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Titel |
Contrasting effects of invasive insects and fire on ecosystem water use efficiency |
VerfasserIn |
K. L. Clark, N. S. Skowronski, M. R. Gallagher, H. Renninger, K. V. R. Schäfer |
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. 23 ; Nr. 11, no. 23 (2014-12-01), S.6509-6523 |
Datensatznummer |
250117699
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Publikation (Nr.) |
copernicus.org/bg-11-6509-2014.pdf |
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Zusammenfassung |
We used eddy covariance and meteorological measurements to estimate net
ecosystem exchange of CO2 (NEE), gross ecosystem production (GEP),
evapotranspiration (Et), and ecosystem water use efficiency (WUEe;
calculated as GEP / Et during dry canopy conditions) in three upland forests
in the New Jersey Pinelands, USA, that were defoliated by gypsy moth
(Lymantria dispar L.) or burned using prescribed fire. Before disturbance, half-hourly
daytime NEE during full sunlight conditions, daily GEP, and daily WUEe
during the summer months were greater at the oak-dominated stand compared to
the mixed or pine-dominated stands. Both defoliation by gypsy moth and
prescribed burning reduced stand leaf area and nitrogen mass in foliage.
During complete defoliation in 2007 at the oak stand, NEE during full
sunlight conditions and daily GEP during the summer averaged only 14 and
35% of pre-disturbance values. Midday NEE and daily GEP then averaged
58 and 85%, and 71 and 78% of pre-defoliation values 1 and
2 years following complete defoliation, respectively. Prescribed fires
conducted in the dormant season at the mixed and pine-dominated stands
reduced NEE during full sunlight conditions and daily GEP during the
following summer to 57 and 68%, and 79 and 82% of
pre-disturbance values, respectively. Daily GEP during the summer was a
strong function of N mass in foliage at the oak and mixed stands, but a
weaker function of N in foliage at the pine-dominated stand. Ecosystem
WUEe during the summer at the oak and mixed stands during defoliation
by gypsy moth averaged 1.6 and 1.1 g C kg H2O−1, representing
60 and 46% of pre-disturbance values. In contrast, prescribed fires
at the mixed and pine-dominated stands had little effect on WUEe. Two
years following complete defoliation by gypsy moth, WUEe during the
summer averaged 2.1 g C kg H2O−1, 80% of pre-disturbance
values. WUEe was correlated with canopy N content only at the
oak-dominated stand. Overall, our results indicate that WUEe during and
following non-stand replacing disturbance is dependent on both the type and
time since disturbance. |
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