土壤田间持水量与麻黄碱含量变化关系的初步研究

采用大田与栽培池相结合的方法 ,对麻黄草不同灌水量与干草量、麻黄碱含量等生理指标含量进行了研究 。

中科系列羊草适应性比较研究

对从原种地引种到海南、宁夏地区后的中科系列羊草生长状况、营养成分含量变化状况等进行评价分析,结果表明:引种羊草到海南省后,羊草生长的茎秆较细,纤维素含量降低;虽然鲜草量有所增加,但是干草重量却比宁夏种植小;种植当年虽然有个别植株有抽穗,但是种子成熟度较差,空壳率几乎为100%,这主要是由于气候影响,日温差较小,影响羊草种子结实率,不适于羊草种子繁殖。

狗牙根牧草资源概述及猪粪尿施肥试验

施肥禁牧区每公顷产干草11947 kg,比不施肥禁牧区每公顷产干草4873 kg,增产145.2%,自然放牧区施肥后每公顷载畜量3.59个黄牛单位,自然放牧区每公顷猪粪尿消纳量14.82 t,狗牙根生长期244 d。为狗牙根牧草开发利用提供依据。

Studies on the Super-high-yield Cultivation Techniques for Oats in Tibet

[Objective] The aim was to explore the optimal levels of different factors influencing oat yield in Lhasa, Tibet. [Method] Orthogonal test was conducted to analyze oat cultivation technology in Tibet. [Result] Qingyin No.2 and Baiyan No. 8 were proved the optimal species to be grown in Lhasa with optimal sowing quantity at 150-180 kg/hm2. Sowing term is an extremely significant factor affecting growing season, and species and N fertilizer are significant factors. Al factors have none significant effects on hay yield. [Conclusion] The research provides theoretical refer-ences and technological supports for large-scale planting.

Comprehensive Quality Assessment of Groundwater Environment in Typical Arid Grassland

[Objective] To comprehensively assess the groundwater quality in typical arid grassland. [Method] Based on the survey of pollution sources and analysis of onsite water quality monitoring of Darhan Muminggan United Banner （Damao County） which situated in the inland river basin at the north foot of Yinshan Mountain, the Nemero index method was used to assess the groundwater quality of this area, and the causes for the pollution were also analyzed. [Result] The groundwater quality in Damao County is between poor and very poor. [Conclusion] This study laid the foun- dation for the control of groundwater pollution in Damao County.

Mycelium Growth and Yielding of Black Poplar Mushroom-Agrocybe aegerita （Brig.） Sing. on Different Substrates

Mycelial growth and yield of two strains ofA. aegerita on different substrates was investigated. Mycelial growth on agar media （PDA, standard, wheat, MEA, CYM, PCA, sawdust extracts： alder and mixture of beech and birch （1：1）） and sawdust substrates （birch, beech, oak, maple, alder） was investigated. Petri dishes （Ф 9 cm） for agar media and biological tubes （18 cm long and Ф 2.5 cm） for sawdust substrates were used. Yield and morphological features were studied on birch, beech and mixture of beech and alder （1：1） sawdust substrates. The temperature of inoculation for agar media and sawdust substrates was 25 ℃. For yielding, when mycelium has completely overgrown the substrate the temperature was decreased to 15-17 ℃ to initiate primordia formation. The cultivation was enlightened 10 h/d with daylight lamps （500 Ix）. One crop was harvested after five weeks. The carpophores of black poplar mushrooms were picked up in clusters. There was no statistically important difference between the mycelial growths of the investigated strains. The best growing agar media were PDA （7.3 cm）, MEA （7.2 cm） and wheat （7.1 cm）, both strains showed the slowest mycelium growth on CYM （5.2 cm）. The mycelial growth on sawdust was the best on the beech （7.1 cm） and birch （6.8 cm） sawdust. The best substrate for cultivation ofA. aegerita was mixture of beech and alder sawdust （39.5 g/100 substrate DM）. The dry yield of carpophores were the highest on beech and alder substrate （3.2 g/100 substrate DM）, but dry matter content was the highest on beech sawdust （15.7%）. The heaviest carpophores were harvested from birch sawdust （3.7 g）; the biggest caps from beech and alder sawdust （3.3 cm）. There were no statistically important differences between the mycelium growth and yielding between both investigated strains.

Effect of Weed Control on Establishment and Herbage Production in Dwarf Napiergrass

Weed control is a crucial factor for maintaining establishment and herbage production in dwarf variety of late-heading type （DL） napiergrass （Pennisetum purpureum Schumach） in southern Kyushu, Japan. This study was aimed to verify the weeding-effect on dry matter （DM） production in the farm level and to examine the effect of several weed control, i.e. mixed sowing of annual setaria （abbreviated as S）, which has no regrowth ability after stem-elongation, paper-mulching （as P） and hand-weeding （as ＋W）, compared with no-weeding （as -W） on DM yield and quality of DL napiergrass in two years. Weed control practices significantly （P 〈 0.05） promoted several plant growth attributes in DL napiergrass, compared with no-weeding both in the farm and experimental levels. Paper-mulchidng （P-W or P＋S-W） had highest yields among several practices in both years. Setaria-sowing ha a partially mitigating effect of weed damage on DM production of DL napiergrass, while additive DM gain from setaria could compensate the yield decrease in DL napiergrass and reduce herbicide cost. Neither digestibility nor crude protein was affected by any weed control in either year. Thus, paper-mulching and annual setaria-sowing could be effective alternative practices for weed control of this species.

Research on the Degradation Kinetics Model in the Drying Process of Chinese Herb

Curative compositions such as catolpol in Rehmannia Glutinosa, flavone in Ophiopogon Japonicus and ginsenoside Re in Panax Ginseng in Chinese herbs were measured as the experimental indices by the method of high performance liquid chromatography under different drying conditions. The reaction order and parameters of the degradation kinetics model were determined and the model was verified by experiments. It was indicated that by comparing with the thin drying method, the prospective model could predict the degradation of curative compositions with drying time, temperature and moisture content of herbal materials with enough precision and could be used to simulate the degradation in the drying process of Chinese herb.

Madagascar High Lands Dry Season Forages： Lofium multiflorum （Italian Ray Grass） and Avena sativa （Oat）

Italian ray grass and oat are two grass species characterized by their ability to adjust tropical climate conditions. This study proposed to assess forage productivities to allow an appropriate mowing period determination in their use as dairy female feed in Madagascar. A test on small plots has been set up in the southern part of the capital city Antananarivo during one dry period （4 months）. Live observations followed by laboratory proximate analyses have been performed for forage productivity and feeding value determination. Cultivated on tanety （hill）, irrigated in counter season, results show that： （I） oat higher height （H = 96.7 cm） than Italian ray grass （H= 69.4 cm） at 99 days of age; （2） similar biomass productivity; （3） dry matter yields significantly different （p = 0.05）; （4） certain similarity between dry matter yields and FMU （fodder milk unit） score evolution; （5） leafy stage of Italian ray grasses at 99 days of age; （6） mid-flowering stage for oats during the same period. Cell wall content, crude fiber and dry matter contents increased with age （p = 0.05）. Crude proteins and minerals evolved in opposite directions. Gross energy content did not present precise variation with age. This study allowed that for an acceptable quantitative and qualitative production during dry seasons, good mowing period for Italian ray grass could start at 76 days age, while oat could start being harvested at 68 days.

Assessing Stylo （Stylosanthes hamata cv. Verano） for Fodder in Semi-arid Nigeria： 1. Effects of Sowing Methods on Growth and Herbage Yield

Field experiments were conducted at Dabagi Farm of the Usmanu Danfodiyo University, Sokoto （13~I＇N and 5~15＇ E）, in the Semi-arid of Nigeria, during 2007 and 2008 rainy seasons to determine the effect of sowing methods on growth and fodder yield of Stylosanthes hamata cv. Verano. Three sowing methods （dibbling, broadcasting and drilling） were investigated. The experimental design adopted for the study was the randomized complete block design （RCBD） replicated three times. The parameters monitored included plant height （cm）, leaf length （cm）, leaf width （cm）, number of leaves, canopy spread （cm）, stand count and herbage yield. Samples were randomly taken and marked for the measurement of the parameters at 2, 4, 6, 8, 10, 12 and 14 weeks after sowing （WAS）. Herbage yield （kg hal） was determined at the end of the 14th week. Result of the study revealed that the sowing methods had significant effect （P 〈 0.05） on growth parameters at 2 to 14 WAS in 2007, 2008 and in their combined analysis. Dry matter yield differed （P 〈 0.05） significantly. Dibbling method produced plants that were taller, longer, with wider canopy spread and leaves as well as more leaves and stands （P 〈 0.05）. The year 2007 produced taller plants, longer, wider canopy spread and leaves as well as more leaves and stands （P 〈 0.05） in all the weeks compared to the year 2008. It was therefore concluded from the results of this study that dibbling method of sowing was the best for Stylosanthes hamata cv. Verano production at 50 ~ 50 cm inter and intra-row spacing in the semi-arid of Sokoto agro-ecology in northwestern Nigeria, presumably due to low competition for scarce moisture and creation of more space in this sowing method.

Effects of Drying and Blanching on the Quality of Toona sinensis

[Objective]To explore the best T.sinensis processing technology.[Method]The T.sinensis was treated by hot wind drying,freeze drying and blanching,and the contents of ascorbic acid,total phenolics and nitrite were determined respectively before and after the treatment to be a standard to evaluate the influence of different processing methods on the quality of T.sinensis.[Result]Both drying and blanching produced certain impact on the contents of all three components,among which the content of ascorbic acid was slightly influenced by vacuum freeze drying and short-time blanching,but greatly affected by long-time blanching and hot wind drying;the loss rate of polyphenols was above 60% when the hot wind drying,freeze drying and blanching lasted for more than 5 min,while it experienced little change under short-time blanching;hot wind drying and blanching may greatly reduce the content of nitrite,however,the vacuum freeze drying even improved the content,which would produce adverse impact on food safety.[Conclusion]Short-time blanching is the best method to process T.sinensis,it can effectively reduce its content of nitrite and retain the nutrients.

Drought shifts soil nematode trophic groups and mediates the heterotrophic respiration

As the most diverse metazoan taxa,soil nematodes serve a diversity of functions in soil food webs and thus can regulate microbial community composition and affect organic matter decomposition and nutrient turnover rates.Because nematodes depend on water flms to access food resources,drought can negatively affect nematode-microbial food webs,yet the impacts of drought on nematode diversity and abundance and how these changes may infuence food web members and their functions are hardly explored.Here,we coupled research along a drought gradient in arid and semiarid grasslands with a detailed intact plant-soil microcosm experiment to explore the patterns and mechanisms of how drought impacts nematode abundance and carbon footprint,microbial phospholipid fatty acid(PLFA)and heterotrophic soil respiration.Overall,in the feld and the microcosm experiments,we found that nematode abundance,carbon footprint and diversity,microbial PLFA and heterotrophic respiration were reduced under drier conditions.In addition,drought altered nematode and microbial community composition,through reducing the nematode channel ratio and increasing the relative fungivorous nematode abundance and the fungal to bacterial ratio.The soil decomposition channel shifted from a bacterial to a fungal pathway in response to drought,indicating decelerated heterotrophic respiration under drought.These results highlight the important contribution of soil nematodes and their associated microbial food web to soil carbon cycling.Our fndings underscore the need to incorporate key soil fauna into terrestrial ecosystem model evaluation.

Stoichiometry of leaf carbon, nitrogen, and phosphorus along a geographic, climatic, and soil gradients in temperate desert of Hexi Corridor, northwest China

Aims Understanding the regional pattern of leaf stoichiometry and its contributing variables are of importance for predicting plant responses to global change and modelling the productivity and nutrient fluxes of ecosystems.In this study,we investigated leaf stoichiometry of plants that sampled from Hexi Corridor,a typical arid region in China,and tried to explore the contribution variables on leaf stoichiometry along the geographic,climatic,and soil gradients.Methods In August 2012,70 sites in Hexi Corridor were investigated.Plant leaves and soils from five equivalent plots within each site were sampled.C,N,and P contents of leaf and soil were measured.Important findings Compared with leaf N and P contents in regional and global scales,leaf N content in Hexi Corridor was close to them with the value of 20.19 mg g^(-1),while leaf P content was lower than them with the value of 1.34 mg g^(-1).Overall,leaf N:P value in Hexi Corridor was 15.70.Individually,leaf N:P values of shrubs and herbs were 16.81 and 14.80,respectively.Scaling exponents for leaf N vs.P of overall and shrubs in Hexi Corridor were 1.29,higher than the scaling exponent of herbs(1.08).Leaf stoichiometry of shrubs and herbs did not show significant latitudinal and longitudinal patterns,meanwhile,it has no significant correlation with mean annual precipitation(MAP),mean annual temperature(MAT),and soil elements.However,only leaf stoichiometry of herbs has significant correlation with altitude and aridity degree.These results indicate that plants in Hexi Corridor are possibly co-limited by N and P,while shrubs are mainly limited by soil P and herbs are limited by soil N.Scaling relationship reveals that leaf N vs.P of herbs is isometric.With increasing altitude,the quadratic regression for leaf C and N contents and the linear regression for leaf P content of herbs reflect the difference responses of the three elements on the variation of MAT along the altitude and it could be explained by plant physiology hypothesis and biogeochemical hypotheses.With decreasing aridity,leaf N and N:P of herbs increased significantly,inferring that herbs growth would be limited by P increasingly and strengthening the increasing nitrogen availability with increasing precipitation.In conclusion,different altitude and aridity patterns for leaf stoichiometry of herbs and shrubs reveal the plastic survive strategies of different xerophytes in Hexi Corridor.Moreover,leaf stoichiometry of herbs in Hexi Corridor could be as indicator of the changing environment that caused by aridity.

Seasonal and interannual variations of ecosystem photosynthetic characteristics in a semi-arid grassland of Northern China

The ecosystem apparent quantum yield(α),maximum rate of gross CO_(2) assimilation(Pmax)and daytime ecosystem respiration rate(R.),reflecting the physiological functioning of ecosystem,are vital photosynthetic parameters for the estimation of ecosystem carbon budget.Climatic drivers may affect photosynthetic parameters both directly and indirectly by altering the response of vegetation.However,the relative contribution and regulation pathway of environmental and physiological controls remain unclear,especially in semi-arid grasslands.We analyzed seasonal and interannual variations of photosynthetic parameters derived from eddy-covariance observation in a typical semi-arid grassland in Inner Mongolia,Northern China,over 12 years from 2006 to 2017.Regression analyses and a structural equation model(SEM)were adopted to separate the contributions of environmental and physiological effects.The photosynthetic parameters showed unimodal seasonal patterns and significantly interannual variations.Variations of air temperature(T,)and soil water content(SWC)drove the seasonal patterns of photosynthetic parameters,while SWC predominated their interannual variations.Moreover,contrasting with the predominant roles of T,onαand Ra,SWC explained more variance of Pmax than T,Results of SEM revealed that environmental factors impacted photosynthetic parameters both directly and indirectly through regulating physiological responses reflected by stomatal conductance at the canopy level.Moreover,leaf area index(LAl)directly affectedα,Pmax and R,and dominated the variation of Pmax.On the other hand,SWC influenced photosynthetic parameters indirectly through LAl and canopy surface conductance(gc).Our findings highlight the importance of physiological regulation on the photosynthetic parameters and carbon assimilation capacity,especially in water-limitedgrassland ecosystems.

Woody plant encroachment may decrease plant carbon storage in grasslands under future drier conditions

Aims Woody plants are widely distributed in various grassland types along the altitudinal/climatic gradients in Xinjiang,China.Considering previously reported change in carbon(C)storage following woody plant encroachment in grasslands and the mediating effect of climate on this change,we predicted that a positive effect of woody plants on plant C storage in semiarid grasslands may revert to a negative effect in arid grasslands.We first investigated the spatial variation of aboveground C(AGC)and belowground C(BGC)storage among grassland types and then tested our prediction.Methods We measured the living AGC storage,litter C(LC)and BGC storage of plants in two physiognomic types,wooded grasslands(aboveground biomass of woody plants at least 50%)and pure grasslands without woody plants in six grassland types representing a gradient form semiarid to arid conditions across Xinjiang.Important Findings Living AGC,LC,BGC and total plant C storage increased from desert to mountain meadows.These increases could also be explained by increasing mean annual precipitation(MAP)or decreasing mean annual temperature(MAT),suggesting that grassland types indeed represented an aridity gradient.Woody plants had an effect on the plant C storage both in size and in distribution relative to pure grasslands.The direction and strength of the effect of woody plants varied with grassland types due to the mediating effect of the climate,with wetter conditions promoting a positive effect of woody plants.Woody plants increased vegetation-level AGC through their high AGC relative to herbaceous plants.However,more negative effects of woody plants on herbaceous plants with increasing aridity led to a weaker increase in the living AGC in arid desert,steppe desert and desert steppe than in the less arid other grassland types.Under greater aridity(lower MAP and higher MAT),woody plants allocated less biomass to roots and had lower BGC and had a more negative impact on herbaceous plant production,thereby reducing vegetation-level BGC in the desert,steppe desert and desert steppe.In sum,this resulted in a negative effect of woody plants on total plant C storage in the most arid grasslands in Xinjiang.As a consequence,we predict that woody plant encroachment may decrease rather than increase C storage in grasslands under future drier conditions.

Leaf and Ecosystem Gas Exchange Responses of Buffel Grass-Dominated Grassland to Summer Precipitation

Sporadic rain events that occur during summer play an important role in the initiation of biological activity of semi-arid grasslands.To understand how ecosystem processes of a buffel grass(Cenchrus ciliaris L.)-dominated grassland respond to summer rain events,an LI 6 400 gas exchange system was used to measure the leaf gas exchange and plant canopy chambers were used to measure net ecosystem CO2exchange(NEE) and ecosystem respiration(Reco), which were made sequentially during periods before rain(dry) and after rain(wet). Gross ecosystem photosynthesis(GEP) was estimated from NEE and Reco fluxes, and light use efficiency parameters were estimated using a rectangular hyperbola model. Prior to the monsoon rain, grassland biomass was non-green and dry exhibiting positive NEE(carbon source) and low GEP values during which the soil water became increasingly scarce. An initial rain pulse(60 mm) increased the NEE from pre-monsoon levels to negative NEE(carbon gain) with markedly higher GEP and increased green biomass. The leaf photosynthesis and leaf stomatal conductance were also improved substantially. The maximum net CO2uptake(i.e.,negative NEE) was sustained in the subsequent period due to multiple rain events. As a result, the grassland acted as a net carbon sink for 20 d after first rain. With cessation of rain(drying cycle), net CO2 uptake was reduced to lower values. High sensitivity of this grassland to rain suggests that any decrease in precipitation in summer may likely affect the carbon sequestration of the semiarid ecosystem.