Flora in abandoned fields and adjacent crop fields on rendzina soils in the Zamość region

A floristic inventory of segetal flora was carried out in abandoned fields and adjacent crop fields on rendzina soils in the Zamość region in the year 2010. This study found a total of 130 weed species belonging to 30 botanical families. The following families were represented most frequently: Asteraceae, Fabaceae, Poaceae, Lamiaceae, Scrophulariaceae, and Brassicaceae. In the segetal flora, apophytes are dominant (55% of the total flora), with the highest number of meadow and xerothermic grassland species among them. Archeophytes (38%) predominate in the group of anthropophytes. The species characterized by the highest constancy classes and reaching the highest cover indices posed the greatest threat to crops in the study area. The following weeds are most frequently found in fallow fields: Consolida regalis, Cichorium intybus, and Sinapis arvensis, while Papaver rhoeas is the greatest threat to cereal crops grown on rendzina soils.


Introduction
At the turn of the 20th and 21st centuries, Polish agriculture was characterized by a continuous process of changes both in the ownership structure and in land use directions [1].In 2002 the area of set-aside and fallow land in Poland was 2.3 million ha, which accounts for 19.7% of arable land area [2].In Lubelskie Voivodeship (province), the low profitability of agricultural production and difficulties with selling agricultural products produced in farms have resulted in an intensification of the process of setting aside and fallowing arable land.In 1999 a total of 71 100 ha of arable land was set aside or fallowed, which accounted for 5.3% of its total area.Until 2003 there was a significant increase in the area of set-aside and fallow land, which was 92 800 ha, i.e., 8% of arable land area.The abandonment of agricultural production in crop fields involves various risks, including the undesired and uncontrolled appearance of agricultural pests [3].Vegetation growing in set-aside land flowers, bears fruit, matures and produces seeds that get into the soil and can maintain viability for many years.Apart from that, the seeds of anemochores can migrate to adjacent crop fields or can be carried over large distances [4,5].Wasteland and set-aside land undergoing secondary succession are often considered to be a source of weed infestation of crop fields [6][7][8].In the first years after fields cease to be cultivated, annual weeds and species that occurred in the last cultivated crop grow predominantly in such fields [9,10].Younger abandoned fields have more favorable conditions for weed growth than crop stands or stubble fields.Weeds in abandoned fields can use habitat resources throughout the entire growing season.They have a lot of room and unlimited access to light.Their growth is not disturbed by the crop plant dominant in the field and by agronomic treatments used [11].Weeds can reach larger sizes and produce more seeds.Therefore, much more fruits and seeds are found in the topsoil of an abandoned field than in a cultivated field [12,13].In addition to secondary succession that leads to the restoration of vegetation characteristic of a given type of habitat, other adverse ecological processes also take place in set-aside land and nitrogen leaching and erosion can be included in them [6,14].The early stages of setting aside land diminish the aesthetic qualities of landscape and moreover biocoenoses in abandoned fields lead to the accumulation of diaspores of segetal and ruderal weeds as well as of crop pests and diseases [7,12,15,16].Anemochorous weeds found in set-aside land are an enormous threat to crop plants that are grown in its vicinity [17,18].The presence of runners of couch grass and perennial weeds causes heavy topsoil sodding and hinders the restoration of a field to agricultural use [14].Therefore, an abandoned field brings about the need to increase crop protection in neighboring farmland [19].
The growth of vegetation in set-aside land depends primarily on natural ecological factors, among which soil plays an important role (inter alia, its granulometric composition, nutrient availability, pH), while secondary succession proceeds in the direction of replacement communities for a given habitat [15,20].
The aim of the present study was to compare weed infestation in abandoned fields and adjacent crop fields on rendzina soils in the Zamość region and to identify segetal species that are the greatest threat to crop fields.

Material and methods
The study of weed infestation in abandoned fields and adjacent crop fields was conducted in cereal crop fields in the villages of Brody Duże and Niedzielska located in the municipality of Szczebrzeszyn as well as in the village of Borowina Sitaniecka in the municipality of Stary Zamość.In the study, 22 relevés made in 2010 using the Braun-Blanquet method were compared [21].
The constancy class (S), i.e., the percentage of occurrence of a particular species in the relevés of a given association expressed using a five-point scale (I-V), was calculated for each species.The cover index (D), which denotes the average cover of a species in the relevés multiplied by 100 [21], was also determined.Plant species nomenclature follows Mirek et al. [22].The soil type and soil complexes in terms of agricultural usefulness were determined based on agricultural soil maps at a scale of 1:5000 [23].

Weed infestation in abandoned fields on rendzina soils
Based on 10 relevés, 11 weed species were found in abandoned fields on rendzina soils.Weeds of the highest constancy classes and cover indices determine the characteristics of agrophytocenoses in set-aside land.Fourteen species classified in constancy classes V and IV with a high cover index had a major contribution to weed infestation in abandoned fields (Tab.1).The following species were dominant contributors to weed infestation in abandoned fields on rendzina soils: Taraxacum officinale, Daucus carota, Melilotus officinalis, Elymus repens, Campanula rapunculoides, Papaver rhoeas, Consolida regalis, Medicago lupulina, Matricaria maritima subsp.inodora, Cichorium intybus, Convolvulus arvensis, Avena fatua, Sonchus arvensis, and Cirsium arvense (Tab.1).Nearly 60% (i.e., 84) of all species (Tab.2), were classified in low constancy classes (I-II).
The segetal flora in abandoned fields belongs to 29 botanical families.In terms of the number of species, the richest families are as follows: Asteraceae, Fabaceae, Poaceae, Lamiaceae, Scrophulariaceae, Brassicaceae, Caryophyllaceae, Euphorbiaceae, Boraginaceae, and Apiaceae.Three species were included in each of the following families: Ranunculaceae, Polygonaceae, Geraniaceae, and Rubiaceae.
In abandoned fields, they are represented by 66 species, which accounts for 59% of the total recorded flora (Fig. 1).Meadow species (24-35%), followed by xerothermic grassland species (23-35%), are dominant among various groups of apophytes.Waterside and wetland apophytes comprise 7 species -11%, forest and thicket apophytes -9 species, i.e. 14%.The lowest number was recorded for apophytes of dunes, outwash plains and sandy grasslands, since it was only 3 taxa -5% (Fig. 2).Within the study area, common apophytes include the following: Taraxacum officinale, Melilotus officinalis, Elymus repens, Campanula rapunculoides, Medicago lupulina, Cichorium intybus, Convolvulus arvensis, Sonchus arvensis, and Cirsium arvense.Anthropophytes were also a heterogeneous group in terms of naturalization.The oldest ones, archeophytes (39 species), were dominant among them and they accounted for 35% of the total flora (Fig. 1).Among archeophytes, Daucus carota created abundant populations.The number of kenophytes (plants introduced at the turn of the 15th and 16th centuries), represented by epecophytes, was 4 species (Fig. 1).Ergasiophygophytes, presently cultivated plants that have escaped into the wild, among others Avena sativa and Triticum aestivum, had a small proportion in the flora of the study area (Fig. 1).

Weed infestation in cereal crops on rendzina soils
Segetal communities of high species diversity are found in cereal crops grown on rendzina soils.Eighty weed species were found in 12 relevés.The following species were dominant contributors to weed infestation in cereal crops  The segetal flora in cereal crops belongs to 29 botanical families.In terms of the number of species, the richest families are as follows: Asteraceae, Fabaceaee, Poaceae.The species-richest genera are the following: Vicia -5 species, Veronica -5 species and Sonchus -3 species.
Within the study area, common apophytes include the following: Campanula rapunculoides, Stellaria media, Polygonum aviculare, Chenopodium album, and Taraxacum officinale.Anthropophytes were also a heterogeneous group in terms of naturalization.The oldest ones, archeophytes (43 species), were dominant among them and they accounted for 54% of the total flora (Tab.1).Among archeophytes, the following were found in greatest numbers: Papaver rhoeas, Consolida regalis, Avena fatua, Lathyrus tuberosus, Sinapis arvensis, and Melandrium noctiflorum.The number of kenophytes (plants introduced at the turn of the 15th and 16th centuries), represented by epecophytes, was 4 species -5% (Tab.1).Ergasiophygophytes, presently cultivated plants that have escaped into the wild, among others Pisum sativum, had a small proportion in the flora of the study area.

Discussion
The floristic composition and the degree of weed infestation in crop fields depend on a multitude of natural and artificial habitat factors.Soil is the most important natural factor.Its mechanical composition, pH, humus and nutrient content as well as moisture content largely determine the species composition of segetal communities [24].Rendzina soils are generally characterized by greater species richness of segetal weeds than other types of soil.
In the segetal flora on rendzina soils in the study area, 130 vascular plant species (excluding basic crop plants) were found in abandoned fields and cereal crops and they

Apophytes 40%
Epecophytes 5% Ergasiophygophytes 1% Archeophytes 54% represented different ecological groups, life forms and origin.Thus, this is quite a large number of species given that the study covered a small area.A similar state of segetal flora has been observed in other parts of our country, among others in Żuławy Wiślane -176 species [25], and Beskid Wyspowy (Island Beskids) -173 species [26].Within the buffer zone of the Roztocze National Park, 233 weed species were found [27].
Based on the present study conducted using the Braun-Blanquet method, the species diversity of the segetal flora in abandoned fields and adjacent cereal crop fields can be compared.The communities in abandoned fields are characterized by higher richness.A total of 111 weed species were found in these fields, while in cereal crops -80 weed species.Weeds of the highest constancy classes and cover indices determine the characteristics of the agrophytocenoses studied.Twenty four species classified in constancy classes V and IV with a high cover index had a major contribution to weed infestation.More species occurred in abandoned fields -14 species, whereas in cereals 10 species were found.
The higher number of species included in the lowest constancy classes is evidence of the low stability of the segetal weed communities and their ongoing dynamics [20].
Species of native origin, apophytes that migrate to crop fields from other natural or semi-natural plant communities, are predominant in the segetal flora of the study area, like in other regions of Poland [25,[28][29][30][31][32].
A total of 71 species are found in abandoned fields, which accounts for 55% of the total recorded flora.32 species occur in abandoned fields and 66 species in cereal crops.Meadow species (26 species: 9 -abandoned fields, 24 -cereals), followed by xerothermic grassland species (23 species: 8 -abandoned fields, 23 -cereals), are predominant among various groups of apophytes.Forest and thicket apophytes include 11 species (8 -abandoned fields, 9 -cereals), whereas waterside and wetland apophytes comprise 7 species (5 -abandoned fields, 7 -cereals).The lowest number was recorded for apophytes of dunes, outwash plains and sandy grasslands, since it was only 4 taxa.Within the study area, common apophytes include the following: Taraxacum officinale, Daucus carota, Melilotus officinalis.
The oldest species of natural origin are archeophytes; 50 archeophytes are found within the study area, which accounts for 38% of the total recorded flora.The following species occurred in greatest numbers: Sinapis arvensis, Melandrium noctiflorum.The number of plants introduced at the turn of the 15th and 16th centuries, represented as epecophytes, was 6 species -5% of the total flora.Ergasiophygophytes, presently cultivated plants that have escaped into the wild, among others Avena sativa, Triticum aestivum, and Pisum sativum, had a small proportion in the flora of the study area, only 2% of the recorded flora.
Similar proportions of particular weed groups were also observed within the area of the Skierbieszów Landscape Park [24].
When we compare weed infestation in abandoned fields and adjacent crop fields, the most common and most frequent species is Papaver rhoeas which belongs to the family Papaveraceae.It reached the highest degree of constancy (class V) both in abandoned fields and in cereals, while its cover index was 1180.0 in abandoned fields and 440.8 in cereals.It has also found optimal conditions for growth on rendzina soils within the buffer zone of the Roztocze National Park [20].
Calciphilous species, such as Muscari comosum, were found both in cereal crops and in abandoned fields.Many of these species were classified as rare taxa in our segetal flora [33].These species reached much higher degrees of constancy in abandoned fields than in adjacent crop fields.

Conclusions
A total of 130 weed species belonging to 30 botanical families were found on rendzina soils in the Zamość region.The species from Asteraceae, Fabaceae, Poaceae, Lamiaceae, Scrophulariaceae, and Brassicaceae were represented most frequently.
In the segetal flora, apophytes (55% of the total flora) predominated, with the highest number of meadow and xerothermic grassland species among them.Archeophytes (38%) predominate in the group of anthropophytes.
The species characterized by the highest constancy classes and reaching the highest cover indices posed the greatest threat to crops in the study area.
The following weeds are most frequently found in abandoned fields: Consolida regalis, Cichorium intybus, Sinapis arvensis, and Convolvulus arvensis, while Papaver rhoeas was the greatest threat to cereal crops.

Fig. 1
Fig. 1 Percentages of historical-geographical groups in the segetal flora found in abandoned fields on rendzina soils in the Zamość region.

Fig. 2
Fig. 2 Origin of apophytes in the segetal flora found in abandoned fields on rendzina soils in the Zamość region.

Fig. 3
Fig. 3 Percentages of historical-geographical groups in the segetal flora found in cereal crops on rendzina soils in the Zamość region.

Fig. 4
Fig.4 Origin of apophytes in the segetal flora found in cereal crops on rendzina soils in the Zamość region.
Weeds found on fallow fields and in cereal crops on rendzina soils in the Zamość region, according to the constancy class (S).
Number of weed species found on rendzina soils in the Zamość region, according to their constancy classes.