Željko Škvorc

Thermophilous deciduous forests in Southeastern Europe

Abstract This paper deals with the numerical elaboration of the database of 1764 relevés of thermophilous deciduous forests assigned by the authors to the order Quercetalia pubescentis in the northwestern part of Southeastern Europe. After elimination of relevés which were dominated by mesophilous deciduous and coniferous tree species, the stratification of relevés was carried out. The TWINSPAN classification revealed eight ecologically and phytogeographically interpretable groups. Additionally the analysis of Pignatti indicator values passively projected on the PCA diagram of the eight groups, and a chorological analysis of individual groups were made. The analyses revealed that all groups in general match with the traditionally accepted alliances, such as Quercion pubescenti-sessiliflorae, Aceri tatarici–Quercion, Quercion confertae, Quercion petraeae-cerris, Syringo-Carpinion, Pruno tenelle–Syrinion, Carpinion orientalis and Fraxino orni–Ostryion. Finally, a synsystematic classification of the elaborated group is proposed, and the nomenclature is harmonised with the International Code of Phytosociological Nomenclature. The results are also presented in a synoptic table together with calculation of the diagnostic species.

The salt marsh vegetation on the East Adriatic coast

Phytosociological characteristics and a rate of endangerment of the salt marsh vegetation in central and southern parts of the east Adriatic coast were studied. A total of 73 vegetation relevés were made and elaborated according to the standard procedures of the Braun-Blanquet method. Numerical analysis of the relevés and life forms was performed. Two associations of the class Arthrocnemetea-Puccinellio festuciformis-Arthrocnemetum fruticosi and Limonio-Artemisietum coerulescentis were recorded, together with the association Juncetum maritimo-acuti of the class Juncetea maritimi. These associations show no significant differentiation with regard to their floristic composition, but only in terms of particular species cover and frequency rates, as well as by life forms and microecological habitat conditions. These are specific habitats, rarely found in the studied area, and highly threatened by human activity (tourism, agriculture).

Ecological and phytogeographical differentiation of oak-hornbeam forests in southeastern Europe

Abstract The aim of the study was to establish the main types of oak-hornbeam (Carpinus betulus and Quercus sp. div) forests on the Apennines, Balkan peninsula and southern Alps and their correlations with the main ecological and phytogeographical gradients in the region. Furthermore, the comparison with the major types recognized in the traditional expert-based classification was done. 1676 relevés of oak-hornbeam forests (alliances Erythronio-Carpinion, Carpinion moesiacum, Physospermo verticillati-Quercion cerris) from the area of the Apennines, Balkan peninsula and southern Alps were collected and entered in a Turboveg database. 508 relevés remained after stratification and were classified with a Modified Two Way Indicator Species Analysis, which resulted in four main clusters that are phytogeographically interpretable, such as (1) southern Apennines, (2) northern-central and central Apennines, (3) central-southern Balkan and (4) north-western Balkan and southern Alps, further divided into subclusters. Pignatti indicator values calculated for relevés of each subcluster were subjected to PCA in order to show the ecological relationships among subclusters, and the spectra of geo-elements were calculated to show the phytogeographical relationship between them. The diagnostic species combination was calculated by a fidelity measure (phi-coefficient) and presented in a synoptic table. Synsystematic classification of the elaborated groups is proposed.

Germination characteristics of Salicornia patula Duval-Jouve, S. emerici Duval-Jouve, and S. veneta Pign. et Lausi and their occurrence in Croatia

Abstract - According to recent molecular analyses of Salicornia, we revised the annual glassworts from the Croatian coast, classified until now only as Salicornia europaea. Two species, a diploid Salicornia patula and a tetraploid S. emerici were recognized. They can be easily distinguished by floral characters, but not only by their habitus, which varies extremely according to environmental factors. Both species differ also in seed morphology. Salicornia patula has dimorphic seeds, with larger central seeds reaching high germination rates. Germination patterns helped to explain the habitat preferences. The species rarely co-occur, however. The rare S. patula occupies drier habitats, on coastal mudflats or sands that are irregularly inundated. It occurs within the assoc. Suaedo maritimae-Salicornietum patulae. Salicornia emerici occupies the lowest coastal mudflats, regularly inundated, where nutrient-rich conditions prevail, and forms an almost monotypical assoc. Salicornietum emerici. Due to the synonymy of S. veneta with S. emerici, we exclude the occurrence of S. veneta in Croatia as an independent taxon.

A phytosociological analysis of the Quercus coccifera L. stands in south Albania (NE Mediterranean)

Abstract The results of a phytosociological investigation of the Quercus coccifera L. stands occurring along the Adriatic and Ionian coasts in south Albania are given. The surveyed stands are localized in the Thermo-Mediterranean and Meso-Mediterranean belts. On the basis of literature and unpublished data, Q. coccifera stands extend from the shoreline up to 680 m of altitude, within the Quercetea ilicis vegetation zone. According to numerical analysis, Q. coccifera stands in south Albania can be divided into two broad groups forming macchia of 3–4 m height and low shrublands [0.5–1.5(-2) m)] defined primarily by degree of human pressure and altitudes. In addition, relevés from Q. coccifera stands in Albania were differentiated from Croatian and Montenegrin the Fraxino orni-Quercetum cocciferae associations. Conversely, Q. coccifera stands in south Albania share several biological and ecological similarities with those of the eastern Adriatic coast: hemicryptophytes prevailed and the chorological spectrum highlights a clear dominance of the steno-Mediterraneans. With respect to indicator values, an important differentiation from the eastern Adriatic associations was shown only in higher light intensity of the stands in Albania.

In vitro pollen germination and pollen tube growth differences among Quercus robur L. clones in response to meteorological conditions

Abstract The impact of meteorological conditions on in vitro pollen germination and pollen tube growth during the initial phases of the development of male flowers in the Pedunculate Oak, Quercus robur, is studied. Phenological observations of male flowers and pollen sampling were performed on the field trial established with grafted Pedunculate Oak clones. During the investigation, weather conditions (absolute minimum and maximum daily air temperature, minimum absolute relative humidity of air and amount of precipitation) were recorded by an automatic meteorological station installed at the field trial. Influence of meteorological conditions on pollen germination and pollen tube growth was studied in the following stages of male flower: (I) during the last ten days of flower bud dormancy, (II) during swelling of the buds, (III) during bud burst and beginning of male catkins elongation, (IV) during the final stage of male flower catkins elongation. High temperatures and low relative air humidity during the bud burst and beginning of the male catkins elongation reduced pollen germination and pollen tube growth. Weather conditions did not significantly affect pollen germination and pollen tube growth during the swelling of flower buds, or in the final stage of male catkins elongation.

Vegetation of trampled habitats in the Plitvice Lakes National Park in Croatia

Abstract The vegetation communities of the trampled habitats in the Plitvice Lakes National Park were studied during 2005 and 2006. With the numerical classification of the relevés, six clusters were obtained, corresponding to the following specific communities: cluster 1 – ass. Matricario–Polygonetum arenastri– the intensively trampled and grazed habitats; cluster 2 – ass. Matricario–Polygonetum arenastri– the only intensively trampled habitats; cluster 3 – ass. Coronopodo–Polygonetum arenastri– very intensively trampled and grazed farmyards; cluster 4 –Trifolium fragiferum community – the trampled surfaces of moist habitats; cluster 5 – ass. Lolietum perennis– the moderately trampled surfaces of roads and yards; cluster 6 – ass. Prunello–Ranunculetum repentis– trampled surfaces of forest roads. The first three clusters belong to the vegetation of intensively trampled habitats of the class Polygono arenastri–Poetea annuae and the last three clusters belong to moderately trampled habitats of the class Molinio–Arrhenatheretea. In the analysis of the ecological factors it is established that separation of the relevés is influenced most greatly by the trampling intensity observed in the field, and of the Ellenberg indicator values, the most important are light, moisture, soil reaction and temperature. Using the analysis of the plant functional traits it is established that therophytes, annuals, biennials, species resistant to trampling and grazing, neophytes and archeophytes prevail in the intensively trampled habitats. In contrast, hemicryptophytes, perennials, and indigenous plant species prevail in the moderately trampled habitats. Representation of the C-S-R plant functional types shows also that trampling as a disturbance factor has a large influence on the differences in the relevés. In the intensively trampled habitats, there is a large proportion of ruderals, while in the moderately trampled habitats there is a large proportion of competitors.

Forest plant community changes in the Spačva lowland area (E Croatia)

Abstract The forests in the Spačva Basin are a complex of lowland forests in the region of Slavonia (eastern Croatia). The present state of the forests is strongly influenced by intensive exploitation and hydro-ameliorative activities carried out in the past. The aim of this study was to consider the extent of changes in species composition, and the extent of environmental changes in forest communities of the Spačva Basin in relation to research conducted between 1969 and 1971. The species composition of four communities (Carpino betuli-Quercetum roboris, Genisto elatae-Quercetum roboris aceretosum tatarici, and caricetosum remotae, and Leucojo-Fraxinetum angustifoliae) is studied by comparing 41 old and 57 new relevés. Changes were estimated using ordinations (RDA, CCA, DCA) and changes in species frequency and cover. A general trend of moisture reduction was noticeable among all communities. All vegetation types are becoming floristically more similar. An increase in frequency and cover of flood intolerant woody species (such as Carpinus betulus, Cornus sanguinea, Tilia tomentosa, and Acer tataricum) as well as a decrease of vernal species related to wet habitats are particularly evident. The succession of all studied communities is resulting in loss of the mosaic community pattern characteristic of lowland alluvial forests.

Vegetation of Croatia: Phytosociological classification of the high-rank syntaxa

Abstract Croatia is among the most ecologically diverse and floristically rich countries in Europe, with a great variety of communities. The vegetation elaboration according to the standard central European method was initiated in Croatia at the beginning of the 20th century. In previous overviews of Croatian vegetation, the number of classes and alliances was underrepresented in relation to the country’s floristic richness. Furthermore, the level of knowledge and the amount of available data varied greatly among the various types of vegetation. The aims of this paper are mainly to compile a stabile syntaxonomic list of classes, orders and alliances dominated by vascular plants in Croatia and to adjust Croatian vegetation to the new European syntaxonomic system (EuroVegChecklist). It introduces a consistent description of high-rank syntaxa in Croatian. In conclusion, the vegetation of Croatia comprises 66 classes, 121 orders and 201 alliances. The number of syntaxa shows vegetation diversity that is rather high compared to most other European countries; this is related to the high floristic richness and endemism. The list points out the obvious problems and gaps in our knowledge of vegetation in Croatia and can serve as a baseline for the future vegetation studies.

Composition and ecology of the Quercus coccifera L. communities along the eastern Adriatic coast (NE Mediterranean)

The aim of this study is to classify and describe all plant communities with Quercus coccifera covering the entire eastern Adriatic coast and islands from north Croatia to south Albania, and to relate their species composition, chorotypes and life forms to environmental factors using Pignatti ecological indicator values. From total 70 phytosociological relevés, we identified and described four floristically and ecologically distinctive vegetation communities (two new proposed subassociations, one association and stand each) using TWINSPAN and the Braun-Blanquet classification scheme. In Croatia and Montenegro, Q. coccifera is forming macchia within the Fraxino orni–Quercetum cocciferae pistacietosum lentisci. Quercus coccifera occurs only sparsely in south Croatia as a shrubland within Fraxino orni–Quercetum cocciferae nerietosum oleandri subassociation or macchia within the Erico arboreae–Arbutetum unedonis association. Despite the difference in biogeographic position and bioclimates, low shrubby Albanian Q. coccifera stands are more closely related to the Q. coccifera communities from the western Mediterranean. Eastern Adriatic communities appear exclusively within the Querceta ilicis vegetation zone and spread within the meso-Mediterranean belt. They nevertheless are an important part of the regions natural heritage and management plans must ensure that all forms of land are used in a sustainable way.