Abstract
Agricultural intensification has led to drastic population declines in Europe’s arable plant vegetation, and continuous monitoring is a prerequisite for assessing measures to increase and conserve remnant populations of endangered arable plant species. Unfortunately, strong variation in plot sizes and in-field locations makes comparison of current arable plant monitoring approaches difficult. This study compares different relevé approaches in conventionally managed arable fields in Northwest German farmland with respect to plant species detection success and time expenditure. We compared species detection rate and expenditure of time of six different relevé types in 45 conventionally managed arable fields (each 15 fields of wheat, maize, and rapeseed): field “Interior” plots (50 × 2 m); field edge plots: “Edge_30” (30 × 2 m), “Edge_50” (50 × 2 m), and “Edge_500” (500 × 1 m); “Subplots” (four dispersed plots of 5 × 1 m); and “Corner” plots (50 × 2 m). To determine species detection rate, the species richness recorded with a survey method was related to the field’s total plant species number as estimated from a survey of the entire field edge zone. With a species detection rate of 8.3% (median), interior plots were inadequate for characterizing the field’s arable plant vegetation. Edge_500 plots yielded the highest proportion of the field’s arable plant species pool (75.6%, including taxa of conservation value), followed by “Corner” plots (45.8%) and “Sublots” (32.6%). Edge_50 and Edge_30 plots detected less than 25% of the field’s species pool. The average time needed for a relevé was 20 min in Edge500 plots and 5–11 min in the other plot types. We suggest implementing Edge_500 plots as a standard monitoring approach in conventionally managed farmland due to its favorable ratio of detection success to expenditure of time. Our findings should be compared to methodological studies conducted in other regions, in different farmland management systems, and in landscapes of variable complexities.
Highlights
In former times, crop cultivation in the farmland was less intense, and many plant species were able to coexist with the crop
Since the 1950s–1960s, advanced soil cultivation techniques, the widespread application of herbicides, and increased fertilizer amounts that intensified competition with the crop have caused dramatic impoverishment of the arable plant vegetation in many regions of Central Europe and elsewhere, which manifested in large losses of arable plant cover and species richness and the collapse of once widespread arable plant communities (Albrecht et al 2016; Albrecht 1989; Májeková et al 2010; Meisel and von Hübschmann 1976; Meyer et al 2013)
The same sequence in species richness was found for the number of arable plant species and for the high-naturevalue species of arable land
Summary
In former times, crop cultivation in the farmland was less intense, and many plant species were able to coexist with the crop. In Central Europe, about 300–350 plant species have adapted to the frequently disturbed manmade habitat of arable fields. From a literature review, Leuschner and Ellenberg (2017) concluded that, in comparison to other habitats in Central Europe, the species richness and population size of arable plants have experienced the most significant decrease within the past 50–60 years. In a large number of fields of Central and Northern Germany, the resampling study of Meyer et al (2013) found a 23% reduction in the regional species pool and a decrease in median plotlevel species richness from 24 to 7 species in the field interior compared to the 1950s–1960s. The species loss was associated with a large decline in arable plant coverage. Meyer et al (2013) found that the median cover of arable plants declined from 30% in the 1959s–1960s to only 3% in 2009 in the interior of central and northern German fields
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