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| Titel |
Stemflow in low-density and hedgerow olive orchards in Portugal |
| VerfasserIn |
Pedro D. Dias, Fernanda Valente, Fernando L. Pereira, Francisco G. Abreu |
| 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 |
250108094
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| Publikation (Nr.) |
 EGU/EGU2015-7825.pdf |
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| Zusammenfassung |
| Stemflow (Sf) is responsible for a localized water and solute input to soil around tree’s trunks,
playing an important eco-hydrological role in forest and agricultural ecosystems. Sf was
monitored for seven months in 25 Olea europaea L. trees distributed in three orchards
managed in two different ways, traditional low-density and super high density hedgerow. The
orchards were located in central Portugal in the regions of Santarém (Várzea and Azóia) and
Lisboa (Tapada). Seven olive varieties were analysed: Arbequina, Galega, Picual, Maçanilha,
Cordovil, Azeiteira, Negrinha and Blanqueta. Measured Sf ranged from 7.5 to 87.2 mm
(relative to crown-projected area), corresponding to 1.2 and 16.7% of gross rainfall (Pg). To
understand better the variables that affect Sf and to be able to predict its value, linear
regression models were fitted to these data. Whenever possible, the linear models were
simplified using the backward stepwise algorithm based on the Akaike information
criterion. For each tree, multiple linear regressions were adjusted between Sf and the
duration, volume and intensity of rainfall episodes and maximum evaporation rate. In
the low-density Várzea grove the more relevant explanatory variables were the
three rainfall characteristics. In the super high density Azóia orchard only rainfall
volume and intensity were considered relevant. In the low-density Tapada’s grove all
trees had a different sub-model with Pg being the only common variable. To try
to explain differences between trees and to improve the quality of the modeling
in each orchard, another set of explanatory variables was added: canopy volume,
tree and trunk heights and trunk perimeter at the height of the first branches. The
variables present in all sub-models were rainfall volume and intensity and the tree
and trunk heights. Canopy volume and rainfall duration were also present in the
sub-models of the two low-density groves (Tapada and Várzea). The determination
coefficient (R2) of all models ranged from 0.5 to 0.76. The size of leaves was also
analysed. Although there were significant differences between varieties and between
trees of the same variety, they did not seem to affect the amount of Sf generated.
Through analysis of bark storage capacity, it was found that older trees, with rough and
thick bark, had higher trunk storage capacity and, therefore, originated less Sf. The
results confirm the need for considering the contribution of stemflow when trying to
correctly assess interception loss in olive orchards. Although the use of simple
and general statistical models may be an attractive option, their precision may be
small, making direct measurements or conceptual modelling preferable methods. |
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