Spergulo-Chrysanthemetum segeti ( Br .-Bl . et de Leeuw 1936 ) R . Tx . 1937 in the Drawsko Lakeland ( Western Pomerania )

Abstract The species richness and structure of Spergulo-Chrysanthemetum segeti have been assessed on the basis of 25 phytosociological relevés made by the Braun-Blanquet method in the Drawsko Lakeland (Poland). Two variants have been distinguished, Spergulo-Chrysanthemetum segeti chamomilletosum typicum and Spergulo-Chrysanthemetum segeti chamomilletosum with Plantago intermedia. The paper presents the distribution and analytical characteristics of this subatlantic association against the background of habitat conditions.


Introduction
The paper constitutes a continuation of a chorological study of the Spergulo-Chrysanthemetum segeti association in the area of the eastern part of Western Pomerania.In the first paper, the ecological and biotope characteristics of the Spergulo-Chrysanthemetum segeti association in the Słupsk Plain and the Damnica Upland were presented, in the second one -in the Słowińskie Coast, and in the subsequent one in the Bytów Lakeland and the Białogard Plain [1][2][3][4].
The Drawsko Lakeland is dominated by brown acidified and leached soils.The valleys of the rivers Parsęta, Rega, Stara Rega, Brzeźniczka, and Dębnica are covered with boggy soils.In the Drawa River Valley, south of Drawsko, alluvial soils are found.In the vicinity of Czaplinek and Rydzewo, black (D) and degraded meadow black earth (Dz) occurs [5].
In terms of agricultural land suitability, the soils of rye complexes (which cover 78% of the arable land in total) dominate the Drawsko Lakeland.Worth mentioning are the soils of wheat complexes (15% of arable land), which larger patches are found between Gudowo and Lubieszewo on Lake Lubie as well as between Karsino and Wełnica.Larger homogeneous areas of the good wheat complex (2) developed from particulate sediment material originating from marginal lakes.They occur on gentle clay slopes in the area of Dalewo, Darskowo, and Suliszewo.The defective wheat complex (3) is represented by soils formed from clays and particulate material sediments.The larger outlines of that complex cover the slopes of moraine mounds in Dziwogóra, Ogrodno and Ostropole.56% of the area of the rye complexes comprise very good (4) and good rye (5) complexes.A smaller area is covered by cereal-fodder complexes -(6%) strong ( 8) and (5%) weak ( 9) [6].
The Drawsko Lakeland belongs to the Baltic region and the mesoregion of the Drawsko -Bytów Lakeland.Soils developed on clays and sands on clays predominate.Forestation in this lake district is relatively low and amounts to 24%.Beech wood forests occur most frequently and they usually develop on clay soils difficult to plough, situated on steep slopes of end moraines [7] in the areas difficult got cultivation.
According to the geobotanical division of Poland, the Drawsko Lakeland is situated in the Pomeranian Divide.A substantial part of this mesoregion is situated in the region of Central Pomeranian Lakelands, in the Świdwin District and the Drawsko Lakeland.A small southeastern part is situated in the Wałcz Province and the Drawa River Valley region [8].
Detailed research on crop-related species was not done.The data concerning the occurrence of some species associated with the Drawsko Lakeland are provided by German botanists [9][10][11].More information concerning the distribution of field weeds in this area is found in the studies of Młynkowiak [12] and Sobisz [13].
The aim of the study was to describe the ecological and phytosociological characteristics of Spergulo-Chrysanthemetum segeti in the Drawsko Lakeland, with particular attention to its diversity against biotope conditions.

Material and methods
A field study was conducted in 2012-2014; 52 phytosociological relevés were made by the Braun-Blanquet method widely used in Poland.In this paper, 25 relevés sampled in 18 places are analyzed.The soil classification is based on Mocek [14].The phytosociological table contains information on soil complex, type of soil and its texture.The soil conditions in crop fields were established on the basis of the soil-agricultural maps at a scale of 1:5000 made available by the Marshall's Office in Szczecin.The soil samples were taken from every stand of Chrysanthemum segetum.The pH in H 2 O and 1 M KCl was determined by the potentiometric method [15].In the phytosociological table, the degree of constancy (S) was also taken into consideration, while the cover coefficient (D) was calculated according to Pawłowski [16].
The classification and terminology of syntaxons is in accordance with Ratyńska et al. [20].The nomenclature of weed species is given according to Mirek et al. [21], whereas crop plant nomenclature follows Jasińska and Kotecki [22].

Results
Phytocenoses of Spergulo-Chrysanthemetum segeti were found in spring crops (barley, oats, wheat and their mixtures, buckwheat) and root plant crops (potatoes, rutabaga, and fodder beet).In total, 101 species were found in the entire data set.The relevés comprise from 11 to 42 species (30 on average).
Spergulo-Chrysanthemetum segeti chamomilletosum typicum lacks hygrophilous species and a substantial proportion of oligotrophic species and acidophilous species from the Aperetalia spicae-venti order is characteristic of this association.The most frequent ones are Apera spica-venti (constancy class V) and Vicia hirsuta, Centaurea cyanus (constancy class IV).In its patches, 11 to 32 species were noted (24 on average).Spergulo-Chrysanthemetum segeti chamomilletosum typicum covers the slopes of moraine hills of with a western and northwestern exposure.The variant with Plantago intermedia develops on excessively moist soils.It is characterized by a larger number of species (from 32 to 42, on average 36) and a substantial proportion of shallow rooted therophytes of the Isoëto durieui-Juncetea bufonii class (Plantago intermedia, Gnaphalium uliginosum, and Juncus bufonius) and other species associated with moist biotopes, among others Mentha arvensis, Sonchus arvensis, Stachys palustris, Polygonum    hydropiper, and Ranunculus repens.Similar moisture relationships in spring crops with the participation of Chrysanthemum segetum were observed in Rhineland-Westphalia by Hüppe [24].Within the variant with Plantago intermedia, a subvariant with Galeopsis speciosa was distinguished (Tab.2, rel.[1][2][3][4][5][6][7][8][9][10][11].Galeopsis speciosa has a narrow spectrum of ecological requirements and occurs exclusively in soils which are periodically excessively moist in the complex 8 and 9 [25].
The local form of this association is distinguished by the presence of hempnettles, a species of low thermal requirement [26].They are accompanied by Anchusa arvensis and Lapsana communis.Regional forms of the association with the participation of Galeopsis sp.div.from the plateau areas of northern Poland were described, among others, by Sobisz [27].

Discussion
Chrysanthemum segetum is a Mediterranean species with subatlantic features [28].It is fairly common in England, the Netherlands, and in the German and French lowlands.The corn marigold is somewhere rare in Central Europe, North Africa and on the Caspian Sea coasts.Its northern range reaches Ireland, Scotland, Sweden as well as southern Norway and Finland.Individuals of Ch. segetum have been recorded in the northern part of the Iberian Peninsula, in the Balkans, in southern Ukraine and also in single localities in western Syria [29].
The first information about the occurrence of Ch. segetum within the present boundaries for Poland was reported by Lucas in 1860, who recorded it in Przytor and Warnowo on Wolin Island.In Poland 352 localities of Ch. segetum (210 ATPOL grids) have been identified until now.Most localities are concentrated in the north, west and northwest of the country.It is found in segetal (325 sites) and ruderal habitats (27 sites).The northernmost locality for this plant is Karwia, whereas the southernmost one is Zakopane [18].In the present study, 25 new stands of the species have been identified.
Spergulo-Chrysanthemetum segeti is a rare syntaxon in Poland and can be found in the western and northwestern part of Poland [46].Chrysanthemum segetum is a species characteristic for the association [47].It is especially found in the stands of crop plants, rarely in ruderal stands [48][49][50].The center of the range of this subatlantic syntaxon is in Western Europe [51][52][53][54][55].The association of Spergulo-Chrysanthemetum segeti reaches in Poland its eastern range, occurring especially on the South Baltic coast and in the part the Eastern Baltic Lakelands [56].
dominance of fertile beech wood, the "Pomeranian type" Melico uniflorae-Fagetum sylvaticae, and subatlantic lowland oak and hornbeam wood Stellario holosteae-Carpinetum betuli.Spergulo-Chrysanthemetum segeti occurs in the northern part of Poland in a series of moraine belts along the lake district located in a relatively cool and moist climate.Both in Western Europe and in the northwestern part of Poland, due to the participation of weeds of low trophic requirements, it has been so far included in the alliance of Panico-Setarion [58].At present, it seems that the higher participation of taxa from the alliance of Veronico-Euphorbion (= Eu-Polygono-Chenopodion) allows us to classify it in the latter.

Conclusions
■ Spergulo-Chrysanthemetum segeti, the association reaching in Poland the eastern limit of its range, was studied in the Drawsko Lakeland mesoregion.Spergulo-Chrysanthemetum segeti was only found in spring cereals (wheat, barley, oat and their mixtures, buckwheat) and in root crops (beets, rutabaga, potatoes).■ The association Spergulo-Chrysanthemetum segeti has a clear regional character because of the presence of Galeopsis sp.div., species that have low thermal requirements.■ Two variants were distinguished: Spergulo-Chrysanthemetum segeti chamomilletosum typicum (Tab. 1, rel.1-12) and Spergulo-Chrysanthemetum segeti chamomilletosum with Plantago intermedia (Tab.2, rel.1-13).The patches of the subassociation occur on leached brown soils, developed from loamy sands and clays (variant typicum), or they develop on brown soils, podzolic soils and black soils containing light loam (the variant with Plantago intermedia).The soil optimum for Spergulo-Chrysanthemetum segeti chamomilletosum typicum is the good wheat complex (2) and very good rye complex (4), while for the variant with Plantago intermedia the cereal-fodder complex -strong (8) and weak (9).■ The ecological optimum of Chrysanthemum segetum has shifted towards rich habitats (the dynamic circle of subatlantic lowland oak-hornbeam wood and fertile beech wood of "Pomeranian type"), hence the placement of Spergulo-Chrysanthementum segeti in Veronico-Euphorbion alliance is justified.