Studying islands is a very interesting subject for ecology, systematic and biogeography. Researches like these can discover rare species that are in need of protection, and also allow to estimate the areals of certain species (Glazkova, 1999). Because of the small size of islands, a limited amount of ecotopes, the shut-in character of the territory, special climatic characteristics, high-tide low-tide regime, islands have special ecological conditions.
Especially representative in this situation are the islands of northern seas, and (in particular) of the White Sea. These islands are generally small and do not have a big list of vascular plant species, which removes a lot of complications in their study. And, it is well known that the White Sea islands experience rapid elevation, while the succession on these islands is, on the contrary, slow. The role of sea birds in the making of the islands flora is well studied (Breslina, 1979, 1987). These data allow forming adequate models of the becoming of the island flora.
Islands of the Kandalaksha bay of the White Sea draw much attention of botanists (Breslina, 1968; Bogdanva, Vehov, 1969; Vehov, Bogdanova, 1969; Vorobyova, 1996), though until now a lot of them weren't explored. (I.P.Breslina, oral information). This is also true for most of the islands of the Tchupa gulf and to the ones East and Northeast from its mouth in the Kiv gulf and east from Sidorov island. Some of these islands are relatively large (for instance Sidorov island is 6 square kilometers big), but some are pretty small, the so-called Baklishi, Kamni (rocks) and Ludki (Breslina, 1987), which are often no bigger then 10 square meteres.
The White Sea expedition of the Moscow Gymnasium on the South-East has been working in the Tchupa gulf region since 1991. Except for the gymnasium students and teachers, year after year, students and staff of Moscow State University take part in the expedition. The floristic studies of the gulf region were started in 1994, and since 1999, systematic floral studies take place.
The studied islands are geographically divided into several archipelagos (check a map): The Ivaninovskie islands are situated east and north-east-east from cape Ivanov Navolok. Ivankov is connected to the continent during low-tide. The archipelago contains 5 islands. Medvezhkinskie islands are situated east of Medvezhij peninsula. The archipelago contains seventeen islands. Odinokie Ludi are situated north-east-east from the Medvezhkinskie islands. Three islands. Srednie Ludi are situated between cape Cartesh and Sidorov island. Three islands including Ubileini island. Keretskie islands are a group of islands situated east from the mouth of the river Keret. We studied Sidorov island (and the small island west from it) and Maliy Andronin with the adjacent island. Sidorov islands are the islands situated east of Sidorov island. 9 islands. Ileika islands are situated west of Sidorov island. 6 islands. Islands of the Tchupa gulf. We studied two small islands thoroughly, situated near Tchkalovsky village, and west of Oleniy island, and also we studied Kruglash island, situated near the entrance to the gulf.
Also, thanks to the noble consent of the Kandalakshski reserve administration, we were able to visit the Kem-Ludsky archipelago and make a floristic study of the island Sredniy (Kem-Ludski). Therefore we studied 51 islands. Unfortunately, the names of many islands or even archipelagos are absent as well as on the maps, and in the memory of the local citizens. The staff of the White Sea Biostation of the RAS gave us a great deal of help in finding the correct geographical names, but still, in most situations we were forced to use fictional names, made up by the participants of our expedition.
All the studies were made in the later half of July and in the first third of August. During the study of the islands we used the transect method with a walk around part of the shore. First the study group walked across the islands estimated maximal length, walking in a chain, so as to spot more plants, and then back to the landing place. We noted all the met plant species, and, if needed, made herbaral gatherings (they are all prepared for donation into the MSU herbarium). The more interesting parts of the island (for instance swaps, ponds) were studied more thoroughly.
The used this abundance scale:
0 - There are no plants of this species
1 - The island has only one sample of the plant or only one tussock of this species.
2 - There are no more than 10 samples or tussocks of the species.
3 - The number of plants is not higher than 5% of the total island's vascular plant flora.
4 - The number of plants is not higher than 25% of the total island's vascular plant flora.
5 - The number of plants is not higher than 50% of the total island's vascular plant flora.
6 - The number of plants is not higher than 75% of the total island's vascular plant flora.
7 - The number of plants is not higher than 100% of the total island's vascular plant flora.
Several groups took place in the study. The species abundance was noted for every island based on the above said scale; distance to the mainland; the island's landscape; “openness”; the existence of certain ecotopes or anthropogenic remainders. The type of the island (by Breslina scale, 1987).
The staff of the MSU and the staff of Moscow botanical institute (RAS), were a great help in identifying certain plants. The plants of certain groups (for instance Hieracium, Puccinellia, Euphrasia) were not identified to the species. The full species list consists of 247 species and species groups. On the account of the lists of flora, we made local plant areal maps for all the discovered species. Please note that all the species we found on the islands were also found on the mainland.
As a result from analyzing the plant areals we divided them into 8 basic types(names are made-up):
Main-land (10%) - Plants with this areal type are found on islands which are close to large parts of main-land. We assume, that the plants of this group inhabit the islands in mainland to outer-sea direction. The inhabiting process of the edge representatives of this type of areal is limited by Sidorov island and the islands located near the mainland (for instance Ivnakov, Mendov islands). Coronaria flos-cuculi has this type of areal. Another type of distribution are represented by the plants found on almost all of the studied islands in the exception of the most Northern ones (Odinokie Ludi) and the most Eastern ones (Cherepacha, Vishka and Mu-Mu islands). Archangelica officinalis has this type of distribution. We must point out that the plants with a mainland areal are less abundant to the East of Sidorov island than the ones inside the Kiv gulf. We explain this not only by the peculiar inhabiting process, but also by the climate limiting factors.
Mainland-gulf (12%) - Plants with this areal type are found on al gulf islands we studied. The plants of this group have even a stronger affinity to the mainland than the ones of the first group.
Sidorovsky (20%) - The inhabiting process of this group is limited (except for the mainland) by Sidorov island and less often by the nearby islands (for instance Drosera anglica). We think that the species of this group distributed along the islands of Keretsky archipelago (or under the protection of its islands). The retaining of these species on Sidorov island is most likely connected with the diversity of biotopes of the island.
Central (2%) - These species are abundant on the central islands of Kiv gulf (for instance Srednie Ludi). Botrychium lunaria has this type of distribution.
Dispersed (3%) - The distribution of these species is limited by the presence or absence of appropriate places of habitat. For example cliff-moss cushions, and Carex brunnescens.
North-Western (3%) - Species of this group inhabit mostly North and north-western islands (for example, Gymnadenia conopsea). These species are not present as a rule on Ivaninovsky and most of the Medveshkinsky islands. It is possible that the inhabiting process of these species occurred from the Northern bank of the Kiv gulf of from the islands of the Kem-Ludsky archipelago.
Continuous (5%) - Species of this group are present on all or practically all of the studied islands with the exception of Kamni and Baklishi type islands. (Atriplex niducaulis)
Non-classified (45%) - In this group we put species with un-identified areals. Some of the species have very unusual distribution patterns, for example Ribes spicatum, the areal of which belongs mostly to Southern islands.
Therefore, about half of the studied species belong to the wide mainland areal group. It means that the inhabitation process of the Kiv gulf islands, most probably, occurred from the large nearby mainland. And (or) distribution of many species is limited by the open sea factors.