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2014-07-23
Conserving the richness of forests on eskers

The relatively untouched beauty of the Latvian nature is appreciated by the locals as well as tourists.  At the same time, nature can not completely escape either natural or human induced disturbances that change the landscape, the composition of tree and plant species, or sometimes create unfavourable conditions for certain species. World scientists have developed methods for managing nature in the most nature friendly way that would limit harm to the nature. However, several world known methods are still not practiced in Latvia. For example, not many people in Latvia know that fire in forests is not only a disastrous element, but in specific conditions it can be a nature friendly process.

What are eskers?

Although Latvia does not have high mountains or deep valleys, the relief of Latvia creates a rather unique and beautiful landscape, because most of the land is covered by relief formed during deglaciation. In places where beneath the glacier there had been hard dolomite and limestone rocks, water streams could not erode and melting waters brought in sand and gravel in the tunnels of the glacier. As the glacier melted, they became visible as zigzag ridges and hill chains. These ridges are called eskers.

Eskers are very rare in Latvia; the best know eskers are located in the Latgale region – Numernes valnis, Grebļkalns and eskers near Andrupene, in other regions – Little Kangars, Big Kangars and Ogre’s Blue Mountains.

The impressive biodiversity of eskers

The most common forests growing on eskers are pine forests that in the land cover due to the calcareous soil have a unique and rich species composition. Since eskers and the forests growing on them are rare in Latvia, these forests are specially protected.

Pine forests are one of the forest types that grow best on eskers. The specially protected habitat „Coniferous forest on, or connected to, glaciofluvial eskers” is one of the rarest protected forest types in Latvia. Altogether, there are only about 14 km2 of these forests in Latvia. Eskers are located in the southeaster part of the Rāzna National Park, reaching AS Latvia’s Forests territories in the near border area of the National Park. 
 
 
 
 

Why are forests on eskers so rich in unique, rare species?

One of the most notable characteristics of forests on eskers is their species richness. Natural disturbances, such as forest fire or small disturbances by pests are essential for preserving their biological diversity. Although such disturbances destroy some of the trees, overall they create new living space for various organisms and foster the emergence of a diverse species composition; hence such disturbances are important for long term survival of species typical to eskers.

What can we do to preserve diversity?

Dry pine forests are negatively affected by natural eutrophication and the consequent disappearance of plants that require sunlight. As the forest overgrows, various flowers and butterflies dependent on those flowers disappear. In order to preserve this habitat, it is essential to maintain an open and bright pine forest.

Fire destroys spruce and the undergrowth, whilst the pine trees mostly survive the fire. As the land cover burns, mineral soil is uncovered and the land cover becomes considerably more diverse and provides suitable living conditions for a significantly larger number of species. Many species, for example, spiders have adapted to fire disturbances and promptly leave their habitat as the fire spreads. At the same time, some beetles migrate to the burnt tree trunks to lay eggs in the warm bark. Soon the burnt soil nurtures mushrooms and various plants. The forest continues to live on and some unique living organisms are provided with appropriate living conditions.

Unfortunately, the quality of forests growing on eskers is dropping. In Latvia, these forests are overgrowing with spruce and a thick layer of moss. Due to economic reasons, man has significantly limited natural disturbances in forests. Even if wildfire does occur in forests on eskers, the burnt trees are removed. However, for several species this is an unfavourable development, since they require fire disturbances.
 
Is this something new?

In Scandinavia (Sweden, Finland) controlled fire is a forest management method with already rather long history. It is used for preparing soil in forest clearings to foster forest renewal, as well as in dry pine forests where it is essential to imitate natural fire disturbances. With the help of this method conditions appropriate for various rare species can be created. The method is used in strictly controlled, usually small areas and is closely supervised by fire safety experts. In Finland, the use of controlled fire is taught in universities to all students of forestry.

In order to achieve nature conservation targets, in certain territories it is essential to implement the forest management methods carefully developed in Scandinavia, and in close supervision of fire safety experts in small territories burn down moss soil cover to make way for larger species diversity. The legislation of Latvia allows using fire when for specific forest habitats it is needed as a forest management method that can improve the habitat conditions. In 2013 the Cabinet of Ministers also passed regulations that outline the exact procedure of using controlled fire as a forest management method.  









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