Restoring forests involves all aspects of soil evaluation, a site-appropriate choice of tree species, fertilisation measures, but also forest management. Simple anaerobic conclusions based on the open-cast mining environment are not possible, as recultivation areas have specific growth conditions.
In the Lusatian lignite mining district, industrial mining of raw materials has left deep scars on a landscape scale. Since the start of scheduled forest recultivation at the beginning of the 20th century, around two-thirds of the areas returned have been afforested or left to natural reforestation.
As a component of the operational plans under mining law, forest recultivation shows how attractive, ecologically valuable and productive habitats can be created within a forest generation. Even experienced foresters find it difficult to differentiate between “dump forests” and similarly structured stands of the same age in open-cast mining areas.
The FIB e.V. supports forest recultivation by developing suitable cultivation and management recommendations for special site conditions, based on modern forest ecosystem research. Not only the growth of wood is of interest. Other equally important sustainability criteria for successful restoration include species and structural diversity, an intact nutrient turnover or the carbon balance of the new forests.
Last but not least, forest recultivation research is concerned with the use of soil-improving substances and fertilisers. Field trials and technical experiments are carried out for this purpose.
In the course of general global warming, an increase in the annual mean temperature in our region of around one degree Celsius since the 1960s can be demonstrated. This worrying trend is continuing. A further warming of 2.3 to 3.5 degrees Celsius is expected by the end of the century – depending on the climate scenario. By contrast, the further development of precipitation remains quite unclear. This makes it all the more necessary to develop forward-looking adaptation strategies that can cope with forecast uncertainties.
In the “Climate Risk Region of Lusatia”, as in open-air laboratories, different tree species and forest structures can be evaluated in terms of their climate and location dependency. FIB e.V. is currently investigating around 50 forest ecosystems typical of the region in terms of hydrology, soil and growth. Annual ring analyses provide information on forest development to date, but also on the reaction of tree species to extreme events.
After the summers of the century in 2018 and 2019, drastic losses in growth and vitality can be demonstrated. While the common pine, for example, is particularly susceptible to heat, Sessile Oaks and Birches react sensitively to precipitation deficits if the trees have had enough water available to produce abundant biomass by then.
Are dump forests and other forests on special sites stable in the long term? How sustainable is forest recultivation and how should the forest functions be assessed overall? Which tree species, origins and genotypes are particularly suitable?
At the FIB e.V. such and other ecological questions are answered with different methods. For example, water and material balance studies are carried out to characterise the system behaviour in more detail. Using complex forest growth simulations linked to climate scenarios, the future development of wood growth can be estimated. Particular attention is paid to mixed and unevenly aged stands.
Ecophysiological studies, for example on photosynthesis efficiency, provide information on the general vitality and drought or heat tolerance of woody plants. It can therefore be assumed that the growth pattern to date does not allow conclusions to be drawn about future forest growth. On the other hand, woody plants can adapt to environmental changes much more than previously assumed, be it through epigenetic mechanisms or adapted shape proportions.
For some time now, our research activities have concentrated on the conversion of site-unfavourable pure coniferous wood stands into near-natural mixed forests with a high proportion of hardwoods. This concerns both dump reforestation and “grown” forests. In this context, we are also testing new technologies for timber harvesting and logging. For example, since 2010 and in cooperation with the Brandenburg State Forestry Service, FIB e.V. has been conducting extensive technical trials under practical conditions.
The measures will be economically and environmentally sound, in particular to protect the soil from permanent damage and to ensure the passability of return routes. In addition to more “classical” soil-physical methods, such as the determination of pore size distribution or in-situ measurements of water infiltration, innovative imaging and analytical measuring methods are also used. High-resolution close-range photogrammetry is particularly promising as an alternative to terrestrial laser scanning (LiDAR).
Another key issue is the minimisation of nutrient exports in forest use. To this end, the nutrient stocks in the individual tree compartments are determined on the basis of biomass functions and sample tree felling, and transferred to the stand or timber harvesting measure via yield measurements.