中国生态农业学报(中英文)

Effects of exogenous carbon input on soil organic carbon mineralization and temperature sensitivity of cropland and wetland in the North China Plain

WEI Yuanyun, CUI Lijuan, ZHANG Manyin, LIU Weiwei, WANG Da'an, YANG Si, XIAO Hongye

2019, 27(10): 1463-1471. doi: 10.13930/j.cnki.cjea.190214

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Abstract:
The influences of exogenous carbon input and climate warming are two key factors of soil organic carbon mineralization. Based on a ¹³C stable isotope labelling technique, we conducted a laboratory incubation experiment to investigate the priming effect and temperature sensitivity of soil organic carbon mineralization of cropland and wetland in the North China Plain to understand and forecast soil carbon dynamics under global climatic change. Topsoil collected from cropland and wetland of Hengshui region were with or without ¹³C-labeled glucose[0.4 mg(C)∙g^-1] at two temperature (15℃ and 25℃) for 35 days. Soil CO₂ emission and its ¹³C isotopic composition was measured at days 1, 3, 5, 7, 10, 14, 21, 28 and 35. Our results suggested that the soil organic carbon mineralization was significantly influenced by land use type, temperature, and glucose addition. The soil organic carbon mineralization of the cropland was approximately equal to that of the wetland without glucose addition but it was significantly higher than that of wetland with glucose addition at the same temperature. Except the wetland soil cultured at 15℃, glucose addition exerted a significantly positive priming effect on soil organic carbon mineralization in wetland and cropland soil. However, the priming effect of the cropland was significantly higher than that of wetland. Soil organic carbon mineralization was also accelerated by increased temperature, and the Q₁₀ value of its temperature sensitivity fluctuated between 1.2 and 1.6 during incubation. The temperature sensitivities of soil organic carbon mineralization were not significantly changed by different land use types and glucose addition. In conclusion, the soil organic carbon mineralization of the cropland was significantly higher than that of wetland under warming conditions and exogenous carbon input.

Effects of rubber planting patterns on ant diversity in low climate suitable area

YU Xiaoyu, LU Zhixing, LI Qiao, YAN Di, CHEN Youqing

2019, 27(10): 1472-1480. doi: 10.13930/j.cnki.cjea.190062

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Abstract:
Rubber is a very important economic crop in China, its' cultivation area in the medium to low climate suitable area accounts for about 79.06% of the total area. In recent years, the status of biodiversity in low climate-suitable areas and methods used to choose planting patterns to protect biodiversity in rubber growing area need immediate attention. In order to reveal the differences of ground-dwelling and canopy foraging ant communities in rubber plantations (Ⅱ), rubber-tea agroforestry (Ⅲ), rubber-coffee agroforestry (Ⅳ), and Dalbergia obtusifolia-corn agroforestry (control plot, Ⅰ), species diversity, community structure differences, and indicator species of ant communities were investigated using traps in September 2015 and August 2016 in 4 different types of sites. The results were as follows:the abundance, species richness, and ACE index of ground-dwelling ant communities demonstrated significant differences among the 4 types of sites, ranked as Ⅲ > Ⅱ > Ⅰ > Ⅳ (P < 0.05). Moreover, the abundance of canopy foraging ant communities revealed significant differences, ranked as Ⅱ > Ⅲ > Ⅳ > Ⅰ (P < 0.05). However, species richness and ACE index did not exhibit significant differences (P > 0.05). The community structure of both the ground-dwelling and canopy foraging ant communities displayed significant differences among the 4 types of sites (P < 0.01). The ant community structure of rubber-tea agroforestry had higher similarity with other sites. There was one indicator species in each of the 4 types of sites, such as Pheidole spathifera in Dalbergia obtusifolia-corn agroforestry, Tapinoma melanocephalum in rubber plantations, Odontomachus circulus in rubber-tea agroforestry, and Tetraponera birmana in rubber-coffee agroforestry. Our results indicate that the rubber-tea agroforestry is a choice that has both economic benefits as well as offers good protection to ant communities in the local rubber plantations. Therefore, it is of interest to conduct further studies on the management of rubber plantation patterns.

Application of wildflower strips for agricultural landscaping

WU Xuefeng, GAO Yike, XIE Zhecheng, XU Jun

2019, 27(10): 1481-1491. doi: 10.13930/j.cnki.cjea.190330

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Abstract:
Wildflower strips in the agricultural landscape are constructed in strip or matrix forms as buffers on headlands, orchards, vegetable fields, etc. by means of mixture sowing. By combining different functional plants into communities, the wildflower strips provide nectar and pollen resources as well as habitats for natural enemies and pollinators. They also contribute in improving the quality of habitats; strengthen the support system for natural enemies; and provide different ecosystem services, such as improving pollination rates, reducing pesticide use, improving and restoring farmland soil, purifying water sources, and inhibiting weeds. The application and development of wildflower strips in Central and Western Europe and the United States were reviewed in this study. Wildflower strips originated in Switzerland but were first applied with the intention of ecological conservation in agricultural settings in Belgium. Over time, the ecological compensation mechanism improved in these countries. In United Kingdom, wildflower strip application occured with strong, detailed policy support involving the use of a variety of methods. However, in the United States, the promotion of native plants, grassland habitat restoration, and the conservation of key pollinators were emphasized. In China, the lack of landscape heterogeneity and habitat fragmentation was mainly caused by the invasion of exotic species and human intervention. The introduction of these methods of wildflower strip implementation as a means for habitat management and planning was crucial. The study on wildflower strip usage in China was still in the early stages of development and was not yet to be practically applied at larger scales. In the future, wildflower strip implementation would be initiated with simultaneous dynamic monitoring and investigation of plant community interactions along with various insect communities in existing non-crop habitats. These investigations will provide the data necessary to construct ecological networks after delimitation of ecological protection areas on a large scale. In addition, these studies will facilitate decision-making on suitable vegetation structures to combine natural and semi-natural habitats based on spatial and temporal dynamics of arthropod functional groups.

Spatial structure and influencing factors of countryside tourist attractions in Shandong Province

LI Shujuan, GAO Lin

2019, 27(10): 1492-1501. doi: 10.13930/j.cnki.cjea.190045

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Abstract:
Countryside tourism has become a new type of industry. In order to explore their spatial distribution pattern and characteristics, 193 countryside tourist attractions in Shandong Province were studies. The spatial distribution patterns of the countryside tourist attractions were analyzed using Geographic Information System (GIS) spatial analysis methods, such as the nearest neighbor index, multi-distance spatial clustering analysis, Ripley's function and kernel density analysis. Considering the overall and local advantages and disadvantages of multi-scale density analysis, Ripley's function was used to determine the optimal search radius for density, cold point and hot spot analysis. Shandong Province countryside tourist attractions had a nearest neighbor index (R) of 0.74, which indicates a typical spatial gathering distribution, mainly distributed in Qingdao, Jinan, Linyi, and Zaozhuang. The spatial differences in hot and cold areas were clearly detected and at the provincial level, showed a significant "block" distribution. Shandong Province countryside tourist attractions were influenced by traffic conditions, location, socioeconomic level, tourism resource endowment, topographical features and other factors. Based on these results, we put forward two proposals combined for the development of Shandong countryside tourism. Firstly, we propose the strengthening of the cooperation between the four regions of eastern Shandong, western Shandong, northern Shandong, and central Shandong to build multiple "core-edge" countryside tourism development areas. Secondly, we propose improvements in the tourist transportation network and the realization of links between different countryside tourist attractions.

Effects of swine slurry application on ammonia emission, nitrogen utilization and apparent balance of a winter wheat-summer maize rotation system

LI Shuo, WANG Xuan, ZHANG Xiqun, LIU Zelong, ZHAO Hao, ZHAO Zhanqing, ZHANG Yuming, SUN Hongyong, MA Lin

2019, 27(10): 1502-1514. doi: 10.13930/j.cnki.cjea.190150

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Abstract:
With the development of intensive swine production in China, large amounts of slurry are produced, which causes nitrogen and phosphorus loss and serious non-point pollution. A potentially efficient way to solve these environmental problems is to substitute mineral fertilizer with swine slurry in intensive maize (Zea mays L.)-wheat (Triticum aestivum L.) double-cropping rotation systems, which could promote the development of sustainable agriculture and animal husbandry. A field experiment was performed with swine slurry application in a maize-wheat double-cropping rotation system in the North China Plain. The study included the following seven treatments with three replications:zero-N control (CK); urea broadcast (CK1); urea injection (CK2); swine slurry as a substitute for 25% urea-N broadcast (25%WB), 50% urea-N broadcast (50%WB), 25% urea-N injection (25%WI), and 50% urea-N injection (50%WI). Swine slurry was applied to the soil before maize and wheat seeding. Compared with the CK, the application of urea and swine slurry significantly improved maize and wheat grain yield and N uptake, with the greatest effect seen in the 25%WI, followed by the 50%WI. Compared with the CK1, the N agronomic efficiency, N partial productivity, and apparent N recovery rate under treatments of urea injection and swine slurry broadcast and injection were significantly improved. The greatest improvement was seen in treatments of swine slurry injection, followed by treatments of swine slurry broadcast, but no significant difference was found between the 25%WI and 50%WI treatments. Compared with CK, the application of urea and swine slurry significantly improved nitrate accumulation. The increase in inorganic nitrogen ranged from 50.8%-87.9% throughout the 0-100 cm soil profile after maize harvest. No significant difference in nitrate accumulation was found among the 50%WB, 25%WI, and 50%WI treatments. Compared with CK1, swine slurry broadcast and urea and swine slurry injection significantly reduced the total amount of ammonia loss during the seeding period of maize and wheat, with reductions ranging from 26.5% to 48.6% and 11.4% to 29.1%, respectively. Meanwhile, swine slurry broadcast and injection significantly reduced N surplus from 7.6% to 16.0%, with the biggest difference found in the 25%WI treatments. However, no significant difference was found between the 25%WI and 50%WI treatments. In view of the yield, nitrogen utilization, and environmental benefits, swine slurry as a substitute for 25% and 50% urea-N injection were reasonable methods of swine slurry application in the intensive summer maize-winter wheat double-cropping rotation field.

Effects of soil layers exchange on key nitrogen transformation processes in soil and nitrogen utilization by maize

YANG Shuo, JIN Wenjun, HUANG Haimeng, WANG Jun, ZHOU Debao, ZHAO Yangyang, DONG Zhaorong, SONG He

2019, 27(10): 1515-1527. doi: 10.13930/j.cnki.cjea.190265

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Abstract:
Soil layers are exchanged during tillage practices, which may change the nitrogen (N) transformation process by affecting the physicochemical and biochemical properties of the soil. In this study, the effects of soil layers exchange on the nitrification and denitrification of lime concretion black soil, maize growth, and N utilization were studied to provide a theoretical basis for selecting reasonable tillage methods, reducing N loss, and improving N use efficiency in the southern region of the Huang-Huai-Hai Plain. In an artificial climate chamber, a normal soil layer distribution (0-35 cm of soil placed in a root box according to in situ soil layers) was used as the control treatment (CK). In-situ 0-10 cm and 10-20 cm soil layers were exchanged and placed in another group of root boxes, which were used as the soil layers exchange (SE) treatment group. A 20 μm nylon mesh was used to separate the rhizosphere and the bulk soil. To investigate the effects of soil layer exchange on soil N transformation, nitrification potential, respiration, denitrifying capacity, denitrification potential, physicochemical properties of the rhizosphere and bulk soil, as well as maize growth, and N use, total N content, and root morphology were investigated at the maize small trumpet stage. The results showed that maize N uptake in SE treatment was 8.9% lower than that of CK (P < 0.05). Soil layer exchange significantly affected the rhizosphere rather than the bulk soil, which reduced its nitrification potential by 13.5% (P < 0.05) and increased the denitrification capacity of the rhizosphere and the bulk soil by 36.6% (P < 0.05) and 8.4% (P < 0.05), respectively. Soil layers exchange increased the soluble organic carbon content of the rhizosphere and bulk soil by 11.7% (P < 0.05) and 5.2%, respectively. Correlation analysis showed that nitrification potential was significantly positively correlated with the abundance of ammonia-oxidizing bacteria (AOB, r=0.91^**), but was not significantly correlated with the abundance of ammonia-oxidizing archaea (AOA). Denitrification capacity was significantly positively correlated with soluble organic carbon and soil respiration (r=0.89^** and 0.93^**), but showed no correlation with nirK or nirS gene copy number. N uptake by maize plants was positively correlated with the nitrification potential of the rhizosphere and the total root surface area×AOB gene copy number (r=0.83^* and 0.86^*), but was significantly negatively correlated with denitrification capacity (r=-0.88^**). These results indicated that a decrease in the nitrification rate and an increase in the denitrification rate in lime concretion black soil could result in low N use efficiency by maize after soil layers exchange. The nitrification rate was driven more by AOB abundance. After soil layers exchange, soil soluble organic carbon was the key driving factor for denitrification capacity. Effective regulation of soil soluble organic carbon content is the key to improving crop nitrogen use efficiency under tillage conditions.

Effects of long-term straw return on corn yield, soil nutrient contents and en-zyme activities in dryland of the Loess Plateau, China

CHENG Man, XIE Wenyan, YANG Zhenxing, ZHOU Huaiping

2019, 27(10): 1528-1536. doi: 10.13930/j.cnki.cjea.190235

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Incorporation of straw in soil plays an important role in nutrient management, maintenance of crop productivity, and improvement of soil quality, which is considered to be an effective measure as a substitute for chemical fertilization. Understanding the effects of long-term straw incorporation on soil properties and corn yield in the dryland of the Loess Plateau are essential to provide scientific evidence for sustainable utilization and soil quality improvement of cropland. Here, based on a long-term (24 years) straw return field experiment, effects of different straw return regimes, i.e., straw mulching (SM), direct straw return (DS), animal-digested straw return (AS), and non-straw return (CK) on soil chemical properties, enzyme activities, and corn yield were studied. Results showed that the cumulative corn yield under SM, DS, and AS treatments were 1.885×10⁵ kg·hm^-2, 1.854×10⁵ kg·hm^-2 and 2.001×10⁵ kg·hm^-2, respectively; the yields increased by 10.1%, 8.6% and 15.3%, respectively, compared to CK treatment (1.695×10⁵ kg·hm^-2). Besides, the three long-term straw incorporation treatments enhanced soil organic carbon by 6%-14% in 0-20 cm soil layer, whereas they had no significant effect on soil organic carbon in 20-40 cm soil layer. Compared to CK, soil total nitrogen, total phosphorus, total potassium, available nitrogen, available phosphorus and available potassium contents were significantly increased under AS treatment; whereas DS treatment enhanced soil total nitrogen, total potassium, available nitrogen and available potassium contents; and SM treatment increased soil available nitrogen and potassium content. In addition, soil invertase activity was the highest under AS treatment, followed by SM and DS, and the lowest under CK treatment. Soil cellulase activity under DS treatment was 2.2 and 1.3 times higher in 0-20 cm and 20-40 cm soil layers, respectively, than that under CK treatment. Furthermore, AS treatment enhanced soil urease activity by 13.0% and soil alkaline phosphatase by 20.5% compared to CK, while SM and DS treatments had no significant effect on soil urease and alkaline phosphatase activities. Soil activities of invertase, urease and alkaline phosphatase showed a greater response to animal-digested straw return treatment, whereas soil cellulose activity had a greater response to direct straw return treatment. Furthermore, there was a significant positive correlation between corn yield and soil invertase activity. In conclusion, long-term continuous animal-digested straw return and direct straw return had a profound impact on soil nutrients and enzyme activities. Particularly, the increase in soil invertase activity by straw return is closely related to the promotion of corn yield.

Effects of shade cultivation and deficit irrigation on the growth and canopy structure of Coffea arabica L. in dry-hot region

HAN Zhihui, HAO Kun, LIU Xiaogang, HE Hongyan, LIU Lihua, YANG Qiliang

2019, 27(10): 1537-1545. doi: 10.13930/j.cnki.cjea.180991

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Abstract:
Highly efficient production of Coffea arabica L. is limited due to irrigation and light management challenges in dry-hot regions. To investigate the effects of an irrigation deficit on the growth and canopy structure of C. arabica under the shade of banana plants, a field experiment was performed using different irrigation levels and shade cultivation modes. A complete combination design was adopted, with three levels of irrigation, i.e. full irrigation (FI), light-deficit irrigation (DI_L) and severe deficit irrigation (DI_S), and four modes of shade cultivation, i.e. no shade cultivation (S₀:monoculture C. arabica), light shade cultivation (S_L:intercropping of four lines of C. arabica and one line of banana), moderate shade cultivation (S_M:intercropping of three lines of C. arabica and one line of banana) and severe shade cultivation (S_S:intercropping of two lines of C. arabica and one line of banana). Compared with FI treatment, other treatments of irrigation decreased the height increment and shoot length by 13.62%-23.94% and 8.82%-13.96%, respectively, and increased the total fixed-point factor by 9.55%-34.97%. Compared with S₀ treatment, other shading cultivation treatments increased the height increment, stem diameter increment, crown width increment, shoot length, and leaf area index of the canopy by 18.33%-33.65%, 6.43%-15.47%, 5.38%-12.60%, 8.82%-24.69% and 5.18%-22.85%, respectively; and decreased the opening, gap fraction, mean leaf dip angle, total fixed-point factor and transmittance of the canopy by 4.42%-15.50%, 4.85%-16.49%, 5.50%-15.07%, 13.78%-41.44% and 10.36%-31.78%, respectively. The opening, gap fraction, mean leaf dip angle, direct fixed-point factor, indirect fixed-point factor, total fixed-point factor, direct radiation of the crown, indirect radiation of the crown, transmittance, and extinction coefficient of the C. arabica canopy were significantly positively correlated with each other and were significantly negatively correlated with leaf area index. Cluster analysis indicated that the twelve treatments could be divided into three categories. The first category was FIS_S, DI_LS_S and FIS_M; the second category was FIS_L, DI_LS_L, DI_LS_M, DI_SS_S, FIS₀ and DI_SS_M; and the third category was DI_LS₀, DI_SS_L and DI_SS₀, when the distances between classes was five. It was clear that the best growth condition was the first category, which can be used as a suitable combination of irrigation and banana shade cultivation mode for C. arabica in dry-hot regions. The results of this study provide theoretical guidance for the irrigation and light management of C. arabica in dry-hot regions.

Effects of simulated nitrogen deposition on growth and photosynthetic characteristics of one-year-old Toona sinensis seedlings

PEI Haofei, GAO Weidong, FANG Jiaoyang, YE Keke, ZHU Yan, HUANG Fang, LI Qingmei

2019, 27(10): 1546-1552. doi: 10.13930/j.cnki.cjea.190168

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With global industrial and agricultural modernization, the characteristics and processes of various ecosystems have been profoundly affected due to increasing nitrogen deposition. Toona sinensis is a unique, dual-use plant widely distributed in China. It is used for medicinal purposes and is also a fast-growing timber tree species. To determine the threshold value of nitrogen deposition that could be sustained at the seedling stage of T. sinensis and to provide some theoretical basis for the cultivation of T. sinensis, a preliminary study was performed to test the response of annual T. sinensis seedlings to nitrogen deposition in summer. Annual T. sinensis seedlings were grown under the simulated nitrogen deposition experiment in summer. Urea was used as the nitrogen source, with six levels of nitrogen addition:0 kg(N)·hm^-2·a^-1, 20 kg(N)·hm^-2·a^-1, 40 kg(N)·hm^-2·a^-1, 80 kg(N)·hm^-2·a^-1, 120 kg(N)·hm^-2·a^-1, and 180 kg(N)·hm^-2·a^-1. The ground diameter, seedling height, biomass, and photosynthesis of T. sinensis seedlings were then measured. The results showed that nitrogen addition contributed to an improvement in the diameter, height, and biomass of T. sinensis seedlings. Ground diameter, height, and biomass were the highest after the addition of 180 kg(N)×hm^-2·a^-1 nitrogen and were 42.5%, 64.4%, and 304.9% higher, respectively, than the control values. The biomass of T. sinensis seedlings was distributed more to the root and leaf. The SPAD of seedling leaves increased with increasing levels of nitrogen addition. At the highest nitrogen addition of 180 kg(N)·hm^-2·a^-1, SPAD values were 73.9% higher than the control. The apparent quantum yield (AQY), maximum net photosynthetic rate (P_nmax), light saturation point (LSP), light compensation point (LCP), and the dark respiration rate (R_d) increased at first and then decreased with increasing levels of nitrogen addition. Except for LCP, which was highest at 80 kg(N)·hm^-2·a^-1, AQY, P_nmax, LSP, and R_d were the highest at 120 kg(N)·hm^-2·a^-1. This study showed that a certain level of nitrogen addition could promote the growth and enhance the photosynthetic ability of T. sinensis seedlings. However, there is a limit to the nitrogen deposition level tolerance of T. sinensis seedlings and when the nitrogen level increases to a certain point, photosynthetic ability begins to decline.

Transpiration characteristics of different soybean varieties based on the Three-Temperature Model and thermal infrared remote sensing

LU Saihong, JIANG Shilian, WANG Tiao, ZHANG Tong, HOU Mengjie, TIAN Fei

2019, 27(10): 1553-1563. doi: 10.13930/j.cnki.cjea.190297

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Transpiration is an important process in the water cycle and is the key parameter to accurately quantify water use efficiency. Thus, it is of great importance for studying the relationship between the carbon and water cycles and for developing water-saving agricultural practices. The major objective of this study was to quantitatively study the transpiration rate of soybean plants of different varieties and under different water stress conditions, to identify differences in temporal and spatial characteristics, and finally, to provide a reference for the selection of drought-resistant and water-saving soybean varieties. Therefore, two soybean varieties (C08 and J21) were selected as the research objects and two water stress conditions (75%[A0] and 37.5%[A1] of the local empirical irrigation quota) were used for each variety. Based on the Three-Temperature Model (3T model) and using thermal infrared remote sensing, transpiration was quantified in the different soybean varieties under different water stress conditions. The diurnal variation in transpiration rate of the soybean plants under different water stress conditions was basically consistent with temperature, net solar radiation (R_n), and canopy temperature (T_c), showing a single-peak curve that first increased and then decreased, reaching a peak at value between 1.2 mm·h^-1 and 2.5 mm·h^-1 at noon. Moreover, the canopy temperature and transpiration rate of soybean plants under different treatments showed obvious spatial heterogeneity. Under different water stress conditions, C08 and J21 soybean varieties showed canopy temperatures in the order A0 < A1, with means of 6.55 K and 5.91 K, respectively. Transpiration rates were in the order of A0 > A1, with averages of 0.28 mm·h^-1 and 0.29 mm·h^-1, respectively. Transpiration rates were positively correlated with irrigation and negatively correlated with canopy temperature. Under the same water stress conditions, canopy temperatures were in the order of C08 < J21, with the mean canopy temperature of J21 1.83-2.47 K lower than that of C08. In addition, transpiration rates were of the order J21 < C08, with the mean transpiration rate of the J21 soybean variety 0.13-0.14 mm·h^-1 higher than that of the C08 soybean variety. Thus, the J21 soybean variety consumes more water than the C08 variety under the same conditions of water stress. In combination with crop growth indicators, such as leaf area index (LAI) and crop yield, these data provide an important reference for improving crop water productivity in the future. Compared with traditional methods, the method used in this study has some advantages. The 3T model requires fewer parameters which are easy to be measured through introducing the concept of reference soil. The high-resolution thermal infrared instrument used here can reach the millimeter scale and meets the accuracy requirements of crop transpiration rate measurement in the farmland microclimate environment. Therefore, crop transpiration estimation based on the 3T model and thermal infrared remote sensing technology is convenient and accurate and is of scientific significance in promoting efficient agricultural water use and selecting water-saving crop varieties.

Evaluation and analysis of fiber quality characteristics of different maturity cotton varieties

TANG Shurong, WEI Shoujun, GUO Ruilin, WEI Jingyan, MENG Junting, YANG Changqin

2019, 27(10): 1564-1577. doi: 10.13930/j.cnki.cjea.190130

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Fiber quality traits of different maturity cotton varieties were analyzed with Grey Multidimensional Comprehensive Assessment (GMCA). Data sets were collected from the cotton national regional trials from 2005 to 2014, including early-maturing, early-medium maturing, and medium maturing variety trials, in three cotton areas of China-the Northwest Inland Valley (NWIV), the Yellow River Valley (YeRV), and the Yangtze River Valley (YaRV). It is of great significance for establishing dominant cotton production areas and ascertains the distribution, ecological breeding, and quality improvement methods for all cotton varieties. Results showed that:1) there were 0.54% and 12.63% of all candidate varieties of medium maturity cotton divided into the high yield and good quality (type Ⅰ) and common quality (type Ⅱ) according to the national cotton fiber quality standards, respectively. The proportions of early-maturing cotton were 7.09% and 18.44%, and proportions of early-medium maturing cotton were 0.57% and 17.14%, respectively. 2) Fiber length and strength of the tested varieties was higher in grey correlation coefficient with those of ideal varieties characters, followed by spinning consistency index, again for micronaire. 3) By comparing fiber quality to ideal trait via grey relational analysis, we found that the fiber quality of medium maturing varieties in the YeRV were better than those of medium maturing varieties in the YaRV. The comprehensive characteristics of fiber quality of early-maturing cotton were the best in the NWIV, and followed by the medium maturing cotton in the YeRV and YaRV. 4) Medium-maturing varieties were mainly distributed in the YeRV and YaRV in China, though medium maturing cotton varieties had increased in the NWIV over the past 5 years. Overall, the range of fiber length for medium maturing varieties was 28.7-30.3 mm, which reached standards for high quality yarn. In recent years, there had been a downward trend on fiber length and strength of cotton varieties in the YeRV, with a strength range of 29.6-31.0 cN·tex^-1, at medium to upper level. Micronaire in three cotton areas with different maturity types exhibited significant difference; the micronaire of the YaRV was higher than that of the YeRV, and that of YeRV from medium maturing varieties was higher than that of the NWIV for early-medium maturing varieties. The micronaire in the YeRV had greatly improved from 2010 to 2014, where more than 6.0 micronaire had been observed. 5) This study showed that the accumulated temperature of above 10℃ was the primary factor affecting fiber quality of conventional and hybrid cotton of medium-maturing varieties. The order of meteorological factors affecting cotton fiber length and micronaire was accumulated temperature above 10℃, rainfall, and sunshine hours; however, that impacting strength and spinning consistency index was accumulate temperature above 10℃, sunshine hours, and rainfall.

Soil improving effect of Suaeda salsa on heavy coastal saline-alkaline land

YANG Ce, CHEN Huanyu, LI Jinsong, TIAN Yu, FENG Xiaohui, LIU Xiaojing, GUO Kai

2019, 27(10): 1578-1586. doi: 10.13930/j.cnki.cjea.190178

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Suaeda salsa is a pioneer species in community succession of coastal saline-alkali ecosystems, as well as an important plant for vegetation construction. In order to explore the soil improvement effect and mechanism of S. salsa on coastal saline-alkali land, the effects of S. salsa growth on soil structure, water infiltration and salt distribution were studied through soil investigation of a primary S. salsa community and indoor soil column planting experiment. Meanwhile, the effects of salt absorption by S. salsa and salt leaching by soil structure promoting were compared and evaluated. The results showed that:1) the growth of S. salsa had an obvious effect on improving the soil structure of coastal saline soil. In the field investigation, the soil bulk density in the 0-20 cm soil layer of S. salsa patch was significantly lower than that in the bare land patch, and the soil porosity was significantly higher than the bare land patch. In the soil column experiment, planting S. salsa reduced soil bulk density of each soil layer, with an average decrease of 6.16%, an increased soil porosity by 1.59%-5.15%. 2) The growth of S. salsa significantly promoted the soil water infiltration capability of coastal saline soil. Field infiltration test results showed that, in the same infiltration time, the cumulative infiltration, initial infiltration rate and stable infiltration rate of S. salsa patch were 3.6, 2.5 and 3.0 times of bare land patch, respectively. The results of soil column simulation tests showed that the initial infiltration rate of S. salsa treatment was 0.08 mm·min^-1, which was 2.6 times that of bare land treatment, and the stable infiltration rate was 0.03 mm·min^-1, which was 3 times that of bare land treatment. 3) The growth of S. salsa significantly reduced the soil salinity. After the harvest of S. salsa in the field investigation and soil column experiment, the soil salinity in the 0-40 cm soil layer in bare land treatment decreased by 2.67% and 12.98% respectively, while that of S. salsa treatment decreased by 12.08% and 49.28% respectively. In the field investigation and soil column experiment, 5.60% and 2.26% of the total desalination were due to harvesting S. salsa, however, leaching desalination accounted for 94.40% and 97.74% of total desalination, respectively. The above results show that planting S. salsa in coastal heavy saline-alkali land has an obvious effect on reducing soil salinity. Besides plant absorption, it also promoted soil salt leaching through improving soil structure and accelerating soil water infiltration.

Advances in research on the effects of micro-topography changes on surface hydrological processes

SI Mengke, CAO Jiansheng, YANG Hui

2019, 27(10): 1587-1595. doi: 10.13930/j.cnki.cjea.190505

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The surface water cycle is a key link in the soil-plant-atmosphere continuum (SPAC) system, and micro-topography plays an important role in the process of rainfall redistribution. Here, we summarized the influence of micro-topography changes on surface hydrological processes and discuss the effects of micro-topography on overland flow, rainfall-infiltration, evapotranspiration, soil water transport, and feedback in SPAC systems. Previous studies regarding the effect of micro-topographic changes on surface hydrological processes were summarized and our understanding of the influential effect of micro-topography changes on runoff, infiltration, and evapotranspiration was advanced in this paper. We aimed at addressing the problems that the classification of micro-topography was unsystematic and that recent studies lacked thorough research into the coupling between micro-topography changes and surface hydrological processes. We proposed that micro-topography types should be divided according to different ecological types and micro-topography construction methods, and at the same time, combined with data from micro-topographic surveying tools and remote sensing technology, to define the micro-topographic scale more accurately. On this basis, long-term field observations should be combined with short-term lab simulations to reveal the coupling mechanism between micro-topography changes and surface hydrological processes and to establish the quantitative relationship between them by creating model, and quantifying micro-topographic improvement measures to efficiently regulate the regional precipitation redistribution process. Ultimately, this paper may provide a theoretical basis for regional water resource regulation.

Research on spectral and texture feature selection for fruit tree extraction in the Taihu Lake Basin

YAO Xinhua, JIN Jia, XU Feifei, FENG Xianfeng, LUO Ming, BI Leilei, LU Zhou

2019, 27(10): 1596-1606. doi: 10.13930/j.cnki.cjea.180955

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Abstract:
The accurate acquisition of planting area and spatial distribution information is essential to monitor the growth and estimate the production of fruit trees (orchard). Remote sensing has been widely used in crop identification and monitoring in recent decades. Numerous classification algorithms have been developed based on various requirements for remote sensing data analysis. However, distinguishing fruit tree orchard and tea garden remains challenging, due to their similar spectral characteristics. Two GF-2 WFV (wide field of view) images, taken in summer and winter, were used to extract the spatial distribution of fruit trees in Jinting Town in the Taihu Lake Basin in this study. The normalized difference vegetation index (NDVI), normalized difference water index (NDWI), and texture features were used to construct a decision tree model. Vegetation and non-vegetation were quickly identified by analyzing the spectral curves of ground features in the study area. However, spectral characteristic was a poor parameter to differentiate fruit trees from tea trees. Since fruit trees and tea trees have distinct textural features, GF-2 images with rich texture information on ground objects can help distinguish fruit trees from tea trees. Thus, texture is one of the most important features in fruit tree extraction. In this study, the method of cumulative difference (Δf) was used to determine the optimal size of the texture window. Among the Δf values of each texture under 15 different window scales (3×3, 5×5, 7×7, 9×9, 11×11, 13×13, 15×15, 17×17, 19×19, 21×21, 23×23, 25×25, 27×27, 29×29, 31×31), the 15×15 window was determined as the optimum texture window. In addition, five texture features that were easy to distinguish from other objects were selected according to the cumulative difference of variables such as mean, variance, contrast, entropy, and correlation under the optimal texture window. The results showed that the decision tree model based on spectral index NDVI and NDWI, combined with texture features, effectively distinguished fruit trees from tea trees. The method of cumulative difference can quickly determine the best texture window size and texture combination. The extraction results showed that fruit trees were widely distributed in all locations of Jinting Town and that the planting area in the south was larger than that in the north. The local detail map indicated that the distribution of fruit trees was relatively neat and mainly in the plain area. The extraction accuracy of fruit trees in this study was 95.23%. The overall accuracy of the model in this study was 89.57% and the kappa coefficient was 89.00%. The producer accuracy and user accuracy were 90.00% and 87.30%, respectively. Using spectral indices combined with textural features achieved a higher overall accuracy than using spectral indices or textural features alone, with an overall accuracy increase of 10.65% and 12.04%, respectively. This method can be applied to the remote sensing extraction of fruit trees on a large scale and can provide an important reference in fruit tree extraction by using texture characteristics of sub-meter images. Moreover, the cumulative difference proposed in this study provides a new method for selecting the best texture window.

Distribution characteristics and impact factors of soil microbial biomass car-bon, nitrogen and phosphorus in western Sichuan plain

WU Xiaoling, ZHANG Shirong, PU Yulin, XU Xiaoxun, LI Yun

2019, 27(10): 1607-1616. doi: 10.13930/j.cnki.cjea.190328

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Abstract:
The characteristics of soil microbial biomass carbon (MBC), soil microbial biomass nitrogen (MBN), and soil microbial biomass phosphorus (MBP) contents, and their responses to climate, altitude, parent material and land use in the western Sichuan plain were investigated by regional survey and statistical analysis. The key influencing factors were subsequently revealed, which provided theoretical guidance for soil quality management in western Sichuan plain. Results showed that MBC, MBN and MBP were significantly higher in alluvial soil than in paddy soil, fluvo-aquic soil, and yellow earth (P < 0.05); moreover, MBC/MBN of fluvo-aquic soil was significantly higher than that of paddy soil. With respect to the influence of climate and elevation, MBC, MBN, and MBP exponentially declined with increasing accumulated temperature above 0℃, accumulated temperature above 10℃, mean annual temperature (MAT) and mean annual precipitation (MAP). However, they were augmented with increasing aridity and altitude. For different parent soil materials, the soil that developed from gray alluvial soil had higher MBC, MBN and MBP contents than those developed from glacial till. Meanwhile, they were significantly higher in the grassland than in paddy field and dry land. However, there were no significant differences between paddy field, dry land, and forest land. Pearson correlation and redundancy analyses revealed that the MBC and MBN had highly significant negative relationships with accumulated temperature above 0℃ and MAT, while, they had highly significant positive relationships with altitude (P < 0.01). In addition, MBP had a highly significant negative relationship with parent material. Furthermore, stepwise regression analysis showed that the main impact factors for MBC were MAT, MAP, and parent material, and aridity; MBN was affected by altitude, aridity, and MAP; MBP was primarily controlled by parent material, accumulated temperature above 10℃, and MAP. Therefore, soil MBC, MBN and MBP can sensitively reflect the climate change in different sampling points in western Sichuan plain, providing an essential basis for predicting the response of soil carbon, nitrogen, and phosphorus to climatic changes.

2019 Vol. 27, No. 10