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| Titel |
Responses of leaf traits to climatic gradients: adaptive variation versus compositional shifts |
| VerfasserIn |
T.-T. Meng, H. Wang, S. P. Harrison, I. C. Prentice, J. Ni, G. Wang |
| 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 ; 12, no. 18 ; Nr. 12, no. 18 (2015-09-17), S.5339-5352 |
| Datensatznummer |
250118092
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| Publikation (Nr.) |
 copernicus.org/bg-12-5339-2015.pdf |
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| Zusammenfassung |
Dynamic global vegetation models (DGVMs) typically rely on plant functional
types (PFTs), which are assigned distinct environmental tolerances and
replace one another progressively along environmental gradients. Fixed
values of traits are assigned to each PFT; modelled trait variation along
gradients is thus driven by PFT replacement. But empirical studies have
revealed "universal" scaling relationships (quantitative trait variations
with climate that are similar within and between species, PFTs and
communities); and continuous, adaptive trait variation has been proposed to
replace PFTs as the basis for next-generation DGVMs.
Here we analyse quantitative leaf-trait variation on long temperature and
moisture gradients in China with a view to understanding the relative
importance of PFT replacement vs. continuous adaptive variation within PFTs.
Leaf area (LA), specific leaf area (SLA), leaf dry matter content (LDMC) and
nitrogen content of dry matter were measured on all species at 80 sites
ranging from temperate to tropical climates and from dense forests to
deserts. Chlorophyll fluorescence traits and carbon, phosphorus and
potassium contents were measured at 47 sites. Generalized linear models were
used to relate log-transformed trait values to growing-season temperature
and moisture indices, with or without PFT identity as a predictor, and to
test for differences in trait responses among PFTs.
Continuous trait variation was found to be ubiquitous. Responses to moisture
availability were generally similar within and between PFTs, but biophysical
traits (LA, SLA and LDMC) of forbs and grasses responded differently from
woody plants. SLA and LDMC responses to temperature were dominated by the
prevalence of evergreen PFTs with thick, dense leaves at the warm end of the
gradient. Nutrient (N, P and K) responses to climate gradients were
generally similar within all PFTs. Area-based nutrients generally declined
with moisture; Narea and Karea declined with temperature, but
Parea increased with temperature.
Although the adaptive nature of many of these trait-climate relationships is
understood qualitatively, a key challenge for modelling is to predict them
quantitatively. Models must take into account that community-level responses
to climatic gradients can be influenced by shifts in PFT composition, such
as the replacement of deciduous by evergreen trees, which may run either
parallel or counter to trait variation within PFTs. The importance of PFT
shifts varies among traits, being important for biophysical traits but less
so for physiological and chemical traits. Finally, models should take
account of the diversity of trait values that is found in all sites and
PFTs, representing the "pool" of variation that is locally available for
the natural adaptation of ecosystem function to environmental change. |
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