SOIL MITES (ACARI) OF THE ECOTONE BETWEEN THE SCOTS PINE FOREST AND MEADOW IN THE FOREST
LANDSCAPE IN TUCHOLA FOREST, POLAND S. Seniczak
1, A. Klimek
1and S. Kaczmarek
21Department 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
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
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
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
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 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.
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
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.
In the forest, the species number of Oribatida was distinctly higher than in adjacent meadow (Table 3). However, the highest number of species was noted in the marginal part of the forest and in plot situated between the forest and meadow, what is typical for the ecotone (Odum, 1982). In the part of the meadow covered with shrubs, the species number of oribatid mites was higher than in the central part of the meadow, and small increase of species number of Oribatida was observed in the part of the meadow near the shrub zone. No ecotone effect was observed in the Gamasida, whose species diversity was similar in all investigated plots (Table 4).
The dominance structure of Oribatida and Gamasida
Among the Oribatida, Tectocepheus velatus or Scheloribates latipes predomi- nated in the forest and in the boundary zone between the forest and meadow (Table 5).
In the meadow, Tectocepheus velatus or Chamobates cuspidatus predominated, but the proportions between the density of species were here lower than in the forest.
Among the Gamasida, Zercon triangularis predominated in the forest and in marginal part of adjoining meadow, while in the central part of meadow, Paragamasus runciger or Dendrolaelaps rectus was the most abundant.
The ecology of some oribatid and gamasid mites in the investigated ecotone
The species distribution of mites in the investigated ecotone well illustrates the ecology of some species. Among Oribatida, most species (Adoristes ovatus, Chamo- bates cuspidatus, Eupelops torulosus, Hemileius initialis, Oppiella nova, Oribatula tibialis and Quadroppia quadricarinata) preferred the forest (Tables 3 and 5). Several species (Metabelba pulverulenta, Oppiella minus and O. ornata) were abundant in the
Table 2. The soil pH, density of mites (A in thousand/1m2), species number (S) and Shannon index (H) of Oribatida and Gamasida in the ecotone between the
Scots pine forest and meadow in Tuchola forest Characteristics Plots:
1.0 2 3 4 5 6 7 8 9 10 11
pH 3.6 3.6 3.6 3.7 3.8 4.0 4.0 4.0 4.0 6.5 6.7
A of: Acari 162.1 104.4 111.6 119.2 134.7 75.9 29.7 27.5 42.6 30.6 17.3 ± 105.8 75.9 93.9 102.9 136.5 57.1 33.9 33.5 55.3 27.9 21.3 Oribatida 127.4 80.4 90.8 93.8 108.3 58.1 18.1 16.0 24.9 11.1 8.8 ± 93.3 59.2 81.4 86.3 113.3 50.1 20.9 20.4 32.3 13.7 10.9 Gamasida 12.6 11.5 11.1 12.2 11.8 6.8 2.1 1.8 3.3 3.8 3.7
± 9.1 9.5 11.7 13.8 11.4 6.5 3.1 2.1 5.1 4.5 3.4
S of: Oribatida 55 50 53 56 59 59 46 34 39 19 11
Gamasida 22 28 22 23 21 21 16 13 21 23 20
H of: Oribatida 2.70 2.60 2.72 2.78 2.95 3.12 2.93 2.81 2.73 1.60 1.48 Gamasida 2.27 2.27 2.33 2.32 2.09 2.01 2.26 2.25 2.64 2.70 2.50
Table 3. List of species of Oribatida in the ecotone between the Scots pine forest and meadow in Tuchola forest
Name of species Plots:
1 2 3 4 5 6 7 8 9 10 11
Adoristes ovatus (C. L. Koch) ? ? ? ? ? ? + + + +
Atropacarus striculus (C. L. Koch) + + +
Autogneta longilamellata Michael + +
A. willmanni (Dyrdowska) + +
Brachychthonius spp. + + + + ? + ? ? + ? +
Caleremaeus monilipes (Michael) + + + + + +
Camisia biurus (C. L. Koch) + +
C. spinifer (C. L. Koch) + + + + + + + +
Carabodes coriaceus C. L. Koch + + + + + + +
C. femoralis (Nicolet) + + + + + + + +
C. forsslundi Sellnick + + + + +
C. labyrinthicus (Michael) + + + + +
C. minusculus Berlese + +
C. subarcticus Trägĺrdh + + + + + + + + +
Cepheus cepheiformis (Nicolet) + + + + + + + +
forest, but the highest density they achieved in the boundary zone between the forest and meadow. Only two species (Eupelops occultus and Scheloribates laevigatus) preferred the meadow, while the eurytopic species, Tectocepheus velatus, had a high
Name of species Plots:
1 2 3 4 5 6 7 8 9 10 11
C. latus C. L. Koch +
Ceratoppia bipilis (Hermann) + + + + +
Ceratozetes 1 + + +
Ceratozetes sellnicki (Rajski) +
Chamobates cuspidatus (Michael) ? ? ? ? ? ? ? ? ? +
Ch. schuetzi (Oudemans) + + + + +
Conchogneta delacarlica (Forsslund) + + + +
Cultroribula bicultrata Berlese + +
Cymbaeremaeus cymba (Nicolet) +
Damaeus 1 + ? + + + + + + +
Damaeus 2 + + + +
Damaeus 3 + + + + + +
Diapterobates humeralis (Hermann) + + + + + + + +
Dometorina plantivaga (Berlese) +
Eporibatula rauschenensis (Sellnick) +
Eremaeus oblongus C. L. Koch + + + + +
Eupelops occultus (C. L. Koch) + + + ? + ?
E. torulosus (C. L. Koch) + + + + + + + +
Euphthiracarus reticulatus (Berlese) + + + + +
Euzetes globulus (Nicolet) + + + + + +
Galumna 1 + +
Galumna lanceata Oudemans + + + + ? ? + + +
Hafenrefferia glivipes (C. L. Koch) + + + + + + Hemileius initialis (Berlese) ? ? ? ? ? ? ? ? + + Heminothrus peltifer (C. L. Koch) + ? ? + + + + + ? ? ?
Hypochthoniella minutisima (Berlese) + + + + + +
Hypochthonius rufulus C. L. Koch ? + + ? + + +
Liacarus coracinus (C. L. Koch) + + + + + + + + +
Licneremaeus licnophorus (Michael) + + + +
Liebstadia 1 + +
Liebstadia similis (Michael) + +
Liochthonius sp. + + + + ? + + + +
Malaconothrus monodactylus Michael ?
Melanozetes mollicomus (C. L. Koch) +
Metabelba pulverulenta C. L. Koch ? ? ? ? ? ? ? ? ? +
Micreremus brevipes (Michael) + + +
Microtritia minima (Berlese) + + + + + + + +
Minunthozetes pseudofusiger(Schweizer) + +
Multioppia glabra Mihelčič ? + + + + + + +
Nanhermannia coronata Berlese + + + + +
N. nanus (Nicolet) ? + + ? + + + + + +
Nothrus palustris C. L. Koch + + + + +
N. silvestris Nicolet ? + ? + + + +
Oppiella 1 ? + + + ? + + +
Name of species Plots:
1 2 3 4 5 6 7 8 9 10 11
Oppiella bicarinata Paoli + +
O. minus (Paoli) ? ? ? ? ? ? ? ? ? +
O. neerlandica (Oudemans) + + + +
O. nova (Oudemans) ? + ? ? + ? + + ? +
O. ornata (Oudemans) + + + + ? +
O. subpectinata (Oudemans) + + +
O. unicarinata Paoli + + + + ? +
Oribatella berlesei Michael + ? ? +
Oribatula tibialis (Nicolet) ? ? ? ? ? ? + + + + Parachipteria willmanni Hammen ? ? ? ? ? ? + + ? + + Pergalumna nervosa (Berlese) + + + + + + + + +
Phthiracarus borealis Trägĺrdh + + + + + + +
P. lentulus (C. L. Koch) + + +
Protoribates 1 + +
Quadroppia quadricarinata (Michael) ? ? ? ? ? ? + + +
Rhysotritia duplicata (Grandjean) + + + + + + + Scheloribates laevigatus (C. L. Koch) + + + + ? ? +
S. latipes (C. L. Koch) ? ? ? ? ? ? ? + +
Steganacarus magnus (Nicolet) + +
Suctobelba spp. ? ? ? ? ? ? ? + + +
Tectocepheus velatus (Michael) ? ? ? ? ? ? ? ? ? ? ?
Trhypochthonius tectorum (Berlese) +
Trichoribates novus (Sellnick) + +
Trimalaconothrus novus (Sellnick) +
Tropacarus carinatus (C. L. Koch) ? + ? ? ? + + +
Number of species 55 50 53 56 59 59 46 34 39 19 11
Explanation: abundance (A) in thou./m2: ? - A >10.0. ? - 5.0 < A Ł 10.0. ? -1.0 < A Ł 5.0. + - A Ł 1.0
Amblyseius obtusus (C.L.Koch) + + + + +
Anthoseius verrucosus Waistein + +
Arctoseius cetratus (Sellnick) + + + + + +
A. magnanalis Evans + + + + +
Asca aphidioides (L.) + + + +
A. nova Willmann +
Cheiroseius borealis (Berlese) + +
Cheiroseius neocorniger (Oudemans) + +
Dendrolaelaps foveolatus (Leitner) + +
D. latior (Leitner) +
D. rectus Karg + ? +
Eviphis ostrinus (C.L.Koch) + ? ? ? + + +
Gamasellodes bicolor (Berlese) + + + + + + +
Gamasellus montanus (Willmann) + + + +
Gamasolaelaps excisus (C.L.Koch) + +
Holoparasitus excipuliger (Berlese) + + + + + + + + + Hypoaspis aculeifer (Canestrini) + + + + + + + + + +
H. austriaca (Sellnick) + + + +
H. praesternalis Willmann + + + + + + + + +
H. vacua (Michael) + + + +
Iphidozercon gibbus Berlese + + +
Lasioseius sp. + +
Macrocheles glaber (Muller) + +
Pachylaelaps furcifer Oudemans +
Paragamasus misellus (Berlese) + + + + + +
P. robustus (Oudemans) + + + + +
P. runciger (Berlese) ? ? ? ? + + + + ? + ?
Paragamasus sp. + + + + +
Parasitus hyalinus (Willmann) +
Parazercon radiatus Trägĺrdh + + + + + + + + + Pergamasus mediocris Berlese ? ? ? ? ? + + + + + +
P. septentrionalis (Oudemans) + + + + + + +
Prozercon kochi Sellnick ? ? ? + + + + +
Rhodacarellus silesiacus Willmann + + + + + +
Rhodacarus coronatus Berlese + + + + + + + +
Sejus togatus C. L. Koch + +
Trachytes aegrota (C.L.Koch) ? ? ? ? + + + +
Urodiaspis tecta (Kramer) + + + ? + ? + + + +
Uropoda minima Kramer + + + + + +
U. orbicularis (Muller) +
Veigaia cerva (Kramer) + + + +
V. kochi (Trägĺrdh) + + + +
V. nemorensis (C.L.Koch) ? + ? ? ? ? + + + + +
Vulgarogamasus kraepelini (Berlese) + + + + ? + + + + +
Number of species 22 28 22 23 21 21 16 13 21 23 20
Explanation: abundance (A) in thou./m2: ? - A >2.0. ? - 1.0 < A Ł 2.0. ? -0.5 < A Ł 1.0. + - A Ł 0.5
Table 4. List of species of Gamasida in the ecotone between the Scots pine forest and meadow in Tuchola forest
Name of species Plots:
1 2 3 4 5 6 7 8 9 10 11
Table 5. The abundance (A in thousand/1 m2) and dominance (D) indices of some Oribatida and Gamasida in the ecotone between the Scots pine forest and
meadow in Tuchola forest
A. ovatus A 6.16 6.33 4.32 4.60 6.36 1.86 0.15 0.18 0.05 0.03 - D 4.83 7.88 4.76 4.90 5.87 3.20 0.83 1.10 0.20 0.23 - C. cuspidatus A 6.53 7.06 8.27 7.01 5.88 4.25 1.94 1.58 1.41 0.05 - D 5.13 8.79 9.11 7.48 5.43 7.31 10.69 9.87 5.66 0.45 - E. occultus A 0.03 - - - - - 0.10 0.20 2.31 0.35 3.14
D 0.02 - - - - - 0.56 1.25 9.30 3.16 35.92
E. torulosus A 0.65 0.63 0.50 0.55 0.53 0.48 0.08 0.05 - - - D 0.51 0.78 0.55 0.59 0.49 0.82 0.42 0.31 - - - H. initials A 11.86 11.94 10.63 10.68 14.90 8.57 1.63 1.08 0.48 0.08 - D 9.31 14.86 11.71 11.39 13.76 14.74 9.03 6.74 1.92 0.68 - M. pulverulenta A 2.44 2.34 2.26 2.31 3.42 3.37 1.11 1.01 1.94 0.05 - D 1.91 2.91 2.49 2.47 3.16 5.79 6.11 6.27 7.79 0.45 - O. minus A 1.23 2.54 2.71 2.89 7.44 3.27 1.58 1.31 3.09 0.13 - D 0.97 3.16 2.99 3.08 6.87 5.62 8.75 8.15 12.44 1.13 - O. nova A 6.56 0.35 1.13 1.11 0.88 1.08 0.55 0.35 1.38 0.05 - D 5.15 0.44 1.25 1.18 0.81 1.86 3.06 2.19 5.56 0.45 -
O. ornata A - 0.13 0.20 0.20 0.70 2.09 0.03 - - - -
D - 0.16 0.22 0.21 0.65 3.59 0.14 - - - -
O. tibialis A 3.54 1.71 1.73 2.36 4.00 3.14 0.70 0.20 0.05 - 0.05 D 2.78 2.13 1.91 2.52 3.69 5.40 3.89 1.25 0.20 - 0.57 P. willmanni A 2.34 1.08 1.58 2.49 2.64 1.08 0.28 0.68 1.61 0.03 0.03 D 1.83 1.35 1.74 2.65 2.44 1.86 1.53 4.23 6.47 0.23 0.29 Q. quadricarinata A 7.74 1.01 3.54 2.16 3.62 1.33 0.25 0.48 0.35 - - D 6.08 1.25 3.90 2.30 3.34 2.29 1.39 2.98 1.42 - - S. laevigatus A 0.28 - - 0.08 0.35 0.60 1.73 1.21 1.89 0.35 - D 0.22 - - 0.08 0.32 1.04 9.58 7.52 7.58 3.16 - S. latipes A 14.43 17.54 16.91 10.91 10.33 6.08 1.08 0.96 0.35 - - D 11.32 21.83 18.63 11.63 9.54 10.46 5.97 5.96 1.42 - - T. velatus A 33.63 12.84 16.81 22.24 15.56 5.15 1.71 2.21 4.78 6.01 1.56 D 26.40 15.98 18.52 23.71 14.36 8.86 9.44 13.79 19.21 53.95 17.82 A. cetratus A 0.03 0.03 0.03 - - - 0.03 - - 0.45 0.43
D 0.20 0.22 0.23 - - - 1.22 - - 11.84 11.41
D. rectus A - - - - - - - - 0.03 0.78 0.35
D - - - - - - - - 0.76 20.39 9.40
E. ostrinus A 0.50 1.16 0.78 0.98 0.48 0.18 - - 0.05 - - D 3.98 10.04 7.00 8.02 4.05 2.60 - - 1.52 - - H. aculeifer A 0.13 0.20 0.20 0.13 0.15 0.10 0.18 0.25 0.40 0.28 - D 0.99 1.75 1.81 1.03 1.28 1.49 8.54 13.89 12.12 7.24 - P. runciger A 2.39 0.68 0.83 0.73 0.50 0.25 0.05 0.18 0.73 0.43 1.08 D 18.89 5.90 7.45 5.97 4.26 3.72 2.44 9.72 21.97 11.18 28.86 Name of species Plots:
1 2 3 4 5 6 7 8 9 10 11
Name of species Plots:
1 2 3 4 5 6 7 8 9 10 11
P. mediocris A 1.03 0.68 0.75 0.75 0.80 0.08 0.03 0.05 0.03 0.03 0.08 D 8.15 5.90 6.77 6.17 6.82 1.12 1.22 2.78 0.76 0.66 2.01 P. kochi A 1.28 0.58 0.58 0.43 0.30 0.05 0.13 0.10 - - - D 10.14 5.02 5.19 3.50 2.56 0.74 6.10 5.56 - - - T. aegrota A 1.01 1.33 1.46 1.68 0.43 0.30 0.05 - 0.10 - - D 7.95 11.57 13.09 13.79 3.62 4.46 2.44 - 3.03 - - V. nemorensis A 0.83 0.45 0.70 0.98 1.56 0.65 0.20 0.10 0.38 0.05 0.08 D 6.56 3.93 6.32 8.02 13.22 9.67 9.76 5.56 11.36 1.32 2.01 Z. triangularis A 3.80 4.47 3.82 4.10 5.28 3.27 0.78 0.60 0.20 0.23 - D 30.02 38.86 34.31 33.54 44.78 48.33 37.80 33.33 6.06 5.92 -
dominance index both in the forest and meadow.
Among Gamasida, there were also forest species (Eviphis ostrinus, Pergamasus mediocris, Prozercon kochi, Trachytes aegrota, Veigaia nemorensis and Zercon triangularis), and some of them achieved the highest density in the marginal part of the forest (Tables 4 and 5). Two species ( Paragamasus runciger and Prozercon kochi ) achieved their maximum abundance in the forest, while to others (Arctoseius cetratus and Dendrolaelaps rectus) preferred the meadow.
Discussion
The beneficial role of ecotones in the landscape is many sided, and therefore they play a great importance in the landscape ecology. They join different ecosystems and create specific habitats, being inhabited by a relatively large number of species (Odum, 1982), which migrate here from adjoining ecosystems. This way the ecotones increase the species diversity and stability of the landscape. They also equalise climate con- ditions and improve distinctly the visual and aesthetic values of the landscape, what is especially profitable in large agricultural and forest monocultures.
The effect of the ecotone on the distribution of organisms depends greatly on their body size. Large animals or plants create usually a broad ecotone, while small organisms and microorganisms create a narrow one. In the ecotone, very important is the ability of species to migrate. Slow moving animals like soil saprophagous mites, are strongly connected with plants by trophic dependencies. It was well observed in this research, where the oribatid mites achieved relatively high density in Scots pine forest, where rather thick layer of litter was present, and were distinctly less abundant in enjoining meadow. In the part of the meadow with shrubs the density and species number of these mites were also higher than in the central part of the meadow.
In this investigation, the effect of the ecotone on plants was well observed in the marginal part of Scots pine forest and in the boundary zone between the forest and meadow. More sunlight reached the forest floor there, what increases the covering of
shrubs and herbs, comparing to the central part of Scots pine forest. Similar increase of density of shrubs was observed in the marginal part of the shelterbelt in the agricultural landscape (Seniczak et al., 1998). Shrubs were also present in small density in the boundary zone between the forest and meadow and in the part of meadow adjoining to the forest. In the later part, the highest number of plant species was noted.
Based on the oribatid mites distribution in the investigated ecotone, their migration between plots seemed to be rather low, what is consistent with Miko et al.
(1989, 1992), Miko (1993) and Seniczak et al. (1998). It was evident in the boundary zone between the forest and meadow and in the part of the meadow which adjoined to shrubs, where the number of oribatid species was relatively high and distinctly decreased towards the central part of the meadow. Considering the distribution of oribatid mites in the ecotone we should realise that meter to oribatid mite individual seems to be rather a long distance. Basing on the body dimension, it is similar like about 200 m for an earthworm. For this reason the distribution of mite species in the investigated ecotone seems to be very useful for the study on their ecology.
The reaction of oribatid mite species to the ecotone was very clear. Most species was found in the marginal part of the forest and in the boundary zone between the forest and meadow, where the covering of shrubs and herbs was the highest and rather thick layer of litter was present. The shrubs also increased the species number of oribatid mites in the meadow, comparing to its central part, and a small increase of species number of Oribatida was observed in the part of the meadow near the shrubs.
No distinct reaction of predatory Gamasida to the ecotone was observed. These mites probably had much food both in Scots pine forest and meadow. In the forest, they could eat soft saprophagous mites, which were abundant here, while in the meadows they could eat nematodes (Karg, 1971), which are usually abundant there (Sohlenius and Wasilewska, 1984). Moreover, these mites move more quickly than the Oribatida, what equalised their density between plots. Probably for these reasons the species number of Gamasida was similar in all investigated plots.
Conclusions
1. The density of soil mites was greatly influenced by the plant associations; in Scots pine forest it was distinctly higher than in the meadow.
2. In mite associations the saprophagous Oribatida predominated. In Scots pine forest the species diversity of these mites was distinctly higher than in the meadow, but most species were found in the marginal part of the forest and in the boundary zone between the forest and meadow, what is typical for the ecotone.
3. No ecotone effect was observed in the predatory Gamasida, whose species number was similar in all investigated plots.
4. Some 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.
5. The oribatid mites seem to be better bioindicators of soil habitat in the ecotone than the gamasid mites.
Acknowledgements
We thank Dr. B. Dąbrowska, Department of Botany and Ecology, University of Technology and Agriculture, Bydgoszcz, Poland, for the determination of plant associations.
References
Karg, W. (1971): Acari (Acarina), Milben Unterordnung Actinochaeta (Para- sitiformes), die freilebenden Gamasina (Gamasides), Raubmilben. In: Die Tierwelt Deutschland, 58 T.VEB, F. Verlag, Jena, 475.
Miko, L. (1993): Effects of poplar windbreaks on soil arthropod communities in heavy soil agroecosystems of East Slovakia. Ecológia (Bratislava), 12: 163-178.
Miko, L., Tešliarova, Z., Grejtowský, A, (1989): The influence of poplar windbreaks on selected biological characteristics of heavy soils in the East Slovakien lowlands.
Ecológia (CSFR), 8: 275-285.
Miko, L., Takácová, M., Miko, M. (1992): Effects of poplar windbreaks on soil arthropod communities in heavy soil agroecosystems of East Slovakia. Ecológia (CSFR), 11: 315-323.
Odum, E. P. (1982): Podstawy ekologii. PWN, Warsaw, p. 661.
Seniczak, S., Kaczmarek, S., Seniczak, A. (1998): Soil mites (Acari) of ecotones between shelterbelt and cultivated fields in the agricultural landscape near Turew, Poland. Bull. Pol. Acad. Sci.. (Warsaw), 46: 7-12.
Sohlenius, B., Wasilewska, L. (1984): Influence of irrigation and fertilization on the nematode community in a Swedish pine forest soil. J. Appl. Ecol., 21: 327-342.
