红鳞蒲桃开花物候特性研究

对红鳞蒲桃种群的花期物候，单株、单个花序、单花的开花动态进行系统的观测研究，详细测量并记录花部构件，同时调查红鳞蒲桃种群的同花期植物。结果表明：红鳞蒲桃种群的花期物候为8月1日～9月15日（2008年），持续时间46d；单株花期从23d到33d不等；单花序的花期情况较为复杂，总体表现为花朵数越多，该花序持续时间越长，但也有个别情况出现，在开花中期花序持续时间长，开花后期花序持续时间最短，开花前期花序持续时间介于两者之间；在整个种群花期内单花平均开花时间约5．2d，种群开花前期单花的持续时间约为6．7d，开花中期约为4．7d，末花期约为4．3d，种群开花前期单花的持续时间显著大于种群中后期的持续时间。红鳞蒲桃种群的同花期植物隶属于16科21属22种。     

Germination ecology of seeds of the annual weeds Capsella bursa-pastoris and Descurainia sophia originating from high northern latitudes

Low temperatures may inhibit dormancy break in seeds of winter annuals, therefore it was hypothesized that seeds of Capsella bursa‐pastoris and Descurainia sophia that mature at high latitudes in late summer–early autumn would not germinate until they had been exposed to high summer temperatures. Consequently, germination would be delayed until the second autumn. Most freshly matured seeds of both species collected in August and September in southern Sweden were dormant. After 3 weeks of burial at simulated August (20/10°C) and September (15/6°C) temperatures, 28 and 27%, respectively, of the C. bursa‐pastoris and 56 and 59%, respectively, of the D. sophia seeds germinated in light at 15/6°C. In contrast, in germination phenology studies conducted in Sweden, only a few seeds of either species germinated during the first autumn following dispersal. However, there was a peak of germination of both species the following spring, demonstrating that dormancy was lost during exposure to the low habitat temperatures between late summer and early autumn and spring. Nearly 100% of the seeds of both species subjected to simulated annual seasonal temperature changes were viable after 30.5 months of burial. In the burial study, exhumed seeds of C. bursa‐pastoris were capable of germinating to 98–100% in light at the simulated spring–autumn temperature regime (15/6°C) in both spring and autumn, while those of D. sophia did so only in autumn. In early spring, however, seeds of D. sophia germinated to 17–50% at 15/6°C. Thus, most seeds of these two annual weeds that mature in late summer do not germinate in the first autumn, but they may do so the following spring or in some subsequent autumn or spring.     

Phenotypic Changes in Grain Sorghum Over the Last Five Decades

Sorghum [Sorghum bicolor (L.) Moench] is a drought‐tolerant crop, and its productivity in rain fed environments has increased since the 1950s. This increase is due to changes in agronomic practices and hybrid improvement. The objective of this study was to determine what aspects of grain sorghum morphology, physiology and water use have changed with hybrid improvement and might have contributed to this yield increase. A 2‐year greenhouse experiment was conducted with one hybrid from each of the past five decades. The hybrids were studied in well‐watered and pre‐ and post‐flowering water deficit conditions. Total water use, transpiration, stomatal conductance and photosynthesis were measured during the growing period. Biomass and biomass components were measured at harvest. There was no consistent change in the leaf physiological parameters resulting from hybrid advancement. In contrast, total water use increased in rate of 8.5 cm³ kg soil^?1 year^?1 from old to new hybrids in the well‐watered treatments. Root biomass also increased in rate of 0.2 g plant^?1 year^?1. Leaf biomass and panicle length also was greater for the newest compared with the older hybrids. Hybrid advancement was related to increase in panicle length but decrease in peduncle length. Results indicated that hybrid development programmes created hybrids with improved drought avoidance, due to better root density of newly released hybrids, or hybrids with better resource use which ultimately increased yield under rain fed conditions.     

Optimising cutting method and timing for the control of Abutilon theophrasti seed production

Abutilon theophrasti (velvetleaf) is a widespread and problematic annual weed. Greenhouse and field experiments were conducted to investigate the effects of different cutting methods on the viability of A. theophrasti seeds. Three cutting methods were assessed: (1) Entire plant cut and dried (EPD)—plants were cut at soil level and dried with capsules attached on the greenhouse bench or soil surface for 4 weeks; (2) capsules detached and dried (CD)—capsules were removed from plants and dried for 4 weeks; and (3) capsules detached and tested while fresh (CF)—a control treatment. Before drying, the developmental stage (stage one, dark green; stage two, light green; stage three, yellowish-green; or stage four, black with the slightly open capsule) and age (days after flowering, DAF) of each capsule was recorded. Seed viability was measured immediately in the CF treatment and after the 4-week drying period in the EPD and CD treatments. No seeds in the EPD and CD treatments were viable when harvested at the first developmental stage (1–8 DAF) in either experiment, but 100% of seeds in the CF treatment in the field were viable when harvested at 8 DAF. In both greenhouse and field experiments, seeds attained full viability at earlier harvest ages in CF than in EPD or CD treatments, suggesting that seeds might become viable relatively early in development but lose viability if allowed to dry. These findings could be applied to optimise late-season mechanical control of A. theophrasti.     

Foliar lifespan,phenology and seasonal dynamics of the invasive shrub Schinus terebinthifolia

Schinus terebinthifolia is a dioecious tree native to South America that has become an invasive weed in Florida, southern California, southern Arizona, Texas and Hawaii and has been naturalised in over 20 countries. Biological control is considered a viable long-term control option for S. terebinthifolia because release from natural enemies appears to be at least partly responsible for its success in Florida. We examined leaf phenology of S. terebinthifolia over a period of 15 months at five sites in central and southern Florida to provide information that may help in predicting the impacts of potential biocontrol agents for this weed. We documented leaf lifespan, the seasonality of leaf development and abscission and the survivorship of leaves that emerged during either spring, summer or autumn. Average leaf lifespan was >4.5 months at all sites, and leaf phenology followed the seasons closely. Although S. terebinthifolia possesses leaves throughout the year, leaf production was greatest from April to September, and most leaves were abscised in February and March. Spring- and summer-emerging leaves were also longer-lived than leaves produced during autumn. These results suggest that leaves of S. terebinthifolia would be most vulnerable to herbivory during the spring and summer months when newly growing leaf tissue is most plentiful. Biocontrol agents capable of damaging these tissues during spring/summer might be an effective means of controlling this invasive weed.     

Season-specific varietal management as an option to increase rainfed lowland rice production in East African high altitude cropping systems

Due to land expansion and an increase in productivity, rice production in sub-Saharan Africa has been growing at a rate of 6% in the past decade. Rainfed rice production systems have accounted for a large share of this expansion. In these systems, the potential growing period not only depends on the length of the rainy season and thus water availability, but is often, especially in the highlands of East Africa, bordered by the onset of the cool period of the year, when low minimum temperatures compromise rice yields. The objective of this study was to investigate the yield potential of 30 rice varieties contrasting in crop duration and cold tolerance in the highlands of East Africa, with its limited length of growing period. A field trial was conducted in the cropping seasons in 2016 and 2017 at the Fogera rice research station, Ethiopia. As a function of the onset of rains, rice was sown mid-July in 2016 and early July in 2017. Early sowing in 2017 led to an extended crop duration and significantly lower yields of the short-duration varieties, and to a shortened duration and significantly higher yields of the medium- and long-duration varieties, when compared to late sowing in 2016. Late sowing compromised yield of the medium- and long-duration varieties because of low temperatures during booting stage, which led to high spikelet sterility. Early sowing resulted in low yields of the short-duration varieties, probably due to low solar radiation during the cloudy rainy season, which coincided with the vegetative stage. Therefore, choice of variety should be a function of the variable onset of the rainy season and related sowing date. However, crop models precisely calibrated for potential varieties and the respective environmental conditions could fully support the selection of a suitable variety, depending on the date of sowing, for example with the help of online tools or smartphone applications.     

广东葡萄一年两收设施避雨栽培模式主要病虫害与防治关键期

【目的】全面了解广东葡萄一年两收设施避雨生产模式主要病虫害的发生情况,明确其防治关键物候期。【方法】在 2016—2019 年进行走访式和常规式调查按治早治小的原则,根据主要病虫害发生动态、相对应的葡萄物候期和防治实践确定防治关键期。【结果】在设施避雨模式下,广东一年两收葡萄病害发生最严重的是白粉病,其次是溃疡病、霜霉病、穗轴褐枯病、灰霉病、日灼病、气灼病、毛毡病等;虫害发生最严重的是蓟马,主要物种是茶黄蓟马、烟蓟马、棕榈蓟马,其次是二斑叶螨、斜纹夜蛾、中喙丽金龟、缺节瘿螨等。与露地栽培的主要病虫害有较大差异。防治关键期重点在休眠期（修剪清园期）、开花前期、幼果期、果实膨大期、果实转色期、果实成熟期。【结论】广东葡萄一年两收设施避雨模式主要病虫害种类不同于露地栽培,具有易重叠发生、危害期较长、多种病虫害出现两个甚至多个发生高峰期、同一病虫害更易爆发等特点。应对广东一年两收设施葡萄病虫害应当有针对性抓关键期防治,重点做好休眠期清园,消灭病虫源,结合花期果期等防治关键期开展有针对性的病虫害防治。     

基于MODIS-LAI数据的广西甘蔗物候期提取

广西是我国甘蔗最大的种植区和蔗糖产业基地,但多年来因自然灾害导致的产量损失严重。及时、准确获取甘蔗的物候动态,可为区域甘蔗种植结构优化、灾害风险管理等提供科学支撑。本文分别借助Savitzky-Golay滤波、Asymmetric Gauss拟合及Double Logistic拟合方法对广西2014—2018年的甘蔗MODIS-LAI数据进行时间序列重构,并采用动态阈值法识别甘蔗关键物候期的时空变化特征。结果表明:1)上述方法可有效消除广西甘蔗LAI序列的不稳定波动和奇异值,且Asymmetric Gauss和Double Logistic方法的拟合结果较好地弥补了S-G滤波处理中局部曲线值动荡变化的缺点,能更准确地识别甘蔗生长过程;2)三种方法对广西甘蔗的播种-萌芽期、茎伸期、成熟期开始时间识别的RMSE和平均误差均在±15 d内,其中Asymmetric Gauss方法对甘蔗物候期的提取结果最优。综上,时序曲线重构法的抗干扰性能较好,可一定程度上弥补因云雨、复杂地形地貌导致LAI序列的误差,保证广西甘蔗物候信息获取的准确性。     

Growth and development of Cirsium arvense in relation to herbicide dose,timing of herbicide application and crop presence

The aim of this study is to assess control effects of 2-methyl-4-chlorophenoxyacetic acid (MCPA) dosage, application timing and crop presence on the weed Cirsium arvense. Swedish farmers are recommended to control C. arvense chemically when most shoots are 10-20 cm tall, and mechanically at the compensation point (CP). Recent studies have shown that the CP occurs before shoots reach the three-leaf stage. We hypothesised that (i) herbicide application near the three-leaf stage gives the strongest control, (ii) crop presence increases herbicide effects, and (iii) a 50% herbicide dose gives the same effect as 100%. Treatments of the pot experiment consisted of MCPA 750; 0%, 50% and 100% of the recommended dose applied at leaf stages 3-8, with and without barley. The strongest control was obtained at four leaves and a maximum shoot height of 13 cm, using the recommended dose and with spring barley. In a field population, a maximum shoot height of 13 cm corresponded to a medium height of 6 cm. The 50% dose gave poorer control. Spraying with the recommended dose at the four-leaf stage reduced the development of C. arvense most effectively. Based on this, we recommend that herbicide spraying should be performed at earlier leaf stages/median heights than previously recommended.     

近150年北京春季物候对气候变化的响应

对北京春季6种物候的计算得出其代表性指标一山桃始花期，并分析物候对气温变化的响应模式。根据气温变化态势，将历史时期气温和物候资料划分为4个时间段，并采用u检验论证时间段间具有显著性差异，分析物候期对气温变化的响应模式和机制，得出：物候期的提前与推迟对温度的增高与降低的响应是非线性的，在同等增、降温幅度下，因降温而导致的物候期推迟幅度较因增温而导致物候期提前幅度小；平均气温增高1℃，北京春季物候期提前2．8—3．6d。并估算了未来北京春季物候变化趋势。