Publicaciones
Se encontró/encontraron 5 Publicaciones(s).
Liedtke, R. (2016): Mobile and Soil Bonded Phosphomonoesterase Activity of the Organic Layer along an Altitudinal Gradient in South Ecuador University of Tuebingen, bachelor thesis
Werner, F.A.; Köster, N.; Kessler, M. & Gradstein, S.R. (2011): Is the resilience of epiphyte assemblages to human disturbance a function of local climate?. Ecotropica 17, 15-20.
Wittich, B.; Homeier, J. & Leuschner, C. (2014): Ammonium, nitrate and glycine uptake of six Ecuadorian tropical montane forest tree species: an in situ pot experiment with saplings. Journal of Tropical Ecology xx, xx.
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DOI: 10.1017/S0266467414000650
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Resumen:
Resumen:
Not much is known about the nitrogen (N) uptake capacity and N-form preference of tropical trees. In a
replicated labelling experiment with 15N-ammonium, 15N-nitrate and dual-labelled glycine applied to saplings of six
tree species from southern Ecuadorianmontane forests, we tested the hypotheses that (1) the saplings of tropical trees
are capable of using organicNeven though they are forming arbuscularmycorrhizas, and (2) with increasing altitude,
tree saplings increasingly prefer ammonium and glycine over nitrate due to reduced nitrification and growing humus
accumulation. Three- to 5-y-old saplings of two species each from 1000, 2000 and 3000 m asl were grown in pots
inside the forest at their origin and labelled with non-fertilizing amounts of the three N forms; 15N enrichment was
detected 5 days after labelling in fine roots, coarse roots, shoots and leaves. The six species differed with respect to
their N-form preference, but neither the abundance of ammonium and nitrate in the soil nor altitude (1000–3000
m asl) seemed to influence the preference. Two species (those with highest growth rate) preferred NH4+ over NO3?,
while the other four species took up NO3? and NH4+ at similar rates when both N forms were equally available. After
13C-glycine addition, 13C was significantly accumulated in the biomass of three species (all species with exclusively
AM symbionts) but a convincing proof of the uptake of intact glycine molecules by these tropical montane forest trees
was not obtained.
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Keywords: |
nitrogen |
nitrate |
ammonium |
altitudinal gradient |
15N tracer study |
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.
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DOI: 10.1007/s10021-012-9556-9
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Resumen:
Resumen:
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.
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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 |
Wolf, K.; Flessa, H. & Veldkamp, E. (2011): Atmospheric methane uptake by tropical montane forest soils and the contribution of the organic layer. Biogeochemistry online, 15.
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DOI: 10.1007/s10533-011-9681-0
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Resumen:
Resumen:
Microbial oxidation in aerobic soils is the primary biotic sink for atmospheric methane (CH4), a powerful greenhouse gas. Although tropical forest soils are estimated to globally account for about 28% of annual soil CH4 consumption (6.2 Tg CH4 year−1), limited data are available on CH4 exchange from tropical montane forests. We present the results of an extensive study on CH4 exchange from tropical montane forest soils along an elevation gradient (1,000, 2,000, 3,000 m) at different topographic positions (lower slope, mid-slope, ridge position) in southern Ecuador. All soils were net atmospheric CH4 sinks, with decreasing annual uptake rates from 5.9 kg CH4?C ha−1 year−1 at 1,000 m to 0.6 kg CH4?C ha−1 year−1 at 3,000 m. Topography had no effect on soil atmospheric CH4 uptake. We detected some unexpected factors controlling net methane fluxes: positive correlations between CH4 uptake rates, mineral nitrogen content of the mineral soil and with CO2 emissions indicated that the largest CH4 uptake corresponded with favorable conditions for microbial activity. Furthermore, we found indications that CH4 uptake was N limited instead of inhibited by NH4 +. Finally, we showed that in contrast to temperate regions, substantial high affinity methane oxidation occurred in the thick organic layers which can influence the CH4 budget of these tropical montane forest soils. Inclusion of elevation as a co-variable will improve regional estimates of methane exchange in these tropical montane forests.
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Keywords: |
altitudinal gradient |
organic layer |
methane |
carbon dioxide |