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| Titel |
Differential effects of extreme drought on production and respiration: synthesis and modeling analysis |
| VerfasserIn |
Z. Shi, M. L. Thomey, W. Mowll, M. Litvak, N. A. Brunsell, S. L. Collins, W. T. Pockman, M. D. Smith, A. K. Knapp, Y. Luo |
| 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. 3 ; Nr. 11, no. 3 (2014-02-04), S.621-633 |
| Datensatznummer |
250117187
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| Publikation (Nr.) |
 copernicus.org/bg-11-621-2014.pdf |
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| Zusammenfassung |
| Extremes in climate may severely impact ecosystem structure and function,
with both the magnitude and rate of response differing among ecosystem types
and processes. We conducted a modeling analysis of the effects of extreme
drought on two key ecosystem processes, production and respiration, and, to
provide a broader context, we complemented this with a synthesis of published
results that cover a wide variety of ecosystems. The synthesis indicated that across a
broad range of biomes, gross primary production (GPP) was generally more
sensitive to extreme drought (defined as proportional reduction relative to
average rainfall periods) than was ecosystem respiration (ER). Furthermore,
this differential sensitivity between production and respiration increased as
drought severity increased; it occurred only in grassland ecosystems, and not
in evergreen needle-leaf and broad-leaf forests or woody savannahs. The
modeling analysis was designed to enable a better understanding of the mechanisms underlying
this pattern, and focused on four grassland sites arrayed across the Great
Plains, USA. Model results consistently showed that net primary productivity
(NPP) was reduced more than heterotrophic respiration (Rh) by
extreme drought (i.e., 67% reduction in annual ambient rainfall) at all
four study sites. The sensitivity of NPP to drought was directly attributable
to rainfall amount, whereas the sensitivity of Rh to drought was
driven by soil drying, reduced carbon (C) input and a drought-induced
reduction in soil C content – a much slower process. However, differences in
reductions in NPP and Rh diminished as extreme drought continued,
due to a gradual decline in the soil C pool leading to further reductions in
Rh. We also varied the way in which drought was imposed in the
modeling analysis; it was either imposed by simulating reductions in rainfall event size (ESR) or by
reducing rainfall event number (REN). Modeled NPP and Rh
decreased more by ESR than REN at the two relatively mesic sites but less so
at the two xeric sites. Our findings suggest that responses of production and
respiration differ in magnitude, occur on different timescales, and are
affected by different mechanisms under extreme, prolonged drought. |
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