11 November: Laura Rose

Land-use intensification in grassland ecosystems: effects from leaf to ecosystem

Laura Rose

Department of Ecology and Ecosystem Research, University of Goettingen, Germany

In the last 50 years, land-use changes in temperate grassland ecosystems occurred either by land-use intensification, i.e. increased fertilization, cutting frequency and stocking rate, or by abandonment of non-profitable sites mostly on low productive soils. Such land-use changes can have profound effects on the species composition, the amount of standing and produced biomass, and on biogeochemical cycles. I am going to present results from the GrassMan experiment, an interdisciplinary meadow experiment at the University of Göttingen, which is designed to investigate the effects of plant biodiversity, fertilizer application and different cutting frequencies on several aspects of grassland functioning.

Fertilizer application and alterations of the cutting frequency severely affect functional leaf traits: NPK-fertilization leads to generally higher leaf-level water use efficiency (WUE), accompanied by an increase in the specific leaf area and leaf nitrogen concentration. Cutting effects are more species specific. Besides these effects on leaf trait values, fertilization additionally alters the interspecific relationships between leaf traits.

Although the increase in leaf-level water use efficiency with fertilization is mirrored by an increase in WUE on the stand level, fertilization leads to higher evapotranspiration rates and thereby decreases ground-water recharge. This is mostly attributed to the higher amount of biomass produced in fertilized compared to unfertilized meadows. Irrespective of its positive effect on aboveground biomass production, fertilization increases nitrogen leaching.

28 October: Justin Thomas Wynns

Status of an ongoing systematic study of Plagiothecium.

Justin Thomas Wynns

dept. Agriculture and Ecology, Copenhagen University


Plagiothecium is a conspicuous and widely distributed genus of pleurocarpous mosses, typically growing on soil or humus in forests, heaths and swamps. The genus is well characterized morphologically by plants that are mostly medium-sized to large, flattened, and highly glossy, with decurrent leaves. Many species produce characteristic small uniseriate gemmae in abundance.

Plagiothecium appears to be a mostly natural genus that includes several species-complexes and some anomalous species. A large number of taxa have been described, and some are very poorly known. Although several excellent regional treatments of the genus exist, Plagiothecium has not been monographed on a worldwide scale. The goal of my study is to obtain a molecular phylogeny of Plagiothecium that will serve as the systematic basis for a projected worldwide monograph.

Pleurocarpous mosses have undergone rapid morphological diversification in recent evolutionary history, and DNA sequence data can be very uniform in this group. To identify the most useful genetic loci for evolutionary reconstruction in Plagiothecium, I have sequenced a number of different loci (mostly chloroplast, some nuclear) for a small number of taxa. In this Ph.D. Status Seminar, I discuss the results of this ongoing initial phase of my study, including the taxonomic conclusions that are emerging.

14 October: Toby Kiers

Reciprocal Rewards in the Rhizosphere: Underground markets and the evolution of cooperation in plant-fungal mutualisms.

Toby Kiers

Free University Amsterdam, Department of Animal Ecology, Faculty of Earth and Life Sciences, Netherlands

Associating with microbes in the rhizosphere can have both costs and benefits for host plants. Because associations generally involve multiple microbial genotypes varying in mutualistic benefit, a potential tragedy of the commons can arise. How do plants maintain cooperation with the most beneficial rhizosphere microbes over the course of evolution? Specific mechanisms may be employed that reduce the fitness benefits to microbes from “cheating”. In the mycorrhizal mutualism, the fungal symbiont cannot be “enslaved.” Rather, the mutualism is evolutionarily stable because control is bidirectional, and partners offering the best rate of exchange are rewarded. The existence of underground biological markets will be discussed.