Table of Content

20 July 2019, Volume 28 Issue 7

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Orginal Article

Potential distribution patterns of Stipa bungeana in China and the major factors influencing distribution

WANG Bai-zhu, ZHU Yuan-jun, LIU Yan-shu, MA Feng-yun, ZHANG Xiao, SHI Zhong-jie, YANG Xiao-hui

2019, 28(7):  3-13.  DOI: 10.11686/cyxb2018368

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Stipa bungeana is a dominant species of typical grassland in the north of China. In this study, we project its potential distribution patterns under current and future climate scenarios using the Maximum Entropy Model, and we identify the major factors influencing the distribution patterns. Initial testing of the model indicated results were reliable. In current climate scenarios, there were 5 highly suitable areas for S. bungeana: the Loess Plateau region, the Tai-Yimeng mountain region, the Hengduan mountains, the southern Tibet valley and the Tianshan mountain area. Under climate scenarios RCP 2.6 and RCP 8.5 (RCP denotes 'representative concentration pathway') in 2070, the highly suitable areas for S. bungeana would decreased. The results from a jackknife test showed that terrain roughness index, September precipitation, SAGA-GIS topographic wetness, February maximum temperature, December precipitation and December average temperature of December were major environmental variables affecting S. bungeana distribution patterns. These results provide a theoretical basis for the sustainable management of typical grassland in China under climate change.

Changes in soil physico-chemical properties and related fractal features during conversion of cropland into agroforestry and grassland: A case study of desertified steppe in Ningxia

CHANG Hai-tao, ZHAO Juan, LIU Jia-nan, LIU Ren-tao, LUO Ya-xi, ZHANG Jing

2019, 28(7):  14-25.  DOI: 10.11686/cyxb2018573

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Yanchi County of Ningxia lies in an agro-pasture transitional zone in northern China. The objectives of this study were to investigate the changes in soil properties and related fractal features associated with conversion of cropland to agroforestry or grassland. We selected four categories of site: cropland, cropland under conversion into grassland, cropland under conversion into agroforestry, and natural grassland; the latter taken as the control. The results showed: 1) Soil moisture content, soil pH and soil electrical conductivity values for both cropland under conversion into grassland and cropland under conversion into agroforestry differed from those in natural grassland. 2) After completing conversion of cropland into grassland, the soil nitrogen and organic carbon contents (0.60% and 5.93%, respectively) were the highest among the four sites studied. 3) Soil texture data for the site categories cropland, cropland under conversion into grassland, cropland under conversion into agroforestry, and natural grassland, respectively, were: clay and silt fraction, 10.87%, 7.47%, 8.73% and 6.53%; very fine sand fraction 39.07%, 35.20%, 38.87% and 31.00%; fine sand fraction, 29.73%, 34.93%, 32.80% and 36.73%; and the coarse sand fraction, 20.27%, 21.93%, 19.60% and 25.73%. Compared with natural grassland, the soil fractions in each particle size category differed significantly (P<0.05) at the cropland site under conversion into agroforestry, and there was also a significant difference (P<0.05) in the contents of very fine sand and coarse sand at the site under conversion from cropland into grassland. 4) The soil fractal dimensions of the four sites ranked from high to low: cropland (2.08)>cropland under conversion into agroforestry (2.01)>cropland under conversion into grassland (1.94)>natural grassland (1.87). 5) There was a positive (P<0.05) correlation between soil clay and silt and electrical conductivity, and a negative (P<0.01) correlation with C∶N ratio. There was a negative (P<0.01) correlation between soil fine sand content and soil pH. There was a negative (P<0.01) correlation with soil electrical conductivity, and a positive (P<0.01) correlation with C∶N ratio. There was a significant positive correlation between soil fractal dimension and soil electrical conductivity, and a negative correlation with C∶N ratio (P<0.01). There were no correlations between soil coarse sand, soil very fine sand and the various other soil data (P>0.05). 6) There was a linear negative correlation between the fractal dimension of soil particle size distribution and fine sand content (P<0.01), and a linear positive correlation with the content of very fine sand (P<0.01), and logarithmic correlation with the content of clay (P<0.01), but no correlation with coarse sand content (P>0.05). Overall, the data show that the conversion of cropland into agroforestry or grassland in the desert steppe region of Ningxia has a profound impact on soil physical and chemical properties, soil particle size distribution and fractal dimension properties. Compared with natural grassland, at the cropland site under conversion into grassland the levels of soil organic C and total N were significantly increased; while at the cropland site under conversion into agroforestry, the proportions of soil clay and fine sand, and the soil fractal dimension were significantly increased. These results show that the conversion of cropland into agroforestry or grassland is conducive to improvement of soil texture and ecosystem restoration in areas where there is soil degradation linked to over-cropping.

The elemental C∶N∶P stoichiometric characteristics and carbon storage of the herb layer under forest in Qinghai Province

CHENG Rui-xi, ZI Hong-biao, LUO Xue-ping, YANG You-fang, DAI Di, WANG Yan-li, SUOER Azhi, WANG Chang-ting

2019, 28(7):  26-37.  DOI: 10.11686/cyxb2018371

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The aim of this study was to clarify the elemental C∶N∶P stoichiometric ratios and carbon density distribution patterns of the herb layer under forest in ecosystems in China’s Qinghai Province. Forest surveys and laboratory analyses of samples collected were carried out in 2011. Determinations included elemental concentrations of C, N, and P, together with their stoichometric ratios, C∶N, C∶P, and N∶P, and C reserves (g·kg^-1) of the herb layers under seven dominant species (Betula platyphylla, Populus tomentosa, Betula albo-sinensis, Picea wilsonii, Populus davidiana, Sabina chinensis, Picea asperata). The results show: the aboveground carbon content [(419.9±1.44) g·kg^-1] of S. chinensis forest was significantly higher than that of other forest types, but the underground carbon content [(364.6±8.33) g·kg^-1] was significantly lower than that of other forest types; the nitrogen content of S. chinensis and P. asperata forests was significantly higher than that of other forest types. There was no significant difference in phosphorus content between different forest types. The C∶N and C∶P stoichiometric ratios of S. chinensis and P. asperata forests were significantly lower than other forest types, while the N∶P ratio was significantly higher than other forest types. In addition, the biomass and carbon density of S. chinensis forest underground herb layer, both aboveground and belowground were significantly higher than that of other forest types. Correlation analysis of the stoichiometric data for these seven dominant tree species in Qinghai Province showed that the carbon density of the herb layer was correlated with its stoichiometric characteristics, and the carbon density could be estimated based on the carbon content. Taking altitude as an environmental factor, it was found that the carbon density of the herb layer under S. chinensis and P. asperata forest was distributed at higher altitude, while other species were distributed at lower altitude. Therefore, understanding the ecological stoichiometric characteristics of nutrient elements for the above and below ground parts of the herb layer, as well as estimating the carbon reserves of the herb layer, is very important to understanding the nutrient status and biochemical cycling processes of forest ecosystems in Qinghai Province.

Effects of nitrogen addition on the soil microbial biomass C and microbial biomass N in degraded alpine grassland in Zoige County

WANG Li-na, LUO Jiu-fu, YANG Mei-xiang, ZHANG Li, LIU Xue-min, DENG Dong-zhou, ZHOU Jin-xing

2019, 28(7):  38-48.  DOI: 10.11686/cyxb2018429

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Alpine meadow is a fragile and vulnerable ecotone in northern Tibet, characterized by high altitude, low temperatures and limited precipitation. Low soil nitrogen availability in these meadows is a key factor limiting the productivity of the grassland. Increasing nitrogen deposition can change C and N cycling dynamics in this ecosystem. The research reported in this paper explored the impact of N addition on soil microbial biomass C and N for four grassland categories in the alpine meadow region of Zoige County: non-degradation grassland (NDG), light degradation grassland (LDG), moderate degradation grassland (MDG), and serious degradation grassland (SDG). In 2015 and 2016, urea was applied to plots during the return of green growth in spring, at rates of nitrogen concentrations 0, 5, 10 and 20 g·m^-2 (denoted CK, N₅, N₁₀ and N₂₀, respectively), in which the nitrogen concentrations of 5, 10 and 20 g·m^-2 were equivalent to urea application amounts of 10.78, 21.55, 43.10 g·m^-2. The results showed that soil microbial biomass C and N were sensitive to N addition but this response diminished with incrfeasing level of grassland degradation. N addition changed the relationship between soil microbial biomass C, microbial biomass N, and also other soil parameters, such as available phosphorus, nitrate nitrogen, total phosphorus, total nitrogen, total organic carbon, pH, and soil moisture content. Correlation of soil microbial biomass C or N with and other environmental factors was not significant, especially for the N₂₀ treatment. Grassland degradation and nitrogen addition can also greatly impact on the ratio of soil microbial biomass C and soil microbial biomass N (SMBC∶SMBN). For the CK treatment, SMBC∶SMBN was significantly higher in serious degradation grassland than in the other three grassland degradation categories. Under the N₅ and N₁₀ treatments, SMBC∶SMBN showed no significant difference between plots of the four degradation categories. However, in non-degradation grassland, the SMBC∶SMBN for the N₂₀ treatment was 33.7% higher than in the CK treatment. In contrast, in serious degradation grassland, SMBC∶SMBN decreased 62.5% for the N₂₀ treatment, compared to the CK treatment. The results indicate that the structure and composition of the soil microbial community is significantly changed following N fertilizer addition to the alpine meadow grassland.

Studies on the soil physical and chemical properties and enzyme activities of two fenced plant communities in desert steppe grassland

LI Guo-qi, ZHAO Pan-pan, SHAO Wen-shan, JIN Chang-qing

2019, 28(7):  49-59.  DOI: 10.11686/cyxb2018392

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Enclosure (fencing) is a fundamental part of China’s current ‘Grain for green’ program, and facilitates both the recovery of vegetation, and the improvement of soil properties. This paper, reports research into the recovery of soil physical and chemical properties and changes in activities of 4 soil enzymes after fencing in Agropyron mongolicum, and Sophora alopecuroides plant communities in the desert steppe of Ningxia province. Adopting the method of space as a substitute for time, the typical sites of two communities were selected and investigated in Yanchi County of Ningxia. The results showed that: 1) After fencing, soil water content, total N and total P increased significantly; while soil bulk density, pH, alkali hydrolysable N and available P contents were significantly reduced in the 0-10 cm soil layer of the A. mongolicum community studied. However, there were no significant differences in soil physical and chemical properties in the 10-40 cm soil depth. In the S. alopecuroides community soil bulk density decreased significantly, while soil water content, pH, organic carbon, total N, total P, available N and available P were significantly increased in the 5-10 cm soil depth. 2) After fencing, in the A. mongolicum community soil urease activity decreased significantly, while soil sucrase activity in the surface layer (0-10 cm) significantly increased, and the activity of catalase and phosphatase did not change significantly. In the S. alopecuroides community soil phosphatase activity decreased significantly, the activities of sucrase and urease were significantly increased, and the activity of catalase changed non-significantly. 3) There were different correlations in the two plant communities between soil enzyme activities and soil physical and chemical properties. In the S. alopecuroides community there was a significant positive correlation between soil sucrase activity, soil urease activity and soil nutrient content (P<0.01), while the activity of phosphatase showed a remarkably negative correlation. In A. mongolicum communities, there were significant positive correlations between urease activity and soil organic carbon, total P and available P content, and also, significant positive correlations between catalase activity and soil organic carbon, total N, and alkali hydrolysable N (P<0.05). In conclusion, although the water content and soil nutrient status of surface soil (0-10 cm) of the two communities were increased by fencing, no consistent changes in activities of the 4 soil enzymes studied were found.

Studies of the shade-tolerance of four ornamental grass and sedge cultivars

ZHANG Chao-cheng, JIANG Qian, WU Zhi, HE Xin-jie, JIANG Kai, GAO Jing-ya, LI Xiang, WANG Ning

2019, 28(7):  60-72.  DOI: 10.11686/cyxb2018375

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This study investigated the shade tolerance of four ornamental grass and sedge cultivars Festuca glauca, Calamagrostis epigeios, Carex lanceolata and Carex giraldiana under different shading treatments. Morphological indices, chlorophyll levels, chlorophyll a∶b ratio, soluble sugar, activity of superoxide dismutase (SOD) and peroxidase (POD) were determined under artificial shading treatments (CK, unshaded; T₁, 48.5% shade; T₂, 70% shade; T₃, 87% shade) to evaluate the resistance to the four ornamental grass and sedge cultivars to shading. With moderately increased shade, plant height, crown diameter, leaf length, chlorophyll content, SOD and POD activity were increased, but under more severe shade they were decreased, compared to CK plants. Chlorophyll a∶b ratio and soluble sugar content were significantly decreased by shading, compared to control plants. There were different patterns of change among the different parameters measured in the different cultivars. The increases in plant height, crown width, leaf length, chlorophyll content, SOD activity and POD activity of F. glauca and C. epigeios for T₁ were significantly higher than those of other treatments. By comparison, for the same parameters in C. giraldiana and C. lanceolata values were markedly higher in T₂ than in the other treatments. In this experiment, the four ornamental species tested responded to shading by etiolation responses, increased chlorophyll content, and SOD and POD activities and reduced chlorophyll a:b ratio. In addition, there were differences in the response mechanism and shade tolerance of the four ornamental grasses and sedges. C. giraldiana and C. lanceolata were shown to be tolerant of moderate shade with a shade intensity of 70%; while F. glauca and C. epigeios only tolerated endure a light shading environment with a shading degree of 48.5%. A subordinate function analysis indicated that the shade tolerance of four ornamental grasses and sedges ranked: C. lanceolata>C. giraldiana>C. epigeios>F. glauca.

Effects of planting density on the growth, yield and nutritional quality of alfalfa in central Inner Mongolia

MENG Kai, LI Xing-yue, JIA Zhen-yu, JIN Hui-qing, MI Fu-gui

2019, 28(7):  73-81.  DOI: 10.11686/cyxb2019053

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This study aimed to identify the optimal planting density for high yield and quality when growing alfalfa in central Inner Mongolia. In this study, alfalfa growth characteristics, forage yield and nutrient quality of the variety Caoyuan No. 3 were studied under four row spacing treatments (15, 30, 45 and 60 cm). The row spacing had a significant effect on the stem:leaf ratio (SLR), with SLR being lower under narrow raw spacing treatments (i.e. 15 and 30 cm row spacing treatments had significantly lower SLR than the 45 and 60 cm row spacings. The plant height and the fresh:dry ratio (FDR) increased with increased row spacing, while the forage yield decreased significantly with increased row spacing (i.e. yield was higher at 15 and 30 cm row spacings). The highest forage yields occurred in the second and third years and were 10813 kg drymatter (DM)·ha^-1 and 12574 kg DM·ha^-1, for the 30 and 15 cm row spacings, respectively. Planting density did not significantly affect crude fat and ash, but did significantly affect crude protein, acid detergent fiber, and neutral detergent fiber, as follows: crude protein was highest at 30 cm row spacing, neutral detergent fiber was lowest at the 15 cm row spacing, acid detergent fiber was lowest at the 45 cm row spacing, and the relative feed value was highest at the 15 cm row spacing. Considering all the forage yield and nutritional quality data, the recommended row spacing for alfalfa planting in the central region of Inner Mongolia is 15-30 cm.

Forage maize type and growth stage effects on biomass yield and silage quality

LI Ying-zheng, YAN Xu, WU Zi-zhou, YANG Chun-yan, LI Xiao-feng, HE Ru-yu, ZHANG Ping, EBENEZER Kofi Sam, ZHOU Yang, ZHANG Lei, RONG Ting-zhao, HE Jian-mei, TANG Qi-lin

2019, 28(7):  82-91.  DOI: 10.11686/cyxb2019070

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In this study, biomass yield and silage quality of three different varieties of forage maize (Zea mexicana, Yucao No.3 and Yucao No.6) were measured at the booting, tasseling and silking stage. Yields differed significantly, both between varieties and growth stages, but no variety by growth stage interaction was observed for yield. The fresh and dry matter (DM) yields of the three varieties were highest at the silking stage of crop development. Among the varieties, Yucao No.6 had significantly higher fresh and DM yield than Yucao No.3 and Z. mexicana. From the tasseling stage onward, the DM content of the varieties tested was greater than 20%, which meets the moisture requirement for silage making. The crude protein (CP) content ranged between 8.19% DM-12.80% DM and decreased gradually from the booting stage to the silking stage. Yucao No.6 had the highest CP content at every growth stage tested, while the CP difference between Yucao No.3 and Z. mexicana was not significant. Water soluble carbohydrate content was highest at the booting stage, and the content of acid detergent fiber and neutral detergent fiber increased progressively at successive crop development stages. The fermentation quality of silage differed significantly between maize varieties and growth stages, with a significant interaction between variety and growth stage. Silages from all the tested forage maize varieties, made in laboratory silos, had the lowest pH value (3.69) and the highest lactic acid content (7.00% DM) when harvested at the booting stage. Silage made at the booting stage performed better in fermentation analysis than silage made at tasseling or booting. Hence, the booting stage is recommended as the best stage for harvesting forage maize for silage production, where quality is required. With regard to variety differences in fermentation analysis, Yucao No.6 performed better than Yucao No.3 and Z. mexicana in almost all parameters studied. Based on the interaction between variety and growth stage for silage fermentation and nutrient composition, Yucao No.6 at booting stage was identified as best for silage due to its high forage fermentation quality and nutritional value compared to the two other varieties and their respective growth stages. However, Yucao No.3 and Z. mexicana were better for production of silage with good fermentation characterisitics, when harvested at the tasseling stage.

Effects of S₃₃₀₇ on physiology of chilling resistance in root and on yield of adzuki bean under low temperature stress during seedling stage

XIANG Hong-tao, LI Wan, HE Ning, WANG Xue-yang, ZHENG Dian-feng, WANG Tong-tong, LIANG Xiao-yan, TANG Xiao-dong, LI Yi-dan

2019, 28(7):  92-102.  DOI: 10.11686/cyxb2019052

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This study investigated the effect of a uniconazole (S₃₃₀₇) spray on cold resistance of adzuki bean in a pot experiment in an artificial climate chamber. Cold tolerant and cold sensitive cultivars Baoqinghong and Tianjinhong, respectively, were selected for study. Regulation of chilling injury and protection of the root system were key points of interest. A low temperature treatment (15 ℃) and spraying of S₃₃₀₇ (20 mg·L^-1) were imposed during plant establishment. The 15 ℃ low temperature treatment was applied for durations of 1, 2, 3, 4, or 5 days. Data collected for the two cultivars included root physical data and physiological indicators. Qualitatively, low temperature treatment increased soluble sugar and proline contents, enhanced superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) antioxidant enzyme activities and reduced malondialdehyde (MDA) content. However, the low temperature decreased adzuki bean yield. Quantitatively, soluble sugar and proline levels, and SOD, POD, and CAT activities after 3 days of low temperature exposure were increased for Baoqinghong and Tianjinhong cultivars by: 59.21% and 52.57%, 10.12% and 25.39%, 14.92% and 11.01%, 5.93% and 0.75%, and 53.33% and 13.33%, respectively, compared with regular temperature treatment. Meanwhile, values for the adzuki bean soluble protein contents after 5 days of low temperature exposure for the two cultivars were significantly increased, by 6.27% and 3.15%, respectively, and corresponding increases for MDA content were 45.41% and 51.08%. Yield decreases compared with controls were, respectively, 19.39% and 41.69% for Baoqinghong and Tianjinhon cultivars. By comparison, after 3 days low temperature exposure following spraying with S₃₃₀₇ soluble sugar, proline, SOD, POD and CAT parameters of Baoqinghong and Tianjinhong were increased by 22.01% and 0.46%, 8.55% and 1.40%, 13.45% and 24.06%, 23.60% and 15.95%, and 4.35% and 5.88%, respectively, compared with controls; while MDA yield after 5 days low temperature exposure was decreased by 9.05% and 4.37%, and yield was decreased by 23.06% and 43.88%. In conclusion, the chilling injury of adzuki bean was ameliorated by spraying of S₃₃₀₇ treatment and yield loss was decreased, which was linked to increased levels of soluble sugar and proline, increased activities SOD, PAD and CAT, and decreased the content of MDA.

Effects of different soil amendment measures on soil water relations, microbial community structure and yield in potato continuous cropping in dry land

XIE Kui-zhong, HU Xin-yuan, ZHANG Tong-tong, QIU Hui-zhen

2019, 28(7):  103-111.  DOI: 10.11686/cyxb2018397

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There is a practice of intensive, continuous cultivation of potato in Gansu province due to a high demand and good economic returns to growers. Under continuous cultivation, growers have experienced reduced tuber yield, reduced soil microbial community health, and an increased incidence of blight disease. To investigate ways to overcome these problems, an experiment was conducted on a potato field continuously cropped for 4 years, to assess the effect of different soil amendment measures on soil water relationships, microbial community structure and incidence of blight disease and tuber yield. The experiment was laid out in a randomized complete block design with three replicates. Five soil amendment treatments were tested: oxalazine, pentachloronitro benzene, Trichoderma harzianum, microbial soil amendment and conventional practice (control). It was found that T. harzianum and oxalazine treatments significantly increased the bacteria ratio. The oxalazine treatment had the lowest (P<0.05) incidence of early and late blight disease, and the highest water use efficiency, compared with other treatments. Economic yield of potatoes increased by 22.3% and 24.1% in T. harzianum and oxalazine treatments, respectively, when compared to the control. In summary, the use of the oxalazine and T. harzianum in a continuously cropped potato field improved soil microbial biomass, increased soil bacteria∶fungi ratio, reduced the incidence of blight, improved water use efficiency, increased soil water content, and improved the tuber yield of potatoes in dry land cultivation.

Effects on germination and seedling drought tolerance in white clover of seed soaking with mannose

ZENG Wei-hang, CHENG Bi-zhen, PENG Yan, LI Zhou

2019, 28(7):  112-122.  DOI: 10.11686/cyxb2018393

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The experiment studied germination and early development of white clover (Trifolium repens cv. ‘Ladino’) seeds subject to drought stress induced by 18% polyethylene glycol (PEG) 6000 solution. Effects on starch metabolism, root activity, osmotic adjustment, antioxidant defense, and gene differential expression, of seed soaking with mannose solution (MAS), were analyzed during the germination period. Different MAS concentrations were investigated including 0 (Control), 1.0, 2.0, 5.0 and 10.0 mmol·L^-1. Seed soaking with low concentration (0.5, 1.0, 2.0 and 5.0 mmol·L^-1) of MAS significantly increased seed germination under drought stress, with the 2.0 mmol·L^-1 MAS concentration having the most pronounced beneficial effects. However, higher MAS concentration (10.0 mmol·L^-1) significantly reduced seed germination under drought stress. Further experiments found that seeds soaked with 2.0 mmol·L^-1 MAS displayed significant increases in root growth, root activity, and amylase activities than seeds soaking with 0 mmol·L^-1 MAS during germination under drought stress. The MAS pretreatment effectively alleviated the stress-induced inhibition of amylolysis, significantly increased the accumulation of free proline, and resulted in a more negative seed osmotic potential during germination. As compared to Control seedlings, the total antioxidant capacity, activities of superoxide dismutase (SOD) and peroxidase (POD), and transcriptional levels of MnSOD and POD significantly increased in the seedlings with 2.0 mmol·L^-1 MAS treatment under drought stress. MAS treatment also resulted in significantly lower levels of reactive oxygen species, electrolyte leakage, and malondialdehyde in cells indicating lower oxidative damage. However, 2.0 mmol·L^-1 of MAS soaking pretreatment did not increase the soluble sugar content during seed germination under drought stress, which indicated that the more negative osmotic potential induced by MAS was mainly related to the accumulation of free proline. In summary, the MAS-promoted production of soluble sugars through accelerated amylolysis is potentially useful to maintain seedling growth under stress. These results indicate that MAS significantly improves drought tolerance of white clover seeds during germination and early development. This response is closely associated with promotion of starch breakdown, enhancement of osmotic adjustment, and improvement of antioxidant defense during seed germination. Seed soaking with a low concentration of MAS may also be useful to promote seed germination of white clover in conditions where water is more freely available.

Photochemical activity in flag leaves of winter wheat when following maize, peanut, or a maize-peanut intercrop in a crop rotation

WANG Fei, YIN Fei, LONG Hao-qiang, LI Xue, WU Yan-yan, JIAO Nian-yuan, MA Chao, FU Guo-zhan

2019, 28(7):  123-131.  DOI: 10.11686/cyxb2018813

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The aim of this research was to verify that photosynthetic activity of flag leaves and yield, in winter wheat, is enhanced when following a maize-peanut intercrop in a crop rotation. Winter wheat was sown into plots in a field experiment which had previously grown a maize-peanut intercrop (ICR), maize (MCR) or peanut (PCR), either without, or with phosphate fertilizer at 180 kg P₂O₅·ha^-1 (P₀ or P₁, respectively). Data gathered included: soil moisture content before wheat sowing, wheat flag leaf gas exchange parameters, and characteristics of photosystem Ⅱ (PSⅡ), photosystem Ⅰ (PSⅠ) and their interrelationships. Compared with MCR, ICR significantly (P<0.05) increased soil moisture content at wheat sowing, the net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), the performances of electron donor (W_k) and acceptor (V_j) sites of the electron transport chain in the PSⅡ reaction center in flag leaves of winter wheat; and enhanced the absorbed energy flux (ABS/CS_o), trapped energy flux (TR_o/CS_o), electron transport flux (ET_o/CS_o) per cross section (CS) in flag leaves of winter wheat. Compared to MCR, ICR significantly improved the maximum quantum yield of primary photochemistry (φ_po), energy conversion efficiency (Ψ_o), electron transfer efficiency (δ_Ro), PSⅠ performance (ΔI/I_o), coordination between PSⅡ and PSⅠ (Φ_PSⅠ/PSⅡ) in flag leaves, and the yield of winter wheat; and increased the φ_po and δ_Ro at the milk-stage of grain development, as compared to PCR. Supplying phosphate fertilizer increased the P_n, ABS/CS_o, TR_o/CS_o, ET_o/CS_o, φ_po, Ψ_o, δ_Ro, ΔI/I_o and Φ_PSⅠ/PSⅡ in flag leaves of winter wheat. The data indicate that intercropping peanut with maize in a crop rotation benefited the following crop in the rotation. In this experiment, following a maize-peanut intercrop, the activity of light reaction centers in flag leaves of winter wheat were enhanced, so the net photosynthetic rate was increased. Conservation of soil moisture during the maize-peanut intercrop phase of the rotation appears to be an important contributing factor in these results.

A study of the optimum sowing and burial dates of rice beans used as green manure after canola harvest in the Chongqing region

ZHANG Xue-feng, WANG Deng-ke, HUANG Lei, YAO Lu-hua, LI Yang, HE Zhi-bin, KANG Lin, GUO Yan-jun

2019, 28(7):  132-142.  DOI: 10.11686/cyxb2018427

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Rice bean (Phaseolus calcaratus) is an important summer green manure crop for improvement of soil quality. In the current study, rice bean was sown on three dates (May 2, May 7, and May 12) and was ploughed in soil on August 4, August 18 or September 2 in Chongqing, China (9 treatments; 3 replicates). Data collected included the above- and below-ground biomass, the plant nutrient contents at different growth stages, the decay rate of matter after burial using a nylon bag method, and levels of soil available nutrients (N, P, and K) after the rice bean was buried. With later sowing dates, the aboveground biomass was significantly decreased, while the root∶shoot ratio was reduced with earlier sowing, but tended to be increased with later sowing. Delayed sowing increased the rice bean plant total nitrogen (TN) content when compared with the control. Plant total potassium (TK) content was significantly reduced by delayed sowing date, whereas differences between sowing dates for total phosphorus (TP) showed no consistent pattern. Dry matter decay rate and plant nutrient levels showed similar trends for the different sowing dates. The values for residual dry matter in nylon bags, TN, TP, and TK were significantly higher than those of the control when the burial date was delayed 15 days in August. After the rice bean was buried, soil available N levels increased during the 21 days, whereas soil available K and P levels were variable. Because of the higher rice bean biomass and nutrient contents from earlier sowing, 10 days after canola harvest is the recommended sowing date for rice bean in Chongqing. The burial date should be in early August, when temperatures are still high enough for the buried plant material to decompose.

Effects of baling density and stacking method on chemical composition and mycotoxin levels of native hay

DU Shuai, LIU Hao, YOU Si-han, Gegentu, JIA Yu-shan

2019, 28(7):  143-150.  DOI: 10.11686/cyxb2018334

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The major constraint for forage storage is chemical composition and mycotoxin. To study the effects of baling density and stacking method on chemical composition and mycotoxin levels of native hay, a randomized split-plot experiment (2×3 factors) was carried out. Baling density as the primary factor and stacking method as the secondary factor was used. The primary factor was 160 and 120 kg·m^-3, the secondary factor was cross-stacking, vertical-stacking and transverse-stacking. Baling density was the main plot factor and sacking method was the subplot factor. For baling density, no significant differences were found for hay dry matter (DM), ash (Ash), neutral detergent fiber (NDF), aflatoxin B₁ (AFB₁), T-2 toxin (T-2) or ochratoxin A (OTA) (P>0.05). However, acid detergent fiber (ADF), crude protein (CP), deoxynivalenol (DON) and zearalenone (ZEN) did differ significantly with baling density (P<0.05). For stacking method, there were no significant differences in Ash, DM, ADF, NDF, CP, DON, AFB₁, T-2 and OTA (P>0.05). However, there was a significant difference between stacking methods for ZEN levels in the hay (P<0.05). In summary, baling density, and stacking method did significantly change hay chemical composition and mycotoxin levels. The optimal combination from this experiment in Xilinhot, was a baling density of 160 kg·m^-3 with cross-stacking of bales.

Effects of isobutyrate supplementation on growth performance, ruminal fermentation and cellulolytic bacterial abundance in calves

LIU Yong-jia, WANG Cong, LIU Qiang, GUO Gang, HUO Wen-jie, ZHANG Jing, PEI Cai-xia, ZHANG Yan-li

2019, 28(7):  151-158.  DOI: 10.11686/cyxb2018411

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This study evaluated the effects of isobutyrate (IB) supplementation on growth performance, ruminal fermentation, ruminal cellulolytic bacteria abundance and ruminal enzyme activities in pre- and post-weaned dairy calves. Thirty-six Chinese Holstein male calves were randomly allocated to four groups at 15 days of age. The treatments were control, low-IB (LIB), medium-IB (MIB) and high-IB (HIB) with 0, 3, 6 and 9 g isobutyrate per calf per day, respectively. At 60 days of age (weaning) and 90 days of age, body weight of calves was measured and ruminal fluid was collected for analysis. The results showed that dry matter intake, average daily gain and economic benefit were higher (P<0.05) for MIB and HIB than for control in pre- and post-weaned calves. Ruminal pH was lower (P<0.05) for HIB than for LIB and control in calves at 90 days of age. Ruminal total volatile fatty acids and acetate concentrations were higher (P<0.05) for MIB and HIB than for LIB and control. The ratio of acetate to propionate was higher (P<0.05) for MIB and HIB than for control in calves at 60 days of age, and was higher (P<0.05) for MIB and HIB than for control and LIB in calves at 90 days of age. Ruminal isobutyrate concentration was higher (P<0.05) for MIB and HIB than for control in calves at 60 and 90 days of age. At 60 days of age, activities of xylanase and α-amylase were higher (P<0.05) for MIB and HIB than for control, activities of cellobiase and pectinase as well as abundance of Butyrivibrio fibrisolvens, Ruminococcus albus and Fibrobacter succinogenes were higher (P<0.05) for MIB and HIB than for control and LIB. At 90 days of age, all the ruminal enzyme activities and cellulolytic bacterial abundance values were higher (P<0.05) for MIB and HIB than for control and LIB treatments. These results indicated that isobutyrate improved growth performance and ruminal fermentation through stimulation of ruminal cellulolytic bacterial growth and enzyme activity. There was no significant difference in measured prarmeters between MIB and HIB; thus, the optimum supplementary dose of isobutyrate was found to be 6 g per calf per day under the conditions of this experiment.

Analysis of insect resistance and herbicide resistance in transgenic alfalfa plants over-expressing the OvBAN/bar gene

DONG Wen-ke, Chen Chun-yan, MA Hui-ling

2019, 28(7):  159-167.  DOI: 10.11686/cyxb2019152

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The bifunctional OvBAN/bar gene was inserted into cell lines of the alfalfa cultivar ‘Gannong No.3’ using Agrobacterium-mediated transformation. PCR and southern blot analysis showed that four transgenic lines that contained the target gene were obtained, and all showed hybridization bands; two lines had single copies, one had two copies, and one had three copies. Expression of OvBAN in the four transgenic plants was analyzed by quantitative RT-PCR, and confirmed to be most highly expressed in the line with 3 copies, and also highly expressed in the two lines with two copies. In these transgenic alfalfa plants, anthocyanin reductase activity and condensed tannin content were significantly higher than in untransformed alfalfa. These three lines of transgenic alfalfa over-expressing the OvBAN/bar gene were tested for resistance to aphids, and the transgenic material demonstrated stronger aphid resistance than non-transgenic plants, with a 78%-93% reduction in aphid numbers per plant. Transgenic plants were then sprayed 0.5% glufosinate to test for herbicide resistance. After 10 days, the transgenic plants were still healthy, while the untransformed plants withered and eventually died, indicating that the bar gene had been integrated into the genome and stably expressed. In summary, the study indicated that introduction of the OvBAN/bar bifunctional genes significantly enhanced insect resistance and herbicide tolerance in transgenic alfalfa plants.

Module structures and the growth analysis of Achnatherum sibiricum clones in forest margin grassland in the Songnen Plain, China

SONG Yue-yuan, YANG Yun-fei

2019, 28(7):  168-174.  DOI: 10.11686/cyxb2018396

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Clusters of Achnatherum sibiricum clones (n=30) were randomly sampled from artificial grassland in forest margin sites on the Songnen Plain. Structures of the modules were analyzed and their characteristics quantified. In this way, scientific insight for the further study of the clonal plant growth strategy was obtained. It was found that there were on average (34.0±11.05) tillers per cluster, with significantly more vegetative tillers (83.3%) than reproductive tillers (16.7%). However, reproductive tillers were 9.6 times heavier than vegetative tillers and therefore the reproductive tillers were the dominant component (66.9%) of total biomass, which was (21.51±10.28) g·cluster^-1. Additionally, quantitative characteristics of the modules were highly variable. The trait with the largest coefficient of variation (76.4%) was the bud number on the reproductive tiller nodes, while the trait with the lowest coefficient of variation (27.6%) was cluster size. The vegetative reproductive capacity per vegetative tiller was significantly higher than that of reproductive tillers. Thus, a very significant (P<0.01) power allometry growth relationship was observed in A. sibiricum between cluster size, and module number and biomass, indicating a complementary and expansive strategy both within the cluster and with respect to its spatial expansion.

Effects of different light intensities on morphogenesis and ultrastructure of Gibasis pellucida leaf

CHEN Bin, LI Hong-yao, LIU Xiao-wei, XIA Bin, SUN Shao-wen, SUN Ying, HE Miao

2019, 28(7):  175-185.  DOI: 10.11686/cyxb2019174

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In this research, ramets of Gibasis pellucida propagated from stem cuttings were used as experimental material to explore the morphological and ultrastructural changes in leaves, when grown at different light levels. Shading net was used to create a series of five light environments with 0, 25%, 50%, 75% and 95% shading, respectively. The results indicated that: with reducing light level from 0 to 75% shading, leaf length, width and area progressively increased to a maximum for the experimental material at 75% shading. Along with change in leaf size, the colors of the leaf upper surface changed from yellow-green to dark-green, and that of the leaf lower surface changed from deep-purple to light-purple. When the shading intensity was 95%, the purple color disappeared. Leaf chorophyll a, chlorophyll b, and chlorophyll (a+b) contents were negatively correlated with light intensity (P<0.05), while leaf anthocyanin content was positively correlated with light intensity. The thickness of leaves and their upper epidermis, lower epidermis, palisade tissue and spongy mesophyll tissue decreased significantly with decreasing light intensity (P<0.05), while the ratio of palisade:spongy mesophyll thickness, and tightness of tissue were highest in the 50% shade treatment. The 0 and 25% shade treatments slightly damaged the ultrastructure of mesophyll cells, causing the expansion of some thylakoid grana and stroma, and enlargement of starch grains. Extremely low-light intensity (95% shading) resulted in serious disruption to the ultrastructure of mesophyll cells, together with some chloroplast disintegration and emptying of starch grains. In summary, G. pellucida possesses a very strong shade adaptation response, and mechanisms used to adapt to the different light environments involved adjusting the shape, pigmentation and anatomical structure of leaves. While G. pellucida could survive in the extremely low light environment of the 95% shade treatment, the structure of the leaf internal organs was damaged irreversibly by this degree of shading.

Research progress on yak grazing behavior and its influence on the soil properties of alpine grassland

DU Zi-yin, CAI Yan-jiang, WANG Xiao-dan, ZHANG Bin

2019, 28(7):  186-197.  DOI: 10.11686/cyxb2018372

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Yak grazing is an important means of utilization of natural grassland in alpine ecosystems, and the herbage consumption, soil treading, and dung and urine excretion during grazing inevitably generate direct or indirect influences on grassland ecosystems. This paper reviews the basic characteristics of the 3 main impacts of grazing, foraging, trampling, and dung and urine deposition. Using this framework, research results relating to the behavioral ecology of grazing yaks are summarized and analyzed, and the influences and functional mechanisms of the animal behavioral processes on soil physicochemical and biological properties are explored. Through this approach, the impacts of grazing on soil carbon (C) and nitrogen (N) status, vegetation biomass and microbial communities in the alpine grassland were clarified. Results showed that foraging, trampling and excretion of dung and urine are important components of grassland C and N cycling and energy conversion. Forage nutrients not digested and utilized by grazing animals are returned to the soil as dung and urine, and this nutrient return is an important source of fertilization in the fragile natural grassland, and ensures the maintenance of soil nutrient balance and vegetation productivity. Compared to the influence of foraging behavior and excreta return, treading impacts emerge more slowly, but have a more permanent effect. Therefore, it is important to systematically elucidate the separate effects of herbage consumption, treading, and dung and urine deposition on the soil physical structure, nutrient dynamics, and herbage accumulation rate, in order to gain a comprehensive theoretical understanding the functional processes and mechanisms of yak grazing and how they influence the alpine grassland nutrient biogeochemical cycling in soil-vegetation systems. Such understanding could be helpful for providing scientific guidance for optimizing yak grazing patterns, maintaining the sustainable development of fragile ecosystems, and enhancing the construction of national ecological security safeguards on the Qinghai-Tibetan Plateau.

Ecological adaptability of biological traits and population distribution patterns for the ephemeral plant Leontice incerta in desert habitats

SUN Hai-rong, CHE Zhao-bi, CHEN Yi-shi, LU Wei-hua, WANG Shu-lin, LI Na-na, XIN Huai-lu

2019, 28(7):  198-207.  DOI: 10.11686/cyxb2018376

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This study aimed to document the ecological adaptability of biological traits and the population distribution pattern of the ephemeral desert plant Leontice incerta in the northern Xinjiang region. Data gathered included biological characteristics, seed production traits, dispersal mechanisms and population distribution patterns in the natural habitat. L. incerta has membranous fruits that form bladders around the seeds and are dispersed by wind rolling, and a swollen irregular underground tuber. Flowers of L. incerta temporarily close in response to cool overnight temperatures in their desert environment. The number of fruits per plant was, on average, 8.29. Fruit have reticulate venation at the sides and base, with the bottom veins thicker and not easy broken, and the apex of the fruit is without veins and thin and paper-like with blue-purple spots. This fruit apex is easily punctured when the fruit matures. Each fruit on average had 2.82 spherical seeds. Long-distance dispersal is achieved through release of seeds from the fruits as they roll in the wind. Average plant height was 18.9 cm, and average tuber diameter was 3.5 cm, but tuber size increased with plant age. To understand seed dispersal characteristics in this species, laboratory simulation studies of capsule movement with variables capsule size, air speed, and surface roughness were carried out, and plant and seedling distribution in the field was studied and analyzed. In the laboratory study, the distance travelled by capsules increased with increasing capsule size and decreased with increasing surface roughness. Seeds were released as capsules travelled, so that total seeds dispersed per capsule increased with distance, while seeds dispersed per unit area of ground decreased with increasing distance. Increased surface roughness increased capsule puncture and seed release from capsules. In the field, correlation between position of adult plants and position of seedlings increased up to 18 m distance from the adult plant and decreased at greater distances, while plant distribution was uniform on a 0-2 m scale, aggregated on a 2.5-14.0 m scale, and random on sampling scales greater than 14 m.