Mayer, Mathias;
Sandén, Hans;
Rewald, Boris;
Godbold, Douglas L.;
Katzensteiner, Klaus
Increase in heterotrophic soil respiration by temperature drives decline in soil organic carbon stocks after forest windthrow in a mountainous ecosystem
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Media type:
E-Article
Title:
Increase in heterotrophic soil respiration by temperature drives decline in soil organic carbon stocks after forest windthrow in a mountainous ecosystem
Contributor:
Mayer, Mathias;
Sandén, Hans;
Rewald, Boris;
Godbold, Douglas L.;
Katzensteiner, Klaus
Description:
<sec>
<label>1.</label>
<p>Intensifying forest disturbance regimes are likely to impact heavily on future carbon (C) budgets of forest ecosystems. Our understanding of how forest disturbance affects the sources of soil CO₂ efflux (<italic>F</italic>
<sub>s</sub>) is, however, poor. This may lead to uncertainties over future C sink estimates of forest ecosystems and associated feedbacks to the atmosphere.</p>
</sec>
<sec>
<label>2.</label>
<p>We investigated the impact of forest windthrow on the heterotrophic and autotrophic sources of <italic>F</italic>
<sub>s</sub>, underlying biotic and abiotic drivers (i.e. plant community composition, soil organic matter (SOM) properties and soil microclimate), and consequences for soil organic carbon (SOC) stocks <italic>in situ</italic> along a disturbance chronosequence in the European Alps. This chronosequence facilitated the study of temporal changes in the above parameters between the third and sixth years after windthrow.</p>
</sec>
<sec>
<label>3.</label>
<p>Along the chronosequence, structural equation modelling revealed that soil temperature, soil moisture, SOM properties and plant community composition explained 90% of the variation in <italic>F</italic>
<sub>s</sub>. While no direct interactions among plants and SOM properties could be determined, plants significantly affected soil microclimate. Windthrow had no obvious effect on <italic>F</italic>
<sub>s</sub> because reduced autotrophic soil respiration (<italic>R</italic>ₐ) was offset by a ~60% increase in heterotrophic soil respiration (<italic>R</italic>
<sub>h</sub>), principally due to increased soil temperatures. <italic>R</italic>ₐ after windthrow was dominated by grasses and herbs rather than trees; however, a high abundance of ectomycorrhizal fungi suggests an important indirect tree contribution to post-windthrow <italic>R</italic>ₐ. SOC stocks significantly declined over the post-windthrow period.</p>
</sec>
<sec>
<label>4.</label>
<p>Our results show that <italic>R</italic>
<sub>h</sub> was by far the dominant source of <italic>F</italic>
<sub>s</sub> after forest windthrow. As C losses from <italic>R</italic>
<sub>h</sub> and SOC stocks were in the same order of magnitude, this study demonstrates that post-windthrow declines in SOC stocks were mainly driven by a temperature-related increase in <italic>R</italic>
<sub>h</sub>.</p>
</sec>