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| Titel |
Root profile in Multi-layered Dehesas: an approach to plant-to-plant Interaction |
| VerfasserIn |
V. Rolo, G. Moreno |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250031428
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| Zusammenfassung |
| Assessing plant-to-plant relationship is a key issue in agroforestry systems. Due to the sessile
feature of plants most of these interactions take place within a restricted space, so
characterizing the zone where the plant alters its environment is important to find overlapping
areas where the facilitation or competition could occur. Main part of plan-to-plant
interactions in the dehesa are located at belowground level, thus the main limited
resources in Mediterranean ecosystems are soil nutrient and water. Hence a better
knowledge of rooting plant profile can be useful to understand the functioning of the
dehesa.
The Iberian dehesa has always been considered as a silvopastoral system where, at least,
two strata of vegetation coexist: native grasses and trees. However the dehesa is also a diverse
system where cropland and encroached territories have been systematically combined, more
or less periodically, with native pasture in order to obtain agricultural, pastoral and forestry
outputs. These multipurpose mosaic-type systems generate several scenarios where the plant
influence zone may be overlapped and the interaction, competition or facilitation, between
plants can play an important role in the ecosystem functioning in terms of productivity and
stability.
In the present study our aim was to characterize the rooting profile of multi-layered
dehesas in order to understand the competitive, and/or facilitative, relationships within the
different plant strata. The root profile of Quercus ilex subsp. ballota, Cistus ladanifer,
Retama spaherocarpa and natural grasses was studied. So 48 trenches, up to 2
meters deep, were excavated in 4 different environments: (i) grass; (ii) tree-grass;
(iii) tree-shrub and (iv) tree-shrub-grass (12 trenches in each environment). The
study was carried out in 4 dehesas, 2 encroached with C. ladanifer and 2 with R.
spaherocarpa.
In every trench soil samples were taken each 20 cm. Subsequently, all samples were
sieved using different
mesh size filters in order to avoid fine root loosing. Different plant roots were
separated visually. Q. ilex roots were identified by their black cork, pasture roots were
white, C. ladanifer roots were dark red and R. spaherocarpa roots were yellow
clear. Besides, all them exhibited a different texture. Weight, length, surface and
average diameter were measured in each root sample using the WinRHIZOpro
program.
The results showed a clear rooting pattern, high root density in the first soil layers
decreasing in depth, in all the plant strata studied. The coexistence of, at least, two plant
stratas modified most of the rooting profiles. In this way, natural grasses growing alone kept
90% of root density in the first 30 cm. In R. sphaerocarpa dehesas pasture reached up to 170
cm although the root density decreased much faster than in C. ladanifer dehesas where
pasture had a higher density in the overall profile, but reaching a much lower depth. The
introduction of shrubs lowered highly the pasture root density. This effect was higher
growing with C. ladanifer than with R. sphaerocarpa, which slightly modified
the pasture rooting profile. The effect of trees in the pasture root system was less
clear.
Trees growing alone stored 70 % of their root density in the first 30 cm. The tree root
system reached the deepest soil layer explored in all the profiles. The introduction of shrub
reduced highly the tree root density in the first soil layer. This effect was higher in
presence of C. ladanifer whose influence reduced 40 % of tree root density in the first
soil layer; nevertheless tree root density increased in deep layers when growing
with C. ladanifer while it decreased throughout the profile when growing with R.
sphaerocarpa.
R. sphaerocarpa root system stored less root density in the first soil layer than C.
ladanifer, reaching up to 190 cm depth. The influence of the tree increased a 20% the R.
sphaerocarpa root density in the first soil layers; however the rest of the profile was highly
overlapped. The C. ladanifer root density decreased much faster growing alone than growing
with tree although the overall profile of C. ladanifer did not differ significantly under the
influence of the tree.
We can conclude that root traits of different plants in multi-layered Dehesa systems are
modified in interacting plant-to-plant scenarios. The introduction of shrubs as a new
competitive element for soil nutrient and water can be understood as a new hazard for tree
functioning. Nevertheless the different exploration of soil layers due to a deeper root profile
of trees could avoid the impoverishment in their nutritional and water state. Although further
studies will be needed. |
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