 |
| Titel |
Charcoal and stable soil organic matter indicate fire frequency, past vegetation and climate in volcanic soils (Mt. Etna, Sicily) |
| VerfasserIn |
Markus Egli, Giovanni Mastrolonardo, Ruedi Seiler, Giacomo Certini, Salvatore Raimondi, Filippo Favilli, Paolo Cherubini |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250046725
|
|
|
|
|
|
| Zusammenfassung |
| A powerful tool to reconstruct past environments and climate is the extraction,
identification and radiocarbon dating of charcoal fragments buried in soils. Charcoal
fragments are particularly useful to reconstruct past vegetation because the level of
preservation is often good enough to determine the tree genus (and in some cases the
species) level. All forest ecosystems have the potential to burn as a result of climate
or human-induced fires. Forest fires are ultimately coupled to climate and are a
not negligible factor of pedogenesis in the Mediterranean areas, where they occur
frequently. Furthermore, soil organic matter (SOM) is prone to changes due to forest
fires, both in terms of quantity and quality. A soil sequence along an elevational
gradient ranging from Mediterranean to subalpine climate zones on slopes of the
Etna region (Sicily, southern Italy) was investigated in respect of soil organic C
and charcoal. The amount of charcoal and the identification of charred species
give an indication about fire frequency and vegetation changes that have occurred
in the past. Furthermore, the distribution into labile and stable organic fraction
provide insight into the stabilisation and turn-over mechanisms of SOM. The stable
organic matter fraction is intended here as the residue of a treatment of the soil
material using H2O2. The soils along the altitudinal sequence were variations of Vitric
Andosols that developed on a trachy-basaltic (alkali mugearite) lava flow having an
age of about 10-15 ky. Two main vegetation systems dominate the studied sites:
at the lower sites it is mainly maquis vegetation and at the higher elevated sites
pine forest. Charcoals were older at higher elevation with ages of up to 1500 y
calBP. The vegetation type did not change much over the last > 1000 years, as all
charcoal pieces were identified as Pinus nigra. Charred material at the lower sites
could be identified as particles of deciduous shrubs, Quercus, Castanea sativa,
Lonicera implexa and Cytisus sp. with mostly a modern 14C age up to about 300 y
calBP. A similar finding is obtained for the stable SOM. In fact, very high ages
were found at the highest elevations, where the stable organic matter fraction had
an age of up to 8.2 ky – an age that is quite close to the start of soil formation.
At the lower sites, frequent bush fires more often destroyed a part of the stable
fraction. In the subsoil of these sites, the stable SOM fraction had an age ranging
from a few decades to max. 1 ky. Furthermore, SOM stocks and the amount of
labile organic matter increased with decreasing altitude. The soils consequently
have recorded the signal of fire frequency and climatic effects: with decreasing
altitude and therefore with a warmer climate, fire frequency, SOM abundance and the
amount of labile SOM increased. At the lower sites, charcoal particles predominantly
reflect the more recent vegetation probably because the repeated fires hindered here
their preservation. Fire appears to also negatively affect the stable SOM fraction
at lower altitudes. Our findings suggest that the high fire frequency is a powerful
rejuvenating factor for soil organic matter, removing part of the SOM and promoting plant
recolonisation. The fire frequency and intensity is, however, still moderate enough as the
organic matter pool even at the lowest is still high and consequently not depleted. |
|
|
|
|
|
|