Publications
Found 26 publication(s)
- of type article
Wallis, C.; Homeier, J.; Pena Tamayo, J.E.; Brandl, R.; Farwig, N. & Bendix, J. (2019): Modeling tropical montane forest biomass, productivity and canopy traits with multispectral remote sensing data. Remote Sensing of Environment 225, 77 - 92.
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DOI: 10.1016/j.rse.2019.02.021
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Abstract:
Abstract:
Tropical montane forests, particularly Andean rainforest, are important ecosystems for regional carbon and water cycles as well as for biological diversity and speciation. Owing to their remoteness, however, ecological key-processes are less understood as in the tropical lowlands. Remote sensing allows modeling of variables related to spatial patterns of carbon stocks and fluxes (e.g., biomass) and ecosystem functioning (e.g., functional leaf traits). However, at a landscape scale most studies conducted so far are based on airborne remote sensing data which is often available only locally and for one time-point. In contrast, multispectral satellites at moderate spectral and spatial resolutions are able to provide spatially continuous and repeated observations. Here, we investigated the effectiveness of Landsat-8 imagery in modeling tropical montane forest biomass, its productivity and selected canopy traits. Topographical, spectral and textural metrics were derived as predictors. To train and validate the models, in-situ data was sampled in 54 permanent plots in forests of southern Ecuador distributed within three study sites at 1000 m, 2000 m and 3000 m a.s.l. We used partial least squares regressions to model and map all response variables. Along the whole elevation gradient biomass and productivity models explained 31%, 43%, 69% and 63% of variance in aboveground biomass, annual wood production, fine litter production and aboveground net primary production, respectively. Regression models of canopy traits measured as community weighted means explained 62%, 78%, 65% and 65% of variance in leaf toughness, specific leaf area, foliar N concentration, and foliar P concentration, respectively. Models at single study sites hardly explained variation in aboveground biomass and the annual wood production indicating that these measures are mainly determined by the change of forest types along with elevation. In contrast, the models of fine litter production and canopy traits explained between 8%–85% in variation depending on the study site. We found spectral metrics, in particular a vegetation index using the red and the green band to provide complementary information to topographical metrics. The model performances for estimating leaf toughness, biochemical canopy traits and related fine litter production all improved when adding spectral information. Our findings therefore revealed that differences in fine litter production and canopy traits in our study area are driven by local changes in vegetation edaphically induced by topography. We conclude that Landsat-derived metrics are useful in modeling fine litter production and biochemical canopy traits, in a topographically and ecologically complex tropical montane forest.
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Keywords: |
Ecuador |
Aboveground forest productivity |
Ecosystem process |
Fine litter production |
Foliar N |
Foliar P |
Grey level co-occurrence texture |
Landsat-8 |
Leaf toughness |
Specific leaf area |
Annual wood production |
Quichimbo Miguitama, P.G.; Jiménez, L.S.; Veintimilla, D.; Potthast, K.; Tischer, A.; Günter, S.; Mosandl, R. & Hamer, U. (2019): Nutrient dynamics in an Andean forest region: a case study of exotic and native species plantations in southern Ecuador. New Forests -, 1 - 22.
Quichimbo Miguitama, P.G.; Jiménez, L.; Veintimilla, D.; Tischer, A.; Günter, S.; Mosandl, R. & Hamer, U. (2017): Forest Site Classification in the Southern Andean Region of Ecuador: A Case Study of Pine Plantations to Collect a Base of Soil Attributes. Forests 473(8), 1-22.
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DOI: 10.3390/f8120473
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Abstract:
Abstract:
Forest site classification adapted to the respective site conditions is one prerequisite for
sustainable silviculture. This work aims to initiate the forest site classification for pine plantations
in the southern Andean region of Ecuador. Forest productivity, estimated by the dominant height
of 20-year-old trees (DH20), was related to data from climate, topography, and soil using 23 plots
installed in pine plantations in the province of Loja. Forest site productivity was classified as:
low (class C: 13.4 m), middle (class B: 16.6 m), and high (Class A: 22.3 m). Strong determinants
to differentiate the forest site classes were: the short to medium term available Ca and K stocks
(organic layer + mineral soil standardized to a depth of 60 cm), soil acidity, the C:N ratio, clay and
sand content, forest floor thickness, altitude, and slope. The lowest forest productivity (Class C)
is mainly associated with the lowest short to medium term available K and Ca stocks. Whereas,
in site classes with the highest forest productivity, pines could benefit from a more active microbial
community releasing N and P, since the soil pH was about 1 unit less acidic. This is supported by the
lowest forest floor thickness and the narrowest C:N ratio.
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Keywords: |
forest |
soil nutrients |
soil |
pine forest |
Pinus patula |
Forest plantation |
forest productivity |
Tiede, Y.; Homeier, J.; Cumbicus Torres, N.; Pena Tamayo, J.E.; Albrecht, J.; Ziegenhagen, B.; Bendix, J.; Brandl, R. & Farwig, N. (2016): Phylogenetic niche conservatism does not explain elevational patterns of species richness, phyodiversity and family age of tree assemblages in Andean rainforest. Erdkunde 70(1), 83-106.
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DOI: 10.3112/erdkunde.2016.01.06
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Abstract:
Abstract:
Phylogenetic niche conservatism (PNC) is the tendency of species within a clade to retain ancestral traits and
to persist in their primary ecological niches on geological time scales. It links evolutionary and ecological processes and has
been hypothesized to explain patterns of species richness and the composition of species assemblages. Decreasing patterns
of species richness along latitudinal gradients were often explained by the combination of ancient tropical climates, trait
retention of tropical lineages and environmental filtering. PNC also predicts decreasing phylodiversity and family age with
decreasing tropicality and has been invoked to explain these patterns along climatic gradients across latitudinal as well as elevational
gradients.
However,
recent
studies
on
tree
assemblages
along
latitudinal
and
elevational
gradients
in
South
America
found
patterns
contradicting
the
PNC
framework.
Our
study
aims
to
shed
light
on
these
contradictions
using
three
different
metrics of the phylogenetic composition that form a gradient from recent evolutionary history to deep phylogenetic
relationships. We analyzed the relationships between elevation and taxonomic species richness, phylodiversity and family
age of tree assemblages in Andean rainforests in Ecuador. In contrast to predictions of the PNC we found no associations
of elevation with species richness of trees and increasing clade level phylodiversity and family age of the tree assemblages
with elevation. Interestingly, we found that patterns of phylodiversity across the studied elevation gradient depended especially
on
the
deep
nodes
in
the
phylogeny.
We
therefore
suggest
that
the
dispersal
of
evolutionarily old plant lineages with
extra-tropical origins influences the recent composition of tree assemblages in the Andes. Further studies spanning broader
ecological gradients and using better resolved phylogenies to estimate family and species ages are needed to obtain a deeper
mechanistic understanding of the processes that drive the assembly of tree communities along elevational gradients.
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Keywords: |
Ecuador |
vegetation geography |
tree species assembly |
elevational gradient |
orogeny |
Müller, A.K.; Matson, A.; Corre, M. & Veldkamp, E. (2015): Soil N2O fluxes along an elevation gradient of tropical montane forests under experimental nitrogen and phosphorus addition. Frontiers in Earth Sscience 3, 66.
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DOI: 10.3389/feart.2015.00066
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Abstract:
Abstract:
Nutrient deposition to tropical forests is increasing, which could affect soil fluxes of nitrous oxide (N2O), a powerful greenhouse gas. We assessed the effects of 35–56 months of moderate nitrogen (N) and phosphorus (P) additions on soil N2O fluxes and net soil N-cycling rates, and quantified the relative contributions of nitrification and denitrification to N2O fluxes. In 2008, a nutrient manipulation experiment was established along an elevation gradient (1000, 2000, and 3000 m) of montane forests in southern Ecuador. Treatments included control, N, P, and N+P addition (with additions of 50 kg N ha?1 yr?1 and 10 kg P ha?1 yr?1). Nitrous oxide fluxes were measured using static, vented chambers and N cycling was determined using the buried bag method. Measurements showed that denitrification was the main N2O source at all elevations, but that annual N2O emissions from control plots were low, and decreased along the elevation gradient (0.57 ± 0.26–0.05 ±0.04 kg N2O-N ha?1 yr?1). We attributed the low fluxes to our sites' conservative soil N cycling as well as gaseous N losses possibly being dominated by N2. Contrary to the first 21 months of the experiment, N addition did not affect N2O fluxes during the 35–56 month period, possibly due to low soil moisture contents during this time. With P addition, N2O fluxes and mineral N concentrations decreased during Months 35–56, presumably because plant P limitations were alleviated, increasing plant N uptake. Nitrogen plus phosphorus addition showed similar trends to N addition, but less pronounced given the counteracting effects of P addition. The combined results from this study (Months 1–21 and 35–56) showed that effects of N and P addition on soil N2O fluxes were not linear with time of exposure, highlighting the importance of long-term studies.
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Keywords: |
NUMEX |
nitrogen |
N2O emissions |
Baldos, A.; Corre, M. & Veldkamp, E. (2015): Response of N cycling to nutrient inputs in forest soils across a 1000–3000 m elevation gradient in the Ecuadorian Andes. Ecology 96(3), 749 - 761.
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DOI: 10.1890/14-0295.1.sm
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Abstract:
Abstract:
Large areas in the tropics receive elevated atmospheric nutrient inputs. Presently, little is known on how nitrogen (N) cycling in tropical montane forest soils will respond to such increased nutrient inputs. We assessed how gross rates of mineral N production (N mineralization and nitrification) and microbial N retention (NH4+ and NO3- immobilization and dissimilatory NO3- reduction to NH4+ [DNRA]) change with elevated N and phosphorus (P) inputs in montane forest soils at 1000-, 2000-, and 3000-m elevations in
south Ecuador. At each elevation, four replicate plots (20320 m each) of control, N (added at 50 kg N ha-1yr-1), P (added at 10 kg P ha-1 yr-1), and combined N x P additions have been established since 2008. We measured gross N cycling rates in 2010 and 2011, using 15N pool dilution techniques with in situ incubation of intact soil cores taken from the top 5 cm of soil. In control plots, gross soil-N cycling rates decreased with increase in elevation, and microbial N retention was tightly coupled with mineral N production. At 1000 m and 2000 m, four-year N and combined N þ P additions increased gross mineral N production but decreased NH4+ and NO3- immobilization and DNRA compared to the control. At 3000 m, four-year N and combined N x P additions increased gross N mineralization rates and decreased DNRA
compared to the control; although NH4+ and NO3- immobilization in the N and NxP plots were not different from the control, these were lower than their respective mineral N production. At all elevations, decreased microbial N retention was accompanied by decreased microbial biomass C and C:N ratio. P addition did not affect any of the soil-N cycling processes. Our results signified that four years of N addition, at a rate expected to occur at these sites, uncoupled the soil-N cycling processes, as indicated by decreased microbial N retention. This fast response of soil-N cycling processes across elevations implies that greater
attention should be paid to the biological implications on montane forests of such uncoupled soil-N cycling.
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Keywords: |
NUMEX |
nitrogen |
phosphorus |
Matson, A.; Corre, M.; Burneo Valdivieso, J.I. & Veldkamp, E. (2014): Free-living nitrogen fixation responds to elevated nutrient inputs in tropical montane forest floor and canopy soils of southern Ecuador. Biogeochemistry 122, 281-294.
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DOI: 10.1007/s10533-014-0041-8
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Abstract:
Abstract:
Although often overlooked in forest research, the canopy can play an important role in forest nutrient cycling. Since the canopy is spatially isolated from the forest floor, nutrient cycling in the
two areas may differ as terrestrial nutrients accumulate. We measured rates of free-living N2 fixation
along an elevation gradient (1,000, 2,000 and 3,000 m) of tropical montane canopy soils, compared
these to rates measured in the top 5 cm of forest floor soils (excluding fresh litter), and assessed the effects of elevated nutrient inputs to the forest floor. N2 fixation was measured using the acetylene reduction assay. Measurements occurred in the field, in the wet and dry seasons, using intact cores of soil. The forest floor had been fertilized biannually with moderate amounts of nitrogen (N) and phosphorus (P) for 4 years; treatments included control, N, P and N x P. N2 fixation rates exhibited little variation with Elevation but were higher in the dry season than the wet season. Fixation was inhibited in forest floor N plots compared to control and P plots, and stimulated in canopy P plots compared to control. At 2,000 m, the canopy contributed 12 % of measured canopy and forest floor N2 fixation (1.2 kg N ha-1 year-1).
Results suggest that N2 fixation is an active process in canopy soils, which is variable across seasons and
sensitive to changes in terrestrial nutrient availability. Long-term terrestrial accumulation of N and/or P has the potential to significantly change the dynamics of soil N cycling in these canopies.
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Keywords: |
NUMEX |
nitrogen |
canopy |
nitrogen fixation |
Matson, A.; Corre, M. & Veldkamp, E. (2014): Nitrogen cycling in canopy soils of tropical montane forests responds rapidly to indirect N and P fertilization. Global Change Biiology 20, 3802-3813.
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DOI: 10.1111/gcb.12668
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Abstract:
Abstract:
Although the canopy can play an important role in forest nutrient cycles, canopy-based processes are often overlooked in studies on nutrient deposition. In areas of nitrogen (N) and phosphorus (P) deposition, canopy soils may retain a significant proportion of atmospheric inputs, and also receive indirect enrichment through root uptake followed by throughfall or recycling of plant litter in the canopy. We measured net and gross rates of N cycling in canopy soils of tropical montane forests along an elevation gradient and assessed indirect effects of elevated nutrient inputs to the forest floor. Net N cycling rates were measured using the buried bag method. Gross N cycling rates were measured using 15N pool dilution techniques. Measurements took place in the field, in the wet and dry season,using intact cores of canopy soil from three elevations (1000, 2000 and 3000 m). The forest floor had been fertilized biannually with moderate amounts of N and P for 4 years; treatments included control, N, P, and N + P. In control plots, gross rates of NH4+ transformations decreased with increasing elevation; gross rates of NO3- transformations
did not exhibit a clear elevation trend, but were significantly affected by season. Nutrient-addition effects were different at each elevation, but combined N + P generally increased N cycling rates at all elevations. Results showed that canopy soils could be a significant N source for epiphytes as well as contributing up to 23% of total (canopy + forest floor) mineral N production in our forests. In contrast to theories that canopy soils are decoupled from nutrient cycling in forest floor soil, N cycling in our canopy soils was sensitive to slight changes in forest floor nutrient availability.Long-term atmospheric N and P deposition may lead to increased N cycling, but also increased mineral N losses from the canopy soil system.
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Keywords: |
NUMEX |
nitrogen |
canopy |
phosphorus |
Homeier, J.; Hertel, D.; Camenzind, T.; Cumbicus Torres, N.; Maraun, M.; Martinson, G.; Poma, N.; Rillig, M.C.; Sandmann, D.; Scheu, S.; Veldkamp, E.; Wilcke, W.; Wullaert, H. & Leuschner, C. (2012): Tropical Andean Forests Are Highly Susceptible to Nutrient Inputs - Rapid Effects of Experimental N and P Addition to an Ecuadorian Montane Forest. PLoS ONE 7, e47128.
Martinson, G.; Corre, M. & Veldkamp, E. (2012): Responses of nitrous oxide fluxes and soil nitrogen cycling to nutrient additions in montane forests along an elevation gradient in southern Ecuador. Biogeochemistry online , online.
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DOI: 10.1007/s10533-012-9753-9
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Abstract:
Abstract:
Tropical montane forests are commonly limited by N or co-limited by N and P. Projected increases in N deposition in tropical montane regions are thought to be insufficient for vegetation demand and are not therefore expected to affect soil N availability and N2O emissions. We established a factorial Nand P-addition experiment (i.e., N, P, N ? P, and control) across an elevation gradient of montane forests in Ecuador to test these hypotheses: (1) moderate rates of N and P additions are able to stimulate soil-N cycling rates and N2O fluxes, and (2) the magnitude and timing of soil N2O-flux responses depend on the initial nutrient status of the forest soils. Moderate rates of nutrients were added: 50 kg N ha-1 year-1 (in the form of urea) and 10 kg P ha-1 year-1 (in the form of NaH2PO4 . 2H2O) split in two equal applications. We tested the hypotheses by measuring changes in net rates of soil–N cycling and N2O fluxes during the first 2 years (2008??2009) of nutrient manipulation in an oldgrowth premontane forest at 1,000 m, growing on a Cambisol soil with no organic layer, in an old-growth lower montane forest at 2,000 m, growing on a Cambisol soil with an organic layer, and an oldgrowth upper montane rainforest at 3,000 m, growing on a Histosol soil with a thick organic layer. Among the control plots, net nitrification rates were largest at the 1,000-m site whereas net nitrification was not detectable at the 2,000and 3,000-m sites. The already large net nitrification at the 1,000-m site was not affected by nutrient additions, but net nitrification became detectable at the 2,000and 3000-m sites after the second year of N and N + P additions. N2O emissions increased rapidly following N and N ? P additions at the 1,000-m site whereas only smaller increases occurred at the 2,000and 3,000-m sites during the second year of N and N + P additions. Addition of P alone had no effect on net rates of soil N cycling and N2O fluxes at any elevation. Our results showed that the initial soil N status, which may also be influenced by presence or absence of organic layer, soil moisture and temperature as encompassed by the elevation gradient, is a good indicator of how soil N cycling and N2O fluxes may respond to future increases in nutrient additions.
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Keywords: |
phosphorus |
mountain forest |
N2O emissions |
soil N availability |
nutrient manipulation |
nutrient limitation |
wood specific gravity |
aboveground biomass |
environmental gradients |
carbon stocks |
Pilodyn wood tester |
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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Abstract:
Abstract:
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 |
Wolf, K.; Veldkamp, E.; Homeier, J. & Martinson, G. (2011): Nitrogen availability links forest productivity, soil nitrous oxide and nitric oxide fluxes of a tropical montane forest in southern Ecuador. Global Biochmical Cycles 25, 12.
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DOI: 10.1029/2010GB003876
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Abstract:
Abstract:
Tropical forests are important sources of the greenhouse gas nitrous oxide (N2O) and of nitric oxide (NO), a precursor of ozone. In tropical montane forests nitrogen limitation is common which affects both soil N2O and NO fluxes and forest productivity. Here we present evidence that forest productivity and N-oxide (N2O + NO) fluxes are linked through N availability along elevation and topographic gradients in tropical montane forests. We measured N-oxide fluxes, several indices of N availability, and forest productivity along an elevation gradient from 1000 m to 3000 m and along topographic gradients. Organic layer thickness of the soils increased and N availability decreased with increasing elevation and along the topographic gradient from the lower slope position to the ridges. Annual N2O fluxes ranged from -0.53 µg(N)m-2h-1 to 14.54 µg(N)m-2h-1 while NO fluxes ranged from -0.02 µg(N)m-2h-1 to 1.13 µg(N)m-2h-1. Both N-oxide fluxes and forest productivity increased with increasing N availability and showed close positive correlations with indices of N availability (C/N ratio and  15N signature of litterfall). We interpret the close correlations of N-oxide fluxes with total litterfall and tree basal area increment as evidence that N availability links N-oxide fluxes and forest productivity. This opens the possibility to include forest productivity as co-variable in predictions of N-oxide fluxes in nitrogen limited tropical montane forests. Especially increment of tree basal area was a promising proxy to predict soil N-oxide fluxes in these N limited ecosystems, possibly because it better reflects long-term forest productivity than total litterfall.
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Keywords: |
nitrogen |
soil N availability |
element fluxes |
Martinson, G.; Werner, F.A.; Scherber, C.; Conrad, R.; Corre, M.; Flessa, H.; Wolf, K.; Klose, M.; Gradstein, S.R. & Veldkamp, E. (2010): Methane emissions from tank bromeliads in neotropical forests. Nature Geoscience 2010(3), 766-769.
Gerique, A. & Veintimilla, D. (2007): Useful Plants and Weeds Occuring in Shuar, Saraguro, and Mestizo Communities. Checklist of the Reserva Biológica San Francisco (Prov. Zamora-Chinchipe, S-Ecuador). Ecotropical Monographs 4, 237-256.