Publications
Found 516 publication(s)
- of type article
Paulick, S.; Dislich, C.; Homeier, J.; Fischer, R. & Huth, A. (2017): The carbon fluxes in different successional stages: modelling the dynamics of tropical montane forests in South Ecuador. Forest Ecosystems 4, 5.
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DOI: 10.1186/s40663-017-0092-0
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Abstract:
Abstract:
Background:
Tropical forests play an important role in the global carbon (C) cycle. However, tropical montane forests have been studied less than tropical lowland forests, and their role in carbon storage is not well understood. Montane forests are highly endangered due to logging, land-use and climate change. Our objective was to analyse how the carbon balance changes during forest succession.
Methods:
In this study, we used a method to estimate local carbon balances that combined forest inventory data with process-based forest models. We utilised such a forest model to study the carbon balance of a tropical montane forest in South Ecuador, comparing two topographical slope positions (ravines and lower slopes vs upper slopes and ridges).
Results: The simulation results showed that the forest acts as a carbon sink with a maximum net ecosystem exchange (NEE) of 9.3 Mg C?(ha?yr)?1 during its early successional stage (0–100 years). In the late successional stage, the simulated NEE fluctuated around zero and had a variation of 0.77 Mg C?(ha?yr) –1. The simulated variability of the NEE was within the range of the field data. We discovered several forest attributes (e.g., basal area or the relative amount of pioneer trees) that can serve as predictors for NEE for young forest stands (0–100 years) but not for those in the late
successional stage (500–1,000 years). In case of young forest stands these correlations are high, especially between stand basal area and NEE.
Conclusion:
In this study, we used an Ecuadorian study site as an example of how to successfully link a forest model with forest inventory data, for estimating stem-diameter distributions, biomass and aboveground net primary productivity. To conclude, this study shows that process-based forest models can be used to investigate the carbon balance of tropical montane forests. With this model it is possible to find hidden relationships between forest attributes and forest carbon fluxes. These relationships promote a better understanding of the role of tropical montane forests in
the context of global carbon cycle, which in future will become more relevant to a society under global change.
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Keywords: |
succession |
FORMIND |
tropical montane forest |
forest model |
carbon balance |
forest productivity |
Silva, B.; Alava Núñez, P.; Strobl, S.; Beck, E. & Bendix, J. (2017): Area-wide evapotranspiration monitoring at the crown level of a tropical mountain rain forest. Remote Sensing of Environment 194, 219–229.
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DOI: 10.1016/j.rse.2017.03.023
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Abstract:
Abstract:
Ecosystem water regulation couples energy and water balance, depends on the integrity of the ecosystem, and responds to changes in climate. Changes in tree-water relationships in the biodiversity hotspot of the tropical Andes in southern Ecuador might be potentially observed at the level of individual trees, thus providing an efficient ecosystem monitoring method with applications in forest management and conservation at the tree and landscape levels. In this study, we combine area-average measurements from a laser scintillometer above the forest with optical satellite data at high spatial resolution to obtain area-wide evapotranspiration data. The processing of field data includes the calculation of energy storage in forest biomass and the partitioning of evapotranspiration into transpiration and evaporation. Satellite-based estimates are calibrated by using tower flux measurements and meteorological data within periods of humid and less-humid atmosphere. The annual evapotranspiration was 1316 mm, of which 1086 mm per year corresponds to the forest transpiration at the study site. Average values of 4.7 and 4.1 mm d-1 per tree crown are observed under humid and less-humid atmospheric conditions, respectively, when applying high-resolution area-wide evapotranspiration in individual crown analysis. Approximately 24% of the observed crowns show a positive monthly change in ET, and 51% of the crowns show a significant change in the daily ET, which can be considered sensitive individuals concerning water relationships. The limitations in the area-wide evapotranspiration at the crown level can be explained by considering the spectral responses of the crown individuals. The presented method can be robustly deployed in the ecological monitoring of mountain forests.
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Keywords: |
remote sensing |
Evapotranspiration |
crown scale |
Silva, B.; Álava-Núñez, P.; Strobl, S.; Beck, E. & Bendix, J. (2017): Area-wide evapotranspirationmonitoring at the crown level of a tropical mountain rain forest. Remote Sensing of Environment 194( ), 219-229.
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DOI: 10.1016/j.rse.2017.03.023
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Abstract:
Abstract:
Ecosystem water regulation couples energy and water balance, depends on the integrity of the ecosystem, and
responds to changes in climate. Changes in tree-water relationships in the biodiversity hotspot of the tropical
Andes in southern Ecuador might be potentially observed at the level of individual trees, thus providing an ef?-
cient ecosystem monitoring method with applications in forest management and conservation at the tree and
landscape levels. In this study,we combine area-averagemeasurements froma laser scintillometer above the for-
est with optical satellite data at high spatial resolution to obtain area-wide evapotranspiration data. The process-
ing of ?eld data includes the calculation of energy storage in forest biomass and the partitioning of
evapotranspiration into transpiration and evaporation. Satellite-based estimates are calibrated by using tower
?ux measurements and meteorological data within periods of humid and less-humid atmosphere. The annual
evapotranspiration was 1316 mm, of which 1086 mm per year corresponds to the forest transpiration at the
study site. Average values of 4.7 and 4.1 mm d?1
per tree crown are observed under humid and less-humid at-
mospheric conditions, respectively, when applying high-resolution area-wide evapotranspiration in individual
crown analysis. Approximately 24% of the observed crowns show a positive monthly change in ET, and 51% of
the crowns show a signi?cant change in the daily ET, which can be considered sensitive individuals concerning
water relationships. The limitations in the area-wide evapotranspiration at the crown level can be explained
by considering the spectral responses of the crown individuals. The presented method can be robustly deployed
in the ecological monitoring of mountain forests.
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Keywords: |
remote sensing |
Evapotranspiration |
crown scale |
Homeier, J.; Báez, S.; Hertel, D. & Leuschner, C. (2017): Editorial: Tropical forest ecosystem responses to increasing nutrient availability. Frontiers in Earth Science 5, 27.
Wallis, C.; Brehm, G.; Donoso, D.A.; Fiedler, K.; Homeier, J.; Paulsch, D.; Suessenbach, D.; Tiede, Y.; Brandl, R.; Farwig, N. & Bendix, J. (2017): Remote sensing improves prediction of tropical montane species diversity but performance differs among taxa. Ecological Indicators 1(1), 1-10.
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DOI: 10.1016/j.ecolind.2017.01.022
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Abstract:
Abstract:
Texture information from passive remote sensing images provides surrogates for habitat structure, which is relevant for modeling biodiversity across space and time and for developing effective ecological indicators. However, the applicability of this information might differ among taxa and diversity measures. We compared the ability of indicators developed from texture analysis of remotely sensed images to predict species richness and species turnover of six taxa (trees, pyraloid moths, geometrid moths, arctiinae moths, ants, and birds) in a megadiverse Andean mountain rainforest ecosystem. Partial least-squares regression models were fitted using 12 predictors that characterize the habitat and included three topographical metrics derived from a high-resolution digital elevation model and nine texture metrics derived from very high-resolution multi-spectral orthophotos. We calculated image textures derived from mean, correlation, and entropy statistics within a relatively broad moving window (102 m × 102 m) of the near infra-red band and two vegetation indices. The model performances of species richness were taxon dependent, with the lowest predictive power for arctiinae moths (4%) and the highest for ants (78%). Topographical metrics sufficiently modeled species richness of pyraloid moths and ants, while models for species richness of trees, geometrid moths, and birds benefited from texture metrics. When more complexity was added to the model such as additional texture statistics calculated from a smaller moving window (18 m × 18 m), the predictive power for trees and birds increased significantly from 12% to 22% and 13% to 27%, respectively. Gradients of species turnover, assessed by non-metric two-dimensional scaling (NMDS) of Bray-Curtis dissimilarities, allowed the construction of models with far higher predictability than species richness across all taxonomic groups, with predictability for the first response variable of species turnover ranging from 64% (birds) to 98% (trees) of the explained change in species composition, and predictability for the second response variable of species turnover ranging from 33% (trees) to 74% (pyraloid moths). The two NMDS axes effectively separated compositional change along the elevational gradient, explained by a combination of elevation and texture metrics, from more subtle, local changes in habitat structure surrogated by varying combinations of texture metrics. The application of indicators arising from texture analysis of remote sensing images differed among taxa and diversity measures. However, these habitat indicators improved predictions of species diversity measures of most taxa, and therefore, we highly recommend their use in biodiversity research.
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Keywords: |
moths |
species richness |
species turnover |
mountain rainforest |
tropical trees |
Birds |
ants |
orthophotos |
Timbe, E.; Feyen, J.; Windhorst, D.; Breuer, L.; Crespo, P.; Celleri, R. & Frede, H. (2017): Multicriteria assessment of water dynamics reveals subcatchment variability in a seemingly homogeneous tropical cloud forest catchment. Hydrological Processes 31(7), 1456-1468.
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DOI: 10.1002/hyp.11146
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Abstract:
Abstract:
To improve the current knowledge of the rainfall–runoff phenomena of tropical montane catchments, we explored the usefulness of several hydrological indicators on a nested cloud forest catchment (76.9 km2). The used metrics belong to 5 categories: baseflow mean transit time, physicochemical properties of stream water, land cover, topographic, and hydrometric parameters. We applied diverse statistical techniques for data analysis and to contrast findings. Multiple regression analysis showed that mean transit times of base flow could be efficiently predicted by sodium concentrations (higher during baseflows) and temperatures of stream water, indicating a major influence of geomorphology rather than topographic or land cover characteristics. Principal component analysis revealed that no specific subset of catchment indicators could be identified as prevailing descriptors for all catchments. The agglomerative hierarchical clustering analysis provided concomitant results, implying larger levels of dissimilarity between smaller subcatchments than between larger ones. Overall, results point out an intricate interdependence of diverse processes at surface and subsurface level indicating a high level of heterogeneity. Disregarding heterogeneity of nested or paired catchments could lead to incomplete or misleading conclusions, especially in tropical mountain regions where pronounced spatial and temporal gradients are present.
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Keywords: |
tropical cloud forest |
catchment flow dynamics |
catchment heterogeneity |
mean transit times |
multicriteria assessment |
rainfall–runoff processes |
Butz, P.; Raffelsbauer, V.; Graefe, S.; Peters, T.; Cueva, E.; Hölscher, D. & Bräuning, A. (2016): Tree responses to moisture fluctuations in a neotropical dry forest as potential climate change indicators. Ecological Indicators 1(1), 1-13.
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DOI: 10.1016/j.ecolind.2016.11.021
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Abstract:
Abstract:
Trees in tropical dry forests (TDFs) have manifold drought coping strategies including succulence of different plant organs, wood anatomical traits and leaf phenology. As water availability to plants is the limiting factor for physiological activity, changes in precipitation patterns are assumed to have strong influences on tree phenology, growth and water turnover. Our objectives were to assess patterns in leaf phenology, radial stem circumference changes and sap flux responses to fluctuating moisture regimes of selected species. Based on these findings we evaluated the potential suitability as indicator species for climate change effects. The study was implemented at different elevational positions in a submontane dry forest of southern Ecuador. Annual rainfall is 600 mm with an eight months dry period; moisture availability slightly increases with altitude because of moist air coming from the Pacific. At three altitudes,we studied the tree species Ceiba trichistandra (leaf deciduous, stem succulent), Eriotheca ruizii (leaf deciduous, root succulent) and Erythrina velutina (leaf deciduous). Reversible stem swelling and shrinking was observed for all three species during the whole study period and at all positions at the altitudinal gradient. However, it was most pronounced and sensitive in the stem succulent C. trichistandra and at the lowest (driest) position. C. trichistandra flushed leaves at dry season intermittent rain events, and from dry to wet season leaf out was earlier, and in this period sap flux was high while stem circumference decreased. Length of the leaved periods of all species increased with altitude. Thus, clear differences among species, topographic positions, radial growth and tree water use patterns are revealed; especially C. trichistandra responded very sensitive to fluctuating moisture regimes with leaf phenology, sap flux and stem diameter variations, and can be regarded as a sensitive indicator for assessing climatic variations.
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Keywords: |
Ecuador |
Phenology |
Elevation gradient |
Sap flux |
Seasonality |
Tree indicator |
Tiede, Y.; Schlautmann, J.; Donoso, D.A.; Wallis, C.; Bendix, J.; Brandl, R. & Farwig, N. (2017): Ants as indicators of environmental change and ecosystem processes. Ecological indicators 1(1), 1-6.
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DOI: 10.1016/j.ecolind.2017.01.029
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Abstract:
Abstract:
Environmental stressors and changes in land use have led to rapid and dramatic species losses. As such, we need effective monitoring programs that alert us not only to biodiversity losses, but also to functional changes in species assemblages and associated ecosystem processes. Ants are important components of terrestrial food webs and a key group in food web interactions and numerous ecosystem processes. Their sensitive and rapid response to environmental changes suggests that they are a suitable indicator group for the monitoring of abiotic, biotic, and functional changes. We tested the suitability of the incidence (i.e. the sum of all species occurrences at 30 baits), species richness, and functional richness of ants as indicators of ecological responses to environmental change, forest degradation, and of the ecosystem process predation on herbivorous arthropods. We sampled data along an elevational gradient (1000–3000 m a.s.l.) and across seasons (wetter and drier period) in a montane rainforest in southern Ecuador. The incidence of ants declined with increasing elevation but did not change with forest degradation. Ant incidence was higher during the drier season. Species richness was highly correlated with incidence and showed comparable results. Functional richness also declined with increasing elevation and did not change with forest degradation. However, a null-model comparison revealed that the functional richness pattern did not differ from a pattern expected for ant assemblages with randomly distributed sets of traits across species. Predation on artificial caterpillars decreased along the elevational gradient; the pattern was not driven by elevation itself, but by ant incidence (or inter-changeable by ant richness), which positively affected predation. In spite of lower ant incidence (or ant richness), predation was higher during the wetter season and did not change with forest degradation and ant functional richness. We used path analysis to disentangle the causal relationships of the environmental factors temperature (with elevation as a proxy), season, and habitat degradation with the incidence and functional richness of ants, and their consequences for predation. Our results would suggest that the forecasted global warming might support more active and species-rich ant assemblages, which in turn would mediate increased predation on herbivorous arthropods. However, this prediction should be made with reservation, as it assumes that the dispersal of ants keeps pace with the climatic changes as well as a one-dimensional relationship between ants and predation within a food-web that comprises species interactions of much higher complexity. Our results also suggested that degraded forests in our study area might provide suitable habitat for epigaeic, ground-dwelling ant assemblages that do not differ in incidence, species richness, functional richness, composition, or predation on arthropods from assemblages of primary forests. Most importantly, our results suggest that the occurrence and activity of ants are important drivers of ecosystem processes and that changes in the incidence and richness of ants can be used as effective indicators of responses to temperature changes and of predation within mega-diverse forest ecosystems.
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Keywords: |
elevational gradient |
species traits |
forest degradation |
path model |
artificial caterpillars |
functional richness |
Farwig, N.; Bendix, J. & Beck, E. (2017): Introduction to the Special Issue “Functional monitoring in megadiverse tropical ecosystems”. Ecological indicators 1(1), 1-3.
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DOI: 10.1016/j.ecolind.2017.02.027
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Abstract:
Abstract:
Land-use and climate change are major threats to biodiversity and ecosystem functions. Most of the current biodiversity monitoring systems are based on periodic records of the populations of a set of threatened or popular ‘flagship’ indicator species. In contrast to the abundance-based monitoring of species, also specific indicators of processes and functional interactions in an ecosystem may become targets of a more functional monitoring which can unveil early responses of an ecosystem to environmental changes at different spatial and temporal scales. The contributions of this Special Issue present such functional indicators for assessing and predicting responses to environmental changes of ecosystem functions in a hotspot of tropical biodiversity.
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Keywords: |
Ecuador |
ecosystem services |
Biodiversity |
ecosystem functions |
global change effects |
functional monitoring systems |
Paul, C.; Weber, M. & Knoke, T. (2017): Agroforestry versus farm mosaic systems – Comparing land-use efficiency, economic returns and risks under climate change effects. Science of The Total Environment online , online.
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DOI: 10.1016/j.scitotenv.2017.02.037
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Abstract:
Abstract:
Increasing land-use conflicts call for the development of land-use systems that reconcile agricultural production with the provisioning of multiple ecosystem services, including climate change mitigation. Agroforestry has been suggested as a global solution to increase land-use efficiency, while reducing environmental impacts and economic risks for farmers. Past research has often focused on comparing tree-crop combinations with agricultural monocultures, but agroforestry has seldom been systematically compared to other forms of land-use diversification, including a farm mosaic. This form of diversification mixes separate parcels of different land uses within the farm. The objective of this study was to develop a modelling approach to compare the performance of the agroforestry and farm mosaic diversification strategies, accounting for tree-crop interaction effects and economic and climate uncertainty. For this purpose, Modern Portfolio Theory and risk simulation were coupled with the process-based biophysical simulation model WaNuLCAS 4.0. For an example application, we used data from a field trial in Panama. The results show that the simulated agroforestry systems (Taungya, alley cropping and border planting) could outperform a farm mosaic approach in terms of cumulative production and return. Considering market and climate uncertainty, agroforestry showed an up to 21% higher economic return at the same risk level (i.e. standard deviation of economic returns). Farm compositions with large shares of land allocated to maize cultivation were also more severely affected by an increasing drought frequency in terms of both risks and returns. Our study demonstrates that agroforestry can be an economically efficient diversification strategy, but only if the design allows for economies of scope, beneficial interactions between trees and crops and higher income diversification compared to a farm mosaic. The modelling approach can make an important contribution to support land-use decisions at the farm level and reduce land-use conflicts at the landscape level.
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Keywords: |
climate change |
Agroforestry |
land use modeling |
Economics |
Paul, C. & Knoke, T. (2016): Forest value: More than commercial. Science 354(6319), 1541-1541.
Strobl, S.; Cueva, E.; Silva, B.; Knüsting, J.; Schorsch, M.; Scheibe, R.; Bendix, J. & Beck, E. (2016): Water relations and photosynthetic water use efficiency as indicators of slow climate change effects on trees in a tropical mountain forest in South Ecuador. Ecological Indicators xxx, xxx-xxx.
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DOI: 10.1016/j.ecolind.2016.12.021
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Abstract:
Abstract:
The effects of an increasing moisture on trees of the tropical species-rich mountain rain forest in the South Ecuadorian Andes was investigated, using the daily total water consumption (TWC) and the instantaneous water use efficiency (WUE, ratio of photosynthetic CO2 uptake per water loss by transpiration) as ecophysiological indicators. Two canopy and one sub-canopy tree species, (Vismia tomentosa, Clusiaceae, an as of yet unknown Lauracee, and Spirotheca rosea, Bombacaceae) were the experimental objects. Seasonal changes as well as a long-term (18 months) trend of increasing precipitation caused an inverse reaction of the TWC of the trees. Because of a rather unlimited water supply to the trees from a permanently high water content of the soil, transpiration followed mainly the atmospheric demand of water vapor, and increasing moisture hence reduced water loss by transpiration. It was hypothesized that in spite of the reduction in transpiratory water loss photosynthetic carbon acquisition would be not or less affected due to an increase in water use efficiency. Concomitant measurements of photosynthetic net CO2 uptake showed the expected increase of WUE in V. tomentosa and S. rosea, but no clear reaction of the Lauracee. Accompanying measurements of stem extension growth confirmed an undiminished growth of V. tomentosa and S. rosea but showed also suspended growth of the Lauracee during the wettest months. While TWC can be continuously monitored with the heat dissipation technique, WUE is determined by leaf porometry in campaigns for which access to the canopy is required. Simultaneous recordings of the gas exchange of leaves at 4 different positions in the crown of one of the experimental trees (V. tomentosa) showed the usability of the trait WUE in combination with the total daily water consumption as indicator set for assessing the response of trees to a subtly changing climate. However, not all tree species appear as likewise useful indicator trees.
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Keywords: |
tropical trees |
physiological indicators |
water and carbon relations |
water use efficiency |
long and short term monitoring |
Tapia Armijos, M.F.; Homeier, J. & Draper Munt, D. (2016): Spatio-temporal analysis of the human footprint in South Ecuador: Influence of human pressure on ecosystems and effectiveness of protected areas. Applied Geography 78, 22-32.
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DOI: 10.1016/j.apgeog.2016.10.007
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Abstract:
Abstract:
Human influence and its impacts are perceptible in all ecosystems resulting in land transformation, changes in global biogeochemistry, climate change, and loss of biological diversity. Mapping the spatial and temporal patterns of human influence is essential to address land use management and conservation programs. In this study, we tailored the Human Footprint index (HF) developed at global level to evaluate
the spatial and temporal patterns of human pressure in South Ecuador for 1982, 1990 and 2008. Landscape and ecosystem levels were analyzed to identify the contribution of different human proxies to the HF.We also used the HF to evaluate the effectiveness of protected areas to reduce human pressure in the
surrounding landscape. We found that levels of human pressure increased and the wildest areas decreased since 1982. We identified important “hotspots of changes” in the seasonally dry forests in the western part and the premontane evergreen forest in the eastern part of the study area. Our results show that each human proxy contributes in a different way to the observed values of HF in the studied ecosystems.
Finally, we found that Podocarpus NP, the most important protected area in our study region, seems to be partially effective in reducing human pressure inside and in the buffer zones where only a low increase in HF was detected. However, the HF values observed in the surrounding landscape were higher than those observed in the buffer zone and inside the protected area. We demonstrated that HF could be a useful regional evaluation tool to facilitate conservation planning.
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Keywords: |
human disturbance |
Biodiversity conservation |
Podocarpus National park |
Rehmus, A.; Bigalke, M.; Boy, J.; Valarezo, C. & Wilcke, W. (2016): Aluminum cycling in a tropical montane forest ecosystem in southern Ecuador. Geoderma 288, 196-203.
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DOI: 10.1016/j.geoderma.2016.11.002
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Abstract:
Abstract:
Growth limitation induced by Al toxicity is believed to commonly occur in tropical forests, although a direct proof is frequently lacking. To test for the general assumption of Al toxicity, Al, Ca, and Mg concentrations in precipitation, throughfall, stemflow, organic layer leachate, mineral soil solutions, stream water, and the leaves of 17 native tree species were analyzed. We calculated Al fluxes and modeled Al speciation in the litter leachate and mineral soil solutions. We assessed potential Al toxicity based on soil base saturation, Al concentrations, Ca:Al and Mg:Al molar ratios and Al speciation in soil solution as well as Al concentrations and Ca:Al andMg:Al molar ratios in tree leaves. High Al fluxes in litterfall (8.77±1.3 to 14.2±1.9 kg ha?1 yr?1, mean ± SE) indicated a high Al circulation through the ecosystem. The fraction of exchangeable and
potentially plant-available Al in mineral soils was high, being a likely reason for a low root length density in
the mineral soil. However, Al concentrations in all solutions were consistently below critical values and
Ca:Al molar and the Ca2+:Alinorganic molar ratios in the organic layer leachate and soil solutions were above 1, the suggested threshold for Al toxicity. Except for two Al-accumulating and one non-accumulating tree species, the Ca:Al molar ratios in tree leaves were above the Al toxicity threshold of 12.5. Our results demonstrate high Al cycling through the vegetation partly because of the presence of some Al accumulator plants. However, there was little indication of an Al toxicity risk in soil and of acute Al toxicity in plants likely reflecting that tree species are well adapted to the environmental conditions at our study site and thus hardly prone to Al toxicity.
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Keywords: |
aluminum toxicity |
tropical forest ecosystems |
aluminum fluxes |
aluminum speciation |
molar Ca:Al ratios |
Bendix, J. & Beck, E. (2016): Environmental Change And Its Impacts In A Biodiversity Hotspot Of The South Ecuadorian Andes–Monitoring And Mitigation Strategies. Erdkunde 70(1), 1-4.
Rollenbeck, R.; Trachte, K. & Bendix, J. (2016): A New Class of Quality Controls for Micrometeorological Data in Complex Tropical Environments. Journal of Atmospheric and Oceanic Technology 33(1), 169-183.
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DOI: 10.1175/JTECH-D-15-0062.1
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Abstract:
Abstract:
Quality control is a particularly demanding problem for micrometeorological studies in complex environments. With the transition to electronic sensing and storage of climate data in high temporal resolution,
traditional approaches of homogenization are insufficient for addressing the small-scale variability and spatial
heterogeneity of the data. This problem can be successfully addressed by introducing a new class of control
procedures based on the physical and climatological relations between different climate variables. The new
approach utilizes knowledge about the interdependency of air temperature, precipitation, radiation, relative
air humidity, cloud cover, and visibility to develop empirical functions for determining the probability
margins for the co-occurrence of specific conditions in tropical mountains and deserts. It can also be applied to
other geographic settings by adjusting the parameters derived from the data itself. All procedures are integrated into a processing chain with feedback loops and combined with conventional logical and statistical
checks, which enables it to detect small errors that normally pass unnoticed. The algorithms are also adapted
to incorporate the short time steps of the original data to retain the potential for detailed process analyses.
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Keywords: |
climate |
microclimate |
Climate variability |
data quality |
Gonzalez, V.; Fries, A.; Rollenbeck, R.; Paladines, J.; Oñate-Valivieso, F. & Bendix, J. (2016): Assessment of deforestation during the last decades in Ecuador using NOAA-AVHRR satellite data. Erdkunde 70(No. 3), 217-235.
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DOI: 10.3112/erdkunde.2016.03.02
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Abstract:
Abstract:
Human activities during the last decades provoked a notable reduction in global forest cover. Knowing that
forest stands act as stock and sinks for carbon and other greenhouse gases, it is important to determine the existing forest
cover at country level and to calculate annual deforestation rates. This work uses NOAAsatellite images in a resolution of
1 km x 1 km to classify the surface of continental Ecuador in “forest” – “non-forest” pixels and to estimate the annual
deforestation rate from 1986 to 2001 as well as from 2001 to 2008. The method is based on a decision tree algorithm that
includes different spectral bands of the NOAA-AVHRRsensor and additional topographic and meteorological parameters.
The results show that the total forest cover of continental Ecuador was reduced from 48.1 % in 1986 to 36.8 % in 2008. The
calculated annual deforestation rates indicate that forest reduction increased during the last decade. The most affected area
is the Coastal Lowland, due to the enhanced population pressure, followed by the Amazon Basin, not only caused by the
governmental supported oil and mining industry, but also due to the uncontrolled timber extraction. The Andean Highland
has been less affected, because the major parts of this region were deforested before, during the Pre-Columbian-Era.
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Keywords: |
Ecuador |
NOAA-AVHRR |
remote sensing |
deforestation |
image pre-processing |
forest cover |
Makowski Giannoni, S.; Trachte, K.; Rollenbeck, R.; Lehnert, L.; Fuchs, J. & Bendix, J. (2016): Atmospheric salt deposition in a tropical mountain rainforest at the eastern Andean slopes of south Ecuador – Pacific or Atlantic origin?. Atmospheric chemistry and physics 16, 10241-10261.
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DOI: 10.5194/acp-16-10241-2016
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Abstract:
Abstract:
Sea salt (NaCl) has recently been proven to be of the utmost importance for ecosystem functioning in Amazon lowland forests because of its impact on herbivory, litter decomposition and, thus, carbon cycling. Sea salt deposition should generally decline as distance from its marine source increases. For the Amazon, a negative east–west gradient of sea salt availability is assumed as a consequence of the barrier effect of the Andes Mountains for Pacific air masses. However, this generalized pattern may not hold for the tropical mountain rainforest in the Andes of southern Ecuador. To analyse sea salt availability, we investigated the deposition of sodium (Na+) and chloride (Cl?), which are good proxies of sea spray aerosol. Because of the complexity of the terrain and related cloud and rain formation processes, sea salt deposition was analysed from both, rain and occult precipitation (OP) along an altitudinal gradient over a period between 2004 and 2009. To assess the influence of easterly and westerly air masses on the deposition of sodium and chloride over southern Ecuador, sea salt aerosol concentration data from the Monitoring Atmospheric Composition and Climate (MACC) reanalysis data set and back-trajectory statistical methods were combined. Our results, based on deposition time series, show a clear difference in the temporal variation of sodium and chloride concentration and Na+???Cl? ratio in relation to height and exposure to winds. At higher elevations, sodium and chloride present a higher seasonality and the Na+???Cl? ratio is closer to that of sea salt. Medium- to long-range sea salt transport exhibited a similar seasonality, which shows the link between our measurements at high elevations and the sea salt synoptic transport. Although the influence of the easterlies was predominant regarding the atmospheric circulation, the statistical analysis of trajectories and hybrid receptor models revealed a stronger impact of the north equatorial Atlantic, Caribbean, and Pacific sea salt sources on the atmospheric sea salt concentration in southern Ecuador. The highest concentration in rain and cloud water was found between September and February when air masses originated from the north equatorial Atlantic, the Caribbean Sea and the equatorial Pacific. Together, these sources accounted for around 82.4?% of the sea salt budget over southern Ecuador.
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Keywords: |
chloride |
sodium |
rain |
Nutrient deposition |
Occult precipitation |
transport modelling |
Back trajectories |
Correa, A.; Windhorst, D.; Crespo, P.; Celleri, R.; Feyen, J. & Breuer, L. (2016): Continuous versus event based sampling: How many samples are required for deriving general hydrological understanding on Ecuador's páramo region?. Hydrological Processes 30(22), 4059-4073.
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DOI: 10.1002/hyp.10975
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Abstract:
Abstract:
As a consequence of the remote location of the Andean páramo is knowledge on their hydrologic functioning limited, notwithstanding this alpine tundra ecosystem act as water towers for a large fraction of the society. Given the harsh environmental conditions in this region is year-round monitoring cumbersome, and it would be beneficially if the monitoring needed for the understanding of the rainfall-runoff response could be limited in time. To identify the hydrological response and the effect of temporal monitoring a nested (n?=?7) hydrological monitoring network was set up in the Zhurucay catchment (7.53?km2), south Ecuador. The research questions were: (1) can event sampling provide similar information in comparison to continuous monitoring, and (2) if so, how many events are needed to achieve a similar degree of information? A subset of 34 rainfall runoff events was compared to monthly values derived from a continuous monitoring scheme from December 2010 to November 2013. Land cover and physiographic characteristics were correlated with eleven hydrological indices. Results show that despite some distinct differences between event and continuous sampling, both datasets reveal similar information; more in particular the monitoring of a single event in the rainy season provides the same information as continuous monitoring, while during the dry season 10 events ought to be monitored.
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Keywords: |
Paramo |
Andes |
hydrologic response |
catchment hydrology |
sampling design |
Mosquera, G.; Celleri, R.; Lazo, P.; Vaché, K.; Perakis, S. & Crespo, P. (2016): Combined use of isotopic and hydrometric data to conceptualize ecohydrological processes in a high-elevation tropical ecosystem. Hydrological Processes xxx, xxx.
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DOI: 10.1002/hyp.10927
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Abstract:
Abstract:
Few high-elevation tropical catchments worldwide are gauged, and even fewer are studied using combined hydrometric and isotopic data. Consequently, we lack information needed to understand processes governing rainfall–runoff dynamics and to predict their influence on downstream ecosystem functioning. To address this need, we present a combination of hydrometric and water stable isotopic observations in the wet Andean páramo ecosystem of the Zhurucay Ecohydrological Observatory (7.53?km2). The catchment is located in the Andes of south Ecuador between 3400 and 3900?m?a.s.l. Water samples for stable isotopic analysis were collected during 2?years (May 2011–May 2013), while rainfall and runoff measurements were continuously recorded since late 2010. The isotopic data reveal that andosol soils predominantly situated on hillslopes drain laterally to histosols (Andean páramo wetlands) mainly located at the valley bottom. Histosols, in turn, feed water to creeks and small rivers throughout the year, establishing hydrologic connectivity between wetlands and the drainage network. Runoff is primarily composed of pre-event water stored in the histosols, which is replenished by rainfall that infiltrates through the andosols. Contributions from the mineral horizon and the top of the fractured bedrock are small and only seem to influence discharge in small catchments during low flow generation (non-exceedance flows?<?Q35). Variations in source contributions are controlled by antecedent soil moisture, rainfall intensity, and duration of rainy periods. Saturated hydraulic conductivity of the soils, higher than the year-round low precipitation intensity, indicates that Hortonian overland flow rarely occurs during high-intensity precipitation events. Deep groundwater contributions to discharge seem to be minimal. These results suggest that, in this high-elevation tropical ecosystem, (1) subsurface flow is a dominant hydrological process and (2) (histosols) wetlands are the major source of stream runoff. Our study highlights that detailed isotopic characterization during short time periods provides valuable information about ecohydrological processes in regions where very few basins are gauged.
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Keywords: |
Andes |
hydrological processes |
isotopes |
ecohydrological processes; |
Mosquera, G.; Segura, C.; Vaché, K.; Windhorst, D.; Breuer, L. & Crespo, P. (2016): Insights into the water mean transit time in a high-elevation tropical ecosystem. Hydrology and Earth System Sciences (HESS) 20(7), 2987-3004.
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DOI: 10.5194/hess-20-2987-2016
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Abstract:
Abstract:
This study focuses on the investigation of the mean transit time (MTT) of water and its spatial variability in a tropical high-elevation ecosystem (wet Andean páramo). The study site is the Zhurucay River Ecohydrological Observatory (7.53?km2) located in southern Ecuador. A lumped parameter model considering five transit time distribution (TTD) functions was used to estimate MTTs under steady-state conditions (i.e., baseflow MTT). We used a unique data set of the ?18O isotopic composition of rainfall and streamflow water samples collected for 3 years (May 2011 to May 2014) in a nested monitoring system of streams. Linear regression between MTT and landscape (soil and vegetation cover, geology, and topography) and hydrometric (runoff coefficient and specific discharge rates) variables was used to explore controls on MTT variability, as well as mean electrical conductivity (MEC) as a possible proxy for MTT. Results revealed that the exponential TTD function best describes the hydrology of the site, indicating a relatively simple transition from rainfall water to the streams through the organic horizon of the wet páramo soils. MTT of the streams is relatively short (0.15–0.73 years, 53–264 days). Regression analysis revealed a negative correlation between the catchment's average slope and MTT (R2?=??0.78, p?<?0.05). MTT showed no significant correlation with hydrometric variables, whereas MEC increases with MTT (R2?=??0.89, p?<?0.001). Overall, we conclude that (1) baseflow MTT confirms that the hydrology of the ecosystem is dominated by shallow subsurface flow; (2) the interplay between the high storage capacity of the wet páramo soils and the slope of the catchments provides the ecosystem with high regulation capacity; and (3) MEC is an efficient predictor of MTT variability in this system of catchments with relatively homogeneous geology.
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Keywords: |
Paramo |
mean transit time |
hydrological processes |
Iniguez, C.; Rausche, S.; Cueva, A.; Sánchez-Rodríguez, A.; Espinosa, C. & Breuer, L. (2016): Shifts in leaf litter breakdown along a forest–pasture–urban gradient in Andean streams. Ecology and Evolution 6(14), 4849-4865.
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DOI: 10.1002/ece3.2257
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Abstract:
Abstract:
Tropical montane ecosystems of the Andes are critically threatened by a rapid land-use change which can potentially affect stream variables, aquatic communities, and ecosystem processes such as leaf litter breakdown. However, these effects have not been sufficiently investigated in the Andean region and at high altitude locations in general. Here, we studied the influence of land use (forest–pasture–urban) on stream physico-chemical variables (e.g., water temperature, nutrient concentration, and pH), aquatic communities (macroinvertebrates and aquatic fungi) and leaf litter breakdown rates in Andean streams (southern Ecuador), and how variation in those stream physico-chemical variables affect macroinvertebrates and fungi related to leaf litter breakdown. We found that pH, water temperature, and nutrient concentration increased along the land-use gradient. Macroinvertebrate communities were significantly different between land uses. Shredder richness and abundance were lower in pasture than forest sites and totally absent in urban sites, and fungal richness and biomass were higher in forest sites than in pasture and urban sites. Leaf litter breakdown rates became slower as riparian land use changed from natural to anthropogenically disturbed conditions and were largely determined by pH, water temperature, phosphate concentration, fungal activity, and single species of leaf-shredding invertebrates. Our findings provide evidence that leaf litter breakdown in Andean streams is sensitive to riparian land-use change, with urban streams being the most affected. In addition, this study highlights the role of fungal biomass and shredder species (Phylloicus; Trichoptera and Anchytarsus; Coleoptera) on leaf litter breakdown in Andean streams and the contribution of aquatic fungi in supporting this ecosystem process when shredders are absent or present low abundance in streams affected by urbanization. Finally, we summarize important implications in terms of managing of native vegetation and riparian buffers to promote ecological integrity and functioning of tropical Andean stream ecosystems.
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Keywords: |
stream water |
decomposition |
Aquatic Pollution |
Ochoa Moreno, S.; Paul, C. & Knoke, T. (2016): Warum Kleinbauern in Ecuador die Landnutzung diversifizieren. Allgemeine Forst Zeitschrift für Waldwirtschaft und Umweltvorsorge 71(13), 31-34.
Schlaeppi, K.; Bender, S.F.; Mascher, F.; Russo, G.; Patrignani, A.; Camenzind, T.; Hempel, S.; Rillig, M.C. & van der Heijden, M.G. (2016): High-resolution community profiling of arbuscular mycorrhizal fungi. New Phytologist xx, xx.
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DOI: 10.1111/nph.14070
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Abstract:
Abstract:
Summary
Community analyses of arbuscular mycorrhizal fungi (AMF) using ribosomal small subunit
(SSU) or internal transcribed spacer (ITS) DNA sequences often suffer from low resolution or
coverage. We developed a novel sequencing based approach for a highly resolving and specific profiling of AMF communities.
We took advantage of previously established AMF-specific PCR primers that amplify a
c. 1.5-kb long fragment covering parts of SSU, ITS and parts of the large ribosomal subunit
(LSU), and we sequenced the resulting amplicons with single molecule real-time (SMRT)
sequencing.
The method was applicable to soil and root samples, detected all major AMF families and
successfully discriminated closely related AMF species, which would not be discernible using
SSU sequences. In inoculation tests we could trace the introduced AMF inoculum at the
molecular level. One of the introduced strains almost replaced the local strain(s), revealing
that AMF inoculation can have a profound impact on the native community.
The methodology presented offers researchers a powerful new tool for AMF community
analysis because it unifies improved specificity and enhanced resolution, whereas the drawback of medium sequencing throughput appears of lesser importance for low-diversity groups
such as AMF.
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Keywords: |
arbuscular mycorrhiza |
mycorrhiza |
Crowther, T. & et, a. (2015): Mapping tree density at a global scale. Nature 525(7568), 201-205.
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DOI: 10.1038/nature14967
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Abstract:
Abstract:
The global extent and distribution of forest trees is central to our understanding of the terrestrial biosphere. We provide the first spatially continuousmap of forest tree density at a global scale. This mapreveals that the global numberof trees is approximately 3.04 trillion, an order of magnitude higher than the previous estimate. Of these trees, approximately 1.39 trillion exist in tropical and subtropical forests, with 0.74 trillion in boreal regions and 0.61 trillion in temperate
regions. Biome-level trends in tree density demonstrate the importance of climate and topography in controlling local tree densities at finer scales, as well as the overwhelming effect of humans across most of the world. Based on our projected tree densities, we estimate that over 15 billion trees are cut down each year, and the global number of trees has fallen by approximately 46% since the start of human civilization.
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Keywords: |
tree density |
Slik, F. & et, a. (2015): An estimate of the number of tropical tree species. PNAS 112(24), 7472-7477.
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DOI: 10.1073/pnas.1423147112
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Abstract:
Abstract:
The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database
from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher’s alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ?40,000 and ?53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ?19,000–25,000 tree species. Continental Africa is relatively depauperate with a minimumof ?4,500–6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa.
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Keywords: |
tree species richness |
tree species |
Silva, B.; Strobl, S.; Beck, E. & Bendix, J. (2016): Canopy evapotranspiration, leaf transpiration and water use efficiency of an Andean pasture in SE-Ecuador – a case study. Erdkunde 70(1), 5-18.
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DOI: 10.3112/erdkunde.2016.01.02
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Abstract:
Abstract:
The relationship between canopy-level evapotranspiration (ETSci) and leaf-level transpiration (Tleaf) as well as photosynthesis (Pleaf) for a homogeneous tropical montane pasture was analyzed over five days using a combination of methods involving a laser scintillometer and a porometer. Weather conditions ranged from overcast to sunny during the period of study. The gas exchange of the leaves of the dominant pasture grass Setaria sphacelata (transpiration vs. photosyn¬thetic CO2 net uptake ) was measured with a porometer and physiologically interpreted on the background of microclimate variables (photosynthetic active radiation (PAR) as proxy for total light intensity, temperature, water vapor deficit of the air) and soil moisture data. Water use efficiency (WUE, photosynthetic CO2 net uptake vs water loss by leaf transpiration) of the pasture was used to analyze the grass’ range of response to the environmental variables of the research area. PAR and water vapor deficit of the air (VPD) appeared to be the determinant factors for Tleaf and ETSci. WUE for the Setaria sphacelata pasture ranged from 1.9 to 5.8 ?mol CO2 mmol-1 H20 day-1 and is particularly low during periods of high VPD combined with enhanced insolation during cloudless periods. ET measurements collected by the scintillometer demonstrated a strong correlation with water flux calculated using the Penman-Monteith approach (TPM) (r² = 0.95). Also, Tleaf measured with the porometer showed reasonable coincidence with the ET observations (r² = 0.78). Values of ETSci ranged from 2.26 to 4.96 mm day-1 and Tleaf ranged from 0.83 to 2.41 mm day-1, but only ETSci showed good correspondence with the available energy (net radiation). The lower correlation between Tleaf and canopy-level ETSci compared to that between ETSci and TPM was tested against contaminations from the adjacent fetch area of the scintillometer path, but no effects were found. Likewise, soil water limitations of Tleaf could be ruled out. Therefore, different correlations of ETSci and Tleaf with the incoming energy and VPD may be traced back to a direct effect of the VPD on ET in contrast to its indirect effect on Tleaf which is additionally regulated by physiological processes in the leaf stomata.
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Keywords: |
Porometry |
Setaria |
Evapotranspiration |
scintillometry |
Adams, M. & Fiedler, K. (2016): Low Herbivory among Targeted Reforestation Sites in the Andean Highlands of Southern Ecuador.. PLoS ONE 11(3), e0151277.
Adams, M. & Fiedler, K. (2015): The value of targeted reforestations for local insect diversity: a case study from the Ecuadorian Andes.. Biodiversity and Conservation 24, 2709-2734.
Kübler, D.; Hildebrandt, P.; Günter, S.; Stimm, B.; Weber, M.; Mosandl, R.; Munoz, J.; Cabrera, O.; Aguirre, N.; Zeilinger, J. & Silva, B. (2016): Assessing the importance of topographic variables for the spatial distribution of tree species in a tropical mountain forest. Erdkunde 70(1), 19-47.