The past, present and future tasks of Hungarian dendrological research.
Hungarian dendrological research (research of living woody plants) has more than 200 years old history; the first general work by János Keresztély Grossinger was published in 1797. Further basic works in our time yet are: Forest Botany by Lajos Fekete and Sándor Mágócsy-Dietz (1896); and the chorological work, Distribution of trees and shrubs of sylvicultural importance in the region of Hungarian State by Lajos Fekete and Tibor Blattny (1913). A few dendrologists and many botanists have helped to get better knowledge of Hungarian dendroflora. From the point of view of taxonomy, chorology and habitat - which are interested by field botanists - it can be said that knowledge is fairly heterogeneous. There are sufficient information about most of the rare (protected/endangered) woody plants (an about 50 species) and the important adventives, above all invasive trees and shrubs (an about 10 species). From these two groups beyond there are only few taxa which can be said thoroughly worked up and known (e.g. Castanea sativa, Cornus mas, Fraxinus spp., Quercus spp.). List of the dendrotaxa, hardly known in the above-mentioned point of view is rich in species that are important for forestry or horticulture (e.g. Alnus glutinosa, Acer spp., Betula pendula, Corylusavellana and most of Salix spp.), supplemented with other species (e.g. Clematis vitalba, Colutea arborescens, Lonicera xylosteum, Padus avium, Sambucus nigra, Staphylea pinnata, Viburnum spp.).Followings can be asked from our field botanists: i) look for a specialist in cases of critical dendrotaxa; ii) a circumspect identification is necessary - especially in the case of leaves - by right of great number of samples from the adequate part of shoot; iii) keep in view frequent hybridization (e.g. in the case of Betula, Crataegus, Pyrus, Tilia), and frequent appearance of hybrids (e.g. Betula × rhombifolia, Cerasus × eminens, Salix × rubens); iv) appearance of interim forms are usually typical in the cases of species classified into aggregate species (e.g. Quercus petraea agg., Qu. pubescens agg.); v) take intraspecific taxa according to various ecological demands, area, morphological differences into consideration; vi) culture variations cannot be treat as an equal with the species (e.g. Populus spp., Salix spp.); vii) natural ↔ artificial area have to be separated; viii) lend a helping hand in getting taxonomical knowledge of hardly known dendrotaxa.
Grey alder (Alnus incana (L.) Moench) structure.
Grey alder occupies 190.6 thousand ha or 6.8% of forests in Latvia. Stand structure has infl uence on its productivity and dynamics. Materials for the studies were collected in the period from 2005 to 2007. For the investigation 47, grey alder stands, representing various ages, site index and density conditions from Jelgava, Bauska, Ogre, Aizkraukle, Jēkabpils, Valmiera, Talsi and Krāslava regions were used. The majority of these stands have not been managed previously and have been originated from shoots. A total of 11 – 30 year old grey alder stands were investigated using a 6 tree sample plot method. Trees were grouped in 2 cm diameter classes according to breast height diameter. Trees according to reduction numbers were grouped in natural diameter classes. In 11 – 15 year old stands trees were within 4 5 two centimeter diameter classes, in 16 30 – year old stands – within 6 12 classes. The proportions of trees in smallest and largest diameter classes not exceed 1 3%. The distribution of grey alder trees in natural diameter classes in 2/3 of cases match up with theoretical Tjurin distribution, resemblance was not detected in cases, when there are large proportions of thin trees in stand. Cumulative percent values of the number of trees and stand volume are were not dependent on site index. Relationship between cumulated value of the number of trees (y) in percents and cumulated value of stand volume (x) was described by parabolic equation (R2 = 0.997, p < 0.05). Fifty percent from stand volume were made up from 70% of thinnest trees. Regression equations describing dependence of tree height, height of live crown base, and length of crown from tree diameter were developed.
Assessment of Ground Regeneration around Borehole Heat Exchangers between Heating Seasons in Cold Climates: A Case Study in Bialystok (NE, Poland)
Based on the experimental studies, the process of ground regeneration around the borehole loaded with brine-water heat pumps working exclusively for heating purposes in the period of four consecutive heating seasons in a cold climate was presented. The research was conducted in north-eastern Poland. The aim of the work is to verify the phenomenon of thermal ground regeneration in the period between heating seasons on the basis of the recorded data and to check whether the ground is able to regenerate itself and at what rate. It was noticed that the ground does not fully regenerate, especially during heating seasons with lower temperatures. In the analyzed period, from 22 September 2016 to 12 October 2020, the ground probably cooled irreversibly by 1.5 °C. In order to illustrate and evaluate the speed of changes in the ground, the one’s profile with an undisturbed temperature field was presented for each month of the year. The presented results can be a very important source of information for the analysis of geothermal conditions occurring in the ground. They can be used to verify mathematical models and conduct long-term simulations that allow us to see the complexity of the processes taking place in the ground.