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This work focuses on calculating the amount of control reserve, which can be provided by a pool of renewable power plants on the next day. The power forecast of wind and solar power plants depends on the weather forecast, which always contains errors. A merger of individual plants at different locations is advantageous in order to reduce the overall forecast error. Still, the amount of control reserve needs to be determined with a high level of reliability. For the calculation, a probabilistic approach based on historical and current weather data is chosen. In order to model the spatial dependencies of the forecast errors between individual plants, R-vine copulas are used. In the copula theory, R-vine copulas provide high accuracy in modelling the dependency of stochastic variables. The methodology is validated and compared to three alternative approaches with a use case of 32 wind and solar plants. The calculated amount of control reserve provided and the achieved reliability proves to be superior to alternative approaches. Additionally, the required reliability level is varied to investigate the impact on the amount of control reserve, which can be offered with the pool. [ABSTRACT FROM AUTHOR]

This work focuses on calculating the amount of control reserve, which can be provided by a pool of renewable power plants on the next day. The power forecast of wind and solar power plants depends on the weather forecast, which always contains errors. A merger of individual plants at different locations is advantageous in order to reduce the overall forecast error. Still, the amount of control reserve needs to be determined with a high level of reliability. For the calculation, a probabilistic approach based on historical and current weather data is chosen. In order to model the spatial dependencies of the forecast errors between individual plants, R‐vine copulas are used. In the copula theory, R‐vine copulas provide high accuracy in modelling the dependency of stochastic variables. The methodology is validated and compared to three alternative approaches with a use case of 32 wind and solar plants. The calculated amount of control reserve provided and the achieved reliability proves to be superior to alternative approaches. Additionally, the required reliability level is varied to investigate the impact on the amount of control reserve, which can be offered with the pool. [ABSTRACT FROM AUTHOR]

The research carried out refers to a study of 460 individual birdsfoot trefoil (Lotus corniculatus L.) plants in order to show relations between the cultivated seeds size and the weight of the root system, on one hand, and between the radicular system and the nodosity formation capacity of the root system (number and weight), on the other hand. The results obtained have revealed the existence of direct positive relations between these properties of the birdsfoot trefoil plants. The magnitude of these attributes values is determined by the size of the seeds used for sowing. [ABSTRACT FROM AUTHOR]

Abstract: The spatial distribution of individual crop plants in the field is important for crop growth, yield production, and crop–weed interactions, but the role of spatial pattern has not been appreciated in agricultural research. A quantitative measure of degree of spatial uniformity/aggregation of individual plants would be very useful in this context. We digitized photographs of field plots of weed-infested spring wheat sown in uniform, random and normal row patterns at three densities (204, 449 and 721seedsm−2), and described the locations of individual wheat seedling as x- and y-coordinates. We analyzed the spatial pattern of these plant locations in two ways. One approach is based on Voronoi or Thiessen polygons (also called tessellations or tiles), which delimit the area closer to each individual than to any other individual. The relative variation (coefficient of variation) in polygon area and the mean shape ratio (ratio between the circumference of the polygon and that of a circle of the same area) of the polygons are measures of spatial aggregation. The other approach was Morisita''s index of dispersion, which is based on the mean and variance in number of individuals in sampling units (quadrats). The CV of polygon area, the mean shape ratio of these polygons and Morisita''s index of dispersion, all performed well as descriptions of the degree of spatial aggregation of crop plants. Models using one of these measures of uniformity and sowing density as explanatory variables accounted for 74–80% of the variation in crop biomass production. Despite its simplicity, models with Morisita''s index performed slightly better than models using polygon parameters, accounting for 80–86% of the variation in weed biomass. Simple spatial analyses of individuals have much to offer agricultural research. [Copyright &y& Elsevier]

Abstract To assess the tolerance of fringed sagewort (Artemisia frigida Willd.) to grazing in semiarid sandy rangeland, forty-five fringed sagewort plants of similar size were chosen randomly from sandy rangeland and divided into three cohorts (fifteen plants per cohort) that were subjected to simulated grazing management in 1998. Plants were cut in spring on 24 April and again in summer on 26 July at either 2–3 cm (severe), or at5–6 cm (moderate), or uncut to serve as the control. Plant responses to intensity of cutting were monitored over two consecutive years differing substantially in the amount and seasonal distribution of rainfall. Cutting in spring (moderate or severe) did not influence plant height, average canopy diameter, the number of branches, and specific branching density measured in July 1998. Moderate cutting in summer reduced plant height compared with the uncut treatment but did not influence other plant growth variables in September 1998. However, severe cutting in summer during the reproductive stage strongly reduced plant height, canopy size, the number of branches, individual shoot weight and specific branching density in September 1998 compared with moderate and no cutting and its negative impacts on the growth of this species were evident in the following year. Severe cutting in spring significantly increased the number of flowering shoots, whereas cutting in summer (at either level) reduced the capacity of fringed sagewort to produce flowering shoots. Also, the negative impact of summer cutting on seed production continued in the following year. The production of plant biomass was similar in the three treatments in 1998, but it was significantly lower in cut than uncut plants in 1999. The reduced biomass was due to a decline in plant height, canopy size, number of branches and specific branching density. Compared with the uncut plants, the cut plants tended to allocate a greater proportion of their biomass to vegetative... [ABSTRACT FROM AUTHOR]

Identification of resistance genes in individual plants requires the use of leaves that have homogeneous reactions to the pathogen. The reactions of the first two leaves of seedlings of 12 wheat differential varieties to 20 Erysiphe graminis f.sp. tritici isolates were compared using in vitro tests on detached leaf segments. The expression of resistance and susceptibility did not differ significantly between the first two leaves with the 12 resistance genes tested. Consequently, the identification of specific powdery-mildew-resistance genes in individual plants is possible if approximately 10 segments of the primary and secondary leaves are used, each of them inoculated by one out of a set of 10 differential isolates. The reaction pattern of a plant to the tester isolates is interpreted according to a procedure in two steps, that are easily computerized. Identification of resistance genes in individual plants is particularly useful for resistance studies in heterogeneous plant populations. [ABSTRACT FROM AUTHOR]