Professor Lutz Eckstein is co-author in a new paper in the journal Applied Vegetation Science led by Yves Klinger (Justus-Liebig-University Giessen, Germany). The authors assessed the role of mowing machinery and endozoochory by migratory sheep as dispersal vectors in semi-natural grasslands by comparing the species compositions and traits of species found in the vectors to the regional above-ground vegetation and soil seed bank. Plant material from mowers (n = 12 from one date) and dung samples from migratory sheep (n = 39 from 13 dates) were collected and the dispersed plant species were determined using the emergence method. We compared the species compositions to the regional above-ground vegetation and seed bank using non-metric multidimensional scaling (NMDS) and indicator species analysis. Furthermore, we compared functional traits of the dispersed species to traits of non-dispersed species of the regional species pools by calculating log-response ratios and performing metaregressions.

Sheep in the Rhön Mountains. Photo by Yves Klinger.

We found that mower samples were more similar to the above-ground vegetation whereas dung samples were more similar to the seed bank. Mowers and sheep endozoochory favored the dispersal of species with different traits and phenologies. Species with small seed sizes were prevalent in both vectors. Mowers were less selective concerning most traits, but favored high-growing grasses such as Alopecurus pratensis and Trisetum flavescens. Sheep dung samples contained less grasses and more palatable species, such as Urtica dioica.

Log-response ratios dispersal vectors vs species pools of sheep vs above-ground. LDMC = Leaf Dry Mass Content, EIV N = Ellenberg Indicator Value for Nutrients. Zero indicates the mean value of the non-dispersed species from the respective species pool, bars show mean log-response ratios ± confidence intervals. Figure is part of Figure 3 in the paper.

Sheep endozoochory and mowing machinery are complementary dispersal vectors favoring species with differing functional traits. Sheep endozoochory enables dispersal of species that have unfavorable traits (e.g. low releasing heights) or phenologies for dispersal by mowing machinery. To ensure the dispersal of a high number of plant species in semi-natural grasslands, the interplay of different vectors should be considered.

Read more about the paper here: https://doi.org/10.1111/avsc.12579.