WEED COMMUNITIES IN POTATO ( Solanum tuberosum L . ) CROPS OF THE MAZOWIECKI LANDSCAPE PARK

This paper presents a description of segetal communities in potato crops cultivated in the Masovian Landscape Park. The communities were analysed based on 64 phytosociological releves made at 45 localities. 4 associations were found in the study area, that is, Digitarietum ischaemi, Echinochloo-Setarietum, Galinsogo-Setarietum, and Lamio-Veronicetum politae . Phytocenoses representing the associations Digitarietum ischaemi and Echinochloo-Setarietum were most varied floristically. Lower syntaxonomical units were determined within these associations, that is, subassociations and variants. These phytocenoses were frequently found; they occurred in various habitats characterized by different trophic and moisture conditions. Patches of the association Lamio-Veronicetum polita were rare and they occurred only on fertile soils and on small areas.


IINTRODUCTION
The area under potato has fallen considerably over the last decade from 1250.4 (in 2000) to 388.3 th (in 2010) (GUS, 2011). This has resulted from changes in the cropping structure, increased fallow area, an unfavourable economic situation, and in the case of land in the vicinity of urban areas, the allocation of land for building development. As far as the Masovian Landscape Park is concerned, there is an additional element, that is, the land use structure: 70% of the area is covered by forest, whereas 11.3% is ploughed land. All the aforementioned factors have influenced potato cultivation in the Masovian Landscape Park causing its continuous decline. The areas cropped to potato are small and yields harvested are mainly used to meet the needs of households.
This paper presents the next study on phytocenoses established in crop plants in this area (Skrajna et al. 2009;Skrajna and Ł ugowska, 2010). The objective of the study was to analyse communities in potato crops against the background of various habitats under conditions of extensive farming in the Masovian Landscape Park area.

RESULTS
Ten different types of phytocenoses, represented by subassociations and variants of 4 associations, were recognised in the Masovian Landscape Park.
Systematics of distinguished root crops com-  Tx. Et Prsg (1942) 1950 The association, of Sub-Atlantic character, occurred both in the Park and its buffer zone.
It was described on the basis of 17 phytosociological relevés. Altogether, there were recorded 71 species in all the examined patches of land (Table 1). Due to the great floristic diversity within this association, apart from the typical form, there was found a form characterised by the presence of ruderal and wet species. The appearance of the community was dominated by the typical species Digitaria ischaemum, with its percentage exceeding 60% in some patches.
Typical patches of this community developed on dry and poor soils. 42 taxa were found that were the poorest phytocenoses in the potato fields. The nature of the analysed phytocenoses was influenced by the group of acidophilous species representing the association Panico-Setarion and which included Rumex acetosella, Spergula arvensis, Scleranthus annuus, Setaria pumila and Raphanus raphanistrum.
Patches of this variant including ruderal species formed in small areas cropped to potato located adjacent to fallow land. This variant was distinguished because the community was characterised by a considerable share of ruderal species compared with other agrophytocenoses. Frequent components of the flora of this community were as follows: Artemisia vulgaris, Erigeron acer, Lactuca serriola, Tanacetum vulgare, Malva neglecta, Sisymbrium officinale.
On light loamy sands, representing different soil types belonging to the cereal-fodder poor soil quality complex, phytocenoses formed that included moisture-loving species. The variant with these species was distinguished based on 5 plant patches. They were slightly richer phytocenoses than the previous ones as 44 weed species were found. The nature of this community was defined, apart from the typical species, by moisture-loving species with shallow roots, the most numerous and most frequent species being Spergularia rubra, Gnaphalium uliginosum, Juncus bufonius, Sagina procumbens, and Plantago intermedia. Krusem. et Vlieg. (1939) 1940 The association Echinochloo-Setarietum was characterised on the basis of 26 phytosociological relevés which comprised 114 weed species (Table 2). These phytocenoses were most frequently found in the examined fields. The diversity of habitats where the phytocenoses of this association developed influenced the heterogeneity of individual patches. Within the association, 2 subassociations and 3 variants were found. The whole association was influenced by the mass presence of its typical species, Echinochloa crus-galli, which reached a very high cover index (D=2567). In turn, Raphanus raphanistrum was most frequently found in Echinochloo-Setarietum typicum, in the remaining communities being found in parts of the patches only. Moreover, the common species in the association were Setaria pumila, Matricaria maritima subsp. indora, Chenopodium album, Stellaria media, Viola arvensis, Polygonum aviculare, and Polygonum lapathifolium subsp. lapathifolium.

Echinochloo-Setarietum
Relevés 1 to 5 revealed communities of the most acidophilous character which were included in Echinochloo-Setarietum sperguletosum. Patches of this subassociation developed on different types of soils representing the good and poor rye soil quality complex. It was the floristically poorest community in the association Echinochloo-Setarietum. Only 39 weed species were found in it. The nature of the association was defined by 3 acidophilous species:

Spergula arvensis, Rumem acetosella, Scleranthus annuus.
Typical patches of the association were found on leached brown soils belonging to the very good and good rye soil quality complex. The community comprised 54 weed species. Apart from the species typical of this association, Matricaria maritima subsp. indora was a regular component of these phytocenoses, whereas Chenopopodium album was the most frequent component of the syntaxa of this association.
The association Echinochloo-Setarietum, with a high share of wet species, was found on light and strong loamy sands representing degraded chernozems and alluvial soils. These were the richest phytocenoses in this association, represented by 73 weed species. The following were the most frequent and numerous species: Plantago intermedia, Gnaphalium uliginosum, Mentha arvensis, Ranunculus repens, Polygonum hydropiper.
Some patches of the association Echinochloo--Setarietum were characterised by a substantial share of Amaranthus retroflexus, which made it possible to classify these phytocenoses as a variant including this species. The community developed on various soils and was floristically abundant, as 70 species were found in 5 relevés. Numerous Amaranthus retroflexus plants in the communities were accompanied by other species, such as Stellaria media, Polygonum lapathifolium subsp. lapathifolium, and Senecio vulgaris, which is indicative of high soil nitrogen content in these habitats. The analysed phytocenoses comprised a small number of wet species.
Communities representing Echinochloo-Setarietum with Veronica agrestis established on trophically rich and well-moistened fertile soils. The phytocenoses were characterised by a high share of species of the alliance Polygono-Chenopodion, of which Veronica persica, Lamium purpureum and Euphorbia helioscopia were regular components.

Galinsogo-Setarietum
Patches of the association Galinsogo-Setarietum developed on leached brown soils which were well fertilised and in good tilth. These phytocenoses were most frequent in the Park's buffer zone, mainly in the proximity of buildings. The association was described based on 10 phytosociological relevés which were floristically rich communities. There were found 76 species in all the examined patches, the average number of species per relevé being 25 (Table 3). The regular components of the phytocenoses were species typical of the association, of which Galinsoga parviflora had a very high cover index. The analysed patches were characterised by a high share of the alliance Polygono-Chenopodion species, the most frequent being Lamium purpureum, Veronica persica, Euphorbia helioscopia and Matricaria maritima subsp. inodora. Moreover, the nature of the phytocenoses was also influenced by species belonging to higher syntaxonomic units which locally reached higher cover, that is, Chenopodium album, Stellaria media, Setaria pumila, Viola arvensis, and Anthemis arvensis. Kornaś 1950 Patches of the association developed on fertile CaCO 3 -rich soils of the good wheat soil quality complex. The association is found both in the Park and in its buffer zone. The phytocenoses were floristically rich as 82 weed species were recorded in 10 patches, the average number of species per relevé being 26 (Table 4). Of the typical species, Lamium amplexicaule was the most common component of this association, Veronica agrestis was less frequent, whereas Veronica opaca and Veronica polita occurred only in some plant patches. There was found a considerable group of the Polygono-Chenopodion alliance species, of which the most numerous species that reached the highest cover were: Veronica persica, Lamium purpureum, Chenopodium polyspermum, Euphorbia helioscopia and Oxalis fontana. In turn, common species of higher syntaxonomic units in the association included: Chenopodium album, Stellaria media, Anagallis arvensis, Chaenorchinum minus, Echinochloa crus-galli, Polygonum lapathifolium subsp. pallidum, and Aethusa cynapium.

DISCUSSION
Intensification of modern agriculture leads to impoverishment of agroecosystems. Many weed species disappear irreversibly, while others spread at a high rate and change the composition and structure of communities. Many authors focus on biodiversity preservation in agriculturally utilised areas and suggest various forms of species conservation, thereby conserving shrinking segetal communities (Ratyń ska and Boratyński 2000;Dostatny, 2004;Siciń ski and Sieradzki, 2010). Such a role might also be fulfilled by landscape parks where the traditional farming system is maintained.
Soils of the Masovian Landscape Park have varied trophic and moisture conditions. Small areas under potato adjacent to fields cropped to cereals, meadows or ruderal communities additionally influence the diversity of segetal communities. These factors have contributed considerably to the high diversity within and inside the associations. Although no intermediate or impoverished associations or alliances were found in the area of the Masovian Landscape Park, reports by other authors examining various areas in different parts of Poland, Wnuk (1976), Szotkowski (1981, Szmeja (1989), Anioł -Kwiatkowska (1990), Kozak (2002, Siciń ski (2003), W ę grzynek (2005), Skrajna and Skrzyczyń ska (2008), Rzymowska and Skrzyczyń ska (2007), have shown that the floristic distinctiveness of agrophytocenoses is diminishing. 4 associations were found in fields cropped to potato in the study area, that is, Digitarietum ischaemi, Echinochloo-Setarietum, Galinsogo-Setarietum and Lamio-Veronicetum politae, the first two associations being internally diverse. Due to its Sub-Atlantic character, Digitarietum ischaemum reaches the south--eastern boundary of its occurrence in Poland. According to many authors (Anioł - Kwiatkowska, 1990;Kozak, 2002;W ę grzynek, 2005), the association is disappearing from agrophytocenoses as the poorest habitats are excluded from cultivation, the production potential of these habitats increases, and they are allotted for construction or afforestation.
What is interesting is the presence of phytocenoses with ruderal species in parts of the patches, which can result from small cropped areas and the proximity of buildings and fallow land. It is also indicative of partial ruderalisation of these communities. The process of infiltration of ruderal species into segetal communities in Poland has been reported by Kapeluszny (2000), Misiewicz et al. (2000), K utyna et al. (2010), and T r ą b a (2010).
Well-developed patches of Lamio-Veronicetum politae with a full range of the association's diagnostic species established on fertile nutrient-rich soils. The analysed association found in some areas of Poland is usually mentioned in its impoverished form with a rare occurrence of Veronica sp. (Korczyń ski, 1998;Szmeja, 1989;Kozak, 2002;W ę grzynek, 2006). According to Wnuk (1987) and Anioł --Kwiatkowska (1990), Veronica polita, Veronica opaca and Veronica agrestis are the species that best characterise Lamio-Veronicetum politae.

CONCLUSIONS
1. Potato fields in the Masovian Landscape Park cover small areas and are more and more difficult to find. 2. Plant communities established in the investigated crops are diversified and floristically rich, which reflects substantial soil variability and extensive farming. 3. The type of farming in such areas is particularly important in preserving the segetal flora diversity of agricultural landscape.