 |
| Titel |
What do Boletus, Chanterelle and Co. have in common with Eco engineering? |
| VerfasserIn |
F. Graf, K. Burri, A. Böll |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020691
|
|
|
|
|
|
| Zusammenfassung |
| A major goal of eco engineering is its contribution to slope stability. The carefully selected
plant and technical construction material are an indispensable requirement but not necessarily
sufficient in view of long-term success. For that purpose, plant growth and the development
of a functional vegetation cover are essential. However, particularly under extreme climatic
and environmental conditions even pioneer plants reach their limits in bridging the gap
between their proper needs and the effective yield of the soil degraded by erosion or sliding
processes.
Besides the conventional solutions that are the application of artificial fertiliser and soil
conditioners, a competitive option is to be found in the "Kingdom of Fungi". Under natural
conditions, as good as every plant species used in eco engineering lives in a symbiotic
relationship with fungi, called mycorrhiza with Boletus and Chanterelle as two
prominent representatives. Within these partnerships, the fungi take charge of the
host’s water and nutrient supply; considerably increasing its efficiency compared to
non-mycorrhized roots. Consequently, plant growth, in particular root performance, and
survival are significantly improved as is shown in a restoration experiment on an
alpine ski slope in the Swiss mountains and has been demonstrated many times
elsewhere.
In addition to this indirect contribution to the restoration and re-stabilisation process, the
mycorrhizal fungi provide more direct functions related to the development of a stable soil
structure starting from a severely degraded soil material. The mycelia producing fungi
assemble and stabilise micro- and macro-aggregates out of smallest organic and inorganic
soil particles. The formation and stabilisation of the soil structure proceed at different spatial
scales directly by electrostatic charge, adhesive and enmeshment mechanisms. Numerous
investigations prove that, on the one hand, the sole application of mycorrhizal fungi
to loose soil material may result in an increase of aggregate stability but, on the
other hand, demonstrate its species specific dependency. Furthermore, mycorrhizal
fungi support the soil aggregate stability by serving as a distribution vector for
associated micro-organisms, mainly bacteria and archaea, some of them soil stabilising
alike.
A positive correlation was found between soil aggregate stability and dry unit weight,
based on laboratory as well as field samples. Such a correlation is known for the shear
strength parameters – particularly for the angle of internal friction Φ’ – of the Mohr-Coulomb
failure criterion on which most of the conventionally used models for soil and slope stability
calculations are based. Moreover, evidence was provided that the aggregate stability of soil at
low dry unit weight (~15.5 kN/m3) added with plants and mycorrhizal fungi corresponds to
that of untreated soil material at high dry unit weight (~19.5 kN/m3) a feature found for the
angle of internal friction Φ’ too. Conclusively, based on these relationships, effects
of plants and mycorrhizal fungi on soil stability may be interpreted as a virtual
increase in dry unit weight and a real increase in the angle of internal friction Φ’,
respectively.
The effect of plants and fungi on soil stability is, however, not restricted to withstand
erosion and sliding processes induced by water. Recent experiments in a wind tunnel reveal
the potential of this symbiosis related to wind erosion and, therefore, in view of combating
desertification. Experiments with differently dense planted soil confirmed the negative
correlation with the amount of sediment transport and health threatening fine dust (PM10)
emission. The "mycorrhiza network" including and connecting plants, soil aggregate
stability, and the angle of internal friction Φ’ is of special meaning in view of soil
stabilisation and the development of degraded soil. Carefully selected fungus-plant
combinations shorten the delicate phase of re-colonisation and the development of a
functional vegetation cover at simultaneous amelioration of the site specific conditions –
representing the essential requirements for long-term success of eco engineering measures. |
|
|
|
|
|
|