DOI: 10.25829/bexis.19166-1.2.9
title: Phytometer data of an experiment with transplanted species of contrasting geographic range types under manipulated biotic interactions (herbivory and competition) and different land-use regimes in Germany, 2009 - 2010

description: Geographic plant distribution is often assumed to be predominantly limited directly by the climatic tolerances of species. However, the role of climate is nowadays known to be mainly an indirect one by mostly mediating dispersal and establishment, species interactions or habitat characteristics, which all are often modified by human land use. In these complex systems, negative biotic interactions are predicted to increase in relative importance towards benign climate conditions. We tested this hypothesis experimentally by exposing plant species with different geographic distribution ranges to different climates, biotic interactions and land use. The dataset is the basis of the publication: Welk, A., Baudis, M., Böckelmann, J., Welk, E & Bruelheide, H. (2019): Plant species´ range type determines local responses to biotic interactions and land use. Ecology. doi:10.1002/ecy.2890
description: Theory: We present results of a fully crossed two-year transplantation field experiment replicated in 45 plots in three study regions along a precipitation gradient across Germany. We manipulated biotic interactions (presence/absence of competition and mollusk herbivory) in grasslands of different management regimes (meadows, mown pastures, pastures). The transplanted phytometers consisted of six congeneric species pairs, each representing one oceanic and one distinctly more continental range type. The oceanic range type is predominantly distributed in benign climate conditions in Western Europe, while the more continental type is distributed in regions with more stressful climate conditions in Eastern Europe. This experimental setting allowed us to study the impact of negative biotic interactions along an abiotic stress gradient under realistic land-use conditions. |Measurements Type: To study the impact of the species´ range type on plant survival and growth in interaction with land use practices, competition and herbivory, we used six congeneric species pairs. The species of each pair differed in geographical distribution range: each one species representing the oceanic and the continental range type, respectively (Welk et al. 2019: Appendix S2: Table S1). Assignment to the oceanic and continental range type was based on the degree to which the species' distribution range extends into the oceanic climate regions of Western Europe (distribution maps of the species can be found in Welk et al. 2019: Appendix S2: Fig. S1-S6). Accordingly, the following plant species pairs were used in the experiment (oceanic / continental): Carlina vulgaris / Carlina biebersteinii, Centaurea scabiosa / Centaurea stoebe, Dianthus deltoides / Dianthus carthusianorum, Koeleria pyramidata / Koeleria macrantha, Scabiosa columbaria / Scabiosa ochroleuca, Silene nutans / Silene otites (details of species characteristics in Welk et al. 2019: Appendix S2: Table S1). |instruments: in the field: ruler in the lab: laboratory scales, epson scanner and winfolia |procedures: We studied the effect of biotic interactions by removal of competitors and mollusk exclosures. Plant responses to these treatments were assessed by monitoring phytometer individuals of 12 plant species, which were transplanted into the experimental plots (detailed information see below). On each of the 45 selected experimental grassland plots, a 3.5 x 6.5 m section was divided into eight square subplots (1 m2), separated by margins of 0.5 m (Welk et al. 2019: Appendix S1: Fig. S2). On each subplot, a maximum number of 16 planting positions were available with a minimum distance of 20 cm between the phytometer plants. The subplots were subjected to different treatments. On each four of the eight subplots plants were released from competition by removing neighbour plants and from herbivory by excluding mollusks. Both treatments were fully crossed, resulting in four treatment combinations with two replicates each. Treatment combinations were assigned randomly to subplots. The whole experiment lasted over two vegetation periods from April 2009 to August 2010. In the competition treatment, plant biomass in a 10 cm radius around the phytometer was removed. To minimize disturbances of the soil structure which might have resulted in fertilization effects, we extracted a cylindrical soil core of 10 cm length / 10 cm depth, removed the aboveground biomass of this soil core and put it back upside-down (see Welk et al. 2019: Appendix S1: Fig. S3). Then, one phytometer plant was planted into the center of the soil core. Although this treatment involved some minor soil disturbance it kept the immediate neighborhood of the target plants free from competitors for several months. Since all plots were established in managed grassland sites of similar productivity with fully closed vegetation cover, competition intensity was comparable among plots. The most common resident species are listed in Welk et al. 2019 (Appendix S1: Table S1). To exclude mollusks, four subplots were fenced with metal frames (IRKA, Typ 1, R+M Gartenbedarf, Rehling, Germany; Welk et al. 2019: Appendix S1: Fig. S4). Additionally, mollusk repellent was applied within these plots (Ferramol, W. Neudorff GmbH KG, Emmerthal, Germany). We inspected the experimental plots regularly every eight weeks (except in winter) and maintained the treatments by manually removing newly upcoming competitors in the 10 cm radius of the phytometer plants or applying new mollusk repellent, respectively. All planted phytometers were watered once after transplantation to ensure initial establishment. At the time of planting, the number of leaves was counted for calculating relative growth rates (RGR) of leaf number according to Hunt (1990). To test the effectiveness of the mollusk exclosure treatment we estimated the proportion of consumed leaf area of all phytometers in autumn 2009. Damaged leaves of each plant were counted and then the percentage of consumed leaf areas of five randomly chosen damaged leaves were visually estimated in following classes: from 1-5 % in 1-percent-steps, from 5-95 % in 5-percent-steps. In August 2010, we harvested above- and belowground biomass, counted leaf number and measured plant height of all phytometers. As a measurement for reproductive capability we counted the flowering units of each flowering phytometer. At the same time, we also sampled one middle-aged and, if possible, undamaged leaf per individual for determinations of specific leaf area (SLA). As it was not possible to scan the fresh leaves, we dried them in the field between papers sheets and later scanned the dried leaves in the laboratory. Determinations of leaf area were conducted with a epson scanner and the programm winfolia. |