Daniel Rieker (Doctoral student)

Ph.D. Student, since 2020 Goethe-University Frankfurt

M.Sc. Landscape ecology, 2016-019 University of Münster

B.Sc. Geography, 2012-2016 University of Augsburg

Research Interest

My research interests are the reciprocal interactions among ecosystems and species, predominantly plants, lichens, and bryophytes in cultivated landscapes. Due to an increasing transformation of ecosystems by human activities, biodiversity is endangered. Each ecosystem has a specific biodiversity threshold down to which ecosystem processes and functions are performed and to maintain resilience. Below this biodiversity threshold, these processes are impeded, and the ecosystem changes. Hence, I am keen to investigate what drives biodiversity and develop evidence-based conservation recommendations to achieve the goals of different nature conservation strategies. For this, I am interested in comparing the diversity of organisms across systematic kingdoms on temporal and spatial scales and along use-intensity gradients.

Forest ecosystems are among the most anthropogenically modified ones. Besides homogenization and fragmentation, the logging of trees has a crucial impact on forest biodiversity. Saproxylic communities are highly diverse, and their habitat abundance decreased by a decline in deadwood volume and heterogeneity. Since these communities drive decomposition and soil formation, and nutrient recycling, high diversity in deadwood biocoenosis seems important to maintain ecosystem processes. Previous research has mostly focused on a specific realm, but cross-taxonomic research is necessary due to strong interactions between saproxylic species. Otherwise, derived conservation methods focus on a small subset of the occurring species diversity with potential negative effects on other than the targeted species group.

This issue is addressed in the joint research effort in the BELongDead experiment of the Biodiversity Exploratories. Funded by the Deutsche Forschungsgemeinschaft (German Research Foundation) I analyze data of saproxylic beetles, fungi and bacteria via a diversity partitioning. With this analysis, it is possible to detect the relevant scales for saproxylic biodiversity conservation and answer the question: Does the mere presence of a deadwood stem, irrespective of tree species, determine the presence and absence of most deadwood-depending species or does it require a diverse array of deadwood tree species over a larger area?

Selected Research

R.J. Heim, A. Bucharova, L. Brodt, J. Kamp, D. Rieker, A.V. Soromotin, A. Yurteav, N. Hölzel (2020): Post-fire vegetation succession in the Siberian subarctic tundra over 45 years, Science of the Total Environment, DOI: 10.1016/j.scitotenv.2020.143425

Research

► Biodiversity Exploratories
The Biodiversity Exploratories are a large-scale and long-time biodiversity experimental set up, funded by the German Research Foundation. In three climatically different regions of Germany, the influence of management on the biodiversity of forests and grassland is studied through a wide range of fields of research ranging from microbes, herbs, and butterflies to deer and trees.

Multitrophic functional diversity in deadwood

► BELongDead – Biodiversity Exploratories Long term Deadwood

In this experiment, 1140 logs of thirteen tree species (9 deciduous, 4 coniferous) were placed in different forest sites in 2009. On these logs, the biodiversity of beetles, fungi, bacteria, mosses, and lichens is studied and set into the context of molecular and biochemical mechanisms and processes of wood decomposition in relation to forest management practices and geographical scale. Besides assembly processes and succession of these organisms on different host species, their influence on decomposition rates and vice versa are examined.

► BESterile – Biodiversity Exploratories Sterile
In a new setup, 72 logs from the two most abundant tree species in Germany Fagus sylvatica and Picea abies will be exposed to gamma rays and placed beside the BElongDead experiment. The sterilized logs will help clarify if differences in fungal diversity on logs are caused by host tree characteristics or the endophyte communities.