SP 11: Invasibility

Invasion - diversity interactions in subtropical forests: the interplay of herbaceous and woody species richness

Principal investigator(s):

Dr. Alexandra Erfmeier (Martin Luther University of Halle-Wittenberg)  

Co-Principal investigator(s):

Prof. Dr. Helge Bruelheide (Martin Luther University of Halle-Wittenberg)  

Phd candidate(s):

Ricarda Pohl (Martin Luther University of Halle-Wittenberg)  
Markus Germany (Martin Luther University of Halle-Wittenberg)  

Contact adress:

Martin Luther University Halle-Wittenberg, Institute of Biology / Geobotany and Botanical Garden, Am Kirchtor 1, 06108 Halle (Saale), Germany


Forest ecosystems are remarkable for including interactions between herbaceous and woody species and for interactions between forest strata in relation to species diversity. While the herb strata alone can have a substantial impact to forest ecosystem functioning, the structural complexity across strata, in addition, may allow for niche complementarity and facilitation.

Herb layer composition in different successional stages, Gutianshan National Nature Reserve (S. Both)

We focus on characteristics of the herb layer

(1) as a response variable to tree layer characteristics and

(2) as a predictor variable for productivity and invasion resistance towards exotic plant species.

(3) In addition, we study feedback effects of herb layer characteristics on the tree layer of young successional forest stages.

We use combined approaches of observational and experimental studies, including field surveys in natural forests and in the Main Experiment, seed addition experiments in common gardens and in the field, as well as controlled greenhouse experiments with artificial communities and with single species, to disentangle these interaction effects.

In this second phase, in particular, species richness and composition of the herb layer are studied as a function of environmental variables (Ecoscape approach) and of planted tree diversity in a grid of permanent plots at both sites of the Main Experiment. In return, the properties of the herb layer serve as covariates for identifying BEF relationships in other subprojects.

Measurements of functional traits of herbaceous species and indices of functional diversity of the herb layer are used to predict productivity and invasibility by other plant species and to test if invasions will be complementary, i.e. increasing functional diversity in the herb layer. The impact of tree species richness on herb layer assembly and invasibility is studied by functional group removal experiments. At the same time, these treatments are used to quantify feedback effects of the herb layer on growth and survival of trees.

Our subproject will help identifying interaction effects of strata level diversity and thus contribute to our understanding of ecosystem functioning in species-rich subtropical forests.

Experimental seed addition study within subplots in the Main Experiment (S. Both)