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| Titel |
Trees influence preferencial flow and water uptake in tropical savanna |
| VerfasserIn |
Laura Benegas, Aida Bargues-Tobella, Niles Hasselquist, Anders Malmer, Ulrik Ilstedt |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250137611
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| Publikation (Nr.) |
 EGU/EGU2017-383.pdf |
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| Zusammenfassung |
| To address potential competition between trees and grasses for soil water, and to disentangle
the main process responsible for local soil water dynamics in pasture ecosystems, we
conducted a study of the soil water content and water source partitioning of grasses and trees
within a pasture in the Copan River catchment, Honduras. We used differences in the 2H/1H
(δD) isotopic signature of soil water (δSW) and the local meteoric water line (LMWL;
δLMWL) as a relative index of evaporation, following a recent model proposed
by Hasselquist et al (under review). The model uses Lc-excess calculated as the
absolute value of the difference between measured δD and that predicted by the
local meteoric water line (lc-excess = ¦δDM – δDP¦). Lc-excess values close to
zero indicate little difference between soil water samples and local precipitation,
whereas larger values indicate a greater degree of evaporation .()...(adapted from
Landwehr and Coplen, 2006). From the relation between Lc-excess and SWC,
we can tease apart different processes by which trees influence local soil water
dynamics, where one such processes indicate that if preferential flow, i.e quick flows
through macropores that by-pass the soil matrix, is the main pathway for water
movement in the soil, then the Lc-excess values of soil water at deeper depths will be
closer to zero than those of the surface soil, whereas relatively higher Lc-excess
values would indicate increasing dominance of matrix flow. We found that soil
underneath trees was wetter than underneath grasses at the dry season and we can
relate this with a lack of clear relationship between Lc-excess and SWC and with
the tree´s apparent shift to groundwater sources for root uptake especially in the
dry season. Due to the positive correlation between Lc-excess and SWC under
trees and due to the lower Lc-excess values found at subsoil below trees during
the dry season, we can infer that preferential flow is also facilitated by the trees
enhancing its contribution to groundwater recharge. The possible water losses via
interception linked with trees on the soil water dynamic was counterbalanced by
the positive contribution of trees to preferential flow and groundwater recharge. |
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