Table of Content

20 July 2016, Volume 25 Issue 7

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Orignal Article

Scaling-up methodology for alpine grassland coverage monitoring based on Landsat 8 OLI and MODIS remote sensing data: A case study in XiaheSangke grassla

MENG Bao-Ping, CUI Xia, YANG Shu-Xia, GAO Jin-Long, HU Yuan-Ning, CHEN Si-Yu, LIANG Tian-Gang

2016, 25(7):  1-12.  DOI: 10.11686/cyxb2015433

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This research used remote sensing data of MODIS and Landsat 8 OLI, combined with ground observations during 2013 and 2014 in XiaheSangke grassland, Gansu Province. Both individual bands and combinations of bands of Landsat 8 OLI were tested, with a view to selecting band combinations sensitive to grassland coverage. Then, grassland coverage inversion models were established based on MODIS vegetation index data. At the same time, the spatial scale effect was analyzed with a 30 m resolution and up-scaled to 250 m resolution for spectral reflectance, vegetation index, and estimated grassland coverage. It was found that: 1) the ratio of Band7/Band5 of the OLI data was the most sensitive combination for detecting grassland coverage, and the best grassland coverage inversion model was the linear function: y_oli=-270.064x_oli+115.987, R²=0.833, P<0.001; 2) The best grassland coverage inversion model was the logarithmic model (y=64.160ln(x_MEVI)+136.927, R²=0.795, P<0.001), which was established by using MODIS MEVI and up-scaling ratio index of OLI. The coefficient of fit was higher than for the models based on MODIS MEVI and Agricultural Digital Camera pictures (R²=0.706), and its average absolute error and average relative error were lower. 3) The accuracy of the logarithmic model (R²=0.795) based on MODIS MEVI and up-scaling grassland coverage using a ratio index (Band7/Band5) of OLI was higher than other models.

Regional-scale ecological stoichiometric characteristics and spatial distribution patterns of key elements in surface soils in the Junggar desert, Chin

TAO Ye, LIU Yao-Bin, WU Gan-Lin, ZHANG Yuan-Ming

2016, 25(7):  13-23.  DOI: 10.11686/cyxb2016009

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Ecological stoichiometry focuses on the element equilibrium and coupling relations, and it has been widely used in study of plant growth, limiting element determination, and ecosystem stability, among others. Desert ecosystems are an important component of terrestrial ecosystems, and are characterized by low precipitation, poor soil development and low floral and faunal biodiversity. Study of the ecological stoichiometry of desert soils enhances understanding of the nutrient supply capability and its effect on biodiversity and ecosystem stability. In this study, surface soil samples (0-10 cm) and environmental factors (including climate and geographical factors) in 79 sites in the Junggar desert were investigated, and then the stoichiometric characteristics of soil organic carbon (C), total nitrogen (N), total phosphorus (P) contents, their distribution patterns and factors influencing them were systematically studied using one-way ANOVA, a Kriging technique and correlation analysis. Soil C, N and P contents were (5.73±0.49), (0.207±0.009) and (0.347±0.004) g/kg respectively; and the soil C∶N, C∶P, and N∶P ratios were (29.92±2.55), (15.97±1.23) and (0.498±0.024) respectively. Soil P showed the highest stability (CV=0.098), whereas C, C∶N and C∶P exhibited relatively strong variability (CV=0.687-0.758). Soil C, P, C∶N and C∶P varied among different habitats (sandy desert, Gobi desert and saline-alkali desert) and different communities (Haloxylon ammodendron, H. persicum and small shrubs). Compared with national and global averages, the soil C, N and P contents, and C∶P and N∶P ratios in the Junggar desert were lower, but the C∶N was higher. The degree of deficiency of soil nutrient elements ranked in order: N>C>P. The soil nutrients and their stoichiometric ratios typically exhibited quadratic relationships with other nutrients, and the stoichiometric ratios were dominated by C and N. At a regional scale, all stoichiometric traits displayed obvious spatial heterogeneity. Soil C, and C∶N and C∶P ratios showed similar distribution patterns and were influenced by mean annual precipitation, latitude and longitude. Soil N and N∶P ratio displayed similar distribution patterns and were influenced by longitude, elevation and mean annual temperature.

Soil nitrogen characteristics of grassland on sandy soil undergoing vegetation restoratio

PU Qin, HU Yu-Fu, JIANG Shuang-Long, HE Jian-Feng, SHU Xiang-Yang, YANG Ze-Peng

2016, 25(7):  24-33.  DOI: 10.11686/cyxb2015571

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Grassland desertification is one of the most serious ecological and environmental problems in our country. To investigate changes in soil nitrogen under different vegetation restoration measures in desertified grasslands, the soil nitrogen content under 4 vegetation restoration measures in a semi-humid alpine region in northwest Sichuan were measured to elucidate the characteristics of soil total nitrogen and components in 0-60 cm soil layer during ecological restoration. After three years’ restoration; fencing with mixed sowing of oat and grasses, fencing with sowing of grasses and natural recovery after fencing, all restoration procedures increased vegetation cover and improved soil physical properties, particularly fencing and sowing oat and grasses. Increasing soil N content appeared as microbial biomass N>N{Invalid MML}-N>N{Invalid MML}-N>available N>total N. Compared with the severely desertified grassland, vegetation cover after fencing and sowing with oat and grasses increased to 74.1%, soil bulk density decreased to 1.39 g/cm³, while surface temperature at noon in summer decreased from 41.5 ℃ to 23.0 ℃. The total N content, available N, N{Invalid MML}-N, N{Invalid MML}-N and microbial biomass N in oat quadrats increased by 255.8%, 270.3%, 299.5%, 357.8% and 745.9% respectively. Soil particle composition and bulk density were significantly correlated with soil total nitrogen and N components in desertified grassland. We concluded that sowing oat with grass is an effective strategy for repairing desertified grasslands. Oats play the role of a pioneer species because of its drought resistance, tolerance of low fertility and strong tillering, promoting the growth of grass.

Assessment of forest soil fertility using an integrated index based on the Nemerow meth

DENG Xiao-Jun, CHEN Xiao-Long, TANG Jian, WANG Hui-Li, HAN Hua, XU Yong-Teng, HE Wen-Ping

2016, 25(7):  34-41.  DOI: 10.11686/cyxb2015435

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This study evaluated soil fertility in a forest utilized for timer production in Daguishan State Forest Farm using the Nemerow method. Soil pH, organic matter, total N, P and K, available N, P, K, Cu, Zn, B and Fe were selected as indicators. The coefficients of variation of these indicators ranged between 5.02%-65.69%. Organic matter content of the studied soil was moderately low with an average of 28.75 g/kg. Similarly, total N and available N were moderate or moderately high with averages of 1.64 g/kg and 135.5 mg/kg, respectively. However, P was very low with an average P₂O₅ content of 0.82 g/kg and an average available P content of 1.5 mg/kg. Average K₂O and available K contents were 23.76 g/kg and 51.8 mg/kg, respectively, moderately low. Soil fertility of the forest could be considered as “nitrogen rich, low phosphorus and moderate potassium”. Trace elements were also variable; available Zn and Fe were 2.03 mg/kg and 32.11 mg/kg, respectively, suggesting moderate levels while available B and Cu were 0.18 mg/kg and 0.41 mg/kg, respectively, indicating low or very low levels. The integrated soil fertility index of Daguishan forest was 0.85. The fertility indices of eucalyptus and pine forests were 0.77 and 0.82, respectively, equivalent to grade Ⅲ, while fir forest had a fertility index of 0.90, equivalent to grade Ⅱ. It was found that soil fertility of the study area was mainly limited by available P, B and Cu.

Simulation and analysis of soil water retention curves within and between hedgerows in Northern China farm system

HE Xiu-Dao, DANG Hong-Zhong, WANG Li, ZHOU Ze-Fu, LV Wen-Qiang

2016, 25(7):  42-51.  DOI: 10.11686/cyxb2015299

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This study aimed to simulate soil water retention curves within and between hedgerows of farm systems in northern China by the Van Genuchten model. Typical hedgerow systems in regions of sandy, loess and black soils were selected for study. The soil texture, soil porosity, soil organic matter and soil water-stable aggregates within and between hedgerows were measured. It was found that the soil porosity, soil organic matter and soil water-stable aggregates within hedgerows in sandy and black soil areas were higher than those from between hedgerows; but this result was adverse in loess area. The soil moisture content within hedgerows was higher than that between hedgerows. The soil water holding capacities within and between hedgerows were lowest in sandy soils and highest in black soils. It was concluded that hedgerows can improve soil texture, structure and soil water retention, and make an important contribution to control of sheet erosion on sloping land.

Spatio-temporal trends for fine root biomass of alpine Rhododendron thymifolium and their significance for ecological adaptation in Qilian Mountain

CAO Wen-Xia, LI Wen

2016, 25(7):  52-61.  DOI: 10.11686/cyxb2015323

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Rhododendron thymifolium is a dominant species in alpine azalea shrub land in Eastern Qilian Mountains. The horizontal and vertical distribution of root biomass for R. thymifolium and of other associated plant species were measured under the shrub canopy and in the gaps between plants of R. thymifolium, and seasonal trends were monitored. Coarse and fine-root biomass, and other species root biomass decreased with increasing soil depth. For R. thymifolium, 90% of fine root biomass was located in the 0-20 cm soil layer, and root biomass under the shrub canopy was greater than that in the between-plant gaps. The fine-root biomass of R. thymifolium was less during the germination period and pre-dormancy periods; the fine roots grew rapidly from June, and reached peak values in July. Peak values always occurred earlier in the surface layer than in the deep layer, and roots in gap areas appeared earlier than those in the shrub canopy area. Gaps between shrubs were regions of active fine root growth. Root biomass of other species began to decline from the sprout period, and was low in July, then reached a maximum at the end of the growing season. The annual average dead root biomass was greater than live root biomass, the dead∶live root biomass ratio increased with soil depth.

Cloning and expression analysis of a U-box gene of E3 ubiquitin ligase from Medicago truncatula

SHAO Lin-Hui, ZHENG Xing-Wei, LI Cong

2016, 25(7):  62-72.  DOI: 10.11686/cyxb2016073

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The E3 ubiquitin ligase is essential for the specific recognition of target proteins of ubiquitin, and therefore, it plays an important role in plant growth and development. The U-box family of E3 ubiquitin ligases function in regulating plant immune responses and stress resistance. To the best of our knowledge, there have been no reports on U-box family genes in Medicago truncatula. In this study, a U-box gene (MtPUB4), consisting of a 2448-bp cDNA encoding a putative protein of 815 amino acids, was cloned from M. truncatula. A sequence alignment analysis revealed that the MtPUB4 protein contains a U-box domain (C-X2-H-X7-C-X7-C-X2-C-H-X2-H) and two ARM (Armadillo) regions. Therefore, it was classified as a U-box/ARM E3 ubiquitin-ligase. We constructed a prokaryotic expression vector (pET-MtPUB4), and an SDS-PAGE analysis confirmed that the MtPUB4 protein was successfully expressed in prokaryotic cells. Real-time polymerase chain reaction analyses showed that the transcript levels of MtPUB4 were higher in flowers and lower in roots. Abiotic stresses such as NaCl, polyethylene glycol, and abscisic acid resulted in increased transcript levels of MtPUB4, with higher transcript levels after longer induction times. The transcript levels of MtPUB4 decreased slightly under low-temperature stress. These results indicated that MtPUB4 may be involved in regulating growth, development, and stress resistance in M. truncatula. The construction of the pBI121-MtPUB4 vector has laid the foundation for transformation of Arabidopsis in future studies.

Deep-sowing tolerance and genetic diversity of maize inbred line

PENG Yun-Ling, ZHAO Xiao-Qiang, YAN Hui-Ping, WU Jin-Huan

2016, 25(7):  73-86.  DOI: 10.11686/cyxb2015277

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The aim of this study was to establish accurate indices to identify and evaluate the deep-sowing tolerance of a range of inbred lines from the maize germplasm. Maize seeds were planted at three depths (3, 15, and 20 cm) and the following phenotypic traits were evaluated: emergence rate (RAT), mesocotyl length (MES), coleoptile length (COL), mesocotyl and coleoptile total length (MES+COL), seedling length (SDL), and root length (RL). At the same time, simple sequence repeat (SSR) markers were used to evaluate the genetic diversity among 51 maize inbred lines. The results showed that as the sowing depth increased from 3 to 15 or 20 cm, the RAT gradually decreased, SDL and RL first increased and then decreased, and MES, COL, and MES+COL increased. There were strong and significant differences in RAT, MES, COL, MES+COL, SDL, and RL among the maize inbred lines. Five traits (RAT, COL, MES, MES+COL, SDL) were significantly affected by sowing depth and by the interaction between genotype and sowing depth. Root length differed significantly depending on sowing depth, but it was not affected by the interaction between genotype and sowing depth. There were strong and significant positive correlations between RAT at 15- and 20-cm sowing depths and MES, COL, MES+COL, SDL, and RL. Six highly deep-sowing tolerant inbred lines and 11 moderately deep-sowing tolerant inbred lines were identified by the membership function method based on their performance when sown at 15 and 20 cm depths. Seventy SSR markers produced 222 alleles with an average of 3.17 alleles per marker. The polymorphism information content for each marker ranged from 0.265 to 0.801 with an average 0.579. The 51 maize inbred lines were divided into two major groups and six sub-groups in a genetic diversity analysis. Relatively high membership values for RAT, MES, COL, MES+COL, SDL, and RL were obtained for the Sipingtou (SPT), Lancaster (Lan), and Luda Red Cob (LRC) lines, which were highly or moderately tolerant to deep sowing. These results showed that maize lines tolerant to deep sowing can be screened by planting seeds at 15 and 20 cm depths, and that RAT, MES, COL, MES+COL, SDL, and RL are important indices to identify deep-sowing tolerance in maize. We conclude that deep-sowing tolerance can be objectively and accurately evaluated by the membership function method in maize inbred lines, and that SPT, Lan, and LRC are important deep-sowing tolerant germplasm groups.

Bioremediation of petroleum contaminated soil by plants and arbuscular mycorrhizal fungi in Northern Shaanx

SHAN Bao-Qin, QU Meng-Meng, LI Jiao, LI Chao

2016, 25(7):  87-94.  DOI: 10.11686/cyxb2015446

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A new bioremediation technique utilizing the symbiotic function between host plant and arbuscular mycorrhizal fungi (AMF) for petroleum contaminated soil was investigated in Northern Shaanxi in 2015. Four species of native plants in Northern Shaanxi studied were Artemisia annu, Artemisia argyi, Caragana korshinskii and Astragalus adsurgens, and AMF species were isolated from the rhizosphere of each species and used to inoculate field grown plants in contaminated soil to test effects of AMF on the degradation of petroleum hydrocarbon in soil and to select the best plant-AMF match. It was found that AMF spore densities were highest in soil with 0-5000 mg petroleum/kg soil, and significantly decreased with increasing petroleum concentration. AMF hyphal densities were higher in petroleum contaminated soil than in uncontaminated soil. The inoculation with AMF increased spore density and the percentage of AM colonization. Plant height and dry weight were decreased with increasing petroleum concentration, but both were significantly promoted by AMF inoculation AMF, with plant height increased by 16.77% and dry weight by 22.56%. Degradation efficiency of petroleum hydrocarbon in soil was enhanced by AMF inoculation, and was 15.35% higher than that of uninoculated soil. Among the plant-AMF combinations, Caragana korshinskii and Glomus geosporum was the best for petroleum degradation, and the degradation rate was 73.81% after 2 months. After inoculation with the selected AMF species, degradation rates of petroleum hydrocarbon and petroleum concentration in soil showed an obvious negative correlation, but degradation rates were significantly positively correlated with spore density, plant height and plant dry weight.

Effects of plateau zokor burrowing activity on soil nutrient spatial heterogeneity in alpine grassland

BAO Gen-Sheng, WANG Hong-Sheng, WANG Yu-Qin, ZENG Hui, MA Ge-Liang, LUO Zang-Ang-Mao

2016, 25(7):  95-104.  DOI: 10.11686/cyxb2015560

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Burrowing activity of Myospalax baileyi influences nutrient cycling, soil texture and soil microbial activity of grasslands, and has an effect on the spatial heterogeneity of soil nutrients. However, there is limited information about the soil nutrient distribution vertically within or across the sloping surface of the coniform-shaped mounds formed due to the burrowing activity of Myospalax baileyi. In this experiment, mounds of differing age (1 year, 3 years and 5 years old) were selected for study in an alpine grassland located in Qinghai Province. Samples were collected from 0-10, 10-20 and 20-30 cm soil depth at the summit of each mound, and for 0-10 cm soil depth at 10 cm intervals across the sloping surface from summit to base. Samples for 0-10 cm soil depth were also collected 10 cm away from the base of the mounds (controls). Soil nutrient contents, including total nitrogen (TN), available nitrogen (AN), total phosphorus (TP), available phosphorus (AP) and organic matter (OM), were determined for all samples. In younger mounds soil nutrient status differed little with vertical depth below the summit of the mound, but in 5-year-old mounds and especially for control samples collected 10 cm from mounds, soil nutrient levels were high in the surface layer and low in the 20-30 cm layer compared to the younger mounds. Soil nutrient levels generally increased from summit to base in the surface layer of younger mounds, and were higher still at 10 cm distance from mound bases. However, 5-year-old mounds generally had higher soil nutrient levels at the summit and lower levels at the base than younger mounds, and therefore exhibited an opposite trend of decreasing nutrient levels from summit to base. This research further confirmed the existence of soil nutrient spatial heterogeneity caused by the burrowing activity of Myospalax baileyi, and also showed that mounds of differing age differ in their soil nutrient spatial heterogeneities. The results of this study will aid understanding of the plant diversity, cover and species distribution patterns in the grasslands.

Effects of grazing duration on polyunsaturated fatty acid deposition and oxidative stability of lamb meat

JIN Yan-Mei, ZHANG Xiao-Qing, WANG Chong, LI Mei, WANG Yi, YAN Qin

2016, 25(7):  104-111.  DOI: 10.11686/cyxb2015448

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The aim of this research was to investigate the effects of the grazing duration on polyunsaturated fatty acids (PUFA) deposition and oxidative stability of lamb meat. Forty castrated male Ujumuqin lambs were randomly assigned to five groups with similar liveweight and age, and then subjected to the following treatments: (i) no grazing (0H, control), (ii) 2 h grazing (2H), (iii) 4 h grazing (4H), (iv) 8 h grazing (8H), and (v) 12 h grazing (12H). Each day, the lambs began to graze at 6:00, and stopped grazing at 8:00, 10:00, 14:00 and 18:00, respectively. The lambs were raised for 102 days, comprising a 15-d feed adaptation period and an 87-d experimental period. Six lambs with similar liveweight from each group were slaughtered at the end of experiment. The longissimus dorsi muscles were sampled from each lamb to measure PUFA contents and antioxidant properties. The results showed that the grazing time significantly affected antioxidant parameters. The meat of lambs fed concentrate in stalls had a higher (P<0.001) malondialdehyde (MDA) content than those in the meat of lambs grazed for 2-, 4-, 8- and 12-h, but there was no significant difference in meat MDA content among the lambs in the four grazing treatments. The meat of lambs grazed for 4-12 h had significantly higher (P<0.001) superoxide dismutase (SOD) activity, but significantly lower peroxidase (GSH-Px) activity (P=0.020) than those in the meat of lambs exclusively fed in pens. There was no significant difference in the total antioxidant capacity (T-AOC) among the five groups. The MDA content and SOD activity showed quadratic curve relationships with grazing time. The MDA content decreased up to 10-h of grazing time, and increased after that. In contrast, SOD activity increased up to 10-h of grazing time, and then decreased. The GSH-Px activity was negatively related to grazing time. The groups grazed for 4-h and 12-h had significantly higher PUFA and peroxidizable fatty acids (HP-PUFA) contents in the meat, compared with the 2-h and 0-h grazing groups (P<0.01). There were multiple linear relationships between antioxidant activity and PUFA (R²=0.586, P<0.001) and HP-PUFA (R²=0.602, P<0.001) contents. In conclusion, the meat of lambs grazed for 2-10 h showed better oxidative stability as a result of compounds that counteract oxidative reactions. This has important consequences for extending the shelf-life of lamb meat.

Effects of additives on fermentation quality and aerobic stability of total mixedration silage containing wet brewers’grains in Tibe

DING Liang, YUAN Xian-Jun, WEN Ai-You, WANG Jian, GUO Gang, LI Jun-Feng, WANG Si-Ran, BAI Xi, SHAO Tao

2016, 25(7):  112-120.  DOI: 10.11686/cyxb2015427

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The aim of this study was to evaluate the effects of Lactobacillus buchneri (LB) and sodium diacetate (SDA) on the fermentation quality and aerobic stability of total mixedration (TMR) silage containing wet brewers’grains in Tibet. The treatments were as follows: control (no additives), LB (at 10⁶ colony forming units/g fresh forage) and SDA (at 0.5% of fresh weight). All silos were opened after 70 days of ensiling, and a portion of silage was collected to analyze fermentation quality, and the chemical and microbial composition. A multi-channel temperature recorder was used to record the change in the temperature of the remaining silage during exposure to air, and the aerobic stability of silage samples was estimated after 6, 9 and 14 days of exposure to air. The results showed that all of the silages had good fermentation quality with high lactic acid contents, low ammonia/total nitrogen ratios, and low butyric acid contents. The addition of SDA increased the lactic acid content (P>0.05) and the dry matter recovery (P<0.05), and significantly (P<0.05) decreased the pH, ammonia/total nitrogen ratio, and butyric acid content, but did not significantly affect the crude protein content, ether extract, ash or neutral detergent fiber and acid detergent fiber contents. The addition of LB significantly (P<0.05) decreased the lactic acid content, crude protein content, and dry matter recovery, and significantly (P<0.05) increased the pH, and ammonia/total nitrogen ratio. During aerobic exposure for 14 d, the pH of all of the silages increased slowly, and the temperatures of the silages were no more 2 ℃ higher than ambient temperature, indicating that all of the TMR silages were highly stable under aerobic conditions. Treatment of the TMR silage with LB and SDA inhibited yeast and mold growth to different degrees, and improved the aerobic stability of TMR silage containing wet brewers’grains. The silage treated with SDA performed better than that treated with LB. These results indicated that adding SDA at 0.5% of fresh weight could not only improve the fermentation quality, but also the aerobic stability of TMR silage containing wet brewers’grains.

Effects of exogenous nitric oxide on antioxidant activity and photosynthetic characteristics of Prunella vulgaris seedlings under NaCl stres

CHANG Qing-Shan, ZHANG Li-Xia, YANG Wei, ZHOU Shan-Shan, HUANG Qing-Zhe, LV Feng-Juan, HUANG Yue, GE Shu-Hui, ZHANG Tian-Meng

2016, 25(7):  121-130.  DOI: 10.11686/cyxb2015454

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The objective of these experiments was to determine the effects of exogenous nitric oxide (NO) on the antioxidant activity and photosynthetic characteristics of Prunella vulgaris seedlings under salt stress. Seedlings of P. vulgaris under salt stress (70 mmol/L NaCl) were treated with sodium nitroprusside (SNP, an exogenous NO donor) at different concentrations (0.01, 0.05, 0.10 and 0.50 mmol/L) and their antioxidant enzyme activity, photosynthetic pigment contents, gas exchange, and chlorophyll fluorescence characteristics were analyzed. The results showed that 0.05-0.10 mmol/L SNP alleviated symptoms of NaCl stress in P. vulgaris seedlings. The 0.10 mmol/L SNP treatment produced the best results. The seedlings in this treatment showed significantly increased (P<0.05) activities of peroxidase and catalase, decreased malondialdehyde content and electric conductivity, significantly increased (P<0.05) chlorophyll content, net photosynthetic rate, stomatal conductance, and transpiration rate, and decreased intercellular CO₂ concentration. Analyses of chlorophyll fluorescence data showed that the 0.10 mmol/L SNP treatment resulted in a significant decrease (P<0.05) in initial fluorescence and non-photochemical quenching, and increased maximum fluorescence, photosystem Ⅱ (PSⅡ) potential fluorescence efficiency, PSⅡ maximum fluorescence efficiency, and PSⅡ excitation capture efficiency in leaves of salt-stressed P. vulgaris seedlings. These results showed that application of SNP at certain concentrations stabilized membranes by increasing the activities of antioxidant enzymes, and improved photochemical efficiency. These changes alleviated photoinhibition damage resulting from salt damage to the PSⅡ center, and enhanced the photosynthetic capacity to increase the salt resistance of P. vulgaris seedlings. The 0.10 mmol/L SNP treatment had the greatest effect on improving salt tolerance of P. vulgaris seedlings under these experimental conditions.

Effects of Chromium stress on physiological and ecophysiological characteristics of male and female plants of Humulus scandens

WANG Bi-Xia, XIAO Juan, FENG Xu, GAN Li-Fen, TANG Ya

2016, 25(7):  131-139.  DOI: 10.11686/cyxb2015436

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This paper studied the differences of sex-specific and photophysiological characteristics of male and female plants of Humulus scandens exposed to chromium (0, 50, 200 and 300 mg Cr³⁺/kg soil). The results showed: 1) the net photosynthetic rate (P_n), chlorophyll fluorescence parameters, root fresh weight and stem length were greater in the females than males for the plants grown under 0 mg/kg (control), but the chlorophyll and malondialdehyde (MDA) concentrations were lower for females than for the males. 2) Compared with control plants, P_n was significantly increased in the 50 mg/kg Cr³⁺ treatment for both male and female plants, but chlorophyll fluorescence parameters were significantly decreased by Cr³⁺ in male plants and the value of other photophysiological indexes and plant growth were slightly increased by Cr³⁺, while Cr³⁺ had no effect on the value of photophysiological indexes and growth of female plants. The value of P_n and the MDA concentration were similar to those of control plants in 200 mg/kg Cr³⁺ treatment, but the root fresh weight and chlorophyll fluorescence parameters were significantly lower than for control plants. However, the 300 mg/kg Cr³⁺ treatment significantly inhibited both of the male and female plants, and in this treatment P_n was significantly decreased (especially in male plants; females demonstrated enhanced ability to repair damage) compared to control plants, and all of the above-mentioned indexes and parameters were also significantly lower than control plants. 3) Overall, P_n of male and female plants first increased and then decreased with Cr³⁺ exposure time, while stem length, root fresh weight and chlorophyll fluorescence parameters were directly decreased, and MDA content and the apparent electron transport rate (E_TR) were promoted. However, the chlorophyll content of males decreased with increasing Cr³⁺ concentration, but there was no significant decrease in chlorophyll content and photosystem II reaction centers for the female plants. In summary, P_n was increased by low Cr³⁺ concentration and inhibited by higher Cr³⁺ both in male and female plants. The plants demonstrated self-protective physiological response mechanisms. This was especially true for the female plants, which have a more flexible response strategy with higher tolerance capacity.

Effect of substitution ratio of Imperata koenigii on competitiveness and growth potential of three species of cold season lawn grass

MA Jiao, ZONG Ren-Xu, LIU Jin-Ping, ZHANG Li-Hui, WU De

2016, 25(7):  140-147.  DOI: 10.11686/cyxb2015440

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A composite replacement experiment was carried out to analyze the effect of five substitution ratios of Imperata koenigii on competitiveness and growth potential of three species of cold season lawn grass (tall fescue, Kentucky bluegrass, perennial ryegrass). Single plant biomass, relative yield, total relative yield, attack and competitiveness, plant height, tiller number, pseudostem and root traits, among others, were determined. I. koenigii substitution had an antagonistic effect on the lawn grasses. The substitution ratio of I. koenigii had a highly significant effect on relative yield and total relative yield of the 3 species (P<0.01). With increasing substitution ratio of I. koenigii, the attack and competitiveness indexes of the lawn grasses were gradually reduced. Grass species was the main factor determining attack and competitiveness of lawn grass, and the three species tested ranked in order: tall fescue>Kentucky bluegrass>perennial ryegrass; the next most important factor was the substitution ratio of I. koenigii. The substitution ratio of I. koenigii had a significant effect on tiller number, pseudostem traits and root characteristics of the three lawn grass species (P<0.05). The ranking of the species for regeneration ability was Kentucky bluegrass>perennial ryegrass>tall fescue, while the ranking for root length and biomass was perennial ryegrass>Kentucky bluegrass>tall fescue. Attack and competitiveness index of ryegrass in the seedling stage was significantly greater than for tall fescue and Kentucky bluegrass (P<0.05). The stress impact of I. koenigii substitution on roots of perennial ryegrass was significantly greater than that of the other two species (P<0.05), resulting in a decrease of perennial ryegrass growth potential. The competitiveness and attack of tall fescue was lower, than the other lawn grasses and I. koenigii substitution enhanced the stem and root traits of tall fescue to significantly lower than those of perennial ryegrass and Kentucky bluegrass. Therefore, tall fescue had a very high growth potential. These results indicate that I. koenigii presence in the three species of lawn grass studied, necessarily led to damage to sward population composition and structure of the lawn grasses. Management measures should applied to prevent I. koenigii invasion of lawns in order to improve lawn quality and persistence.

Effects of fertilizer and soil additives on plant nutrient utilization in a degraded soil

HUANG Rong, GAO Ming, YE Xia-Yi, WANG Wen-Qiang, LIU Bin-Bin, LIU Jiang, DAI Wen-Cai

2016, 25(7):  148-157.  DOI: 10.11686/cyxb2015441

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The objective for this study was to provide a scientific basis for evaluating the effects of different amelioration methods on plant nutrient utilization in degraded soil by analyzing their influence on yield, quality and nutrient content of vegetables. Seven amelioration treatments were assessed across four different vegetables including lettuce and water spinach. Compared with the control (CK), amelioration treatments improved the yield of vegetables, especially NPKH (N-P-K fertilizer+biomass ash) and NPKW (N-P-K fertilizer+biological fertilizer). Amelioration treatments increased the nitrate (N{Invalid MML}-N) content of vegetables compared with CK. The nitrate content of lettuce complied with Regulation GB/T15401, suggesting it did not reduce the quality of lettuce. Nitrate contents under the fertilizer plus amendment treatments were lower than those under the fertilizer (NPK) only treatments; nitrate content for the NPKW treatment was 7.8%-63.0% lower than NPK treatments. The NPKH treatment increased amino acid content, reduced nitrate content and improved apparent N recovery rate of N fertilizer. NPKH also markedly improved P and K contents in lettuce. However, compared with the CK, the K content of lettuce under NPKH was reduced by 43.4%-58.9%. The fertilizer utilization efficiency under NPKH and NPKW was higher than other treatments in water spinach, increasing the N, P, K content of water spinach under these treatments. This research indicates that fertilizer application with amendments can maintain high vegetable crop yields and stimulate N uptake and transformation by the crop.

Relationship between nitrogen after-effects and the yield and agronomic traits of monocropped and intercropped soybean

WANG Jia-Rui, WANG Ke, ZHAO Ya-Ni, XU Kai-Wei, ZHOU Tao, CHEN Yuan-Xue

2016, 25(7):  158-167.  DOI: 10.11686/cyxb2015567

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A field experiment was conducted to study the after-effects of nitrogen applied at different rates (0, 60, 120, 180 kg/ha) to wheat on the yields and agronomic traits of a subsequent soybean monoculture (wheat-soybean cropping system) and soybean intercrop (wheat/maize/soybean intercropping system) in the 2013-2014 growing season. The results showed that soybean in both monoculture and intercropping systems made full use of the after-effect of nitrogen applied to wheat. The biomass and grain yield of soybean first increased and then decreased as the rate of nitrogen application to wheat increased. The highest biomass and grain yield of monocropped soybean and the highest yield of intercropped soybean (4133 kg/ha) were in the N₁₂₀ treatment. The biomass of monocropped soybean was 62.3% higher than that of intercropped soybean at the branching stage, but the biomass of intercropped soybean was 57.9% higher than that of monocropped soybean at the harvest stage. Compared with monocropped soybean, intercropped soybean showed 63.9% higher grain number per plant and 55.9% higher yield. The 100-grain weight did not differ significantly between intercropped and monocropped soybean. The grain yield from the main stem and branches accounted for 54.2% and 45.8%, respectively, of the total yield of monocropped soybean. However, grain yield from the branches accounted for 68.9% of the total grain yield of intercropped soybean. Although the lodging rate was 5.2% higher for intercropped soybean than for monocropped soybean, the empty sticks rate was 78.0% lower and the blighted pod rate was 25.4% lower for intercropped than for monocropped soybean. The percentage of branch grain yield increased with increasing nitrogen application to wheat. The main stem length of intercropped soybean (average, 39.5 cm) was 6.2 cm longer than that of monocropped soybean (average, 33.3 cm) at the branching stage while that of monocropped soybean (average, 84.8 cm) was 10.4 cm longer than that of intercropped soybean (average, 74.4 cm) at the harvest stage. The length of the first stem was greater in intercropped soybean (8.3, 6.6 cm) than in monocropped soybean (5.6, 4.6 cm) at both branching and harvest stages. The average number of branches was higher in monocropped soybean (1.9) than in intercropped soybean (0.7) at the branching stage, while that of intercropped soybean (6.1) was higher than that of monocropped soybean (3.5) at the harvest stage. The number of branches significantly increased with increasing nitrogen application to the former wheat crop. These results indicated that the soybean was able to utilize the residual N from nitrogen applied to wheat in both the wheat-soybean and wheat/maize/soybean systems. Although growth of intercropped soybean can be affected by maize, intercropped soybean can recover rapidly and resume rapid growth after the maize is harvested. The number of branches, pods, and filled pods as well as the grain yield can be increased through adjusting the amount of nitrogen applied to former crops.

Effects of nitrogen fertilizer on nitrate accumulation and nitrogen use characteristics in sweet sorghu

QU Hui, CHEN Jun-Feng, CHENG Liang, LU Xiao-Yan, SHEN Yi-Xin

2016, 25(7):  168-176.  DOI: 10.11686/cyxb2015411

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A field experiment was conducted to evaluate nitrate accumulation, crude protein (CP) content and nitrogen use efficiency of sweet sorghum (Sorghum bicolor cv. Hunnigreen) under different nitrogen fertilizer rates (0, 100, 200, 300, 400, 500 kg N/ha) in 2009 and 2010 in eastern China. The experiment was laid out in randomized complete block design with three replicates. Nitrate content of shoot decreased with plant growth and nitrate accumulation was higher in stems than leaves. The crude protein production efficiency (CPPE), nitrogen dry matter production efficiency (NDMPE), dry matter production efficiency (DMPE) and nitrogen apparent recovery rate (NARR) decreased with increasing rate of nitrogen fertilizer, indicating that the higher rates of nitrogen decreased nitrogen use efficiency and increased nitrogen losses. Crude protein (CP) and free amino acid (FAA) content increased with increasing rates of nitrogen. However, the increase of FAA was much less than that of CP. Mean CP content was 6.11%, while FAA content was 2.99% when nitrogen was applied at 500 kg N/ha, indicating that the application N increased the CP content, but decreased the proportion of high quality protein. Nitrate content of sweet sorghum increased with increasing rates of nitrogen, however, it was not above toxic levels, 0.2% of DM (dry matter), until application rates were above 400 kg N/ha. The most appropriate rate of nitrogen for sweet sorghum in eastern China was 200-300 kg N/ha; these rates increased the yield and quality of sweet sorghum, improved nitrogen use efficiency and also reduce nitrogen losses and nitrate contamination in soils and groundwater.

Physical properties of different turfgrass rootzone soil mixes and their effects on the growth of ‘Lanyin No.Ⅲ’ zoysiagrass

SONG Hua-Wei, LIU Ying, WANG Chen, LIU Tian-Zeng, ZHANG Ju-Ming

2016, 25(7):  177-185.  DOI: 10.11686/cyxb2015524

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Sports turf quality mainly depends on the turf-bed structure and its construction quality, and the choice of rootzone soil mixes greatly affects the turf quality, its usage and the maintenance budget in the longer term. ‘Lanyin No.Ⅲ’ zoysiagrass (Zoysia japonica cv. Lanyin No.Ⅲ) is widely used in sports turf in southern China. This study aimed to examine the effects of five different rootzone mixes with varying physical properties on turf growth of ‘Lanyin No.Ⅲ’ zoysiagrass. The five rootzone mixes were 100% puresand (A), sand∶peat (85%∶15%) (B), sand∶soil (85%∶15%) (C), sand∶soil∶peat (85.0%∶7.5%∶7.5%) (D), and 100% pure soil (E). Soil bulk density, total porosity, capillary porosity, non-capillary porosity, and saturated hydraulic conductivity of the rootzone mixes were measured, together with turf color, regrowth rate and aboveground biomass to determine the effects of the various rootzone media on the growth of ‘Lanyin No.Ⅲ’ zoysiagrass. The bulk densities of the five rootzone media differed in the early stage of establishment, but did not differ in the late stage of establishment. Air permeability and hydraulic conductivity of the rootzone media containing sand were significantly higher than those with pure soil. However, the sand rootzones media containing 15% soil, 15% peat, or mixture of 7.5% peat and 7.5% soil showed no obvious differences in soil porosity and hydraulic conductivity. The rootzone media comprising pure soil produced good turf quality with better color, regrowth speed and more aboveground biomass than the other media. The turf quality when turves were grown on rootzone media of sand mixed with peat, soil, and mixtures of peat and soil were similar, and slightly better than those grown in pure sand. Based on the above results, it is considered that a sand rootzone medium is suitable for the construction of ‘Lanyin No.Ⅲ’ zoysiagrass sports turf because it has more aeration and better drainage than the other media. The rootzone medium comprising pure soil was not suitable for sports turf because of poor aeration and drainage ability.

Seed emergence and growth of Caragana korshinskii in different habitat

SUN Yi, YAN Xing-Fu

2016, 25(7):  186-195.  DOI: 10.11686/cyxb2015449

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The aim of this study was to explore the mechanism of seed emergence and the factors affecting seedling regeneration of Caragana korshinskii. Field surveys and experiments were conducted in the C. korshinskii forest plantation in Baijitan Nature Reserve, Ningxia, China. We conducted field surveys and seed burial experiments in three different base habitats: C. korshinskii shrubs (CKS), Artemisia desertorum shrubs (ADS), and bare sand (BS); and in three different sand dune habitats: bottom (BSD), middle (MSD), and top (TSD). We also evaluated seed emergence and seedling growth at different distances from the base of C. korshinskii shrubs (0.5 m, 1.5 m, and shrub-interspace). The results showed that the habitat (CKS, ADS, and BS) and treatment (sand surface and sand burial) had significant effects on the percentage of seedling emergence (PSE) and survival rate of C. korshinskii seeds (P<0.05). In the ADS habitat, for example, the PSE of buried seeds was significantly higher than that of seeds on the sand surface during the early stage of the survey (P<0.05) and significantly higher than those of buried seeds in both the CKS and BS habitats (P<0.05). The highest PSE was in buried seeds in the ADS habitat, but there was no significant difference in PSE between the other two habitats and between buried seeds and those on the sand surface. The results also showed that the PSE of seeds planted at the BSD was significantly higher than that of seeds planted at the TSD (P<0.01; 20 times higher at the end of the experiment). The maximum and minimum PSE was at 1.5 m from the C. korshinskii shrub base and in the shrub-interspace, respectively, on all survey dates. All three habitats showed the highest PSEs on July 18, but there were no significant differences in PSE and emergence rate (ER) among the three habitats during the whole experiment period. The maximum seedling height, basal stem diameter, taproot length, root∶stem ratio, and total dry mass of seedlings were in BSD, while the maximum root∶shoot ratio was in TSD. Seedlings at 0.5 m from the C. korshinskii shrub base had the greatest seedling height (P<0.05). With increasing distance of seedlings from the C. korshinskii shrub base, the tap root length, root∶stem ratio, and maximum root∶shoot ratio increased, but total dry mass decreased.

Effect of sowing quantity and method on seedling quality and yield of Astragalus membranaceus var. mongholicus in Weiyuan, Gansu Province, Chin

MI Yong-Wei, CAI Zi-Ping, WU Wei-Guo, WANG Guo-Xiang, WANG Hong-Xia, PENG Yun-Xia, GONG Cheng-Wen, WEI Li-Xia

2016, 25(7):  196-202.  DOI: 10.11686/cyxb2015565

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The aim of this study was to determine the effects of seeding density and sowing method on the quality and yield of Astragalus membranaceus var. mongholicus, to provide the basis for a normalization-cultivation technique. We used the Longqi No.2 cultivar as the experimental material. The seeds were sown at three different densities (90, 150, 210 kg/ha) using four different sowing methods (drilling, broadcast sowing, plastic mulching, and hole sowing). Then, quality indicators and yield were measured at the end of the nursery cultivation. There was a significant effect of the interaction between the seeding density and sowing method on seedling quality parameters, both at the individual and the population scale. As the sowing density increased, single seedling fresh weight, root length, and root diameter tended to decrease, seedling yield first increased and then significantly decreased, and seedling number increased while the proportion of superior seedlings decreased significantly. Under the same sowing density, the plastic mulching and hole sowing methods showed the best performance, in that the proportions of superior seedlings were higher than those obtained using the drilling and broadcast sowing methods. As the seeding density increased, the seedling yield first increased and then decreased when the plastic mulching and hole sowing methods were used, but tended to decrease when the drilling and broadcast sowing methods were used. At the seeding density of 150 kg/ha, the largest number of superior seedlings per unit area was achieved using the plastic mulching and hole sowing methods. These results show that seeds of A. membranaceus var. mongholicus should be sown at a density of 150 kg/ha and cultivated using the plastic mulching or hole sowing methods for the best results in Weiyuan.

Research advances on fungal diseases of Vicia sativa

XU Shan, LI Yan-Zhong

2016, 25(7):  203-214.  DOI: 10.11686/cyxb2015478

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Vicia sativa (Leguminosae) is one of the most important and widely cultivated crops in China. By the end of 2015, 14 fungal diseases of V. sativa had been reported from 28 countries. Of these 14 diseases, 10 infect the leaves and stems, three infect the roots, and one infects the plants systemically. Four fungal pathogens (Alternaria alternata, Aphanomyces euteiches, Pythium debaryanm, Verticillium dahliae) have only infected V. sativa abroad, and two (Epicoccum nigrum and Stemphylium botryosum) have only infected V. sativa in China. In China, 10 fungal diseases of V. sativa have been detected in 10 provinces. Among these provinces, Gansu has the most fungal diseases (eight), followed by Yunnan (six). In total, there are 43 fungal pathogenic species that infect V. sativa. These pathogens belong to the Deuteromycotina (58%), Ascomycotina (16%), Basidiomyotina (14%), and Mastigomycotina (12%). Of these 43 fungal pathogens, 15 occur only abroad, seven occur only in China, and seven are specific to V. sativa. In addition, six seed-borne fungi have been detected in V. sativa seeds in China, and four of them are known to have negative effects on seed germination and seedling growth. Until now, there have been few studies on the harm, life cycle, and management of fungal diseases of V. sativa, although some studies have described aspects of common diseases such as anthracnose, powdery mildew, rust and botrytis. With the increasing cultivation area of V. sativa and the increased demand for this crop, it is important to study its main fungal diseases to evaluate yield losses, to accurately identify the causal agents, to evaluate the dynamics and occurrence of diseases, and to develop effective management strategies.