Publikationen
Es wurden 516 Publikationen gefunden
- vom Typ: article
Graefe, S.; Fang, D. & Butz, P. (2019): Water residence times in trees of a neotropical dry forest. Trees 1, 1–7.
Butz, P.; Hölscher, D.; Cueva, E. & Graefe, S. (2018): Tree Water Use Patterns as Influenced by Phenology in a Dry Forest of Southern Ecuador. Frontiers in Plant Science 9, 945.
Raffelsbauer, V.; Spannl, S.; Peña , K.; Pucha Cofrep, D.A.; Steppe, K. & Bräuning, A. (2019): Tree Circumference Changes and Species-Specific Growth Recovery After Extreme Dry Events in a Montane Rainforest in Southern Ecuador. Frontiers in Plant Sciences 10, 342.
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DOI: 10.3389/fpls.2019.00342
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Abstract:
Abstract:
Under drought conditions, even tropical rainforests might turn from carbon sinks to sources, and tree species composition might be altered by increased mortality. We monitored stem diameter variations of 40 tree individuals with stem diameters above 10 cm belonging to eleven different tree genera and three tree life forms with high-resolution dendrometers from July 2007 to November 2010 and additionally March 2015 to December 2017 in a tropical mountain rainforest in South Ecuador, a biodiversity hotspot with more than 300 different tree species belonging to different functional types. Although our study area receives around 2200 mm of annual rainfall, dry spells occur regularly during so-called “Veranillo del Niño” (VdN) periods in October-November. In climate change scenarios, droughts are expected with higher frequency and intensity as today. We selected dry intervals with a minimum of four consecutive days to examine how different tree species respond to drought stress, raising the question if some species are better adapted to a possible higher frequency and increasing duration of dry periods. We analyzed the averaged species-specific stem shrinkage rates and recovery times during and after dry periods. The two deciduous broadleaved species Cedrela montana and Handroanthus chrysanthus showed the biggest stem shrinkage of up to 2 mm after 10 consecutive dry days. A comparison of daily circumference changes over 600 consecutive days revealed different drought responses between the families concerning the percentage of days with stem shrinkage/increment, ranging from 27.5 to 72.5% for Graffenrieda emarginata to 45–55% for Podocarpus oleifolius under same climate conditions. Moreover, we found great difference of recovery times after longer-lasting (i.e., eight to ten days) VdN drought events between the two evergreen broadleaved species Vismia cavanillesiana and Tapirira guianensis. While Vismia replenished to pre-VdN stem circumference after only 5 days, Tapirira needed 52 days on average to restore its circumference. Hence, a higher frequency of droughts might increase inter-species competition and species-specific mortality and might finally alter the species composition of the ecosystem.
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Keywords: |
tree growth |
Santillan, V.; Quitian, M.; Tinoco, B.A.; Zarate, E.; Schleuning, M.; Boehning-Gaese, K. & Neuschulz, E. (2018): Different responses of taxonomic and functional bird diversity to forest fragmentation across an elevational gradient. Oecologia x, x-x.
Santillan, V.; Quitian, M.; Tinoco, B.A.; Zarate, E.; Schleuning, M.; Boehning-Gaese, K. & Neuschulz, E. (2018): Temperature and precipitation, but not resource availability drive spatio-temporal variation in bird assemblages along a tropical elevational gradient. PlosOne x, x-x.
Quitian, M.; Santillan, V.; Espinosa, C.I.; Homeier, J.; Boehning-Gaese, K.; Schleuning, M. & Neuschulz, E. (2018): Direct and indirect effects of plant and frugivore diversity on structural and functional components of fruit removal. Oecologia x, x-x.
Quitian, M.; Santillan, V.; Bender, I.M.; Espinosa, C.I.; Homeier, J.; Boehning-Gaese, K.; Schleuning, M. & Neuschulz, E. (2018): Functional responses of avian frugivores to variation of fruit resources in natural and fragmented forests. Functional Ecology x, x-x.
Hanz, D.; Boehning-Gaese, K.; Ferger, S.; Fritz, S.; Neuschulz, E.; Quitian, M.; Santillan, V.; Töpfer, T. & Schleuning, M. (2018): Functional and phylogenetic diversity of bird assemblages are filtered by different environmental drivers. Journal of Biogepgraphy x, x-x.
Bender, I.M.; Kissling, W.; Blendinger, P.; Hensen, I.; Kühn, I.; Munoz, M.; Neuschulz, E.; Nowak, L.; Quitian, M.; Saavedra, F.; Santillan, V.; Töpfer, T.; Wiegand, T.; Dehling, D. & Schleuning, M. (2018): Morphological trait matching shapes plant-frugivore networks across the Andes. Ecography 41(11), 1910-1919.
Bruelheide, H.; Nadrowski, K.; Assmann, T.; Bauhus, J.; Both, S.; Buscot, F.; Chen, X.; Ding, B.; Durka, W. & Erfmeier, A. (2014): Designing forest biodiversity experiments: general considerations illustrated by a new large experiment in subtropical China. Methods in Ecology and Evolution 5(1), 74--89.
Campozano, L.; Trachte, K.; Celleri, R.; Samaniego, E.; Bendix, J.; Cristóbal, A. & Mejia, J.F. (2018): Climatology and Teleconnections of Mesoscale Convective Systems in an Andean Basin in Southern Ecuador: The Case of the Paute Basin. Advances in Meteorology 2018, 1-13.
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DOI: 10.1155/2018/4259191
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Abstract:
Abstract:
Mesoscale convective systems (MCSs) climatology, the thermodynamic and dynamical variables, and teleconnections influencing MCSs development are assessed for the Paute basin (PB) in the Ecuadorian Andes from 2000 to 2009. The seasonality of MCSs occurrence shows a bimodal pattern, with higher occurrence during March-April (MA) and October-November (ON), analogous to the regional rainfall seasonality. The diurnal cycle of MCSs shows a clear nocturnal occurrence, especially during the MA and ON periods. Interestingly, despite the higher occurrence of MCSs during the rainy seasons, the monthly size relative frequency remains fairly constant throughout the year. On the east of the PB, the persistent high convective available potential and low convective inhibition values from midday to nighttime are likely related to the nocturnal development of the MCSs. A significant positive correlation between the MCSs occurrence to the west of the PB and the Trans-Niño index was found, suggesting that ENSO is an important source of interannual variability of MCSs frequency with increasing development of MCSs during warm ENSO phases. On the east of the PB, the variability of MCSs is positively correlated to the tropical Atlantic sea surface temperature anomalies south of the equator, due to the variability of the Atlantic subtropical anticyclone, showing main departures from this relation when anomalous conditions occur in the tropical Pacific due to ENSO.
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Keywords: |
Andes |
Meteorology |
Trachte, K. (2018): Atmospheric Moisture Pathways to the Highlands of the Tropical Andes: Analyzing the Effects of Spectral Nudging on Different Driving Fields for Regional Climate Modeling. Atmosphere 9(11), 1-24.
Carrillo Rojas, G.; Silva, B.; Rollenbeck, R.; Celleri, R. & Bendix, J. (2018): The breathing of the Andean highlands: Net ecosystem exchange and evapotranspiration over the páramo of southern Ecuador. Agricultural and Forest Meteorology 265, 30-47.
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DOI: 10.1016/j.agrformet.2018.11.006
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Abstract:
Abstract:
Atmospheric carbon (CO2) exchange, evapotranspiration (ET) processes, and their interactions with climatic drivers across tropical alpine grasslands are poorly understood. This lack of understanding is particularly evident for the páramo, the highest vegetated frontier in the northern Andes, the main source of water for inter-Andean cities, and a large carbon storage area. Studies of CO2 and ET fluxes via the standard Eddy Covariance (EC) technique have never been applied to this region, limiting the understanding of diurnal / nocturnal exchanges and budget estimations. In this paper, we report the first EC analysis conducted on the Andean páramo (3765?m a.s.l.); this analysis measured CO2, ET, and micrometeorological variables over two years (2016–2018) to understand their interactions with climatic / biophysical controls. The páramo was found to be a source of CO2 and exhibited a net positive exchange (mean = +99?±?30 gC m?2 per year). The light-responses of net CO2 exchange and the primary productivity were correlated and model-parameterized. Evapotranspiration was 635?±?9?mm per year (51% of the annual rainfall total), and we obtained crop coefficients for the dominant vegetation (Tussock grass) based on reference-ET models FAO56 and ASCE-ERWI (0.90 and 0.78, respectively). We also compared our results to those from other high-altitude (alpine) and high-latitude grasslands (tundra). Finally, we demonstrate that our measurement period is representative of the páramo’s longer-term climate dynamics. Our investigation contributes to the body of knowledge on the land surface-atmosphere processes of the tropical Andes and supports decision-making about ecosystem services management and the preservation of this vulnerable biome.
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Keywords: |
Ecuador |
carbon |
Paramo |
Evapotranspiration |
Tropical Andes |
Eddy covariance |
Knüsting, J.; Brinkmann, M.C.; Silva, B.; Schorsch, M.; Bendix, J.; Beck, E. & Scheibe, R. (2018): Who will win where and why? An ecophysiological dissection of the competition between a tropical pasture grass and the invasive weed Bracken over an elevation range of 1000m in the tropical Andes. PlosOne 13, 1-24.
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DOI: 10.1371/journal.pone.0202255
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Abstract:
Abstract:
In tropical agriculture, the vigorously growing Bracken fern causes severe problems by
invading pastures and out-competing the common pasture grasses. Due to infestation by
that weed, pastures are abandoned after a few years, and as a fatal consequence, the biodi-
versity-rich tropical forest is progressively cleared for new grazing areas. Here we present a
broad physiological comparison of the two plant species that are the main competitors on
the pastures in the tropical Ecuadorian Andes, the planted forage grass Setaria sphacelata
and the weed Bracken (Pteridium arachnoideum).With increasing elevation, the competitive
power of Bracken increases as shown by satellite data of the study region. Using data
obtained from field measurements, the annual biomass production of both plant species, as
a measure of their competitive strength, was modeled over an elevational gradient from
1800 to 2800 m. The model shows that with increasing elevation, biomass production of the
two species shifts in favor of Bracken which, above 1800 m, is capable of outgrowing the
grass. In greenhouse experiments, the effects on plant growth of the presumed key vari-
ables of the elevational gradient, temperature and UV radiation, were separately analyzed.
Low temperature, as well as UV irradiation, inhibited carbon uptake of the C4-grass more
than that of the C3-plant Bracken. The less temperature-sensitive photosynthesis of
Bracken and its effective protection from UV radiation contribute to the success of the weed
on the highland pastures. In field samples of Bracken but not of Setaria, the content of flavo-
noids as UV-scavengers increased with the elevation. Combining modeling with measure-
ments in greenhouse and field allowed to explain the invasive growth of a common weed in
upland pastures. The performance of Setaria decreases with elevation due to suboptimal
photosynthesis at lower temperatures and the inability to adapt its cellular UV screen.
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Keywords: |
South Ecuador |
Bracken fern |
competition |
Gonzales-Jaramillo, V.; Fries, A.; Zeilinger, J.; Homeier, J.; Paladines, J. & Bendix, J. (2018): Estimation of Above Ground Biomass in a Tropical Mountain Forest in Southern Ecuador Using Airborne LiDAR Data. Remote Sensing 10, .
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DOI: 10.3390/rs10050660
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Abstract:
Abstract:
A reliable estimation of Above Ground Biomass (AGB) in Tropical Mountain Forest (TMF)
is still complicated, due to fast-changing climate and topographic conditions, which modifies the
forest structure within fine scales. The variations in vertical and horizontal forest structure are hardly
detectable by small field plots, especially in natural TMF due to the high tree diversity and the
inaccessibility of remote areas. Therefore, the present approach used remotely sensed data from a
Light Detection and Ranging (LiDAR) sensor in combination with field measurements to estimate
AGB accurately for a catchment in the Andes of south-eastern Ecuador. From the LiDAR data,
information about horizontal and vertical structure of the TMF could be derived and the vegetation at
tree level classified, differentiated between the prevailing forest types (ravine forest, ridge forest and
Elfin Forest). Furthermore, topographical variables (Topographic Position Index, TPI; Morphometric
Protection Index, MPI) were calculated by means of the high-resolution LiDAR data to analyse the
AGB distribution within the catchment. The field measurements included different tree parameters
of the species present in the plots, which were used to determine the local mean Wood Density
(WD) as well as the specific height-diameter relationship to calculate AGB, applying regional scale
modelling at tree level. The results confirmed that field plot measurements alone cannot capture
completely the forest structure in TMF but in combination with high resolution LiDAR data, applying
a classification at tree level, the AGB amount (Mg ha??1) and its distribution in the entire catchment
could be estimated adequately (model accuracy at tree level: R2 > 0.91). It was found that the AGB
distribution is strongly related to ridges and depressions (TPI) and to the protection of the site (MPI),
because high AGB was also detected at higher elevations (up to 196.6 Mg ha??1, above 2700 m), if the
site is situated in depressions (ravine forest) and protected by the surrounding terrain. In general,
highest AGB is stored in the protected ravine TMF parts, also at higher elevations, which could only
be detected by means of the remote sensed data in high resolution, because most of these areas are
inaccessible. Other vegetation units, present in the study catchment (pasture and subpáramo) do not
contain large AGB stocks, which underlines the importance of intact natural forest stands.
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Keywords: |
LiDAR |
AGB estimation |
Castro, L.M.; Härtl, F.; Ochoa Moreno, S.; Calvas, B.; Izquierdo Montoya, G.L. & Knoke, T. (2018): Integrated bio-economic models as tools to support land-use decision making: a review of potential and limitations. Journal of Bioeconomics online , online.
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DOI: 10.1007/s10818-018-9270-6
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Abstract:
Abstract:
Bio-economic modelling has become a useful tool for anticipating the
outcomes of policies and technologies before their implementation. Advances in mathematical
programming have made it possible to build more comprehensive models. In
an overview of recent studies about bio-economic models applied to land-use problems
in agriculture and forestry,we evaluated howaspects such as uncertainty,multiple
objective functions, system dynamics and time have been incorporated into models.
We found that single objective models were more frequently applied at the farm level,
while multiple objective modelling has been applied to meet concerns at the landscape
level. Among the objectives, social aspects are seldom represented in allmodels, when
being compared to economic and environmental aspects. The integration of uncertainty
is occasionally a topic, while stochastic approaches are more frequently applied than
non-stochastic robust methods. Mostmultiple-objectivemodels do not integrate uncertainty
or sequential decision making. Static approaches continue to be more recurrent
than truly dynamic models. Even though integrating multiple aspects may enhance
our understanding of a system; it involves a tradeoff between complexity and robustness
of the results obtained. Land-use models have to address this balance between
complexity and robustness in order to evolve towards robust multiple-objective spatial
optimization as a prerequisite to achieve sustainability goals.
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Keywords: |
Uncertainty analysis |
land use modeling |
Mosquera, G.; Brum, M.; Barros, F.d.V.; Vieira Pompeu, P.; Rodas, M.; Lazo, P.; Müller, C.S.; Mulligan, M.; Asbjornses, H.; Moore, G.W. & Oliveira, R.S. (2017): Ecohydrological drivers of Neotropical vegetation in montane ecosystems. Ecohydrology n/a, e1932.
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DOI: 10.1002/eco.1932
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Abstract:
Abstract:
Montane ecosystems are known for their high numbers of endemic species, unique climate conditions, and wide variety of ecosystem services such as water supply and carbon storage. Although many ecohydrological and climatic studies of montane environments have been carried out in temperate and boreal regions, few have been done in Neotropical regions. Hence, the objective of this review is to synthesize the existing literature on the main factors (biotic and abiotic) that influence vegetation distribution, functional traits, and ecohydrological processes and feedbacks in tropical montane ecosystems and to identify key knowledge gaps. Most of the literature used includes work conducted in Neotropical montane rainforests, cloud forests, and grass/scrublands (e.g., páramos, punas, and campos de altitude/rupestres). Fog is a major cli- matic attribute in tropical montane habitats. We found that fog regimes (frequency and intensity of fog events) influence both water inputs (i.e., canopy interception and foliar water uptake) and outputs (evapotranspiration) and represent an important driver of local species composition, dominance of plant functional types, and ecological functioning. The stability and conservation of tropical montane ecosystems depends on such ecohydrological fluxes, which are sensitive to increases in air temperature and changing precipitation and fog regimes. Furthermore, to better inform effective conservation and restoration strategies, more work is needed to elucidate how key ecohydrological processes are affected by land use conversion to agriculture and pasture lands, as human activities influence the water budgets in Neotropical montane watersheds not only at regional?scales but also globally.
KEYWORDS
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Keywords: |
ecosystem services |
grassland |
fog |
montane rain forest |
water and carbon budgets |
Quitian, M.; Santillan, V.; Espinosa, C.I.; Homeier, J.; Boehning-Gaese, K.; Schleuning, M. & Neuschulz, E. (2017): Elevation-dependent effects of forest fragmentation on plant–bird interaction networks in the tropical Andes. Ecography 40, 1-10.
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DOI: 10.1111/ecog.03247
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Abstract:
Abstract:
Tropical forests harbor diverse ecological communities of plants and animals that are organized in complex interaction networks. The diversity and structure of plant–animal interaction networks may change along elevational gradients and in response to human-induced habitat fragmentation. While previous studies have analyzed the effects of elevation and forest fragmentation on species interaction networks in isolation, to our knowledge no study has investigated whether the effects of forest fragmentation on species interactions may differ along elevational gradients. In this study, we analyzed main and interaction effects of elevation and forest fragmentation on plant–frugivore interaction networks at plant and bird species level. Over a period spanning two years, we recorded plant–frugivore interactions at three elevations (1000, 2000 and 3000 m a.s.l.) and in two habitat types (continuous and fragmented forest) in tropical montane forests in southern Ecuador. We found a consistent effect of elevation on the structure of plant–frugivore networks. We observed a decrease in the number of effective bird partners of plants and, thus, a decline in the redundancy of bird species with increasing elevation. Furthermore, bird specialization on specific plant partners increased towards high elevations. Fragmentation had a relatively weak effect on the interaction networks for both plant and bird species, but resulted in a significant increase in bird specialization in fragmented forests at high elevations. Our results indicate that forest fragmentation may have stronger effects on plant–frugivore interaction networks at high compared to low elevations because bird species richness declined more steeply towards high elevations than plant species richness. We conclude that conservation efforts should prioritize the maintenance of consumer diversity, for instance by maintaining stretches of continuous forest. This applies in particular to species-poor communities, such as those at high elevations, as the ecological processes in these communities seem most sensitive towards forest fragmentation.
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Keywords: |
elevational gradient |
mutualistic interactions |
specialization |
Manchego, C.; Hildebrandt, P.; Cueva Ortiz, J.L.; Espinosa, C.; Stimm, B. & Günter, S. (2017): Climate change versus deforestation: Implications for tree species distribution in the dry forests of southern Ecuador. PLOS ONE 12(12), e0190092.
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DOI: 10.1371/journal.pone.0190092
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Abstract:
Abstract:
Seasonally dry forests in the neotropics are heavily threatened by a combination of human disturbances and climate change; however, the severity of these threats is seldom contrasted. This study aims to quantify and compare the effects of deforestation and climate change on the natural spatial ranges of 17 characteristic tree species of southern Ecuador dry deciduous forests, which are heavily fragmented and support high levels of endemism as part of the Tumbesian ecoregion. We used 660 plant records to generate species distribution models and land-cover data to project species ranges for two time frames: a simulated deforestation scenario from 2008 to 2014 with native forest to anthropogenic land-use conversion, and an extreme climate change scenario (CCSM4.0, RCP 8.5) for 2050, which assumed zero change from human activities. To assess both potential threats, we compared the estimated annual rates of species loss (i.e., range shifts) affecting each species. Deforestation loss for all species averaged approximately 71 km2/year, while potential climate-attributed loss was almost 21 km2/year. Moreover, annual area loss rates due to deforestation were significantly higher than those attributed to climate-change (P < 0.01). However, projections into the future scenario show evidence of diverging displacement patterns, indicating the potential formation of novel ecosystems, which is consistent with other species assemblage predictions as result of climate change. Furthermore, we provide recommendations for management and conservation, prioritizing the most threatened species such as Albizia multiflora, Ceiba trichistandra, and Cochlospermum vitifolium.
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Keywords: |
Southern Ecuador |
deforestation |
climate change scenario |
tree species |
Seasonally dry tropical forest |
species distribution modelling |
Guio Blanco, C.M.; Brito Gómez, V.M.; Crespo, P. & Ließ, M. (2018): Spatial prediction of soil water retention in a Páramo landscape: Methodological insight into machine learning using random forest. Geoderma 316, 100-114.
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DOI: 10.1016/j.geoderma.2017.12.002
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Abstract:
Abstract:
Soils of Páramo ecosystems regulate the water supply to many Andean populations. In spite of being a necessary input to distributed hydrological models, regionalized soil water retention data from these areas are currently not available. The investigated catchment of the Quinuas River has a size of about 90 km2 and comprises parts of the Cajas National Park in southern Ecuador. It is dominated by soils with high organic carbon contents, which display characteristics of volcanic influence. Besides providing spatial predictions of soil water retention at the catchment scale, the study presents a detailed methodological insight to model setup and validation of the underlying machine learning approach with random forest. The developed models performed well predicting volumetric water contents between 0.55 and 0.9 cm3 cm? 3. Among the predictors derived from a digital elevation model and a Landsat image, altitude and several vegetation indices provided the most information content. The regionalized maps show particularly low water retention values in the lower Quinuas valley, which go along with high prediction uncertainties. Due to the small size of the dataset, mineral soils could not be separated from organic soils, leading to a high prediction uncertainty in the lower part of the valley, where the soils are influenced by anthropogenic land use.
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Keywords: |
Páramo |
random forest |
water retention |
validation |
parameter tuning |
Quichimbo Miguitama, P.G.; Jiménez, L.; Veintimilla, D.; Tischer, A.; Günter, S.; Mosandl, R. & Hamer, U. (2017): Forest Site Classification in the Southern Andean Region of Ecuador: A Case Study of Pine Plantations to Collect a Base of Soil Attributes. Forests 473(8), 1-22.
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DOI: 10.3390/f8120473
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Abstract:
Abstract:
Forest site classification adapted to the respective site conditions is one prerequisite for
sustainable silviculture. This work aims to initiate the forest site classification for pine plantations
in the southern Andean region of Ecuador. Forest productivity, estimated by the dominant height
of 20-year-old trees (DH20), was related to data from climate, topography, and soil using 23 plots
installed in pine plantations in the province of Loja. Forest site productivity was classified as:
low (class C: 13.4 m), middle (class B: 16.6 m), and high (Class A: 22.3 m). Strong determinants
to differentiate the forest site classes were: the short to medium term available Ca and K stocks
(organic layer + mineral soil standardized to a depth of 60 cm), soil acidity, the C:N ratio, clay and
sand content, forest floor thickness, altitude, and slope. The lowest forest productivity (Class C)
is mainly associated with the lowest short to medium term available K and Ca stocks. Whereas,
in site classes with the highest forest productivity, pines could benefit from a more active microbial
community releasing N and P, since the soil pH was about 1 unit less acidic. This is supported by the
lowest forest floor thickness and the narrowest C:N ratio.
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Keywords: |
forest |
soil nutrients |
soil |
pine forest |
Pinus patula |
Forest plantation |
forest productivity |
Wright, C.; Kawaga-Viviani, A.; Gerlein-Safdi, C.; Mosquera, G.; Poca, M.; Tseng, H. & Chun, K.P. (2017): Advancing ecohydrology in the changing tropics: Perspectives from early career scientists. Ecohydrology na, e1918.
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DOI: 10.1002/eco.1918
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Abstract:
Abstract:
Tropical ecosystems offer a unique setting for understanding ecohydrological processes, but to date, such investigations have been limited. The purpose of this paper is to highlight the impor- tance of studying these processes—specifically, how they are being affected by the transforma- tive changes taking place in the tropics—and to offer an agenda for future research. At present, the ongoing loss of native ecosystems is largely due to agricultural expansion, but parallel pro- cesses of afforestation are also taking place, leading to shifts in ecohydrological fluxes. Similarly, shifts in water availability due to climate change will affect both water and carbon fluxes in trop- ical ecosystems. A number of methods exist that can help us better understand how changes in land use and climate affect ecohydrological processes; these include stable isotopes, remote sens- ing, and process?based models. Still, our knowledge of the underlying physical mechanisms, espe- cially those that determine the effects of scale on ecosystem processes, remains incomplete.We assert that development of a knowledge base concerning the effects of transformative change on ecological, hydrological, and biogeochemical processes at different spatio?temporal scales is an urgent need for tropical regions and should serve as a compass for emerging ecohydrologists. To reach this goal, we advocate a research agenda that expands the number and diversity of eco- systems targeted for ecohydrological investigations and connects researchers across the tropics. We believe that the use of big data and open source software—already an important integrative tool/skill for the young ecohydrologist—will be key in expanding research capabilities.
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Keywords: |
remote sensing |
climate change |
big data |
land use/land cover |
modelling |
stable isotopes |
tropical ecosystems |
Cárate Tandalla, D.; Camenzind, T.; Leuschner, C. & Homeier, J. (2018): Contrasting species responses to continued nitrogen and phosphorus addition in tropical montane forest tree seedlings. Biotropica 50(2), 234-245.
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DOI: 10.1111/btp.12518
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Abstract:
Abstract:
Global changes in nutrient deposition rates are likely to have profound effects on plant communities, particularly in the nutrient-limited systems of the tropics. We studied the effects of increased nutrient availability on the seedlings of six tree species in montane forests of southern Ecuador in situ. After five years of continued N, P, or N+P addition, naturally grown seedlings of each of the two most common
species at each elevation (1000, 2000, and 3000 m asl) were harvested for analyses of leaf morphology, nutrient content, herbivory, and tissue biomass allocation. Most species showed increased foliar N and P concentrations after addition of each respective element. Leaf tissue N:P ratios of >20 in the control plants of all species suggest that P is more growth-limiting in these forests than N. Leaf
morphological responses to nutrient addition were species and nutrient specific, with some species (Hedyosmum purparescens, Graffenrieda emarginata) exhibiting increased specific leaf area (SLA), and others (Graffenrieda harlingii) increased leaf area ratios (LAR). Pouteria torta (1000 m) had lower SLA and LAR after P addition. Increased herbivory was only evident in G. emarginata (after N and N+P addition).
Only the species from 3000 m asl modified biomass allocation after nutrient addition. In general, N and N+P addition more strongly affected the species studied at the upper elevations, whereas P addition had a similar range of effects on the species at all elevations. We conclude that the responses of the studied tropical montane forest tree seedlings to chronic N and P addition are highly species-specific and that successful adaptation to increased nutrient availability will depend on species-specific morphological and physiological plasticity.
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Keywords: |
seedlings |
NUMEX |
functional traits |
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 |
Báez, S. & Homeier, J. (2018): Functional traits determine tree growth and ecosystem productivity of a tropical montane forest: Insights from a long-term nutrient manipulation experiment. Global Change Biology 24(1), 399-409.
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DOI: 10.1111/gcb.13905
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Abstract:
Abstract:
Trait response-effects are critical to forecast community structure and biomass production in highly diverse tropical forests. Ecological theory and few observation studies indicate that trees with acquisitive functional traits would respond more strongly to higher resource availability than those with conservative traits. We assessed how long-term tree growth in experimental nutrient addition plots (N, P and N+P) varied as a function of morphological traits, tree size and species identity. We also evaluated how trait-based responses affected stand scale biomass production considering the community structure. We found that tree growth depended on interactions between functional traits and the type or combination of nutrients added. Common species with acquisitive functional traits responded more strongly to nutrient addition, mainly to N+P. Phosphorous enhanced the growth rates of species with acquisitive and conservative traits, had mostly positive effects on common species and neutral or negative effects in rare species. Moreover, trees receiving N+P grew faster irrespective of their initial size relative to control or to other treatment plots. Finally, species responses were highly idiosyncratic suggesting that community processes including competition and niche dimensionality may be altered under increased resource availability. We found no statistically significant effects of nutrient additions on aboveground biomass productivity because acquisitive species had a limited potential to increase their biomass, possibly due to their generally lower wood density. In contrast, P addition increased the growth rates of species characterized by more conservative resource strategies (with higher wood density) that were poorly represented in the plant community. We provide the first long-term experimental evidence that trait-based responses, community structure, and community processes modulate the effects of increased nutrient availability on biomass productivity in a tropical forest.
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Keywords: |
NUMEX |
functional traits |
experimental nutrient addition |
Correa, A.; Windhorst, D.; Tetzlaff, D.; Crespo, P.; Celleri, R.; Feyen, J. & Breuer, L. (2017): Temporal dynamics in dominant runoff sources and flow paths in the Andean Páramo. Water Resources Research 53(8), 5998-6017.
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DOI: 10.1002/2016WR020187
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Abstract:
Abstract:
The relative importance of catchment's water provenance and flow paths varies in space and time, complicating the conceptualization of the rainfall-runoff responses. We assessed the temporal dynamics in source areas, flow paths, and age by End Member Mixing Analysis (EMMA), hydrograph separation, and Inverse Transit Time Proxies (ITTPs) estimation within a headwater catchment in the Ecuadorian Andes. Twenty-two solutes, stable isotopes, pH, and electrical conductivity from a stream and 12 potential sources were analyzed. Four end-members were required to satisfactorily represent the hydrological system, i.e., rainfall, spring water, and water from the bottom layers of Histosols and Andosols. Water from Histosols in and near the riparian zone was the highest source contributor to runoff throughout the year (39% for the drier season, 45% for the wetter season), highlighting the importance of the water that is stored in the riparian zone. Spring water contributions to streamflow tripled during the drier season, as evidenced by geochemical signatures that are consistent with deeper flow paths rather than shallow interflow through Andosols. Rainfall exhibited low seasonal variation in this contribution. Hydrograph separation revealed that 94% and 84% is preevent water in the drier and wetter seasons, respectively. From low-flow to high-flow conditions, all the sources increased their contribution except spring water. The relative age of stream water decreased during wetter periods, when the contributing area of the riparian zone expands. The multimethod and multitracer approach enabled to closely study the interchanging importance of flow processes and water source dynamics from an interannual perspective.
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Keywords: |
hydrochemistry |
Paramo |
hydrological processes |
catchment flow dynamics |
Oñate-Valdivieso, F.; Fries, A.; Mendoza, K.; Gonzales-Jaramillo, V.; Pucha Cofrep, F.; Rollenbeck, R. & Bendix, J. (2017): Temporal and spatial analysis of precipitation patterns in an Andean region of southern Ecuador using LAWR weather radar. Meteorology and Atmospheric Physics 129(295), 1-12.
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DOI: 10.1007/s00703-017-0535-8
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Abstract:
Abstract:
This paper focuses on the analysis of precipitation patterns, using a Local Area Weather Radar to collect information about the precipitation distribution in an Andean region of southern Ecuador (cities of Loja, Zamora and Catamayo). 54 representative events were selected to develop daily precipitation maps and to obtain their relevant characteristics, which were related to the topography and the season. The results showed that a strong correlation between the areas covered by precipitation (RA coefficient) and the season exists. In general, humid air masses come from the east (Amazon Basin), but during the main rainy season (December to April), humidity also frequently enters the study region from the west (Pacific Ocean). The rainy season is characterized by convective precipitation, associated with higher evaporation rates during austral summer. The relatively dry season is formed between May and November, but considerable precipitation amounts are registered, too, due to advective moisture transport from the Amazon Basin, a result of the predominant tropical easterlies carrying the humidity up the eastern escarpment of the Andes, generally following the natural course of the drainage systems.
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Keywords: |
Ecuador |
precipitation |
radar |
Bendix, J.; Fries, A.; Zárate, J.; Trachte, K.; Rollenbeck, R.; Pucha Cofrep, F.; Paladines, R.; Palacios, I.; Orellana Alvear, J.; Oñate-Valdivieso, F.; Naranjo, C.; Mendoza, L.; Mejia, D.; Guallpa, M.; Gordillo, F.; Gonzales-Jaramillo, V.; Dobbermann, M.; Celleri, R.; Carrillo, C.; Araque, A. & Achilles, S. (2017): Radarnet Sur – first weather radar network in tropical high mountains. Bulletin of the American Meteorological Society 98(6), 1235-1254.
Palomeque, X.; Maza, A.; Iñanagua, J.P.; Günter, S.; Hildebrandt, P.; Weber, M. & Stimm, B. (2017): Intraspecific Variability in Seed Quality of Native Tree Species in Mountain Forests in Southern Ecuador: Implications for Forest Restoration. Revista de Ciencias Ambientales (Tropical Journal of Environmental Sciences) 51(2), 52-72.
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DOI: 10.15359/rca.51-2.3
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Abstract:
Abstract:
Uno de los aspectos importantes a considerarse en la producción eficiente de plántulas con fines de restauración es la calidad de semillas y su variabilidad. El objetivo de este estudio fue evaluar los parámetros de semillas de acuerdo con las reglas del “International Seed Testing Association” entre diferentes árboles madre o individuos de siete especies nativas (Cedrela montana, Morella pubescens, Inga acreana, Tabebuia chrysantha, Ocotea heterochroma, Oreocallis grandiflora y Myrcianthes rhopaloides) en dos bosques de montaña del sur del Ecuador. Estas especies fueron seleccionadas por la importancia ecológica, socioeconómica, y su gran potencial para la restauración. De un total de 35 árboles madre de todas las especies, se colectaron las semillas en sus respectivos periodos de fructificación, y en el laboratorio fueron analizados los siguientes parámetros: pureza, peso, contenido de humedad y germinación; adicionalmente se determinó el coeficiente de velocidad de germinación. Los resultados mostraron una similitud intraespecífica en cada especie para la mayoría de los parámetros; no obstante, el peso presentó alta variabilidad intraespecífica para todas las especies. El parámetro germinación obtuvo diferencias entre individuos para C. montana, T. chrysantha, O. heterochroma y M. rhopaloides. En cuanto a la velocidad de germinación, individuos de especies como O. grandiflora e I. acreana mostraron un alto coeficiente en contraste a los individuos de O. heterochroma y M. pubescens. La información generada en este estudio podría ser el primer paso en la formulación de pautas para la producción masiva de plántulas de especies nativas con fines de restauración.
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Keywords: |
seedlings |
Cedrela montana |
Tabebuia chrysantha |
native species |
tree seeds |
restoration |
germination |
seed quality |
Morella pubescens |
Inga acreana |
Ocotea heterochroma |
Oreocallis grandiflora |
Palomeque, X.; Günter, S.; Siddons, D.; Hildebrandt, P.; Stimm, B.; Aguirre, N.; Arias, R. & Weber, M. (2017): Natural or assisted succession as approach of forest recovery on abandoned lands with different land use history in the Andes of Southern Ecuador. New Forests 1(1), 1-10.
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DOI: 10.1007/s11056-017-9590-8
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Abstract:
Abstract:
Forest recovery on disturbed areas is of special significance in the Ecuadorian Andes, where deforestation is a serious problem. Natural diachronic succession was evaluated on three large plots or sites, differing in their land use and vegetation composition, one is dominated by grass species on an abandoned pasture (Pasture site), the other two are post-fire vegetation dominated by bracken (Bracken site) and various shrubs (Shrub site). Additionally, we assessed the effectiveness of manual removal of competitive herbaceous species to accelerate forest recovery. Monitoring was done in 2003, 2005 and 2007 on 48 subplots of 116 m2 each recording species richness and woody-species density. Results showed that the Pasture site demonstrated a competitive effect of exotic grasses on woody species recruitment with much lower species recruitment and density, suggesting serious inhibition of natural forest regeneration and an unclear successional trajectory. The Bracken and Shrub sites became significantly similar floristically and there is evidence for a marked facilitation of woody plant recruitment correlated with light availability on the ground. Both sites showed characteristics of classic succession, with Shrub showing a higher species richness and density while late-successional species are poorly represented on the Bracken site. However, NMDS ordination using species density showed that the two trajectories may not be converging towards a common ‘‘final state’’. Manual weeding was ineffective for accelerating forest recovery. These results suggest that the main limiting factor for the recruitment of woody species on the Pasture site is strong grass competition and must be addressed before seed availability, while seed availability seems to be theconstraining factor for Bracken and Shrub site development, thus direct seeding or planting may be effective in accelerating forest recovery.
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Keywords: |
succession |
abandoned pasture |
bracken fern |
restoration |