Quantification and drivers for belowground carbon input in boreal forest

Ectomycorrhizal (EcM) fungi live in symbiosis with many tree species and its biomass is reported to equal with fine root biomass in boreal forests. Its importance in carbon (C) cycling in forest ecosystems is highly recognized but the poor knowledge of EcM mycelia turnover leads to a great gap in quantifying belowground C inputs. Commonly used sequential mycelial ingrowth mesh-bags ignore the continuous growth and death of mycelia in the field. Instead, we will use an advanced scanner method to visually detect the turnover (lifespan) of EcM mycelia and fine roots based on daily capture of images in forests predominated by the Scots pine in different climates. We will connect the observed dynamics with the environmental factors and the status of the host tree. This method has potential to be outbreaking in quantifying the belowground C inputs, which are urgently needed in order to quantify for soil C sequestration.

The project has detected temperature and moisture effects to daily fine root elongation rate of Scots pine by using a novel flatbed scanner method. The project had found the increasing temperature positively promote the fine root growth, but the moisture deficiency could lead to various effects to the root growth due to the soil moisture heterogeneity of different scanner locations. The EcM mycelia production in the soil was found to have positive correlation with stand basal area, site fertility and thickness of the organic layer in boreal forests, which means the higher density of trees, more fertile site and thicker humus layer could lead to a higher EcM production. The project was successfully performed and published two first-author peer-reviewed publications, several ao-authored papers and my doctoral dissertation. In the near future, I will use the previous published root growth data from Southern Finland (Hyytiälä) compared with that from the Northern Finland (Värriö) and detect how the environmental factors affect the root growth in different regions.