Table of Content

20 April 2013, Volume 22 Issue 2

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Regional characteristics of the alpine meadow degradation succession on the Qinghai-Tibetan Plateau

WANG Jian-bing, ZHANG De-gang, CAO Guang-min, TIAN Qing

2013, 22(2):  1-10. 

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The degradation succession characteristics of alpine meadow on Qinghai-Tibetan Plateau were studied comprehensively from 2005 to 2012. The results indicated that the typical zonal vegetation on Qinghai-Tibaten Plateau was Gramineae and Kobresia humilis community. The degraded grassland in Guoluo of Qinghai Province was characterized with large-scale erosion of mattic epipedon in Kobresia pygmaea community and forbs-black soil. It was at the stage of succession from K. humilis to K. pygmaea community in Yushu of Qinghai Province. The alpine meadow successes from K. humilis to K. pygmaea community, or it remains the normal K. pygmaea community in the north part of Tibetan Plateau. The reduced excellent edible forage of Gramineae and Cyperaceae, and the increased forbs coverage were the main characteristic of alpine meadow degradation. Meanwhile, this degradation caused the increased soil compaction and the topsoil was more sensitive. The bulk densities of different layers in 0 to 10 cm, 10 to 20 cm and 20 to 40 cm were increased by (0.50±0.08) g/m³, (0.16±0.07) g/m³ and (0.04±0.03) g/m³ respectively. Meanwhile, The soil organic matter content was greatly reduced by 19.3% to 53.2% and the reduction slowed down with the soil depth.

Desertification dynamic change trend and quantitative analysis of driving factors of alpine meadow in Maqu County in the First Meander of the Yellow River

CHEN Wen-ye, ZHANG Jin, QI Deng-chen, ZHAO-ming, ZHANG Ji-qiang, LI Guang-yu, WEI Qiang, WANG Fang, ZHU Li, LIU Zhen-heng, SUN Fei-da, KANG Jian-jun, LUO Wen-li

2013, 22(2):  11-21. 

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Based on the remote sensing and GIS technology and the methods of remote sensing dynamic monitoring, data interpretation combined with field investigation, the desertification space-time evolution process and its development trend of Maqu alpine meadow (Gansu) in recent 35 years was analyzed according to the selection of remote sensing image in 1975, 1990, 1994, 2000, 2005 and 2009, and integrated the topographic map, desertification monitoring data of each period and data of land use map. Based on this basis, the desertification drive factors are quantitatively identified and analyzed on contribution rate according to the grey correlation degree analysis method. The results show that, 1) the desertification in the research area showed a continuous expansion trend followed by time changes, and this trend developed a process of slow development→slight decrease→fast development. Mobile sand dunes developed a process of low development→rapid development→reverse, semi-fixed sand dunes developed a process of low development→rapid development→rapid reverse and fixed sand dunes showed a trend of slow development→reverse→rapid development. The spatial pattern of the desertification land distribution area showed an expanding situation and the desertification degree showed a trend of reducing volatility along the Yellow River. 2) the correlation order of driving factors and desertification land area is: GNP>number of sheep of each year>population>mean annual temperature>animal output value>mean annual precipitation>number of large animals of each year>mean annual evaporation>beef and mutton production>aridity index>runoff volume of the Yellow River>average wind speed; the driving force natural and human factors on the proportion of desertification land area were 40.43% and 59.57%, respectively. These results showed that abnormal disturbance of climatic warming was induced and the secondary factors which lead to grassland desertification, human irrational activities was the strengthened and leading factors which accelerated the land desertification development and the expansion of grassland desertification in the research area is the integrated process which is combined with action and influence of the two kinds of factors.

Soil respiration of Hulunber meadow steppe and response of its controlling factors to different grazing intensities

DENG Yu, LIU Xiao-ni, YAN Rui-rui, WANG Xu, YANG Gui-xia, REN Zheng-chao, XIN Xiao-ping

2013, 22(2):  22-29. 

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From June to September in 2010, soil respiration was measured at six different grazing intensities in experimental plots in Hulunber meadow steppe using a LI-6400-09 Soil Chamber to understand the influence of different grazing intensities on soil respiration of grassland. The controlling factors of soil respiration were taken into account under different grazing intensities. 1) Soil water content, root biomass, above ground biomass, and litter accumulation decreased with an increase of grazing intensity. However, soil temperature had an irregular change pattern with an increase of grazing intensity. 2) The dynamic changes in soil respiration rate have a double peak curve from different grazing intensities during the whole experimental period, while the varied mode of the mean value of soil respiration rate can be expressed as R₁ >R₀ >R₂ >R₃ >R₄ >R₅. There was no significant difference between R₀ and R₁. The soil respiration rate was higher in R₀ and R₁ treatments than in the R₅ treatment except on September 30th. Soil respiration rate was dramatically influenced by grazing intensity, with a more intense response under the R₄ and R₅ grazing intensities. 3) The effect of grazing intensiy on soil respiration changed with variation of grazing season or date showing there was an interaction between them. The partial correlation of time analysis has shown that soil temperature, soil water content, root biomass, above ground biomass, litter accumulation had significantly positive correlations with soil respiration under different grazing intensities but there was a significantly negative correlation with grazing intensities. The lower grazing intensity (R₁) had no adverse effect on soil respiration rate and its controlling factors, while the higher grazing intensities (R₄ and R₅) have obviously influenced them.

Effects of land use patterns on soil phosphorus fractions in the Longzhong part of the Loess Plateau

TENG Ze-qin, LI Xu-dong, HAN Hui-ge, ZHANG Chun-ping, FU Hua

2013, 22(2):  30-37. 

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We investigated the soil phosphorus fractions in croplands (planted and fallow, which had a history of traditional cultivation for at least 50 years)and grasslands (fenced and grazed, which had been restored from cultivation for 24 years) on the Loess Plateau. 1) Different land use patterns changed soil phosphorus fractions. The contents of active inorganic phosphorus(H₂O-Pi, NaHCO₃-Pi), potential active inorganic phosphorus(NaOH-Pi), and stable inorganic phosphorus (DHCl-Pi )in the 0-10 cm soil layer and highly stable inorganic phosphorus (HHCl-Pi)in the 30-60 cm soil layer in the croplands were significantly higher than those in the grasslands due to long-term fertilization of the croplands; 2) The conversions between soil phosphorus fractions mainly occured between moderately stable inorganic phosphorus (DHCl-Pi)and other phosphorus components, and also mainly in the 0-20 cm soil layer in the croplands; 3) Available phosphorus and total phosphorus were significantly correlated with H₂O-Pi, NaHCO₃-Pi, and NaOH-Pi. There were significant correlations between total soil nitrogen, soil organic carbon and NaOH-Pi, NaOH-Po, and HHCl-Pi (P<0.01). Soil pH was significantly and negatively correlated with NaHCO₃-Po (P<0.05), H₂O-Pi, NaHCO₃-Pi, NaOH-Pi, NaOH-Po, and HHCl-Pi (P<0.01).

The effects of nitrogen fertilizer on the contents of TOC, POC, SMBC and WSOC in two kinds of sandy substrates

ZHU Yi, HOU Xin-cun, WU Ju-ying, DUAN Liu-sheng, FAN Xi-Feng

2013, 22(2):  38-46. 

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The effects of continuous nitrogen fertilizer application on the contents of TOC (total organic carbon), POC (particulate organic carbon), SMBC (soil microbial biomass carbon) and WSOC (water-soluble organic carbon) under two types of marginal lands (gross sandy soil and pure sand) were studied using switchgrass planted in PVC pipes. Nitrogen fertilizer exerted significant effects on root dry weight, contents of TOC, POC, SMBC and WSOC at different soil depths of both gross sandy soil and pure sand (P<0.05). In both soil depths of the two types of substrates, the contents of TOC, POC and SMBC all reached a maximum under the N₄ gradient, while the WSOC content decreased. For all nitrogen concentrations there was no significant difference in the vertical distribution of root dry weight, contents of TOC, POC, SMBC and WSOC under both types of substrate. The maximum of all indexes appeared at the 0-60 cm depth.

A study on the nutrient value of oat and its influences on soil fertility of winter fallow fields

XIE Zhao-liang, ZHANG Teng-fei, CHEN Xin-zhu, ZHANG Jian-guo

2013, 22(2):  47-53. 

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The yields, nutrient value and fermentation quality of two oat (Avena sativa) varieties and their effects on soil fertility of winter fallow fields were investigated to provide a theoretical basis for ensiling and processing of oats and further development of winter paddy fields. The four treatments of control A (fallow fields, no fertilizer), control B (fallow fields, with fertilizer), black oat treatment and yellow oat treatment were made in triplicate. There was no significant difference in hay yields, crude protein yields or relative feed value between the two oat varieties (P>0.05). Neither of the two oat varieties achieved a good fermentation quality under natural silage conditions, while adding lactic acid bacteria significantly increased the content of lactic acid and reduced pH, contents of butyric acid and ammonia-nitrogen of silages (P<0.05), thus markedly improving the fermentation quality. The contents of organic matter, total N and total K in winter paddy soil were significantly increased by cultivating oats. Planting yellow oats increased the contents of soil available P (P<0.05) to 36.66%, 31.75% and 18.03% higher than that of control A, control B and the black oat group, respectively. Planting black oat significantly (P<0.05) increased the activities of soil invertase and catalase which were 15.56% and 26.21% higher than that of control A, and 11.83% and 14.71% higher than that of control B. In summary, there is a great potential for cultivating oat in winter fallow fields, to not only produce large amounts of forages as silage material, but also to improve the soil nutrient and enzyme activities.

Effects of intercropping patterns on growth characters and yield of Angelica sinensis under continuous mono-cropping planting

WANG Tian-tao, WANG Qi, WANG Hui-zhen, ZHANG En-he

2013, 22(2):  54-61. 

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In order to alleviate or overcome obstacles of continuous mono-cropping in Angelica sinensis planting, a controlled study was conducted on 2 years continuous mono-cropping of A. sinensis planting filed in Min County, Gansu Province at 2011. The five intercropping patterns were angelica/rape, angelica/broad bean, angelica/garlic, angelica/wheat and angelica/oat, respectively, and mono-cropping angelica was concerned as a control. The growth characters and yield of A. sinensis were studied under the 6 cropping patterns. The plant height of angelica was the highest in angelica/garlic planting at all the growth stages among all treatments. At the seedling and rootstock thickening stage, increases of dry matter of angelica above ground under angelica/garlic planting were 31.51% and 21.28%, respectively, compared with mono-cropping angelica planting. At the seedling, rootstock thickening and harvesting stage, increases of dry matter of angelica underground under angelica/garlic planting were 25.00%, 36.65% and 54.75%, respectively, and increases of root stem diameter of angelica under angelica/garlic planting were 12.26%,4.80% and 24.38%, respectively, compared with mono-cropping angelica planting. The dry matter of angelica above ground and underground decreased under angelica/oat planting. Compared with mono-cropping angelica planting, decreases of incidence of angelica Ditylenchus destructor were 46.05%, 43.31%, 25.24%, 2.34% and 12.82%, respectively, under angelica/rape, angelica/broad bean, angelica/garlic, angelica/wheat and angelica/oat planting, and increases of the first-class and the second-class of angelica were 118.62% and 27.82% under angelica/garlic planting. Yields of angelica reached 1 946 kg/hm² under angelica/garlic planting, and increases of yields of angelica under angelica/garlic planting were 67.29%, 143.31%, 207.57%, 683.06% and 34.71%, respectively, compared with angelica/rape, angelica/broad bean, angelica/wheat, angelica/oat and mono-cropping angelica planting. Intercropping patterns had effects on the emergence rate and bolting percentage of angelica, but the effects were not significant. The intercropping pattern of angelica/garlic planting increased the yields, the first-class and the second-class of angelic, and decreased the incidence of D. destructor, so the angelica/garlic planting was the best intercropping pattern to alleviate or overcome the obstacles of continuous mono-cropping in A. sinensis planting in Min County, Gansu Province.

Potential distribution of Tausch’s goatgrass (Aegilops tauschii) in both China and the rest of the world as predicted by MaxEnt

FANG Feng, ZHANG Chao-xian, HUANG Hong-juan, LI Yan, CHEN Jing-chao, YANG Long, WEI Shou-hui

2013, 22(2):  62-70. 

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Tausch’s goatgrass (Aegilops tauschii) is a serious weed worldwide. Determination of the potential geographical distribution of Tausch’s goatgrass is an important factor for effectively controlling the spreading of this weed. The potential distribution of Tausch’s goatgrass in China and in the rest of the world were predicted using the MaxEnt model. West Asia, the Middle-east, the Mediterranean coast of south-eastern Europe and northern Africa are the main suitable areas for growth of Tausch’s goatgrass. In China the suitable areas are mainly distributed in Henan, Hebei, Shandong, southwest of Shanxi, Guanzhong Plain of Shaanxi, the central and south of Ningxia, southeast of Gansu, north of Hubei, Jiangsu and Anhui provinces. The global potential distribution area of Tausch’s goatgrass is mainly between 30° to 45° degrees north in the latitude of the main winter wheat producing areas. As the global climate changes, the potential distribution range of Tausch’s goatgrass will vary according to different emissions scenarios. With greenhouse gases under the A1b emissions scenario, by 2050, the potential distribution of Tausch’s goatgrass will have a tendency to expand, while under A2a and B2a emissions scenarios, the low- and medium-risk areas will tend to decrease, but the high-risk areas will not change significantly.

Estimation of diet composition and herbage intake of grazing sheep at different stocking rates in Inner Mongolia typical steppe by using n-alkanes technique

LIU Gui-he, ZHANG Ying-jun, WANG Shi-ping, HAN Jian-guo

2013, 22(2):  71-79. 

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In order to probe into the application of n-alkanes as markers for estimating diet composition and herbage intake of free grazing herbivores in rangeland, a rotational grazing experiment was conducted from 20th June to 20th September at 2004, at the Inner Mongolia Grassland Ecosystem Research Station of Chinese Academy of Sciences. Sixty 2-year-old wethers (Inner Mongolia fine wool sheep × Inner Mongolia sheep) were selected and allocated to the 5 stocking rates (1.33, 2.67, 4.00, 5.33 and 6.67 sheep/ha) without significant difference (P>0.05) in body weight (36.9±2.6) kg to evaluate the effect of stocking rates and grazing seasons on dietary composition and intake of grazing sheep, at the same time, total feces of each sheep were collected using bag attached to body and 10 cages (1.2 m×1.2 m) were arranged randomly within each paddock to assess approximately how many species ingested by grazing sheep based on the difference between aboveground biomass of each species inside and outside cages after grazing. Only the stocking rates of 1.33, 4.00 and 6.67 sheep/ha were dosed with one Artificial QSM Alkane Controlled Released Capsules (Made in New Zealand Captec Company) at the beginning of the experiment each time. The samples of herbage and feces were collected daily for 7 days and dried for n-alkane concentration analysis using gas chromatography to estimate the feces output, diet composition, and herbage intake of sheep. The results show that there was a difference in concentration of n-alkanes among each plant species, and there were no significant difference (P>0.05) between estimated feces output using n-alkane technique and the actual values by sheep. 7-9 species forages were ingested by sheep, and plant species and its proportion were eaten by sheep were different at different stocking rates and grazing season, but their intake did not differ significantly (P>0.05). In conclusion, n-alkanes technique can estimate accurately and easily dietary composition and intake of grazing sheep when used in combination with the cage technique in natural temperate grasslands.

Effects of additive and moisture content on fermentation quality of smooth vetch silage

CHEN Peng-fei, BAI Shi-qie, YANG Fu-yu, GAN You-min

2013, 22(2):  80-86. 

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The fermentation quality of smooth vetch (Vicia villosa var.) silage kept for 60 days were investigated using smooth vetch with high (fresh) and low (wilt for 3 hours) moisture content. Ammonium formate (3, 6 L/t), lactic acid bacteria (1.0×10⁵ cfu/g FW), antimicrobial mixture including sodium benzoate, sodium propionate, sodium nitrite, and hexamethylenetetramine (3, 6 L/t) were added separately at ensiling but the CK had no additives. The results indicated that the fermentation quality of smooth vetch silage with high and low moisture contents were highly significantly (P＜0.01) affected by additives, but positive performances depended on the levels. The moisture content played a highly significantly positive role in improving the fermentation quality of smooth vetch silage except for the pH value (P＜0.01). The group with low moisture content performed better than the one with high moisture content. Highly significant (P＜0.01) interactions occurred between the two factors (additives and moisture content). Overall, in the high moisture content silage group, the treatments with added ammonium formate (6 L/t) and antimicrobial mixture (3 L/t) showed the best performance in fermentation quality of smooth vetch silage. In the high moisture content silage group, all treatments showed positive effects compared with the CK but without significant differences. To make silage with high quality, reducing the moisture content and adding suitable additives before ensiling are suggested.

Effects of plant solid powder and ethanol extract of Impatiens balsamina on microbial metabolic parameters during in vitro rumen fermentation

WANG Dong-sheng, HUANG Jiang-li, ZHANG Zhi-hong, TIAN Xiao-juan, HUANG Huang, YIN Yu-long, DING Jian-nan

2013, 22(2):  87-93. 

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The effects of Impatiens balsamina preparations, including ethanol extracts and plant solid powder (0.5%, 1.0% and 2.5%), on methane production and metabolic parameters of cattle rumen microorganisms were studied in vitro. Forages with straw 0.90 g, corn 0.45 g and soybean 0.15 g (1 mm screen) were transported in 250 mL serum bottles containing 200 mL liquid (artificial saliva and ruminal liquor in a 2∶1), and incubated at 39℃. Total gas production by the original plant solid powder was the highest, monensin treatments the lowest, and ethanol extracts were intermediate. Although the treatments of both I. balsamina and monensin reduced methane production, it was lowest in the original plant solid powder treatments. Monensin treatments reduced carbon dioxide production while I. balsamina increased it. Furthermore, the treatments of I. balsamina preparations and monensin reduced ammonia nitrogen (NH₃-N), and as I. balsamina contents increased, ammonium nitrogen production decreased. The MCP of monensin treatments was the least, while those of original plant solid powder treatments (S1, S2, S3) were significantly higher than that of the control and monensin treatments. Monensin treatments reduced the contents of acetate and total volatile fatty acid but increased propionate. Treatments of I. balsamina increased the volatile fatty acids contents,and compared with that of the control, the volatile fatty acids contents of ethanol extracts and original plant solid powder were increased by 12.9% and 20.2%, respectively. Moreover, the treatments of monensin and I. balsamina reduced the ratio of acetate to propionate. In conclusion, I. balsamina could reduce methane emissions, promote the conversion of NH₃-N to MCP, improve the metabolic model of in vitro rumen fermentation. The solid powder of I. balsamina was the most effective preparation.

Effects of red clover isoflavones on ascites syndrome incidence and antioxidant activity of broiler induced by cold exposure

JIANG Yi-bao, YANG Yu-rong, FENG Chang-song, WANG Cheng-zhang, CUI Guo-wen

2013, 22(2):  94-99. 

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The aim of this study was to observe the role of red clover (Trifolium pratense) isoflavones on ascites syndrome (AS) and antioxidant activity of broiler. Three hundreds broilers were randomized divide into three groups: normal temperature control group, low temperature group, low temperature and supplement red clover isoflavone group. AS was induced by cold exposure, ascites syndrome incidence was recorded. Six birds were randomly selected from each group on 14, 21, 28, 35 and 42 days, ascites heart index (AHI), packed cell volume (PCV), SOD (superoxide dismutase), MDA (malonaldehyde) and GSH-Px (glutathione peroxidase) in serum and liver were detected. The results showed that the incidence of AS was increased induced by cold exposure, treatment with red clover isoflavone attenuated AS incidence, AHI and PCV were decreased, further, red clover isoflavone elevated antioxidant activity of broiler.

Effect of alfalfa flavonoids on growth and reproduction performance of female rats

WANG Wei, MA Deng-tan, ZHAI Xin-ying, WANG Cheng-zhang, TIAN Miao-miao, YAN Xue-bing

2013, 22(2):  100-108. 

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The impact of different doses of alfalfa flavonoids on growth, reproduction and endocrine systems in female rats was studied using three doses of alfalfa flavonoids (120, 400, and 1 200 mg/kg) and two control groups (diethylstilbestrol 0.5 mg/kg and blank control group). Estradiol (E2), prolactin (PRL), progesterone (P), and growth hormone (GH) were determined by chemiluminescence. Related data of rat reproduction were uterine wet weight/coefficient, ovarian wet weight/coefficient, feed intake, daily body gain, litter size and newborn litter weight of rats. The low doses of alfalfa flavonoids increased the E2 level and uterine wet weight/coefficient (P<0.05) but significantly (P<0.05) reduced the ovarian wet weight/coefficient in mature female rats. GH levels were not significantly different in immature female rats but the middle and high dose groups had markedly reduced uterine wet weight/coefficients (P<0.05). However, feed intake was not significantly different although litter size and newborn litter weight had an increased trend in mature female rats. Litter size of middle and high dose groups increased 0.4% and 2.2% more than the blank control group (P>0.05). Newborn litter weight of middle and high dose groups increased 5.14% and 0.10% more than the blank control group (P>0.05). Therefore, different doses of alfalfa flavonoids influenced hormone secretions and the development of the reproductive organs before mating. Alfalfa flavonoids resulted in a significantly improved reproduction performance.

Butterfly diversity dynamics in different seasons at the Jindian National Forest Park, Kunming, Yunnan

PU Zheng-yu, SHI Jun-yi, YAO Jun, YANG Ling, ZHOU De-qun

2013, 22(2):  109-116. 

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From October 2010 to September 2011, butterfly diversity was surveyed over four seasons at the Jindian National Forest Park, Kunming. Specimens of 972 butterflies, belonging to 9 families, 49 genera and 69 species were captured and identified. The butterfly genus, species, individual numbers, diversity index and evenness index in different season were analyzed. The results showed the priority ranking as summer＞spring＞autumn＞winter; The dominance index ranking had the trend spring＞autumn＞summer＞winter. The similarity coefficient was related to the different season’ climate and was highest between autumn and winter but was lowest between summer and winter. Many butterflies species have two or more generations each year in the Kunming area.

UV mutagenesis and screening for fungicide resistant strains of Trichoderma aureoviride T2

YIN Ting, XU Bing-liang, LIANG Qiao-lan, GU Li-jun, LI Rong-feng

2013, 22(2):  117-122. 

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To obtain fungicide resistant strains, Trichoderma aureoviride strain T2 was tested against six fungicides and the most effective fungicide (Procymidone) was selected for screening against mutagenic strains derived by UV irradiation. The strains were grown on a range of procymidone concentrations (50-800 μg/mL) on a medicinal culture medium. Four strongly resistant strains (T2-1, T2-2, T2-5, and T2-6) were obtained. After the 10 inoculation, colony growth rate, sporulation and antagonism to Botrytis cinerea were assessed and the biological characteristics of the four strains were found to be constant. The T2-6 strain was significantly better than the other three strains.

Identification and biological characteristics of the pathogen causing the potato gangrene in Gansu Province

JIANG Hong-xia, YANG Cheng-de, XUE Li, PU Chong-jian, CHEN Xiu-rong, SHANG Xun-wu,LI Chang-sheng

2013, 22(2):  123-131. 

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Studied on the symptoms, pathogenic morphology of potato gangrene, the results showed that the symptoms of potato tubers were round, oval, or irregular, sunken lesions formed at the umbilicus or buds. These lesions gradually expanded to form khaki, lavender sunken lesions, in size from 1 to 3 cm. Small black bodies were observed in the center of the lesions. Isolates of Phoma spp. were isolated and purified from twenty-six samples of tuber rot of potatoes in Gansu Province. The morphologic characteristics, pathogenicity, symptoms, biochemistry characteristics and ITS sequence analysis of isolates all suggested they were Phoma foveata, which showed the rot of potatoes was caused by the P. foveata and the disease named gangrene. 30% propiconazole·difenoconazole, 35% carbendazim sulfonate, 5% Junduqing, 10% difenoconazoleyl and 32.5% difenoconazole·azoxystrobin had a better inhibiting action to P. foveata and the EC₅₀ were 2.43×10^-5, 1.77×10^-2, 7.40×10^-2, 1.31×10^-2 and 2.31×10^-1 μg/mL, respectively. The optimum temperature for mycelial growth and conidia germination were 20℃. There were difference on the color, size and edge of colony among different media, but the PDA media was the optimum for mycelial growth. The conidia could germinate under pH 3-10, and pH 6 was the suitable range for germination. The paper was the first report for potato gangrene in China and the results helped to control this disease in Gansu Province.

Isolation and characterization of PGPR from the rhizosphere of the Avena sativa in saline-alkali soil

LIU Jia-li, FANG Fang, SHI Xu-han, CHEN Hong-yan, YAO Lin, GUO Chang-hong

2013, 22(2):  132-139. 

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Two strains of plant growth-promoting rhizobacteria (PGPR) containing ACC deaminase, A-2 and A-4 were isolated from saline-alkali rhizosphere soil of Avena sativa, based upon their ability to utilize 1-aminocyclopropane-1-carboxylate (ACC) as a sole nitrogen source. Using morphology, physiological biochemical characteristics and 16S rDNA analysis, strain A-2 was identified as Enterobacter sp. and A-4 was confirmed as Pseudomonas sp.. The ACC deaminase activity of A-2 and A-4 were (1.89±0.12) μmol α-KA/(mg Pr·h) and (2.63±0.12) μmol α-KA/(mg Pr·h), respectively. When the concentration of L-Trp increased, the IAA synthesis of A-2 increased, while that of A-4 did not change significantly. The ability of A-2 to synthesize siderophore was greater than that of A-4. The height of oat plants treated with A-2 and A-4 were from 12.24 cm up to 13.98 and 14.07 cm, the plant fresh weights were from 34.285 g up to 35.012 and 35.102 g, respectively. The length of roots were from 14.13 cm up to 16.23 and 17.60 cm, and root fresh weights were from 7.790 g up to 8.065 and 8.187 g, respectively. These results suggest that strains A-2 and A-4 contain ACC deaminase that can increase resistance in oat to saline-alkali stress.

Cloning and bio-infomatical analysis of the high-affinity K⁺ transporter gene PutHKT2;1 from the halophyte Puccinellia tenuiflora

LI Jian, ZHANG Jin-Lin, WANG Suo-Min, GUO Qiang

2013, 22(2):  140-149. 

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Saline soils are normally dominated by Na⁺ which threatens plant growth and agricultural productivity. Increasingly research has focused on the functions of high-affinity K⁺ transporter HKT2;1 in controlling Na⁺ uptake, strengthening the selectivity of K⁺ and thus enhancing salt tolerance. A putative high-affinity K⁺ transporter gene PutHKT2;1 was isolated from the halophyte Puccinellia tenuiflora by RT-PCR and RACE methods and was used to investigate the sodium tolerance mechanism. The gene was 1 919 bp in total length with an open reading frame (ORF) of 1 638 bp encoding a 60.5 kDa protein with 546 amino acids and theoretical PI of 9.07. Sequence analysis suggested that the nucleotide sequence and the translated amino acid sequence shared over 75% and 66% of homology to the HKT2;1 gene sequences from other higher plants. The PutHKT2;1 protein might have 11 transmembrane segments. Secondary structure analysis indicated that the PutHKT2;1 contained a 47.99% α-helix, 5.13% β-turns, 31.87% random coils and 15.01% extended strand. Cloning the full length PutHKT2;1 gene and its bio-informatical analysis will be helpful to elucidate the salt tolerance mechanism of P. tenuiflora.

Transformation of the GsCRCK gene into Medicago sativa cv. Nongjing No.1 and salt tolerance analysis in transgenic plants

LIU Ying, CAI Hua, LIU Jing, BAI Xi, JI Wei, ZHU Yan-ming

2013, 22(2):  150-157. 

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The stress-responsive kinase gene of wild soybean (GsCRCK) was selected because of the gene expression profiles under salinity, drought and cold stresses, previously established in our laboratory. Over expression of GsCRCK in transgenic Arabidopsis resulted in enhanced plant tolerance to high salinity and ABA. In this study, one plant expression vector regulated by a 35S promoter (named as pBEOCRCK) were constructed to transfer the target gene into Medicago sativa cv. Nongjing No.1 separately by the Agrobacterium-mediated method. Many resistant seedlings of GsCRCK have been obtained. The results of PCR and RT-PCR showed that the GsCRCK gene was normally expressed in transgenic plants. After GsCRCK transgenic M. sativa cv. Nongjing No.1 were stressed with 0, 300 and 400 mmol/L NaCl, we compared transgenic M. sativa to non-transgenic M. sativa by assessing specific physiological indicators. The relative membrane permeability, the content of chlorophyll, the content of MDA, and the activity of SOD in plants which were stressed with 300 mmol/L NaCl were measured together with the death rate from a 400 mmol/L NaCl stress. The transgenic M. sativa had a greater tolerance of salinity stress compared with non-transgenic plants.

Genetic diversity of 20 ryegrass accessions by SRAP markers

LI Jie-qin, WANG Li-hua, ZHAN Qiu-wen, ZHU Kui, LIU Jing-liang, LI Wan-xiang

2013, 22(2):  158-164. 

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Sequence related amplified polymorphism (SRAP) markers were used to analyze the genetic diversity among 20 ryegrass (Lolium) lines. The results showed that 765 fragments were amplified by 53 primers. Polymorphic bands were 597 which accounted for 78.95% in the total amplified fragments. The number of amplified and polymorphic fragments was 14.43 and 11.26 per primer, respectively. The genetic similarity coefficients ranged from 0.485 to 0.727 among these ryegrass lines and the average was 0.627. Using unweighted pair-group method with arithmetic means (UPGMA) cluster analysis on the SRAP markers, these ryegrass lines could be divided into four groups by the threshold of 0.63. Two Lolium multiflorum lines could not be clustered into a group but spread in 18 Lolium perenne lines. In addition, cluster results were consistent with the resources of these ryegrass lines. All results suggested that SRAP markers were suitable for the research of the genetic diversity on ryegrass.

Cloning and expression analysis of the promoter of Caragana korshinskii gene

REN Ai-qin, YI Jin, GAO Hong-wen, LI Jun, WANG Xue-min

2013, 22(2):  165-170. 

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A genomic walking technique was used to clone the promoter sequence of the CkNCED1 gene from Caragana korshinskii. The plant CARE cis-element analysis revealed that, besides the basic elements, the promoter sequence included two ABA responsive elements (ABRE) and many other stress-response elements. The PGWB533 expression vector containing this promoter sequence was constructed with the GUS reporter gene. Histochemical staining analysis showed that the GUS reporter gene was expressed in the tissues of leaves, root, stem, flower and silique, and was especially higher in leaves. These results identified the localization and expression of the CkNCED1 gene in vivo, which suggested that CkNCED1 gene plays an important role in biosynthesis regulation of ABA. The study lay a foundation for further analysis of the gene function.

Isolation, identification and analysis of rDNA-ITS gene sequence of Fusarium culmorum from maize ear rot samples

GUO Cheng, WEI Hong-yu, GUO Man-ku, HE Su-qin, GUO Jian-guo, WANG Xiao-ming

2013, 22(2):  171-177. 

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To identify pathogens of maize ear rot in Gansu province, samples were collected from 4 ecological zones in September, 2009 and the pathogens were isolated from cankered maize ear onto a standard medium. Fusarium colonies obtained were identified according to the Leisle taxonomic system after subculture and single-spore isolation. Of 271 isolates, 105 were identified as F. culmorum, contributing about 38.7% of the Fusarium isolates. The populations differed in different ecological areas, for example, F. culmorum was the dominant pathogen in Longdong and Longnan ecological areas, where its isolation frequencies were 52.0% and 55.4% respectively. The pathogenicity of F. culmorum was tested according to Koch’s Postulate using mixed isolates on maize varieties Shendan 16 and Jinsui 96832. F. culmorum was verified as pathogenic to maize ears. Three F. culmorum isolates were taken at random for sequences analysis of the rDNA-ITS gene. The PCR products of the three isolates were collected, purified, and sequenced. The sequences were aligned in GenBank. There was a very close relationship of isolates 3-1-1 with K1004 and K216, 6-4-1 and 21-2-1 with CBS122.73 downloaded from GenBank. Their maximum similarity was 99% with F. culmorum. Microsoft DNAStar was used to draw the phylogenetic tree of isolates 3-1-1, 6-4-1 and 21-2-1. This tree showed that 3-1-1 was in the same cluster as the K1004 while K216 isolates, 6-4-1 and 21-2-1 were in the same cluster as the CBS122.73 isolate, results that were consistent with morphological identification.

Effect of exogenous nitric oxide on seedling growth and physiological characteristics of maize seedlings under cadmium stress

WANG Fang, CHANG Pan-pan, CHEN Yong-ping, PENG Yun-ling, FANG Yong-feng, WANG Han-ning

2013, 22(2):  178-186. 

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The present study was conducted in pot to investigate the effects of exogenous nitric oxide (NO) on the membrane lipid permeability, osmotic adjustment substances, antioxidant enzyme activities and chlorophyll content of maize seedling under cadmium stress. The results showed that: compared with the CK, under 100 mg/L Cd²⁺ stress, proline and chlorophyll content were decreased, the accumulation of soluble protein and soluble sugar content were slowly accumulated, and the antioxidant enzymes activities were decreased, but MDA content, O₂^-·generation rate and membrane permeability were increased. Compared with 100 mg/L Cd, 100 μmol/L SNP (sodium nitroprusside)significantly increased biomass amoun and improved the activity of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), increased the content of chlorophyll and proline (Pro), and promoted the accumulation of soluble sugar and soluble protein content, but reduced MDA content, the rate of accumulation of O₂^-·and cell membrane permeability. The results indicated that exogenous nitric oxide had a significantly effect on the growth of seedlings under 100 mg/L Cd²⁺ stress, and enhanced the resistance of maize seedling to Cd toxicity.

Effects of heavy metals and saline-alkali on seedlings growth, physiological-biochemical of Oryehophragmus violaeeus

ZHANG Xiao-ai, LI Ming-yang, WANG Zhi-hui, TANG Hao-ruo, ZHANG Xin-quan, ZUO Jing

2013, 22(2):  187-194. 

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The aim was to study on effects of heavy metals and saline-alkali on seedlings growth, physiological-biochemical of Oryehophragmus violaeeus. The results showed that relative electrolyte leakage, the content of soluble sugar and the content of Pro all increased with increased heavy metals and saline-alkali conditions, the total biomass decreased with increased heavy metals and saline-alkali conditions, but the content of MDA initially increased and then decreased. The activities of superoxide dismutase, peroxidase increased with increased heavy metals and saline-alkali conditions, and evidently higher than the control. The effect of heavy metals and saline-alkali stress on photosynthetic pigment content, in the leaf was assessed. With an increase in heavy metals and saline-alkali concentration, the chlorophyll and carotenoid contents decreased gradually, but the carotenoid contents decreased morn. The seedlings of O. violaeeus is with resistance against light combined stresses of salt-alkali and Pb (500 mg/L), and the stress patience of vane is greater than the root.

Germination responses of three medicinal licorices to saline environments and their suitable ecological regions

LU Jia-hui, LV Xin, WU Ling, LI Xue-yu

2013, 22(2):  195-202. 

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To make known the salt tolerance and suitable ecological regions of Glycyrrhiza inflata, Glycyrrhiza uralensis and Glycyrrhiza glabra from Xinjiang, the seeds of three species were salt stress treated using Na₂SO₄, NaCl and NaHCO₃ at different concentrations to compare their germination responses, salt tolerance and suitable ecological regions. The germination percentage, mean germination days, germination energy, length of plumular axis, germination recovery percentage of three medicinal licorices were recorded. Germination percentage, relative vigor index and length of plumular axis of three species obviously declined with increased salinity. Germinate time prolonged under high salinity stress. The sequence of salt injury level of seed was NaHCO₃>Na₂SO₄>NaCl. There was a significant difference of salt tolerance threshold among three species. G. inflata exhibited greater germination ability under salt stress than G. uralensis and G. glabra. So it is suitable planted in the soil mainly with chloride-sulfate containing 0-1.3% salt. The NaHCO₃ tolerance of G. glabra was the highest and can be planted in the abandoned saline land containing NaHCO₃. The slat tolerance of G. uralensis was the weakest. Therefore, the optimum salt concentration for G. uralensis was 0-0.7%.

Effect of Na and Si interactions on the drought resistance of Nitrarial tangutorum

DUAN Jiao-jiao, YANG Zi-hui, KANG Jian-jun, YU Jian-long, WANG Suo-min

2013, 22(2):  203-210. 

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The effects on growth and drought resistance of potted Nitrarial tangutorum treated with different concentrations of NaCl and Na₂SiO₃ were studied. Growth of N. tangutorum was promoted and drought resistance improved by 1.2 g/kg NaCl alone or a 0.3 g/kg NaCl+0.72 g/kg Na₂SiO₃ combination. Compared with the control, application of NaCl alone increased plant height, root length and dry weight by 47%, 25% and 236%, respectively. Application of the NaCl/Na₂SiO₃ combination effectively promoted growth and improved drought resistance of N. tangutorum more than the NaCl treatment. Compared with the NaCl treatment, the combination treatment increased plant height, root length and dry weight by 81%, 43% and 193%, respectively. It is suggested that moderate levels of Na and Si combinations could more effectively promote growth and improve drought resistance of N. tangutorum than the application of NaCl alone.

Effects of salt stress on the growth and osmotica accumulation of Coleus blumei

LIU Ai-rong, ZHANG Yuan-bing, ZHONG Ze-hua, WU Xia, ZHANG Ming

2013, 22(2):  211-218. 

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Potted Coleus blumei plants were treated with NaCl concentrations of 0 (control), 10, 50,100,150,or 200 mmol/L, and the effect of salt stress on growth, water status and osmotica accumulation were studied. Compared with the control, as NaCl concentration increased, the fresh weight, dry weight, water content and water potential decreased, while Na⁺, proline, soluble sugar content showed an upward trend. The contents of K⁺, Ca²⁺, Mg²⁺, NO₃^- were initially increased but then decreased, while free amino acid content showed the opposite trend. The results of high-performance liquid chromatography (HPLC) showed that the change rates of eight organic acids differed from each other. Synthetic analysis indicated that NaCl stress inhibited the growth of C. blumei, and the inhibitory effect on growth and water stress were enhanced as NaCl concentration increased. Under low salinity stress C. blumei accumulated the osmotica of inorganic ions such as Na⁺, Ca²⁺, Mg²⁺, NO₃^- etc, and organic matter such as proline, soluble sugar, ethanol acid, malonic acid, α-ketoglutarate and citric acid to adjust osmotic stress. To adjust osmotic stress at high salinities it accumulated osmotica such as Na⁺, proline, soluble sugar, free amino acid, malic acid, succinic acid, oxalic acid, glycolic acid and malonic acid. Therefore C. blumei accumulated different osmotica to adapt to osmotic stress under different NaCl salinity stresses.

Physiological responses of Ocimum basilicum to seawater stress

NING Jian-feng, ZOU Xian-zhong, YANG Shao-hai, SUN Li-li, LUO Wen-jian, CHEN Yong, WU Jin-long,WEI Lan

2013, 22(2):  219-226. 

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Basil (Ocimum basilicum) seedlings were subjected to 0, 5%, 10%, 20%, 30% and 40% seawater under netting house conditions. Increasing seawater concentration led to considerable reduction in plant growth rate and dry mass accumulation. However, root growth was not affected even by treatment with 30% seawater. High salinity (30% and 40% seawater) caused significant increases of soluble sugar and proline contents as well as leaf water use efficiency, whereas photosynthesis was inhibited mainly due to stomatal restriction. Accumulation of Na⁺ was correlated with a decline of Ca²⁺ and K⁺ in stems, roots or both. However, contents of K⁺ and Ca²⁺ in leaves increased or remained relatively unchanged with increasing salt levels. In plants stressed by salinity, Na⁺ were partitioned mainly in roots (57.1%-64.6% of the total) and more than 50% of the K⁺ and Ca²⁺ were stored in leaves. In addition, seawater stress decreased the K⁺/Na⁺ and Ca²⁺/Na⁺ in this species, although the higher K⁺/Na⁺ and Ca²⁺/Na⁺ were observed in leaves rather than in roots and stems. The K⁺/Na⁺ was greater than three even when subjected to 40% seawater. These results suggest that salt tolerance of basil plants might be associated with the compartmentalisation of Na⁺ in roots and the balance of K⁺, Na⁺ and Ca²⁺ in leaves as well as the osmotic adjustment with soluble sugar and proline under conditions of high salinity.

Cold-tolerance of 5 species of Juncao under low temperature stress

LIN Xing-sheng, LIN Zhan-xi, LIN Dong-mei, LIN Hui, LUO Hai-ling, HU Ying-ping, LIN Chun-mei, ZHU Chao-zhi

2013, 22(2):  227-234. 

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To select excellent Juncao species with high cold-resistance, 5 species of Juncao including Arundo sp., Arundo donax, Pennisetum sp., Pennisetum purpureum and Echinochloa crusgalli were taken as test materials and treated at 3, 0, -5, -10, -15, -20℃. Electrolyte leakage, malondialdehyde content and soluble sugar content, activity of superoxide dismutase, peroxidase, catalase and the mortality rate after recovery test were determined to detect cold resistance of the 5 species. The semi-lethal temperatures (LT₅₀) of Arundo sp., A. donax, Pennisetum sp., P. purpureum and E. crusgalli were -12.05, -21.28, 0.69, 0.18, -1.98℃ respectively. The cold-resistance of the 5 Juncao species was evaluated mathematically as A. donax >Arundo sp.>E. crusgalli>P. purpureum>Pennisetum sp., which is in accord with the results after the recovery test from low temperature stress.

Effects of different slow/controlled release nitrogen fertilizer on tall fescue turf growth and nitrogen volatilization

GU Jia-lin, BIAN Xiu-ju, XU Kai, ZHANG Dong-lei, ZHU Wen, LIU Bao-cun, ZHAO Tong-ke, FANG Rui-yuan, CAO Bing, ZOU Guo-yuan

2013, 22(2):  235-242. 

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Field experiments were conducted to study the effects of two kinds of macromolecule polymer coated urea that the nitrogen release period were 30 and 60 days (PCU30,PCU60), sulfur coated urea(SCU), urea mixed with nitrification inhibitor (UI) and urea(U) on grass growth, nitrogen uptake, ammonia and N₂O volatilization of fertilizer in tall fescue turf. Results showed that application of fertilizer such as PCU30,PCU60,SCU in spring and autumn at total rate of 260 kg/hm² per year could meet nitrogen requirement of grass normal growth. Meanwhile, the clipping yields and nitrogen uptake of those treatments were all significantly higher than U treatment at same N rate in one year with four times application. In terms of gaseous nitrogen loss, ammonia volatilization from UI was 44.42 kg/hm², which was significantly higher than other treatments. But N₂O emission of this treatment was 6.46 kg/hm², significantly lower than others. The ammonia volatilization of PCU30, PCU60 and SCU treatments were 17.67, 13.59 and 18.54 kg/hm² and the N₂O emissions were 8.14, 6.92 and 9.91 kg/hm² respectively. But all of them were significantly lower than the U treatment. Considering integrated factors, PCU60 should be taken as a suitable fertilizer on tall turf grass with twice application in spring and autumn for a year, which could increase nitrogen use efficiency and reduce nitrogen volatilization, showing an outstanding ecological and environmental benefit.

Humulus scandens gender differences in response to water stress in the vegetative growth stage

LIU Jin-ping, DUAN Jing

2013, 22(2):  243-249. 

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Humulus scandens in the vegetative growth stage was treated with the drought stress of four water gradients. When the sex could be identified, some indicators of single male and female plants, including the quantitative traits of components (root, stem, leaves), fresh weight, hay weight, and the proportion of component to total biomass, were measured and analyzed. H. scandens responded to water stress by significantly shortening the duration of vegetative growth. Male plants were more sensitive to the lack of water than female plants. Response to water stress was in the order roots, leaves, and stems. Root moisture content was reduced to meet the needs of stems and leaves to water. Meanwhile, the plant reduced the consumption of water by reducing the number of leaves and branches and by narrowing leaf area and stem length. These indicators (including total leaf area, branch, length and volume of stem, length and volume of root) were lower on male than on female plants. Water had a highly significant effect on fresh weight and hay weight of each component. Sex significantly affected only the biomass of roots. The total biomass of male plants was significant lower than that of female plants, but there was no difference between them in the distribution of each component of the biomass. H. scandens responded to water stress by reducing investment in vegetative growth and quickly switching into reproductive growth, which laid the foundation for reproduction and expansion of the population.

A study on physiological characteristics and comparison of salt tolerance of two Medicago sativa at the seedling stage

LIU Jing, CAI Hua, LIU Ying, ZHU Yan-ming, JI Wei, BAI Xi

2013, 22(2):  250-256. 

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The salt tolerance of Medicago sativa cv. Zhaodong and M. sativa cv. Nongjing No.1 and their physiological responses under salt stress were studied in seedlings cultured in 1/2 Hogland solution supplied with NaCl at concentrations of 0, 50, 100, 200, 300 or 400 mmol/L. Salt injury was measured after the treatment. The content of malondialdehyde (MDA), chlorophyll, proline before and after 3, 6, 9, 12, 15 and 21 days of salt stress were measured and analyzed. The salt tolerance of the two species was comprehensively evaluated by fuzzy subordinate function. There was no significant effect on the growth of two M. sativa at low concentrations of NaCl, showing they had a certain salt tolerance ability. The content of MDA increased with an increase of NaCl concentration. While under the stress of 200 and 300 mmol/L, the content of MDA increased initially then decreased, and then increased again after a prolonged time. With the concentration and duration of NaCl stress increasing, salt injury increased, the content of chlorophyll reduced, and the proline content was considerably increased. However, the accumulation of proline was not entirely consistent with salt-tolerant performance. The results of a comprehensive evaluation showed that the salt tolerance of M. sativa cv. Nongjing No.1 was higher than that of M. sativa cv. Zhaodong under the stress of 100 and 200 mmol/L NaCl, while under the treatment of 300 and 400 mmol/L, the salt tolerance of M. sativa cv. Zhaodong was higher than that of M. sativa cv. Nongjing No.1.

Physiological responses of white clover by different leaf types associated with anti-oxidative enzyme protection and osmotic adjustment under drought stress

LI Zhou,PENG Yan,SU Xing-yuan

2013, 22(2):  257-263. 

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Mechanisms of drought tolerance were studied in large-leaved and small-leaved white clovers by measuring physiological changes, including relative water content, electrolyte leakage, malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), ornithine aminotransferase (OAT) and osmotic adjustment substances (soluble sugar, free proline and betaine), under drought stress and rewatering. With an extension of drought stress, relative water content of the two materials decreased, while electrolyte leakage and MDA content increased. At the same time, SOD and CAT activities initially increased but then decreased and there was a sharp rise in OAT activity and in content of osmotic adjustment substances. Under drought stress, significantly higher relative water content, cell membrane stability, content of osmotic adjustment substances and activities of SOD, CAT and OAT as well as lower lipid peroxidation level were found in the small-leaved clover leaves compared with those of the large-leaved clover. After re-watering, there were varying degrees of recovery in the two leaf types of white clover, but overall the small-leaved white clover recovered better.

A study on photosynthetic characteristics and growth and development of Iris japonica under different illumination

CAI Shi-zhen, LI Xi, PAN Yuan-zhi, LI Jing, HU Ting-xing, YE Chong

2013, 22(2):  264-272. 

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Adaptability of Iris japonica under different illuminations was studied with the photosynthetic characteristics measured with a Li-6400 photosynthesis system. The Chl a/Chl b, net photosynthetic rate, stomatal conductance, transpiration rate and intercellular CO₂ concentration decreased with less light on the plants, and the light compensation point, dark respiration rate, the CO₂ compensation point also decreased, but the carboxylation efficiency increased as a mechanism of physiological adaptability to light decreasing. The adaptability to light was wide because the light compensation point was 5.18-12.05 μmol/(m²·s) and the light saturation point was higher (about 1 000 μmol/m²·s); the CO₂ compensation point was 54.84-58.45 μmol/mol and the CO₂ saturation point was about 970 μmol/mol; the plants under bamboo forest had bigger leaf area and better flowering than that of other community patterns, but the plants could grow under the three community patterns.

Photosynthetic and physiological characteristics of introduced plants at the desert-oasis ecotone

LUO Wei-cheng, ZENG Fan-jiang, LIU Bo, ZHANG Li-gang, LIU Zhen, SONG Cong, PENG Shou-lan, PENG Hui-qing

2013, 22(2):  273-280. 

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To explore adaptability of adventitious plants to extreme arid regions, we studied the photosynthesis characteristics and water potential of three plant species (Xanthoceras sorbifolia, Ziziphus jujuba and Berberis thunbergii) in the natural conditions of the desert-oasis transitional area of the Cele oasis on the southern fringe of the Taklamakan Desert.1) The three plant species showed similar light response curves: the net photosynthetic rate (P_n) increased initially but then decreased. The light saturation point (LSP) of X. sorbifolia and B. thunbergii were significantly higher than that of Z. jujuba (P<0.01), while the P_nmax and R_d of B. thunbergii were both higher than those of X. sorbifolia and Z. jujuba. These results indicated that X. sorbifolia and B. thunbergii can use glare light efficiently for photosynthesis, and B. thunbergii has the advantages of higher photosynthetic efficiency and stronger ability to withstand stress. 2) The content of chl and MDA of X. sorbifolia were significantly higher than those of the other two species (P<0.05), but the soluble sugar contents of the three species were not significantly different (P＞0.05). The Pro content of B. thunbergii was significantly higher than that of the other two species (P<0.01). 3) The X. sorbifolia had the highest water potential in three plants (P<0.01), so B. thunbergii and Z. jujuba have stronger water uptake ability. In summary, the trend of photosynthetic parameters and physiological indicators are not in complete accord; this may be due to individual differences between the species, so in order to select the most suitable adventitious plants in the oasis-desert transitional zone, further research is needed.

Effects of defoliation disturbance of aboveground biomass on photochemical process of reforested Calligonum caput-medusae saplings in arid desert

ZHU Cheng-gang, LI Wei-hong, MA Jian-xin, MA Xiao-dong

2013, 22(2):  281-289. 

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The effect of artificial disturbance on aboveground biomass of two years old Calligonum caput-medusae saplings was studied using different disturbance intensity (CK, 30%, 50% and 70%) and assessiing photochemical processes in PSⅡ of reforested shrub saplings. Saplings in the 30% disturbed group had the highest photochemical efficiency of PSⅡ and photosynthetic capacity. Most of the surplus absorbed energy by PSⅡ of experimental saplings could be dissipated as heat when the fraction of absorbed light utilized in PSⅡ photochemistry was inhibited, thus the excess excitation energy maintained a stable status. The saplings under high intensity disturbance could maintain the normal function of PSⅡ by series regulation and photoprotection mechanisms. However, high intensity disturbance of aboveground biomass (more than 50%) reduced the photosynthetic capacity, electron transport rate and the efficiency and activity of PSⅡ thus inhibiting the growth of saplings.

Review of grassland management practices for carbon sequestration

ZHANG Ying-jun, YANG Gao-wen, LIU Nan, CHANG Shu-juan, WANG Xiao-ya

2013, 22(2):  290-299. 

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About 400 million ha grassland in China is a large potential carbon sink. However, grassland carbon sequestration is not fully understood. This paper reviews the effects of meteorological factors (CO₂, temperature and rainfall change), grassland management (grazing, native grassland conversion to cropland, mowing, fertilization, irrigation, reseeding, abandoned cropland, exclosure, establishment of artificial grassland and ploughing), and degradation on soil carbon content, to guide grassland management for carbon sequestration. Changes of temperature and precipitation play different roles in the function of grassland carbon sequestration, which should be taken into account in grassland management. Degraded grassland with low productivity and soil organic matter content and a worse soil physical and chemical environment has great carbon sequestration potential. Appropriate grassland management measures will greatly improve soil organic carbon. One report suggests that the application of exclosure in degraded grassland in China could sequester over 12.01 Tg C/year. Heavy grazing can reduce carbon sequestration due to changing grassland plant community diversity, net primary productivity reduction, lower litter production and nitrogen limitation in soil. Proper grazing management has been estimated to increase soil carbon storage. Native grassland conversion to cropland has caused negative carbon sequestration, as a result of soil erosion, soil organic matter decomposition and lower litter production. Because high mowing intensity reduced soil organic matter, proper mowing height and frequency, application of manure and fertilizer to balance nutrient loss was needed on hay grassland. Fertilization, reseeding, ploughing and irrigation increased soil organic matter storage by promoting revegetation and net primary productivity. Abandoned cropland and exclosure associated with fertilization and reseeding could promote restoration and soil nutrient content, and increase carbon sequestration efficiency. Carbon sequestration capability of forage was: mixed perennial legume and grass＞legume＞perennial grass＞annual grass.

Rural-urban migration and its effects on social and economic development in China: a review

LI Li-hua, TANG Zeng

2013, 22(2):  300-306. 

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Rural-urban migration is inevitable in Chinese developmental process of urbanization and industrialization. Research related in this field had been undertaken both in China and internationally. This paper reviews the research progress on rural-urban migration in China, especially its impacts on the farmers and the agricultural sector. We conclude that the migration of rural labor may cause slight adverse impacts on agriculture in some areas. But for long run, the migration could increase farmers’ income and promote the development of agriculture, and helping solving the problems existed in the agricultural sector and improving farmers’ living standard. It is the inevitable way for Chinese future development. Areas for future research are also suggested.

Comparative analysis on gas exchange characteristics of four geographical provenances of Nitraria tangutorum

CHONG Pei-fang, SU Shi-ping, GAO Ming, LI Yi, SUN Zhao-cheng

2013, 22(2):  307-312. 

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Photosynthesis is one of the important activities which affect plant growth. The open gas exchange system, Locpro Portable Photosynthesis System, was used to study the change in daily photosynthesis and light-response curves of four geographic provenances (Jinta: JT, Linze: LZ, Minqin: MQ, Jiuzhoutai: JZT) of Nitraria tangutorumon. The daily change of net photosynthetic rate (Pn) and transpiration rate (Tr) of the four geographical provenances were single-peak curves. The Pn, stomatal conductance (Gs), water use efficiency (WUE), light saturation point (LSP) and light compensation point (LCP) of these provenances differed from Jinta, Linze and Minqin to Jiuzhoutai geographical provenance. The capacity of Jinta provenance using high intensity illumination was the highest, and its LSP was up to (1 800±68) μmol/m²·s. The capacity of Jiuzhoutai provenance using low light was higher than that of any other provenance and its LCP was (25.52±17) μmol/m²·s. The results from the four geographical provenances showed that N. tangutorum is a heliophyte and wide domain species with high adaptability to illumination. It is concluded that photosynthesis of N. tangutorum is very sensitive to variations of water because in the Jinta provenance original habitat it grew in the drought and had a high photosynthetic ability.

Alfalfa productivity and plateau characteristics in a gully region of the Loess Plateau

SHE Feng-xia, HAO Ming-de, ZANG Yi-fei

2013, 22(2):  313-317. 

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Alfalfa (Medicago sativa) plant yield and nutrient change characteristics of forage crop rotation were studied in a long-term experiment in the gully region of the Loess Plateau. The one-year Medicago yield was 8 763 kg/ha (the lowest) and the three-year Medicago yield was 12 020 kg/ha (the highest) but the four-year yield fell to 9 665 kg/ha. The N, P, K uptake (218, 11, 105 kg/ha respectively) in one-year Medicago was the lowest. The P, K uptake of three-year Medicago was the highest (23 kg/ha and 185 kg/ha respectively) and compared with one-year Medicago, the P uptake was 109.1％ higher and the K uptake was 76.2％ higher. The N uptake of four-year Medicago was the highest, about 351 kg/ha, which was 61％ higher than one-year Medicago. Soil organic matter, total nitrogen and alkali solution nitrogen content increased each year, organic matter increased form 15.60 to 18.26 g/kg, total nitrogen increased from 1.20 to 1.50 g/kg, and alkali solution nitrogen increased from 64.74 to 88.02 mg/kg. However, soil total phosphorus, available phosphorus and potassium declined each year. Total phosphorus fell from 0.86 to 0.76 g/kg, available phosphorus fell from 14.00 to 9.27 mg/kg, rapidly-available potassium fell from 70.51 to 54.35 mg/kg. Consequently, the optimum amount of potash in production fertilizer is needed to meet the needs of high quality and high production of afalfa.

Influence of straw pulp film mulching on water conservation of alpine degraded meadow in Tibet

YU Cheng-qun, WU Jun-xi, GUAN Fa-chun

2013, 22(2):  318-321. 

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The use of plastic film for mulching is very extensive because of its excellent properties and low cost. However, the massive use of plastic film poses an environmental risk, and in order to offer an alternative for water conservation of grassland soil, a comparison of straw pulp film and non-mulching was used to research the function of film in the conservation of soil water in alpine degraded meadows of Tibet. The relative humidity at the soil surface, soil temperature, soil compaction and water content in the straw pulp film treatment were better than in the CK, and the water content in May and June were 22.87% and 20.21% respectively, which were significantly better than the CK (n=5, P<0.05). At the same time, soil compaction at the surface and at 5 cm were 245 and 948 kPa, significantly different (n=5, P<0.05) from the CK. Mulching with straw pulp film gave a physical insulation to heat and obstruction to water evaporation, which helped retain soil moisture.