Publications
Found 861 publication(s)
- of type
Urgiles , N.; Haug, I.; Setaro, S. & Aguirre, N. 2016: Introduction to Mycorrhizas in the Tropics with Emphasis on the Montane Forest in Southern Ecuador.: Estudios de Bioversidad 4 (EDILOJA Cía. Ltda., Loja).
Schlaeppi, K.; Bender, S.F.; Mascher, F.; Russo, G.; Patrignani, A.; Camenzind, T.; Hempel, S.; Rillig, M.C. & van der Heijden, M.G. (2016): High-resolution community profiling of arbuscular mycorrhizal fungi. New Phytologist xx, xx.
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DOI: 10.1111/nph.14070
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Abstract:
Abstract:
Summary
Community analyses of arbuscular mycorrhizal fungi (AMF) using ribosomal small subunit
(SSU) or internal transcribed spacer (ITS) DNA sequences often suffer from low resolution or
coverage. We developed a novel sequencing based approach for a highly resolving and specific profiling of AMF communities.
We took advantage of previously established AMF-specific PCR primers that amplify a
c. 1.5-kb long fragment covering parts of SSU, ITS and parts of the large ribosomal subunit
(LSU), and we sequenced the resulting amplicons with single molecule real-time (SMRT)
sequencing.
The method was applicable to soil and root samples, detected all major AMF families and
successfully discriminated closely related AMF species, which would not be discernible using
SSU sequences. In inoculation tests we could trace the introduced AMF inoculum at the
molecular level. One of the introduced strains almost replaced the local strain(s), revealing
that AMF inoculation can have a profound impact on the native community.
The methodology presented offers researchers a powerful new tool for AMF community
analysis because it unifies improved specificity and enhanced resolution, whereas the drawback of medium sequencing throughput appears of lesser importance for low-diversity groups
such as AMF.
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Keywords: |
arbuscular mycorrhiza |
mycorrhiza |
Crowther, T. & et, a. (2015): Mapping tree density at a global scale. Nature 525(7568), 201-205.
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DOI: 10.1038/nature14967
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Abstract:
Abstract:
The global extent and distribution of forest trees is central to our understanding of the terrestrial biosphere. We provide the first spatially continuousmap of forest tree density at a global scale. This mapreveals that the global numberof trees is approximately 3.04 trillion, an order of magnitude higher than the previous estimate. Of these trees, approximately 1.39 trillion exist in tropical and subtropical forests, with 0.74 trillion in boreal regions and 0.61 trillion in temperate
regions. Biome-level trends in tree density demonstrate the importance of climate and topography in controlling local tree densities at finer scales, as well as the overwhelming effect of humans across most of the world. Based on our projected tree densities, we estimate that over 15 billion trees are cut down each year, and the global number of trees has fallen by approximately 46% since the start of human civilization.
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Keywords: |
tree density |
Slik, F. & et, a. (2015): An estimate of the number of tropical tree species. PNAS 112(24), 7472-7477.
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DOI: 10.1073/pnas.1423147112
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Abstract:
Abstract:
The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database
from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher’s alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ?40,000 and ?53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ?19,000–25,000 tree species. Continental Africa is relatively depauperate with a minimumof ?4,500–6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa.
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Keywords: |
tree species richness |
tree species |
Silva, B.; Strobl, S.; Beck, E. & Bendix, J. (2016): Canopy evapotranspiration, leaf transpiration and water use efficiency of an Andean pasture in SE-Ecuador – a case study. Erdkunde 70(1), 5-18.
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DOI: 10.3112/erdkunde.2016.01.02
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Abstract:
Abstract:
The relationship between canopy-level evapotranspiration (ETSci) and leaf-level transpiration (Tleaf) as well as photosynthesis (Pleaf) for a homogeneous tropical montane pasture was analyzed over five days using a combination of methods involving a laser scintillometer and a porometer. Weather conditions ranged from overcast to sunny during the period of study. The gas exchange of the leaves of the dominant pasture grass Setaria sphacelata (transpiration vs. photosyn¬thetic CO2 net uptake ) was measured with a porometer and physiologically interpreted on the background of microclimate variables (photosynthetic active radiation (PAR) as proxy for total light intensity, temperature, water vapor deficit of the air) and soil moisture data. Water use efficiency (WUE, photosynthetic CO2 net uptake vs water loss by leaf transpiration) of the pasture was used to analyze the grass’ range of response to the environmental variables of the research area. PAR and water vapor deficit of the air (VPD) appeared to be the determinant factors for Tleaf and ETSci. WUE for the Setaria sphacelata pasture ranged from 1.9 to 5.8 ?mol CO2 mmol-1 H20 day-1 and is particularly low during periods of high VPD combined with enhanced insolation during cloudless periods. ET measurements collected by the scintillometer demonstrated a strong correlation with water flux calculated using the Penman-Monteith approach (TPM) (r² = 0.95). Also, Tleaf measured with the porometer showed reasonable coincidence with the ET observations (r² = 0.78). Values of ETSci ranged from 2.26 to 4.96 mm day-1 and Tleaf ranged from 0.83 to 2.41 mm day-1, but only ETSci showed good correspondence with the available energy (net radiation). The lower correlation between Tleaf and canopy-level ETSci compared to that between ETSci and TPM was tested against contaminations from the adjacent fetch area of the scintillometer path, but no effects were found. Likewise, soil water limitations of Tleaf could be ruled out. Therefore, different correlations of ETSci and Tleaf with the incoming energy and VPD may be traced back to a direct effect of the VPD on ET in contrast to its indirect effect on Tleaf which is additionally regulated by physiological processes in the leaf stomata.
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Keywords: |
Porometry |
Setaria |
Evapotranspiration |
scintillometry |
Adams, M. & Fiedler, K. (2016): Low Herbivory among Targeted Reforestation Sites in the Andean Highlands of Southern Ecuador.. PLoS ONE 11(3), e0151277.
Adams, M. & Fiedler, K. (2015): The value of targeted reforestations for local insect diversity: a case study from the Ecuadorian Andes.. Biodiversity and Conservation 24, 2709-2734.
Kübler, D.; Hildebrandt, P.; Günter, S.; Stimm, B.; Weber, M.; Mosandl, R.; Munoz, J.; Cabrera, O.; Aguirre, N.; Zeilinger, J. & Silva, B. (2016): Assessing the importance of topographic variables for the spatial distribution of tree species in a tropical mountain forest. Erdkunde 70(1), 19-47.
Tiede, Y.; Homeier, J.; Cumbicus Torres, N.; Pena Tamayo, J.E.; Albrecht, J.; Ziegenhagen, B.; Bendix, J.; Brandl, R. & Farwig, N. (2016): Phylogenetic niche conservatism does not explain elevational patterns of species richness, phyodiversity and family age of tree assemblages in Andean rainforest. Erdkunde 70(1), 83-106.
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DOI: 10.3112/erdkunde.2016.01.06
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Abstract:
Abstract:
Phylogenetic niche conservatism (PNC) is the tendency of species within a clade to retain ancestral traits and
to persist in their primary ecological niches on geological time scales. It links evolutionary and ecological processes and has
been hypothesized to explain patterns of species richness and the composition of species assemblages. Decreasing patterns
of species richness along latitudinal gradients were often explained by the combination of ancient tropical climates, trait
retention of tropical lineages and environmental filtering. PNC also predicts decreasing phylodiversity and family age with
decreasing tropicality and has been invoked to explain these patterns along climatic gradients across latitudinal as well as elevational
gradients.
However,
recent
studies
on
tree
assemblages
along
latitudinal
and
elevational
gradients
in
South
America
found
patterns
contradicting
the
PNC
framework.
Our
study
aims
to
shed
light
on
these
contradictions
using
three
different
metrics of the phylogenetic composition that form a gradient from recent evolutionary history to deep phylogenetic
relationships. We analyzed the relationships between elevation and taxonomic species richness, phylodiversity and family
age of tree assemblages in Andean rainforests in Ecuador. In contrast to predictions of the PNC we found no associations
of elevation with species richness of trees and increasing clade level phylodiversity and family age of the tree assemblages
with elevation. Interestingly, we found that patterns of phylodiversity across the studied elevation gradient depended especially
on
the
deep
nodes
in
the
phylogeny.
We
therefore
suggest
that
the
dispersal
of
evolutionarily old plant lineages with
extra-tropical origins influences the recent composition of tree assemblages in the Andes. Further studies spanning broader
ecological gradients and using better resolved phylogenies to estimate family and species ages are needed to obtain a deeper
mechanistic understanding of the processes that drive the assembly of tree communities along elevational gradients.
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Keywords: |
Ecuador |
vegetation geography |
tree species assembly |
elevational gradient |
orogeny |
Wagner, F.H.; Bräuning, A.; Homeier, J.; Spannl, S.; Volland, F. & et, a. (2016): Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests. Biogeosciences 13, 2537–2562.
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DOI: 10.5194/bg-13-2537-2016
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Abstract:
Abstract:
The seasonal climate drivers of the carbon cycle
in tropical forests remain poorly known, although these
forests account for more carbon assimilation and storage than
any other terrestrial ecosystem. Based on a unique combination
of seasonal pan-tropical data sets from 89 experimental
sites (68 include aboveground wood productivity measurements
and 35 litter productivity measurements), their associated
canopy photosynthetic capacity (enhanced vegetation
index, EVI) and climate, we ask how carbon assimilation
and aboveground allocation are related to climate seasonality
in tropical forests and how they interact in the seasonal
carbon cycle. We found that canopy photosynthetic capacity
seasonality responds positively to precipitation when rainfall
is < 2000mm/yr (water-limited forests) and to radiation
otherwise (light-limited forests). On the other hand, independent
of climate limitations, wood productivity and litterfall
are driven by seasonal variation in precipitation and
evapotranspiration, respectively. Consequently, light-limited
forests present an asynchronism between canopy photosynthetic
capacity and wood productivity. First-order control by
precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000mm/yr.
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Keywords: |
climate |
tree growth |
litterfall |
Fadrique, B. & Homeier, J. (2016): Elevation and topography influence community structure, biomass and host tree interactions of lianas in tropical montane forests of southern Ecuador. Journal of Vegetation Science 27, 958-968.
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DOI: 10.1111/jvs.12427
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Abstract:
Abstract:
Questions: How does the structure of liana communities (diameter, density and biomass) in tropical montane forests vary along elevation and topographic gradients? How do patterns of tree infestation vary with elevation? Is tree diameter growth reduced by lianas in tropicalmontane forest?
Location: Tropical Andean forests (1000–3000 m a.s.l.) in the San Francisco Reserve and in the Podocarpus National Park, southern Ecuador.
Methods: All lianas (DBH ? 1 cm) were censused in 54 permanent plots (20 9 20 m) equally distributed between three study sites (1000, 2000 and 3000 m a.s.l.) and three topographic positions (lower, mid and upper slope) per site (six replicate plots at each site by position combination). The DBH and number of lianas hosted was recorded for all trees (DBH ? 10 cm). Liana biomass
was estimated using allometric equations. ANOVAs were used to test for effects of elevation and slope positions on liana parameters and proportion of trees infested. The relationships between liana biomass and tree parameters and environmental
parameters were analysed with partial least squares regression. We
used the available literature data to perform a regression analysis of liana biomass in response to elevation in humid tropical old-growth forests between sea level and 3000 ma.s.l.
Results: Liana diameter, density and biomass all decrease with elevation. The decreasing liana biomass agrees with results from previous studies of liana biomass in other humid tropical forests, indicating a decrease of 0.18 Mg/ha liana biomass per 100 m of elevation gain. Topographic variation leads to thinner but more abundant stems upslope; there was no effect of topographic position on liana biomass. Liana biomass and liana infestation are both positively correlated with host tree DBH at every elevation. Tree diameter growth is reduced by liana
infestation; the proportion of infested trees is lower in Andean montane forests than in tropical lowland forests.
Conclusions: Liana biomass distribution and tree infestation vary significantly with elevation. Biomass of lianas and relative contribution of lianas to total above-ground biomass both decrease with elevation. Topographic effects likely result fromhigher soil fertility at lower slope positions.
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Keywords: |
tree growth |
MATRIX |
elevation |
liana |
liana biomass |
Knoke, T.; Paul, C.; Hildebrandt, P.; Calvas, B.; Castro, L.M.; Härtl, F.; Döllerer, M.; Hamer, U.; Windhorst, D.; Wiersma, Y.; Curatola Fernández, G.F.; Obermeier, W.A.; Adams, J.; Breuer, L.; Mosandl, R.; Beck, E.; Weber, M.; Stimm, B.; Haber, W.; Fürst, C. & Bendix, J. (2016): Compositional diversity of rehabilitated tropical lands supports multiple ecosystem services and buffers uncertainties. Nature Communications 7, Article number:11877.
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DOI: 10.1038/ncomms11877
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Abstract:
Abstract:
High landscape diversity is assumed to increase the number and level of ecosystem services. However, the interactions between ecosystem service provision, disturbance and landscape composition are poorly understood. Here we present a novel approach to include uncertainty in the optimization of land allocation for improving the provision of multiple ecosystem services. We refer to the rehabilitation of abandoned agricultural lands in Ecuador including two types of both afforestation and pasture rehabilitation, together with a succession option. Our results show that high compositional landscape diversity supports multiple ecosystem services (multifunction effect). This implicitly provides a buffer against uncertainty. Our work shows that active integration of uncertainty is only important when optimizing single or highly correlated ecosystem services and that the multifunction effect on landscape diversity is stronger than the uncertainty effect. This is an important insight to support a land-use planning based on ecosystem services.
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Keywords: |
ecosystem services |
South Ecuador |
sustainable land use |
land use modeling |
restoration |
Ochoa Moreno, S.; Paul, C.; Castro, L.M.; Valle, L. & Knoke, T. (2016): Banning goats could exacerbate deforestation of the Ecuadorian dry forest - How the effectiveness of conservation payment is influenced by productive use options. Erdkunde 70(1), 49-67.
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DOI: 10.3112/erdkunde.2016.01.04
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Abstract:
Abstract:
Due to ongoing conversion of the dry forests of southern Ecuador to pasture and farmland, they are among the most threatened ecosystems globally. This study explored how to control deforestation in the region while securing the livelihoods of local people through land-use diversification and compensation payments. Results are based on interview data collected from 163 households near the Laipuna Reserve in southern Ecuador. Combining modern financial theory and von Thünen’s theory of land distribution, we optimized land-use shares of two types of forest management (banning and allowing goat grazing) and three crops (maize, beans and peanuts). Land-use portfolios were calculated for four different farm sizes, represented by the quartiles of the farm size distribution. We found that goat grazing was important for diversifying farm income and reducing financial risks for all farm sizes. However, forest area would still be converted to cropland under the current financial coefficients. The amount of compensation needed to maintain current forest cover was calculated for two different scenarios: 1) banning goat grazing and 2) allowing forest use where the farmer could decide how much forest area would be allocated to each land-use option. Offering financial compensation for forest preservation (Scenario 1) reduced deforestation but would still lead to a conversion of at least 23?% of current forests to croplands. Allowing forest use in a compensation scheme (Scenario 2) would help retain 96?% of the current forest cover, with 29?% of this forest being set aside for conservation. This scenario would suppose annual payments ranging from $4 to $89 ha-1, with the largest farms requiring the lowest payments. In contrast, banning goats from the forest would even risk losing the entire forest area to cropland, if compensation fell below $50 ha-1 yr-1. We conclude that coupling productive options with secure compensation payments and developing policies that support land-use diversification and sustainable use of forest resources, will be most effective in conserving the Ecuadorian dry forest.
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Keywords: |
silvopasture |
land change modelling |
Laipuna |
land use change |
financial modeling of land-use shares |
dry forest |
socio bosque |
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 |
Dietrich, K.; Spöri, E. & Oelmann, Y. (2016): Nutrient addition modifies phosphatase activities along an altitudinal gradient in a tropical montane forest in Southern Ecuador. Frontiers in Earth Science 4, 1-9.
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DOI: 10.3389/feart.2016.00012
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Abstract:
Abstract:
Atmospheric nutrient deposition and climate change are expected to endanger the diversity of tropical forest ecosystems. Nitrogen (N) deposition might influence nutrient fluxes beyond the N cycle by a concomitant increased demand for other nutritional elements such as phosphorus (P). Organisms might respond to the increased P demand by enhanced activity of enzymes involved in releasing inorganic P from organic matter (OM). Our aims were to assess the effect of i) climate shifts (approximated by an altitudinal gradient), and ii) nutrient addition (N, P, N+P) on phosphatase activity (PA) in organic layer and mineral soil of a tropical montane rainforest in Southern Ecuador. A nutrient manipulation experiment (NUMEX) was set up along an altitudinal gradient (1000, 2000, and 3000 m a.s.l.). We determined PA and inorganic and total P concentrations. PA at 1000 m was significantly lower (mean ± standard error: 48 ± 20 µmol p-NP g-1 dm h-1) as compared to 2000 m and 3000 m (119 ± 11 and 137 ± 19, respectively). One explanation might be that very rapid decomposition of OM at 1000 m results in very thin organic layers reducing the stabilization of enzymes and thus, resulting in leaching loss of enzymes under the humid tropical climate. We found no effect of N addition on PA neither in the organic layer nor in mineral soil, probably because of the low nutrient addition rates that showed ambiguous results so far on productivity measures as a proxy for P demand. In the organic layers of P and N+P treatments, we found decreased PA and increased concentrations of inorganic P. This indicates that the surplus of inorganic P reduced the biosynthesis of phosphatase enzymes. PA in megadiverse montane rainforests is likely to be unaffected by increased atmospheric N deposition but reduced upon atmospheric P deposition.
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Keywords: |
Ecuador |
NUMEX |
phosphorus |
fertilization |
tropical montane forest |
phosphatase activity |
Spannl, S.; Volland, F.; Pucha Cofrep, D.A.; Peters, T.; Cueva, E. & Bräuning, A. (2016): Climate variability, tree increment patterns and ENSO-related carbon sequestration reduction of the tropical dry forest species Loxopterygium huasango of Southern Ecuador. Trees Structure and Function e(e), e.
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DOI: DOI 10.1007/s00468-016-1362-0
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Abstract:
Abstract:
We present the first multi-year long time series
of local climate data in the seasonally dry tropical forest in
Southern Ecuador and related growth dynamics of Loxopterygium
huasango, a deciduous tree species. Local climate
was investigated by installing an automatically
weather station in 2007 and the daily tree growth variability
was measured with high-resolution point dendrometers.
The climatic impact on growth behaviour was
evaluated. Hydro-climatic variables, like precipitation and
relative humidity, were the most important factors for
controlling tree growth. Changes in rainwater input affected
radial increment rates and daily amplitudes of stem
diameter variations within the study period from 2009 to
2013. El Nin˜o Southern Oscillation (ENSO) related
variations of tropical Pacific Ocean sea surface temperatures
influenced the trees’ increment rates. Average radial
increments showed high inter-annual (up to 7.89 mm) and
inter-individual (up to 3.88 mm) variations. Daily amplitudes
of stem diameter variations differed strongly between
the two extreme years 2009 (wet) and 2011 (dry). Contrary
to 2009, the La Nin˜a drought in 2011 caused a rapid
reduction of the daily amplitudes, indicating a total cessation
(‘growth collapse’) of stem increment under ENSOrelated
drought conditions and demonstrating the high
impact of climatic extreme events on carbon sequestration
of the dry tropical forest ecosystem.
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Keywords: |
Ecuador |
dendrometer |
dendroecology |
Climate variability |
La Nina drought |
Seasonally dry tropical forest |
Spannl, S.; Homeier, J. & Bräuning, A. (2016): Nutrient-Induced Modifications of Wood Anatomical Traits of Alchornea lojaensis (Euphorbiaceae). Frontiers in Earth Science 4(50), 1-11.
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DOI: 10.3389/feart.2016.00050
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Abstract:
Abstract:
Regarding woody plant responses on higher atmospheric inputs of the macronutrients nitrogen (N) and phosphorous (P) on tropical forests in the future, an adaptive modification of wood anatomical traits on the cellular level of woody plants is expected. As part of an interdisciplinary nutrient manipulation experiment (NUMEX) carried out in Southern Ecuador, we present here the first descriptive and quantitative wood anatomical analysis of the tropical evergreen tree species Alchornea lojaensis (Euphorbiaceae). We sampled branch wood of nine individual trees belonging to treatments with N fertilization, N+P fertilization, and a control group, respectively. Quantitative evaluations of eleven different vessel parameters were conducted. The results showed that this endemic tree species will be able to adapt well to the future effects of climate change and higher nutrient deposition. This was firstly implied by an increase in vessel diameter and consequently a higher theo. area-specific hydraulic conductivity with higher nutrient availability. Secondly, the percentage of small vessels (0–20 ?m diameter) strongly increased with fertilization. Thirdly, the vessel arrangement (solitary vessels vs. multiple vessel groupings) changed toward a lower percentage of solitary vessel fraction (VS), and concurrently toward a higher total vessel grouping index (VG) and a higher mean group size of non-solitary vessels (VM) after N and N+P addition. We conclude that higher nutrient availability of N and N+P triggered higher foliage amount and water demand, leading to higher cavitation risk in larger vessels. This is counteracted by a stronger grouping of vessels with smaller risk of cavitation to ensure water supply during drier periods that are expected to occur in higher frequency in the near future.
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Keywords: |
fertilization |
branch wood |
evergreen tropical montane forest |
Euphorbiaceae |
quantitative wood anatomy |
Ließ, M.; Schmidt, J. & Glaser, B. (2016): Improving the spatial prediction of soil organic carbon stocks in a complex tropical mountain landscape by methodological specifications in machine learning approaches. PLOS ONE 11(4), 1-22.
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DOI: 10.1371/journal.pone.0153673
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Abstract:
Abstract:
Tropical forests are significant carbon sinks and their soils’ carbon storage potential is immense. However, little is known about the soil organic carbon (SOC) stocks of Tropical mountain areas whose complex soil-landscape and difficult accessibility pose a challenge to spatial analysis. The choice of methodology for spatial prediction is of high importance to improve the expected poor model results in case of low predictor-response correlations. Four aspects were considered to improve model performance in predicting SOC stocks of the organic layer of a tropical mountain forest landscape: Different spatial predictor settings, predictor selection strategies, various machine learning algorithms and model tuning. Five machine learning algorithms: random forests, artificial neural networks,
multivariate adaptive regression splines, boosted regression trees and support
vector machines were trained and tuned to predict SOC stocks from predictors derived
from a digital elevation model and satellite image. Topographical predictors were calculated with a GIS search radius of 45 to 615 m. Finally, three predictor selection strategies were applied to the total set of 236 predictors. All machine learning algorithms—including the model tuning and predictor selection—were compared via five repetitions of a tenfold cross-validation. The boosted regression tree algorithm resulted in the overall best model. SOC stocks ranged between 0.2 to 17.7 kg m-2, displaying a huge variability with diffuse insolation and curvatures of different scale guiding the spatial pattern. Predictor selection and model tuning improved the models’ predictive performance in all five machine learning algorithms. The rather low number of selected predictors favours Forward compared to backward selection procedures. Choosing predictors due to their indiviual performance was vanquished by the two procedures which accounted for predictor interaction.
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Keywords: |
soil organic carbon |
digital soil mapping |
Wallis, C.; Paulsch, D.; Zeilinger, J.; Silva, B.; Curatola Fernández, G.F.; Brandl, R.; Farwig, N. & Bendix, J. (2016): Contrasting performance of Lidar and optical texture models in predicting avian diversity in a tropical mountain forest. Remote sensing of environment 174, 223-232.
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DOI: 10.1016/j.rse.2015.12.019
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Abstract:
Abstract:
Ecosystems worldwide are threatened by the increasing impact of land use and climate change. To protect their diversity and functionality, spatially explicit monitoring systems are needed. In remote areas, monitoring is difficult and recurrent field surveys are costly. By using Lidar or themore cost-effective and repetitive optical satellite data, remote sensing could provide proxies for habitat structure supporting measures for the conservation of biodiversity. Here we compared the explanatory power of both, airborne Lidar and optical satellite data in modeling the spatial distribution of biodiversity of birds across a complex tropical mountain forest ecosystem in southeastern Ecuador. Weused data fromfield surveys of birds and chose three measures as proxies for different aspects of diversity: (i) Shannon diversity as a measure of ?-diversity that also includes the relative abundance of species, (ii) phylodiversity as a first proxy for functional diversity, and (iii) community composition as a proxy for combined ?- and ?-diversity.We modeled these diversity estimates using partial least-square regression of Lidar and optical texturemetrics separately and compared themodels using a leave-one-out validated R2 and rootmean square error. Bird community informationwas best predicted by both remote sensing datasets, followed by Shannon diversity and phylodiversity. Our findings reveal a high potential of optical texture metrics for predicting Shannon diversity and ameasure of community composition, but not for modeling phylodiversity.
Generalizing from the investigated tropicalmountain ecosystem,we conclude that texture information retrieved frommultispectral data of operational satellite systems could replace costly airborne laser-scanning formodeling certain aspects of biodiversity.
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Keywords: |
forest structure |
LiDAR |
QuickBird |
topographic heterogenity |
bird community |
Birds |
Schlautmann, J. (2016): Predator richness, elevation and rainfall seasonality: direct and indirect effects on artificial caterpillar predation University of Marburg, master thesis
Greiner, L. (2016): Texture images as tool for predicting bird feeding guilds in a tropical montane rainforest University of Marburg, master thesis
Ahlers, J. (2016): Variabilität der Feinstreuquantität und -qualität sowie die Auswirkungen einer kontinuierlichen N und P Düngung entlang eines Höhengradienten im tropischen Bergregenwald Südecuadors University of Goettingen, bachelor thesis
Liedtke, R. (2016): Mobile and Soil Bonded Phosphomonoesterase Activity of the Organic Layer along an Altitudinal Gradient in South Ecuador University of Tuebingen, bachelor thesis
Homeier, J. 2008: Potential Vegetation and Floristic Composition of Andean Forests in South Ecuador, with a Focus on the RBSF. (Springer).
Carrillo Rojas, G.; Silva, B.; Cordova, M.; Celleri, R. & Bendix, J. (2016): Dynamic Mapping of Evapotranspiration Using an Energy Balance-Based Model over an Andean Páramo Catchment of Southern Ecuador. Remote Sensing 8(2), 160 (1-24).
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DOI: 10.3390/rs8020160
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Abstract:
Abstract:
Understanding of evapotranspiration (ET) processes over Andean mountain environments is crucial, particularly due to the importance of these regions to deliver water-related ecosystem services. In this context, the detection of spatio-temporal changes in ET remains poorly investigated for specific Andean ecosystems, like the páramo. To overcome this lack of knowledge, we implemented the energy-balance model METRIC with Landsat 7 ETM+ and MODIS-Terra imagery for a páramo catchment. The implementation contemplated adjustments for complex terrain in order to obtain daily, monthly and annual ET maps (between 2013 and 2014). In addition, we compared our results to the global ET product MOD16. Finally, a rigorous validation of the outputs was conducted with residual ET from the water balance. ET retrievals from METRIC (Landsat-based) showed good agreement with the validation-related ET at monthly and annual steps (mean bias error <8 mm·month?1 and annual deviation <17%). However, METRIC (MODIS-based) outputs and the MOD16 product were revealed to be unsuitable for our study due to the low spatial resolution. At last, the plausibility of METRIC to obtain spatial ET retrievals using higher resolution satellite data is demonstrated, which constitutes the first contribution to the understanding of spatially-explicit ET over an alpine catchment in the neo-tropical Andes.
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Keywords: |
Ecuador |
Páramo |
remote sensing |
Andes |
Landsat |
Evapotranspiration |
Tropical Mountains |
METRIC |
MODIS |
Lopez, G. (2015): Effects of experimental nutrient additions on root architecture of tropical montane forest trees in South Ecuador University of Goettingen, master thesis
Barros Sulca, D.C. (2015): A land-use allocation model for Ecuador using site-specific land-use restrictions Institute of Forest Management, Technische Universität München, master thesis
Camenzind, T.; Papathanasiou, H.J.; Förster, A.; Dietrich, K.; Hertel, D.; Homeier, J.; Oelmann, Y.; Olsson, P.A.; Suarez, J.P. & Rillig, M.C. (2016): Increases in Soil Aggregation Following Phosphorus Additions in a Tropical Premontane Forest are Not Driven by Root and Arbuscular Mycorrhizal Fungal Abundances. Frontiers in Earth Science 3(89), e.
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DOI: 10.3389/feart.2015.00089
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Abstract:
Tropical ecosystems have an important role in global change scenarios, in part because they serve as a large terrestrial carbon pool. Carbon protection is mediated by soil aggregation processes, whereby biotic and abiotic factors influence the formation and stability of aggregates. Nutrient additions may affect soil structure indirectly by simultaneous shifts in biotic factors, mainly roots, and fungal hyphae, but also via impacts on abiotic soil properties. Here, we tested the hypothesis that soil aggregation will be affected by nutrient additions primarily via changes in arbuscular mycorrhizal fungal (AMF) hyphae and root length in a pristine tropical forest system. Therefore, the percentage of water-stable macroaggregates (> 250 ?m) (WSA) and the soil mean weight diameter (MWD) was analyzed, as well as nutrient contents, pH, root length, and AMF abundance. Phosphorus additions significantly increased the amount of WSA, which was consistent across two different sampling times. Despite a positive effect of phosphorus additions on extra-radical AMF biomass, no relationship between WSA and extra-radical AMF nor roots was revealed by regression analyses, contrary to the proposed hypothesis. These findings emphasize the importance of analyzing soil structure in understudied tropical systems, since it might be affected by increasing nutrient deposition expected in the future.
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Keywords: |
NUMEX |
Camenzind, T.; Homeier, J.; Dietrich, K.; Hempel, S.; Hertel, D.; Krohn, A.; Leuschner, C.; Oelmann, Y.; Olsson, P.A.; Suarez, J.P. & Rillig, M.C. (2016): Opposing effects of nitrogen versus phosphorus additions on mycorrhizal fungal abundance along an elevational gradient in tropical montane forests. Soil Biology & Biochemistry 94, 37-47.
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DOI: 10.1016/j.soilbio.2015.11.011
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Abstract:
Abstract:
Studies in temperate systems provide evidence that the abundance of arbuscular mycorrhizal fungal (AMF) depends on soil nutrient availability, which is mainly explained in the context of resource stoichiometry and differential plant biomass allocation. We applied this concept to an understudied ecosystem – tropical montane forest – analyzing root and AMF abundance along an elevational gradient with decreasing nutrient availability, combined with responses to nitrogen (N) versus phosphorus (P) additions. At three sites from 1000 to 3000 m above sea-level we analyzed fine root length, AMF root colonization as well as extraradical AMF biomass (neutral lipid fatty acid 16:1?5, hyphal length and spore counts) in a nutrient manipulation experiment. We found a significant increase in root length as well as intra- and extraradical AMF abundance with elevation. Overall, P additions significantly increased, whereas N additions decreased AMF abundance, with differential though nonsystematic changes along the elevational gradient. Strongest effects were clearly observed at the intermediate site. These findings suggest a general dependency of roots and AMF on nutrient availability, though responses to N and P additions differed from previous studies in temperate systems. In the context of future nutrient depositions, results suggest diverging responses of AMF abundance depending on site characteristics.
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Keywords: |
NUMEX |
Bombuscaro |
AM fungi |
arbuscular mycorrhiza |
nutrient cycle |
Nutrient deposition |
Wallis, C.; Paulsch, D.; Zeilinger, J.; Silva, B.; Curatola Fernández, G.F.; Brandl, R.; Farwig, N. & Bendix, J. (2016): Contrasting performance of Lidar and optical texture models in predicting avian diversity in a tropical mountain forest. Remote Sensing of Environment 174, 223-232.
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DOI: 10.1016/j.rse.2015.12.019
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Abstract:
Abstract:
Ecosystems worldwide are threatened by the increasing impact of land use and climate change. To protect their diversity and functionality, spatially explicit monitoring systems are needed. In remote areas, monitoring is difficult and recurrent field surveys are costly. By using Lidar or themore cost-effective and repetitive optical satellite data, remote sensing could provide proxies for habitat structure supporting measures for the conservation of biodiversity. Here we compared the explanatory power of both, airborne Lidar and optical satellite data in modeling the spatial distribution of biodiversity of birds across a complex tropical mountain forest ecosystem in southeastern Ecuador. Weused data fromfield surveys of birds and chose three measures as proxies for different aspects of diversity: (i) Shannon diversity as a measure of ?-diversity that also includes the relative abundance of species, (ii) phylodiversity as a first proxy for functional diversity, and (iii) community composition as a proxy for combined ?- and ?-diversity.We modeled these diversity estimates using partial least-square regression of Lidar and optical texturemetrics separately and compared themodels using a leave-one-out validated R2 and rootmean square error. Bird community informationwas best predicted by both remote sensing datasets, followed by Shannon diversity and phylodiversity. Our findings reveal a high potential of optical texture metrics for predicting Shannon diversity and ameasure of community composition, but not for modeling phylodiversity.
Generalizing from the investigated tropical mountain ecosystem, we conclude that texture information retrieved frommultispectral data of operational satellite systems could replace costly airborne laser-scanning formodeling certain aspects of biodiversity.
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Keywords: |
Biodiversity |
Southern Ecuador |
beta diversity |
Lidar |
Quickbird |
Phylodiversity |
Alpha diversity |
Shannon diversity |
Community composition |
Birds |
Partial least-square regression |
Gray level co-occurrence matrix |