 |
| Titel |
Coarse root topology of Norway spruce (Picea abies) and its effects on slope stability |
| VerfasserIn |
Aniek Lith, Elmar Schmaltz, Thom Bogaard, Saskia Keesstra |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250138648
|
| Publikation (Nr.) |
 EGU/EGU2017-1741.pdf |
|
|
|
|
|
| Zusammenfassung |
| The structural distribution of coarse roots and its beneficial effects on soil reinforcement has
widely been assessed. However, it is still not fully understood how topological features of
coarse roots (e.g. branching patterns) are affected by slope inclination and further influence
the ability of young trees to reinforce soil. This study aims to analyse empirically the
impact of slope gradient on the topological development of coarse roots and thus to
assess its effects on soil reinforcement. We performed root system excavations on
two young Picea abies: tree A on a gently inclined plane (β ≈ 12∘) where slope
failures are not expected; tree B on a slope (β ≈ 35∘) with failure potential. The
diameter (d) of the segments between distinct root nodes (root ends, branching
locations, direction changes and attachments to stem) of coarse roots (d > 2mm) were
measured in situ. The spatial coordinates (x,y,z) of the nodes and surface were
measured on a plane raster grid, from which segment length (ls), direction and
inclination towards the surface (βr) were derived. Roots and segments were classified
into laterals (βr < 10∘), obliques (10∘ ≤ βr < 70∘) and verticals (βr ≥ 70∘),
with βr,max = 90∘. We assigned topological orders to the segments according to
developmental (DSC) and functional segment classifications (FSC), to obtain quantitative
relations between the topological order and number of segments, total and average
ls. The maximal root cohesion (cr) of each segment was assessed using material
specific tensile forces (Tr), root area ratio (RAR) and βr, assuming that a potential
slip surface would cross the root system parallel to the slope. Laterals depicted the
majority of roots (57 %) for tree A orientated rather in upslope direction (76.8
%), whereas tree B showed mostly obliques (54 %) orientated rather in downslope
direction (55.4 %). Vertical roots were scarcely observable for both trees. DSC showed
a high r2 (> 0.84) for the segments and ls. FSC showed high r2 (> 0.95) for the
number of segments and the total length. RAR values of tree B are distributed rather
upslope (76.8 % of RARtot), compared to 44.5 % of RARtot for tree A. The average
cr (0.15) of each segment of tree B was remarkably higher than of tree A (0.10),
leading to the conclusion that the slope has a strong influence on cr itself. This is
supported by comparing the distribution of cr for both trees, where tree B tends to
produce a higher cr in upslope direction (68.7 % of total cr) than tree A (37.7 %).
In contrast to our expectations, tree B shows generally a higher cr compared to
tree A, despite lower subsurface biomass. The findings indicate that the distinct
branching patterns of coarse roots might determine the distribution of the RAR
and thus lead to a higher reinforcement potential of young Picea abies on slopes. |
|
|
|
|
|
|