Case Study 1
The Nitrogen Cycle in Taiga Ecosystems
Taiga ecosystems are characterized by low nitrogen availability. In his doctoral thesis, biologist Róbert Blaško investigated the development of the nitrogen cycle in boreal forests.
Many taiga trees have nitrogen fixing bacteria in their root nodules, such as the Frankia actinobacteria. These turn nitrogen from the air into nitrates the plant can use.
Despite this, Blaško found that, in his study areas in Sweden, nitrogen availability declines with ecosystem age. For example, he noticed a 20% decline in percentage of nitrogen in conifer needles when comparing a 150 and 560 year old taiga forest.
He suggested this may be due to changes in the microbial community. For example, plants more prevalent in older ecosystems may have different nitrogen fixing bacteria that provide less nitrates, or abiotic factors may arise or increase that limit nitrogen fixation.
