• What was the problem/issue being addressed?¨
Challenges in manipulating plant-soil interactions for enhanced C sequestration and N retention arise from the huge species and life strategy diversity of both soil biota and plants, which have precluded their comprehensive characterization and limited our understanding of their ecological functions. The present research was carried out within a unique common garden experiment with monoculture stands of six common European tree species; the broadleaves beech (Fagus sylvatica L.), pedunculate oak (Quercus robur L.), lime (Tilia cordata L.), sycamore maple (Acer pseudoplatanus L.) and ash (Fraxinus excelsior L.) and the conifer Norway spruce (Picea abies (L.) Karst.). The research project focused on effects of common European trees on processes underlying soil C and N fluxes as well as on diversity and abundance of soil biota and their potential role in C and N cycling. The project adapted novel techniques such as next generation sequencing methods with modern analytical methods such as PLFA or enzyme activity to explain complex processes and mechanisms associated with C and N fluxes in soil. Results obtained from this research will contribute to bridge gaps in ecological theory in term of ecosystem functions and services.
• Why is it important for society?
One of the greatest challenges of the 21st century is to mitigate global climate changes caused by increasing emissions of greenhouse gases. Since soils constitute a larger carbon (C) pool than the vegetation and atmosphere together an important strategy could be to sequester more C in soils. Plant-soil interactions play an important role for ecosystem services such as C sequestration and N retention in soil and such interactions receive increasing attention among scientists and policymakers. Novel techniques such as next generation sequencing methods in combination with analysis of C stock patterns under different tree species present an opportunity to highlight complex processes and mechanisms which underlie C and N fluxes in soil. Novel research has highlighted the role of soil microbial diversity for C and N fluxes. However, a specific role of various members of the soil community remains unknown. In my project, I focused on diversity and structure of various soil biota (bacteria, fungi and fauna) and the role for processes involved in C and N cycling.
• What were the overall objectives?
The AFOREST project aimed to (1) explore litter mediated effects of common European tree species on soil physico-chemical properties as proxy of C and N turnover in soil; (2) characterize effects of tree species on community structure and composition of soil biota; (3) evaluate the impact of common European tree species on metabolic diversity and structure and composition of functional genes related to C and N turnover and (4) synthesize the role of soil biota for C and N turnover in soils.
• What are the conclusions?
Our results revealed higher diversity of soil bacteria and fungi in soil planted by ash, maple and lime. I also found higher bacterial growth in soils planted by ash, maple and lime while soils planted by beech, oak and spruce showed higher fungal growth. In addition, I discovered higher metabolic activity in soils planted with ash, maple lime and oak, while beech and spruce showed lower metabolic activity. There were also differences in abundance and density of soil fauna. For example, I found higher relative abundance of phylum Annelida in soils planted with beech, oak and spruce while soil planted with ash, maple and lime showed higher relative abundance of phylum Arthropoda. Finally, I found a link between litter chemistry, soil physico-chemical soil properties and relative abundance and biomass of soil biota.
