Tuesday, October 4, 2016

Slovakia 2016 - Nature Protection: National Nature Reserve of Sur

ISSUE DATE: 7 October 2016
CIRCULATION: 60 000 (each)
STAMP SIZE: 27.2 x 44.4 mm 
ENGRAVER: Rudolf Cigánik
STAMP DESIGN: Rudolf Cigánik

Dryopteris Carthusiana. The narrow buckler-fern grows in Europe, rarely in Turkey, northern Iran, the Caucasus and Western Siberia and also in North America. In our country, it is a quite abundant species growing predominantly in humid damper marsh forests in the plains up to mountain regions. It also does well on peat, sand or loamy soils and in slightly shaded places. In exceptional cases we can find it growing in direct sunlight. We can also see it growing on living or dead trees, in the shrub layer or on the banks of streams, rocky slopes or old walls. The narrow buckler-fern is susceptible to a decrease in humidity and probably for that reason, it prefers habitats with a higher level of groundwater which is important for optimal growth and reproduction. 

It is primarily found in forests with a dominance of black alder, grey alder, European white elm and beech. Being part of the herb layer in the forest of Šúr near Svätý Jur, it also grows epiphytically on alder prop roots, above the level of flooded soil. It grows out of a rhizome from which long stalks with 2 or 3 pinnate compound leaves that have a light green blade and a lanceolate shape grow. They are 15 to 80 cm long. The shape of the stalked leaves ranges from lanceolate to ovate. They are saw-tooth edged with long tips. The sori that contain the spores on the lower side of leaves are 0.5-1 cm long in diameter.

Frangula alnus. The glossy buckthorn is a typical shrub that occurs in the marsh alder forest of the National Nature Reserve Šúr near Svätý Jur. The shrub tends to co-exist with grey willow, guelder-rose, European white elm or bird cherry. It grows most luxuriantly in damp and very bright places; the opposite is true as regards places with larger alders and a dense connection of tree crowns. The glossy buckthorn can grow to a height of 5 m, occasionally up to 9 m; therefore it is sometimes incorrectly referred to as a tree. The bark is smooth, black and brown with white dots. The appearance of the bark is caused by numerous white, oval breathing pores, so-called lenticels. Ramnatoxine, a red pigment, is obtained from the bark; in addition, the bark contains free and glycoside bound anthraquinones. It is used for medical purposes and after being processed, it has a laxative effect. It also has anti-helminth, anti-microbial and anti-oxidative effects. The leaves are staggered on easily breakable branches. They are ovate with an entire margin and narrow to a stalk at the base. They are broad at the top and the tip is short and pointed. The leaves are downy but only on the venation. Its flowers are small, green with pink spots and grow as a compound flower in the leaf axils. 

Its fruit is a drupe, violet and black when ripe, green or red when unripe. Consumption of the fruit by birds such as jays, starlings, thrushes and robins leads a relatively effective distribution in the surrounding area. Distribution by flowing water is an interesting method of distribution as the fruit can float the surface of the water for 7-19 days. This is a significant particularly in areas where autumn and winter floods occur. While the glossy buckthorn originates in Europe, Asia and North Africa, in North America it is one of the introduced and invasive species that threaten the original marsh lands and swamps.

Alnus Glutinosa. The black alder is a widespread species occurring in bottomlands, swamp forests, marsh lands and along the shore; away from water, it occurs at locations with high rainfall. Thus, it depends on water because its leaves do not have any mechanism to control transpiration. The black alder does well in acidic soils. Its occurrence ranges from the plains up to mountainous regions. The common alder can grow to a height of 20-30 m. A characteristic of the black alder is its smooth bark which is, however, cracked at the base of the trunk. Its leaves are nearly orbiculate, cut or slightly wedge-shaped on the top. 

The catkins appear before the leaves sprout from March to April. The male catkins grow in groups of 2-3; they are pendulous and purple in colour. The fertile female catkins are woody, brown and reminiscent of small cones. The black alder is a tree species that dominates the forest in Šúr near Svätý Jur, where it creates a so-called genuine alder forest. Regular surface floods lasting for more than 6 months are typical of these forests. Here are optimal conditions for the growth of alder. Due to the high level of moisture and presence of mud, the alder root system is closely connected with the soil attributes, thus being relatively shallow. The black alder often has aerial roots that develop into supporting prop roots. 

It is possible to identify the height of surface floods in the forest according to their size. In addition, the black alder can grow in poor soils due to the symbiosis of roots with nitrogen fixing bacterias of the Frankia genus. The lower part of the alder trunk is sometimes studded with pores, which accelerate the total gas exchange.  This is especially important with soils that contain stagnate water low in oxygen. The alder in Šúr rejuvenate quickly and fast growing young trees can absorb tree stumps that decompose quickly and disintegrate. In general, however, the restoration of alder forests is a problem since the seedlings are very susceptible to drought.

author: Igor Kokavec (Pofis)

Stamp images and description thanks to Slovenská pošta and POFIS

Slovenská pošta