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Ecological Effects of Energy Nurse Crops - Forest Restoration and Biomass Production

concluded 12/2014

Summary

 

 

Storms, droughts, and pest insect outbreaks regularly disturb forests, in particular those that are characterized by tree species that are not in accordance with site conditions. Ordinary restoration methods establishing juvenile target trees in open areas often face problems in terms of seedling survival owing to stress from frost, drought, sun, or pests. From an ecological point of view, delayed restoration success can result in increased nutrient elution and reduction of carbon stored in soils. To address this problem nurse crops comprising robust and fast growing tree species such as birch (Betula ssp.) or poplar (Populus ssp.) have been used to establish an overstory sheltering sensitive target tree species against weather extremes.
This project aims to utilize forest biomass provided by nurse crops to support the production of renewable energy (Energy Nurse Crops, ENCs). However, exporting additional forest biomass affects the nutrient cycles and thus may undermine the principle of sustainability. Therefore, this project will investigate and evaluate the concept of ENCs and its consequences relative to ordinary restoration methods especially for forest ecosystems sensitive to windblow such as pure black spruce stands (Picea abies) stocking on periodically wet soils.
Tree species such as birch or poplar are known to develop extensive root systems. Because ENCs reliably establish in open areas and because their roots can quickly penetrate soils, they may be able to retain much more nutrients on site than any target tree species could ever do when established under unfavorable growth conditions. Eventually the positive effects of nutrient retention and soil carbon fixation may outweigh the negative effects of nutrient export with biomass. To explore this question, field experiments quantifying nutrient elution, nutrient pools, carbon pools, biomass production, and root growth will be conducted in ENC stands of different age, site, and tree species. Introducing additional tree species such as birch or poplar may also affect forest ground vegetation composition and species abundance. A research approach addressing species diversity of forest ground vegetation will be considered in the future.

 

Supervisors: Prof. Dr. Jürgen Bauhus, PD Dr. Klaus v. Wilpert
Researcher: Hendrik Stark
Funding: Stiftung Energieforschung Baden-Württemberg, Stipendium nach dem Landesgraduiertenförderungsgesetz (LGFG)
Duration: 09/2009 bis 08/2012

 

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