Publications
Found 80 publication(s)
- of type article
Alvarez Figueroa, P.A.; Velescu, A.; Pierick, K. & Homeier, J. (2024): Sources and sinks of N in ecosystem solutions along the water path through a tropical montane forest in Ecuador assessed with δ15N values of total dissolved nitrogen. Journal of Geophysical Research: Biogeosciences 129, e2024JG008, 1-16.
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DOI: 10.1029/2024JG008043
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Abstract:
Abstract:
The globally increasing reactive N richness affects even remote ecosystems such as the tropical montane forests in Ecuador. We tested whether the δ15N values of total dissolved N (TDN), measured directly in solution with a TOC‐IRMS, can be used to help elucidate N sources and sinks along the water path and thus might be suitable for ecosystem monitoring. From 2013 to 2016, the δ15N values of TDN in bulk deposition showed the most pronounced temporal variation of all ecosystem solutions (δ15N values: 1.9–5.9‰). In throughfall (TF), TDN was on average 15N‐depleted (-1.8 ± s.d. 0.4‰) relative to rainfall (3.4 ± 0.9‰), resulting from net retention of isotopically heavy N, mainly as NH4+. Simultaneously, N‐isotopically light NO3‐N and dissolved organic nitrogen (DON) with a δ15N value between NO3‐N and NH4‐N were leached from the canopy (leaves: -3.5 ± 0.5‰). The increasing δ15N values in the order, TF < stemflow (SF, 0.1 ± 0.6‰) < litter leachate (LL, 1.3 ± 0.7‰) concurred with an increasing DON contribution to TDN reflecting the δ15N value of the organic layer (1.9 ± 0.9‰). The lower δ15N value of the mineral soil solution at the 0.15 m soil depth (SS15, -1.5 ± 0.3‰) than in LL can be explained by the retention of DON and NH4+ and the addition of NO3- from mineralization and nitrification. The increasing δ15N values in the order, SS15 < SS30 (-0.6 ± 0.2‰) < streamflow (ST, 0.5 ± 0.6‰) suggested gaseous N losses because of increasing denitrification. There was no seasonality of the δ15N values. Our results demonstrate that the δ15N values of TDN in ecosystem solutions help identify N sources and sinks in forest ecosystems.
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Keywords: |
throughfall |
15N natural abundance |
rainfall |
litter leachate |
time series |
Barczyk, M.; Acosta Rojas, D.C.; Espinosa, C.I.; Homeier, J.; Tinoco, B.A.; Velescu, A.; Wilcke, W.; Schleuning, M. & Neuschulz, E.L. (2024): Environmental conditions differently shape leaf, seed and seedling trait composition between and within elevations of tropical montane forests. Oikos e10421, 0-10.
Alvarez Figueroa, P.A.; Velescu, A.; Pierick, K.; Homeier, J. & Wilcke, W. (2023): Carbon stable isotope ratios of dissolved organic matter as a tool to identify its sources and transformations in a tropical montane forest in Ecuador. Environmental Science and Technology 57, 14983−14993.
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DOI: 10.1021/acs.est.3c01623
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Abstract:
Dissolved organic matter (DOM) contributes to forest C cycling. We assessed temporal variability, sources, and transformations of DOM during four years in a tropical montane forest with the help of stable C isotope ratios (δ13C values). We measured δ13C values of DOM in rainfall (RF), throughfall (TF), stemflow (SF), litter leachate (LL), soil solutions at the 0.15 and 0.30 m depths (SS15, SS30), and streamflow (ST)with TOC-IRMS. The δ13C values of DOM did not vary seasonally. We detected an event with a high δ13C value likely attributable to black carbon from local pasture fires. The mean δ13C values of DOM outside the event decreased in the order, RF (−26.0 ± 1.3‰) > TF (−28.7 ± 0.3‰) > SF (−29.2 ± 0.2‰) > LL (−29.6 ± 0.2‰) because of increasing leaching of C-isotopically light compounds. The higher δ13C values of DOM in SS15 (−27.8 ± 1.0‰), SS30 (−27.6 ± 1.1‰), and ST (−27.9 ± 1.1‰) than in the above-ground solutions suggested that roots and root exudates are major belowground DOM sources. Although in DOM the C/N ratios correlated with the δ13C values when all solutions were considered, this was not the case for SS15, SS30, and ST alone. Thus, the δ13C values of DOM provide an additional tool to assess the sources and turnover of DOM.
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Keywords: |
C/N ratio |
13C natural abundance |
Dissolved organic carbon |
Acosta Rojas, D.C.; Barczyk, M.; Espinosa, C.I.; Farwig, N.; Homeier, J.; Tiede, Y.; Velescu, A.; Tinoco, B.A.; Wilcke, W.; Neuschulz, E.L. & Schleuning, M. (2023): Abiotic factors similarly shape the distribution of fruit, seed and leaf traits in tropical fleshy-fruited tree communities. Acta Oecologica 121, 103953.
Pierick, K.; Leuschner, C.; Link, R.; Baez, S.; Velescu, A.; Wilcke, W. & Homeier, J. (2024): Above-and belowground strategies of tropical montane tree species are coordinated and driven by small-scale nitrogen availability. Functional Ecology 38, 1364-1377.
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DOI: 10.1111/1365-2435.14554
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Abstract:
Abstract:
1. The question whether the strategies of above-and belowground plant organs
are coordinated as predicted by the plant economics spectrum theory is still
under debate. We aim to determine the leading dimensions of tree trait variation
for above-and belowground functional traits, and test whether they represent
spectra of adaptation along a soil fertility gradient in tropical Andean
forests.
2. We measured leaf, stem and fine root functional traits, and individual-level
soil nutrient availability for 433 trees from 52 species at three elevations between
1000 and 3000 m a.s.l.
3. We found close coordination between above– and belowground functional traits
related to the trade-off between resource acquisition and conservation, whereas
root diameter and specific root length formed an independent axis of covarying
traits. The position of a tree species along the acquisition–conservation axis of
the trait space was closely associated with local soil nitrogen, but not phosphorus,
availability.
4. Our results imply that above-and belowground plant functional traits determine
at which edaphic microhabitats coexisting tree species can grow, which is potentially
crucial for understanding community assembly in species-rich
tropical montane forests.
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Keywords: |
Ecuador |
tropical montane forest |
fine roots |
intraspecific variability |
functional traits |
Velescu, A.; Homeier, J.; Bendix, J.; Valarezo, C. & Wilcke, W. (2021): Response of water-bound fluxes of potassium, calcium, magnesium and sodium to nutrient additions in an Ecuadorian tropical montane forest. Forest Ecology and Management 501(119661), 1-14.
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DOI: 10.1016/j.foreco.2021.119661
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Abstract:
Abstract:
In the past two decades, the Amazon-exposed, tropical montane rain forests in south Ecuador experienced increasing deposition of reactive N mainly from Amazonian forest fires, episodic Ca and Mg inputs from Saharan dust, and a low but constant P deposition from unknown sources. To explore the response of this tropical, perhumid ecosystem to nutrient inputs, we established in 2007 a Nutrient Manipulation Experiment (NUMEX). Since 2008, we have applied 50 kg ha−1 year−1 of N as urea, 10 kg ha−1 year−1 of P as NaH2PO4·H2O, 50 kg ha−1 year−1 of N + 10 kg ha−1 year−1 of P and 10 kg ha−1 year−1 of Ca as CaCl2·H2O in a randomized block design at 2000 m a.s.l. in a natural forest of the south Ecuadorian Andes. Previous studies have shown that alkali and alkaline earth metals had beneficial effects on the functioning of N and P co-limited tropical forests occurring on acidic soils. Therefore, we determined the response of all major aqueous ecosystem fluxes of K, Ca, Mg and Na to nutrient amendments, to understand how increasing atmospheric deposition would affect their cycling in the future. Additions of N and P decreased K leaching from the organic layer and in the mineral soil, thus tightening K cycling. This suggests that increasing future N and P availability may result in K limitation in the long term. The leaching of Ca and Mg from the canopy increased in response to amendments of N and P and we observed an enhanced uptake of these nutrients also if Ca was amended alone. Although N was applied as urea, acidity of soil solutions and leaching of K, Ca, Mg and Na did not increase following separate N amendments. In spite of the acid soils and of its low cation-exchange competitivity, Na included in the P fertilizer was only partly leached from the organic layer. We suggest that it was probably required to cover an unmet Na demand of the soil fauna. Our results demonstrate the major role in the functioning of the tropical montane forests played by K, Ca and Mg as potential future growth-limiting elements and increasingly required nutrients in response to rising N and P availability, while they also support the importance of Na as a functional element in these ecosystems.
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Keywords: |
Ecuador |
NUMEX |
nutrient manipulation |
tropical montane forest |
nutrient additions |
base cations |
Dantas De Paula, M.; Forrest, M.; Langan, L.; Bendix, J.; Homeier, J.; Velescu, A.; Wilcke, W. & Hickler, T. (2021): Nutrient cycling drives plant community trait assembly and ecosystem functioning in a tropical mountain biodiversity hotspot. New Phytologist -(-), -.
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DOI: 10.1111/nph.17600
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Abstract:
Summary Community trait assembly in highly diverse tropical rainforests is still poorly understood. Based on more than a decade of field measurements in a biodiversity hotspot of southern Ecuador, we implemented plant trait variation and improved soil organic matter dynamics in a widely used dynamic vegetation model (the Lund-Potsdam-Jena General Ecosystem Simulator, LPJ-GUESS) to explore the main drivers of community assembly along an elevational gradient. In the model used here (LPJ-GUESS-NTD, where NTD stands for nutrient-trait dynamics), each plant individual can possess different trait combinations, and the community trait composition emerges via ecological sorting. Further model developments include plant growth limitation by phosphorous (P) and mycorrhizal nutrient uptake. The new model version reproduced the main observed community trait shift and related vegetation processes along the elevational gradient, but only if nutrient limitations to plant growth were activated. In turn, when traits were fixed, low productivity communities emerged due to reduced nutrient-use efficiency. Mycorrhizal nutrient uptake, when deactivated, reduced net primary production (NPP) by 61–72% along the gradient. Our results strongly suggest that the elevational temperature gradient drives community assembly and ecosystem functioning indirectly through its effect on soil nutrient dynamics and vegetation traits. This illustrates the importance of considering these processes to yield realistic model predictions.
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Keywords: |
mycorrhiza |
dynamic vegetation model |
nutrient cycling |
plant community assembly |
plant functional traits |
tropical montane forests (TMF) |
Bendix, J.; Aguirre, N.; Beck, E.; Bräuning, A.; Brandl, R.; Breuer, L.; Boehning-Gaese, K.; Dantas De Paula, M.; Hickler, T.; Homeier, J.; Inclan, D.; Leuschner, C.; Neuschulz, E.; Schleuning, M.; Suarez, J.P.; Trachte, K.; Wilcke, W. & Farwig, N. (2021): A research framework for projecting ecosystem change in highly diverse tropical mountain ecosystems. Oecologia 2021, 1-13.
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DOI: 10.1007/s00442-021-04852-8
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Abstract:
Abstract:
Tropical mountain ecosystems are threatened by climate and land-use changes. Their diversity and complexity make projec-
tions how they respond to environmental changes challenging. A suitable way are trait-based approaches, by distinguishing
between response traits that determine the resistance of species to environmental changes and efect traits that are relevant
for species’ interactions, biotic processes, and ecosystem functions. The combination of those approaches with land surface
models (LSM) linking the functional community composition to ecosystem functions provides new ways to project the
response of ecosystems to environmental changes. With the interdisciplinary project RESPECT, we propose a research
framework that uses a trait-based response-efect-framework (REF) to quantify relationships between abiotic conditions,
the diversity of functional traits in communities, and associated biotic processes, informing a biodiversity-LSM. We apply
the framework to a megadiverse tropical mountain forest. We use a plot design along an elevation and a land-use gradient
to collect data on abiotic drivers, functional traits, and biotic processes. We integrate these data to build the biodiversity-
LSM and illustrate how to test the model. REF results show that aboveground biomass production is not directly related to
changing climatic conditions, but indirectly through associated changes in functional traits. Herbivory is directly related to
changing abiotic conditions. The biodiversity-LSM informed by local functional trait and soil data improved the simulation
of biomass production substantially. We conclude that local data, also derived from previous projects (platform Ecuador), are
key elements of the research framework. We specify essential datasets to apply this framework to other mountain ecosystems.
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Keywords: |
Biodiversity-Land-Surface-Model |
Wilcke, W.; Velescu, A.; Leimer, S.; Blotevogel, S.; Alvarez Figueroa, P.A. & Valarezo, C. (2020): Total organic carbon concentrations in ecosystem solutions of a remote tropical montane forest respond to global environmental change. Global Change Biology 26, 6989–7005.
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DOI: 10.1111/gcb.15351
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Abstract:
The response of organic carbon (C) concentrations in ecosystem solutions to environmental change affects the release of dissolved organic matter (DOM) from forests to surface and groundwaters. We determined the total organic C (TOC) concentrations (filtered <1–7 μm) and the ratios of TOC/dissolved organic nitrogen (DON) concentrations, electrical conductivity (EC), and pH in all major ecosystem solutions of a tropical montane forest from 1998 to 2013. The forest was located on the rim of the Amazon basin in Ecuador and experienced increasing numbers of days with >25°C, decreasing soil moisture, and rising nitrogen (N) deposition from the atmosphere during the study period. In rainfall, throughfall, mineral soil solutions (at the 0.15- and 0.30-m depths), and streamflow, TOC concentrations and fluxes decreased significantly from 1998 to 2013, while they increased in stemflow. TOC/DON
ratios decreased significantly in rainfall, throughfall, soil solution at the 0.15-m depth, and streamflow. Based on Δ14C values, the TOC in rainfall and mineral soil solutions was 1 year old and that of litter leachate was 10 years old. The pH in litter leachate decreased with time, that in mineral soil solutions increased, while those in the other ecosystem solutions did not change. Thus, reduced TOC solubility because of lower pH values cannot explain the negative trends in TOC concentrations in most ecosystem
solutions. The increasing TOC concentrations and EC in stemflow pointed at an increased leaching of TOC and other ions from the bark. Our results suggest an accelerated degradation of DOM, particularly of young DOM, associated with the production of N-rich compounds simultaneously to changing climatic conditions and increasing N availability. Thus, environmental change increased the CO2 release to the atmosphere but reduced DOM export to surface and groundwater.
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Keywords: |
Dissolved organic carbon |
time series |
carbon-14 dating |
TOC:DON ratio |
ecosystem fluxes |
Knoke, T.; Paul, C.; Rammig, A.; Gosling, E.; Hildebrandt, P.; Härtl, F.; Peters, T.; Richter, M.; Diertl, K.; Castro, L.M.; Calvas, B.; Ochoa Moreno, S.; Valle-Carrión, L.A.; Hamer, U.; Tischer, A.; Potthast, K.; Windhorst, D.; Homeier, J.; Wilcke, W.; Velescu, A.; Gerique, A.; Pohle, P.; Adams, J.; Breuer, L.; Mosandl, R.; Beck, E.; Weber, M.; Stimm, B.; Silva, B.; Verburg, P.H. & Bendix, J. (2020): Accounting for multiple ecosystem services in a simulation of land-use decisions: Does it reduce tropical deforestation?. Global Change Biology 26( ), 1-22.
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DOI: 10.1111/gcb.15003
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Abstract:
Abstract:
Abstract Conversion of tropical forests is among the primary causes of global environmental change. The loss of their important environmental services has prompted calls to integrate ecosystem services (ES) in addition to socio-economic objectives in decision-making. To test the effect of accounting for both ES and socio-economic objectives in land-use decisions, we develop a new dynamic approach to model deforestation scenarios for tropical mountain forests. We integrate multi-objective optimization of land allocation with an innovative approach to consider uncertainty spaces for each objective. These uncertainty spaces account for potential variability among decision-makers, who may have different expectations about the future. When optimizing only socio-economic objectives, the model continues the past trend in deforestation (1975–2015) in the projected land-use allocation (2015–2070). Based on indicators for biomass production, carbon storage, climate and water regulation, and soil quality, we show that considering multiple ES in addition to the socio-economic objectives has heterogeneous effects on land-use allocation. It saves some natural forest if the natural forest share is below 38%, and can stop deforestation once the natural forest share drops below 10%. For landscapes with high shares of forest (38%–80% in our study), accounting for multiple ES under high uncertainty of their indicators may, however, accelerate deforestation. For such multifunctional landscapes, two main effects prevail: (a) accelerated expansion of diversified non-natural areas to elevate the levels of the indicators and (b) increased landscape diversification to maintain multiple ES, reducing the proportion of natural forest. Only when accounting for vascular plant species richness as an explicit objective in the optimization, deforestation was consistently reduced. Aiming for multifunctional landscapes may therefore conflict with the aim of reducing deforestation, which we can quantify here for the first time. Our findings are relevant for identifying types of landscapes where this conflict may arise and to better align respective policies.
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Keywords: |
Ecuador |
biodiversity |
ecosystem services |
landscape restoration |
land allocation |
robust optimization |
Wilcke, W.; Velescu, A.; Leimer, S.; Bigalke, M.; Boy, J. & Valarezo, C. (2019): Temporal Trends of Phosphorus Cycling in a Tropical Montane Forest in Ecuador During 14 Years. Journal of Geophysical Research: Biogeosciences 124, 1370-1386.
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DOI: 10.1029/2018JG004942
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Abstract:
Increased bioavailability of P can have a negative impact on plant biodiversity. In an approximately 9‐ha catchment under N + P‐limited megadiverse tropical montane forest in Ecuador, we budgeted all major P fluxes and determined whether the P fluxes changed from 1999 to 2013. Furthermore, we assessed which external drivers (rainfall, total P and acid deposition) caused this potential change. Mean (±SD) annual P deposition (bulk+dry) was 240 ± 270 mg/m2, with the SD reflecting the interannual variation. The annual P flux to the soil via throughfall+stemflow+litterfall was 1,400 ± 170 mg/m2 of which 18 ± 9.2% was leached to below the organic layer. The mineral soil retained 80 ± 12% of the P leached from the organic layer. The mean annual P weathering rate was 79 ± 63 mg/m2. The sum of P fluxes was approximately 5 times larger above than below the mineral soil surface, illustrating that P was tightly cycled in the biological part of the forest. The mean annual canopy budget was negative (−120 ± 280 mg/m2); that is, P was leached from the canopy. Throughfall was the largest source of dissolved P. The P catchment budget (total deposition‐streamflow) was positive (200 ± 270 mg/m2); that is, P was retained, mainly in the soil organic layer. From 1999 to 2013, P fluxes with throughfall, stemflow, and streamflow increased significantly. The strongest driver of the P budgets of the canopy and the catchment was total P deposition. Our results demonstrate that mainly biological processes retained deposited P in the vegetation and the organic layer enhancing the internal P cycle.
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Keywords: |
litterfall |
temporal trends |
catchment budget |
weathering rates |
phosphorus fluxes |
Wilcke, W.; Velescu, A.; Leimer, S.; Bigalke, M.; Boy, J. & Valarezo, C. (2017): Biological versus geochemical control and environmental change drivers of the base metal budgets of a tropical montane forest in Ecuador during 15 years. Biogeochemistry 136, 167-189.
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DOI: 10.1007/s10533-017-0386-x
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Abstract:
Abstract:
To assess the susceptibility of the base metal budget of a remote tropical montane forest in Ecuador to environmental change, we determined the extent of biological control of base metal fluxes and explored the impact of atmospheric inputs and precipitation considered as potential drivers of ecosystem change on the base metal fluxes. We quantified all major base metal fluxes in a ca. 9.1 ha forested catchment from 1998 to 2013. Mean (±s.d.) annual flux to the soil via throughfall+ stemflow+litterfall was 13800±1500 mg m-2 Ca, 19000±1510 mg m-2 K, 4690±619 mg m-2 Mg and 846±592 mg m-2 Na of which 22±6%, 45±16%, 39±10% and 84±33%, respectively, were leached to below the organic layer. The mineral soil retained 79-94% of this Ca, K and Mg, while Na was released. Weathering rates estimated with three different approaches ranged from not detected (ND) to 504 mg m-2 yr-1 Ca, ND-1769 mg m-2 yr-1 K, 287-597 mg m-2 yr-1 Mg and 403-540 mg m-2 yr-1 Na. The size of mainly biologically controlled aboveground fluxes of Ca, K and Mg was 1-2 orders of magnitude larger than that of mainly geochemically controlled fluxes (sorption to soil and weathering). The elemental catchment budgets (total deposition-streamflow) were positive for Ca (574±893 mg m-2) and K (1330±773 mg m-2), negative for Na (-370±1300 mg m-2) and neutral for Mg (1.89±304 mg m-2). Our results demonstrate that biological processes controlled element retention for Ca, K and Mg in the biological part of the ecosystem. This was different for Na, which was mainly released by weathering from the study catchment, while the biological part of the ecosystem was Na-poor. The deposition of base metals was the strongest driver of their budgets suggesting that the base metal cycling of the study ecosystem is susceptible to changing deposition.
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Keywords: |
throughfall |
litterfall |
stem flow |
alkaline dust deposition |
acid deposition |
catchment budget |
stream flow |
weathering rates |
Rehmus, A.; Bigalke, M.; Boy, J.; Valarezo, C. & Wilcke, W. (2016): Aluminum cycling in a tropical montane forest ecosystem in southern Ecuador. Geoderma 288, 196-203.
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DOI: 10.1016/j.geoderma.2016.11.002
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Abstract:
Growth limitation induced by Al toxicity is believed to commonly occur in tropical forests, although a direct proof is frequently lacking. To test for the general assumption of Al toxicity, Al, Ca, and Mg concentrations in precipitation, throughfall, stemflow, organic layer leachate, mineral soil solutions, stream water, and the leaves of 17 native tree species were analyzed. We calculated Al fluxes and modeled Al speciation in the litter leachate and mineral soil solutions. We assessed potential Al toxicity based on soil base saturation, Al concentrations, Ca:Al and Mg:Al molar ratios and Al speciation in soil solution as well as Al concentrations and Ca:Al andMg:Al molar ratios in tree leaves. High Al fluxes in litterfall (8.77±1.3 to 14.2±1.9 kg ha?1 yr?1, mean ± SE) indicated a high Al circulation through the ecosystem. The fraction of exchangeable and
potentially plant-available Al in mineral soils was high, being a likely reason for a low root length density in
the mineral soil. However, Al concentrations in all solutions were consistently below critical values and
Ca:Al molar and the Ca2+:Alinorganic molar ratios in the organic layer leachate and soil solutions were above 1, the suggested threshold for Al toxicity. Except for two Al-accumulating and one non-accumulating tree species, the Ca:Al molar ratios in tree leaves were above the Al toxicity threshold of 12.5. Our results demonstrate high Al cycling through the vegetation partly because of the presence of some Al accumulator plants. However, there was little indication of an Al toxicity risk in soil and of acute Al toxicity in plants likely reflecting that tree species are well adapted to the environmental conditions at our study site and thus hardly prone to Al toxicity.
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Keywords: |
aluminum toxicity |
tropical forest ecosystems |
aluminum fluxes |
aluminum speciation |
molar Ca:Al ratios |
Velescu, A.; Valarezo, C. & Wilcke, W. (2016): Response of dissolved carbon and nitrogen concentrations to moderate nutrient additions in a tropical montane forest of South Ecuador. Frontiers in Earth Science 4(58), 1-18.
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DOI: 10.3389/feart.2016.00058
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Abstract:
Abstract:
In the past two decades, the tropical montane rain forests in south Ecuador experienced increasing deposition of reactive nitrogen mainly originating from Amazonian forest fires, while Saharan dust inputs episodically increased deposition of base metals. Increasing air temperature and unevenly distributed rainfall have allowed for longer dry spells in a perhumid ecosystem. This might have favored mineralization of dissolved organic matter (DOM) by microorganisms and increased nutrient release from the organic layer. Environmental change is expected to impact the functioning of this ecosystem belonging to the biodiversity hotspots of the Earth.
In 2007, we established a nutrient manipulation experiment (NUMEX) to understand the response of the ecosystem to moderately increased nutrient inputs. Since 2008, we have continuously applied 50 kg ha-1 a-1 of nitrogen (N), 10 kg ha-1 a-1 of phosphorus (P), 50 kg + 10 kg ha-1 a-1 of N and P and 10 kg ha-1 a-1 of calcium (Ca) in a randomized block design at 2000 m a.s.l. in a natural forest on the Amazonia-exposed slopes of the south Ecuadorian Andes.
Nitrogen concentrations in throughfall increased following N+P additions, while separate N amendments only increased nitrate concentrations. Total organic carbon (TOC) and dissolved organic nitrogen (DON) concentrations showed high seasonal variations in litter leachate and decreased significantly in the P and N+P treatments, but not in the N treatment. Thus, P availability plays a key role in the mineralization of DOM. TOC/DON ratios were narrower in throughfall than in litter leachate but their temporal course did not respond to nutrient amendments.
Our results revealed an initially fast, positive response of the C and N cycling to nutrient additions which declined with time. TOC and DON cycling only change if N and P supply are improved concurrently, while NO3-N leaching increases only if N is separately added. This indicates co-limitation of the microorganisms by N and P. The current increasing reactive N deposition will increase N export from the root zone, while it will only accelerate TOC and DON turnover if P availability is simultaneously increased. The Saharan dust-related Ca deposition has no impact on TOC and DON turnover.
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Keywords: |
Ecuador |
NUMEX |
nutrient manipulation |
tropical montane forest |
dissolved organic N |
nutrient additions |
total organic C |
nitrate leaching |
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 |
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 |
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 |
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 |
Homeier, J.; Hertel, D.; Camenzind, T.; Cumbicus Torres, N.; Maraun, M.; Martinson, G.; Poma, N.; Rillig, M.C.; Sandmann, D.; Scheu, S.; Veldkamp, E.; Wilcke, W.; Wullaert, H. & Leuschner, C. (2012): Tropical Andean Forests Are Highly Susceptible to Nutrient Inputs - Rapid Effects of Experimental N and P Addition to an Ecuadorian Montane Forest. PLoS ONE 7, e47128.
Werner, F.A.; Homeier, J.; Oesker, M. & Boy, J. (2011): Epiphytic biomass of a tropical montane forest varies with topography. Journal of Tropical Ecology 28, 23-31.
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DOI: 10.1017/S0266467411000526
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Abstract:
Abstract:
The spatial heterogeneity of tropical forest epiphytes has rarely been quantified in terms of biomass. In particular, the effect of topographic variation on epiphyte biomass is poorly known, although forests on ridges and ravines can differ drastically in stature and exposure. In an Ecuadorian lower montane forest we quantified epiphytic biomass along two gradients: (1) the twig-branch-trunk trajectory, and (2) the ridge-ravine gradient. Twenty-one trees were sampled in each of three forest types (ridge, slope, ravine positions). Their epiphytic biomass was extrapolated to stand level based on basal area?epiphyte load relationships, with tree basal areas taken from six plots of 400 m 2 each per forest type. Our results document the successional addition and partial replacement of lichens by bryophytes, angiosperms and finally dead organic matter along the twig-branch-trunk trajectory. Despite having the highest tree basal area, total epiphytic biomass (mean ± SD) of ravine forest was significantly lower (2.6 ± 0.7 Mg half 1) than in mid-slope forest (6.3 ± 1.1 Mg half 1) and ridge forest (4.4 ± 1.6 Mg half 1), whereas maximum bryophyte water storage capacity was significantly higher. We attribute this pattern to differences in forest dynamics, stand structure and microclimate. Although our study could not differentiate between direct effects of slope position (nutrient availability, mesoclimate) and indirect effects (stand structure and dynamics), it provides evidence that fine-scale topography needs to be taken into account when extrapolating epiphytic biomass and related matter fluxes from stand-level data to the regional scale.
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Keywords: |
Ecuador |
succession |
epiphyte |
crown humus |
dead organic matter |
carbon storage |
maximum water storage capacity |
topographic heterogenity |
Schwarz, M.T.; Oelmann, Y. & Wilcke, W. (2011): Stable N isotope composition of nitrate reflects N transformations during the passage of water through a montane rain forest in Ecuador. Biogeochemístry 102, 195-208.
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DOI: 10.1007/s10533-010-9434-5
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Abstract:
Abstract:
Knowledge of the fate of deposited N in the possibly N-limited, highly biodiverse north Andean forests is important because of the possible effects of N inputs on plant performance and species composition. We analyzed concentrations and fluxes
of NO3?N, NH4?N and dissolved organic N (DON) in rainfall, throughfall, litter leachate, mineral soil solutions (0.15?0.30 m depths) and stream water in a montane forest in Ecuador during four consecutive quarters and used the natural 15N abundance in NO3 during the passage of rain water through the
ecosystem and bulk d15N values in soil to detect N transformations. Depletion of 15N in NO3 and increased NO3
fluxes during the passage through the canopy and the organic layer indicated nitrification in these compartments. During leaching from the organic layer to mineral soil and stream, NO3
concentrations progressively decreased and were enriched in 15N but did not reach the d15N values of solid phase organic matter (d15N = 5.6?6.7%). This suggested a combination of nitrification and denitrification in mineral soil. In the wettest quarter, the d15N value of NO3 in litter leachate was smaller
(d15N = -1.58%) than in the other quarters (d15N = -9.38 ± SE 0.46%) probably because of reduced mineralization and associated fractionation against 15N. Nitrogen isotope fractionation of NO3 between litter leachate and stream water was smaller in the wettest period than in the other periods
probably because of a higher rate of denitrification and continuous dilution by isotopically lighter NO3-N from throughfall and nitrification in the organic layer during the wettest period. The stable N isotope composition of NO3
gave valuable indications of N transformations during the passage of water through the forest ecosystem from rainfall to the stream.
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Keywords: |
nitrate |
tropical montane forest |
denitrification |
nitrification |
15N natural abundance |
terrestrial N cycling |
Wullaert, H.; Homeier, J.; Valarezo, C. & Wilcke, W. (2010): Response of the N and P cycles of an old-growth montane forest in Ecuador to experimental low-level N and P amendments. Forest Ecology and Management 260, 1435-1445.
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DOI: 10.1016/j.foreco.2010.07.021
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Abstract:
Abstract:
Atmospheric nitrogen (N) and phosphorus (P) depositions are expected to increase in the tropics as a
consequence of increasing human activities in the next decades. In the literature, it is frequently assumed
that tropical montane forests are N-limited, while tropical lowland forests are P-limited. In a low-level N
and P addition experiment, we determined the short-term response of N and P cycles in a north Andean
montane forest on Palaeozoic shists and metasandstones at an elevation of 2100m a.s.l. to increased N
and P inputs. We evaluated experimental N, P and N+ P additions (50 kg ha−1 yr−1 of N, 10 kg ha−1 yr−1
of P and 50 kg + 10 kg ha−1 yr−1 of N and P, respectively) and an untreated control in a fourfold replicated
randomized block design. We collected litter leachate, mineral soil solution (0.15 and 0.30m depths),
throughfall and litterfall before the treatment began (August 2007) until 16 months after the first nutrient
application (April 2009). Less than 10 and 1% of the applied N and P, respectively, leached below the
organic layer which contained almost all roots and no significant leaching losses of N and P occurred
to below 0.15m mineral soil depth. Deposited N and P from the atmosphere in dry and wet form were
retained in the canopy of the control treatment using a canopy budget model. Nitrogen and P retention
by the canopy were reduced and N and P fluxes in throughfall and litterfall increased in their respective
treatments. The increase in N and P fluxes in throughfall after fertilization was equivalent to 2.5% of the
applied N and 2% of the applied P. The fluxes of N and P in litterfall were up to 15% and 3%, respectively,
higher in the N and N+ P than in the control treatments. We conclude that the expected elevated N and P
deposition in the tropics will be retained in the ecosystem, at least in the short term and hence, N and P
concentrations in stream water will not increase. Our results suggest that in the studied tropical montane
forest ecosystem on Palaeozoic bedrock, N and P are co-limiting the growth of organisms in the canopy
and organic layer.
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Keywords: |
tropical montane forest |
nutrient cycle |
leaching losses |
N deposition |
P deposition |
environmental change |
Wullaert, H.; Pohlert, T.; Boy, J.; Valarezo, C. & Wilcke, W. (2009): Spatial throughfall heterogeneity in a montane rain forest in Ecuador: Extent, temporal stability and drivers. Journal of Hydrology 377, 71-79.
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DOI: 10.1016/j.jhydrol.2009.08.001
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Abstract:
Abstract:
The drivers of spatial throughfall heterogeneity are still not fully understood. At an undisturbed forest site in the Ecuadorian Andes with ca. 2600 mm of annual rainfall we determined the accuracy of throughfall measurements by comparing Hellmann-type funnel gauges with troughs. At the same undisturbed and a managed, selectively-logged forest site we determined spatial variability of throughfall, temporal stability of spatial variability and the controls of spatial throughfall variability using a 4-year dataset in weekly resolution. There were no systematic differences between the collected volumes of funnel gauges and troughs. Based on the statistical distribution of annual throughfall volumes, a high number
of 27 funnel-type rainfall collectors were required in the undisturbed forest and 20 in the managed forest to estimate throughfall with an error of 10% and a confidence interval of 95%. Spatial throughfall variability in the studied forests was high, markedly stable during 4 years and similar in six selected rain events suggesting that a stable canopy structure controlled throughfall variability. After mathematically eliminating the canopy influence, no meteorological variable had a significant effect on throughfall variability. We conclude that the high spatial variability of throughfall in the study forest, mainly controlled by a long-term stable canopy structure, contributes to the creation of different ecological niches which are
a prerequisite for the enormous biological diversity of the north Andean forests.
Wilcke, W.; Günter, S.; Alt, F.; Geißler, C.; Boy, J.; Knuth, J.; Oelmann, Y.; Weber, M.; Valarezo, C. & Mosandl, R. (2009): Response of water and nutrient fluxes to improvement fellings in a tropical montane forest in Ecuador. Forest Ecology and Management 257, 1292-1304.
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DOI: 10.1016/j.foreco.2008.11.036
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Abstract:
Abstract:
Management of natural forestsmight be one option to reduce the high deforestation rate in Ecuador. We therefore evaluated the response of water and nutrient cycles in a natural tropical montane forest to improvement fellings with the aim of favoring economically valuable target trees which will later be harvested with additional ecosystem impacts not considered here. The study was conducted at ca. 1900?2200 m above sea level in the south Ecuadorian Andes on the east-exposed slope of the east cordillera. In June 2004, one of two paired ca. 10-ha large catchments was thinned by felling 10.2% of the initial basal area (dbh longer than 10 cm) on 30% of the catchment. The stems remained in situ. We measured ecosystem fluxes from rainfall via throughfall and stemflow to soil solution (litter leachate, soil solution at 15 and 30 cm depth) and stream flow between May 2004 and
May 2005. After the fellings, soil solutions were extracted from the gaps created by the felled trees and the forest next to the gaps. We determined aboveground water fluxes by direct measurement and soil water fluxes with a budget approach. In the solutions, we measured concentrations of NH4-N, NO3-N, total dissolved N, PO4-P, total dissolved P, Ca, Mg, K, Na, and Cl-. Fluxes were calculated as volumeweighted mean (vwm) concentrations times water fluxes. Dry deposition was estimated using chloride as inert tracer. The fellings increased concentrations of N, K, Ca, and Mg in the organic layer of the resulting gaps
compared with the forest next to the gaps (vwm concentrations of N: 6.4 mg/l in the forest next to the gap/8.7 mg/l in the gaps, K: 9.8/11, Mg: 1.8/3.0, Ca: 3.4/5.8). Lower nutrient concentrations and fluxes in the mineral soil of the gaps than in forest next to the gaps suggested that these nutrientswere taken up by ground vegetation and target trees. The paired modified and undisturbed catchments had similar water and nutrient budgets. The fellings did not have a significant impact on the water and nutrient budget at the catchment scale.
Boy, J.; Valarezo, C. & Wilcke, W. (2008): Water flow paths in soil control element exports in an Andean tropical montane forest. European Journal of Soil Science 59, 1209-1227.
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DOI: 10.1111/j.1365-2389.2008.01063.x
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Abstract:
Abstract:
We tested the hypothesis that concentrations of chemical constituents in stream water can be explained by the depth of water flow through soil. Therefore, we measured the concentrations of total organic carbon (TOC), NO3-N, NH4-N, dissolved organic nitrogen (DON), P, S, K, Ca, Mg, Na, Al and Mn in rainfall, throughfall, stemflow, litter leachate, mineral soil solution and stream water of three 8-13 ha catchments on steep slopes (1900-2200 m above sea level) of the south Ecuadorian Andes, from April 1998 to April 2003. Peak C (14-22 mg litre1), N (0.6-0.9 mg litre1), K (0.5-0.7 mg litre1), Ca (0.6-1.0 mg litre1), Mg (0.3-0.5 mg litre1), Al (110-390 mg litre1) and Mn (3.9-8.4 mg litre1) concentrations in stream water were associated with lateral flow (fast near-surface flow in saturated topsoil) while the greatest P (0.1-0.3 mg litre1), S (0.3-0.7 mg litre1) and Na (3.0-6.0 mg litre1) concentrations occurred during low baseflow conditions. All elements had greater concentrations in the organic layer than in the mineral soil, but only C, N, K, Ca, Mg, Al and Mn were flushed out during lateral-flow conditions. Phosphorus, S and Na, in contrast, were mainly released by weathering and (re-)oxidation of sulphides in the subsoil. Baseflow accounted for 32% to 61% of P export, while > 50% of S was exported during intermediate flow conditions (i.e. lateral flow at the depth of several tens of cm in the mineral soil). Near-surface water flow through C- and nutrient-rich topsoil during rainstorms was the major export pathway for C, N, Al and Mn (contributing > 50% to the total export of these elements). Near-surface flow also accounted for one-third of total base metal export. Our results demonstrate that near-surface flow related to storm events markedly affects the cycling of many nutrients in steep tropical montane forests.
Boy, J.; Rollenbeck, R.; Valarezo, C. & Wilcke, W. (2008): Amazonian biomass burning-derived acid and nutrient deposition in the north Andean montane forest of Ecuador. Global Biogeochemical Cycles 22, GB4011.
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DOI: 10.1029/2007GB003158
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Abstract:
Abstract:
We explored the influence of biomass burning in Amazonia and northeastern Latin
America on N, C, P, S, K, Ca, Mg, Al, Mn, and Zn cycles of an Andean montane forest in
south Ecuador exposed to the Amazon basin between May 1998 and April 2003. We
assessed the response of the element budget of three microcatchments (8?13 ha) to the
variations in atmospheric deposition between the intensive burning season and outside
the burning season in Amazonia. There were significantly elevated H, N, and Mn
depositions during biomass burning. Elevated H deposition during biomass burning
caused elevated base metal loss from the canopy and the organic horizon and
deteriorated already low base metal supply of the vegetation. N was only retained
during biomass burning but not during nonfire conditions when deposition was much
smaller. We conclude that biomass burning-related aerosol emissions in Amazonia are
large enough to substantially increase element deposition at the western rim of
Amazonia. Particularly the related increase of acid deposition impoverishes already base
metal scarce ecosystems. As biomass burning is most intense during El Nin?o situations,
a shortened El Nin?o?Southern Oscillation cycle because of global warming likely
enhances the acid deposition at our study forest.
Fleischbein, K.; Wilcke, W.; Valarezo, C.; Zech, W. & Knoblich, K. (2006): Water budgets of three small catchments under montane forest in Ecuador: experimental and modelling approach. Hydrological Processes 20, 2491-2507.
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DOI: 10.1002/hyp.6212
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Abstract:
Abstract:
The water budget of forested catchments controls the local water supply and influences the regional climate. To assess anthropogenic impact on the water cycle we constructed a water budget for three ~10 ha catchments under lower montane forest on the east-facing slope of the Andes in south Ecuador at 1900-2150 m elevation. We used field hydrological measurements and modeled surface flows with TOPMODEL, a semi-distributed catchment model. We measured incident precipitation, throughfall, stemflow, and surface flow between May 1998 and April 2002 in hourly to weekly resolution, and determined all variables needed to parameterize TOPMODEL. On average of the four monitored years and three catchments, incident precipitation was 2504±s.d.123 mm, throughfall 1473±197 mm, and stemflow 25±2 mm yr-1. Fog water input was negligible. Mean annual interception loss in the forest was 1006±270 mm, and mean annual surface flow, calculated with TOPMODEL in an hourly resolution was 1039±48 mm. The resulting mean annual evapotranspiration was 1466±161 mm of which 32% (=471±162 mm) was transpiration if evaporation from the soil was neglected. Our study catchments show a high evapotranspiration attributable to the strong solar insolation near the equator, the small impact of fog, the generally low intensity of incident precipitation and additional wind-driven advective energy input.
Zimmermann, A.; Wilcke, W. & Elsenbeer, H. (2007): Spatial and temporal patterns of throughfall quantity and quality in a tropical montane forest in Ecuador.. Journal of Hydrology 343, 80-96.
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DOI: 10.1016/j.jhydrol.2007.06.012
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Abstract:
Abstract:
In forests, complex canopy processes control the change in volume and chemical composition of rain water. We hypothesize that (i) spatial patterns, (ii) the temporal stability of spatial patterns, and (iii) the temporal course of solute concentrations can be used to explore these processes. The study area at 1950 m above sea level in the south Ecuadorian Andes is far away from anthropogenic emission sources and marine influences. It received ca. 2200 mm of rain annually. We collected rain and throughfall on an event and within-event basis for five precipitation periods between August and October 2005 at up to 25 sites and analyzed the samples for pH and concentrations of , , , , , , , , and total N ( ), P ( ), and organic C ( ). Cumulative throughfall amounted to 79% of rainfall. Compared with other tropical forests, rainfall solute concentrations were low and throughfall solute concentrations similar. Volumes and solute concentrations of rainfall were spatially and temporally little variable. The spatial coefficient of variation for throughfall volumes was 53%, for solute concentrations 28292%, and for deposition 33252%. Temporal persistence of spatial patterns was high for throughfall volumes and varied among solutes. Spatial patterns of , and concentrations in throughfall were highly persistent. The spatial patterns of throughfall fluxes were less stable than those of concentrations. During a monitoring time of 72 hours, solute concentrations in throughfall of selected rain events remained at a similar level indicating that the leachable element pool in the canopy was not exhausted. Our results demonstrate that the passage of rain through the canopy of a tropical montane forest in Ecuador results in a spatially heterogeneous throughfall pattern with a considerable stability during three months. There is a large leachable element pool in the canopy, which is not depleted by the typical light rain within 72 hours.
Wilcke, W.; Oelmann, Y.; Schmitt, A.; Valarezo, C.; Zech, W. & Homeier, J. (2008): Soil properties and tree growth along an altitudinal transect in Ecuadorian tropical montane forest. Journal of Plant Nutrition and Soil Science 171, 220-230.
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DOI: 10.1002/jpln.200625210
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Abstract:
Abstract:
In tropical montane forests, soil properties change with altitude and tree growth decreases. In a tropical montane forest in Ecuador, we determined soil and tree properties along an altitudinal transect between 1960 and 2450 m above seal level. In different vegetation units height, basal area, and diameter growth of trees were recorded, and all horizons of three replicate profiles at each of eight sites were sampled. We determined pH and total concentrations of Al, C, Ca, K, Mg, Mn, N, Na, P, S, Zn, polyphenols, and lignin in all soil horizons and in the mineral soil additionally the effective cation-exchange capacity (ECEC). The soils were Cambisols, Planosols, and Histosols. The concentrations of Mg, Mn, N, P, and S in the O horizons and of Al, C, and all nutrients except Ca in the A horizons correlated significantly negatively with altitude. The C/N, C/P, and C/S ratios increased and the lignin concentrations decreased in O and A horizons with increasing altitude. Forest stature, tree basal area, and tree growth decreased with altitude. An ANOVA analysis indicated that macronutrients (e.g., N, P, Ca) and micronutrients (e.g., Mn) in the organic layer and in the soil mineral A horizon were correlated with tree growth. Furthermore, lignin concentrations in the organic layer and the C/N ratio in soil affected tree growth. These effects were consistent, even if the effect of altitude was accounted for in a statistical hierarchical model. This suggests a contribution of nutrient deficiencies to reduced tree growth possibly caused by reduced organic matter turnover at higher altitudes.