Croatian Journal of Forest Engineering (Apr 2011)
Vegetation Fetures of Beech Forests of Psunj, Papuk and Krndija Mountains
Abstract
The Slavonianmountains have an important place in the floristic and vegetation picture of the continental part of Croatia. For the most part, the forest cover of this region consists of common beech stands (Fagus sylvatica L.). Many authors have worked on defining plant communities of common beech in the northern part of Croatia in the last ten years. Even though this has greatly contributed to get a better understanding of them,many questions have remained open. This is so because the research wasmostly conducted on smaller geographical scale where local conditions (specific microhabitat, anthropogenic influences, etc.) significantly affected the phytosociological analyses. On the other hand, it is rather difficult to carry out the analyses on a larger geographical scale because many regions and/or vegetative types are still scarcely covered by relevés. The goal of this study is to analyze the floral composition of beech forests of Psunj, Papuk and Krndija mountains, which have not been sufficiently studied so far. The next goal is to define and draw boundaries between plant communities, and also to analyze some of the ecological and phytogeographical features. During field studies of beech forests of Psunj, Papuk and Krndija mountains, 88 relevés were made using central European Braun-Blanquet methodology. The relevés have been compared with the relevés of similar vegetation in the wider geographical region (N Croatia, N Slovenia, S Hungary). The analysis included 1509 published relevés of 13 associations from Slovene Phytosociological Database (Šilc 2006) and Croatian database of forests vegetation (Krstonošić et al. 2007) – Lamio orvale-Fagetum, Cardamine savensi-Fagetum, Isopyro-Fagetum, Vicio oroboidi-Fagetum, Hacquetio-Fagetum, Helleboro odori-Fagetum, Carici pilosae-Fagetum, Festuco drymeiae-Fagetum, Galio odorati-Fagetum, Polysticho setiferi-Fagetum, Luzulo-Fagetum, Castaneo-Fagetum i Blechno-Fagetum. The numerical analysis of the floral composition was made (cluster analysis, NMDS), as well as the analysis of ecological variables (DCA). To describe ecological conditions, Ellenberg’s indicator values were also used. Clasification was made by cluster analyses in PC-ORD (McCune&Mefford 1999). NMDS was made by R using Vegan (Oksanen et al. 2006) and DCAwas made by CANOCO 4.02 (Ter Braak and Šmilauer 2002). Slavonian hills are situated in the eastern part of Croatia, on the border of the Pannonian and Illyrian floristic area. The area is bordered by themountains of Papuk (953ma.s.l.) and Krndija in the north-west and north, and by the mountains of Psunj (989 m a.s.l.), Požeška gora (616 m a.s.l.) and Dilj (471m a.s.l.) in the south-east and east. The average annual air temperature in the researched area is around 11 °C, and it increases from the west to the east. January is the coldest month of the year, and July is the wormest. The average annual amount of precipitation decreases from the west to the east. The geological structure is quite diverse. Most of the mountain range is made of silicate and sandstone rock, while parts of Papuk and Požeška gora, and most parts of Dilj are made of limestone and marlstone. We have established three associations of beech forests that can be divided into acidophilic beech forests (Luzulo-Fagetum), submountainous beech forests (Festuco drymeiae-Fagetum luzuletosum and caricetosum pilosae) and mountainous beech forests (Cardamino savensi-Fagetum), (Fig. 2, 3, Tab. 1). Ass. Luzulo luzuloidi-Fagetum This association has already been reported in the study area. These stands are established on acid substrates on steep slopes (Fig. 4, 5). They have very poor floral composition. Furthermore, typical stands are dominated by Luzula luzuloides and this mainly occurs on the northern slopes; there are also stands dominated by Vaccinium myrtillus, which occurs in slightly warmer habitats (cf. Tab. 1 and 2). Ass. Festuco drymeiae-Fagetum In the study region of Psunj, Papuk and Krndija mountains, two groups of relevés could be distinguished, even though there is no sharp distinction between them (Fig. 2). A more acidophilic group (subass. luzuletosum), where Festuca drymeia is dominant with a significant presence of Luzula luzuloides, comes in great complexes at higher altitudes and ismore present in the western and northern part of themountains. In the southern and eastern part, it can be found in small patches. The domination of the Carex pilosa is significant for the other group (subass. caricetosum pilosae). It can be found at lower altitudes and it ismore present in the eastern and southern part of themountains. In the floristic sense, it differs from subass. luzuletosum with a greater participation of species such as Carpinus betulus, Quercus petraea, Tilia tomentosa and others. In the area of the association, in the ditches and basins, there is a significant presence of species such as Polystichum setiferum, Dryopteris filix-mas, Acer pseudoplatanus, Sambucus nigra, etc. (Tab. 1, 2, Fig. 3, 4). Having analyzed the submountainous beech forests in the region of Psunj, Papuk and Krndija mountains, the question remains whether there are two associations, or different subassociations within the same association. To solve the status and relationship with the related associations, it is necessary to make a study that will include all submountainous beech forests in a wider geographical area. The description and systematic position of this association is a topic of much debate in phytosociological literature. We are of the opinion that none of the nomenclature combinations are satisfactory. Ass. Cardamino savensi-Fagetum Beech stands grow in the upper region of Mt. Papuk (over 700 m a.s.l.) and they can be clearly distinguished from all other studied stands by their floral composition. By comparing it with the relevés of beech forests fromliterature, it has been undeniably established that this was the case of mountainous beech forests of the suballiance Lamio orvalae-Fagetum. By its floral composition and ecological characteristics, these forests are most similar to those described under the name Cardamino savensi-Fagetum in Slovenia. Slavonian mountains are a region of well-indented relief, where various base soils, soil depths, expositions, etc., occur in a very small space. Consequently, forest plant communities appear in a delicate mosaic of different vegetation types, which often alternate and whose boundaries are usually not clear-cut. The composition of beech forest flora of Psunj, Papuk and Krndija, as well as the whole area of Slavonian mountains is characterized by a smaller number of species compared to beech forests of the Dinarian region and western Croatia. For the most part, some Illyrian species (Lamium orvala, Calamintha grandiflora, Cardamine trifolia, Rhamnus fallax and Euphorbia carniolica) are missing or come up very rarely, which has also been noted in some earlier studies. Sizeable regions of beech forests of Slavonian mountains are still quite inadequately explored from a phytosociological point of view. This is mainly the case with the westernmost and north-easternmost regions (Fig. 1). In order to solve the remaining open questions and to better define plant communities, it is necessary to study these regions as well.
