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| Titel |
Aridity and decomposition processes in complex landscapes |
| VerfasserIn |
Alessandro Ossola, Petter Nyman |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250107344
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| Publikation (Nr.) |
 EGU/EGU2015-7042.pdf |
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| Zusammenfassung |
| Decomposition of organic matter is a key biogeochemical process contributing to nutrient
cycles, carbon fluxes and soil development. The activity of decomposers depends on
microclimate, with temperature and rainfall being major drivers. In complex terrain the
fine-scale variation in microclimate (and hence water availability) as a result of slope
orientation is caused by differences in incoming radiation and surface temperature. Aridity,
measured as the long-term balance between net radiation and rainfall, is a metric that can be
used to represent variations in water availability within the landscape. Since aridity metrics
can be obtained at fine spatial scales, they could theoretically be used to investigate how
decomposition processes vary across complex landscapes. In this study, four research sites
were selected in tall open sclerophyll forest along a aridity gradient (Budyko dryness index
ranging from 1.56 –2.22) where microclimate, litter moisture and soil moisture
were monitored continuously for one year. Litter bags were packed to estimate
decomposition rates (k) using leaves of a tree species not present in the study area
(Eucalyptus globulus) in order to avoid home-field advantage effects. Litter mass loss
was measured to assess the activity of macro-decomposers (6mm litter bag mesh
size), meso-decomposers (1 mm mesh), microbes above-ground (0.2 mm mesh) and
microbes below-ground (2 cm depth, 0.2 mm mesh). Four replicates for each set of
bags were installed at each site and bags were collected at 1, 2, 4, 7 and 12 months
since installation. We first tested whether differences in microclimate due to slope
orientation have significant effects on decomposition processes. Then the dryness
index was related to decomposition rates to evaluate if small-scale variation in
decomposition can be predicted using readily available information on rainfall and
radiation. Decomposition rates (k), calculated fitting single pool negative exponential
models, generally decreased with increasing aridity with k going from 0.0025 day-1
on equatorial (dry) facing slopes to 0.0040 day-1 on polar (wet) facing slopes.
However, differences in temperature as a result of morning vs afternoon sun on east
and west aspects, respectively, (not captured in the aridity metric) resulted in poor
prediction of decomposition for the sites located in the intermediate aridity range.
Overall the results highlight that relatively small differences in microclimate due to
slope orientation can have large effects on decomposition. Future research will
aim to refine the aridity metric to better resolve small scale variation in surface
temperature which is important when up-scaling decomposition processes to landscapes. |
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