Phenological observations on shrubs to predict weed emergence in turf

Phenology is the study of periodic biological events. If we can find easily recognizable events in common plants that precede or coincide with weed emergences, these plants could be used as indicators. Weed seedlings are usually difficult to detect in turf, so the use of phenological indicators may provide an alternative approach to predict the time when a weed appears and consequently guide management decisions. A study was undertaken to determine whether the phenological phases of some plants could serve as reliable indicators of time of weed emergence in turf. The phenology of six shrubs (Crataegus monogyna Jacq., Forsythia viridissima Lindl., Sambucus nigra L., Syringa vulgaris L., Rosa multiflora Thunb., Ziziphus jujuba Miller) and a perennial herbaceous plant [Cynodon dactylon (L.) Pers.] was observed and the emergence dynamics of four annual weed species [Digitaria sanguinalis (L.) Scop., Eleusine indica (L.) Gaertner, Setaria glauca (L.) Beauv., Setaria viridis (L.) Beauv.] were studied from 1999 to 2004 in northern Italy. A correlation between certain events and weed emergence was verified. S. vulgaris and F. viridissima appear to be the best indicators: there is a quite close correspondence between the appearance of D. sanguinalis and lilac flowering and between the beginning of emergence of E. indica and the end of lilac flowering; emergences of S. glauca and S. viridis were predicted well in relation to the end of forsythia flowering. Base temperatures and starting dates required to calculate the heat unit sums to reach and complete the flowering phase of the indicators were calculated using two different methods and the resultant cumulative growing degree days were compared.     

Calculation of sample size in survival trials: the impact of informative noncompliance

Sample size calculations for survival trials typically include an adjustment to account for the expected rate of noncompliance, or discontinuation from study medication. Existing sample size methods assume that when patients discontinue, they do so independently of their risk of an endpoint; that is, that noncompliance is noninformative. However, this assumption is not always true, as we illustrate using results from a published clinical trial database. In this article, we introduce a modified version of the method proposed by Lakatos (1988, Biometrics 44, 229-241) that can be used to calculate sample size under informative noncompliance. This method is based on the concept of two subpopulations: one with high rates of endpoint and discontinuation and another with low rates. Using this new method, we show that failure to consider the impact of informative noncompliance can lead to a considerably underpowered study.     

Seasonal dynamic of plant phenophases in Beijing—A case study in Beijing Botanical Garden北大核心CSCD

Aims Seasonality is the typical characteristic of plant landscape in Beijing, including seasonal dynamics of plant phenology. We analyzed the seasonal changes in phenology of 120 deciduous trees in Beijing Botanical Garden, with additional efforts on an innovative methodology in studying plant phenology. Methods Based on the standards of the Chinese Phenological Observation Method, three-level Phenological Code (a, b, and c) was used to recode the phenology data. Our data analysis was performed with “pentad” (5-day period) in 24 Solar Terms. Analytical methods include a frequency distribution method to explore the division of phenophases and their dynamic constitution. The frequency distribution statistics in SPSS 20.0 were applied to explore the temporal dynamics in occurrence time and duration for different types of phenophases. Important findings We found that: The division of phenological seasons and their phenological constitution as: 6th–19th pentad for Spring, with 54.03% of the whole phenophases that are featured with sprouting, leaf spreading and flowering; 20th–45th pentad for Summer, with 12.95% of phenophases that include conclusions of leaf spreading for all trees, intensive fruiting, fewer flowering, and autumn-leaf scenery in late summer; 46th–59th pentad for Autumn, with 27.19% of the phenophases that are characterized with leaf discoloration and defoliation, some fruiting, and very few flowering; and 60th pentad for Winter, with 0.6% of phenophases that are all constituted with defoliation. The temporal distribution pattern of different kinds of phenophases is as follows. The leaf-unfolding phenophases span from 3rd to 23rd pentad and averagely last for 3.27 pentads, with Sorbaria kirilowii as one of the earliest leaf-unfolding species. The leaf coloration phenophases happen between 40th –63rd pentad, with Tilia mongolica and Armeniaca sibirica as the earliest species to show fall-color leaf. The autumn-leaf duration lasts for 8.2 pentads in average, with Euonymus alatus and Sambucus williamsii as the typical species that show longer leaf duration. The leaf period averagely lasts for 44.2 pentads, with Abelia chinensis, Salix matsudana and Kerria japonica holding the longest leaf time. The flowering-type phenophases happen during 1st–53rd pentad, with 8th–23rd pentad as the best ornamental period, and three species (Chimonanthus praecox, Jasminum nudiflorum and Ulmus pumila) as the earliest blooming species and Elsholtzia stauntoni as the last one to bloom. The flowering period lasts for 6.7 pentads in average, with Sorbaria kirilowii, Hibiscus syriacus and Lagerstroemia indica showing the longest flowering time. The fruiting-type phenophases happen between 8th–59th pentad, with Ulmus pumila and Lonicera fragrantissima as the earliest species for fruit maturation. The fruiting duration averagely lasts for 29.0 pentads, and those species that do not lose fruits during the winter and some other species with longer fruit holding period though falling fruits completely in winter such as Viburnum melanocarpum and Physocarpus opulifolius ‘Luteus’ have longer ornamental time of fruit scenery. Compared with a counterpart research in the 1980s, this study reveals that spring in 2017 came earlier by a pentad than that 30 years ago while autumn came later by 3 pentads; additionally, autumn duration shortened by 2 pentads while summer duration prolonged by 4 pentads, resulting in larger differences between the duration of the four seasons. © Chinese Journal of Plant Ecology.     

Two examples of the interplay between field observations and laboratory experiments from 35 years of research with planktonic organisms

Two studies of complicated ecological phenomena in Lake Maarsseveen (The Netherlands) are presented to illustrate that a combination of field and laboratory analysis might be a successful approach. In the first one, the yearly varying ratio of population abundance of two diatoms, Asterionella formosa and Fragilaria crotonensis during early spring is explained by a combination of abiotic and biotic factors. A fungal parasite blocks population development of the first species at temperatures higher than 3–5 °C . The second species then competes successfully for phosphate and develops a large population. The interaction between Asterionella and the fungus proved to be intricate. Several physiological mechanisms operate together and combined with variable climatic factors makes the prediction of what species will be dominant, impossible. In the second example diel vertical migration of the hybrid Daphnia galeata × hyalina is analysed in the field and the laboratory. Migration is confined to six to seven weeks in June–July when large shoals of juvenile perch are present in the pelagic zone of the lake. These fish exudate a kairomone that enhances the reaction of Daphnia to relative increases in light intensity of dawn. Especially accelerations in rate of relative increases enhance swimming velocity. The extent of enhancement depends, however, on the concentration of the kairomone and on food concentration. A Decision Making Mechanism is introduced and the relation between the response mechanism and the adaptive relevance of diel vertical migration is made.Finally considerations about research strategies and the importance of fundamental research are made. It is concluded that the development of limnology and aquatic ecology might be in danger when the present tendency to give prevalence to applied research continues.     

THE NARWHAL, MONODON MONOCEROS, IN THE NORWEGIAN HIGH ARCTIC

Narwhals ( Monodon monoceros ) are known to frequent the waters of the Norwegian arctic archipelago of Svalbard. An attempt is made to summarize narwhal observations from the Svalbard area, and from this to deduce their distribution. Observations have been gathered from the literature, sealing vessel log books and official statistics. Interviews have also been conducted with residents of Svalbard. I con&de that narwhals are most frequently observed in the area off the north-west corner of Spitsbergen.     

Estimation of Several Missing Values in F-Square Designs

The present study deals with the estimation of several missing values in F-square designs. The estimating equations for the non-iterative least squares estimation of Missing Values and explicit expressions for the estimators of the particular patterns of Missing Values are presented. This procedure is illustrated with the help of a numerical example.