.170372

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Induced insect resistance is a series of defending reactions of plant under biotic and abiotic stress. In order to explore the effects of Bemisia tabaci feeding on induced insect resistance of different varieties of pepper, and illuminate the insect resistance mechanisms, we conducted an experiment in insectary. In the experiment, two insect-resistant varieties ('Xinyidai Sanying' and 'Xinsujiao 5') and two insect-susceptible varieties ('Sujiao 13' and 'Sujiao 15') of pepper were selected and infected with B. tabaci adults 0 (control), 30 (lower density), 60 (middle density) and 120 (higher density) heads per plant, respectively. The contents of chlorophyll, soluble sugar, soluble protein, phenol compound and flavonoids in pepper leaves were determined after 24 h of feeding of B. tabaci. The results showed that leaf chlorophyll content of pepper under feeding of lower density of B. tabaci was significantly increased, and the chlorophyll content decreased with the increase of population density of the insect, but was still higher than that of the control. The increase of chlorophyll content in the insect-susceptible pepper varieties was higher than that of the insect-resistant varieties. The content of soluble sugar in pepper leaves showed a decreasing trend after infected with the insects with lower and higher densities, and the decreased level of insect-resistant varieties was higher than that of insect-susceptible varieties. The content of soluble protein in pepper leaves decreased after infected by the insects with lower and middle densities, but increased when fed by high density insects. The changing range of soluble protein contents of insect-resistant pepper varieties was higher than that of insect-susceptible varieties. The contents of phonemic compounds in leaves increased significantly after B. tabaci feeding, and the increase rate of insect-susceptible varieties was higher than that of the insect-resistant cultivars. With the increased insect density, the content of phenolic compounds in pepper leaves showed a significant upward trend, but decreased obviously when the population density was 120 head per plant. We also found that the content of flavonoids in the leaves of pepper 'Sujiao 15' was significantly increased after B. tabaci feeding, and that in other varieties under middle insect density were not significantly different from that of the control. However, in the case of higher insect density, the content of flavonoids was significantly higher than that of control. Our results indicated that the feeding of B. tabaci changed contents of nutrients and resistant substances in the direction of improving insect resistance. The extents of change of different pepper varieties under different insect densities were different. The results provided a basis for further revealing the defense and anti-defense mechanisms between hos plant and B. tabaci.

Effects of nitrogen application rate on soil microbial quantity and soil enzymes activities in maize/soybean intercropping systems

FU Zhidan, ZHOU Li, CHEN Ping, DU Qing, PANG Ting, YANG Wenyu, YONG Taiwen

2017, 25(10): 1463-1474. doi: 10.13930/j.cnki.cjea.170335

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Abstract:
To study the effects of nitrogen rate on soil microbial quantity and enzyme activity in maize/soybean intercropping system, a 2-factor design was developed. The main factor in the design was planting pattern, which included monoculture maize (MM), sole soybean (SS) and maize/soybean relay strip intercropping system (IMS). Then the sub-factor of nitrogen application rate N for maize and soybean were no nitrogen application[0 kg(N)·hm^-2, NN], reduced nitrogen application[180 kg(N)·hm^-2, RN], and conventional nitrogen application[240 kg(N)·hm^-2, CN]. The results showed that the quantities of fungi and actinomycetes in rhizosphere soil of intercropped maize were 25.37% and 8.79% higher than those of monoculture maize, respectively. Also the quantities of soil fungi, actinomycetes and nitrogen-fixing bacteria in the rhizosphere soil of intercropped soybean were higher than those of sole soybean. Soil protease and urease activities in the rhizosphere soil of intercropped maize and protease activity in rhizosphere soil of intercropped soybean significantly increased compared with the corresponding monoculture. Under different nitrogen application rates, the quantities of soil fungi, actinomycetes and nitrogen-fixing bacteria in the rhizosphere of maize and soybean were higher under RN than under NN and CN, respectively. In addition, nitrogen application increased the quantity of actinomycetes in the rhizosphere soil of maize and soybean. The quantities of nitrogen-fixing bacteria in the rhizosphere soil of maize were 17.78% and 5.67% higher under RN compared with those under NN and CN, respectively. Moreover, the activities of soil protease and urease in the rhizosphere of maize and activity of soil urease in the rhizosphere of soybean were highest under RN compared with those under NN and CN. Reduced nitrogen fertilization increased the degree of soil microbial and enzyme activities in the rhizosphere of maize/soybean relay strip intercropping system, promoted nitrogen uptake of maize and soybean, and thereby saved fertilizer use.

Effect of water deficit on mineral element absorption, distribution and water utilization by different wheat varieties

LI Dongxiao, WANG Hongguang, ZHANG Di, ZHAO Guoying, LI Haoran, JIA Bin, LI Yanming, LI Ruiqi

2017, 25(10): 1475-1484. doi: 10.13930/j.cnki.cjea.170272

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Abstract:
In the context of limiting the area of wheat irrigation, it is necessary for promoting resources use efficiencies, increasing yield and improving quality of wheat to explore nutrients absorption and utilization, and water use efficiency of wheat under water deficit condition. Pot experiments were conducted in phytotrons with three wheat varieties under two water conditions (normal and drought). The three wheat varieties included 'Cangmai-6001' (drought resistant), 'Hanmai-9' (wet and high yield) and 'Jimai-22' (multi-resistance and super high yield). The content, accumulation and distribution of mineral elements in different organs of the plants were measured. Also the relationship between these indexes with water use efficiency and yield analyzed. The results showed that the contents and accumulation of mineral elements were specific to different plant organs. The highest content and distribution ratio of Ca were observed in leaf, those of Cu and Zn were in grain, Na was in stem. Fe accumulated in different organs of the plant was influenced by water and plant variety. Under normal water condition, the highest Fe content and distribution ratio were in the stem of 'Cangmai-6001', which was the same for the leaf for 'Hanmai-9'. The Fe content in stem and glume and Fe distribution ratio in leaf and glume were higher than in other organs of 'Jimai-22'. Under water deficit condition, Fe content was highest in grain for 'Cangmai-6001'and 'Hanmai-9', but it was highest in leaf for 'Jimai-22'. For all the investigated varieties, the highest Fe distribution was in grain. Water deficit increased with the distribution of Cu and Zn, accumulation of Zn, Na and Ca in grain, water use efficiency and yield for 'Cangmai-6001', and with WUE_yield for 'Jimai-22'. However, water deficit decreased with the accumulation of Mn in the grain of 'Cangmai-6001', Cu and Mn in grain of 'Hanmai-9', Cu and Fe accumulation in 'Jimai-22' grain, water use efficiency, yield and dry matter weight of 'Hanmai-9'. Above all, 'Cangmai-6001' was more beneficial in terms of yield increase with higher WUE, higher Fe accumulation in grain and supplemented Mn element under water deficit condition. 'Jimai-22' had stable yield with increasing WUE and supplemented Fe element in grain under water deficit condition. For 'Hanmai-9' variety, the yield, WUE, Cu and Mn accumulation in grain decreased obviously under water deficit condition. Correlation analysis indicated that Cu, Zn, Ca and Mn had significant interaction with dry matter, with no direct effect on yield and WUE. This was related with the differences in variety and interaction effects of variety and water. There was still the tendency for mineral elements to regulate water utilization by influencing wheat dry matter formation, which needed further research and verification.

Effect of nitrogen management and cultivation method on grain-filling characteristics and grain yield of indica hybrid rice

YAN Tianrong, LI Xuyi, LI Na, JIANG Mingjin, YANG Zhiyuan, HE Yan, WANG Chunyu, WANG Haiyue, MA Jun

2017, 25(10): 1485-1494. doi: 10.13930/j.cnki.cjea.170337

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Abstract:
The effects of nitrogen management[ratios of transplant-tiller to panicle of N-fertilizer were 9:1 (N₁), 7:3 (N₂) and 5:5 (N₃)] and cultivation method (C₁, wide and narrow row cultivation; C₂, triangular cultivation; C₃, wide row and narrow space cultivation; and C₄, seedling-throwing cultivation) on sink potential, grain-filling properties and grain yield were studied in two widely variable ecological conditions (Wenjiang and Hanyuan in Sichuan Province) using indica hybrid rice 'Ⅱ-you-498'. The aim of the study was to clarify the correlation among ecological conditions, nitrogen management and cultivation method with grain-filling properties and grain yield formation. The results were as follows:1) Grain sink potential, grain plumpness, seed setting rate and 1000-grain weight in Hanyuan were better than those in Wenjiang. Furthermore, it was easy to have high yield with low initial growth vigor due to delayed date for peak grain-filling rate, high grain-filling rate and long grain-filling duration at early and middle stages and long active grain-filling period in Hanyuan. 2) With increasing nitrogen application ratio at the late stage, the maximum sink potential decreased while grain-filling indexes, seed setting rate and 1000-grain weight increased. The initial growth vigor reduced at grain-filling, and the maximum and mean grain-filling rates (G_max and G_mean) increased. Also, the time to reach peak grain-filling delayed with higher proportion of growth while the duration of grain-filling shortened. The highest yield was under N₂. 3) There were little differences in seed-setting rate and 1000-grain weight but significant differences in biomass yield, sink potential and grain-filling characteristics among different cultivation methods. For the highest yield performance under different cultivation methods, there were similar grain-filling characteristics, such as larger sink potential, lower initial growth vigor at grain-filling, delayed time to reach maximum grain-filling and higher G_max and G_mean. The wide and narrow row cultivation, triangule cultivation, wide row and narrow space cultivation and seedling-throwing cultivation had the highest yield when the ratio of transplant-tiller and panicle N-fertilizer was 9:1, 9:1, 7:3 and 5:5, respectively. Triangular cultivation had the highest yield among the four cultivation methods. 4) Correlation analysis showed that with increasing maximum sink potential, initial growth vigor at grain-filling and delayed time to reach maximum grain-filling rate decrease. The high grain yield obtained was attributed to increasing duration of grain-filling, grain-filling rate and growth increment, especially in the early and middle stages. Thus any further improvement in rice yield depended on local ecological conditions and cultivation methods, combined with optimized nitrogen management.

Effects of combined biochemical inhibitors and fertilization models on nutrient uptake and use efficiency of rice in yellow clayey field

ZHOU Xuan, WU Lianghuan, DAI Feng

2017, 25(10): 1495-1507. doi: 10.13930/j.cnki.cjea.170292

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Abstract:
Application of biochemical inhibitors for urease and nitrification is an effective way of improving fertilizer use efficiency of rice. The objective of this study was to determine the characteristics of nutrient use of rice as affected by biochemical inhibitors and fertilization models, and find the optimal yield and efficient application method in rice growing region in yellow clayey soils. It analyzed the interaction effects of biochemical inhibitors[urease inhibitors N-(n-butyl) thiophosphoric triamide (NBPT] and N-(n-propyl) thiophosphoric triamide (NPPT), and nitrification inhibitor 2-chloro-6-(trichloromethyl) pyridine (CP)] with fertilization models (one-off and three-time fertilizations) on nutrient absorption, utilization and distribution of rice, and the relationship between nutrient uptake and grain yield using two factor randomized block design. Results showed that certain interaction effects was observed between inhibitor combination and fertilization model on the uptake, utilization and distribution of nitrogen (N), phosphorus (P) and potassium (K) at the main growth periods of rice. The three times urea fertilization treatment significantly increased N, P and K uptake (respectively by 11.0%, 0.9% and 4.2%) at maturity, and N recovery efficiency and N agronomic efficiency (respectively by 27.5% and 70.8%) over those of one-off urea fertilization treatment. The addition of inhibitors (NBPT, NPPT/+CP) significantly increased N, P and K uptakes of rice, dry matter production and N accumulation after heading stage. It also improved the allocation of nutrients in grain and N use efficiency under different fertilization models. The application of new urease inhibitor NPPT alone or combined with CP had the similar effect on nutrient uptake and use in paddy fields with NBPT. The uptake of N, P and K of rice at maturity had significant positive correlation with grain yield under different fertilization models. In conclusion, the integration and optimization of fertilization techniques combined with inhibitors enhanced the uptake and transport of N, P and K after heading stage. It also promoted nutrient accumulation and at the same time significantly improved rice yield and nutrient use efficiency in yellow clayey fields.

Spatio-temporal variation in reference evapotranspiration in recent 50 years in karst and non-karst areas in Guangxi Zhuang Autonomous Region

WU Liping, CHEN Hongsong, LIAN Jinjiao, FU Zhiyong, WANG Sheng

2017, 25(10): 1508-1517. doi: 10.13930/j.cnki.cjea.170293

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Reference evapotranspiration (ET₀) is the water requirement of plants driven by meteorological factors. It is critical for restoration of vegetation and regional water resources management. In Southwest China where karst landforms are common, the ecological environment is fragile. Extreme drought and flood events are usually caused by declining annual precipitation and large amounts of precipitation within short time periods. The response of ET₀ to global climate change is a key in the assessment of the effect of climate change on hydrology. Therefore, it was important to explore the spatial and temporal variations and the related driving factors of ET₀. Based on data collected from 25 meteorological stations in Guangxi for the 1960-2010, daily ET₀ was computed using the FAO-56 Penman-Monteith equation. The spatio-temporal variations and the driving factors of ET₀ in Guangxi karst and non-karst areas were analyzed separately using Kriging interpolations, cumulative anomalies and spearman rank correlation at seasonal and annual scales. The driving factors of ET₀ in karst and non-karst areas were analyzed using the path-analysis method. Results showed that ET₀ decreased gradually from southeast to northwest of the study area, with an average rate of 1 138 mm·a^-1 during the studied period. High ET₀ was mainly distributed in non-karst areas and low ET₀ in karst areas. For different seasons, ET₀ values from stations in non-karst areas were generally higher than those from stations in karst areas. Mean monthly ET₀ in both karst areas and non-karst areas tracked a unimodal curve, with relatively high ET₀ for the period from May to September. Non-karst areas had higher ET₀ variations than karst areas. The average monthly ET₀ in non-karst areas was 95 mm and that in karst areas 64 mm. Summer ET₀ was highest and winter ET₀ lowest. In the recent 51 years, annual ET₀ for both karst and non-karst areas tracked N-shaped distribution, and were the highest in the 1970s and lowest in the 1990s with an increasing trend for period 2002-2010. The trends of variation in annual ET₀ in Guangxi were also analyzed. Out of the 25 stations, 3 stations in karst and 4 stations in non-karst areas had significant decrease in trend; then 2 stations in karst and 1 station in non-karst areas showed significant increase in trend, and the other stations had no significant trends. Analysis of the relationship between ET₀ and meteorological factors showed that sunshine duration, wind speed and average temperature were the main meteorological factors driving ET₀ in non-karst areas. Relative humidity influenced annual ET₀ by interacting with other meteorological factors in karst areas. Seasonally, sunshine duration and average temperature had the highest impact on ET₀, and both were positively related with ET₀. Furthermore, the indirect effect of the coefficient between wind speed and ET₀ was negative for karst areas and positive for non-karst areas in winter and spring. Differences in geographical location and topography were the main reasons for the differences in ET₀ between karst and non-karst areas. Therefore, understanding the trend of change and the reasons for the change in ET₀ in different regions was a necessary measure for analysis of ecological water requirement.

Overexpression of Suaeda salsa SsNHX1 gene enhanced salt and drought tolerance of transgenic tobacco

CHEN Xin, MA Chao, YANG Yongjuan, WANG Hongling, HUANG Ying, ZHANG Xiaoxia, HUANG Kaifeng, ZHAO Zhuo, ZHANG Suzhi

2017, 25(10): 1518-1526. doi: 10.13930/j.cnki.cjea.170230

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Tobacco (Nicotiana tobacum L.) is an important economic and model plant. Salt and drought are two important environmental factors that are harmful to plant growth, development, production and quality of tobacco. In addition to conventional salt and drought prevention measures, genetic engineering of plants has also been proven to be effective. In order to improve salt and drought tolerance of tobacco, Na⁺/H⁺ anti-porter gene SsNHX1 was cloned from Suaeda salsa salt-tolerant plant and overexpressed in tobacco by agrobacterium-mediated genetic transformation. The differences in salt tolerance and drought resistance were compared by determining phenotypic and physiological indexes of wild and transgenic tobacco L1 and L5. Phenotypic analysis showed that salt tolerance of SsNHX1 transgenic tobacco lines L1 and L5 were significantly higher than that of the wild type. This was evident from the vigorously growth and uninhibited root elongation under salt stress condition. The overexpressed transgenic lines of tobacco accumulated more Na⁺ and K⁺ in the both leaves and roots and with faster rate of increase of Na⁺ and slower decreasing rate of K⁺. The lines also maintained significantly higher contents of relative leaf water and chlorophyll, but lower malondialdehyde contents and relative conductivities. The results indicated that overexpression of SsNHX1 gene apparently promoted compartmentalization of Na⁺ from vacuolar cells into vacuoles and improved salt tolerance of transgenic plants of tobacco. On the other hand, SsNHX1 transgenic tobacco plants showed significant enhancement of drought tolerance than the wild type and restored normal growth after rehydration. Under drought stress, the contents of malondialdehyde and relative conductivities of transgenic lines were lower than those of the wild type, while the relative water and chlorophyll contents of leaves were maintained. The results suggested that under drought stress, overexpressed SsNHX1 in tobacco reduced damage to cell membrane by reducing osmotic potential of cells, maintaining relative water and chlorophyll content of leaves, and finally improved drought resistance of tobacco.

Environmental impact assessment via life cycle analysis for organic and conventional apple productions

CAI Yujie, QIAO Yuhui, XU Jing, MENG Fanqiao, WU Wenliang

2017, 25(10): 1527-1534. doi: 10.13930/j.cnki.cjea.170131

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Abstract:
To set the scientific basis for sustainable agricultural development and ecological civilization construction in China, this study analyzed the impacts of organic and conventional apple productions on environment in Fushan of Shanxi Province, Baishui of Shaanxi Province and Tianshui of Gansu Province through life cycle analysis method. Data were collected via field visits and farmer interviews. The study used unit apple production as the basis for comparative analysis. The system boundary of apple production defined in the study included materials production and cropping stages. The impacts of apple production on environments were assessed at four aspects-energy consumption, global warming, environmental acidification and eutrophication. It was found that nutrient use efficiency in organic apple production in Fushan of Shanxi Province was higher than that in conventional apple production, which was the reverse of the results for Baishui of Shaanxi Province and Tianshui of Gansu Province. The yield of organic apple was similar to that of conventional apple in Baishui of Shaanxi Province and Tianshui of Gansu Province, while the yield of organic apple in Fushan of Shanxi Province was only 69% that of conventional apple. Nitrogen, phosphorous and potassium inputs in organic apple production in Fushan of Shanxi Province were 6.8%-18.8% those of conventional apple production. For the other two regions, however, nutrient input in organic production was about 72.7%-228.8% that of conventional production. Energy consumption per unit organic apple product in the three regions accounted for less than 26% of the conventional product; i.e., energy utilization efficiency of organic apple was higher than that of conventional apple. Among the four environmental impacts (energy consumption, global warming, environmental acidification and eutrophication), eutrophication contributed the most (over 80%) to total environmental impact. The impact of global warming for unit organic apple product in Fushan of Shanxi Province was smaller than that of conventional product (organic product was only 23% that of conventional product). However, organic apple production in Baishui of Shaanxi Province and Tianshui of Gansu Province was much higher than that of conventional production (organic apple was respectively 356% and 138% conventional apple for the two areas). Environmental acidification and eutrophication under organic apple production in Fushan of Shanxi Province was lower than that under conventional production, but the results for Tianshui of Gansu Province and Baishui of Shaanxi Province were the reverse. Total environmental impact of apple production was the highest in Baisui of Shaanxi Province, followed by Tianshui of Gansu Province and then Fushan of Shanxi Province. Total environmental impact of organic apple production was 22% that of conventional apple production in Fushan of Shanxi Province. Then in Baishui of Shaanxi Province and Tianshui of Gansu Province, total environmental impacts of organic apple production were respectively 356% and 138% those of conventional apple production. This discrepancy was mainly due to differences in the amount and types of fertilizer used. The results showed that organic production had crop yields comparable to those of conventional agriculture in terms of nutrient input. However, it also led to higher negative environmental impacts and lower nutrient and energy use efficiency in organic production.

Assessment of Cd, Pb, Hg and As contamination in soils and plants in Isatis indigotica cultivated regions in Hebei Province

GENG Liping, GAO Ningda, ZHAO Quanli, XUE Peiying, LIU Wenju

2017, 25(10): 1535-1544. doi: 10.13930/j.cnki.cjea.170379

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Abstract:
Concentrations of Cd, Pb, Hg and As in soils and plants in Isatis indigotica cultivated regions of Anguo City and Yuxian County in Hebei Province were analyzed and the bioconcentration factors of I. indigotica from different regions discussed. The study would provide data support and scientific basis for further studies of safe and rational development in crude Chinese drugs. The results showed that the contents of Cd, Pb, Hg and As in soil varied little in I. indigotica cultivated regions of Anguo City and Yuxian County in Hebei Province, with a range of coefficient of variation of 11.70%-97.65%. In the evaluation of the levels of soil contamination based on Class 1 standard for Cd, Pb, Hg and As of the Environmental Quality Standard for Soils (GB 15618-1995), and the Nemerow index background values of heavy metals were used as assessment standard. The range of Nemerow index of 45% soil samples from I. indigotica cultivated regions was 0.7-1.0, which suggested that the soils in the study areas were at an alarming level of pollution. When Class 2 quality standard was used, both the single pollution index and the Nemerow index did not exceed 0.7, which suggested that the investigated soils were generally safe for cultivation of I. indigotica. In addition, the average contents of Cd, Pb, Hg and As in shoots of I. indigotica were respectively 0.22 mg·kg^-1, 0.89 mg·kg^-1, 0.04 mg·kg^-1 and 0.25 mg·kg^-1, with accumulation capacity rank of Cd > Hg > Pb > As. The average contents of Cd, Pb, Hg and As in roots of the herb were respectively 0.14 mg·kg^-1, 0.57 mg·kg^-1, 0.04 mg·kg^-1 and 0.26 mg·kg^-1, with accumulation capacity trend of Cd > Hg > As > Pb. The concentrations of Pb, As and Hg did not exceed the safety limitation based on the Green Trade Standards for Import-Export of Medicinal Plants Preparations (WM2-2001). However, the contamination index of Cd in shoots of I. indigotica was higher than 0.7 and Cd level in 9.09% of the plant samples exceeded the safety limitation, indicating that the levels of Cd in the herbs in both regions were at an alarming level of pollution. It was therefore recommended to follow Class 2 standard of soil quality set in the Environmental Quality Standard for Soils. The accumulation characteristics of heavy metals in roots and shoots of I. indigotica should also be of significant concern in GAP (good agricultural practices) soil quality evaluation.

Characteristics of soil heavy metals pollution in cultivated land in zones between ipsilateral dams of Liaohe River

LIU Qiang, ZHANG Wanqiu, ZHOU Guiyu, LIANG Lei, BAI Xiaoliang, CHEN Yang

2017, 25(10): 1545-1553. doi: 10.13930/j.cnki.cjea.170153

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Abstract:
The heavy metals[zinc (Zn), lead (Pb), copper (Cu) and cadmium (Cd)] contents in the 0-5 cm, 5-15 cm and 15-30 cm soil depths of zones between ipsilateral dams in ten sections along Liaohe River were detected and the pollution situation of single heavy metal was evaluated using the geological accumulation index method. The potential degree of ecological damage by heavy metals was comprehensively evaluated using potential ecological risk index. The aims of the study were to evaluate the pollution degree of heavy metals, and explore the agricultural safety in zones between ipsilateral dams of Liaohe River. The results showed that the average contents of Cu, Pb and Zn were 32.42 mg·kg^-1, 38.23 mg·kg^-1 and 47.35 mg·kg^-1, respectively. The contents of heavy metals in different sections and at various soil depths were lower than the GradeⅡstandard of the National Soil Environmental Quality Standard. The average content of Cd was 1.625 mg·kg^-1, which was 1.70 times higher than the Grade Ⅱ standard of the National Soil Environmental Quality Standard. While from Zhuer Mountain to YubaoTai Grand Bridge, the trend of soil Cd content increased, it decreased from Yubaotai Grand Bridge to the estuary. Then using the Liaohe Bridge as the divide, the average content of Cd in the upper stream region was 6.47 times that in the lower reaches. The geological accumulation indexes of Pb, Cu and Zn in each sample section were all lower than 1.0, but the geological accumulation index of Cd obviously reflected a pollution trend in the study area. Strong pollution in excess of Grade V standard mainly occurred in the upper reaches of Liaohe River. From Tongjiang port to Yubaotai Bridge, potential ecological risk index of various heavy metals was very strong. Hudedian, Daniudukou, on to Liaohe Bridge was an area with a strong ecological hazard. Then the dawn bridge area had a medium ecological hazard. Finally, Lengdong Bridge, Zhaoquan River and Liaohe River estuary constituted the area with slight ecological hazard. The contribution of Cd in various sections to potential ecological risk of multi-metal was 78.77%-98.23%, which was positively correlated with the potential ecological risk index. The performance trend of various heavy metals in terms of potential ecological risk index was similar to the distribution trend in geological accumulation index of Cd, with the maximum value in Tongjiang estuary.

Evaluation index system and empirical analysis of agro-ecological civilization on the county scale-A case study of Shijiazhuang City

LIU Ruosha, ZHAO Rudan, LI Zhenqin, ZHAO Haozhan

2017, 25(10): 1554-1564. doi: 10.13930/j.cnki.cjea.170555

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Abstract:
Agro-ecological civilization is a key embodiment of the construction of China's ecological civilization. The county-scale construction of an evaluation index system of agro-ecological civilization can be used to judge agro-ecological civilization and to implement different policies suitable to different counties. It is important to construct a scientific and ra-tional pattern of agricultural development. Starting with the construction of agro-ecological civilization and based on step-wise analytic hierarchy and cluster analysis, this paper used 22 indicators for four areas of ecological vitality, economic vitality, social vitality and coordination degree to construct a county-scale evaluation index system of agro-ecological civilization. In a case study of 17 counties in Shijiazhuang, the paper used the 2012 statistical data to conduct comprehensive analysis and appraisal of unit area of county agro-ecological civilization and put forward corresponding countermeasures and suggestions. It provided a more perfect theoretical basis for the construction of agro-ecological civilization. In terms of ecological vitality, the results showed a significant overall advantage for Xinle City, Pingshan County, Gaocheng City, Luancheng County, Lingshou County, Luquan City and Jinzhou City. For overall economic vitality, Gaocheng City, Xinji City, Luquan City and Zhengding County were preferred. In terms of social vitality, Pingshan County and Luancheng County were the best, while Zanhuang County, Gaocheng City, Jinzhou City and Wuji County were the worst. For coordination degree, Gaocheng City, Luquan City and Luancheng County were on the whole better. Inference from a comprehensive analysis of agro-ecological civilization at county-scale suggested that economic vitality had the greatest impact on comprehensive level of agro-ecological civilization. The more powerful counties in the economic field, the comprehensive level was higher. The above results showed that economic, social and coordination factors strongly supported the construction and development of agro-ecological civilization in the study area. Therefore in the process of construction of agro-ecological civilization in Shijiazhuang City, a full understand of the levels of ecological, social and economic development in the counties was critical. It was also important to adhere to the principle of local conditions and partition policy in improving the level of agricultural development and optimizing the pattern of agro-ecological development.

2017 Vol. 25, No. 10