Abstract: BACKGROUND: Atypical myopathy (AM) in horses is caused by the plant toxin hypoglycin A, which in Europe typically is found in the sycamore maple tree (Acer pseudoplatanus). Owners are concerned about whether their horses are in danger if they graze near maple trees. HYPOTHESIS/OBJECTIVES: To measure hypoglycin A in the most common maple tree species in the Netherlands, and to determine whether concentration of toxin is a predictor of AM in horses. METHODS: A total of 278 samples of maple tree leaves, sprouts, and seeds were classified by species. Mean concentrations of hypoglycin A were compared for the type of sample, the season and the occurrence of AM in the pasture (non-AM versus AM). Statistical analysis was performed using generalized a linear model (SPPS22). RESULTS: Almost all Acer pseudoplatanus samples contained hypoglycin A, with concentrations differing significantly among sources (P < .001). Concentrations were significantly higher in seeds from the AM group than in seeds from the non-AM group (856 ± 677 and 456 ± 358 mg/kg, respectively; P = .039). In sprouts and leaves this was not the case. Acer platanoides and Acer campestre samples did not contain detectable concentrations of hypoglycin A. CONCLUSIONS AND CLINICAL IMPORTANCE: Acer platanoides and campestre seem to be safe around paddocks and pastures, whereas almost all Acer pseudoplatanus samples contained hypoglycin A. In all AM cases, Acer pseudoplatanus was found. Despite significantly higher concentration of hypoglycin A in seeds of pastures where AM has occurred, individual prediction of AM cannot be made by measuring these concentrations because of the high standard deviation.

Abstract: The main focus of this paper was the dynamics of Fraxinus angustifolia tree spatial patterns after the frequency of flooding events has markedly declined, especially as regards competition with Carpinus betulus and Acer campestre, the most rapidly expanding species in alluvial hardwood forests in Central Europe. The study was conducted in alluvial forests at the confluence of the Morava and Dyje rivers in the Czech Republic. A pair correlation function was used to describe the variability in tree density. Analyses were carried out for datasets from 1973, 1994 and 2006. Over the study period, F. angustifolia populations were characterised by stagnation in the number of individuals, while the number of C. betulus and A. campestre trees increased. Recruitment rates of F. angustifolia were the lowest of all species with the exception of Quercus robur. Recruits of F. angustifolia showed a strong connection to newly available space after decay of the Q. robur layer. Analysis of the elevational distribution of populations showed an increase in the stand intersection of tree species. In the absence of regular floods, F. angustifolia comes into direct competition with C. betulus and A. campestre, which are more adapted to grow in densely shaded, closed stands.

Abstract: The role of the robin as a determinant of heterotrophic consortia is considered. The robin is a consort of determinants of autotrophic consortia, which core is represented mostly by dominating species of deciduous trees (Quercus robur Linnaeus, 1753, Tilia cordata Miller, 1768, Acer platanoides Linnaeus, 1753, Acer campestre Linnaeus, 1753), and also by sedges (Carex sp.) and grasses (Poaceae), connected with the determinants by fabric links. The robin also belongs to the concentr of the second and higher orders as a component of forest biogeocenoses and it is also the main determinant in species composition of the insects inhabiting bird nests. As a result of the taxonomic analysis of invertebrates in the robin nests, it has been found out that the most numerous class was Insecta (9 orders and 27 families), with the dominance of Coleoptera (30.7 %). The nidicolous fauna of the robin (38 species) was dominated by zoophages along with parasites and hematophages such as Hippoboscidae (46.4 %). The percentage of phytophages and saprophages among the invertebrate nest inhabitants was somewhat less (21 % each), then followed necrophages (12 %). Zoophages and parasites also dominated according to the number of objects in the nests (42 %; n = 150), the less was the portion of phytophages (34 %), saprophages (18 %), and necrophages (6 %). The highest number of species and objects of zoophages was recorded for climax and mature biocenoses (oak forests in NNP “HL” and pine cenoses in NNP “H””).

Abstract: In November 2013, Scolytus koenigi Schevyrew, 1890 was recorded for the first time in the territory of the Czech Republic (Southern Moravia, at two localities near the village of Lednice). This finding represents the northernmost occurrence of this species in Central Europe. Because the knowledge of the S. koenigi bionomy is very limited, the characteristics of 52 galleries on 10 different host tree fragments were studied. The species was found to develop on dead or dying branches and thin trunks of maples Acer campestre L. and Acer platanoides L. with diameters of 3-12 cm. All of the galleries comprised a 1.6-2.9 mm wide and 8-67 mm long single egg gallery oriented parallelly to the wood grain, with 18-108 larval galleries emerging almost symmetrically on both sides of the egg gallery.

Abstract: The present work has explored the influence of immediate microclimate conditions associated with different slope altitude on metabolic processes in leaves of woody species. In the recent years, climate change tending to aridity features enhancement, have made more pressing the forests survival and the trees adaptive capabilities studying. The problem of natural forests conservation and restoration is relevant inUkraine as well, especially in the Steppe zone, because of the forest ecosystems developing under the unfavorable conditions of geographic mismatch; therefore forests are very sensitive to any environmental changes. The study was carried out on the territory of Bellegarde’ Prisamarsky International Biosphere Reserve (48°45'01.56"N 35°28'31.09"E) in the natural old-growth (more than 85 years old) mixed deciduous forest. Studied areas have been located on the southern slope of the river Samara right steep bank in the lower (52 ma.s.l.), middle (74 ma.s.l.) and upper (96 ma.s.l.) altitude of the slope. Autochthonous arboreal flora of natural forest was represented by the edificatory species Quercus robus L. and Fraxinus excelsior L., and some co-dominant species including Tilia cordata Mill., Acer platanoides L., Acer campestre L., and Ulmus laevis Pall. The objects of study were chosen in the upper tier ( F. excelsior , an ash) and lower tier ( T. cordata , linden) of natural forest. The gradient character of increasing temperature and light levels dependent on slope altitude together with reducing relative humidity level under the canopy of trees was established. This direction of the local changes in the environmental factors was defined as conventional increase in aridity traits at moving upwards on slope. Trees leaves metabolic responses to these local changes have been identified. The leaves of F. excelsior and T. cordata were selected from 5-7 trees in each parts of the slope in May 2016. Leaves chlorophyll (total level, Chl a, and Chl b) content and antioxidant enzyme catalase activity were measured. Decreasing amount of chlorophyll in leaves of both tree species at the middle and upper parts of the slope compared with index on lower part were found, respectively at 15% and 20% for linden, and at 23% and 33% for ash. Correlation coefficients of total chlorophyll content with light intensity, temperature and relative humidity were similar in linden leaves (respectively, r = - 0.83, r = - 0.98, and r = 0.96) and ash leaves (respectively, r = - 0.84, r = - 0.99, and r = 0.97). In contrast, catalase activity in leaves of T. cordata and F. excelsior had opposite directions of change along the slope altitude. Catalase activity in linden leaves decreased by 1.4 and 2.0 times at the middle and upper level relative to the bottom part of the slope, while enzyme activity in ash leaves increased 1.1 and 1.5 times respectively. Correlation coefficients of catalase activity in T. cordata leaves with light, temperature, and humidity were high, respectively r = - 0.93, r = - 1.00, and r = 1.00. At the same time, dependence of F. excelsior leaves catalase activity has been expressed by such coefficients: r = 1.00, r = 0.89 and r = - 0.93, respectively for light, temperature, and humidity. Thus, a very high sensitivity of arboreal trees leaves photosynthetic and antioxidant processes even to slight changes in environmental features at different slope altitude was established. T. cordata and Fraxinus excelsior showed various adaptive strategies to altitude-associated changes of microclimate conditions including temperature and light intensity increase together with relative humidity decrease. In linden leaves, the positive dependences were established between both metabolic processes and humidity together with negative influence of temperature and light. In leaves of ash, chlorophyll content also increased due to humidity level, while catalase activity increasing was associated with light and temperature growth. Study results can be used to assess the adaptive potential of tree species to enhancing aridity traits, as well as for design of planted forests resistant to climate change.

Abstract: Forest understory species such as shrub and herbaceous layer, have received little attention in long-term studies. Knowledge of the diameter and the height of trees are fundamental for developing growth and yield models in forest stands. Overstory composition of the Sikfőkut Project site was dominated by sessile oak–Turkey-oak forest (Quercetum petraeae-cerris Soo 1963). Similarly to other European countries an oak decline occurred in Hungary oak woodlands at the end of 1970’s and about 63% of the oak trees perished in our site. The potential for oak species regeneration was a very low over the period of 1982-2012. Four nonlinear height-diameter functions were fitted and evaluated for Sikfőkut site based on a data set consisting of 2025 individuals for three dominant woody species (Acer campestre L., Acer tataricum L. and Cornus mas L.) and detected any short-term changes in these equations following dieback of oak canopies. These height– diameter equations increase our knowledge of the growth of these species; therefore will enable us to improve management planning in oak forests.

Abstract: Information about the diameter and the height of woody species is fundamental to developing growth and yield models in forest stands. Ten nonlinear height–diameter functions were fitted and evaluat...