Yan Peng, IGN, defends her thesis at the section of Forest, Nature and Biomass

Yan Peng defends her thesis:

Tree species effects on soil carbon stocks and tree speciesmediated effects of soil fauna on litter decomposition

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Supervisors: 
Professor Lars Vesterdal, IGN
Professor Inger Kappel Schmidt, IGN

Assessment Committee:
Professor Håkan Wallander, Department of Biology, Lund University
Associate Professor Simon Bahrndorff, Department of Chemistry and Bioscience, AAU
Associate Professor Klaus Steenberg Larsen (chair), IGN

Summary:
Soil contains a substantial part of terrestrial carbon (C) and plays an important role in the terrestrial C cycling. Tree species has been found to be of great importance for soil C stocks, and selection of appropriate tree species is an important forest management decision that may affect soil C sequestration. However, quantitative estimates of tree species effects on soil C stocks are still scarce, and how tree species may affect soil fauna communities and their effects on litter decomposition is also limited, which limited our understanding on the mechanisms of tree species effects on soil C stocks.
Through global meta-analysis, field survey, and litterbag experiments, this thesis assessed how tree species and their mycorrhizal association, namely arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM), affected soil C stocks, soil fauna communities, litter decomposition, and soil fauna effects on litter decomposition. We found that tree species is an important factor affecting soil C stocks, with lower forest floor C stock (39%), but higher mineral soil C stock (10%) under AM than ECM trees. Tree species significantly affected soil fauna communities directly and/or indirectly through regulating resource availability of litter, forest floor, and soil, with higher soil fauna biomass as well as taxonomic and functional diversity under AM than ECM tree species except for lime, which showed a pattern similar to that for AM tree species. However, tree species effects varied among different taxonomic and functional groups. Plant litter species, mycorrhizal association, litterbag mesh size, and their interactions all significantly affected litter decomposition, with higher litter decomposition rates for litter from AM than ECM tree species tor in larger mesh size litterbags with access of soil fauna. The access of meso- and macrofauna significantly enhanced litter decomposition, increasing the decomposition rate of AM and ECM tree species by 255% and 92% by mesofauna and 265% and 108% by all soil fauna, respectively, except for lime litter that showed a similar pattern with litter from AM tree species.
Our findings would be useful for informing tree species selection in forest management or afforestation aiming to sequester more atmospheric C in soils, for predicting the effects of forest management on soil fauna communities, and for better understanding the importance of plant-fauna-soil interactions following forest management or afforestation in C sequestration and climate change mitigation.

A digital version of the PhD thesis can be obtained from the PhD secretary Anne Marie Faldt anmf@ign.ku.dk