Year: 2009
Type: dissertation
Abstract: Decomposition of soil organic matter connects the global carbon (C) cycle with the turnover of nitrogen (N), but exactly how the availability of N affects the soil C turnover is unclear. In boreal forest soils, fungi are essential to litter decomposition. Most litter decomposing fungi form large mycelia and have a well developed capacity to translocate resources, such as carbohydrates and nutrients, within their mycelia. Translocation by litter fungi may enable efficient utilization of spatially separated substrates differing in respect to their quality and thus have a major influence on decomposition and nutrient dynamics. In order to isolate the different mechanisms controlling C and N turnover by litter decomposing fungi, controlled laboratory studies were conducted with the known, common litter fungi Marasmius androsaceus and Mycena epipterygia. Furthermore, some litter fungi with unknown functional capability were tested for their ability to decompose pine needles and potential effects of interspecific interactions for C and N dynamics were also assessed. The low initial N content of recently abscised pine needles limited the catabolism as well as growth and needle decomposition by both M. androsaceus and M. epipterygia. Accordingly, when colonizing new needle litter both fungi translocated assimilated N into the needles leading to a net gain in the total N pool. This way, both fungi were able to increase their growth in the new substrate. In addition, both fungi translocated C to low C:N ratio substrates, thereby overcoming local C deficiency and subsequently restricted mineralization of N. When able to connect substrates of different quality, both fungi increased their efficiency by allocating a larger proportion of assimilated C into biomass production, thereby reducing the release of CO₂. Interspecific antagonistic interactions prevented mycelial linking of substrates colonized by different species, and thereby hampered translocation. This thesis demonstrates that the capacity of litter decomposing fungi to translocate resources within their mycelia may have a decisive influence on the C and N cycle in boreal forests.
Author: Johanna Boberg
Language: English
Subfield: Soil Science
Domain: Life Sciences
SDG: Life on land
Open Access status: green
OpenAlex ID: W52199212