Resource availability and seedling establishment

PhD student

Ieva Bebre

Research Outline

The conversion of even-aged and often poorly structured pure stands to mixed stands are of particular interest since mixed forests are thought to be more sustainable from both an ecological and economical point of view. Mixed forest management in temperate zones often includes dispensing with clear-cuts, which in a long-term means that the next generation of trees will at least initially develop under the canopy of older generations. In order to promote regeneration of various tree species and ensure a species mixture, resource availability under the canopy has to be sufficient for a variety of species to grow and develop.
The Subproject 8 sets to quantitatively assess the impact of resource availability and mature tree species composition and density impact on tree seedling growth and biomass partitioning.
The project is based on two experiments:

  • a field experiment where direct seeding and planting of European beech, Norway spruce, and Douglas fir will be carried out in the preselected study sites (Intensive Measurement Plots, n=20) in fenced and unfenced subplots;

  • and a complimentary pot/ controlled experiment using light and nutrient gradient and planting the pots either as monocultures or mixtures of the studied species.

The work is divided into 3 main phases: 1st – setting up the experiments; 2nd – evaluating the seedling performance (incl. assessment of, e.g. overlaying canopy, ground vegetation, browsing effect); and the 3rd – seedling harvest at the end of the vegetation periods in order to assess biomass partitioning and nutritional status. The experiments will allow examining seedling survival, growth, and biomass partitioning as a function of species, age, size light availability, soil properties and competition and thus understanding the species-specific responses to limited resource availability (in terms of growth and biomass allocation) which is crucial for the management of mixed species regenerations by controlling canopy density.

Principal Investigator / Supervisor

Dr. Peter Annighöfer, Silviculture and Forest Ecology of the Temperate Zones, Faculty of Forest Sciences and Forest Ecology