Soil CO<sub>2</sub> efflux in an old-growth southern conifer forest (<i>Agathis australis</i>) – magnitude, components and controls
Total soil CO<sub>2</sub> efflux and its component fluxes, autotrophic and heterotrophic respiration, were measured in a native forest in northern Aotearoa–New Zealand. The forest is dominated by <i>Agathis australis</i> (kauri) and is on an acidic, clay rich soil. Soil CO<...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-08-01
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| Series: | SOIL |
| Online Access: | http://www.soil-journal.net/2/403/2016/soil-2-403-2016.pdf |
| Summary: | Total soil CO<sub>2</sub> efflux and its component fluxes, autotrophic and
heterotrophic respiration, were measured in a native forest in northern
Aotearoa–New Zealand. The forest is dominated by <i>Agathis australis</i> (kauri) and is on an
acidic, clay rich soil. Soil CO<sub>2</sub> efflux, volumetric soil water content
and soil temperature were measured bi-weekly to monthly at 72 sampling
points over 18 months. Trenching and regression analysis was used to
partition total soil CO<sub>2</sub> efflux into heterotrophic and autotrophic
respiration. The effect of tree structure was investigated by calculating an
index of local contribution (<i>I</i><sub>c</sub>, based on tree size and distance to the
measurement location) followed by correlation analysis between <i>I</i><sub>c</sub> and
total soil CO<sub>2</sub> efflux, root biomass, litterfall and soil characteristics. The
measured mean total soil CO<sub>2</sub> efflux was 3.47 µmol m<sup>−2</sup> s<sup>−1</sup>.
Autotrophic respiration accounted for 25 % (trenching) or 28 %
(regression analysis) of total soil CO<sub>2</sub> efflux. Using uni- and
bivariate models showed that soil temperature was a poor predictor of the
temporal variation in total soil CO<sub>2</sub> efflux (< 20 %). In
contrast, a stronger temperature sensitivity was found for heterotrophic
respiration (around 47 %). We found significant positive relationships
between kauri tree size (<i>I</i><sub>c</sub>) and total soil CO<sub>2</sub> efflux, root
biomass and mineral soil CN ratio within 5–6 m of the sampling points. Using
multiple regression analysis revealed that 97 % of the spatial variability
in total soil CO<sub>2</sub> efflux in this kauri-dominated stand was explained by
root biomass and soil temperature. Our findings suggest that biotic factors
such as tree structure should be investigated in soil carbon related studies. |
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| ISSN: | 2199-3971 2199-398X |