中国生态农业学报(中英文)

Review of plastic film mulching system and its impact on soil ecological envi-ronment in China's rainfed drylands

JIANG Rui, GUO Sheng, MA Dedi

2018, 26(3): 317-328. doi: 10.13930/j.cnki.cjea.170760

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Abstract:
Plastic film mulching, as an important and effective cultivation mode that improves grain yield, has been widely used in rainfed agricultural areas in Northwest China. This study reviewed crop yield, soil moisture content, soil temperature, soil nutrient transformation and transport, and microbial population and activity under plastic film mulching conditions. The review was designed to provide theoretical support for improving plastic film mulching system in China's rainfed dry regions. Researches results showed that maize, wheat and potato increased yields significantly under plastic film mulching compared to no mulching condition. Yield increase was influenced by plastic film cover mode, with an average increase rate of 26.2%, 37.1% and 29.8%, respectively. Full-film mulching most significantly increased crop yield. Average yields of maize, wheat and potato were respectively 30.0%, 5.1% and 26.4% higher than ridge and furrow system with ridge mulching. Water use efficiencies of maize, wheat and potato under film mulching increased respectively by 42.8%, 10.9% and 92.8% over no mulching. Film mulching influenced vertical distribution of nitrate in the soil profile, with nitrate accumulation in the topsoil layer under plastic film mulching. Also film mulching improved nitrogen fertilizer use efficiency, and reduced nitrogen leaching and ammonia volatilization. However, there were some different conclusions on denitrification under film mulching system, which required further studies. The influence of film mulching on organic carbon was related to climate, soil, crop and mulching time, which meant that the results were not consistent. In addition, film mulching increased farmland soil microbial biomass and changed soil physical properties. Although film mulching significantly improved crop yields, it certainly affected the ecological environment via such processes as "extravagant water deprivation", increased greenhouse gas emission, soil organic matter exhaustion, mulch film residues, etc. Thus further systematic research on the controlling mechanisms, improvement strategies of film mulching technology and comprehensive evaluation of the effect of film mulching system on ecological environment needed urgent attention for sustainable development of agricultural production in China's arid areas.

Effect of tillage practices on soil water-stable aggregate stability in dry farm-lands in the Loess Plateau, Central Gansu Province

WU Jun, CAI Liqun, ZHANG Renzhi, QI Peng, ZHANG Jun, Yeboah STEPHEN

2018, 26(3): 329-337. doi: 10.13930/j.cnki.cjea.171094

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Abstract:
The semiarid western Loess Plateau is characterized by hilly landscape that is severely prone to soil erosion. Stability and distribution of soil water-stable aggregates could be affected by soil tillage methods in dry land areas. An improved understanding of the effect on soil and water erosion associated with the production of land is required for enhancement of agricultural sustainability in semiarid areas. A 15-year local field experiment was carried out to study the effects of different tillage methods and straw applications on soil water-stable aggregates and aggregate destruction mechanisms under spring-wheat/pea rotation using three Le Bissonnais (LB) and routine wet sieving (RW) methods. Three LB wet sieving methods used in the experiment were slow wetting sieving (SW) method simulating light rains (micro-cracking), fast-wetting sieving (FW) method simulating heavy rains (slaking), and wet stirring sieving (WS) method simulating disturbance (mechanical breakdown). Four aggregate size ranges were obtained by the sieving methods:2-5 mm (larger aggregate, LA); 0.25-2 mm (small aggregate, SA); 0.053-0.25 mm (micro-aggregate, MA); and < 0.053 mm (slit plus clay, SC). The results of the three LB methods and RW method were then compared and the mean weight diameter (MWD), relative slaking index (RSI) and relative mechanical breakdown index (RMI) of soil aggregates were calculated. The field experiment was located in the Rainfed Agricultural Experimental Station (35°28'N, 104°44'E) which belongs to Gansu Agricultural University in Dingxi, Gansu Province, China. The experimental work included the following tillage and straw mulching treatments:conventional tillage (T), no tillage (NT), no tillage with straw mulching (NTS), and conventional tillage with straw incorporation (TS). The treatments were arranged in a complete randomized block design with three replications. The soil samples were taken at three soil depths (0-5 cm, 5-10 cm and 10-30 cm). The results showed that after wetting treatments except the slow wetting method, the dominant fraction of fragments in each soil layer was < 0.25 mm under all four tillage treatments. The order of sieving method as for < 0.25 mm non water-stable aggregates content was RW > FW > WS > SW. MWD of soil aggregates for four sieving methods was in the order of SW > WS > FW > RW under all the four tillage treatments. This trend indicated that aggregate breakdown mechanism was in the order of:slaking > mechanical breakdown > micro-cracking. While NTS treated soils exhibited the highest MWD and water-stable aggregates content for all wet sieving methods in the 0-5 cm and 5-10 cm soil layers. MWD for NTS treatment was significantly greater (P ≤ 5%) than T and NT treatments. Also TS treatment showed the highest MWD and water-stage aggregates content in the 10-30 cm soil layer, but with no significant difference in MWD from NTS. Compared with T treatment, TS treated soils significantly improved MWD. RSI and RMI of soil aggregates were suppressed by NTS, TS and NT treatments, and NTS treatment had the highest effect. Straw addition significantly suppressed RSI and RMI of soil aggregates in all three observed soil layers. No tillage significantly suppressed RSI of soil aggregate in the 0-5 cm soil layer. The results suggested that heavy rain was the main factor destroying soil aggregates in rainfed farmlands in the Loess Plateau region in Central Gansu Province. NTS treatment performed best for sustainable agricultural development and soil and water conservation in the Loess Plateau region in Central Gansu Province.

Effects of herbicides on urea nitrogen transformation and greenhouse gas emission of soil in citrus orchards with different planting years

ZHENG Xiangzhou, WANG Yasa, ZHANG Yushu, ZHANG Jing, DING Hong

2018, 26(3): 338-346. doi: 10.13930/j.cnki.cjea.170662

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Abstract:
Soil microbes significantly influence the transformation and fate of nitrogen in soils by participating in the biology and biochemistry processes of soil nitrogen cycle. Research has shown that herbicides inhibit non-target soil microbes and the related biochemical processes. Therefore, herbicides have significant effects on plant uptake and utilization of nitrogen and its release from soil into the environment. This experiment aimed to explore the effects of herbicides on the transformation of urea nitrogen and greenhouse gas emissions in soils planted with citrus orchards for different years. It was important to evaluate the environmental safety of herbicides and nitrogen application in orchard soils. Thus a 2-factor, 3-level complete block design experiment[with herbicide factors of no herbicide, glyphosate of 10 mg·kg^-1 a.i. and butachlor of 10 mg·kg^-1 a.i.; and planting year factors of 0-year (woodland), 10-year and 30-year citrus orchard] was conducted under laboratory conditions with 200 mg(N)·kg^-1(dry soil) urea applied in each treatment. The results showed that urea hydrolysis rate, nitrification rate, denitrification loss and greenhouse gas emission of citrus orchard (10 and 30 years) were higher than those of the woodland (P < 0.05). Compared with woodland, the 10-year and 30-year citrus orchards increased soil total denitrification loss by 5.12 and 4.30 times, total N₂O emission by 7.80 and 2.74 times, and total CO₂ emission by 19.62% and 39.64%, respectively. Soil urea hydrolysis rate, nitrification rate and CO₂ emission in the 30-year citrus orchard were significantly greater than those in the 10-year citrus orchard. Compared with the 10-year citrus orchard soil, total CO₂ emission increased by 16.74%, but total denitrification loss was no significantly different in the 30-year citrus orchard soil. Glyphosate and butachlor significantly boosted urea hydrolysis in woodland soil, but had no effect on nitrification in the 30-year citrus orchard soil. Butachlor had significant negative effect on woodland CO₂ emission, but showed no effect on citrus orchard soil. Compared with the zero herbicide treatment, butachlor significantly (P < 0.05) boosted N₂O emission, respectively by 56.27% and 85.41% in the 10-year and 30-year citrus orchard soils. Glyphosate had no effect on soil total CO₂ and N₂O emission in soils under the three treatments of citrus planting year. Herbicides glyphosate and butachlor had no significant effect on nitrogen transformation in citrus orchard soils, but butachlor significantly boosted N₂O emission in citrus orchard soils.

Seasonal dynamics of soil organic carbon fractions under straw and plastic film mulching of spring maize

MAO Hailan, WANG Jun, FU Xin, LI Rongrong, ZHAO Dandan

2018, 26(3): 347-356. doi: 10.13930/j.cnki.cjea.170603

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It is important to investigate soil microbial biomass carbon, potential mineralized carbon and particulate organic carbon under different tillage patterns, mulching methods and fertilization regimes for evaluation of soil carbon pool change due to agricultural management. Based on a long-term mulching experiment in dry highland of the Losses Plateau, this study investigated dynamic changes of soil organic carbon at different crop growth stages under straw and plastic film mulching conditions. The aim of the study was to explore seasonal responses of soil organic carbon and its fractions to surface mulching and deepen the understanding of soil carbon cycle in dry farmland. The data were collected from the 8 years experiment with the treatments of straw mulching, plastic film mulching and no mulching (CK) at pre-sowing, seeding, jointing, belling-heading, filling and harvest stages of spring maize. The seasonal dynamics of soil organic carbon, microbial biomass carbon, potential mineralized carbon and particulate organic carbon in 0-10 cm, 10-20 cm and 20-40 cm layers were determined. The results showed that:1) the contents of soil organic carbon, microbial biomass carbon, potential mineralized carbon and particulate organic carbon showed a tendency of decreasing at seedling stage, increasing at jointing stage, decreasing again at belling-heading stage and recovering at filling and harvest stages. 2) Compared with the CK, straw mulching effectively increased the contents of soil organic carbon and its fractions at most growth stages of spring maize, which improved soil fertility and enhanced carbon sequestration. Plastic film mulching did not show significant effects at the early growth stages, but decreased soil organic carbon and its fractions contents at the later stages of spring maize. 3) The ratio of microbial biomass carbon to soil organic carbon did not change with growth stages among treatments. However, particulate organic carbon in 0-10 cm under straw mulching was significantly higher than that under CK and plastic film mulching treatments, indicating that it hugely contributed to the dynamics of soil organic carbon in the topsoil layer under straw mulching treatment. The dynamics of soil organic carbon under plastic film mulching were mainly attributed to changes in particulate organic carbon and potential mineralized carbon. 4) The proportions of potential mineralized carbon and particulate organic carbon decreased at belling-filling stage with plastic film mulching or without any form of mulching, but did not change throughout the growing season with straw mulching. This indicated that straw mulching recharged soil potential mineralized carbon and particulate organic carbon during later growth stages. In conclusion, straw mulching of spring maize in the Loess Plateau significantly increased soil organic carbon and its fractions contents with obvious seasonal variations, while plastic film mulching showed decreasing effect at later growth stages of spring maize.

Temporal-spatial dynamics of wild bee diversity in agricultural landscapes in Changping District, Beijing

WU Panlong, SONG Xiao, XIA Bohui, XU Huanli, LIU Yunhui

2018, 26(3): 357-366. doi: 10.13930/j.cnki.cjea.170829

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Abstract:
Pollination is one of the most important ecosystem services provided mainly by bees for crops and wild plants. The universality, adaptability and diversity of wild bees are driven more as reliable pollinators than honey makers. However, the diversity of wild bees had significantly reduced in recent years due to the loss of habitat and the erosion of habitat quality, which potentially threaten pollination service and agricultural sustainability supported by bees. The functional group diversity of wild bees is also the important component of diversity, which is a better predictor of pollination than species diversity. Wild bee species with different functional traits need different resources and respond to environmental changes differently. However, there is little knowledge on the response of different functional groups of wild bees to habitat types. To determine the spatio-temporal dynamics of wild bees in different habitats and the importance of different habitats for wild bee conservation in agricultural landscape mosaics, netting-catching was used to collect wild bees in four habitats (planted woodland, natural shrub forest, wasteland and peach orchard) during the period from April to September 2016. The temporal dynamics of diversity of wild bees and their functional groups in different habitats were analyzed. The results showed that natural shrub forest had the highest individual numbers and species richness of wild bees, large bees, solitary bees; and highest individual number of medium-sized bees. While planted woodland had more individuals of small bees, peach orchard had the lowest individuals number and species richness of wild bees. Natural shrub forest, planted woodland and peach orchard all had similar temporal dynamics of wild bee diversity, with one peak in spring and the other in summer. Overall, all functional groups of wild bees had the highest diversity in natural or semi-natural habitats across the sampling seasons. Peach orchard had the lowest wild bee diversity in May, which was attributed to intensive management of groundcover in peach orchards. Similarly, there were more unique species solely in natural shrub forest because of high resource availability and low human disturbance. Other habitat types also had some unique species which contributed to the overall bee diversity in the region. The four most abundant species were respectively Nomia thoracica, Halictus aerarius, Ceratina flavipes and Lasioglossum halictoides, which had different temporal dynamics in the habitat types. The species N. thoracica and C. flavipes were distributed in all the habitat types, except for wasteland. While N. thoracica was active in June through August, C. flavipes was active throughout all the sampling seasons. H. aerarius and L. halictoides existed in all habitat types, with the former active from May through September and the latter from April through July. Therefore, the four habitat types all had essential resources for wild bees, but the natural and semi-natural habitats were more important. In particular, natural shrub forest sustained more bees and had greater pollination efficiency. It was concluded that habitat diversity (especially natural and semi-natural habitat diversity) and less intensive management during active seasons of wild bees were critical for improving wild bee diversity and pollination services.

Research progresses in the effects of rhizosphere oxygen-increasing on rice root morphology and physiology

ZHOU Wanlai, YI Yongjian, TU Naimei, TAN Zhijian, WANG Hongying, YANG Yuanru, WANG Chaoyun, YI Zhenxie

2018, 26(3): 367-376. doi: 10.13930/j.cnki.cjea.170680

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Abstract:
Rhizosphere oxygen is an important environmental factor that influences paddy filed environment and physiological metabolism of rice root. Existing reviews about rhizosphere oxygen are usually from the perspectives of hypoxia or anoxia stress. In recent years, more and more researchers implemented active oxygen-increasing in rice cultivation and obtained a large number of results. Rhizosphere oxygen-increasing significantly affects the morphology and structure of hydroponic rice root, making rice roots slender and elongated. It may be due to the reduced demand for preventing the leakage of oxygen and invasion of reducing substances, which means there is no need to form a barrier against radial O₂ loss, so the thickness of outer layer cell wall of root is smaller than that under hypoxic or anoxic stress conditions. It's suggested that there is an internal consistency among the root morphology, structure and functional requirements of rice under aerobic condition. Rhizosphere oxygen-increasing significantly promotes root vigor with an increment from 10% to 150% and with great differences among varieties. From the aspects of root morphology, physiological activity and transformation of nitrogen form in root-zone, e.g., the increased fine root, the raised root vigor, the enhanced nitrification under aerobic treatment, rhizosphere oxygen-increasing is beneficial for rice roots to uptake nitrogen, however its effects on nitrogen accumulation in rice is complex and related with the method and degree of oxygen-increasing treatment. Excessive oxygen-increasing inhibits the use of nitrogen in rice plants, thus limiting the increase in biomass, which in turn inhibits the absorption and accumulation of nitrogen. Response of rice to oxygen-increasing is not a simple reverse of that to hypoxia or anoxia stress, the dramatic yield decrease of rice under oxygen-saturation treatment demonstrated the complexity of rice response to oxygen-enrichment environment. It's proposed that exploring the effects of rhizosphere oxygen-increasing on pre-third-leaf stage rice seedling and rice nitrogen metabolism, quantifying the demand for oxygen of field rice and seeking feasible oxygen-increasing measures in seedling stage was of great significance for further improving rice seedling raising technology and theory.

Responses of dry matter distribution and water use of summer maize (Zea mays L.) to intercropped cultivars competition on the Loess Plateau of China

WANG Xiaolin, XU Weizhou, ZHANG Xiong, ZHANG Suiqi

2018, 26(3): 377-387. doi: 10.13930/j.cnki.cjea.170698

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Abstract:
On the Loess Plateau, maize morphological structure and yield performance are restricted by low rainfall and limited soil nutrient. Resource competition in intercroped cultivation have a postive effect on individual establishment and biomass allocation of maize cultivars. It was necessary to research root morphology and biomass allocation of maize under the combined effect of rainfall, planting density and intercropping for exploring effects of intercropping models on grain yield and water use efficiency (WUE) of maize in the Loess Plateau. To this end, a field experiment was conducted at Changwu Agri-ecological Station in the Loess Plateau, Chinese Academy of Science which is located in the classic dry farmming region in the semi-arid region of the Loess Plateau in Northwest China. Two maize cultivars ('Z958' and 'S16a') were intercroped under two planting densities (45 000 plants·hm^-2 and 75 000 plants·hm^-2) with 1:1 lines ratio. The aboveground and belowground growth and biomass accumulation were investigated at different growth stages of maize in tow rainfall year types, 2011 with rainfall of 647 mm and 2012 with rainfall 497 mm. The study also measured and analyzed the correlation among biomass allocation, root distribution, grain yield and WUE. The results showed that:1) soil water deficiency had a negative effect on root surface area (SA) of 'S16a' at flowering stage under low intercropped planting density. Also while SA of 'Z958' decreased by 30.5% under high intercropping density, WUE increased with increasing intercropping density. After two years of experimentation, root length density (RLD) in the 0-20 cm soil layer significantly increased under 'Z958' and 'S16a' intercropping. Also with increasing planting denstiy, rainwater deficiency led to deeper root growth to enhance water uptake. This in turn enhanced root competition for water and eventually obviously increased RLD in the 30-40 cm soil layer. Root distribution of 'Z958' was higher than that of 'S16a' for the two planting densities. 2) Biomass accumulation under two cultivars intercropping was genotypically different, with enhanced 'Z958' growth during vegetative period and enhanced 'S16a' growth during reproductive period. The individual biomass of two maize cultivars decreased with increasing intercropping density. The increase in dry weight at reproductive growth period was higher for 'S16a' than for 'Z958' in 2011 under low intercropped planting density. With high density and drought condition, individual biomass accumulation decreased under maize cultivars intercropping after flowering. 3) There was on average 6.0% increase in harvest index (HI) under high intercropping density and HI increased with increasing rainfall. Root and shoot growth was normal due to light competition under sufficient precipitation and low planting density. Soil drought and high intercropping density resulted in significant decrease in root to shoot rate (RSR) of 'Z958' as root competition for water increased. 4) In drought year (2011), competitive advantage was fully apparent in the two cultivars intercropping system, with yield and WUE increases of respectively 10.3% and 21.4%, 28.2% and 42.0% under two intercropping densities. Furthermore, yield and WUE of intercropped 'Z958' were 17.6% and 50.0% higher than that of 'S16a' for the two-year experimental period. Finally, 'Z958' showed rational biomass distribution and response to soil drought when intercropped with 'S16a' via reducing redundant root growth and decreasing excessive resouces use. Effective root morphological adjustment and biomass distribution of 'Z958' were responsible for the yield and WUE increase.

Growth periods variation of summer maize and winter wheat and their corre lations with hydrothermal conditions in recent years in China

CUI Yaoping, XIAO Dengpan, LIU Sujie, LI Nan, JIANG Lin, SHI Xinyu, LIU Xiaomeng, LI Jiangsu, LU Jingqi, QIN Yaochen

2018, 26(3): 388-396. doi: 10.13930/j.cnki.cjea.170693

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Crop phenology is influenced by both climatic and agronomic conditions, especially temperature and precipitation, which directly affect tillage schedule. A climatic phenomenon of warming hiatus has been noted since 2000. This phenomenon differs with the popular views of global warming. From the perspective of crop phenology, numerous studies have been conducted to assess the changes in growth periods of summer maize and winter wheat in the past decades. A relatively clear linkage of phenology and climatic conditions has been confirmed. As necessary climatic variables for crop growth, both temperature and precipitation influence the processes of crop growth, including the time of occurrence of the main phenology and length of the growth period. However, the relationship between phenology and climatic condition in recent years has been hindered by the lack of specific analysis that corresponds this relationship with the warming hiatus. For this specific period therefore, analyzing inter-annual changes of main phenological events and exploring the relationship between phenology and temperature as well as precipitation have become necessary for assessing current and future impacts of climatic conditions on crop growth and food security. Using observed phenological and meteorological data for 2000-2013, this study focused on analyzing of phenological characteristics and variations in growth periods of summer maize and winter wheat. Corresponding matches were built among hydrothermal conditions during the growth periods of the two crops and then the relationships between the length of growth period and hydrothermal conditions were analyzed. Spatial analysis method was used to find the proximal meteorological stations to phenological stations. Also, classical statistic was used to analyze the trends in phenology of the two crops and the relationships between phenology and hydrothermal conditions. The results showed delays in the main phenological events of summer maize and winter wheat. About 64% of the observed data stations showed that maturity of summer maize had delayed and the proportion of station with delayed trends in winter wheat was 78%. For the period covered in the study, the growth periods of summer maize and winter wheat were more sensitive to temperature and precipitation changes. About 88% of the stations used for summer maize and 64% of the stations used for winter wheat showed negative correlation between growth period length and temperature. While 71% of the stations used for summer maize and 77% of the stations used for winter wheat showed positive correlation between growth period length and precipitation. The reason for these tends was attributed to climate change. Different from the general understanding of global warming, average temperature during the growth period of summer maize did not show an obvious increase or decrease in trend, but precipitation obviously increased in most of the stations. The proportion of the stations with increasing trends in precipitation was more than 68%, while both cold and dry trends were observed during the whole growth period of winter wheat. The proportion of the stations with decreasing trend in temperature or precipitation all was more than 60%. In addition, analysis of the crop rotation stations revealed that annual climate data could be used in place of climate data for the growth periods to analyze for phenology and growth of rotational crops.

Effects of line-spacing expansion and row-spacing shrinkage on canopy structure and yield of spring corn

HE Dongdong, YANG Hengshan, ZHANG Yuqin

2018, 26(3): 397-408. doi: 10.13930/j.cnki.cjea.170623

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Abstract:
To explore the physiological and ecological mechanisms of expanding line-spacing and shrinking row-spacing for increasing planting density and yield of spring corn in Xiliaohe Plain, a study was conducted with two corn varieties (the compact density-enduring variety 'Nonghua 101' and the semi-compact variety 'Weike 702') with planting densities of 6×10⁴ plants·hm^-2 (D1), 7.5×10⁴ plants·hm^-2 (D2) and 9×10⁴ plants·hm^-2 (D3). Then the conventional cultivation was used as the control treatment (CK) with row-spacing of 60 cm and plant-spacing of 27.78 cm (D1), 22.22 cm (D2) and 18.52 cm (D3). The expanding line-spacing and the shrinking row-spacing mode of cultivation (KH) had row-spacing of 100 cm and plant-spacing of 16.67 cm (D1), 13.33 cm (D2) and 11.11 cm (D3). The leaf area index, stem leaf angle, leaf orientation value, light transmittance of corn canopy at spinning stage, milk-ripe stage and full ripe stage and component factors of yield were determined, and also leaf area attenuation rate was calculated. Then the effects of expanding line-spacing and shrinking row-spacing on spring corn yield and canopy structure were determined. The results showed that the yields of KH treatments were significantly higher than that of CK treatments, where the yield increased most obviously under D2 density. Leaf area index of KH was higher than that of CK at late growth stage, and reached the highest value at milk-ripe stage with the most obvious variation under D2 density. Stem leaf angle of the upper leaves was smaller and with higher leaf orientation value than those of the lower ones. Stem leaf angle of middle and lower leaves were larger but with smaller leaf orientation values than those of the upper ones for 2 varieties under KH treatments. The light transmittances of canopies were higher than those of CK for both varieties under KH plantation mode. For D1 density, light transmittances of canopies of 'Weike 702' was in the order of top layer > spike layer > bottom layer, except in 2015. Under the D2 and D3 densities, light transmittances of canopies of 'Weike 702' was in the order of spike layer > top layer > bottom layer. The differences were most obvious under D2 density, except in 2015. In conclusion, canopy structure of KH planting pattern was more reasonable under higher planting density resulting in higher yield. The responses of different varieties to KH planting pattern were different. Leaf area index and stem leaf angle of 'Nonghua 101' were lower than those of 'Weike 702'. Leaf aspect and canopy transmittance were also higher than those of 'Weike 702'. Measured yields of 'Nonghua 101' under different densities were higher than those of 'Weike 702', and the highest yield was under the 7.5×10⁴ plants·hm^-2 planting density. Moreover, yield increase of 'Nonghua 101' was more obvious than that of 'Weike 702'.

Effects of DCMU on anthocyanin synthesis genes and its related signals in C₄-pepc gene overexpressed rice under drought conditions

HE Yafei, XU Mengjie, LI Xia

2018, 26(3): 409-421. doi: 10.13930/j.cnki.cjea.170647

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Abstract:
Anthocyanins are important antioxidant materials that protects plant from damage by reactive oxygen species (ROS). Especially under adverse conditions, the regulation of sucrose in plants depends on its ability to induce anthocyanin accumulation. To determine the intrinsic relationship between photosynthetic and anthocyanin regulated pathways for C₄-phosphoenolpyruvate carboxylate (PEPC, EC 4.1.1.31) gene overexpressed rice (PC) in drought conditions, PC and untransformed wild-type (WT) were treated with 50 μmol·L-1 photosynthetic inhibitor DCMU for 1 h and the performance of the rice seedlings at 4-5 leaf stage observed under 12% PEG-6000 simulated drought. The results showed that DCMU pretreatment significantly reduced relative water contents of WT and PC under simulated 12% PEG-6000 drought condition, and relative water content of PC was significantly higher than that of WT. The anthocyanin content was higher in PC than in WT under 12% PEG-6000 simulated drought or drought plus DCMU pretreatment. 12% PEG-6000 simulated drought decreased anthocyanin contents of PC and WT, while DCMU pretreatment alleviated this effect. Compared with 12% PEG-6000, DCMU plus 12% PEG-6000 significantly inhibited net photosynthetic rate, stomatal conductance, intercellular CO₂ and carboxylation efficiency of the two rice lines, but these parameters of PC lines were significantly higher than those of WT lines. Then DCMU plus 12% PEG-6000 down-regulated endogenous sucrose content of the two materials, but sucrose content of PC lines was significantly higher than that of WT lines. Further studies showed that higher sucrose level in PC was associated with higher expression levels of transcriptional factors of bHLH (OsB1, OsB2), R2R3-MYB (OsC1), COP1 (constitutively photomorphogenic 1), HY5 (elongated hypocotyl 5), OsPAL, OsCHI, OsCHS, OsF3H, OsF3'H, OsDFR and OsANS, which resulted in synthesizing more anthocyanin to improve water retention capacity. In addition, PC rice sensed drought signals through NO and Ca²⁺, which participated in the regulation of transcription factors, regulation of anthocyanin synthesis gene, synthesis of more anthocyanin and thereby enhanced PC rice response to drought stress. This enhanced water retention capacity, stabilized photosynthetic capacity and resisted drought. Therefore, it was beneficial in molecular breeding of "C₄ Rice" to study the symphony between high yield and plant resistance.

Prediction of spatial distribution of soil available iron in a typical hilly farm-land using terrain attributes and random forest model

YANG Qipo, WU Wei, LIU Hongbin

2018, 26(3): 422-431. doi: 10.13930/j.cnki.cjea.170461

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Abstract:
Soil available iron is essential for plant growth. Detailed information on the spatial distribution of soil available iron is critical for effective management of soil fertility. To date, published works on soil available iron have mainly focused on the spatial variability and little has been done on predicting the spatial distribution of soil available iron. To understand the spatial distribution of soil available iron in hilly areas of Southwest China, we conducted a study in 2014 at a 2-km² typical hilly region with uniform soil parent materials in Yongxing Town, Jiangjin County, Chongqing City. A total of 309 soil samples were collected from cultivated lands at the depth of 0-20 cm. The samples were randomly divided into calibration (224) and validation (85) samples. Nine terrain attributes (including elevation, slope, aspect, valley depth, horizontal curvature, profile curvature, convergence index, relation position index and topographic wetness index) were extracted from a digital elevation model of spatial resolution of 2.0 m. Ordinary Kriging (OK), Multiple Linear Regression (MLR) and Random Forest (RF) analyses were used to predict the content of soil available iron based on the terrain attributes. Accuracy indicators, including mean absolute error (MAE), root mean square error (RMSE) and coefficient of determination (R²), were used to evaluate model performance based on validation data. Correlation analysis showed that topographic wetness index and valley depth were significantly positively correlated with soil available iron content. Slope, horizontal curvature, profile curvature, convergence index and relative position index were on the other hand significantly negatively correlated with soil available iron content. Compared with OK and MLR, RF model performed best, with MAE=22.33 mg·kg^-1, RMSE=27.98 mg·kg^-1 and R²=0.76. Additionally, RF analysis indicated that topographic wetness and slope were the main factors controlling the spatial distribution of soil available iron. Soil available iron content in the study area was 3.00-276.97 mg·kg^-1, which was higher for paddy field than for dryland. Semivariance model showed strong spatial autocorrelation of soil available iron, indicating that structural factors were the main driving force of spatial variation of soil available iron. Therefore it was concluded that the RF model together with terrain attributes well explained the spatial variability of soil available iron in the area. The result of the study provided valuable information for studies on predicting the spatial distribution of trace elements in soils in hilly areas.

Evaluation of cultivated land consolidation suitability in Northeast China black soil zone using niche-fitness model: A case study of Gongzhuling City

XU Xiaoqian, WANG Jingkuan, LI Shuangyi, PEI Jiubo, YANG Ji, ZHANG Weijun

2018, 26(3): 432-441. doi: 10.13930/j.cnki.cjea.170633

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Abstract:
Cultivated land consolidation is a good protection measure of land resources, while land suitability evaluation forms the prerequisite and basis for cultivated land consolidation. Niche theory is generally used in ecological studies. Niche-fitness can be used to characterize the suitability of species to habitat conditions, which is increasingly applied on landscape studies. Similarly, it can be used to characterize the suitability of cultivated land consolidation index. With Gongzhuling City as the case study, this paper used niche theory and 14 indicators of four index layers (natural condition, infrastructure condition, ecological sustainability and spatial stability) to establish the suitability evaluation index system of cultivated land consolidation, . The Delphi method was then used in combination with Analytic Hierarchy Process (AHP) to determine the index weight. While the actual ecological niche of cultivated land consolidation was defined as the real index value, optimal ecological niche was defined as the ideal index value. Thus the evaluation models for the three index types (positive index, negative index and moderate index) were determined on the basis of the match degree between actual and optimal ecological niche. Based on this approach, the weighted sum of matching degree was calculated as the niche-fitness value of each evaluation unit. Finally, using the Ward method, the suitability of cultivated land consolidation were divided into 4 grades to evaluate cultivated land consolidation regions. Meanwhile, the optimal niche was proposed as a standard of cultivated land consolidation to establish the diagnosis model of obstacle indicators, clarifying the priority and orientation on cultivated land consolidation in different regions, searching countermeasures and valid paths. The results showed that the natural condition of cultivated land in Gongzhuling City was good and that cultivated land consolidation could be prioritized in the Southwest and North. About 13 799.89 hm² of land was highly suitable for cultivated land consolidation, which accounted for 4.16% of the total cultivated land. This area was restricted by farmland shelter belt ratio, road accessibility and the degree of field regularity. About 77 754.36 hm² of land was moderately suitable for cultivated land consolidation, accounting for 23.41% of the total cultivated land. The land was restricted by irrigation condition, road accessibility and farmland shelter belt ratio. About 177 192.38 hm² of land was mildly suitable for cultivated land consolidation, accounting for 53.36% of the total cultivated land. The land was restricted by soil organic matter content, distance from main traffic line and soil pH. The area unsuitable for cultivated land consolidation was 63 325.61 hm², accounting for 19.07% of the total cultivated land area. And the restrictive factors were soil texture, irrigation condition and topsoil thickness. It was suggested that the relevant departments should carry out corresponding measures of cultivated land consolidation in different regions and orderly implement the measures in the future. In conclusion, the application of the niche-fitness model in the evaluation of cultivated land consolidation suitability extended the application range of the theory of ecological niche. This provided the scientific basis for site selection and consolidation direction of cultivated land consolidation projects.

Evaluation of influencing of terrain factors on land use change based on improved Index Sum Method

WANG Shidong, WU Chao

2018, 26(3): 442-452. doi: 10.13930/j.cnki.cjea.170593

Abstract(1027) HTML (26) PDF(1082)

Abstract:
Land use change is the interaction result of human activities and natural environment under social and economic impact. Discovering factors affecting land use change is the hot spot and has very important significance for researches on resources, environment and socioeconomic issues. Terrain directly influences land use change. Therefore, it is crucial to explore the extents of terrain affecting the regional land use changes. In order to explain the interaction of human-land system and provide the basis for sustainable land use, environmental protection and ecological reconstruction, we conducted a research on the performance of terrain factors with regard to land use change. The study aimed to explore the influence extents of terrain factors on regional land use change, so as to provide scientific basis for regional land development and land use spatial structure, direction and mode. In view of the existing problems in the research field, based on the natural conditions, land use characteristics and terrain factors of the study area, we chose 12 evaluation indexes from the macro-terrain factors and micro-terrain factors to establish the evaluation index system. Then, a comprehensive evaluation model of terrain factors influencing on land use change was established based on the improved Index Sum method. Indexes weights were determined by combining Entropy method and Decision Alternative Ratio Evaluation System to overcome the objectivity of the Entropy method and improve the rationality of weight determination of the improved Index Sum method. The influencing extent of terrain factors on land use change in Luanchuan County of Henan Province was evaluated using the established method. The results showed that the influencing extents of terrain factors of evaluation, slope, slope direction, slope length, slope direction variability and surface cutting extent increased from 2005 to 2015, while those of slope variability, plane curvature, profile curvature, elevation variation coefficient, terrain relief and terrain roughness decreased. The change in comprehensive influencing extent of terrain factors on land use change was 0.000 978 and the change rate was 7.06% from 2005 to 2010, which were -0.001 705 and -11.50% from 2010 to 2015, and -0.000 727 and -5.25% from 2005 to 2015. These results showed a tendency of increase-decrease of terrain factors influencing extent on land use change from 2005 to 2015. The evaluation results showed that the terrain factors, as the natural driving factors of land use change, had a decreasing trend of influence extent with the social and economic development, improvement of human technology, rationalization of political and economic structure and environment protection. The results provided the important data reference and scientific basis for regional land use planning, urban construction and ecological environment protection.

Meteorological conditions and rating method of quality formation of 'Cabernet Sauvignon' grape in eastern foothills of Helan Mountain

MA Liwen, LI Jianping, HAN Yingjuan, LI Wanchun

2018, 26(3): 453-466. doi: 10.13930/j.cnki.cjea.170579

Abstract(1147) HTML (36) PDF(964)

Abstract:
The quality of grape wine is largely determined by the quality of grapes, which is closely related to meteorological conditions during grape growing season. Under normal management conditions and agricultural technology, the method of evaluation of meteorological conditions for fruit growth is called quality meteorological evaluation of wine grape. Meteorological condition rating techniques and meteorological indexes research on wine grape quality formation provide the base lines of climatic conditions for rating commercial wine, vintage identification and hoarding. In this paper, five indexes were tested for total sugar, total acid, sugar-acid ratio, pH and tannin content of 101 'Cabernet Sauvignon' fruit samples collected at various sites in eastern Helan Mountain during 2003-2011. Test data for 51 samples were selected to analyze for correlations with meteorological data for fruit growth. Based on the analysis of biological effects of meteorological factors on quality, meteorological factors affecting each quality index were determined for significant level. Based on the determination coefficient of each meteorological factor to a quality index, five weight models of quality indexes with significant meteorological factors were constructed. Thus the quality indexes of 'Cabernet Sauvignon' grape were reckoned with the meteorological conditions for fruit growth period. Using determination coefficients of meteorological factors as weight, an integrated meteorological simulation model with 5 quality indicators was constructed and a comprehensive quality meteorological evaluation model was established by using the weight of individual quality indicators. Using related research results coupled with the winemaker suggestion, a comprehensive meteorological scoring model for wine grape quality was constructed based on the contribution of each quality index and wine quality. In relation to previous studies and the criteria of quality of grape and wine, 5 quality indicators and quality grades were classified. The threshold meteorological factors corresponding to the wine quality and classification criteria for grape climatic conditions of 'Cabernet Sauvignon' were also determined. It implied that based on the requirements of total sugar, total acid, sugar-acid ratio, pH and tannin content needed for brewing high quality wine, the 5 quality indicators and comprehensive meteorological grades of 'Cabernet Sauvignon' were divided into five grades. This included excellent (grade 5), very good (grade 4), good (grade 3), medium (grade 2) and poor (grade 1). Then based on the threshold of each quality grade and the comprehensive meteorological simulation equation of the above 5 quality indicators, the threshold of the meteorological factors affecting each quality grade was deduced. This was in turn used as the meteorological factor classification index for evaluating the climate condition for quality of 'Cabernet Sauvignon' grape. The effects of simulation and grape classification of the 5 quality indicators and 'Cabernet Sauvignon' grape in the foothills of Helan Mountain were tested using the 51 samples selected to establish the model. The results showed that all the models of the 5 quality indicators passed the 0.001 R-test and F-test, indicating that the estimated values were within the measured values and that the variation trends were consistent. Among these, the simulation effects of total sugar content, total acid content, sugar-acid ratio and tannin content were better (R ≥ 0.59 and small RMSE) than the effects of pH (where there was a relative large simulation dispersion). To predict the effects of the evaluation model and indexes by using the other 50 samples that were not included in the model development and meteorological data during fruit development, the effects of the grading were tested for 'Cabernet Sauvignon' grape quality in the eastern foothills of Helan Mountain. The results indicated that the contents of total sugar and total acid were close to the measured values. In addition to a relative large error for few samples of sugar-acid ratio and tannin content, the error for the other samples was relatively small and the overall trend was consistent with the measured values. pH was relatively stable and all the samples were within the appropriate range for brewing high-quality wine, and differences in yearly meteorological conditions were difficult to determine, indicating that the local climatic conditions were conducive for the pH needed for high quality wine brewing. From the comprehensive score and grade, 28 samples were the same as the actual level and only 4 samples differed at 2 levels. The rest of the samples were within level 1, which more accurately reflected the quality of raw materials. The meteorological evaluation indexes and models of 'Cabernet Sauvignon' provided a feasible tool for evaluating the quality of wine grape in the eastern foothills of Helan Mountain.

2018 Vol. 26, No. 3