THE EFFECT OF FARMING METHOD ON THE DYNAMICS OF COMMUNITIES FROM THE ALLIANCE Radiolion linoidis (RIAS GODAY 1961) PIETACH 1965 IN KAŁUSZYN UPLAND AGROCENOSES

The work presents the results of studies carried out from 1994 to 2010 on changes in phytocenoses with Radiolion linoidis species due to increased intensification of the farming process. The research material consisted of 136 phytosociological relevés taken from the same sites located in cereals, tuber crops/maize and stubble fields. The relevés were grouped based on three periods reflecting changes in farming system: period I (1994–1997) – traditional farming system; period II (2002–2004) – shift from traditional to intensive farming; period III (2008–2010) – intensive farming system. Communities with Radiolion linoidis continued to disappear over the whole study period due to farming intensification. The phytocenoses Spergulario-Illecebretum verticillati found in stubble fields and communities with Illecebrum verticillatum observed in cereals and tuber crops in period I were replaced with patches of Echinochloo-Setarietum in maize and stubble fields as well as the association Vicietum tetraspermae in cereals in period III. The values of Sørensen’s index of community similarity and of the dynamics index emphasize how advanced the process of changes in and impoverishment of communities was.


INTRODUCTION
Intensive development of agricultural production technology in Europe began in the first part of the 20 th century [1] and in Poland in the second part of the 20 th century. Modern agrotechnology and intensive application of chemicals in field production have led to the disappearance of many specialised species and whole communities [2][3][4][5]. Other factors that have promoted the impoverishment of flora in agrocenoses include abandoning marginal land, reduced diversity of cultivated fields, for example smaller percentages of fields under Secale cereale L. and Linum usitatissimum L., and ploughing under of stubble fields which are the main place where many short-lived ground species develop [6,7]. They also include communities with Radiolion linoidis included in the list of endangered segetal communities in Poland [8].
The purpose of this work was to analyse transformations of communities from the alliance Radiolion linoidis due to changes in habitat conditions resulting from intensification of the farming process.

MATERIALS AND METHODS
Field observations were performed over the period 1994-2010 in the same sites located in cultivated fields of 23 localities of the Kałuszyn Upland [14] ( Fig. 1). There was a total of 136 phytosociological relevés taken using the Braun-Blanquet approach [15] in fields under cereals, root crops/maize and in stubble fields. Next, the relevés were grouped according to the following three periods to reflect changes in farming methods: -period I (1994-1997) -traditional farming system; -period II (2002)(2003)(2004)) -transformation periodshift form traditional to intensive farming; -and period III (2008-2010) -intensive farming system. Data on the changes in farming intensification and percentages of area under individual crops were derived from surveys carried out among the owners of the fields where permanent study areas were located. Soil conditions were determined using agricultural soil maps at a scale of 1:5000. Relevés from the study periods were arranged into tables according to individual crops and stubble. Then, phytosociological classification was made [16] and used to analyse the structural changes in the communities.
Sørensen's index of similarity (SW s ) was employed to reflect the extent of changes in communities in individual study periods. The index was calculated according to the following formula: Moreover, the dynamics index V was used to analyse changes in the floristic composition of agrophytocenoses in the sites studied. The index reflects an increase or decrease in constancy of occurrence and is a measure of species dynamics [17]: where: S 1 -constancy of occurrence of a given species in period I (1994-1997); S 3 -constancy of occurrence of a given species in period III (2008-2010). The species which were characterised by an absolute increase or decrease in constancy of 4 percent points were considered to be species whose constancy changed significantly. Vascular plant terminology in the study followed Mirek et al. [18].

RESULTS
Comparisons of the present state of the communities with their state 17 years ago revealed dynamic changes taking place in the structure of agrocenoses for all the crop groups and stubble fields. A number of community transformations associated with changes in the land use structure and farming intensification took place.

Changes in stubble communities
Changes in syntaxonomic affiliation of communities were observed in the study area in stubble fields. Two associations including lower units were recognised in period I: Spergulario-Illecebretum verticillati and Digitarietum ischaemi. They were floristically rich phytocenoses: there was a total of 113 species in stubble fields ( Table 1). Number of species per relevé ranged between 26 and 53, on average 32 species. There was observed a mass occurrence of Illecebrum verticillatum in both associations. Moreover, a large cover of the following hygrophilous species was observed: species of the association Radiolion linoidis such as Hypericum humifusum, Radiola linoides and Centunculus minimus, of the classes Isoëto-Nanojuncetea -Juncus bufonius, Juncus capitatus, Gnaphalium uliginosum and Plantago intermedia as well as other moisture-loving species like the most numerous Veronica serpyllifolia, Polygonum hydropiper and Sagina procumbens. There was observed a mass occurrence of the following acidophilous weeds: Rumex acetostella and Spergula arvensis and others. Explanatory notes: numbers after species inform about numbers of columns in the table: S -phytosociological constancy, D -cover factor; In period II, one more association was distinguished, i.e. Echinochloo-Setarietum, as well as the community Setaria pumilla-Setaria viridis. The cover of Illecebrum verticillatum, all the species from Radiolion linoidis and Isoëto-Nanojuncetea and acidophilous species was markedly reduced. On the contrary, a higher share of the following nitrophilous species was observed: Chenopodium album, Stellaria media and Matricaria maritima subsp. inodora. Additionally, new species established, e.g. Veronica persica and Galinsoga parviflora. The overall number of stubble species was lower: 85. The average number of species per relevé was lower, too, and amounted to 27. Period III saw an even faster rate of disappearance of species and whole syntaxa representing the class Isoëto-Nanojuncetea. What is more, phytocoenoses of the association Spergulario-Illecebretum verticillati were not found, whereas rare patches of Digitarietum ischaemii Illecebrum verticillatum were replaced by numerous plants of Polygonum hydropiper, Peplis portula and Bidens tripartita.

Changes in weed communities of cereal crops
At the beginning of the study, rye was the only winter cereal, with its cover ranging from 45 to 60%. These agrocenoses included the association Arnoserido-Scleranthetum, either typical or the variant with Illecebrum verticillatum, as well as the community with Aperion spicae-venti, the variant with Illecebrum verticillatum. The vertical structure of the stand was not distinct and often consisted of just one stratum. Thinner rye stands at the stage of grain maturation favoured the development of ground weeds. Illecebrum verticillatum plants were common and were accompanied by numerous species of the association Radiolion linoidis and of the class Isoëto Nanojuncetea, in which the species with the highest constancy and cover included the following: Radiola linoides, Centunculus minimus, Hypericum humifusum, Juncus bufonius and Juncus capitatus. Arnoseris minima was also a numerous characteristic species in the lowest layer, whereas Apera spica-venti was the dominant species in the upper one ( Table 2). Cereal communities were infested by 82 weedy species, on average 24 species per relevé.
In 2002-2004 the total area of land under winter cereals decreased and half of it was under Triticale. The average cover of this cereal was higher and reached 64%. Higher stand density substantially reduced the development of ground weeds. Agrocenoses in this period included the community Aperion spicae-venti, the typical variant and the hygrophilous variant with Juncus bufonius and the dominating species Apera spica-venti. The withdrawing species included Arnoseris minima and other acidophilous species. What is more, there was a drastic drop in the constancy and cover of the following species from the order Radiolion linoidis: Illecebrum verticillatum, Radiola linoides, Centunculus minimus, and Hypericum humifusum. The greater cover of Matricaria maritima subsp. inodora, Vicia tetrasperma and Polygonum lapathifolium subsp. pallidum indicates the improved nutrient status of the habitats. Agrocenoses included 66 species. The number of species per-relevé was slightly lower and ranged from 15 to 29, averaging 23 species. There was also a decrease in total weed cover.
Triticale was the only winter species cultivated in period III and its average cover reached 70%. The agrophytocenoses underwent further transformations; the association Vicietum tetraspermae, the typical variant with Juncus bufonius and Rhinanthus serotinus, became the leading dominant. Great numbers of new species, Bromus secalinus and Vicia villosa, were found in some patches. In addition, the following nitrophilous newcomers increased their cover: Matricaria maritima subsp. inodora, Sonchus arvensis and Galium aparine. Hygrophilous species of the alliance Radiolion linoidis became very rare, whereas moisture--lowing species characterised by higher nutrient requirements, like Bidens tripartita, increased their cover. The community was made up of 65 species, 22 species per relevé on average.

Changes in weed communities of tuber crops/maize
In period I, potatoes were grown for livestock under the traditional farming system. They were characterised by substantial secondary weed infestation. These phytocenoses included two associations; Digitarietum ischaemi was frequently found in the typical variant and the variant with Illecebrum verticillatum, whereas the variant with Echinochloo-Setarietum sperguletosum was infrequent (Table 3). Hygrophilous species from the class Isoëto-Nanojuncetea -Juncus bufonius and Illecebrum verticillatum, present in all patches at high cover, made them easily recognisable. These phytocenoses consisted, respectively, of a total of 61 and 19 species per patch, on average.
During the period of farming process transition, 60% of cropped land was under maize. Patches of Digitarietum ischemii were seldom, whereas patches of Echinochloo-Setarietum became the dominant association which was much more diversified internally compared to period I. Hygrophilous species representing the syntaxa analysed clearly withdrew from the phytocenoses. Similarly, there was a clear decrease in the number of acidophilous species, particularly Spergula arvensis, Anthemis arvensis and Rumex acetosella. Moreover, there was observed a marked increase in the share of panicoid weeds but the overall weed cover in maize decreased. Also, the number of species making up the phytocenoses and the average number of species per relevé diminished (58 and 15, respectively). The above-mentioned changes progressed during the period of intensive farming, when only maize was cultivated. The dominance of Echinochloa crus-galli increased by further 30% compared with the previous period. The number and cover of nitrophilous species increased, the greatest changes being observed for Thlaspi arvense. The overall number of species slightly decreased to a level of 50, but the average number of species per patch remained the same. Tabela  Explanatory notes: numbers after species inform about numbers of columns in the table: S -phytosociological constancy, D -cover factor; Explanatory notes: numbers after species inform about numbers of columns in the table: S -phytosociological constancy, D -cover factor;

Index of community dynamics and similarity
The comparison of the conditions in period I and II in the agrophytocenoses studied revealed changes leading to the impoverishment and simplification of communities. In the crop groups analysed, the number of disappearing and withdrawing species was not compensated by new taxa (Table 4).
92 species in stubble fields, 71 in cereals and 50 in tuber crops/maize displayed dynamic tendencies. The withdrawing species included stenotopic taxa, that is, hygrophilous and acidophilous species which were withdrawing due to changes in habitat conditions (Table 5). The group of spreading species was less numerous. These weeds have a wide ecological amplitude; moreover, they are usually common species/ taxa with a high nutrient requirement ( Table 6).
The comparison of the communities for the period analysed by means of Sørensen's index (SW s ) confirmed marked similarities between period I and II communities for all the crop groups analysed (Table 7). The changes in agrocenoses over these periods were slow. Much greater differences were found when periods II and III were compared. The value of the index diminished clearly, which was accompanied by an increase in field production intensification and changes in agrophytocenoses. The lowest value of the index was obtained when period I was compared with period III. The similarity was as low as SW s = 0.29 for tuber crops/maize.

DISCUSSION
The changes due to farming intensification taking place over 17 years in the communities with Radiolion linoidis indicated an improved nutrient status of these habitats. The community composition and structure changed; all the syntaxa with species representing the aforementioned association disappeared in stubble fields, cereals and tuber crops. They were replaced by associations widespread in Poland and characterised by wide amplitude of habitats where they grow. The association Echinochloo-Setarietum was observed in stubble fields and maize, whereas Vicietum tetraspermae and species-impoverished communities representing the association Aperion spicae-venti were found in cereals. The scale of these transformations is also reflected in the low value of Sørensen's coefficient. The analysis of the changes in species composition of the communities in period I and III demonstrated that the species disappeared much faster than new ones appeared (Table 4, 5). Many works, both Polish and foreign, have examined the issue of impoverishment and disappearance of specialised communities [2,5,[19][20][21][22][23][24].
Species that spread and reached the highest values of the dynamics index included eurytopic and nitrophilous species, such as: Echinochloa crus-galli, Chenopodium album, Galinsoga parviflora, Stellaria media, Matricaria maritima subsp. inodora and Elymus repens, which are believed to be common expansive weeds in Poland [25,26]. The establishment of these species is possible, because maize has become a dominant crop plant and now the area under maize is around 60% of cropped land. Communities establishing in maize consist of the smallest number of species (an average of 16 species per patch), compared with cereals or tuber crops. According to G o łębiowska and Kaus [27], the number of weedy species in maize depends on weed control methods and ranges from 11 to 16 species per relevé [28], whereas monoculture is associated with the following dominant species: Chenopodium album, Echinochloa crus-galli, Elymus repens and others [29]. The application of herbicides, e.g. triazine products, substantially reduces the development of weeds [28] whereas monoculture is associated with the development of weed dominance, for example Chenopodium album, Echinochloa crusgalli, Elymus repens, and others. Compensation of weeds which quickly develop resistance to herbicides has already been noticed in the agrocenoses studied, as exemplified by a mass occurrence of Echinochloa crus-galli CONCLUSIONS 1. Communities from the Radiolion linoidis alliance were greatly reduced due to changes in farming methods. 2. Acidophilous phytocenoses Spergulario-Illecebretum verticillati disappeared in stubble fields, while phytocenoses with Illecebrum verticillatum in cereals and tuber crops. 3. Various forms of the common association Echinochloo-Setarietum established in maize and stubble fields, whereas patches of Vicietum tetraspermae in cereals. 4. The greatest differences were found for the communities between study period I and III, as reflected by a low value of Sørensen's index (SW s =0.29). 5. The impoverishment of communities took place; the number of disappearing and withdrawing species was higher than the number of new taxa.