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Edaphic, structural and physiological contrasts across Amazon Basin forest–savanna ecotones suggest a role for potassium as a key modulator of tropical woody vegetation structure and function

Lloyd, J.; Domingues, T. F.; Schrodt, F.; Ishida, F. Y.; Feldpausch, T. R.; Saiz, G.; Quesada, C. A.; Schwarz, M.; Torello-Raventos, M.; Gilpin, M.; Marimon, B. S.; Marimon-Junior, B. H.; Ratter, J. A.; Grace, J.; Nardoto, G. B.; Veenendaal, E.; Arroyo, L.; Villarroel, D.; Killeen, T. J.; Steininger, M.; Phillips, O. L.

Authors

J. Lloyd

T. F. Domingues

F. Y. Ishida

T. R. Feldpausch

G. Saiz

C. A. Quesada

M. Schwarz

M. Torello-Raventos

M. Gilpin

B. S. Marimon

B. H. Marimon-Junior

J. A. Ratter

J. Grace

G. B. Nardoto

E. Veenendaal

L. Arroyo

D. Villarroel

T. J. Killeen

M. Steininger

O. L. Phillips



Abstract

Sampling along a precipitation gradient in tropical South America extending from ca. 0.8 to 2.0 m a−1, savanna soils had consistently lower exchangeable cation concentrations and higher C / N ratios than nearby forest plots. These soil differences were also reflected in canopy averaged leaf traits with savanna trees typically having higher leaf mass per unit area but lower mass-based nitrogen (Nm) and potassium (Km). Both Nm and Km also increased with declining mean annual precipitation (PA), but most area-based leaf traits such as leaf photosynthetic capacity showed no systematic variation with PA or vegetation type. Despite this invariance, when taken in conjunction with other measures such as mean canopy height, area-based soil exchangeable potassium content, [K]sa, proved to be an excellent predictor of several photosynthetic properties (including 13C isotope discrimination). Moreover, when considered in a multivariate context
with PA and soil plant available water storage capacity (θP) as covariates, [K]sa also proved to be an excellent predictor of stand-level canopy area, providing drastically improved fits as compared to models considering just PA and/or θP. Neither calcium, nor magnesium, nor soil pH could substitute for potassium when tested as alternative model predictors (1AIC > 10). Nor for any model could simple soil texture metrics such as sand or clay content substitute for either [K]sa or θP. Taken in conjunction with recent work in Africa and the forests of the Amazon Basin, this suggests –in combination with some newly conceptualised interacting effects of PA and θP also presented here – a critical role for potassium as a modulator of tropical vegetation structure and function.

Journal Article Type Article
Publication Date Nov 18, 2015
Journal Biogeosciences
Print ISSN 1726-4170
Electronic ISSN 1726-4189
Publisher European Geosciences Union
Peer Reviewed Peer Reviewed
Volume 12
Issue 22
Pages 6529-6571
APA6 Citation Lloyd, J., Domingues, T. F., Schrodt, F., Ishida, F. Y., Feldpausch, T. R., Saiz, G., …Phillips, O. L. (2015). Edaphic, structural and physiological contrasts across Amazon Basin forest–savanna ecotones suggest a role for potassium as a key modulator of tropical woody vegetation structure and function. Biogeosciences, 12(22), 6529-6571. https://doi.org/10.5194/bg-12-6529-2015
DOI https://doi.org/10.5194/bg-12-6529-2015
Keywords Earth-Surface Processes; Ecology, Evolution, Behavior and Systematics
Publisher URL https://www.biogeosciences.net/12/6529/2015/

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Edaphic, structural and physiological contrasts across Amazon Basin forest–savanna ecotones suggest a role for potassium as a key modulator of tropical woody vegetation structure and function (3.5 Mb)
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