Phenology is the study of periodic biological events in the plant world that are influenced by the environment. Temperature increase in spring season can advance the spring phases, but warming in autumn and winter may slow the fulfillment of chilling requirements and lead to later onset of spring events. This study examined different genotypes of walnut trees under environmental conditions, and measured the cold demand, heat requirements, and average time from budburst till flowering for 28 walnut genotypes. The information obtained provides a better understanding of the phenological temperature response of walnuts that will be useful for walnut production and will also contribute to the development of adaptation measures in the light of the expected climate change.

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Walnut is a species of high vigour, with relatively slow growth, and the size of trees grows with each year of growth. Accumulation of wood biomass, and respectively, productivity, is a resultant synthesis of physiological processes and interaction of trees with environmental factors. The authors have assessed growth characteristics of genotypes standing on their own roots in the sands area of Oltenia (Romania). In terms of tree height, it ranged from 8.53 m to 18.00 m, while trunk circumference varied between 40 cm and 229 cm, in genotypes with ages between the 16 and 44 years. Environmental factors, by influencing cambium tissue activity, cell differentiation processes, cell walls growth processes, are inducing particular characteristics of annual rings, in terms of size. The average value of growth ring was 7.09 mm, with a minimum of 3.53 mm, a maximum of 13.94 mm and variation coefficient of 40.20%. The obtained results show that climatic and edaphic factors of the culture area are influencing the trees growth and development and indicate a good adaptability of genotypes to these conditions.

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The aim of this study is to provide information on the phenology of urban spring season, of some species of ornamental trees and shrubs, in the light of climate changes occurred over the recent decades. Ten species of ornamental shrubs and trees cultivated in two areas of a town located in southwestern Romania were studied. It was found that the spring season phenology of the studied species is dependent on the climatic year, in recording differences between the number of days from November 1 and the beginning of each spring phenophase, both from one species to another and from one climatic year to another, and also from one area to another; the spring phenology starting earlier in the urban area regardless of the species and the climatic year. Higher temperatures, rising from one year to another, are speeding-up the onset and development of spring phenology, regardless of species, and the urban climate through the effect of urban heat island leads to even earlier onset of spring phenophases and shortening of the growing season, so that by phenological differences existing within the species from one climatic year to another and from one climatic zone to another, spring season phenology can be considered an indicator of temperature rise.