Table of Content

20 October 2015, Volume 24 Issue 10

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Orginal Article

Carbon storage and carbon density of forest vegetation in Luoyang, Western Henan Province

WANG Yan-Fang, LIU Ling, LI Zhi-Chao, SHANGGUAN Zhou-Ping

2015, 24(10):  1-11.  DOI: 10.11686/cyxb2015078

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The loessial hilly region of Western Henan comprises loess soils primarily covered in forest and is of great significance for environmental protection in central and western China. Forest resource inventory data obtained from the Luoyang area of western Henan in 2007 formed the basis of this study. An average biomass computational method recommended by the Intergovernmental Panel on Climate Change (IPCC) was used to estimate forest carbon storage and carbon density under different forest types, tree species, stand ages and forest origins as well as the spatial distribution patterns of stored carbon in Luoyang forests. The results showed that the total forest vegetation carbon storage in the study area was 31.45 Tg (1 Tg=1×10¹² g) with an average forest vegetation carbon density of 38.81 Mg/ha (1 Mg=1×10⁶ g). In which the carbon storage of arbor forest was 25.06 Tg, accounting for 79.67% of the total forest vegetation carbon storage in study area, and the average carbon density of various tree species was 42.08 Mg/ha. The carbon storage of different forest categories ranked in the order: arbor forest>four-side tree>economic forest>shrub forest>bamboo forest>scattered trees>open forest. Quercus forest had the highest carbon storage and Larch forest the lowest carbon density among different tree species. The carbon storage and carbon density of natural forest were higher than that of plantation forests. Carbon storage in different Counties of Luoyang ranged from 0.31 to 10.34 Tg, and carbon density ranged 18.41 to 44.47 Mg/ha. Forest carbon storage systematically increased from northeast to southwest. Hence, Songxian County had the highest carbon storage and carbon density while Yanshi County had the lowest. Research area forest mainly consisted of young-age and middle-age forests but the carbon density of mature forests was the highest among all of the age classes. The forest vegetation in the loessial hilly region of Luoyang in western Henan has potential to store considerable quantities of carbon through growth of young and middle-aged forests.

Effects of nitrogen addition on the physical properties of soil in an alpine meadow on the eastern Qinghai-Tibetan Plateau

LIU Xiao-Dong, YIN Guo-Li, WU Jun, CHEN Jian-Gang, MA Long-Xi, SHI Shang-Li

2015, 24(10):  12-21.  DOI: 10.11686/cyxb2015154

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A 3-year study was conducted from 2012 to 2014 to determine the effects of nitrogen (N) addition on the physical properties of soil in an alpine meadow in Xiahe County on the eastern Qinghai-Tibetan Plateau. The four treatments were as follows: CK (control, no N addition), LN (low N, 50 kg N/ha), MN (medium N, 100 kg N/ha), and HN (high N, 150 kg N/ha). Each N-addition treatment had three replicates of 54 m² (6 m×9 m), with a 1.5 m isolation band between adjacent plots. Analyses of soil bulk density, soil porosity, soil compaction, and soil aggregates showed that MN and HN treatments reduced soil bulk density and soil compaction, increased soil porosity and non-capillary porosity, and maximized water-holding capacity in the 0-10 cm soil layer. In the 20-30 cm soil layer, compared with CK, all N-addition treatments showed higher soil bulk density and soil compaction, reduced soil porosity, and maximized water-holding capacity. In terms of the effect of N addition on the stability of soil aggregates in the 0-30 cm soil layer, the LN, MN, and HN treatments dramatically increased the macro-aggregate content (≥0.25 mm) and MWD (mean weight diameter), with the MN treatment having the strongest effect. Compared with CK, LN and MN dramatically improved the water-stable aggregate content. All of the N-addition treatments significantly promoted soil aggregation and increased the MWD of aggregates. The results indicated that N addition could effectively prevent soil erosion, and hence, control the loss of water and soil nutrients. The MN and HN treatments significantly increased the aboveground biomass in the grassland, while underground biomass was increased in the MN treatment and decreased in the HN treatment. The results of this study showed that the MN treatment was the most beneficial treatment in terms of improving soil properties. This treatment increased soil bulk density, reduced soil porosity, and increased soil compaction, increased the content of ≥0.25 mm soil aggregates and improved aggregate stability, and increased both the aboveground and underground biomass of plants in the grassland.

Analysis of soil respiration under different grazing management patterns in the alpine meadow-steppe of the Qinghai-Tibet Plateau

LI Wen, CAO Wen-Xia, LIU Hao-Dong, LI Xiao-Long, XU Chang-Lin, SHI Shang-Li, FENG Jin, ZHOU Chuan-Meng

2015, 24(10):  22-32.  DOI: 10.11686/cyxb2015152

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In recent decades, the carbon cycle of terrestrial ecosystems has become a hot topic in global climate change research. Soil respiration is the main route by which soil organic carbon (SOC) enters the atmosphere, and also the main contributor to increased atmospheric carbon globally. As the earth’s largest terrestrial ecosystem, grassland is a very important carbon sink that stores one-quarter of the world’s SOC. The alpine meadow-steppe of the Qinghai-Tibet Plateau is known as the roof of the world, as it is the highest, largest, and most unique type of grassland in the world. The Qinghai-Tibet Plateau alpine meadow-steppe is becoming seriously degraded because of its unique geographical location and harsh natural environmental conditions, combined with recent global climate change, human occupation and animal grazing, and rats and insect pests. Reasonable grazing management is one of the main measures to restore the grassland ecosystem, and has important implications for the healthy development and sustainable use of grassland. However, there is little information on soil respiration under different grazing management models in the Qinghai-Tibet Plateau. In this study, an LI-8100A Automated Soil CO₂ Flux system was used to investigate soil respiration under four grassland management strategies: no grazing (NG); grazing rest at the growing stage (RG); traditional grazing rest in summer (TG); and continuous grazing (CG). The aim of this study was to deepen our understanding of soil respiration in the alpine meadow-steppe ecosystem, to assess the impacts of global warming, and to evaluate the effects of rest grazing on the alpine meadow-steppe ecosystem. The results showed that: 1) soil respiration differed from month to month under the different grazing patterns, first increasing and then decreasing. In all of the treatments except for CG, the highest soil respiration rates were in August, and were significantly higher than those in the other months. There was no significant difference in soil respiration between August and September in the CG treatment, but the rates in both months were significantly higher than those in other months. 2) In the growing season, soil respiration was significantly higher in the NG, RG, and TG plots than in the CG plot, and there was no significant difference in soil respiration between the NG and RG plots. 3) There was a significant positive correlation between soil respiration and soil temperature under all of the rest grazing patterns, but not under CG. Based on their Q₁₀ values, the plots were ranked as follows: NG>RG>TG>CG. 4) There was a threshold at which the effects of soil water content on soil respiration changed; that is, the two were positively correlated at soil water contents of 30% or lower, and negatively correlated at soil water contents of >30%. 5) Soil respiration was significantly correlated with aboveground and belowground biomass. Considering the economic income stability of the herdsmen, the management pattern of grazing rest at the growing stage could promote the efficient use of grassland resources, and help to restore forage productivity and maintain the grassland ecosystem. Therefore, grazing rest at the growing stage is the best management strategy for the alpine meadow-steppe grassland in the Qinghai-Tibet Plateau.

Effects of fencing and grazing on vegetation and soil physical and chemical properties in an alpine meadow in the Qinghai Lake Basin

LI Yang, YAN Zhen-Ying, GUO Ding, WANG Hai-Xia, SU Shu-Lan, LI Xu-Dong, FU Hua

2015, 24(10):  33-39.  DOI: 10.11686/cyxb2014429

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The aim of this study was to determine the effects of fencing on the productivity and structure of plant communities and on the physical and chemical properties of soil in alpine meadows. A field study was conducted in two types of degraded alpine meadows, one dominated by Kobresia pygmaea and the other dominated by Kobresia humilis, in the Qinghai Lake Basin. The results showed that the aboveground biomass of K. pygmaea and K. humilis increased by 33.8%, and 31.5%, respectively, after 2 years of exclosure. Exclosure significantly increased the proportion of aboveground biomass of sedges and members of the gramineae, and decreased the proportion of aboveground biomass of forbs. Exclosure also resulted in significant increases in plant community diversity and evenness indexes. In the K. pygmaea and K. humilis alpine meadows, grassland soil organic carbon content in the 0-10 cm soil layer increased by 10.15% and 12.74%, respectively, after 2 years of exclosure. The soil organic carbon content in the 10-30 cm soil layer did not change significantly after 2 years of exclosure. In K. humilis meadow soil, the total phosphorus content increased by 16.13% in the 0-10 cm soil layer, but was unchanged in 10-30 cm soil layer after 2 years of exclosure. In the K. pygmaea and K. humilis alpine meadows, soil bulk density increased by 6.61% and 6.25%, respectively, and pH decreased by 4.04% and 3.69%, respectively, in the 0-10 cm layer after 2 years of exclosure. In the 10-30 cm soil layers of both types of meadows, neither soil bulk density nor pH was affected after 2 years of exclosure.

Relationships between plant diversity, soil property and productivity in an alpine meadow

SHI Hong-Xiao, HOU Xiang-Yang, SHI Shang-Li, WU Xin-Hong, LI-Peng, YANG Ting-Ting

2015, 24(10):  40-47.  DOI: 10.11686/cyxb2014509

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The relationships among primary productivity, soil factors and plant diversity in alpine meadows were investigated by analyzing plant community diversity, productivity and soil nutrients of three grassland types in the Three Rivers District, Kobresia pygmaea+Kobresia humilis, Kobresia pygmaea+forbs and Kobresia pygmaeaPolygonum macrophyllum meadow. The biomass, community diversity and soil physical and chemical properties of the different alpine meadows types differed significantly (P<0.05). The Kobresia pygmaea+P. macrophyllum meadow had the highest productivity, number of species and soil nutrient content. Correlation analysis showed that forage biomass and soil physical-chemical properties (P<0.05) and soil organic matter (P<0.01) were significantly positively correlated. The number of plant species present was also correlated with soil nutrients (P<0.01), while uniformity and diversity of community structure were positively correlated (P<0.01) with soil potassium content. The competitive advantage of dominant species was associated with tolerance of low fertility(P<0.05), particularly phosphorus. Aboveground biomass and forage biomass and available phosphorus were significantly positively correlated (P<0.01). Nitrogen was associated with species richness and productivity.

Impact factors and relationships between biodiversity and biomass of different communities in the desert steppe of Ningxia, China

YANG Yang, LIU Bing-Ru

2015, 24(10):  48-57.  DOI: 10.11686/cyxb2014438

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Impact factors and relationships between plant biodiversity and biomass of different communities of desert steppe in an unmodified condition were determined using biodiversity indices, soil physical and chemical factors and assessment of aboveground and underground biomass. The results showed that species richness and diversity varied similarly in different communities. Exponential relationships between aboveground biomass and underground biomass showed that the desert steppe community displayed allometric growth patterns. The response of community richness to aboveground biomass was unimodal, while that to underground biomass was linear. Underground biomass was positively correlated with surface litter. Soil moisture, soil organic carbon, total nitrogen and available nutrients also contributed to underground biomass while soil moisture and soil organic carbon greatly contributed to aboveground biomass. Soil microbial biomass, soil carbon and nitrogen had a significant influence on community diversity indices.

Alfalfa science research by Chinese scholars since 1950: history and main topics

LIU Zhi-Ying, LI Xi-Liang, QI Xiao, LI Feng, FANG Shan-Shan, WANG Zong-Li, SUN Qi-Zhong

2015, 24(10):  58-69.  DOI: 10.11686/cyxb2015129

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Alfalfa (Medicago sativa) has been cultivated in China for more than 2000 years since its introduction during the Han dynasty. Currently, alfalfa is the most widely planted forage grass in China. Despite the importance of this species as a forage, research on alfalfa began late in China, and has rapidly developed in recent years. In this study, we obtained data from the Web of Science (WOS), China National Knowledge Infrastructure (CNKI), and other related databases, and then used a literature metrology method to analyze the history of research on alfalfa conducted by Chinese scholars since 1950. We explored the research achievements, evolution of hot spots, and key nodes in a historical context of nearly 65 years, and compared the tracks of domestic and international research on alfalfa. Our results showed that, since 1950, there has been an increase in the momentum of research on alfalfa conducted by Chinese scholars. According to the growth curve of the number of alfalfa publications, the period since 1950 can be divided into five periods, with the fast-growth stage in alfalfa research occurring after 2000. Our analyses showed that the internationalization of Chinese alfalfa research has increased over time, and that China is now the second-most important source of alfalfa research. In the early years of alfalfa research, the main topics were the mining of local varieties and genetic resources. More recently, research topics have included yield improvement, quality improvement, and breeding and cultivation theory. Also, there has been a considerable body of research on the development of alfalfa industries, comparisons of alfalfa cultivation and use between China and other countries, molecular biology, and interspecific relationships. The growth of the alfalfa industry, the emergence of new science and technology journals, and the increase in funding for scientific research have contributed to the rapid developments in alfalfa research over the last 65 years. The results of this study suggest that with the transformation of food structure and the development of grassland agriculture in China, alfalfa research has shifted from basic theory to technology, so that it can support the needs of major national strategies and provide basic science knowledge.

Use of the stochastic frontier production function in a technical efficiency analysis of grass production: An example from the “One River and Two Tributaries” region of Tibet

QU Yun-He, YU Cheng-Qun, SUN Wei, WU Jun-Xi, LI Shao-Wei

2015, 24(10):  70-79.  DOI: 10.11686/cyxb2014360

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Based on the agricultural household on-the-spot investigation data collected in the “One River and Two Tributaries” Region of Tibet, we estimated the technical efficiency of grass production of agricultural households using the stochastic frontier production function. This method estimates the contributions of grass family differences, farm size, and region distribution to the technical efficiency of grass production. The results indicated that there is a loss of technical efficiency in grass production in the “One River and Two Tributaries” Region of Tibet. The yield per mu could increase by approximately 30% with improved technical efficiency. The output elasticity coefficients with respect to input factors of labor, seeds, fuel, organic fertilizer, chemical fertilizer, and land were 0.1423, 0.2197, 0.1309, 0.2600, 0.2265, and 0.0206, respectively. Grass family difference was identified as the key factor in improving technical efficiency. Farm size and liquidity strongly affected the technical efficiency of grass production via their effects on other input factors such as labor and capital. This was because of the disadvantageous position of resource use, compared with animal husbandry and off-farm industries. Human capital and agricultural comprehensive production capability did not affect the technical efficiency of grass production. Increasing the grass yield by improving technical efficiency can include measures such as extending the production technology to legume forage grasses, enlarging grass planting areas, and identifying which grass families are best adapted for growth in different regions, especially Lhasa.

The effect of different alfalfa varieties on the midgut protease activity of pea aphid (Acyrthosiphon pisum)

DA Li-Ting, ZHU Ya-Ling, SONG Li-Wen, HU Gui-Xin, WANG Sen-Shan

2015, 24(10):  80-87.  DOI: 10.11686/cyxb2014470

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This research measured the midgut protease enzyme activity in the red and green pea aphid (Acyrthosiphon pisum) after they had fed on 8 alfalfa (Medicago sativa) varieties with differing resistance. The midgut protease activity of the red pea aphid was (9.71±0.63) U/mL after they had fed on the variety Weinan, and was (0.33±0.10) U/mL after feeding on variety Sandili. The protease activity of the green pea aphid was (9.88±0.56) U/mL after feeding on the variety Hunter river, and (0.43±0.02) U/mL after feeding on Sandili. The midgut lipase activity of the red pea aphid was (4.12±0.30) U/mL when they infested the cultivar Hunter river, but was only (1.63±0.10) U/mL (P<0.05) when they infested the variety Gannong No.5. Lipase activity was (4.00±0.29) U/mL when aphids had fed on the variety Weinan, and was (1.08±0.13) U/mL when feeding on the cultivar Gannong No.5. The midgut amylase activities of the red and green pea aphids were (2.30±0.40) U/mL and (2.14±0.29) U/mL, respectively when they had fed on the cultivar Hunter river. In summary, for pea aphid infestation of 8 alfalfa varieties with differing aphid resistance, a high negative linear correlation was observed between the resistance of the different alfalfa varieties and the protease, lipase and amylase activities of the pea aphid, i.e. when the alfalfa aphid resistance is higher, the enzyme activity is lower. Hence it is concluded that the resistant alfalfa varieties restrict the midgut digestive enzyme activity of the pea aphid.

Identification and biological characteristics of Fusarium sporotrichioide isolated from Medicago sativa root

PAN Long-Qi, ZHANG Li, YANG Cheng-De, YUAN Qing-Hua, WANG Yu, MIAO Li-Hong

2015, 24(10):  88-98.  DOI: 10.11686/cyxb2014466

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The strain BYE27-2-5 isolated from alfalfa (Medicago sativa) with root rot in north China was comprehensively evaluated by analyses of its biological characteristics, morphology, and ITS sequence. The optimum temperatures for mycelium growth, sporulation, and spore germination were 25℃, 30℃, and 28℃, respectively. The strain was able to grow in a pH range of 5.0-11.0 and the optimal pH for sporulation and spore germination were 8.0 and 7.0, respectively. Alternative light conditions were optimal for mycelial growth whereas complete light conditions were optimal for sporulation and spore germination. Spores germinated most rapidly at 95% relative humidity or in water-drop conditions, and failed germinate at relative humidity levels below 75%. Dextrose peptone medium was the best medium for mycelial growth and spore germination and potato dextrose agar was the best medium for sporulation. The best carbon source for mycelial growth and spore germination was glucose and that for sporulation was sucrose. The best nitrogen source for mycelium growth was peptone and that for spore germination and sporulation was yeast extract. The lethal temperature for mycelia was 54℃ (10 min) and that for spores was 48℃ (10 min). Based on these biological characteristics and the results of an ITS sequence analysis, the isolate was identified as Fusarium sporotrichioide.

Root system distribution characteristics of three herbs and their effects on soil composition and nutrients in the ‘Purple Soil’ region

CHEN Yun, HE Bing-Hui, LIAN Cai-Xia, LIU Zhi-Peng

2015, 24(10):  99-107.  DOI: 10.11686/cyxb2014456

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In order to explore the effects of herb roots on soil physical properties and soil nutrients, alfalfa (Medicago sativa), Bermuda grass (Cynodon dactylon) and vetiver grass (Vetiveria zizanioides), planted for three years, were used for these experiments. Taking bare plots as a contrast, soil and root samples from 0-10 cm, 10-20 cm and 20-30 cm soil layers were collected. Then the WinRHIZO (Pro.2004c) root analysis system was used to measure root parameters and conventional methods were used to measure soil physical and chemical properties. In all three soil layers, vetiver grass root parameters were excellent, especially root length density and root surface area density, for these two traits the maxima averaged 13.46 cm/cm³ and 5.75 cm²/cm³, respectively. Overall, root weight density (RWD) of alfalfa was the greatest, with a minimum average of 18.10 mg/cm³. None of the three herbs had any significant effects on soil physical properties 3 years after planting, but data for the herb plots showed that the proportion of sand particles had decreased and the proportion of finer particles (silt and clay) had increased, compared to bare CK plots. Most herbs had significant effects on soil organic matter and available potassium in most soil layers, with content of organic matter increasing and content of available potassium decreasing. However, the herbs had almost no effect on soil total nitrogen, alkali-hydrolyzable nitrogen, total phosphorous, available phosphorous and total potassium. The total potassium contents of all herb plots (3.93-4.83 g/kg) were higher than the bare plots, but the available potassium levels of all herb plots were low, especially in alfalfa. The maximum deficient number was 20.24 mg/kg. All soil nutrients had significant correlations (P<0.05) with all or some of the root parameters, and the maximum correlation coefficient was 0.833, for the relationship between organic matter and RWD.

The phylogenetic significance of fruit structures in Bupleurum of the family Apiaceae

CHANG Xiu-Qi, LIU Mei, CHENG Xin-Yu, WANG Yu-Ting, WEI Xue-Ying, WANG Xue-Wei

2015, 24(10):  108-119.  DOI: 10.11686/cyxb2015067

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The three-dimensional structure of fruits of 29 species, 5 varieties and 2 forms in the genus Bupleurum, from China were studied in depth and are reported for the first time in this paper. The fruit structures were found to vary greatly. The mericarp surfaces are smooth, approximately circular in transverse section, and ribs are slightly prominent. Two types of secretory structures, rib ducts and vittae, occur in the mesocarps. The former which are small in diameter are found in a few taxa and the latter include unbranched and branched vittae. The vittae occur in the furrow (1-5) and commissure (2-7) in most taxa, and they are similar to mericarps in length, usually unbranched, and sometimes short. The vittae are branched in a few taxa and dispersed in the mesocarps. The testa is composed of one or two layers of parenchyma cells. The endosperm is flat or slightly concave on the commissural side. Crystals are not present in the mesocarp. There are usually two carpophores, which are arranged on opposite sides of the commissural plane. Most features of the genus are present in other groups of the Apioideae, but branching vittae and testa with two layers of cells are only found in the Azorelloideae, Saniculoideae, and some groups of the Apioideae. The anatomical structures of Bupleurum fruits support its continued classification in the Apioideae, as shown by molecular studies.

Analysis of the forage and grain productivity of oat cultivars

ZHOU Qing-Ping, YAN Hong-Bo, LIANG Guo-Ling, JIA Zhi-Feng, LIU Wen-Hui, TIAN Li-Hua, CHEN You-Jun, CHEN Shi-Yong

2015, 24(10):  120-130.  DOI: 10.11686/cyxb2014465

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In order to explain reason for forage and grain yield difference of oat cultivars, eight oat cultivars widely planted in Qinghai province were used in this study. Special-traits of the high yield oat was found through cluster analysis, correlation analysis and multiple stepwise regression. The main results as below. 1) The forage and grain yield productivity was different among cultivars, the forage and the grain yield of Qingyan 1 and Linna was highest, and that of the Caoyou 1 and Qingyou 2 was lowest. 2) Eight oat cultivars could be grouped into two clusters according to the cluster analysis. Cluster 1 included Jiayan 2, Qingyin 2, Caoyou 1 and Qingyou 2, they have relatively poor performance. Cluster 2 included Linna, Qingyan 1, Neon and Qingyongjiu 887, they have relatively better performance, with 12.8% and 14.2% higher forage and grain yield than that of cultivars in cluster 1. 3) The forage yield of both two clusters was positively correlated to the stem diameter, and negatively correlated to the plant height. Also the grain yield of both two clusters were positively correlated to the plant height, grain weight per spike, kernel weight, the length and the width of the seed with rafter, indicating that the relationship between forage yield and traits of oats are relatively stable. 4) The multiple stepwise regression results showed that the contribution rate of the stem diameter to the forage yield was high and significant, and the same for the contribution rate of the stem diameter and seed width to the grain yield for both two clusters. Compared with the first cluster, the smaller negative coefficient value of stem diameter and the larger positive coefficient of the seed width in the regression equation between traits and yield is the inner high yielding reason for the second cluster. Thus, the stem diameter and the seed width could be used as an important index in the selection and breeding of oat.

Seed germination characteristics of the desert subshrub Atriplex cana and its ecological significance

CAI Dan-Hong, YAN Cheng, WEI Yan

2015, 24(10):  131-138.  DOI: 10.11686/cyxb2014463

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Abstract:Atriplex cana is a xerophytic subshrub with drought resistance, salinity resistance and low fertility tolerance. It is a useful forage plant in Xinjiang. Experiments were conducted to determine the effects of temperature, seed bract removal, and NaCl on seed germination. Seeds were able to germinate in a range of temperatures from 5/15℃ to 25/35℃. The higher the temperature, the faster the germination occurred. The optimum temperature regime for seed germination was 20/30℃ and 25/35℃. Under a 25℃ dark/35℃ light regime, the final germination percentage reached a maximum value after 6-8 days of hydration, while under 5/15℃ and 10/20℃ temperature regimes final germination percentage was achieved after 25-34 days. There was a significant increase in seed germination rate after 2-8 months seed storage, while germination percentage of seeds decreased when exposed to natural atmospheric conditions for 10 months. Bracts formed a mechanical barrier to water uptake, and has a significant influence on the final seed germination rate. Removal of bracts promoted seed germination. Germination was not affected by NaCl at concentrations below 0.8 mol/L, but was decreased by NaCl at higher concentrations. Seeds incubated in NaCl at concentrations of 0.05-4.00 mol/L recovered after being transferred to distilled water. After NaCl treatment some seeds retained their vigor, while others lost vigor. Research into seed germination characteristics may reveal a scientific basis for this ecological adaptation trait. Such research may also provide basic data for improvement salinity tolerant forage subshrub production in the Xinjiang desert.

Effects of sowing time on yield and quality of Codonopsis pilosula seedlings

ZHAO Ya-Lan, CHEN Yuan, GUO Feng-Xia, GUO Zhi-Jun, LIU Xi-Quan

2015, 24(10):  139-148.  DOI: 10.11686/cyxb2014437

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To determine the most appropriate time to plant Codonopsis pilosula, an experiment comparing winter and spring sowing was conducted. Yield and quality of seedlings and soil water content were measured regularly after both sowing times. The results showed that the climatic condition in Longxi County is suitable for cultivating C. pilosula seedlings. Under both winter and spring conditions, the pattern of seedling emergence followed the typical ‘S’ curve which was able to be modelled using a logistic regression. Higher soil moisture in the 0-20 cm soil layer in the winter sown field resulted in seedling emergence 6 days earlier compared with spring sowing and yield was increased by 47.8% with good seedling quality. In contrast, the emergence rate of seedlings in the spring-sowing field was 27.3% greater than winter sown but the seedlings were small and of poor quality. In conclusion, the seedling cultivating sown in winter was of great significance to avoid the spring drought, suggesting that the seedling cultivating methods sown winter and spring should be adopted in proportion in order to reduce the seed ablastemic risk when sown in spring caused by the severe drought tress. It is worth noting that when cultivating the plant seedlings whether sown in winter or spring the keeping-moisture measures should be promptly taken after sowing and the wheat straw is the perfect for the coverage.

Effects of frequent uind-sand flow on photosynthesis and water metabolism of Pinus sylvestnis var. mongolica seedlings

ZHAO Ha-Lin, LI Jin, ZHOU Rui-Lian, YUN Jian-Ying, QU Hao, PAN Cheng-Chen

2015, 24(10):  149-156.  DOI: 10.11686/cyxb2014414

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In order to understand effects of frequent wind-sand flow on photosynthesis and water metabolism of Pinus sylvestnis var. mongolica seedlings, a field wind-sand flow experiment with a gradient wind speed treatments of 0 (CK), 6, 9, 12, 15 and 18 m/s (wind sand flow intensity are 1.00, 28.30, 63.28, 111.82 and 172.93 g/cm·min, respectively) was conducted in the Horqin Sand Land of Inner Mongolia in the Spring, 2013. The photosynthetic rate (P_n), transpiration rate (T_r) and water use efficiency (WUE) were investigated. The results showed that, 1) frequent wind sand flow could change diurnal variation pattern of the T_r, stomatal conductance (G_s), intercellular CO₂ concentration (C_i) and WUE in the Pinus sylvestnis var. mongolica seedlings, but had litter effects on diurnal variation pattern of the P_n; 2) With increase of wind-sand flow strength, the RWC and leaf temperature, average daily P_n, WUE tended to decrease, which decreased by 4.6%, 1.8%, 52.6% and 56.3% in the 18 m/s treatment than that in the CK, respectively; and the average daily T_r, G_s and C_i tended to increase, which increased by 31.6%, 75.0% and 30.9% in the 18 m/s treatment than that in the CK, respectively. 3) With increase of wind-sand flow strength, the daily maximum P_n and WUE tended to decrease, the maximum daily C_i tended to increase, the maximum daily T_r decreased when wind-sand flow was below 15 m/s and increased when wind-sand flow was in 15 m/s and 18 m/s. 4) In wind-sand flow stress, decline of photosynthetic ability in P. sylvestnis var. mongolica scapling mainly due to decrease of the relative water content (RWC) and leaf temperature and the leaf mechanical damage, and increase of the T_r was attributed mainly to significant increase of the G_s.

Physiological responses of three forages to drought stress and evaluation of their drought resistance

JIN Jun-Ying, ZHANG Wei-Hua, YUAN Ling

2015, 24(10):  157-165.  DOI: 10.11686/cyxb2014505

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The aim of this study was to evaluate the drought stress responses of various forages and to select forage cultivars with high drought resistance. A pot experiment was carried out to study the effects of drought stress on the growth and physiology of Hemarthria compressa, Sudangrass (a Sorghum hybrid), and Dolichos lab lab. The drought responses, as measured using various physiological indices, differed among the three forages. The biomass of the three forages continuously decreased as the duration of the drought treatment extended. The maximum decrease in biomass under drought, as compared with their respective controls, was 18.29% for H. compressa, 31.21% for Sudangrass, and 33.55% for D. lab lab. Light and medium drought treatments had little effect on the root growth of H. compressa and Sudangrass, but increased their root:shoot ratios. The decrease in shoot biomass under drought reduced water consumption, and the increased root:shoot ratios increased the water and nutrition absorption capacity of the plants. The drought treatments damaged cell membranes and increased the malondialdehyde content, resulting in leakage of intracellular materials, increased relative electric conductivity, reduced chlorophyll content, and lower root activity, all of which inhibited growth of the three forages. Under drought stress, the proline content in tissues of the three forages was 1.3-8.1 times that in their respective controls, and there were significant increases in soluble sugar content and soluble protein content, which aided osmotic adjustment. The drought treatments also promoted the activity of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) in the three forages. The increased antioxidant enzyme activities helped to eliminate free oxygen radicals to mitigate drought damage. A comprehensive evaluation of the drought resistance of the three forages using the membership function method ranked their drought resistance, from strongest to weakest, as follows: H. compressa>D. lab lab>Sudangrass.

Biological characteristics and nutrients of the photoperiod-sensitive Sorghum×Sudangrass varieties in the arid land of east Gansu

HE Zhen-Fu, HE Chun-Gui, WEI Yu-Ming, LIU Long-Sheng

2015, 24(10):  166-174.  DOI: 10.11686/cyxb2014492

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We studied the biological characteristics, the change in nutritional value at different growth stages and the impact of cutting frequency on production with three photoperiod-sensitive Sorghum×Sudangrass varieties: Monster, Big Kahuna and BJ0603 in the arid land of east Gansu. All varieties were sown in late April and were at the heading or flowering stage when harvested in early October. Hence the reproductive growth stage was not completed. At harvest, the differences in plant height, node number, leaf number and stem diameter among varieties were not significant, but the differences in the weight of leaf and single stem (stalk and leaves) were significant. The standardised grass yield (65% moisture content) and the dry matter production under one cut in one year were higher than those under two cuts, but not significantly different, while the fresh grass production under two cuts was significantly higher. The differences in the fresh grass production, the standardised grass yield and the dry matter production were significant among varieties whether under one or two cuts, with the yield ranking: Monster>BJ0603>Big Kahuna. From the early jointing stage to the booting stage, the levels of crude protein (CP) and ether extract (EE) in the stem decreased, while the acid detergent fiber (ADF) and neutral detergent fiber (NDF) values increased. The crude fiber (CF) and soluble sugar levels increased and then decreased, while the crude ash content (ASH) dropped sharply and the nitrogen free extract (NFE) values first decreased and then increased. The contents of CP, ADF, NDF, ASH, NFE and soluble sugar differed significantly among varieties, while no significant difference in EE and CF content was observed. Based on the variation in yield and nutrient content, the best utilisation strategy for photoperiod-sensitive Sorghum×Sudangrass was to cut once per year as silage and to harvest before the first frost. If utilized as hay or green chop, the best strategy in the arid land of east Gansu would be to cut twice yearly with the first cut performed between the late jointing stage and the booting stage, and the second cut before the first frost.

Effect of phosphorus application under drip irrigation on the productivity and quality of alfalfa in Northern Xinjiang

ZHANG Fan-Fan, YU Lei, MA Chun-Hui, ZHANG Qian-Bing, LU Wei-Hua

2015, 24(10):  175-182.  DOI: 10.11686/cyxb2014467

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In order to improve the productivity and nutritional value of alfalfa under drip irrigation, this study compared two varieties of alfalfa (Xinmu No.2, Sanditi) with different patterns of phosphorus application under drip irrigation in oasis area of northern Xinjiang. Five fertilizer treatments were established, 180 kg/ha phosphate fertilizer (L₁), 360 kg/ha phosphate fertilizer (H₁), 180 kg/ha phosphate fertilizer split application (L₂), 360 kg/ha phosphate fertilizer split application (H₂) and no phosphate fertilizer (control). The results show that different patterns of phosphorus application influence hay production, growth speed, leaf-stem ratio on first cut and plant height on third cut of Medicago sativa cv. Xinmu No.2 (P<0.05), and hay production and growth speed on third cut of M. sativa cv. Sanditi (P<0.05), and they have no significant influence on other indicators of productivity(P>0.05). And different patterns of phosphorus application influence crude protein and fibre on each crop time and crude ash on first cut of M. sativa cv. Xinmu No.2 (P<0.05), and crude ash on first and third cut of M. sativa cv. Sanditi (P<0.05), and they have no significant influence on other indicators of nutrition value (P>0.05). Application on each indicator of annual performance of two varieties of alfalfa, this test adopts similar priority ratio analysis to synthesize each indicator. And then the rank of optimum pattern of phosphorus application is H₁>L₁>H₂>L₂>CK.

Effects of phosphate fertilizer on yield, quality and plant nutrient form in lettuce in ‘calcareous purple’ soil

CHEN Yi, WANG Zheng-Yin, TANG Jing, ZHANG Xiao-Ling, YANG Dong, XIANG Hua-Hui, LI Rong

2015, 24(10):  183-193.  DOI: 10.11686/cyxb2014462

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Field experiments were conducted to examine lettuce production in ‘calcareous purple’ soils with six different phosphate (P) levels (0, 45, 90, 135, 180 and 270 kg/ha P₂O₅) at two sites (1. Hanhu village and 2. Hanjin village) in order to investigate effects of the different P fertilizer levels on yield, quality and plant nutrient form in lettuce. Yields of lettuce for the two sites were significantly increased (9.5%-26.7% and 8.1%-21.3%, respectively) by application of P fertilizer and maximum yields were obtained from the P₄ treatment (180 kg P₂O₅/ha). There was a significant quadratic regression relationship between P fertilizer rates and yields of lettuce, the maximum yield and economic optimum application rates were, respectively, 219 and 215 kg/ha (P₂O₅) for site No.1, and 195 and 191 kg/ha for experimental site No.2. Contents of vitamin C, amino acids and soluble sugar of lettuce were reduced in all treatments and in the P₂ treatment were decreased, respectively, by 15.8%, 27.8% and 14.0% for site No.1. At site No. 2, nitrate contents of the lettuce were decreased and vitamin C contents were improved in all treatments and were increased by 6.3% and 20.4% in P₄ and P₅ treatments, respectively. Levels of amino acids and soluble sugar were reduced in all treatments and for the P₄ treatment were decreased by 35.0% and 8.3%, respectively. Nitrate contents were reduced, with the P₂ treatment decreased by 6.9%. The highest contents of total-N and total-P of lettuce were achieved in the P₄ treatment for both experimental sites. With respect to forms of plant nutrients: N, P and K were mainly present as protein-N, non-protein-P and non-protein-K, respectively in the lettuce. K levels correlated more closely with lettuce quality than did N and P levels. Total-K showed a significantly positive correlation with vitamin C and amino acid levels for site No.1, but protein-K showed a negative correlation with vitamin C for site No.2. The maximum P use efficiency was obtained from the P₁ treatment (8.14% and 9.38%, respectively), followed by the P₄ treatment (4.64% and 7.42%, respectively), for the two experimental sites. Overall, from this study, the recommended application rate of P fertilizer for P-deficient ‘calcareous purple soil’ used for vegetable production was 180 kg/ha (P₂O₅) under these conditions.

The impacts of grazing on the soil microorganism population of grassland

GOU Yan-Ni, NAN Zhi-Biao

2015, 24(10):  194-205.  DOI: 10.11686/cyxb2014460

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Soil quality is crucial to sustainable development of grassland ecosystems and to their productivity. Healthy soil must have rich species diversity, active microorganism populations, an efficient internal nutrient cycle and good buffering against disturbance. Soil microorganisms are the main driver of various biological processes and are therefore very important in soil systems. Hence, soil microbial community characteristics such as population numbers, community structure and species diversity can be used as a measure of soil health. The present paper summarizes the effects of grazing on the grassland soil microbial populations, community structure and diversity. We propose that it is essential to understand the impact of grazing management on soil microorganisms. A methodology is introduced for evaluation of soil health, and selection of a suitable grazing level to improve grassland management, and the advantages and disadvantages are discussed. Two key questions are addressed; namely the responses of the soil microbial community to grazing activity, and how to use these indicators to evaluate soil quality and propose a reasonable grazing practice to sustainably improve the productivity of grassland.

Effect of soil conditioner on the growth of Lolium multiflorum

YUAN Yao, GUO Jian-Bin, YIN Shi-Meng, MOU Xia

2015, 24(10):  206-213.  DOI: 10.11686/cyxb2014503

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To explore the effect of soil conditioners which are applied to semiarid regions of the Loess Plateau, this study compared pots planted with Lolium multiflorum seed with and without the soil conditioners. Three self-made soil conditioners (A, B, C) and a standard soil conditioner (D) were compared. The results showed that soil conditioner application can significantly improve soil perviousness, but there was no difference in seedling emergence rates between untreated and soil conditioner treated pots. Soil conditioner C produced significantly better height growth in L. multiflorum plants, 16.6% and 33.7% higher than that of the standard soil conditioner and the untreated soil respectively. Tiller numbers in pots treated with soil conditioner C were 18.5% and 33.8% higher than that of standard soil conditioner and the untreated soil respectively while the biomass was 40% and 185% higher, respectively. The appearance utilization rate of phosphorus was 10.28% treated with soil conditioner C. Therefore, self-made environment-friendly soil conditioner C was the best soil conditioner among them. The study will provide a theoretical guide for soil conditioner application and vegetation restoration in semiarid regions of the Loess Plateau.

Effect of silicon addition on seedling morphological and physiological indicators of Glycyrrhiza uralensis under salt stress

CUI Jia-Jia, ZHANG Xin-Hui, LI Yue-Tong, ZHOU Da, ZHANG En-He

2015, 24(10):  214-220.  DOI: 10.11686/cyxb2014445

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In this study, a water culture experiment was conducted to investigate the effect of silicon addition on the morphological indicators (radicle, seed germ) and physiological indicators [membrane permeability, malondialdehyde (MDA) level and peroxidase activities] of Glycyrrhiza uralensis seedlings under salt stress. Two NaCl concentrations (100 and 200 mmol/L) and six Si levels (0, 0.4, 0.8, 1.2, 1.6 and 2.0 mmol/L) were set as treatments in the experiment. Potassium silicate (K₂SO₄) was used as the source of Si. The Si addition can effectively increase the length and dry weight of germ and radicle of G. uralensis seedlings under salt stress. Under 100 mmol/L NaCl, the 0.4 mmol/L Si treatment promoted radicle growth the most among all the Si treatments, while under 200 mmol/L NaCl, the 0.8 mmol/L Si treatment promoted radicle growth the most. Exogenous Si addition was also able to increase the peroxidase activity and proline content, and reduce the levels of MDA under salt stress. In conclusion, G. uralensis showed enhanced osmotic stress resistance and reactive oxygen scavenging capacity under salt stress when exogenous Si was added to the culture medium and Si addition alleviated growth suppression of G. uralensis seedlings caused by salt stress.