Effects of winter barley as a cover crop on the weed vegetation in a no-tillage soybean

The present study clarified the effects of winter barley as a cover crop on the weed vegetation, expressed as a multiplied dominance ratio (MDR), and emergence of summer annual weeds in a no-tillage soybean system. A 3 year field study with treatments consisting of six systems was conducted: no-tillage single cropping, no-tillage cropping following winter barley and tillage single cropping, respectively with and without herbicide application. The MDR of perennial weeds increased annually in the no-tillage fields in spring, but summer annual weeds were abundant in all fields, including the no-tillage fields in summer. Grasses, for example Digitaria ciliaris (Retz.) Koeler, were especially abundant in the no-tillage fields. The MDR of summer annual weeds, especially grasses in the barley and soybean fields, were much lower than for the no-tillage single soybean fields. Densities of D. ciliaris and Echinochloa crus-galli (L.) Beauv. var. crus-galli in the no-tillage single soybean fields were much greater than in the tilled fields, with few exceptions. In contrast, broad-leaved weeds emerged more in tilled fields than in the no-tillage fields. Winter barley suppressed emergence of summer annual weeds, especially during the first 3 years. The MDR for grasses in summer showed a good correlation with the frequency of emergence for grasses every year. These results showed that the increase in the volume of grasses in summer resulted mainly from an increase in the frequency of emergence, and that the suppression of grasses by winter barley resulted mainly from suppression of the emergence frequency. Soybean yields were higher in the barley and soybean fields for the first 2 years.     

不同除草剂对稻田杂草群落演替的影响

为了明确除草剂对稻田杂草群落演替的影响,2001～2004年,连续4年施用7种稻田除草剂控制移栽稻田杂草,每年调查稻田杂草的种类、密度和鲜重,分析稻田杂草种群的变化.结果表明：连续使用同一除草剂对稻田杂草群落演替影响显著,靶标杂草的优势度值与药剂使用年限存在显著的线性或非线性关系：Y=a＋bx或Y=ax^2＋bx＋c;非靶标杂草优势度值与药剂使用年限呈极显著正相关线性关系.不同药剂处理的杂草群落有一定的差异,连续使用二元复配除草剂,杂草群落的均匀度和多样性指数分别为0.40～0.43和1.57～1.84,明显低于单剂处理和对照区,田间主要杂草是陌上菜、水苋、千金子和水莎草,其杂草的鲜重显著低于其它处理.     

Suppression of weeds and weed seeds in the soil by stubbles and no-tillage in an arid maize-winter wheat-common vetch rotation on the Loess Plateau of China

Reduced tillage provides ecological and economic benefits to arable land on the Loess Plateau of China, where soil erosion has long been a serious problem and soil water availability is largely restricted. However, high abundances of weeds in reduced tillage systems cause significant yield losses. In this study, we explored the effects of no-tillage and stubble retention on the number and density of weeds and weed seeds in a 12-year maize-winter wheat-common vetch rotation on the Loess Plateau. Four treatments including conventional tillage, no-tillage, conventional tillage+stubble retention and no-tillage+stubble retention were designed and applied. We found that no-tillage increased the number of weed species and weed density in most of the crops, while stubble retention decreased weed density in maize and tended to suppress weeds in both no-tillage treatments(no-tillage and no-tillage+stubble retention). No-tillage led to an increase in the number of weed species in the weed seedbank and tended to increase seed density during the spring growth of winter wheat, but it decreased seed density during post-vetch fallow. Stubble retention tended to reduce seed density during the spring growth of winter wheat and post-vetch fallow. We concluded that no-tillage can promote weeds in the experimental crop rotation, while stubble retention suppresses weeds in untilled fields. The combined effects of stubble retention and no-tillage on weed suppression varied among the three crops. Based on these results, we recommend stubble retention in untilled legume-crop rotations on the Loess Plateau to improve the control of weeds.     

皖西南直播棉田杂草群落出苗模式

为明确皖西南直播棉田杂草群落出苗模式及其与气象因子的相关性,采用定点定时调查法,于2010—2012年对棉田杂草种类、数量及群落结构进行调查,分析物种多样性,并以灰色关联度法分析直播棉田杂草群落出苗数量与气象因子的相关性。结果表明,皖西南棉区直播棉田杂草种类有13科24种。棉田杂草出苗有2次高峰,分别在5—6月和8—9月。棉田杂草群落多样性指数年度间变化较一致,但物种丰富度变化较大。周积温、周最高积温和周最低积温是影响皖西南直播棉田杂草群落出苗数量季节变化的主要因素,另外还受降水量影响。5—6月的杂草出苗高峰期是棉田杂草重点防治时期;相对占优势的杂草有牛筋草、千金子、旱稗、通泉草和马齿苋,是棉田杂草重点防治对象。     

Influences of long‐term different types of fertilization on weed community biodiversity in rice paddy fields

In order to provide a scientific basis for developing integrated weed management strategies in rice paddy fields, this study investigated the influences of different types of fertilization on weed biodiversity. The experiment was conducted at Long‐term‐located Monitoring Station for Soil Fertility, Agricultural Science Academy, of Jiangxi Province, China. Five fertilization treatments were set: no fertilization (NOF), PK, NP, NK, and NPK. The results showed that the influence of different fertilization treatments on weed community traits followed the models PK > NOF > NK > NP > NPK for species richness, PK > NOF > NK > NP > NPK for species diversity, NPK > NP > NK > NOF > PK for community dominance, and PK > NOF > NK > NP > NPK for community evenness. Under NPK (i.e. balanced fertilization), the weed species diversity and richness and weed community evenness were the lowest. The principal component analysis showed that the weed community was divided into three groups: (i) NK and a part of NOF; (ii) NP and NPK; and (iii) PK and NOF. The correlation analysis indicated that the influence of each macro‐element on the weed community followed the model N > P > K. The organic content in the paddy soil might have played an equally important role with the amount of available N in determining the weed community's characteristics. Regarding the way by which N, P, and K influenced the weed community, the amount of available P and K mainly influenced the organic content, while the amount of available N influenced both the organic content and light transmittance within the canopy, thereby enhancing the capacity of rice to compete with weeds.     

全膜双垄沟播玉米田选用除草地膜的适宜田间杂草密度研究

在陇东旱塬生态条件下,田间测定了全膜双垄沟播玉米田选用化学除草地膜和黑色地膜的适宜田间杂草密度。结果表明,全膜双垄沟播玉米田覆盖白色地膜,玉米主要农艺性状、产量及经济效益均随田间杂草密度的增加而降低。杂草密度至少达到116.68株/m2和163.48株/m2时,分别选择覆盖化学除草地膜和黑色地膜可使玉米株高、株高整齐度、茎粗、茎粗整齐度、果穗长、果穗粗、穗粒数、百粒重、有效成穗株率、单位面积有效果穗数等主要农艺性状较覆盖白色地膜有明显改善,玉米产量和经济效益较覆盖白色地膜均有显著提高,产量增幅分别达到1.89%~48.18%和3.87%~47.72%,纯收益增幅分别达到4.49%~157.16%和11.21%~158.88%。     

沿江圩区长期稻麦连作田土壤杂草种子库的研究

通过对沿江圩区长期稻麦连作田土壤杂草种子库研究,结果表明,土壤杂草种子库中小麦田有8科14种、水稻田有9科17种。2种类型田块的种子库主要分布在0～10cm的土层中。小麦田该层出草量达77.74%,水稻田为72.05%。麦田土壤总出草量为11930株/m2,主要是日本看麦娘、草和稻槎菜,出草量占总量的59.96%;稻田土壤总出草量达9855株/m2,主要是稗草、节节菜、千金子和异型莎草,出草量占总量的51.03%。上述7种杂草是该区农田的主要杂草,均为当前防除的重点,其中日本看麦娘和稗草分别是小麦、水稻田的优势种。通过研究提出了减少土壤杂草种子库种源的对策。     

基于TM影像的草原沙漠化植被盖度分析研究

植被盖度是草原沙漠化评价的重要指标,以TM影像为数据源,结合地面调查数据和对应点的NDVI值,建立了植被指数与植被盖度间的回归模型,利用该模型生成植被盖度分布图;同时利用前人的植被盖度计算经验公式,生成同一区域的植被盖度分布图,并分别对其植被盖度数据进行分级。对比分级结果,发现:通过大量的地面调查数据建立的盖度分析模型分类精度较高,总精度达到85.42%,而通过经验公式计算,效果相对较差,其分类精度仅有75.00%。     

基于随机占优准则的山岳型景区游客感知测评研究——以中华五岳为例

游客感知是旅游者对旅游体验的认识和评价结果,关乎其旅游决策和满意度,对于山岳型景区的可持续发展有着重要意义。文中以中华五岳为例,利用第三方平台数据并基于随机占优准则和PROMETHEE-Ⅱ法对山岳型景区游客感知进行研究。结果表明:游客对于五岳景区生态环境和文化底蕴的评价较高,而对于景区管理和服务意识的评价偏低,并且针对个别影响因素出现了不同的游客体验倾向。在此基础上,利用实地考察对数据结果进行验证,提出五岳景区需针对其短板做出不同的改进策略,因地制宜对各景区进行整改完善,真正做到可持续、稳定地发展,这对提升山岳型景区形象及落实可持续发展具有重要意义。     

Roles of emergence time and interspecific competition on the dominance and coexistence of Setaria faberi and Digitaria ciliaris in an orchard weed community in Japan

Setaria faberi and Digitaria ciliaris are summer annual grass weeds that constitute an orchard weed community in Japan. Species dominance in the weed community shifts from S. faberi to D. ciliaris with an emergence delay. The change in species dominance is assumed to be a clue to how weeds dominate or coexist in shaping the community. Population dynamics and seasonal variations in emergence and competitive ability were studied from this viewpoint. Field monitoring and pot experiments exhibited that the emergence period of the two species overlapped extensively from April to June. The emergence of S. faberi began 2 weeks earlier than that of D. ciliaris in April and declined in June as a result of the induction of secondary dormancy. The plant density of D. ciliaris was high during the whole period. The great mortality of the species was replenished with its great natality. The replacement series experiments revealed that S. faberi that had been planted in April was a better competitor than D. ciliaris, but it lost its competitive superiority in the June plantings, when D. ciliaris became a superior competitor to S. faberi. The level of seed output was greater for D. ciliaris, even when it was an inferior competitor. Therefore, the shift in species dominance appeared to be attributed to a change in competitive superiority between the two species. The early emergence of S. faberi and the high plant density of D. ciliaris might accelerate competitive exclusion. The two species coexist when they are equivalent in competitiveness.     

Impact of large-scale vegetation restoration project on summer land surface temperature on the Loess Plateau,China

A large-scale afforestation project has been carried out since 1999 in the Loess Plateau of China. However, vegetation-induced changes in land surface temperature (LST) through the changing land surface energy balance have not been well documented. Using satellite measurements, this study quantified the contribution of vegetation restoration to the changes in summer LST and analyzed the effects of different vegetation restoration patterns on LST during both daytime and nighttime. The results show that the average daytime LST decreased by 4.3°C in the vegetation restoration area while the average nighttime LST increased by 1.4°C. The contributions of the vegetation restoration project to the changes in daytime LST and nighttime LST are 58% and 60%, respectively, which are far greater than the impact of climate change. The vegetation restoration pattern of cropland (CR) converting into artificial forest (AF) has a cooling effect during daytime and a warming effect at nighttime, while the conversion of CR to grassland has an opposite effect compared with the conversion of CR to AF. Our results indicate that increasing evapotranspiration caused by the vegetation restoration on the Loess Plateau is the controlling factor of daytime LST change, while the nighttime LST change is affected by soil humidity and air humidity.     

基于MODIS的民勤绿洲植被覆盖变化定量分析

以典型沙漠绿洲-民勤绿洲为研究区,利用MODIS陆地3级标准数据产品MOD13,通过改进的植被覆盖度估算模型对2000～2010年7月的植被覆盖度进行了估算,并对其进行分级,通过空间叠置定量分析了不同级别植被覆盖度的分布特征及动态变化。研究发现,从2000～2010年11年间,民勤绿洲轮廓变化明显,绿洲面积明显缩小,荒漠进一步扩张,极低覆盖度植被面积增加1106.01km2,相当于研究区总面积26.95%,中高覆盖度和高覆盖度植被面积分别减少133.63km2和54.75km2,各占研究区总面积的3.26%和1.33%;研究表明,11年来民勤绿洲面积萎缩明显,岛状绿洲大量消失,其中以西北部最为严重。     

塔里木河下游生态输水对植物群落数量特征的影响

结合2002-2004年对塔里木河下游生态输水过程中5个断面固定植物群落样地的调查,运用群落数量分析法,分析了塔里木河下游植物群落对生态输水的响应.结果表明:在生态输水过程中,植被覆盖度普遍增加,草本植物覆盖度的增长率高于乔木和灌木;各断面乔木和草本植物的综合优势比普遍增加,但优势种的优势地位并没有改变,群落的类型没有变化;在整个研究区,物种的丰富度与均匀度仍很低.为提高输水生态效应,提出河道输水与面上供水相结合的输水方法和建立人工植被等建议.     

Effects of loosing Aigamo ducks on the growth of rice plants, weeds, and the number of arthropods in paddy fields

Aigamo duck farming has been noticed as one of the techniques of environmental conservation agriculture. This study was carried out to investigate the effects of loosing Aigamo ducks on the growth and production of rice plants, the quantity of weeds and arthropods, and the balance of nitrogen (N) in paddy fields by changing the density of the Aigamo ducks. A paddy field was divided into three test plots: a 10-Aigamo-duck plot, a five-Aigamo-duck plot, and a weeding plot. The results show that the height, number of culms, and yield crops of the rice plants increased more in the 10-Aigamo-duck plot and the five-Aigamo-duck plot than that of the weeding plot. Millet ( Echinochloa oryzicola ) remained in both the Aigamo duck plots. The weeding plot was covered with monochoria ( Monochoria vaginalis ). In both the Aigamo duck plots, the outbreak of total arthropods was lower than that of the weeding plot, but the number of rice plants damaged by grass leaf rollers ( Cnaphalocrocis medinalis ) was increased. The number of spiders, regarded as useful insects, did not differ that much between the experimental plots. The N content of the soil did not differ as an effect of loosing the Aigamo ducks. The rice plants in the 10-Aigamo-duck plot absorbed more N than the rice plants in the other plots.     

8%精噁唑甘草胺可分散油悬浮剂对直播水稻田禾本科杂草的防效及后茬作物的影响

为明确新型水直播稻田除草剂精噁唑甘草胺以及对照药剂对于直播稻田禾本科杂草的防除效果以及对于水稻及后茬作物的安全性, 于2019年在江西宜春市上高县水稻田进行了大田杂草防效试验以及后茬作物安全性研究。结果表明:8%精噁唑甘草胺OD对于直播水稻田的禾本科杂草具有良好的防除效果, 120 g/hm2 以及200 g/hm2 剂量处理对于禾本科杂草的防效均在88%以上。而且所有处理对于水稻均无药害产生, 实现增产, 并对后茬作物生长安全。综上所述, 新型直播稻田除草剂精噁唑甘草胺对直播水稻田禾本科杂草有良好防除效果, 可以在市场上推广应用。     

施氮对关中地区冬小麦农田土壤呼吸的影响及基于植被指数的估算模型

为探寻不同施氮量对农田土壤呼吸（R_S）的影响并快速准确估算R_S,以关中地区冬小麦为研究对象,观测了5种施氮量下冬小麦农田R_S的变化,研究了环境因子（土壤温度、土壤湿度）及作物因素（叶面积指数、地上部生物量、SPAD值）对于R_S的影响,建立了适用于关中地区土壤温度与植被指数下的农田土壤呼吸估算模型。设置秸秆还田下的5种施氮量处理,分别为传统施氮量SN200（200 kg·hm^-2）、优化施氮量SN150（150 kg·hm^-2）、60%优化施氮量SN120（120 kg·hm^-2）、50%优化施氮量SN100（100 kg·hm^-2）以及不施氮肥SN0（0 kg·hm^-2）。结果表明：不同施氮量下R_S随生育期推进均表现为先升高再降低的趋势,同时添加氮肥促进了R_S排放。各处理观测期内R_S的均值为：SN200（3.68 μmol·m^-2·s^-1）>SN150（3.40 μmol·m^-2·s^-1）>SN120（3.06 μmol·m^-2·s^-1）>SN100（2.70 μmol·m^-2·s^-1）>SN0（2.21 μmol·m^-2·s^-1）。不同施氮量下冬小麦冠层近红外波段反射率在拔节期和抽穗期差异明显,反射率从高到低依次为SN200>SN150>SN120>SN100>SN0,而在灌浆期和成熟期差异不大。土壤温度显著影响了R_S（P<0.01）,土壤湿度与R_S没有显著相关关系（P0.05）。叶面积指数、地上部生物量、SPAD值和植被指数均与R_S呈显著相关关系（P<0.05）。通过多种模型评估,建立基于植被指数和土壤温度的最佳农田土壤呼吸估算模型,显著高于基于土壤温度的单因子模型,模型精度可达到0.6以上（n=120）。     

Effects of long‐term fertilization on the weed growth and community composition in a double‐rice ecosystem during the fallow period

The vegetation cover during the non‐cropping season could have important implications for the maintenance and recovery of soil fertility, as well as for biodiversity conservation in croplands. In this study, five fertilization regimes (control: non‐fertilization; N: inorganic N fertilization; P: inorganic P fertilization; NPK: balanced fertilization with inorganic N, P and K; NPKM: balanced NPK plus farmyard manure) were conducted from 1981 in a double‐rice (Oryza sativa L.)‐cropping system in subtropical China. The effects of long‐term fertilization were investigated on the weed growth, diversity and community structure during the fallow period. The results showed that, relative to the control, both inorganic fertilization alone (N, P and NPK) and NPKM in the rice‐growing season significantly increased the weed density and biomass during the fallow period in the paddy field. There was no significant difference in the weed species richness (the number of species) among the treatments. Compared with the control, fertilization tended to reduce the weed diversity (Shannon's H′) and evenness (Shannon's E), especially in the N treatment. Long‐term fertilization resulted in a significant shift in weed community's composition during the fallow period. The weed community's structure was affected by soil nutrients in the order P > N > K.     

Spatial distribution of vegetation and the influencing factors in Qaidam Basin based on NDVI

The spatial distribution of vegetation in Qaidam Basin was analyzed using GIMMS(Global Inventory Modeling and Mapping Studies) /NDVI(Normalized Difference Vegetation Index) data set from January 1982 to December 2006.Based on the data of precipitation,terrain,stream systems,land use and the map of vegetation distribution in Qaidam Basin,we studied the factors influencing the spatial distribution of vegetation.The results showed that the vegetation was generally low in Qaidam Basin and there was a clear semi-ring structure from southeast to northwest.In some areas,the existence of rivers,lakes and spring belts turned this semi-ring structure into a non-continuous state and formed distinct bright spots and continuous linear features.There were four main factors that affected the spatial distribution of vegetation coverage in Qaidam Basin,i.e.,precipitation,hydrological conditions,altitude and human activities.Precipitation and altitude have a correlation and determine the basic pattern of vegetation distribution in Qaidam Basin.The impacts of hydrological conditions and human activities were mainly embodied in partial areas,and often broke the pattern of vegetation distribution dominated by precipitation and altitude.     

Establishment of, and preliminary impact studies on, the rust, Maravalia cryptostegiae, of the invasive alien weed, Cryptostegia grandiflora in Queensland, Australia

The rust fungus Maravalia cryptostegiae , from south-west Madagascar, was introduced into Australia in 1995 as a classical biological control agent against the highly invasive rubber-vine weed Cryptostegia grandiflora , a woody climber endemic to Madagascar. The rust was released at 69 sites between 1995 and 1997 and is now established throughout the plant's exotic range in Queensland, estimated at over 40 000 km². Dispersal was low in the first 3–4 months but was virtually linear thereafter, and the rust spread over 100 km within the first year; after 3 years it was recorded 550 km away from the nearest release site. Spraying both dry and aqueous inoculum of uredinioid teliospores from the ground using mist-blowers, as well as from the air by atomizing spore suspensions, resulted in rust-induced defoliation, producing an overall reduction in fecundity and biomass of the weed. In sites with low water tables, weed growth decreased markedly, with a reduction in plant volume from 9 m⁻³ to 1 m⁻³ over a 4-year period. Both rust- and drought-induced stress combined to cause up to 75% plant mortality at some sites, and at all monitored sites, seedling recruitment was virtually nil. Improved growth of indigenous grasses amongst rubber-vine thickets has increased fuel loads and created opportunities to use fire as a component of an integrated approach to the management of this economically and ecologically damaging weed.