Publications
Found 516 publication(s)
- of type article
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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Abstract:
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): The impact of roads on the avifauna of páramo grasslands in Cajas National Park, 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 |
Bahr, E.; Chamba Zaragocin, D.; Fierro Jaramillo, N.; Witt, A. & Makeschin, F. (2014): Modeling of soil nutrient balances, flows and stocks revealed effects of management on soil fertility in south Ecuadorian smallholder farming systems. Nutrient Cycling in Agroecosystems -, -.
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DOI: 10.1007/s10705-014-9662-5
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Abstract:
Abstract:
Linking nutrient balances and flows to soil
nutrient stocks creates a valuable indicator for sustainability
assessment in agricultural land-use systems.
Therefore, we investigated the impact of management
on soil fertility at farm/field scale using the Nutmon
approach. A detailed methodology for the adaptation
of the difficult-to-quantify flows to the local conditions
is described. Research was carried out in the three
farming systems of Yantzaza (low-external-input), El
Tambo (irrigated cash crops) and San Lucas (integrated
nutrient management) in southern Ecuador. For
each land-use within a farm (annual and perennial
crops, pasture, forest), soil nutrient balances and flows
were modeled with Nutmon and soil nutrient stocks
were calculated for NPK. Soil nutrient balances were
evaluated using potential socio-economic and soil
fertility explanatory variables. Balances for the different
land-uses in the three research areas varied between
-151 to 66 kg ha-1 a-1 for N, -4 to 33 kg ha-1 a-1 for P and -346 to 39 kg ha-1 a-1 for K and were mainly negative. Up to 70 % of the balances’ variability was explained by soil fertility variables and financial flows. Highest external inputs existed in
land-uses with a strong market orientation. Land-uses
benefiting from a surplus of within-farm flows had the
highest soil nutrient stocks. The focus on N fertilization
induced highly negative PKbalances in annual crops of
El Tambo. In contrast, the application of organic
fertilizers and nutrient recycling in San Lucas resulted
in positive NP balances particularly for perennial
crops. NP balances in annual crops of Yantzaza were
most negative due to nonexistent fertilization, leaching
and burning of crop residues. A non-sustainable landuse
of annual crops in Yantzaza was illustrated by total
N stock decreases of 4.9 % a-1 and decreased soil
organic carbon stocks to 85 % of adjacent forest sites.
Results indicated a potential risk regarding sustainable
management of soils in the research area and provide a
basis for policy and decision makers to develop
appropriate management strategies.
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Keywords: |
soil nutrient depletion |
Nutmon |
agricultural soil |
sustainable land-use |
within-farm flows |
Werner, F.A. & Homeier, J. (2014): Is tropical montane forest heterogeneity promoted by a resource-driven feedback cycle? Evidence from nutrient relations, herbivory and litter decomposition along a topographical gradient. Functional Ecology x(x), x.
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DOI: 10.1111/1365-2435.12351
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Abstract:
Abstract:
1. Ridges of tropical mountains often differ strikingly from neighbouring ravines in terms of
forest structure, productivity and species composition. This heterogeneity is poorly understood
despite its critical role in biodiversity maintenance, carbon and nutrient budgets.
2. We examined measures of tree biomass and productivity, foliage and litter quality (nutrient
concentrations, specific leaf mass, phenolics), herbivory and leaf litter decomposition in each
six plots laid out in upper and lower slope position in a tropical montane moist forest in southeastern
Ecuador.
3. Productivity, quality of foliage and litter as well as herbivory were significantly lower in
upper slope position, and closely correlated with soil nutrient concentrations and accumulated
humus. The decomposition of upper slope leaf litter (decomposition rate k) was substantially
lower than in litter from lower slope forest, whereas the site of decomposition (slope position)
only had a marginal effect on the decomposition rate.
4. Our results suggest that the differences in stand structure, productivity, foliar quality, herbivory
and decomposition between slope positions are ultimately due to stronger nutrient limitations
in upper slope forest. We propose a general conceptual model that explains origin and
maintenance of contrasting forest types along topographical gradients through down-slope
fluxes of nutrients and water, and a nutrient-driven positive feedback cycle.
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Keywords: |
topographic heterogenity |
Makowski, S.; Rollenbeck, R.; Trachte, K. & Bendix, J. (2014): Natural or anthropogenic? On the origin of atmospheric sulfate deposition in the Andes of southeastern Ecuador. Atmos. Chem. Phys 14, 11297–11312.
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DOI: 10.5194/acp-14-11297-2014
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Abstract:
Abstract:
Atmospheric sulfur deposition above certain limits
can represent a threat to tropical forests, causing nutrient
imbalances and mobilizing toxic elements that impact biodiversity
and forest productivity. Atmospheric sources of sulfur
deposited by precipitation have been roughly identified in
only a few lowland tropical forests. Even scarcer are studies
of this type in tropical mountain forests, many of them megadiversity
hotspots and especially vulnerable to acidic deposition.
In these places, the topographic complexity and related
streamflow conditions affect the origin, type, and intensity of
deposition. Furthermore, in regions with a variety of natural
and anthropogenic sulfur sources, like active volcanoes and
biomass burning, no source emission data has been used for
determining the contribution of each source to the deposition.
The main goal of the current study is to evaluate sulfate
(SO?
4 ) deposition by rain and occult precipitation at two topographic
locations in a tropical mountain forest of southern
Ecuador, and to trace back the deposition to possible emission
sources applying back-trajectory modeling. To link upwind
natural (volcanic) and anthropogenic (urban/industrial
and biomass-burning) sulfur emissions and observed sulfate
deposition, we employed state-of-the-art inventory and satellite
data, including volcanic passive degassing as well. We
conclude that biomass-burning sources generally dominate
sulfate deposition at the evaluated sites. Minor sulfate transport
occurs during the shifting of the predominant winds
to the north and west. Occult precipitation sulfate deposition
and likely rain sulfate deposition are mainly linked to
biomass-burning emissions from the Amazon lowlands. Volcanic
and anthropogenic emissions from the north and west
contribute to occult precipitation sulfate deposition at the
mountain crest Cerro del Consuelo meteorological Station and to rain-deposited sulfate at the upriver mountain pass El
Tiro meteorological station.
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Keywords: |
Nutrient deposition |
Iniguez, C.; Leiva Calderón, A.; Breuer, L.; Frede, H. & Hampel, H. (2014): Deforestation and benthic indicators: How much vegetation cover is needed to sustain healthy Andean streams? . PLoS ONE 9(8), e105869.
Silva, B.; Roos, K.; Fries, A.; Rollenbeck, R.; Beck, E. & Bendix, J. (2014): Mapping Two Competing Grassland Species from a Low-Altitude Helium Balloon. IEEE Journal of selected topics in applied earth observations and remote sensing 7(7), 3038 - 3049.
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DOI: 10.1109/JSTARS.2014.2321896
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Abstract:
Abstract:
This paper describes a method of low-altitude remote
sensing in combination with in situ measurements (leaf area, spectroscopy, and position) to monitor the postfire canopy recovery of two competing grassland species. The method was developed in the Andes of Ecuador, where a tethered balloon with a digital camera was deployed to record a time series of very high spatial resolution
imagery ( nominal resolution = 2cm ) of an experimental plot covered by two competing species: 1) the pasture grass, Setaria sphacelata; and 2) the invasive southern bracken, Pteridium arachnoideum. Image processing techniques were combined to solve geometric issues and construct high-quality mosaics for image classification. The semiautomatic and object-oriented classification method was based on geometrical and textural attributes of image segments and showed promising results for detecting the invasive bracken fern in Setaria pastures (performance by area under the curve, AUC = 0.88). Valuable insights are given into vegetation monitoring applications using unmanned aerial vehicles, which produces a time series of species-specific maps, including foliage projective cover (FPC) and leaf area index (LAI). This new method constitutes an important and accessible tool for ecological investigations of competing species in pastures and validation of remote sensing information on mountain environments.
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Keywords: |
bracken |
pasture |
land cover |
LAI |
remote sensing |
abandoned pasture |
burning |
Bracken fern |
Jantz, N.; Homeier, J. & Behling, H. (2014): Representativeness of tree diversity in the modern pollen rain of Andean montane forests. Journal of Vegetation Science 25(2), 481-490.
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DOI: 10.1111/jvs.12105
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Abstract:
Abstract:
Questions: To assess the relationship between modern pollen rain and Andean
montane forest vegetation for diversity, and provide a basis for interpretations of
palaeoecological data in the northern Andes, we asked: (1) can the reduction of
plant and pollen data to family level preserve information about diversity in both
data sets; (2) how precisely do tree pollen and spore types represent richness patterns
along an altitudinal gradient on tropical mountains; and (3) how similar
are tree pollen and spore family richness in relationship to tree family richness?
Location: Tropicalmontane rain forests, Podocarpus National Park in the Andes
of South Ecuador (3°S, 79°W, 1000–3000 ma.s.l.).
Methods:We analysed tree diversity and species composition in three different
rain forest types: Premontane (PMF), lowermontane (LMF) and uppermontane
(UMF).We investigated modern pollen rain using pollen traps. After testing the
reliability of a taxonomic surrogacy on the plant data, we compared abundance
and representation, as well as diversity of the two data sets at family level. This
was done using rarefaction and Sørensen indices.
Results: The correlation between tree species and families was high (r = 0.81,
P < 0.001). Sample rarefaction on tree pollen and plant family data revealed
highest pollen diversity on sites of the UMF, but highest tree diversity on LMF
and PMF sites. The Sørensen indices indicate down-drift of pollen from higher
altitudes in PMF and LMF and up-drift in UMF. Between 1% and 50% of pollen
taxa of each sample originate fromoutside the plot.
Conclusions: Taxonomic surrogacy at family level is a good tool for comparing
presence–absence patterns of plant and pollen data in tropical regions with high
tree diversity. On a family basis, pollen presence–absence data represent the corresponding
tree vegetation data, but uncertainties increase with decreasing altitude.
The higher diversity in pollen data of the UMF, but slightly lower diversity
in the LMF and PMF, can at least partly be explained by wind patterns, local
abundance of shrubs and herbs and differences in evenness.
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Keywords: |
MATRIX |
Rehmus, A.; Bigalke, M.; Valerezo, C.; Mora Castillo, J.R. & Wilcke, W. (2014): Aluminum toxicity to tropical montane forest tree seedlings in southern Ecuador: response of biomass and plant morphology to elevated Al concentrations. Plant and Soil 382(1-2), 301–315.
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DOI: 10.1007/s11104-014-2110-0
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Abstract:
Abstract:
Aims: In acid tropical forest soils (pH <5.5)increased mobility of aluminum might limit aboveground productivity. Therefore, we evaluated Al phytotoxicity of three native tree species of tropical montane
forests in southern Ecuador.
Methods: An hydroponic dose-response experiment was conducted. Seedlings of Cedrela odorata L., Heliocarpus americanus L., and Tabebuia chrysantha(Jacq.) G. Nicholson were treated with 0, 300, 600, 1200, and 2400 ?M Al and an organic layer leachate. Dose-response curves were generated for root and shoot morphologic properties to determine effective concentrations (EC).
Results: Shoot biomass and healthy leaf area decreased by 44 % to 83 % at 2400 ?M Al, root biomass did
not respond (C. odorata), declined by 51 % (H. americanus), or was stimulated at low Al concentrations
of 300 ?M (T. chrysantha). EC10 (i.e. reduction 10 %) values of Al for total biomass were 315 ?M
(C. odorata), 219 ?M (H. americanus), and 368 ?M (T. chrysantha). Helicarpus americanus, a fast growing
pioneer tree species, was most sensitive to Al toxicity. Negative effects were strongest if plants grew
in organic layer leachate, indicating limitation of plant growth by nutrient scarcity rather than Al toxicity.
Conclusions: Al toxicity occurred at Al concentrations
far above those in native organic layer leachate.
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Keywords: |
aluminum toxicity |
tropical tree seedlings |
dose-response curves |
organic layer leachate |
Graefe, S.; Leuschner, C.; Coners, H. & Hertel, D. (2011): Root functioning in tropical high-elevation forests: Environmental vs. biological control of root water absorption. Environmental and Experimental Botany 71(3), 329–336.
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DOI: 10.1016/j.envexpbot.2011.01.001
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Abstract:
Abstract:
Lowered temperatures may reduce the root water uptake of tropical trees at high elevations through several mechanisms; however, field studies to test their relevance are lacking. We measured sap flux density (J) in small-diameter tree roots across a 2000-m elevation transect in a tropical mountain forest for quantifying the effects of temperature, VPD and soil moisture on root water flow and uptake at different elevations. Recently developed miniature heat balance-sap flow gauges were applied to roots
of about 10mm in diameter in mountain forest stands at 1050, 1890 and 3060m a.s.l. in the Ecuadorian
Andes and the measured flow was related to anatomical properties of the root xylem. Between 1050 and 3060 m, mean J decreased to about a third. VPD was the most influential environmental factor controlling J at 1050 and 1890 m, while Ta was the key determinant at 3060 m. Large vessels were absent in the root xylem of high-elevation trees which resulted in a 10-fold decrease of theoretical hydraulic conductivity (kh theor) between 1050 and 3060 m. We conclude that both physical limitations (reduced VPD, increased viscosity of water) and biological constraints (large decrease of kh theor) result in a significantly reduced J and root water uptake of the trees in high-elevation tropical forests.
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Keywords: |
ecuador |
altitude |
miniature sap flow gauges |
root anatomy |
root sap flow |
theoretical hydraulic conductivity |
vpd |
Graefe, S.; Hertel, D. & Leuschner, C. (2010): N, P and K limitation of fine root growth along an elevation transect in tropical mountain forests. Acta Oecologica 36, 537-542.
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DOI: 10.1016/j.actao.2010.07.007
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Abstract:
Abstract:
It is generally assumed that tree growth in tropical low-elevation forests is primarily limited by phosphorus
while nitrogen limitation is more prominent in tropical montane forests where temperature is
lower and the soils are poorly developed. We tested this hypothesis in mountain rainforests of South
Ecuador by investigating the growth response of tree fine roots to N, P and K fertilization in ingrowth cores
exposed at 1050 m (pre-montane) and 3060 m (upper montane) elevation. Root growth into unfertilized
ingrowth cores (control treatment) was about 10 times slower at 3060 m than at 1050 m. At 1050 m, root
growth was stimulated not only by P, but also by N and K. In contrast, N was the only element to promote
root growth at 3060 m. The N concentration in fine root biomass dropped to nearly a third between 1050
and 3060 m, those of P, K, Ca and Mg decreased as well, but to a lesser degree. According to a 15NO3
15NH4
tracer study along the slope, tree fine roots accumulated nitrate and ammonium in root biomass at similar
rates between 1050 and 3060 m, despite lower temperatures higher upslope.We conclude that the nature
of nutrient limitation of tree fine root growth changes with elevation from an apparent co-limitation by
P together with N and K at 1050 m to predominant N limitation at 3060 m, which is also reflected by low
foliar N concentrations. Increasing N limitation may have caused the high fine root biomass and root/shoot
ratio in the high elevation forest, while the capability of the roots to acquire mineral N apparently was not
affected by lower temperatures at high elevations.
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Keywords: |
nitrogen |
phosphorus |
potassium |
nutrient limitation |
ecuador |
fine roots |
15N tracer study |
Acevedo Cabra, R.; Wiersma, Y.; Ankerst, D. & Knoke, T. (2014): Assessment of Wildfire Hazards with a Semiparametric Spatial Approach: A Case Study of Wildfires in South America. Environ Model Assess 19(6), 533-546.
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DOI: 10.1007/s10666-014-9411-9
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Abstract:
Abstract:
Rural households in agricultural economies are
vulnerable to several environmental risks such as fires,
floods, and droughts that may affect their productivity in
whole or in part. These hazards are especially relevant in
developing countries where farmers have few or no access
to traditional risk-transfer techniques, such as insurance and
finance, and where low governmental investments in rural
infrastructure, risk assessment techniques, or early warning
systems makes the aftermath of such hazards more
expensive and results in slower recovery for those who are
affected. In this paper, we use historical satellite data (Terra)
of burned areas in South America to fit a semiparametric
spatial model, based on kernel smoothing and on a nonlinear
relationship between average time between events and damage,
to assess the environmental hazard affecting the land’s
productivity. The results were twofold: first, we were able
to develop a spatial assessment of fire hazard, and second,
we were able to evaluate how much a farmer may lose in
terms of productivity per hectare due to the environmental hazard. The methodology may be easily adapted to other
world regions; to different environmental hazards such as
floods, windbreak, windthrow, or related land-use changes;
or to integrate various environmental hazards simultaneously,
as long as they can be monitored via remote sensing
(e.g., satellite imagery, aerial photographs, etc).
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Keywords: |
fire history |
Fries, A.; Rollenbeck, R.; Bayer, F.; Gonzalez, V.; Oñate-Valivieso, F.; Peters, T. & Bendix, J. (2014): Catchment precipitation processes in the San Francisco valley in southern Ecuador: combined approach using high-resolution radar images and in situ observations. Meteorology and Atmospheric Physics 703, x.
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DOI: 10.1007/s00703-014-0335-3
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Abstract:
Abstract:
The precise estimation of precipitation quantities in tropical mountain regions is in great demand by ecological and hydrological studies, due to the heterogeneity of the rainfall distribution and the lack of meteorological station data. This study uses radar images and ground station data to provide the required high-resolution precipitation maps. Also wind data are taken into account, due to its influence on the precipitation formation and to demonstrate the relation between synoptic wind, topography and the precipitation distribution inside small mountain valleys. The study analyses the rainfall distribution and amounts of 4 days inside the San Francisco Valley, a small catchment in the tropical Andes of southern Ecuador, representing different seasons and the typical atmospheric flows, which are correlated to the annual precipitation map. The results show that the rainfall distribution and amounts are generally defined by the wind direction and velocity, besides the topographic location in relation to the main barriers and pathways. The dominant wind direction causes a division of the catchment in a wetter eastern and a dryer western part. Moreover, the annual seasons are reversed; the main rainy season for the eastern part occurs between June and August, while the western part reaches the precipitation maximum between January and March. This may have influence on the species composition at the different slopes and the annual hydrological cycle inside the catchment.
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Keywords: |
Atmospheric Sciences |
Meteorology |
Terrestrial Pollution |
Waste Water Technology |
Water Pollution Control |
Water Management |
Aquatic Pollution |
Rillig, M.C.; Camenzind, T.; Velescu, A.; Wilcke, W.; Homeier, J.; Horn, S. & Hempel, S. (2014): Nitrogen and phosphorus additions impact arbuscular mycorrhizal abundance and molecular diversity in a tropical montane forest. Global Change Biology --, --.
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DOI: 10.1111/gcb.12618
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Abstract:
Abstract:
Increased nitrogen (N) depositions expected in the future endanger the diversity and stability of ecosystems primarily limited by N, but also often co-limited by other nutrients like phosphorus (P). In this context a nutrient manipulation experiment (NUMEX) was set up in a tropical montane rainforest in southern Ecuador, an area identified as biodiversity hotspot. We examined impacts of elevated N and P availability on arbuscular mycorrhizal fungi (AMF), a group of obligate biotrophic plant symbionts with an important role in soil nutrient cycles. We tested the hypothesis that increased nutrient availability will reduce AMF abundance, reduce species richness and shift the AMF community toward lineages previously shown to be favored by fertilized conditions. NUMEX was designed as a full factorial randomized block design. Soil cores were taken after 2 years of nutrient additions in plots located at 2000 m above sea level. Roots were extracted and intraradical AMF abundance determined microscopically; the AMF community was analyzed by 454-pyrosequencing targeting the large subunit rDNA. We identified 74 operational taxonomic units (OTUs) with a large proportion of Diversisporales. N additions provoked a significant decrease in intraradical abundance, whereas AMF richness was reduced significantly by N and P additions, with the strongest effect in the combined treatment (39% fewer OTUs), mainly influencing rare species. We identified a differential effect on phylogenetic groups, with Diversisporales richness mainly reduced by N additions in contrast to Glomerales highly significantly affected solely by P. Regarding AMF community structure, we observed a compositional shift when analyzing presence/absence data following P additions. In conclusion, N and P additions in this ecosystem affect AMF abundance, but especially AMF species richness; these changes might influence plant community composition and productivity and by that various ecosystem processes.
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Keywords: |
ECSF |
NUMEX |
nitrogen |
AM fungi |
nutrient manipulation |
Hitziger, M. & Ließ, M. (2014): Comparison of Three Supervised Learning Methods for Digital Soil Mapping: Application to a Complex Terrain in the Ecuadorian Andes. Applied and Environmental Soil Science 2014, 10 pages.
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DOI: 10.1155/2014/809495
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Abstract:
Abstract:
A digital soil mapping approach is applied to a complex, mountainous terrain in the Ecuadorian Andes. Relief features are derived from a digital elevation model and used as predictors for topsoil texture classes sand, silt, and clay. The performance of three statistical learning methods is compared: linear regression, random forest, and stochastic gradient boosting of regression trees. In linear regression, a stepwise backward variable selection procedure is applied and overfitting is controlled by minimizing Mallow’s Cp. For random forest and boosting, the effect of predictor selection and tuning procedures is assessed. 100-fold repetitions of a 5-fold cross-validation of the selected modelling procedures are employed for validation, uncertainty assessment, and method
comparison. Absolute assessment of model performance is achieved by comparing the prediction error of the selected method and the mean. Boosting performs best, providing predictions that are reliably better than the mean. The median reduction of the root mean square error is around 5%. Elevation is the most important predictor. All models clearly distinguish ridges and slopes.
The predicted texture patterns are interpreted as result of catena sequences (eluviation of fine particles on slope shoulders) and landslides (mixing up mineral soil horizons on slopes).
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Keywords: |
soil texture |
digital soil map |
Peters, T.; Bräuning, A.; Münchow, J. & Richter, M. (2014): An ecological paradox: high species diversity and low position of the upper forest line in the Andean Depression. Ecology and Evolution ece.3.1078, 1-12.
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DOI: DOI:10.1002/ece3.1078
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Abstract:
Abstract:
Systematic investigations of the upper forest line (UFL) primarily concentrate on mid and high latitudes of the Northern Hemisphere, whereas studies of Neotropical UFLs are still fragmentary. This article outlines the extraordinary high tree diversity at the UFL within the Andean Depression and unravels the links between the comparatively low position of the local UFL, high tree-species diversity, and climate. On the basis of Gentry?s rapid inventory methodology for the tropics, vegetation sampling was conducted at 12 UFL sites, and local climate (temperature, wind, precipitation, and soil moisture) was investigated at six sites. Monotypic forests dominated by Polylepis were only found at the higher located margins of the Andean Depression while the lower situated core areas were characterized by a species-rich forest, which lacked the elsewhere dominant tree-species Polylepis. In total, a remarkably high tree-species number of 255 tree species of 40 different plant families was found. Beta-diversity was also high with more than two complete species turnovers. A non-linear relationship between the floristic similarity of the investigated study sites and elevation was detected. Temperatures at the investigated study sites clearly exceeded 5.5°C, the postulated threshold value for the upper tree growth limit in the tropics. Instead, quasi-permanent trade winds, high precipitation amounts, and high soil water contents affect the local position of the UFL in a negative way. Interestingly, most of the above-mentioned factors are also contributing to the high species richness. The result is a combination of a clearly marked upper forest line depression combined with an extraordinary forest line complexity, which was an almost unknown paradox.
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Keywords: |
climate |
air temperature |
Andes |
Biodiversity |
upper forest line |
andean depression |
Timbe, E.; Windhorst, D.; Crespo, P.; Frede, H.; Feyen, J. & Breuer, L. (2014): Understanding uncertainties when inferring mean transit times of water trough tracer-based lumped-parameter models in Andean tropical montane cloud forest catchments. Hydrology and Earth System Sciences 18(4), 1503-1523.
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DOI: 10.5194/hess-18-1503-2014
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Abstract:
Abstract:
Weekly samples from surface waters, springs, soil water and rainfall were collected in a 76.9 km² mountain rain forest catchment and its tributaries in southern Ecuador.Time series of the stable water isotopes (oxygen-18 and deuterium) were used to calculate mean transit times (MTTs) and the transit time distribution functions (TTDs) solving the convolution method for seven lumped-parameter models. For each model setup, the generalized likelihood uncertainty estimation (GLUE) methodology was applied to find the best predictions, behavioral solutions and parameter identifiability. For the study basin, TTDs based on model types such as the linear–piston flow for soil waters and the exponential–piston flow for surface waters and springs performed better than more versatile equations such as the gamma and the two parallel linear reservoirs. Notwithstanding both approaches yielded a better goodness of fit for most sites, but with considerable larger uncertainty shown by GLUE. Among the tested models, corresponding results were obtained for soil waters with short MTTs (ranging from 2 to 9 weeks). For waters with longer MTTs differences were found, suggesting that for those cases the MTT should be based at least on an intercomparison of several models. Under dominant baseflow conditions long MTTs for stream water ? 2 yr were detected, a phenomenon also observed for shallow springs. Short MTTs for water in the top soil layer indicate a rapid exchange of surface waters with deeper soil horizons. Differences in travel times between soils suggest that there is evidence of a land use effect on flow generation.
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Keywords: |
mean transit time |
transit time distribution function |
isotope tracers |
catchment hydrology |
Uncertainty analysis |
Lumped-models |
Bahr, E.; Chamba Zaragocin, D. & Makeschin, F. (2014): Soil nutrient stock dynamics and land-use management of annuals,perennials and pastures after slash-and-burn in the SouthernEcuadorian Andes. Agriculture, Ecosystems and Environment 188(0), 275-288.
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DOI: 10.1016/j.agee.2014.03.005
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Abstract:
Abstract:
Quantification of nutrient stocks and their temporal changes are considered of prime importance in farm-ing systems of the humid tropics to answer the question of sustainable management. The research areain the Southern Ecuadorian Andes included forest, annual (0–5 years old) and different aged perennial(0–5, 6–10, 11–20, 21–30) and pasture (0–5, 6–10, 11–20, 21–30, >30) sites. Soil organic carbon (SOC),total and plant available soil nutrient stocks and nutrient balances were investigated to assess temporalsoil nutrient dynamics in relation to management activities. Forest conversion by slash-and-burn caused a decrease in SOC stocks in all three land-uses amounting between 14% and 19%. This was mainly due tothe absence of an organic layer and losses in the upper five cm of the mineral soil. Stocks of exchangeablebases and pH values increased in annuals which however, had the most negative nutrient balance of allland-uses amounting to ?128, ?25 and ?226 kg ha?1 a?1 for N, P and K, respectively. The abandonmentof annual sites after five years was linked to a shortage of available N and P due to low-external-input management which caused SOC stock decreases. Major soil nutrient changes in perennials and pasturesdid not occur directly but 6–20 years after forest conversion with increases in stocks for total N, P, S and exchangeable bases above forest level. SOC stocks of medium aged perennials and pastures increased above forest level in the mineral soil. Easily available inorganic N and P stocks remained low throughout the chronosequence in perennials and pastures, indicating a quick uptake by plant roots and microor-ganisms. Compared to medium aged sites, oldest perennials and pastures showed a strong decrease in SOC (?28% and ?16%) and soil nutrient stocks. Stocks for total N, P, S and exchangeable bases were up to50% below those of medium aged sites in oldest perennials and pastures.
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Keywords: |
land-use change |
tropical soils |
chronosequence |
low-external-input management |
soil nutrient depletion |
soil organic carbon |
Bahr, E.; Hamer, U.; Chamba, D. & Makeschin, F. (2013): Different fertilizer types affected nitrogen and carbon cycling in eroded and colluvial soils of Southern Ecuador. Agricultural Sciences 4(12A), 19-32.
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DOI: 10.4236/as.2013.412A002
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Abstract:
Abstract:
A tropical smallholder cash crop farming system in a semi-arid Inter-Andean valley of Ecuador was investigated. Intensive irrigated agriculture with up to 400 kg of urea-N fertilization ha?1·a?1 prevails in colluvial sites whereas urea application in the steep eroded sites is lower. Farmers did recently introduce manure to partly replace urea fertilization. Knowledge about the effects of mineral and organic fertilizers on nitrogen and carbon cycling needs to be improved to maintain sustainable agriculture in the research area. Therefore, a laboratory incubation experiment was conducted to investigate effects of urea and guinea pig manure on microbial activity of colluvial foot slope and eroded upper slope soils. Soil samples were treated with 200 kg·N·ha?1 either applied as urea, guinea pig manure or a combination of both and compared to a control. Urea fertilizer was labeled with 15N to trace its fate. Microbial biomass and basal respiration were determined in different time intervals. Urea fertilization induced an acceleration of soil organic matter (SOM) mineralization (positive priming effect) in the first seven days of incubation. The combined fertilization served as a positive alternative to the present urea management since it increased the amount of microbial biomass and provided mineral nitrogen for immediate plant uptake. Moreover, low recovery rates suggested an immobilization of fertilized nitrogen into the microbial biomass inducing an efficient and sustained nutrient release throughout the entire growing season. SOM stocks in colluvial soils were 40% below those of eroded soils which was partly due to the positive priming effect after urea fertilization. Microbial activity and efficiency were not reduced by soil erosion.
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Keywords: |
fertilization |
soil organic matter |
priming effect |
15N-labeled urea |
guinea pig manure |
erosion |
Wullaert, H.; Bigalke, M.; Homeier, J.; Cumbicus Torres, N.; Valarezo, C. & Wilcke, W. (2013): Short-term response of the Ca cycle of a montane forest in Ecuador to low experimental CaCl2 additions. Journal of Plant Nutrition and Soil Science 176(6), 892-903.
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DOI: 10.1002/jpln.201300146
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Abstract:
Abstract:
The tropical montane forests of the E Andean cordillera in Ecuador receive episodic Sahara dust inputs particularly increasing Ca deposition. We added CaCl2 to isolate the effect of Ca deposition by Sahara dust to tropical montane forest from the simultaneously occurring pH effect. We examined components of the Ca cycle at four control plots and four plots with added Ca (2 × 5 kg ha–1 Ca annually as CaCl2) in a random arrangement. Between August 2007 and December 2009 (four applications of Ca), we determined Ca concentrations and fluxes in litter leachate, mineral soil solution (0.15 and 0.30 m depths), throughfall, and fine litterfall and Al concentrations and speciation in soil solutions. After 1 y of Ca addition, we assessed fine-root biomass, leaf area, and tree growth. Only < 3% of the applied Ca leached below the acid organic layer (pH 3.5–4.8). The added CaCl2 did not change electrical conductivity in the root zone after 2 y. In the second year of fertilization, Ca retention in the canopy of the Ca treatment tended to decrease relative to the control. After 2 y, 21% of the applied Ca was recycled to soil with throughfall and litterfall. One year after the first Ca addition, fine-root biomass had decreased significantly. Decreasing fine-root biomass might be attributed to a direct or an indirect beneficial effect of Ca on the soil decomposer community. Because of almost complete association of Al with dissolved organic matter and high free Ca2+ : Al3+ activity ratios in solution of all plots, Al toxicity was unlikely. We conclude that the added Ca was retained in the system and had beneficial effects on some plants.
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Keywords: |
tree growth |
NUMEX |
roots |
calcium |
aluminium |
nutrient cycle |
Wilcke, W.; Leimer, S.; Peters, T.; Emck, P.; Rollenbeck, R.; Trachte, K.; Valarezo, C. & Bendix, J. (2013): The nitrogen cycle of tropical montane forest in Ecuador turns inorganic under environmental change. Global Biogeochemical Cycles 27(4), 1194-1204.
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DOI: 10.1002/2012GB004471
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Abstract:
Abstract:
Water-bound nitrogen (N) cycling in temperate terrestrial ecosystems of the Northern
Hemisphere is today mainly inorganic because of anthropogenic release of reactive N to
the environment. In little-industrialized and remote areas, in contrast, a larger part of
N cycling occurs as dissolved organic N (DON). In a north Andean tropical montane forest
in Ecuador, the N cycle changed markedly during 1998–2010 along with increasing
N deposition and reduced soil moisture. The DON concentrations and the fractional
contribution of DON to total N significantly decreased in rainfall, throughfall, and soil
solutions. This inorganic turn of the N cycle was most pronounced in rainfall and became
weaker along the flow path of water through the system until it disappeared in stream water.
Decreasing organic contributions to N cycling were caused not only by increasing inorganic
N input but also by reduced DON production and/or enhanced DON decomposition.
Accelerated DON decomposition might be attributable to less waterlogging and higher
nutrient availability. Significantly increasing NO3-N concentrations and NO3-N/NH4-N
concentration ratios in throughfall and litter leachate below the thick organic layers indicated
increasing nitrification. In mineral soil solutions, in contrast, NH4-N concentrations increased and NO3-N/NH4-N concentration ratios decreased significantly, suggesting increasing net ammonification. Our results demonstrate that the remote tropical montane forests on the rim of the Amazon basin experienced a pronounced change of the N cycle in only one decade. This change likely parallels a similar change which followed industrialization in the temperate zone of the Northern Hemisphere more than a century ago.
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Keywords: |
climate change |
nitrification |
N deposition |
terrestrial N cycling |
dissolved organic N |