Table of Content

20 December 2011, Volume 20 Issue 6

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Seasonal changes in species composition, richness and the aboveground biomass of three community types in Gurbantunggut Desert, Northwestern China

TAO Ye, ZHANG Yuan-ming

2011, 20(6):  1-11. 

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Desert zones, accounted for approx. 18.5% of the total land area, was the important component of the land ecosystem. Desert ecosystem was characterized by low biodiversity and low stability, so it was easily disturbed by external forces, and it was difficult to recover. The structure and species composition of a community were the result of community succession, and they were closely relevant to the stability of ecosystem. Biomass was an important carrier of material cycle (carbon cycle) of ecosystem, it was an expression of the productivity, also was a key index evaluating the structure and function of ecosystem. Thus, the study on biomass in desert areas was very important for understanding the productivity and capacity of desert ecosystems. In this study, three types of widely distributed plant communities in Gurbantunggut Desert, Northwestern China were chosen: 36 Ephedra distachya communities, 28 Seriphidium terrae-albae communities and 13 Artemisia songarica communities. Vegetation investigation was conducted two times (seasons) in early summer and early autumn, respectively, to get the data of species composition and species richness. Then the standing aboveground biomass of herbs was gained by cutting at the ground level, and the biomass of shrubs by estimating models. The aims were to explore the seasonal changes in species composition and species richness, and to compare the aboveground biomass of different life-forms and to understand the relationship between biomass and richness of herbs in different seasons. The numbers of families and species in E. distachya and S. terrae-albae communities were more than those in A. songarica communities in early summer, whereas the numbers reduced greatly in all the three communities in early autumn. There were five life-forms in summer, and the ephemeral plant had most species. In autumn, the ephemeral and ephemeroid plants disappeared, and there were only three life-forms left, and the annual plant had most species at this time. The richness value of each community types in summer was more than that in autumn. Species richness of A. songarica communities in summer was significantly higher than those of E. distachya and S. terrae-albae communities; while in autumn, there was no difference between the three community types. In each community types, species richness in summer was positively correlated with that in autumn, indicating the structural stability of desert communities. The aboveground biomass of herbs (0.67-6.99 g/m²) was slightly more than that (0.89-4.2 g/m²) in autumn. The total aboveground biomasses of three types of communities were 73.19, 85.38 and 54.21 g/m², respectively; and the three constructive species accounted for 86.03%, 84.07% and 89.65%, respectively; while the percentages of herbs were all less than 5%. There were “Single-hump Type” relationships between herbaceous richness and their aboveground biomass both in summer and autumn, indicating highest richness at middle biomass. Although herbaceous biomasses were lower, the time crisscross of short vegetated and long vegetated plants showed an important ecological significance in maintaining biodiversity and surface stability of desert ecosystem. Totally, compared with other deserts in similar latitude in China, the three desert communities in Gurbantunggut Desert had the characteristics of obviously seasonal changes in species composition and richness, but low biomass.

Evaluation of economic benefits and ecological values of cellulosic bioenergy grasses in Beijing suburban areas

HOU Xin-cun, FAN Xi-feng, WU Ju-ying, ZUO Hai-tao

2011, 20(6):  12-17. 

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The well-known biomass material, cellulosic bioenergy grasses such as switchgrass (Panicum virgatum), silverreed (Triarrhena sacchariflora) and giantreed (Arundo donax), are important bioenergy plant resources with great development potential. In this research, the evaluation of economic benefits and ecological values was employed in the entire process from the farming culture of cellulosic bioenergy grasses to the production of cellulosic ethanol. During the production of cellulosic ethanol from the biomass of these grasses, the economic benefits were 4 147.85, 1 185.08 and 2 019.76 yuan RMB per tonne cellulosic ethanol for the three grasses respectively, and from an economic point of view, switchgrass is economically optimal, followed by giantreed, and then silverreed. The ecological value of air purification was 4 639.28, 4 351.25 and 4 320.39 yuan RMB per tonne, respectively, and from an ecological point of view, switchgrass is ecologically optimal, followed by silverreed, and then giantreed. The potential for CO₂ fixation of switchgrass, silverreed and giantreed are huge and have a positive effect on the reduction of CO₂ concentration, greenhouse gasses, and the accumulation of soil carbon.

Spatial-temporal distribution of the ecological service value and NPP of cultivated land on Longdong Loess Plateau

LI Guang, HUANG Gao-bao, WANG Qi, WANG Xing-tang, GAO Zhen-ni, LIU Cheng-zhong

2011, 20(6):  18-25. 

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The heterogeneity in spatial-temporal scale of the net primary productivity (NPP) and ecological service value was studied to keep a healthy ecological system of cultivated land by using methods related to the ecological system service and productivity assessment. The changes in NPP and the unit area value of ecological service were not distinct with the total increasing from 1997-2005. The spatial distribution of NPP and ecological service value was very obvious and divided into the lower value in the northwest area and the higher value in the southeast area. The unit area value of ecological service was about 10.2×10⁴ yuan/(ha·a) and NPP was about 5.04 t/(ha·a) in the southeast area, while in the northwest area, they were 7.7×10⁴ yuan/(ha·a) and 3.54 t/(ha·a) respectively. The NPP and ecological service value would be improved by using precipitation resources with rational and high efficiency under the conditions of optimal crop layout and adjusted plant structure.

Changes in landscape patterns and the driving force in the Eastern Qilian Mountains

LIU Jing, LIU Xue-lu, WANG Zhe-feng

2011, 20(6):  26-33. 

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Based on the techniques of RS & GIS and methods of landscape ecology, changes in landscape patterns and the driving force in the Eastern Qilian Mountains were analyzed. 1) At the patch level, the research area landscape was a grain grade structure in 1994 and 2008. There were large numbers, but a small area of mini- and small-patches while in contrast, there were few middle-, large- and huge-patches but they occupied a large area. There were great changes in the Eastern Qilian Mountains landscape from 1994 to 2008. The areas of forest, shrub and grassland remained at 78.2%, 66.7% and 86.3% of the original area respectively, and 28.1% of the shrub area came from the forest landscape. Additionally, 4.8% of the original grassland area and 12.7% of the original snow area had degenerated into bare land, and there was a dramatic transformation between forests and shrubs, snow and bare areas. The shape of patches of forest, snow and water became more simple and regularized. 2) The analysis of landscape diversity showed that evenness and fragmentation indexes of the Eastern Qilian Mountains in 2008 increased compared with those in 1994, while landscape dominance and isolation indexes decreased. The overall level of landscape diversity and heterogeneity increased, the dominant role of main plaque control decreased in the landscape which developed towards diversification and homogenization. 3) Natural factors were the main reason for temperature rise and the reduction of snow area, while precipitation increasingly influenced the decline in water area. Human factors, especially excessive logging, was fundamental for the reduction of forest area and for the degradation to shrubland.

Analysis of the nitrogen uptake and utilization efficiency and N fertilizer residual effect in the wheat-maize-soybean and wheat-maize-sweet potato relay strip intercropping

YONG Tai-wen, XIANG Da-bing, ZHANG Jing, WAN Yan, LIU Wei-guo, YANG Wen-yu

2011, 20(6):  34-44. 

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The aim of this paper was to study the mechanisms of interspecific nitrogen facilitation and transfer in the relay strip intercropping systems of “wheat/maize/soybean” and “wheat/maize/sweet potato”. The methods of root barrier and ¹⁵N-isotope dilution were used to investigate the nitrogen transfer, nitrogen uptake and residual effect in the two relay strip intercropping systems. Comparing the no barrier with solid barrier, the results showed that in-season ¹⁵N uptake and ¹⁵N recovery efficiency of wheat increased remarkably, and ¹⁵N% abundance left in soil and total N content reduced obviously. In the “wheat/maize/soybean” system, the in-season ¹⁵N uptake and ¹⁵N recovery efficiency, ¹⁵N% abundance left in soil and total N content of maize with no barrier increased by 25.16%, 25.16%, 13.89% and 10.15%. But in the “wheat/maize/sweet potato” system, the value of above indices reduced by 15.98%, 15.99%, 17.37% and 5.19%. For soybean, the in-season ¹⁵N uptake and ¹⁵N recovery efficiency, ¹⁵N% abundance left in soil reduced, the soil total N content increased by 3.03%. For sweet potato, the in-season ¹⁵N uptake and ¹⁵N recovery efficiency increased, ¹⁵N% abundance left in soil and total N content reduced by 0.91% and 4.95%. In the “wheat/maize/soybean” system, the ¹⁵N uptake and ¹⁵N recovery efficiency of wheat and maize obtained from previous wheat, maize and soybean were higher than that of the “wheat/maize/sweet potato” system. The ¹⁵N uptake and ¹⁵N recovery efficiency of soybean obtained from previous wheat or maize were lower than that of sweet potato, but that from previous soybean was higher than that from previous sweet potato. The “wheat/maize/soybean” system was more beneficial to increase annual nitrogen uptake, nitrogen residual effect and maintaining soil fertility.

Inhibitory effect of Trifolium pratense on the growth of Lactuca sativa seedlings

XU Rui, LIU Quan, YAN Zhi-qiang, JIN Hui, CUI Hai-yan, PU Xun, QIN Bo

2011, 20(6):  45-51. 

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The inhibitory effects on Lactuca sativa of the root extracts and fractions prepared with different solvents from Trifolium pratense were tested and compared by living-bioassay methods. The ethanol extract showed a significant inhibitory effect on the germination and growth of L. sativa seeds and seedlings. The chloroform and ethylacetate extracts of the root showed stronger inhibitory effects and were determined as the effective phytotoxic fractions of T. pratense. The bioactivity-driven fractionation of the chloroform extract led to the purification of a flavonoid glycoside, which was characterized (mainly by NMR spectral elucidation) as (6aR, 11aR)-trifolirhizin. This compound led to significant reductions of fresh weight and root length of L. sativa seedlings and stimulated the activity of SOD and CAT at lower concentrations but inhibited the activity of the enzymes at higher concentrations. Reactive oxygen species increased and the peroxidation of membrane lipid was induced by (6aR, 11aR)-trifolirhizin at higher concentrations to affect the related physiological processes for the growth and development of plants.

Effects of salt stress on the growth, antioxidant ability and salt stress protein of Calendula officinalis

LIU Ai-rong, ZHANG Yuan-bing, FANG Yuan-yuan, LI Wei, CHEN Zhi-yang

2011, 20(6):  52-59. 

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Calendula officinalis plants were treated with NaCl at different concentrations (0, 10, 50, 100, 200 and 300 mmol/L), while fresh and dry weights, chlorophyll content, root dehydrogenase activity, Na⁺ and K⁺ content, activity of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), MDA content, and cell membrane permeability were determined. Polyacrylamide gel electrophoresis (PAGE) of POD isoenzyme and SDS-PAGE of salt stress protein were done. Compared with the control, fresh and dry weight, chrolophyll content, SOD and POD activity initially increased but then decreased, while MDA content did the opposite. Na⁺ content and cell membrane permeability increased, while root dehydrogenase activity, K⁺ content and CAT activity decreased. Eight bands were detected through PAGE of POD isoenzyme. Only salt stress protein was induced under 10 mmol/L NaCl stress. Therefore, 10 mmol/L NaCl treatment promoted the growth of C. officinalis but the inhibitory effects on C. officinalis growth were enhanced as NaCl concentrations increased. The synthesis analysis showed that the salt tolerance threshold of Calendula officinalis was 100 mmol/L.

Effect on the photosynthetic characteristics of Cd uptake and translocation in seedlings of two Helianthus tuberosus varieties

CHEN Liang, LONG Xiao-hua, ZHENG Xiao-tao, LIU Zhao-pu

2011, 20(6):  60-67. 

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The photosynthetic characteristics and Cd accumulating capacities of two Helianthus tuberosus varieties (NY5, NY2) at different Cd concentrations (0, 5, 25, 50, 100, and 200 mg/L), were investigated for the potential use of H. tuberosus as a candidate for phytoremediation of Cd-contaminated soils. 1) The biomass of NY5 and NY2 were significantly reduced by Cd stress, but the reduction was less for NY5 than for NY2. 2) The chlorophyll content of NY5 was lowest in the 100 mg/L Cd treatment, while for NY2, the lowest value was observed in the 25 mg/L Cd treatment. The carotenoids content of NY5 under Cd stress was higher than that of the control, while the opposite was observed for NY2. 3) With the increase in Cd concentration, net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) significantly decreased, but the intercellular CO₂ concentration (Ci) was relatively stable. Water use efficiency (WUE) and stomatal limitation (Ls) of NY5 showed similar change trend under Cd stress with the lowest value observed at 50 mg/L Cd, while for NY2, there was little change. 4) NY5 and NY2 had Cd tolerance and accumulation capacity at high concentrations of Cd stress, but the capacity of NY5 was greater than that of NY2. H. tuberosus may therefore be an excellent candidate for phytoremediation on Cd-contaminated soils, and NY5 may be better than NY2.

Dynamics of soil salt content in the rhizosphere soils of four salt-tolerant forage species

DONG Li-ping, LI Xian-ting, CAO Jing, SU Yi-bing, DAI Li-lan, CHU Jin-peng

2011, 20(6):  68-76. 

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A rhizobag experiment to investigate the dynamics of pH and salt ions in the rhizosphere and bulk soils was conducted on calcareous salt-affected soils using four salt-tolerant forage species in the Yin Da irrigation district, Yongdeng County of Gansu province. The pH, EC and concentrations of six major salt ions in the soils of tested forage species decreased with an extension of incubation time. There was a significantly lower pH in rhizosphere soils than in corresponding bulk soils during the growth period of all tested plants, such as Xinjiangdaye (Medicago sativa cv. Xinjiangdaye), Zhonglan No.1 (M.sativa cv. Zhonglan No.1), Sesbania cannabina and Puccinellia chinampoensis. EC was higher in rhizosphere soils than in bulk soils for all tested plants after a 90-day growth period. The distribution of salt ions in the rhizosphere and bulk soils showed different change trends at different incubation times. Ca²⁺ and Mg²⁺ were enriched in the rhizosphere soils at different growth stages of all tested plants except Xinjiangdaye at the 90-day growth stage. At the 60-day growth stage, K⁺ concentration in the rhizosphere soils of S. cannabina decreased, but then increased at subsequent growth stages. For the other three forage species, K⁺ was in deficit in the rhizosphere soils. Na⁺ and Cl^- concentrations increased in the rhizosphere soils at different growth stages for all tested plants except Xinjiangdaye and Zhonglan No.1 at the 90-day growth stage. There were significant differences in six major salt ions between the rhizosphere and bulk soils for all tested plants at the same growth stage. The Na⁺/Ca²⁺ and Na⁺/Mg²⁺ showed a decreasing trend with an extension of incubation time. This indicated that the deficit of Na⁺ in the soils was more profound than those of Ca²⁺ and Mg²⁺, and that Na₂SO₄ and MgSO₄ were enriched in the rhizosphere soils of Xinjiangdaye, while NaCl was enriched in rhizosphere soils of the other three forage species.

Effect of soil water deficit and enhanced ultraviolet radiation on contents and crystal structure of cuticular waxes in alfalfa (Medicago sativa) leaf

GUO Yan-jun, GUO Yun-jiang, TANG Hua, LI Zhi-yan, HAN Long

2011, 20(6):  77-84. 

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Enhanced ultraviolet radiation induced by human activities widely influenced plant adaptation, which accompanied with drought stress severely reduced crop yields. In the current study, two alfalfa (Medicago sativa) cultivars with different drought resistances, Aohan (high resistance) and Sanditi (low resistance), were used to analyze the responses of leaf cuticular wax content and crystal structure, leaf water potential (LWP), and ultraviolet absorbing compounds under soil water deficit and enhanced ultraviolet radiation (UVR) stresses. The results showed that the leaf wax content in Aohan was significantly higher than that in Sanditi. Compared to well-watered plants, leaf wax content and LWP in Aohan with combined treatments of UVR and soil water deficit increased, while LWP in Sanditi changed insignificantly. This indicates that high-drought resistant cultivar might maintain higher level of LWP to control water loss by increasing wax deposition on leaf surface. Under the conditions of 0.05 W/m² UVR dose or combined treatments of UVR and soil water deficit, the platelet wax crystalloid on leaf surface of both alfalfa cultivars melted, which increased covering areas and UVR reflection rate, and thus would reduce cuticular water loss. Under 0.1 W/m² UVR dose, some crystal platelets paralleling leaf surface while vertically distributing above other crystalloid, appeared on leaf surface of Aohan, which efficiently reduced the effect of UVR on plant physiology, while the wax crystalloids of Sanditi further melted. The structure of wax crystalloids had no significant response to solely water deficit treatment. The contents of ultraviolet absorbing compounds had no significant response to enhanced UVR, indicating that the wax crystalloid structure on alfalfa leaf surface had direct defense mechanism to UVR, which partly might delay or replace the defense mechanisms from secondary metabolic compound such as ultraviolet absorbing compounds.

Two strategies of cloning Medicago sativa phytochrome A and B genes

LI Ping, YANG Ling-ling, CHEN Qi-xin, SHI Ying-hua, YAN Xue-bing, CHEN Zhan-kuan, WANG Cheng-zhang

2011, 20(6):  85-92. 

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Short days are the main environmental factor leading to fall dormancy (FD) in alfalfa (Medicago sativa) which is considered to be a photoperiodic response with phytochromes as the main receptors. This study explored efficient methods for cloning phytochromes of M. sativa, including phytochrome A (PHYA) and phytochrome B (PHYB), which are the main phytochromes and have not been cloned in this species. Based on principles of comparative genomics and a bioinformatics approach, PHYA and PHYB genes were cloned by two different experimental strategies: using mRNA at the beginning and then the RACE technique, or by genomic DNA then genome walking. The sequences will be fundamental to studies of the relationship between FD in alfalfa and photoperiod. We also found thatM. truncatula could be used as a model plant in cloning unknown genes of M. sativa.

Effect of nitrogen on protective enzyme activities and lipid peroxidation in triticale genotypes with different N use efficiency

KUANG Yi, LI Ting-xuan, YU Hai-ying

2011, 20(6):  93-100. 

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To elucidate the effect of nitrogen on biomass of shoot, protective enzyme activities and lipid peroxidation in triticale leaves at different growing stages (seeding, tillering, jointing and heading), a pot experiment was carried out using four N levels (0, 0.25, 0.50 and 1.00 g N/pot) with two triticale genotypes, one of high N use efficiency (P1429186) and one of low N use efficiency (Clxt74). 1) At the same N levels, shoot biomass of P1429186 was significantly greater than that of Clxt74 at different growth stages. At the same growth stages, shoot biomass was greater when more N was supplied, and the increasing capacity of P1429186 was much greater than that of Clxt74. 2) During seeding, the activities of superxoide dismutase (SOD), peroxidase (POD), and catalase (CAT) in leaves of P1429186 were greater than in Clxt74 at the same N levels. Contrarily, malondialdehyde (MDA) content was significantly lower in P1429186 than in Clxt74. 3) Correlation analysis showed that shoot biomass had various correlations with the activities of SOD, POD, and CAT in leaves of triticale at different growth stages, and had a negative correlation with MDA content. This indicated that, the protective enzymes of P1429186 can cooperate with each other to eliminate reactive oxygen species, thereby inhibiting membrane lipid peroxidation to increase photosynthesis and yield.

Effect of moisture content on physiological characteristics of Elymus sibiricus seed under different storage temperature conditions

ZHU Ping, KONG Ling-qi, LI Gao, ZHANG Xiao-yuan, YU Xiao-na, MAO Pei-sheng

2011, 20(6):  101-108. 

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The experiments were conducted to study the influence of storage temperature on superoxide anion radical, antioxidant enzyme activities and lipid peroxidation in Elymus sibiricus seeds with different moisture content (4%, 10%, 16%, 22%, 28%, 34%, 40%), and try to explore the mechanism of seed deterioration with different moisture content. The results showed that seed germination rate decreased gradually after low and room temperature storage and germination capability of seeds with higher moisture content (16%~40%) lost significantly. The percent of dead seeds increased, SOD and MDA content generally decreased with the moisture content improved. APX (ascorbate peroxidase) and superoxide anion production rate decreased with the moisture content increasing under the low temperature. In 28% moisture content, APX and superoxide anion production rate began to rise. After stored under room temperature, APX increased in 22% moisture content, superoxide anion production rate generally declined. But in 16% moisture content, superoxide anion production rate rose dramatically and seed germination rate suddenly decreased to zero, abnormal seeds and dead seeds obviously increased. In low moisture content(4%～16%), superoxide anion radical accumulation could be the key to cause seed deterioration. But the vigor reduction of seeds with high moisture content was not related to free radical accumulation and lipid peroxidation.

A study on the causes of Iris tenuifolin dormancy and the methods for breaking dormancy

ZHANG Dan, ZHANG Jin-zheng, SUN Guo-feng, LI Xiao-dong, HE Qing

2011, 20(6):  109-117. 

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The causes of Iris tenuifolin seed dormancy were studied by the hygroscopicity of seeds, different scarification treatments and germination inhibitor tests. The embryo was not responsible for dormancy, while the seed coats and micropylar endosperm played important roles in reducing germination percentage. Additionally in the seed coats, there were polar germination inhibitors which were soluble in methanol. Sulphuric acid treatment for 60 min or cold-warm stratification (4℃/25℃) for 120 or 150 d effectively promoted germination percentage, from 0 to 51.11%, 36.67% and 40.00%, respectively, and also increased the germination index to 0.45, 0.42 and 0.51. The germination percentage was only 7.78% if the seeds were stratified at 4℃ for 150 d. The main reason why cold-warm stratification was better for germination, was that the mechanical resistance to embryo growth was considerably reduced and the growth potential of embryos was considerably enhanced. In summary, the seed of I. tenuifolin has a physiological dormancy, which is caused by both the mechanical resistance of micropylar tissue and germination inhibitors in seed coats.

Effect of winter cropping Italian ryegrass on N and P leakage from soils

XIN Guo-rong, LI Jian, YANG Zhong-yi

2011, 20(6):  118-125. 

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Based on the construction of an Italian ryegrass-rice rotation (IRR) system, the variety and dynamics of N and P loss in underground leakage water under different experimental treatments were investigated. The average loss of N and P through leakage water in the growth cycle was 115.98 kg/ha NO₃^--N, 0.828 0 kg/ha NH₄⁺-N and 0.028 5 kg/ha P under the idle field treatment (CK). Winter cropping of Italian ryegrass reduced the loss of N and P. Winter cropping Italian ryegrass with 375 kg/hm compound fertilizer, resulted in loss reductions of NO₃^--N, NH₄⁺-N and P of 49.43%, 48.59% and 24.11%, respectively, compared to the CK. Winter cropping Italian ryegrass with 750 kg/ha compound fertilizer, resulted in loss reductions of NO₃^--N and NH₄⁺-N of 38.20% and 15.57%, respectively, while the loss of P was slightly greater than that under CK.

Effects of green manure application combined with chemical fertilizers on microbial biomass C, N and nitrogen supplying characteristics of tobacco-planting soils

LI Zheng, LIU Guo-shun, JING Hai-xia, YE Xie-feng, XIE Chang-sheng, XIANG Yong-guang, ZHANG Wen-ping, YANG Chao, WANG Yong, XI Xiang-yin

2011, 20(6):  126-134. 

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In field experiments, the effects of green manure application combined with chemical fertilizers on microbial biomass C, N and nitrogen supplying characteristics of tobacco-planting soils were studied to provide a theoretical basis to study low carbon agriculture and to build resource-saving, environment-friendly agriculture and to promote the sustainable development of tobacco agriculture and the production of tobacco leaves with specific characteristics. Green manure application combined with chemical fertilizers increased soil microbial biomass C, N and soil nitrogen supplying capacity. The effects of application ratio of green manure and chemical fertilizer were different at different growth stages. In comparison with the control at different growth stages, soil microbial biomass C, N and soil urease activity were increased 7.07%-123.32%, 3.28%-157.69% and 3.13%-50.00%, respectively by green manure application. The contents of soil total nitrogen and alkalytic nitrogen increased by 22.21% and 15.42%. The dynamics of microbial biomass C and N were different at different growth stages. Microbial biomass C peaked at the rosette stage and the budding stage, while microbial biomass N peaked at the rosette stage and the topping stage. The contribution of green manure to soil microbial biomass C, N and enzyme activity was greater than that of chemical fertilizer. Green manure was a main resource of soil microbial biomass N and soil nitrogen. At the same time, green manure also played an important role in the preservation of soil nitrogen. The above results revealed green manure application could promote the activity of soil organisms, favouring the turnover of organic matter in the soil and the provision of nutrition to meet the needs of tobacco's normal growth.

Seasonal dynamics in soil microbial biomass and enzymatic activities under different alpine brushlands of the Eastern Qilian Mountains

YANG Cheng-de, LONG Rui-jun, CHEN Xiu-rong, XU Chang-lin, XUE Li

2011, 20(6):  135-142. 

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The soil microbial biomass and enzymatic activities were studied under Rhododendrons alpine brush lands (RB), Salix cupularis alpine brush lands (SB) and Dasiphoru fruticosa alpine brush lands (DB) of the Eastern Qilian Mountains in the Qinghai-Tibetan Plateau, China. The seasonal trend of soil microbial biomass carbon (SMBC) increased significantly from May to July (P<0.05), and then fell significantly from July to September (P<0.05), before increasing again until November across all three sites. However, the soil microbial biomass nitrogen (SMBN) and the soil microbial biomass phosphorus (SMBP) significantly decreased from May to September then increased again after September except that the SMBN under SB decreased from May to November. The seasonal dynamics of SMBC/soil organic matter (SOM), SMBN/soil total nitrogen (STN) and SMBP/soil total phosphorus (STP) showed similar trends to the SMBC, SMBN and SMBP, respectively. The annual mean ratio of SMBC/SMBN was 5.79-10.31: this was higher in the lower than in the upper layer. The maximum was in July and the minimum in September. Urease activities gradually increased from May to July, and then decreased after July across all three sites. The seasonal dynamics of neutral phosphatase activities (NPA) increased from May to July, but significantly (P<0.05) decreased from July to September, and then gradually increased after September at RB. At SB, the NPA gradually increased from May to November while at DB, it increased from May to September, and then decreased after September.

Main species litter decomposition and function of soil fauna in Leymus chinensis grassland

WANG Xing-li, YIN Xiu-qin, SONG Bo, XIN Wei-dong, LI Bo, MA Hong-bin

2011, 20(6):  143-149. 

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This study is on the decomposition of main species litter and the function of soil fauna in Leymus chinensis grassland. The results show that there are differences in decomposition rate both among litter species and mesh bags. Chloris virgata litter decomposes fastest, meanwhile litter in 4 and 2 mm mesh bags have higher decomposition rates than those in 0.01 mm mesh bags. For the composition of soil fauna community in litter decomposition process, Gamasida, Actinedida and Oribatida are dominant groups, while Lygaeidae, Psocidae, Cydnidae, Pseudachorutidae, Microphysidae, Isotomidae and Tubalifera are common groups. Soil fauna community has generally accelerated the rates of litter decomposition, but the contributions of macro and mesh-micro soil fauna are different. Mesh-micro soil fauna has a stronger role of promoting the litter decomposition. The pearson correlation analysis indicates there is a significant negative relationship between litter mass loss percent and diversity index of soil fauna community, while the relationship does not exist between other soil fauna community characters and litter mass loss percent.

Effect of fungal endophytes against rust disease of perennial ryegrass (Lolium perenne) on growth and physiological indices

MA Min-zhi, NAN Zhi-biao

2011, 20(6):  150-156. 

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The biological, photosynthetic and physiological characteristics of Neotyphodium endophyte-infected (E+) and endophyte-free (E-) perennial ryegrass (fairway cultivar) with Puccinia spp.infections were studied in a field experiment. The height and biomass of E+ plants were significantly higher than those of E- plants, and the loss of diseased leaves of E+ plants was significantly lower than that of E- plants irrespective of whether they were slightly or severely infected. The same response also occurred in the dwarf diseased leaves. For slight and severely affected plants, the contents of leaf relative water, soluble sugar, chlorophyll, proline, and net photosynthetic rate, transpiration rate and stomatal conductance as well as the activities of superoxide dismutase and peroxidase of E+ plants were significantly greater than those of E- plants. However, the malondialdehyde content of E+ plants was significantly lower than that of E- plants. In conclusion, endophyte infection improved rust disease resistance of perennial ryegrass under field conditions.

Isolation and identification of endogenic nitrogen-fixing bacteria in the roots of Jerusalem artichoke (Helianthus tuberosus)

MENG Xian-fa, LONG Xiao-hua, KANG Jian, WANG Xue-qing, LIU Zhao-pu

2011, 20(6):  157-163. 

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Endogenic nitrogen-fixing bacteria (ENB) from the roots of Jerusalem artichoke (Helianthus tuberosus) were isolated and identified using acetylene reduction assay (ARA) combined with gas chromatography (GC). The seven ENB strains isolated belonged to Rhizobium (2 strains), Stenotrophomonas (3 strains), Pseudomonas (1 strain) and Enterobacter (1 strain). Significant differences in nitrogenase activity were found among the ENB strains. The nitrogenase activities of two strains, cho1 and cho9, were higher than 100 nmol/(mL·h). Cho4 strain had the strongest salt-tolerance and could grow normally in condition of 7% NaCl. Five strains showed the power of phosphate solubilization and strain cho7 had the highest ability (63.84 μg/mL). All the ENB strains could excrete IAA, but there was a significant difference in the ability to do so, and strain cho2 had the highest activity (13.49 μg/mL).

Establishment of an Agrobacterium tumefaciens-mediated genetic transformation system of Lilium speciosum

CHU Jun, XU Na, ZHANG Qiang, WANG Song-hua, ZHOU Zheng-yi, JIN Guang-ming

2011, 20(6):  164-169. 

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Several factors, affecting Agrobacterium tumefaciens-mediated genetic transformations of lily were studied based on the establishment of regeneration systems. The pre-culture time of 5 days was beneficial for improving transformation frequency. Co-culture for 3 days with 100 μmol/L AS (acetosyringone) resulted not only in higher rates of transformation but also controlled the over-growth of bacteria. The 10-min bacteria infection (ABS₆₀₀= 0.8, pH=5.7) with 150 μmol/L AS was found to be the optimal selection for transgenic plantlets. It was confirmed by using gus instantaneous expression test and hpt gene PCR test that the vector was integrated into the regeneration genome of lily.

Identification of cellulose decomposing fungi strain F₁ and decomposition activity to two kinds of lawn grass litter

LU Guang-xin, CHEN Xiu-rong, YANG Cheng-de, XUE Li, LIU Wen, BIAN Jing

2011, 20(6):  170-179. 

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A fungal isolate (strain F₁) was isolated from east part of grassland soil in Qilian alpine. Taxonomic status and decomposition activity to two kinds of lawn grass litter were studied in this study. Combinated morphology with rDNA-ITS molecular biology methods, the fungus was Microdochium bolleyi. The dynamics of lignocellulolytic enzymes secreted by M. bolleyi and cell wall material(CWM) decomposition of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) litter were investigated for 42 d at 25℃ on a rotary shaker at 150 r/min in flask liquid fermentation method. 1) Insoluble cell wall material(ICWM) of two kinds of lawn grass litter significantly reduced after inoculation strain F₁ (P<0.05); 2) When two kinds of lawn grass litter acts as substrate respectively, the laccase secreted by strain F₁ appears first, followed by the cellulase enzyme and xylanase, catechol oxidase and guaiacol oxidase occurs at the latest; 3) Perennial ryegrass compared with white clover, the insoluble cell wall material (ICWM) and cell wall material (CWM) degradation rate of perennial ryegrass litter was higher (P<0.05); 4) The FPAase, CMCase, xylanase, pycocatechol oxidase and guaiacol oxidase activity except for the laccase secreted by M. bolleyi in perennial ryegrass litter were higher than those in white clover litter (P<0.05).

A test on microzyme fermentation of corn straw

HUI Wen-sen, WANG Kang-ying, SHEN Xiao-rong, LIU Hui-xia

2011, 20(6):  180-185. 

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Fermentation by yeast of corn straw at room temperature was tested. After completion of the fermentation, four nutrition indexes (CP, EE, CF and WSC) were tested and compared. When the ingredients of bran, yeast and corn straw were in the ratio 2∶2∶100, CP increased significantly by 1.93% after fermentation and EE by 0.51%. When the fermentation time was from 10-15 d, the increases were 6.49%-6.61% and 0.82%-0.95% respectively. The length of the corn straws had an obvious affect on fermentation. Fermentation was significantly increased by comminuting the straw, but this increased the cost of fermentation. If water content can be controlled within 60%-70%, the fermentation can be improved. Yeast fermentation had little effect on CF.

Effect of cutting time on the biomass production and forage quality of Lolium multiflorum

DING Cheng-long, GU Hong-ru, XU Neng-xiang, CHENG Yun-hui

2011, 20(6):  186-194. 

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In order to investigate the effect of cutting time on the yield and forage quality of Lolium multiflorum, seven varieties, one selected line and two cutting strategies were applied. The forage yield, the content of crude protein (CP), water-soluble carbohydrate (WSC), acid-detergent fiber (ADF), neutral-detergent fiber (NDF), and in vitro dry matter digestibility (IVDMD) were measured. Compared with cutting begun from April 1st, the dry matter yield of cutting begun from April 16 increased remarkable (P＜0.01). Dry matter yield increased range from 16.0% to 50.2% with different varieties. Compared with different cutting strategies, the concentration of forage CP and WSC of the early cutting is higher than that of later cutting between the same cutting time (1st, 2nd, or 3rd), but the concentration of ADF and NDF of the later cutting is higher than the early cutting between the same cutting time. The CP yields per unit area changed between two cutting strategies depending on varieties. The IVDMD of different varieties followed the same trend: 1st cutting＞2nd cutting＞3rd cutting. Between different cutting strategies, the IVDMD of early cutting is higher than the later cutting between the same cutting time (1st, 2nd, or 3rd). Considered the forage yield and quality, delaying cutting time properly can remarkably increase forage yield and digestible dry matter yield per unit area.

Effects of biological additives on the quality of water hyacinth and maize straw mixed silage

CHEN Xin-zhu, ZHUANG Yi-fen, ZHANG Jian-guo, LIAO Hui-zhen, ZHANG Wen-chang, ZHANG Zhao-yang, CHEN Qing-da

2011, 20(6):  195-202. 

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In order to investigate the effects of biological additives on the quality of mixing water hyacinth and maize stalk, four mixture ratios of water hyacinth and maize stalk at 8∶2, 7∶3, 6∶4 and 5∶5 (W8M2, W7M3, W6M4 and W5M5) were designed. In addition, no-additive, fermented green juice (FGJ), cellulase (CEL) and FGJ+CEL (MIX) were added for all materials. After ensiled for 60 days at ambient temperature, the nutritional composition were measured for each treatment. Three kinds of additives significant improved the fermentation quality of water hyacinth and maize straw mixed silages (P<0.05). FGJ and CEL also had obvious interaction. In addition, with the increase of corn straw mixture ratio, the quality of silage was improved. W5M5 was the best silage.

Effects of moisture content and additives on the quality of Agropyron elongatum silage

LIU Ling, CHEN Xin, LI Zhen, HAN Ming-ming, XU Qing-fang, HAN Jian-guo, YU Zhu, BAI Chun-sheng

2011, 20(6):  203-207. 

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The effects of moisture content and additives on the quality of Agropyron elongatum silage and the best way to ferment A. elongatum silage were investigated. Fresh or wilted A. elongatum at the seeding stage were ensiled in bags for 360 d with CK, sucrose (2%), or formic acid (6 mL/kg). The pH increased significantly in the wilted silage. The wilting treatment led to a reduction in lactic acid and ammonia nitrogen contents, but to an increase in acetic acid content. The formic acid treatment resulted in a decrease in pH and the formation of acetic acid, but an increase in lactic acid content. Adding sugar led to a decrease in silage pH and acetic acid content, but to an increase in lactate production. Wilting or adding acid or sucrose had little impact on CP, NDF, ADF, Ash, EE, nitrate, and nitrite content, and dry matter recovery of A. elongatum silage. The nitrate content decreased by 48%-53%, while nitrite content increased.

The nutrient components and ensilage fermentation quality of sweet corn stalks harvested at different times

CUI Wei-dong, DONG Zhao-xia, ZHANG Jian-guo, WEI Jian-sheng, LIN Lu-cheng, ZHANG Ming

2011, 20(6):  208-213. 

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The effect of harvest time on nutrient components and ensilage fermentation quality of sweet corn stalks in winter and summer were investigated. The stalks were harvested and ensiled on the day of ear harvest and the 3rd, 6th, 9th and 12th day after the harvest of corn ears. In winter the contents of crude protein, ether extract and nitrogen free extract in stalks were not significantly different between harvest times but the contents of water soluble carbohydrates and crude fiber in stalk harvested on the day of ear harvest were significantly greater than those harvested on the 9th day after ear harvest. The best fermentation quality was obtained when stalks were harvested on the 3rd day after the ear harvest. In summer, harvest time significantly influenced the nutrient components of stalks. The dry matter content of stalks rose significantly as the harvest time was delayed. The contents of crude protein and crude fiber in stalks were greatest on the day of ear harvest, but the contents of water soluble carbohydrates and nitrogen free extract were the lowest as was the score for silage quality. Sweet corn stalks had the best nutrient quality when harvested within 6 d after ear harvest in winter and within 9 d in summer, and had the best silage quality when harvested within 6 d in winter and during 3-9 d in summer.

A study on fatty acid components of twenty-eight forages

FENG De-qing, HUANG Qin-lou, LI Chun-yan, HUANG Xiu-sheng, ZHONG Zhen-mei

2011, 20(6):  214-218. 

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The fatty acids were determined, analyzed and compared at the same time in twenty-eight forages. Alpha linolenic acid was the most abundant fatty acid in the forage, making up to 43.78% of the fatty acids. The polyunsaturated fatty acids comprised 54.71% of the fatty acids, and 95.18% of the unsaturated fatty acids, indicating that the unsaturated fatty acids in the forage were dominated by the polyunsaturated fatty acids that had double bonds or more. In the grasses, Lolium multiflorum and Pennisetum had a high alpha linolenic acid content. In L. multiflorum the content was 69.9%, in P. purpureum cv. N51 it was 67.6%, in P. purpureum cv. Red it was 62.2%, and in P. americanum×P. purpureum it was 61.0%. There was no significant difference in the content of alpha linolenic acid between Gramineae and Leguminous forages.

Test and comprehensive assessment on the performance of 22 alfalfa varieties

CAO Hong, ZHANG Hui-ling, GAI Qiong-hui, CHEN Hong, ZHAO Man-lai

2011, 20(6):  219-229. 

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In the semi-arid area of eastern Gansu province, performance and stress-resistance testing were conducted with 22 domestic and introduced alfalfa (Medicago sativa) varieties. 1) There were no differences between varieties in breeding time in the first year, but in the next year, domestic variety and WL series became green earlier than other varieties and there were significant differences in flower budding for all varieties. The drought- and cold-resistance of most of the introduced varieties were no better than those of the domestic ones such as Gannong No.1. 2) The analysis of three-year hay production showed a 6.4%-25.2% significant increase in 14 alfalfa varieties in contrasts with the Longdong variety. The hierarchy analysis indicated that the varieties could be divided into 4 ranks based on their performance: Phabulous and Gannong No.1 were the best. 3) Some of the varieties, including Gannong No.1, Phabulous, Algonquin, Ameristand, and Amerigraze, would be suitable for wide utilization in the Qingyang area because they all easily performed with high, more stable production, drought- and cold-resistance, and higher assessment scores. The rest, including Gannong No.2, Alfaking, Xinjiang, Gannong No.3, and Sanditi, could be used in some areas according to the individual ecological conditions, variety property and utilization target.

Comparison of Stylosanthes guianensis in degraded mountain Yuanmou of the dry-hot Valley

LONG Hui-ying, HE Hua-xuan, ZHANG De, JIN Jie, SHI Liang-tao, ZHANG Ming-zhong, BAI Chang-jun

2011, 20(6):  230-236. 

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It has carried on the compared experiments for 12 Stylosanthes guianensis in degraded Mountain Yuanmou of the dry-hot Valley from 2007 to 2009. Their growth period,the biomass above the ground, leaf/stem ratio, dry/fresh ratio, the number of divarication,stub height etc.were recorded. The results showed that: 1)The best combination property of forage was S.guianensis CIAT11362, it was highest for average yield, dry yield and survival rate of three years of S.guianensis CIAT11362, whose average dry yield was 20.31 t/ha, dry seasons dry yield was 7.17 t/ha, survival rate of three years was 87.5%, it is a more drought-resistant grass, adapted to arid and semi-arid region. 2) GC1579 S.guianensis and S. guianensis reyancv No.5 are optimum integrated traits can be used as dry and hot valley to promote grass. 3) the 90089 and the West S. guianensis overall performance, though not particularly outstanding, but have the advantages which in special environment should not be ignored, they maybe ideal under the different performance requirements.

Acquisition and identification of cold-resistant somatic mutants of centipedegrass

YUAN Xue-jun, WANG Zhi-yong, ZHENG Yi-qi, LIU Jian-xiu, SHE Jian-ming

2011, 20(6):  237-244. 

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Weak cold-resistance of centipedegrass is one of the major factors limiting its wide application. This study aimed to obtain cold-resistant somatic mutants from the seed of eminent Chinese native centipedegrass selection E-126 by induction and screening at low temperature. The callus induced by seeds of centipedegrass was cultivated at 0℃ for 26 d during the process of subculture and two pieces of survival callus tissues were obtained. Strain 1 and strain 2 were obtained after survival callus subculture proliferation, differentiation, rhizogenesis and transplantation. No significant differences were found in leaf color, lamellar hair, leaf length and leaf width between strains 1and 2 and the control. LT₅₀ of strains 1 and 2 were -6.646 and -6.546 ℃, respectively, which was significantly lower than that of control plants (-5.351 ℃) and there was no significant difference between the LT₅₀ of strains 1 and 2. The results of sequence related amplified polymorphism (SRAP) markers demonstrated that there were identical characteristic bands at 110, 230 and 240 bp of centipedegrass strains 1 and 2 obtained through low temperature induction. However, no characteristic bands at 110, 230 and 240 bp were found in control plants, indicating that the somatic mutants of centipedegrass were genetically stable compared with that of control plants at a molecular level. Strains 1 and 2 could be utilized as identical strains.

Genetic diversity of Hemarthria compressa germplasms from southwestern China based on EST-SSR markers

CHEN Yong-xia, ZHANG Xin-quan, XIE Wen-gang, MA Xiao, LIU Ying

2011, 20(6):  245-253. 

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Using EST-SSR with primers from cereal crops, the genetic diversity was assessed in 40 wild Hemarthria compressa clones from southwestern China and three varieties. After amplification with 23 pairs of EST-SSR primers of Poaceae, 323 fragments were detected, of which 261 were polymorphic, accounting for 80.4% of the total. The polymorphic information content was from 0.354 to 0.500. The genetic similarity coefficient of 43 accessions ranged from 0.690 to 0.913. Clustering analysis also revealed that the clustering among tested materials was related to their geographic origins, ecological types and morphological characteristics. AMOVA (analysis of molecular variance) of five geographical groups of H. compressa revealed that 95.32% of total variance occurred within these groups and 4.68% of total variance occurred between them. It is suggested that using EST-SSR primers from cereal crops, is feasible and effective for analyzing the genetic diversity of H.compressa.

Effect of nutrition level on reproductive performance of Tan×Small Tail Han crossbred ewes

WANG Hong-bo, GUO Jiang-peng, LI Fa-di, HAO Zheng-li, YAN Ping

2011, 20(6):  254-263. 

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The effects of (Ⅰ) 0.8×NRC, (Ⅱ) 0.9×NRC and (Ⅲ) 1.0×NRC levels of metabolic energy (ME) and crude protein (CP) on reproductive performance of ewes during the late period of pregnancy (97-150 d), lactation period (30 d) and flush period (from weaning of lambs to end of the second estrus cycle) were studied. Thirty Tan×Small Tail Han crossbred ewes in lamb at the first or second conceiving stage were randomly divided into three groups (6, 5 and 7 ewes in groups Ⅰ, Ⅱ and Ⅲ respectively were used for statistical analysis). All the ewes were individually housed in pens with lamb creep. 1) During the late period of pregnancy, the postpartum weight of ewes for group Ⅰ (43.50±7.50 kg) was lower than those of groups Ⅱ and Ⅲ (47.20±2.12 and 54.79±6.72 kg). The average daily gain (ADG) of ewes-selves for group Ⅲ (137.4±59.8 g) was greater than those of groups Ⅰ and Ⅱ (-57.7±39.9 and 34.2±56.2 g). Differences in birth weight of lambs (3.82±0.76, 3.86±0.58 and 4.10±0.77 kg respectively) among the three groups were not significant, but litter weight was greater for group Ⅲ (7.69±2.24 kg) than for groups Ⅰ and Ⅱ (5.73±1.34 and 5.40±1.65 kg). 2) During the period of lactation, milk yield of ewes (27.08±4.52, 40.34±11.90 and 55.48±14.29 kg), body-weight (BW) (13.49±3.82, 14.62±3.64 and 19.32±4.45 kg) and body-weight gain (BWG) of litters (7.17±2.71, 9.22±2.17 and 12.28±3.15 kg), BW at weaning (7.71±2.26, 10.45±1.72 and 11.19±2.51 kg) and BWG of lambs (4.10±1.60, 6.59±1.38 and 7.08±2.09 kg) increased with the nutritive levels of ewes. BW of group Ⅰ ewes increased (+0.94±2.053 kg) but for groups Ⅱ and Ⅲ, it decreased (-0.35±2.74 and -1.86±3.89 kg), although there were no significant differences in BWG among all groups. 3) For group Ⅰ, Ⅱ and Ⅲ ewes, BWs at the end of nursing were 46.31±7.61, 46.85±2.58 and 52.93±4.20 kg respectively. The first estrous cycle occurred at 18.60±12.86, 13.25±6.70 and 10.71±4.07 d after cessation of nursing. The ratios of barren ewes at the end of the second estrous cycle were 16.67%, 20.00% and 14.29%, and the lambing intervals were 201.8, 183.5 and 187.7 d.

Nutritional evaluation of Helianthus tuberosus meal on lactating dairy cows

ZHAO Fang-fang, ZHENG Chen, LI Fa-di, HAN Xiang-min, HAO Zheng-li

2011, 20(6):  264-269. 

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A 3×3 latin square design was used to determine the nutritive value of Helianthus tuberosus meal with six lactating Holstein dairy cows. 1) On an air dry basis, dry matter, crude protein, ether extract, crude fiber, nitrogen-free extract, neutral detergent fiber, acid detergent fiber, calcium, phosphorus, and milking energy of H. tuberosus meal were 92.43%, 2.98%, 0.81%, 12.67%, 25.93%, 21.44%, 3.92%, 0.27%, 0.20% and 5.18 MJ/kg respectively. H. tuberosus meal was a poor energy feed for dairy cows. 2) The digestibility of dry matter, crude protein, neutral detergent fiber and acid detergent fiber of H. tuberosus meal (on an air dry basis), were 61.78%, 73.21%, 51.65% and 61.14% respectively. The digestible energy and net energy were 10.13 and 5.18 MJ/kg. In three treatments the digestibility of compendium nutritive matters tended to decrease. H. tuberosus meal was higher in feed digestibility than the common meal and had no influence on dairy cows. 3) The addition of H. tuberosus meal to the dairy ration did not affect the production performance.

Characteristics of herbage water soluble carbohydrates and of factors influencing them

HUANG De-jun, MAO Zhu-xin, FU Hua

2011, 20(6):  270-278. 

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Water soluble carbohydrates (WSC) are one of the basic metabolic materials in plants and they influence plant growth, development and adaptability to harsh environments. In addition, an increase in WSC content can enhance the use efficiency of protein and dry mass in forage by herbivores, thereby not only enhancing protein production in milk, but also reducing CO₂ emissions from the animal’s rumen. In this paper, we summarize the characteristic of WSC in the plant influenced by the biotic and abiotic factors such as heredity, environment, and cultivation management. WSC contents of plants differed between plant species, organ positions and phonological phases. Environmental factors such as temperature, water, salt and nutrition contents also had major influences on WSC content.

Advances in research on the function of artificial grassland in karst rock desertification control

LI Xin, XIONG Kang-ning, GONG Jin-hong , CHEN Yong-bi

2011, 20(6):  279-286. 

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Karst rock desertification is the most serious eco-geologically environmental problem in southwestern china. Lawn is the final barrier that protects the ecological environment in this karst area and plays an irreplaceable role in controlling karst rock desertification. This review summarizes advances in research on the distribution of karst, the problems from ecological and economic viewpoints, the role of grassland in the control of rock desertification, and the theory and technology of grassland construction in karst areas. Grassland construction in karst areas has some problems including unreasonable use of grassland, relatively low level of industrialization, and lack of research on grass water. We propose that research on the selection of drought-resistant grass species, grass water, grassland animal husbandry industrialization, low-cost building of artificial grasslands, and disaster prediction and control are urgent to address the problems in karst areas.

Variation of net ecosystem carbon flux and its impact factors on Stipa baicalensis steppe in the growing season

XU Li-jun, TANG Hua-jun, YANG Gui-xia, WANG Xu, WANG Bo, XIN Xiao-ping

2011, 20(6):  287-292. 

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CO₂ flux and its impact factors were measured by an eddy correction system in Stipa grassland. There were distinct diurnal and seasonal variations with an inverted U-shape diurnal change in CO₂ flux. There was obvious change in July, and the maximum uptake and emission were -0.56 and 0.83 mg/(m²·s), respectively. Latent heat flux, sensible heat flux, net radiation flux and photosynthetic active radiation were related to CO₂ flux. There was no obvious correlation between soil temperature and soil water content with CO₂ flux.

A study on photosynthetic characteristics and simulation of the psammophyte Artemisia halodendron

LI Xi-meng, LU Zhi-yao, MA Shuai, FENG Jin-zhao

2011, 20(6):  293-298. 

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The diurnal dynamics and light response curve of photosynthetic rate (Pn) were measured in Artemisia halodendron. Under natural conditions the diurnal dynamics of A. halodendron Pn showed double peaks with a significant mid-day depression. The decrease in Pn between 8:00-14:00 was attributed to the stomatal limitation and after 14:00 the decrease was due to non-stomatal limitation. Diurnal dynamics of water use efficiency was similar to that of Pn, showing its strong adaptation to drought. Furthermore, different photosynthetic response models and stomatal models were used to simulate the response and we found that the simulated value of a modified rectangular hyperbola model and modified stomatal model had the best fit with observed values.

Influences of row spacing on fertile tillers and characters of seed yield of Elymus sibiricus cv. Chuancao No.2

YOU Ming-hong, LIU Jin-ping, BAI Shi-qie, ZHANG Xin-quan, LI Da-xu

2011, 20(6):  299-304. 

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A randomized block design was utilized with five row gradients (30, 45, 60, 75, and 90 cm) to measure and analyze the characters of shoots, inflorescence and seed yield of Elymus sibiricus cv. Chuancao No.2. Row spacing had a highly significant affect on tillers, ratio of fertile tillers, fertile tillers per square metre, height of fertile tillers, and diameter of fertile tillers. This resulted in very significant differences among the length and diameter of ear stalks, cob lengths, spikelets and florets per fertile tiller. These results finally led to eventual differences among setting percent, presentation seed yield, and harvested seed yield. However, the total florets per square metre and the potential seed yield were stable at different row spacings. The partial correlation analysis further showed that plant height was the main factor affecting setting percent. The length of inflorescence stalk reflected the spikelets and seeds of fertile tillers and harvested seed yields. Thus we may predict setting percent and seed yield through plant height and length of inflorescence stalks. The 1 000-seed weight and other parameters were relatively stable. Comprehensive experimental data showed that sowing with a row space of 60 cm gave the greatest potential seed yield, presentation seed yield and harvested seed yield, and is therefore recommended to be widely using in practice.