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| Titel |
The effect of drought and interspecific interactions on depth of water uptake in deep- and shallow-rooting grassland species as determined by δ18O natural abundance |
| VerfasserIn |
N. J. Hoekstra, J. A. Finn, D. Hofer, A. Lüscher |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 16 ; Nr. 11, no. 16 (2014-08-25), S.4493-4506 |
| Datensatznummer |
250117562
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| Publikation (Nr.) |
 copernicus.org/bg-11-4493-2014.pdf |
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| Zusammenfassung |
Increased incidence of drought, as predicted under climate change,
has the potential to negatively affect grassland production. Compared to
monocultures, vertical belowground niche complementarity between shallow-
and deep-rooting species may be an important mechanism resulting in higher
yields and higher resistance to drought in grassland mixtures. However, very
little is known about the belowground responses in grassland systems and
increased insight into these processes may yield important information both
to predict the effect of future climate change and better design
agricultural systems to cope with this.
This study assessed the effect of a 9-week experimental summer drought on
the depth of water uptake of two shallow-rooting species (Lolium perenne L. and
Trifolium repens L.) and two deep-rooting species (Cichorium intybus L. and Trifolium pratense L.) in grassland monocultures and
four-species mixtures by using the natural abundance δ18O
isotope method. We tested the following three hypotheses: (1) drought results in a
shift of water uptake to deeper soil layers, (2) deep-rooting species take up
a higher proportion of water from deeper soil layers relative to
shallow-rooting species, and (3) as a result of interspecific interactions in
mixtures, the water uptake of shallow-rooting species becomes shallower when
grown together with deep-rooting species and vice versa, resulting in
reduced niche overlap.
The natural abundance δ18O technique provided novel insights
into the depth of water uptake of deep- and shallow- rooting grassland
species and revealed large shifts in depth of water uptake in response to
drought and interspecific interactions.
Compared to control conditions, drought reduced the proportional water
uptake from 0–10 cm soil depth (PCWU0–10) of L. perenne, T. repens and C. intybus in monocultures by
on average 54%. In contrast, the PCWU0–10 of T. pratense in monoculture
increased by 44%, and only when grown in mixture did the PCWU0–10
of T. pratense decrease under drought conditions. In line with hypothesis (2), in
monoculture, the PCWU0–10 of shallow-rooting species L. perenne and T. repens was 0.53
averaged over the two drought treatments, compared to 0.16 for the
deep-rooting C. intybus. Surprisingly, in monoculture, water uptake by T. pratense was shallower
than for the shallow-rooting species (PCWU0–10 = 0.68).
Interspecific interactions in mixtures resulted in a shift in the depth of
water uptake by the different species. As hypothesised, the shallow-rooting
species L. perenne and T. repens tended to become shallower, and the deep-rooting T. pratense made a
dramatic shift to deeper soil layers (reduction in PCWU0–10 of 58%
on average) in mixture compared to monoculture. However, these shifts did
not result in a reduction in the proportional similarity of the proportional
water uptake from different soil depth intervals (niche overlap) in mixtures
compared to monocultures.
There was no clear link between interspecific differences in depth of water
uptake and the reduction of biomass production under drought compared to
control conditions (drought resistance). Cichorium intybus, the species with water uptake
from the deepest soil layers was one of the species most affected by
drought. Interestingly, T. pratense, which was least affected by drought, also had the
greatest plasticity in depth of water uptake. This suggests that there may
be an indirect effect of rooting depth on drought resistance, as it
determines the potential plasticity in the depth of water uptake. |
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