Publikationen
Es wurden 505 Publikationen gefunden
- vom Typ: article
Ermilov, S.; Stary, J.; Sandmann, D.; Marian, F. & Maraun, M. (2013): New taxa and new records of oribatid mites of the family Galumnidae (Acari: Oribatida) from Ecuador. Zootaxa 3700, 259–270.
Ermilov, S.; Sandmann, D.; Marian, F. & Maraun, M. (2013): Two new oribatid mite species of the genus Gittella from Ecuador (Acari, Oribatida, Oppiidae). Spixiana 36, 1-8.
Ermilov, S.; Sandmann, D.; Marian, F. & Maraun, M. (2013): Perscheloribates paratzitzikamensis n. sp., with supplementary description of Scheloribates elegans and Monoschelobates parvus (Acari, Oribatida, Scheloribatidae) from Ecuador. Acarologia 53, 429–437.
Ermilov, S.; Sandmann, D.; Marian, F. & Maraun, M. (2013): Oribatid mites of the superfamily Oppioidea from Ecuador (Acari: Oribatida). Systematic and Applied Acarology 18, 218-224.
Ermilov, S.; Bayartogtokh, B.; Sandmann, D.; Marian, F. & Maraun, M. (2013): New and little known species of oribatid mites of the family Haplozetidae (Acari, Oribatida) from Ecuador. Zookeys 346, 43-57.
Ermilov, S.; Sandmann, D. & Maraun, M. (2013): A new species of the genus Orthozetes from Ecuador (Acari: Oribatida: Microzetidae). Acarina 21, 100-103.
Jacquemin, J.; Delsinne, T.; Maraun, M. & Leponce, M. (2014): Trophic ecology of the armadillo ant Tatuidris tatusia assessed by stable isotopes and behavioral observations. Journal of Insect Science 14, 18.
Ermilov, S.; Marian, F. & Maraun, M. (2014): Two new species of Ecuadorian oribatid mites of the genera Hermannobates and Rhynchoribates (Acari Oribatida: Hermanniellidae, Rhynchoribatidae). Systematic and Applied Acarology 19, 313-324.
Tischer, A.; Potthast, K. & Hamer, U. (2014): Land use and soil depth affect resource and microbial stoichiometry in a tropical mountain rainforest region of southern Ecuador. Oecologia 175, 375-393.
Tischer, A.; Potthast, K. & Hamer, U. (2014): Land?use and soil depth affect resource and microbial stoichiometry in a tropical mountain rainforest region of southern Ecuador. Oecologia 175, 375-393.
Tischer, A.; Blagodatskaya, E. & Hamer, U. (2013): Extracellular enzyme activities in a tropical mountain rainforest region of southern Ecuador affected by low soil P status and land-use change. Applied Soil Ecology 74, 1-11.
Timbe, E.; Windhorst, D.; Celleri, R.; Timbe, L.; Crespo, P.; Frede, H.; Feyen, J. & Breuer, L. (2015): Sampling frequency trade-offs in the assessment of mean transit times of tropical montane catchment waters under semi-steady-state conditions. Hydrology and Earth System Sciences 19(3), 1153-1168.
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DOI: 10.5194/hess-19-1153-2015
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Abstract:
Abstract:
Precipitation event samples and weekly based water samples from streams and soils were collected in a tropical montane cloud forest catchment for 2 years and analyzed for stable water isotopes in order to understand the effect of sampling frequency in the performance of three lumped-parameter distribution functions (exponential-piston flow, linear-piston flow and gamma) which were used to estimate mean transit times of waters. Precipitation data, used as input function for the models, were aggregated to daily, weekly, bi-weekly, monthly and bi-monthly sampling resolutions, while analyzed frequencies for outflows went from weekly to bi-monthly. By using different scenarios involving diverse sampling frequencies, this study reveals that the effect of lowering the sampling frequency depends on the water type. For soil waters, with transit times on the order of few weeks, there was a clear trend of over predictions.
In contrast, the trend for stream waters, which have a more damped isotopic signal and mean transit times on the order of 2 to 4 years, was less clear and showed a dependence on the type of model used. The trade-off to coarse data resolutions could potentially lead to misleading conclusions on how water actually moves through the catchment, notwithstanding that these predictions could reach better fitting efficiencies, fewer uncertainties, errors and biases. For both water types an optimal sampling frequency seems to be 1 or at most 2
weeks. The results of our analyses provide information for the planning of future fieldwork in similar Andean or other catchments.
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Keywords: |
hydrology |
isotope tracers |
Krashevska, V.; Sandmann, D.; Maraun, M. & Scheu, S. (2012): Consequences of exclusion of precipitation on microorganisms and microbial consumers in montane tropical rainforests.. Oecologia 170, 1067-1076.
Krashevska, V.; Sandmann, D.; Maraun, M. & Scheu, S. (2014): Moderate changes in nutrient input alter tropical microbial and protist communities and belowground linkages. . The ISME Journal 8, 1126-1134.
Butenschoen, O.; Krashevska, V.; Maraun, M.; Marian, F.; Sandmann, D. & Scheu, S. (2014): Litter mixture effects on decomposition in tropical montane rainforests vary strongly with time and turn negative at later stages of decay. . Soil Biology and Biochemistry 77, 121-128.
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DOI: 10.1016/j.soilbio.2014.06.019
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Abstract:
Abstract:
In a litterbag study in a tropical montane rainforest in Ecuador we assessed the impact of leaf litter species identity and richness on decomposition. We incubated leaf litter of six native tree species in monocultures and all possible two and four species combinations and analysed mass loss over a period of 24 months. Mass loss in monocultures averaged 30.7% after 6 month and differed significantly between species with variations being closely related to initial concentrations of lignin, Mg and P. At later harvests mass loss in monocultures averaged 54.5% but did not vary among leaf litter species and, unexpectedly, did not increase between 12 and 24 months suggesting that litter converged towards an extremely poor common quality retarding decomposition. After 6 months mass loss of leaf litter species was significantly faster in mixtures than in monocultures, resulting in synergistic non-additive mixture effects on decomposition, whereas at later harvests mass loss of component litter species was more variable and leaf litter mixture effects differed with species richness. Mass loss in the two species mixtures did not deviate from those predicted from monocultures, while we found antagonistic non-additive mixture effects in the four species mixtures. This suggests that litter species shared a poor common quality but different chemistry resulting in negative interactions in chemically diverse litter mixtures at later stages of decomposition. Overall, the results suggest that interspecific variations in diversity and composition of structural and secondary litter compounds rather than concentrations of individual litter compounds per se, control long term leaf litter decomposition in tropical montane rainforests. Plant species diversity thus appears to act as a major driver for decomposition processes in tropical montane rainforest ecosystems, highlighting the need for increasing plant conservation efforts to protect ecosystem functioning of this threatened biodiversity hotspot.
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Keywords: |
litter decomposition |
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 |
Herrera, P.; Suarez, J.P. & Kottke, I. (2010): Orchids keep the ascomycetes outside: a highly diverse group of ascomycetes colonizing the velamen of epiphytic orchids from a tropical mountain rainforest in Southern Ecuador. Mycology 1(4), 262-268.
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DOI: 10.1080/21501203.2010.526645
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Abstract:
Abstract:
Orchid mycorrhizal detection, based only on fungal isolation from roots, is biased due to difficulties in isolating the respec- tive fungi. Previous investigations have shown that mostly ascomycetes, housed in the sheltered compartment of the vela- men covering the roots of epiphytic orchids, are isolated on agar plates. Roots of 83 individual epiphytic orchid of Stelis hallii, S. superbiens, S. concinna, Stelis sp. and Pleurothallis lilijae were sampled in the Reserva Biológica San Francisco, Southern Ecuador. The velamen was partly removed and root tissue macerated and transferred to Petri dishes containing corn meal agar, malt extract agar and Melin Norkrans modified medium. DNA was extracted from the cultures and the 5.8S-ITS region and partial nrLSU sequenced. Phylogenetic analysis revealed members of 12 orders of ascomycetes associ- ated with the roots of these orchids, a much higher diversity than previously known. Twelve isolates were related to the Helotiales. Our results have uncovered some of the fungal diversity within the velamen of epiphytic orchids; fungi invading, most likely, from tree bark or humus accumulation close to the roots.
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Keywords: |
neotropical mountain rain forest |
ascomycota |
epiphytic orchids |
velamen |
Helotiales |
Castro, L.M.; Calvas, B. & Knoke, T. (2015): Ecuadorian Banana Farms Should Consider Organic Banana with Low Price Risks in Their Land-Use Portfolios. PlOS one 10(3), e0120384.
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DOI: 10.1371/journal.pone.0120384
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Abstract:
Abstract:
Organic farming is a more environmentally friendly form of land use than conventional agriculture. However, recent studies point out production tradeoffs that often prevent the adoption of such practices by farmers. Our study shows with the example of organic banana production in Ecuador that economic tradeoffs depend much on the approach of the analysis. We test, if organic banana should be included in economic land-use portfolios, which indicate how much of the land is provided for which type of land-use. We use time series data for productivity and prices over 30 years to compute the economic return (as annualized net present value) and its volatility (with standard deviation as risk measure) for eight crops to derive land-use portfolios for different levels of risk, which maximize economic return. We find that organic banana is included in land-use portfolios for almost every level of accepted risk with proportions from 1% to maximally 32%, even if the same high uncertainty as for conventional banana is simulated for organic banana. A more realistic, lower simulated price risk increased the proportion of organic banana substantially to up to 57% and increased annual economic returns by up to US$ 187 per ha. Under an assumed integration of both markets, for organic and conventional banana, simulated by an increased coefficient of correlation of economic return from organic and conventional banana (? up to +0.7), organic banana holds significant portions in the land-use portfolios tested only, if a low price risk of organic banana is considered. We conclude that uncertainty is a key issue for the adoption of organic banana. As historic data support a low price risk for organic banana compared to conventional banana, Ecuadorian farmers should consider organic banana as an advantageous land-use option in their land-use portfolios.
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Keywords: |
land diversification |
agriculture |
land use modeling |
Cruz, D.; Suarez, J.P.; Kottke, I. & Piepenbring, M. (2014): Cryptic species revealed by molecular phylogenetic analysis of sequences obtained from basidiomata of Tulasnella. . Mycologia 106(4), 708-722.
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DOI: 10.3852/12-386
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Abstract:
Abstract:
Delimitation of species and the search for a proper threshold for defining phylogenetic species in fungi are under discussion. In this study, morpho- logical and molecular data are correlated to delimit species of Tulasnella, the most important mycobionts of Orchidaceae, which suffer from poor taxonomy. Resupinate basidiomata of Tulasnella species were collected in Ecuador and Germany, and 11 specimens (seven from Ecuador, four from Germany) were assigned to traditional species concepts by use of morphological keys. The specimens were compared by micro-anatomical examination with 75 specimens of Tulasnella borrowed from fungaria to obtain better insights on variation of characters. Sequences of the ITS region (127) were obtained after cloning from the fresh basidiomata and from pure cultures. Proportional variability of ITS sequences was analyzed within and among the cultures and the specimens designated to different morphospecies. Results sug- gested an intragenomic variation of less than 2%, an intraspecific variation of up to 4% and an interspe- cific divergence of more than 9% in Tulasnella. Cryptic species in Tulasnella, mostly from Ecuador, were revealed by phylogenetic analyses with 4% intraspecific divergence as a minimum threshold for delimiting species. Conventional diagnostic morpho- logical characters appeared insufficient for species characterization. Arguments are presented for molec- ular delimitation of the established species Tulasnella
albida, T. asymmetrica, T. eichleriana, T. cf. pinicola, T. tomaculum and T. violea.
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Keywords: |
interspecific divergence |
intragenomic variability |
intraspecific variability |
morphospecies |
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 |
Paul, C. & Knoke, T. (2015): Between land sharing and land sparing – what role remains for forest management and conservation?. International Forestry Review 17(2), 210-230.
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Conflicts between satisfying the growing global demand for food and energy and simultaneously preserving natural ecosystems have spurred renewed debate about how to optimise future land use. This study reviews the role of forests and forest management within these proposed land-use strategies and reveals that discussions about future management of forest and agricultural lands take place largely exclusive of one another. Based on these results, a land-use concept is proposed in which sustainable agricultural intensification is paired with land-use diversification as a risk reduction strategy and complemented by productive restoration and compensation payments for forest conservation. Improving afforestation and agroforestry practices on degraded lands and investigating effects of diversification on the landscape scale are identified as important objectives for future interdisciplinary research. Considering forests as part of a comprehensive land-use portfolio will be vital in order to help strengthen links and ease conflicts between forest and agricultural land uses.
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Keywords: |
sustainable land use |
indirect land use change (ILUC) |
natural forest management |
Rehmus, A.; Bigalke, M.; Valarezo, C.; Mora Castillo, J.R. & Wilcke, W. (2015): Aluminium toxicity to tropical montane forest tree seedlings in southern Ecuador: Response of the nutrient status to elevated Al concentrations. Plant and Soil 388, 87-97.
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DOI: 10.1007/s11104-014-2276-5
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Abstract:
Abstract:
Aims We determined the reasons why in nutrient solution increasing Al concentrations>300 ?M inhibited
shoot biomass production of Cedrela odorata L., Heliocarpus americanus L., and Tabebuia chrysantha
(Jacq.) G. Nicholson while 300 ?M Al stimulated root biomass production of Tabebuia chrysantha.
Methods Nutrient concentrations in plant tissue after a hydroponic growth experiment were determined.
Results Increasing Al concentrations significantly decreased Mg concentrations in leaves. Phosphorus
concentrations in roots of C. odorata and T. chrysantha were significantly highest in the treatment with 300 ?M Al and correlated significantly with root biomass.
Conclusions Shoot biomass production was likely inhibited by reduced Mg uptake, impairing photosynthesis.
The stimulation of root growth at low Al concentrations can be possibly attributed to improved P uptake.
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Keywords: |
phosphorus |
aluminum toxicity |
tropical forest tree seedling |
nutrient deficiency |
growth stimulation |
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.
Kotowska, M. & Werner, F.A. (2013): Environmental controls over methane emissions from bromeliad phytotelmata: The role of phosphorus and nitrogen availability, temperature, and water content. GLOBAL BIOGEOCHEMICAL CYCLES 27, 1-8.
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DOI: 10.1002/2013GB004612
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Abstract:
Abstract:
Tank bromeliads are common epiphytic plants throughout neotropical forests that store
signi?cant amounts of water in phytotelmata (tanks) formed by highly modi?ed leafs.
Methanogenic archaea in these tanks have recently been identi?ed as a signi?cant source of
atmospheric methane. We address the effects of environmental drivers (temperature, tank
water content, sodium phosphate [P], and urea [N] addition) on methane production in
anaerobically incubated bromeliad slurry and emissions from intact bromeliad tanks in
montane Ecuador. N addition ? 1 mg g 1 had a signi?cantly positive effect on headspace
methane concentrations in incubation jars while P addition did not affect methane
production at any dosage (? 1 mg g 1 ). Tank bromeliads (Tillandsia complanata) cultivated
in situ showed signi?cantly increased ef?uxes of methane in response to the addition of
26 mg N addition per tank but not to lower dosage of N or any dosage of P (? 5.2 mg plant 1 ).
There was no signi?cant interaction between N and P addition. The brevity of the
stimulatory effect of N addition on plant methane ef?uxes (1–2 days) points at N
competition by other microorganisms or bromeliads. Methane ef?ux from plants closely
followed within-day temperature ?uctuations over 24 h cycles, yet the dependency of
temperature was not exponential as typical for terrestrial wetlands but instead linear. In
simulated drought, methane emission from bromeliad tanks was maintained with minimum
amounts of water and regained after a short lag phase of approximately 24 h. Our results
suggest that methanogens in bromeliads are primarily limited by N and that direct effects of
global change (increasing temperature and seasonality, remote fertilization) on bromeliad
methane emissions are of moderate scale.
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Keywords: |
nutrients |
gas emission |
NUMEX |
N-cycle |
nitrogen |
Gas exchange |
phosphorus |
nutrient manipulation |
nutrient limitation |
phosphorus availability |
nutrient cycle |
methane |
Astudillo Webster, P.X.; Universidad del Azuay; Samaniego, G.M.; Machado, P.J.; Aguilar, J.M.; Tinoco, B.A.; Graham, C.H.; Stony Brook University; Latta, S.C.; National Aviary (USA) & Farwig, N. (2014): Der Einfluss von Straßen auf die Avifauna von Paramo Grasland im Cajas Nationalpark, Ecuador. Studies on Neotropical Fauna and Environment 49(3), 204-212.
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DOI: 10.1080/01650521.2014.960778
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Abstract:
Abstract:
National parks are an important tool for conserving biodiversity, particularly in areas of high biodiversity and endemism such as the tropical Andes. However, national parks often face a variety of stressors related to recreation, road construction and illegal extraction of natural resources. Unfortunately, the influence of these stressors for biodiversity is rarely well documented. Cajas National Park in Ecuador is no exception. Despite being traversed by the Cuenca-Molleturo-Naranjal road, effects of the road construction on biodiversity have not been determined. We therefore assessed the influence of road proximity on bird species richness and abundance as well as composition of bird habitat groups in Cajas National Park using transect walks at 25 m and 250 m distance to the road (overall 18 transects, each 1 km length). In total, we recorded 1110 individuals of 28 páramo bird species. Overall species richness did not differ between transects near and far from the road. Nevertheless, the average abundance of shrubby páramo species was significantly higher far from the road than near the road (Far = 36, Near = 25). Moreover, we found a tendency towards differences in the composition of bird habitat groups between transects near and far from the road. One aspect potentially driving the observed patterns was the increasing proportion of planted non-native woody tree species within páramo grassland near the road, which may have caused reduced abundances of shrubby páramo bird species there. While roads represented a clear impact on the composition of bird species in the páramo, the major effect seems to be driven by the introduction of non- native plant species along the roadside. In order to reduce the impact of roads to a minimum, we suggest that park managers should control the introduction of such plant species.
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Keywords: |
Paramo |
species richness |
abundance |
bird community |
stressors |
Cajas National Park |
road impact |
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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Abstract:
Abstract:
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 |
Exbrayat, J.F.; Buytaert, W.; Timbe, E.; Windhorst, D. & Breuer, L. (2014): Addressing sources of uncertainty in runoff projections for a data scarce catchment in the Ecuadorian Andes. Climatic Change --(--), 1-15.
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DOI: 10.1007/s10584-014-1160-x
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Abstract:
Abstract:
Future climate projections from general circulation models (GCMs) predict an
acceleration of the global hydrological cycle throughout the 21st century in response to human-induced rise in temperatures. However, projections of GCMs are too coarse in resolution to be used in local studies of climate change impacts. To cope with this problem, downscaling methods have been developed that transform climate projections into high resolution datasets to drive impact models such as rainfall-runoff models. Generally, the range of changes simulated by different GCMs is considered to be the major source of variability in the results of such studies. However, the cascade of uncertainty in runoff projections is further elongated by differences between impact models, especially where robust calibration is hampered by the scarcity of data.
Here, we address the relative importance of these different sources of uncertainty in a poorly monitored headwater catchment of the Ecuadorian Andes. Therefore, we force 7 hydrological models with downscaled outputs of 8 GCMs driven by the A1B and A2 emission scenarios over the 21st century. Results indicate a likely increase in annual runoff by 2100 with a large variability between the different combinations of a climate model with a hydrological
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Keywords: |
climate change |
Uncertainty analysis |
hydrological catchment model |
Windhorst, D.; Kraft, P.; Timbe, E.; Frede, H. & Breuer, L. (2014): Stable water isotope tracing through hydrological models for disentangling runoff generation processes at the hillslope scale. Hydrol. Earth Syst. Sci. 18(10), 4113-4127.
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DOI: 10.5194/hess-18-4113-2014
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Abstract:
Abstract:
Hillslopes are the dominant landscape components
where incoming precipitation becomes groundwater, streamflow
or atmospheric water vapor. However, directly observing
flux partitioning in the soil is almost impossible. Hydrological
hillslope models are therefore being used to investigate
the processes involved. Here we report on a modeling
experiment using the Catchment Modeling Framework
(CMF) where measured stable water isotopes in vertical
soil profiles along a tropical mountainous grassland hillslope
transect are traced through the model to resolve potential
mixing processes. CMF simulates advective transport of
stable water isotopes 18O and 2H based on the Richards equation
within a fully distributed 2-D representation of the hillslope.
The model successfully replicates the observed temporal
pattern of soil water isotope profiles (R2 0.84 and Nash–
Sutcliffe efficiency (NSE) 0.42). Predicted flows are in good
agreement with previous studies. We highlight the importance
of groundwater recharge and shallow lateral subsurface
flow, accounting for 50 and 16% of the total flow leaving the
system, respectively. Surface runoff is negligible despite the
steep slopes in the Ecuadorian study region.
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Keywords: |
isotopes |
isotope tracers |
hydrological catchment model |
Knoke, T.; Bendix, J.; Pohle, P.; Hamer, U.; Hildebrandt, P.; Roos, K.; Gerique, A.; Lopez Sandoval, M.F.; Breuer, L.; Tischer, A.; Silva, B.; Calvas, B.; Aguirre, N.; Castro, L.M.; Windhorst, D.; Weber, M.; Stimm, B.; Günter, S.; Palomeque, X.; Mora, J.; Mosandl, R. & Beck, E. (2014): Afforestation or intense pasturing improve the ecological and economic value of abandoned tropical farmlands. Nature Communications 5:5612, 1-50.
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DOI: 10.1038/ncomms6612
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Abstract:
Abstract:
Increasing demands for livelihood resources in tropical rural areas have led to progressive
clearing of biodiverse natural forests. Restoration of abandoned farmlands could counter
this process. However, as aims and modes of restoration differ in their ecological and
socio-economic value, the assessment of achievable ecosystem functions and bene?ts
requires holistic investigation. Here we combine the results from multidisciplinary research
for a unique assessment based on a normalization of 23 ecological, economic and social
indicators for four restoration options in the tropical Andes of Ecuador. A comparison of the
outcomes among afforestation with native alder or exotic pine, pasture restoration with either
low-input or intense management and the abandoned status quo shows that both variants of
afforestation and intense pasture use improve the ecological value, but low-input pasture
does not. Economic indicators favour either afforestation or intense pasturing. Both Mestizo
and indigenous Saraguro settlers are more inclined to opt for afforestation.
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Keywords: |
sustainable land-use |