Wittich, B.; Horna, V.; Homeier, J. & Leuschner, C. (2012): <b>Altitudinal decrease in photosynthetic capacity in tropical trees: A case study from Ecuador and a pantropical literature analysis</b>. <i>Ecosystems</i> <b>15</b>, 958-973.
Resource Description
Title:
Altitudinal decrease in photosynthetic capacity in tropical trees: A case study from Ecuador and a pantropical literature analysis
In tropical mountains, trees are the dominant life<br/>
form from sea level to above 4,000-m altitude under<br/>
highly variable thermal conditions (range of<br/>
mean annual temperatures: <8 to >28C). How<br/>
light-saturated net photosynthesis of tropical trees<br/>
adapts to variation in temperature, atmospheric<br/>
CO2 concentration, and further environmental<br/>
factors, that change along elevation gradients,<br/>
is not precisely known. With gas exchange<br/>
measurements in mature trees, we determined<br/>
light-saturated net photosynthesis at ambient<br/>
temperature (T) and [CO2] (Asat) of 40 tree species<br/>
from 21 families in tropical mountain forests at<br/>
1000-, 2000-, and 3000-m elevation in southern<br/>
Ecuador. We tested the hypothesis that stand-level<br/>
averages of Asat and leaf dark respiration (RD) per<br/>
leaf area remain constant with elevation. Standlevel<br/>
means of Asat were 8.8, 11.3, and 7.2 lmol<br/>
CO2 m-2 s-1; those of RD 0.8, 0.6, and 0.7 lmol<br/>
CO2 m-2 s-1 at 1000-, 2000-, and 3000-m elevation,<br/>
respectively, with no significant altitudinal<br/>
trend. We obtained coefficients of among-species<br/>
variation in Asat and RD of 20?53% (n = 10?16 tree<br/>
species per stand). Examining our data in the<br/>
context of a pan-tropical Asat data base for mature<br/>
tropical trees (c. 170 species from 18 sites at variable<br/>
elevation) revealed that area-based Asat<br/>
decreases in tropical mountains by, on average,<br/>
1.3 lmol CO2 m-2 s-1 per km altitude increase (or<br/>
by 0.2 lmol CO2 m-2 s-1 per K temperature<br/>
decrease). The Asat decrease occurred despite an<br/>
increase in leaf mass per area with altitude. Local<br/>
geological and soil fertility conditions and related<br/>
foliar N and P concentrations considerably influenced<br/>
the altitudinal Asat patterns. We conclude<br/>
that elevation is an important influencing factor of<br/>
the photosynthetic activity of tropical trees. Lowered<br/>
Asat together with a reduced stand leaf area<br/>
decrease canopy C gain with elevation in tropical<br/>
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:
email:
jhomeie <at> gwdg.de
Faculty of Resource Management
University of Applied Sciences and Arts (HAWK)
37077 Göttingen
Germany
