Abstract
<p>The aim of study was to evaluate diversity of segetal flora and its transformations over a more than 20-year period in 19 field habitats representative for cereal crops of southern Poland. The research hypothesis assumed that: (<em><strong>i</strong></em>) the diversity of habitat conditions determines the abundance of arable land flora, (<em><strong>ii</strong></em>) it also affects farming intensity which is the main cause of the decline in the biodiversity of agrocoenoses.</p><p>Based on 415 phytosociological relevés (sampled using the Braun-Blanquet method), weed species richness (Sr), phytosociological constancy of species (S), cover index (<em>D</em>), Shannon’s diversity index (<em>H</em>) and Simpson’s dominance index (<em>C</em>) were determined. Measurements were done for each habitat during two research periods. The results were subjected to ANOVA analysis. To assess the similarities of the studied habitats’ weed flora in each period and their changes over time, Ward’s hierarchical cluster analysis was used. The distance matrix was calculated from Jaccard’s similarity indices. The results are presented in the form of hierarchical trees.</p><p>The study showed that species richness of the weed communities and their diversity were strongly determined by habitat conditions. Preservation of the value of the diversity index and even its increase (especially in a considerable part of mountain habitats) showed that extensive methods of reducing weed infestation had remained at a similar level of efficacy during the 20-year interval. Hierarchical cluster analysis showed differences between the first and second study period in the weed communities for habitats of lowland soil complexes. The exception were the habitats with the greatest potential for crop cultivation, located on chernozems and rendzinas. In the mountain habitats, there were no significant changes in the segetal flora during the study interval. An increase in weed flora abundance indicates a lack of threats to the diversity of agrophytocoenoses in this part of Poland.</p>
Highlights
Numerous publications, issued during the last decade, showed significant changes in flora and segetal communities in Europe [1,2,3,4,5,6,7,8]
The main findings that are worthy of notice are following: ■■ The majority of effects are significant. ■■ The indices species richness (Sr) and H become higher in the second period, whereas index C diminishes, which is consistent with the meaning of these variables
The lists are supplemented with combinations of sporadic taxa occurring in lowland (Appendix S1) and mountain habitats (Appendix S2)
Summary
Numerous publications, issued during the last decade, showed significant changes in flora and segetal communities in Europe [1,2,3,4,5,6,7,8]. The authors emphasized the decline in diversity, the uniformity of phytocoenoses, and even the possibility of losing some of the weed species This phenomenon is usually caused by agricultural practice: changes in land use, reduced tillage and crop rotation, intensive mineral fertilization, purification of seed material, and especially the very common use of herbicides. Dąbkowska et al / The transformation of segetal flora richness and diversity point to the presence of weeds as specific indicators of the intensity of management and use of agricultural land [1,3,6]. According to these reports, in extreme cases, e.g., in Germany, there has been a drastic loss of weed species encountered [7]. Similar risks are present in Poland, especially in relation to weeds that are most vulnerable to the progressive intensification of farming [12,13,14]
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