The mature forests of Koitajoki Area in Ilomantsi were studied in the North Karelian Biosphere Reserve Finnish - Russian researches in 1993-1998. Russian researchers from Petrozavodsk (Karelian Research Centre) , St Petersburg (Komarov Botanical Institute) and Moscow (Moscow State University) were involved in the studies.
The goal of the researches was to study the biolgical value of the prevailing forest fragments.
An index of the value of the forest fragments was compiled. The index includes the amount and quality and succession of the decaying wood in the sites. The groups studied were Coleoptera, Diptera, Hymenoptera and aphyllophoraceous fungi.
Coleoptera species were were most numerous in Tapionaho, where there were over 200 spedies found of the total number of 282 found in the studies. Endangered coleoptera were presented by 14 species. The most important one was Cyllodes ater, a beetle only found twice in Finland and already thought to be extinct. Monochamus urussovi and Orthotomicus longicollis are considered vulneralble.
The reserches revealed 502 species of Diptera. Diptera studies were concentrated on the family Mycetophilidae, which is an important group in forest wood webs. Six of the species found were endangered. Of these Pachyneura fasciata, Keroplatus tipuloides, Xylophagus ater ja Xylophagus junki are considered vulnerable. As many as 82 of the species are new for Finland, seven of the species were new for Europe, and assumably there were several species new for science.
Total of 264 species of Hymenoptera were found. Dolichomitus aciculatus, Dolichomitus terebrans, Odontocolon punctulatus, O. spinipes ja O. dentipes are rare species. Aniseres caudatus is a species recently (1997) described for science in Russian Karelia.
Total of 170 species of polyporaceous fungi were found. The most species rich site was Tapionaho, which also had been studied most carefully. Total of 21 endangered species were found, and moreover, several species which have been recently described or are poorly known. Polyporus pseudobetulinus in considerd endangered, Clavaria zolingeri, Diplomitoporus crustulinus, D. lindbladii, Haploporusodorus, Hericum clathroides, H. fragile, Hydnellum suaveolens, Polyporus badius ja Sceletocutis lenis are vulnerable.
According to the studies Koitajoki area species diversity is high and especially Tapioanho area is very important from protection point of view.