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Wittich, B.; Horna, V.; Homeier, J. & Leuschner, C. (2012): Altitudinal decrease in photosynthetic capacity in tropical trees: A case study from Ecuador and a pantropical literature analysis. Ecosystems 15, 958-973
DOI: http://dx.doi.org/10.1007/s10021-012-9556-9.

Resource Description

Title: Altitudinal decrease in photosynthetic capacity in tropical trees: A case study from Ecuador and a pantropical literature analysis
FOR816dw ID: 1116
Publication Date: 2012-08-15
License and Usage Rights: http://www.tropicalmountainforest.org/dataagreement.do
Resource Owner(s):
Individual: Bärbel Wittich
Contact:
Individual: Viviana Horna
Contact:
Individual: Jürgen Homeier
Contact:
Individual: Christoph Leuschner
Contact:
Abstract:
In tropical mountains, trees are the dominant life
form from sea level to above 4,000-m altitude under
highly variable thermal conditions (range of
mean annual temperatures: <8 to >28C). How
light-saturated net photosynthesis of tropical trees
adapts to variation in temperature, atmospheric
CO2 concentration, and further environmental
factors, that change along elevation gradients,
is not precisely known. With gas exchange
measurements in mature trees, we determined
light-saturated net photosynthesis at ambient
temperature (T) and [CO2] (Asat) of 40 tree species
from 21 families in tropical mountain forests at
1000-, 2000-, and 3000-m elevation in southern
Ecuador. We tested the hypothesis that stand-level
averages of Asat and leaf dark respiration (RD) per
leaf area remain constant with elevation. Standlevel
means of Asat were 8.8, 11.3, and 7.2 lmol
CO2 m-2 s-1; those of RD 0.8, 0.6, and 0.7 lmol
CO2 m-2 s-1 at 1000-, 2000-, and 3000-m elevation,
respectively, with no significant altitudinal
trend. We obtained coefficients of among-species
variation in Asat and RD of 20?53% (n = 10?16 tree
species per stand). Examining our data in the
context of a pan-tropical Asat data base for mature
tropical trees (c. 170 species from 18 sites at variable
elevation) revealed that area-based Asat
decreases in tropical mountains by, on average,
1.3 lmol CO2 m-2 s-1 per km altitude increase (or
by 0.2 lmol CO2 m-2 s-1 per K temperature
decrease). The Asat decrease occurred despite an
increase in leaf mass per area with altitude. Local
geological and soil fertility conditions and related
foliar N and P concentrations considerably influenced
the altitudinal Asat patterns. We conclude
that elevation is an important influencing factor of
the photosynthetic activity of tropical trees. Lowered
Asat together with a reduced stand leaf area
decrease canopy C gain with elevation in tropical
mountains.
Keywords:
| altitudinal gradient | foliar N | foliar P | leaf dark respiration | light-saturated net photosynthesis | tropical lowland forests | mature trees | C source limitation | tropical montane forest |
Literature type specific fields:
ARTICLE
Journal: Ecosystems
Volume: 15
Page Range: 958-973
Metadata Provider:
Individual: Jürgen Homeier
Contact:
Online Distribution:
Download File: http://www.tropicalmountainforest.org/publications.do?citid=1116

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