Markus Germany

Scientific Guest
Markus Germany



My name is Markus Germany and I finished my diploma in Biology at the Johannes-Gutenberg University Mainz, Rheinland-Pfalz. Nature conservation and environmental protection have built the central motivation for studying biology. During my scientific education, I increasingly realized the vital importance of biodiversity for ecosystem functioning and during my diploma thesis about “Diversity fragmentation relationships of island like movile hills in the Târnava Mare Region in Transylvania (Romania)”, I was impressed by the particularly high species richness in Romanian temperate grassland ecosystems, as it is only rarely encountered in Europe today.

Biodiversity is threatened in many ways, yet, the consequences are not fully understood. In particular, the interactions between biodiversity and ecosystem functions must be much better understood in more complex systems as being provided in forests with their multiple structural layers, each of them contributing separately to the overall diversity. New insights must be obtained to grasp this multicomplexity of diversity. Within my PhD project, I aim to add knowledge on strata specific responses to diversity in experimental subtropical forests only rarely studied to date. 

I joined iDiv because…

yDiv gives me the chance to profit from a larger interdisciplinary network that allows to assess the multicomplexity of my study system also from multiple scientific perspectives. I want to learn more about new fields and methods.

Research Project


“The role of herb layer characteristics and productivity for forest ecosystem functioning”

In forests, the herb layer contributes a great deal to the overall biodiversity, yet is also able to alter tree and shrub diversity and to influence the nutrient content of the ecosystem. Nonetheless, most forest biodiversity studies, just as discussions of threats to biodiversity often ignore the functional role of herb layer.

In my PhD project, integrated within the “BEF-China” Experiment (FOR 891), a large tree diversity experiment in the subtropics, I address the mechanisms behind tree layer x herb layer interactions by taking profound knowledge of environmental covariation (quantified as the Ecoscape) into account. Thereby, one focus is to quantify herb layer characteristics and their feedback effects on the trees along an experimental tree biodiversity gradient. In addition, I study effects of herb layer x tree diversity interactions on tree recruitment and address the role of the herb layer for the nutrient balance of forests.

The experimental set up of “BEF-China” is designed to separate tree species richness effects from identity effects since all species are equally represented at each diversity level “broken-stick” design. Moreover it is possible to address strata-overarching questions like biodiversity–productivity relationships and to perform additional manipulations of the herb layer along an experimental gradient of tree species richness.

Research question / Hypotheses

As major objectives, we test

1.1.) for increasing effects of tree diversity with diminishing influence of the Ecoscape on the herb layer with the time,

1.2.) for changes in tree diversity effects on the herb layer in different nutrient and competition environments (as mediated by phosphate fertilization and no weeding treatments)

2.) for Janzen-Connell effects by studying woody recruitment, and

3.) for important quantitative contributions of the herb layer to the whole CNP balance of the ecosystem.

Accordingly, I assume, that productivity and diversity of the herb layer will be increasingly modified by tree layer diversity and identity with the time, while signals of the Ecoscape will diminish. Increasing competition within the herb layer as well as modified P levels in the soil will change herb layer productivity, composition and diversity since individual species and/or groups (e.g. trees) will benefit more than others.

As major Janzen-Connell effects, I expect to find that survival of tree recruits will decrease and growth will be more limited with increasing proximity to nearest parent plants (distance dependence in seedling recruitment) as well as with increasing seedling density (overcompensating density dependence in seedling recruitment). Hence, leaf herbivory and plant pathogen load will increase with proximity to the nearest conspecific adult tree and with increasing seedling density.

Finally, herb layer foliage will contain higher proportions of essential nutrients than expected from biomass proportions. Thus, P-fertilization will have stronger effects on the herb layer than on the tree layer, in particular on the functional group of grasses.

Links to the main questions of iDiv / Links to other iDiv projects?

In this project, I partition forest diversity into structural components by studying the pattern and emergence of herb layer diversity in response to the tree layer diversity and to tree identity as well as to the Ecoscape. By testing for Janzen-Connell effects, I study effects of biotic components of the Ecoscape on tree layer responses As explanation for the maintenance of biodiversity, I test whether and to what extent regular weeding, phosphorus fertilization and canopy closure can alter herb layer diversity. As consequences for ecosystem functioning, I also investigate the degree as to which Ecoscape as well as tree layer diversity and identity can alter herb layer productivity and composition. At last we analyze the role of the herb layer diversity for the nutrient balance, and thus its overall contribution of ecosystem functioning.

Methods to be used

In order to assess herb layer productivity, composition and diversity in response to tree diversity, identity and to the Ecoscape as well as to test for changes within the herb layer by phosphate fertilization and no wedding treatments, first data on herb layer composition have been collected in each 35 plots along a tree diversity experiment at two sites, each implying subplots of phosphorous fertilization, annual weeding and no weeding (i.e. admitting all types of weeds, n= 207). Biomass served as a proxy for herb layer productivity in response tree diversity. In addition, LAI and light measurements were performed. Ecoscape data (here: soil data) are available from the “BEF China” database. Phosphor stock was determined by leaf samples of Miscanthus floridulus (as a phytometer available in all plots).

An overall species inventory at the plot level is meant to be performed to quantify leaf nutrient concentrations and nutrient contents in the herb layer (including P and N, Ca, Mg, K).

Janzen-Connell effects as an explanation for the maintenance of biodiversity and to predict the development of the experiment after weeding will be reduced, will be tested in seedling addition trials with 18 different species into the Main Experiment of BEF-China as well as in a Common Garden experiment. Preliminary tests for Janzen-Connell effects have been conducted to a smaller extent (5 species) in order to detect potential risks in advance.

To quantify the natural seed levels near and far from parent trees, seed traps and adjacent small-scale plots, have been installed in 58 plots. This is an ongoing experiment in 2015.

Short CV


Since 04/2014
PhD student at the Institute of Biology / Geobotany and Botanical Garden, Martin Luther University Halle-Wittenberg

from 1st of March 2015
Kiel University
Supervisor: Prof. Dr. Alexandra Erfmeier
Title: The role of herb layer characteristics and productivity for forest ecosystem functioning

Diploma thesis at the Institute of Botany and Botanical Garden, Johannes Gutenberg University Mainz
Supervisor: Prof. Joachim W. Kadereit, Ph.D.
Title: Diversity-fragmentation relationships of island-like movile hills in the Târnava Mare Region in Transylvania (Romania)

Diploma examination in the subjects of botany, ecology, zoology

04/2006 - 04/2013
Study of Biology at the Johannes Gutenberg University Mainz

iDiv publications


M. S. Germany, H. Bruelheide, A. Erfmeier

(2021): Drivers of understorey biomass: tree species identity is more important than richness in a young forest. Journal of Plant Ecology 14(3) *

Germany, M. S., Bruelheide, H., Erfmeier, A.

(2019): Janzen-Connell effects in a forest BEF experiment: Strong distance-dependent seedling establishment of multiple species. Ecology 100(8)

Germany, M. S., Bruelheide, H., Erfmeier, A.

(2017): Limited tree richness effects on herb layer composition, richness and productivity in experimental forest stands. Journal of Plant Ecology 10(1), 190-200
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Martin Luther University Halle-Wittenberg
Institute of Biology / Geobotany and Botanical Garden
Am Kirchtor 1
06108 Halle/Saale

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+49 345 5526263
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Martin Luther University Halle-Wittenberg

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