Boreal tree species affect soil organic matter composition and saprotrophic mineralization rates

Javier H Segura,Mats G Öquist,Mats B Nilsson,Jürgen Schleucher,Julie Tolu,Tobias Sparrman,Henrik Serk

doi:10.1007/s11104-019-04105-x

Javier H Segura, Mats G Öquist + Show 5 more

Open Access

https://doi.org/10.1007/s11104-019-04105-x

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Abstract

AimsTo investigate how different tree species affect the composition of SOM and its mineralization in boreal forest ecosystems.MethodsWe used pyrolysis GC–MS for molecular-level characterization of the SOM formed under five common boreal tree species at a replicated field experiment ~50years after plantation. We incubated soil samples at 4, 9, 14 and 19 °C and measured inherent CO2 production and substrate-induced respiration. We then evaluated if the saprotrophic microbial activity and its temperature sensitivity was controlled by the SOM composition.ResultsThe molecular composition of the SOM emerged as key factor influencing SOM properties in plots with different tree species. Most of the variance in the SOM content was explained by the organo-chemical composition of the SOM. More importantly, the fraction of the microbial community able to utilize the native SOM was largely controlled by the SOM organo-chemical composition. Temperature sensitivity of CO2 production (Q10) was not explained by SOM composition. However, the microbial access to different SOM pools varied with temperature.ConclusionsThese results bridge the gap between the paradigms of short-term litter and long-term SOM decomposition showing that, on an intermediate timescale (~50 years), boreal tree species affect SOM molecular composition and saprotrophic mineralization rates.

Highlights

An estimated 30% of the earth’s soil organic matter (SOM) pool of ca. 2300 Pg C is stored in soils of high-latitude ecosystems (Tarnocai et al 2009)
Most of the variance in the SOM content was explained by the organo-chemical composition of the SOM
The fraction of the microbial community able to utilize the native SOM was largely controlled by the SOM organochemical composition

Summary

Introduction

An estimated 30% of the earth’s soil organic matter (SOM) pool of ca. 2300 Pg C is stored in soils of high-latitude ecosystems (Tarnocai et al 2009). 2300 Pg C is stored in soils of high-latitude ecosystems (Tarnocai et al 2009). This mass of carbon is similar to that of CO2-C presently found in the atmosphere (Ciais et al 2014). The composition of SOM and its turnover are critical determinants of nutrient cycling, soil formation, and the net ecosystem carbon balance (Waksman 1936; Trumbore 2000; Kleber and Johnson 2010; Schmidt et al 2011). The persistence of SOM in the soil depends on a complex set of interactions between biological and physicochemical factors that control its rate of decomposition (Schmidt et al 2011)

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