Soil Mites (Acari) of the Ecotone Between the Scots Pine Forest and Meadow in the Forest Landscape in Tuchola Forest, Poland
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249 SOIL MITES (ACARI)... SOIL MITES (ACARI) OF THE ECOTONE BETWEEN THE SCOTS PINE FOREST AND MEADOW IN THE FOREST LANDSCAPE IN TUCHOLA FOREST, POLAND S. Seniczak1, A. Klimek1 and S. Kaczmarek2 1Department of Ecology, University of Technology and Agriculture, 2Institute of Biology and Environmental Protection, Pedagogical University, By- dgoszcz, Poland Abstract The soil mites in the ecotone between the 26 years old Scots pine forest (plant association from the ordo Vaccinio-Piceetalia) and adjacent meadow (plant association from the ordo Arrhenatheretalia), in the forest landscape in Tuchola Forest, were investigated in spring and autumn of 1995 and 1996. Eleven plots were chosen in this ecotone. In the forest, plots were situated in distances of 1 m, 2 m, 4 m, 8 m and 20 m from the border of the forest, and in the meadow they were 1 m, 2 m, 4 m, 8 m and 20 m from the border of the meadow. One plot was situated between these ecosystems. The density of soil mites was greatly influenced by the plant associations; in Scots pine forest it was distinctly higher than in the meadow. In mite associations, the saprophagous Oribatida predominated. In Scots pine forest, the species diversity of these mites was distinctly higher than in the meadow. However, the most species was found in the marginal part of the forest and in the boundary zone between the forest and meadow, what is typical for the ecotone. No ecotone effect was observed in the predatory Gamasida, whose species number was similar in the investigated plots. Several mite species achieved their highest density in the boundary zone between the forest and meadow, but only one, Oppiella ornata, was earlier announced as a shelterbelt and ecotone species. Introduction In the landscape ecology much attention is paid to the biodiversity. It may be considered in different aspects and different levels of systematic organisation (Richling and Solon, 1996), but the most important of them for the stability of the lanscape seems to be the species diversity (H) in Odum (1982) meaning. In natural ecosystems, which are slightly changed by human activity, this diversity is usually high. There are many 250 S. SENICZAK predators and parasites in these ecosystems, which are able to regulate the development of the other species, including pests, in their early stage, even then, when they find very good developmental conditions. Therefore, no large populations of pests appear here and these ecosystems can develop without harm. In contrast, in large agricultural areas and those forested by a man, with large monocultures, the species diversity is rather low. There are too little predators and parasites in them, which could protect the plants against the pests. Pests find here much food, and when the climate developmental conditions are favourable, they multiply very quickly and damage the plants or kill them. In such a situation chemicals are used to protect the plants against the pests. However, the chemicals perturb the ecological balance in ecosystems, and kill beside the pests also the other species, including predators and parasites, what lowers the species diversity and stability of these ecosystems. If we want to avoid the chemicals, we should improve the stability of the landscape by increasing its diversity. The species diversity of ecosystems generally depends on soil fertility, but in the ecotone it is higher because of many species, which migrate from the adjoining ecosystems into the boundary zone. Therefore, if we enlarge the ecotones, we also increase the species diversity and stability of the landscape. In this research, the soil mites were investigated in the ecotone between the young Scots pine forest and adjoining meadow, with species analyse of saprophagous Oribatida and predatory Gamasida. Study Areas The ecotone was situated between the 26 years old Scots pine forest and adjacent meadow, in the central part of Tuchola Forests, Forest Inspectorate Osie and Forest District Łoboda (Fig. 1). These forests grow on one of the largest outwash areas, which were formed in the foreground of Pomeranian Glaciation. The ecotone was chosen on a slope with about 10% N orth inclination; its higher part was covered with Scots pine forest and its lower part was grown by grasses (Fig. 2, Photos 1-3). The climate of this region is moderate, being under the influence of an oceanic climate from the West, and a continental climate from the East. The growing season lasts for about 200 days, the mean annual rainfall is 560 mm, and the mean annual temperature is 7.40C. The wind blows mainly from the West and South-West, and is usually a breeze. The forest soil belongs to the spodic udipsamments soil group, and has a well developed litter, about 5 cm thick. The meadow soil is differentiated: its higher part, situated near the forest, belongs to psammaquepts soil group, while the other part belongs to medisaprists and sapristis soil group. The forest plant association is between Leucobryo-Pinetum and Peucedano- Pinetum, and belongs to the ordo Vaccinio-Piceetalia. In the tree layer Scots pine (Pinus sylvestris L.) predominates, with a small amount of spruce [Picea abies (L.) Kerstew.] and birch (Betula pendula Roth.). In the central part of the forest the covering of trees is the highest, and therefore the shrubs and herbs are weakly developed there 251 SOIL MITES (ACARI)... Fig. 1. The location of the investigated ecotone between the Scots pine forest and meadow in the Tuchola Forestv Fig. 2. The location of plots in the ecotone between the Scots pine forest and meadow 252 S. SENICZAK Photos 1-3. Views on the ecotone between the Scots pine forest and meadow in Tuchola forest: upper - general view, middle - the boundary zone between the forest and meadow, lower - the central part of the forestv 253 SOIL MITES (ACARI)... because of the lack of the sunlight. The shrubs include small spruce trees, mountain ash (Sorbus aucuparia L.), alder buckthorn (Frangula alnus Mill.), blackberry-bush (Rubus plicatus W. et N.) and juniper (Juniperus communis L.). Among herbs, reed grass [Calamagrostis arundinacea (L.) Roth.] and bent grass (Agrostis vulgaris With.) are frequent. The mosses are well developed and a mesophile species Pleurozium schreberii (Bridd.) Mitt. predominates in them. In the direction of the meadow, the covering of bushes and herbs increases, while the covering of mosses decreases, along with decreasing covering of trees (Table 1). In the marginal part of the forest, the bushes grow in a distinctly higher density and are richer in species than those in the central part of the forest. Alder buckthorn predominates there, and besides of species, which occupy the central part of the forest, poplar (Populus tremula L.), fieldelder (Sambucus nigra L.), alder [Alnus glutinosae (L.) Geartn.], English oak (Quercus robur L.), currant bush (Ribes sp.) and hornbeam (Carpinus betulus L.) are present. The bushes grow also in the boundary zone between the forest and meadow and in adjoining zone of the meadow. The meadow plant association belongs to the ordo Arrhenatheretalia. Meadow grasses (Poa pratensis L. and P. trivialis L.) and fescue (Festuca pratensis Huds.) are the most frequent there. Table 1. The covering of plant layers (%) and the number of plant species in the ecotone between the Scots pine forest and meadow in Tuchola forest Characteristic Plots: 1 2 3 4 5 6 7 8 9 10 11 Cover of trees layer 90 80 80 80 60 40 10 5 - - - Cover of shrub layer 5 5 1 55 60 20 10 10 - - - Cover of herb layer c 20 25 15 20 50 60 100 100 100 100 100 Cover of mosses layer 90 70 60 60 50 40 40 20 20 20 5 Number of plant species 24 26 20 25 27 26 37 35 30 20 21 Material and Methods The soil mites in the ecotone between the 26 years old Scots pine forest and adjoining meadow were investigated in spring and autumn of 1995 and 1996. Eleven plots were chosen in total. In the forest, plots were situated in distances of 1 m, 2 m, 4 m, 8 m and 20 m from the border of the forest, and in the meadow they were also 1 m, 2 m, 4 m, 8 m and 20 m from the border of the meadow. One plot was situated between these ecosystems (Fig. 2). In each plot and each sampling period, 10 soil samples each 17 cm2 in area and 10 cm deep were taken, and each was further divided into 2 vertical soil horizons. In the forest, organic (O) and mineral (AEes) soil horizons were distinguished, while in the meadow and in plot situated between these ecosystems the 254 S. SENICZAK soil was divided into mineral AM’ and AM” horizons. Mites were extracted from the material in high gradient Tullgren funnels. Over 34 000 mites were examined. We determined the Oribatida and Gamasida to species or genus, including juvenile stages. The species diversity of Oribatida was characterised with the Shannon H index (Odum, 1982). Results Density of mites and species diversity of Oribatida and Gamasida In Scots pine forest, the density of mites was distinctly higher than in adjoining meadow (Table 2), what was probably caused by the lower soil pH, and presence of organic layer in the forest. A relatively high density was noted in the boundary zone between these ecosystems and in the adjoining meadow covered by bushes, what indicated the great influence of plants on the density of soil mites. In the central part of the meadow, the density of mites was distinctly lower. This pattern of density was created mainly by the Oribatida, which predominated in mite associations both in the forest and in the meadow, and by the Gamasida, which were usually the second most abundant.