Publications
Found 850 publication(s)
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DFG PAK 823-825 (2015): Tabebuia Bulletins, Issue 3. Laboratory for Climatology and Remote Sensing (LCRS), University of Marburg, Marburg, Germany.
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DOI: 10.5678/lcrs/pak823-825.cit.1399
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After the coordinators’ updating of the state of research and introducing the new name of this publication, they summarize the important elements of the program for knowledge transfer to stakeholders. The local advisory board informs about a landslide which hit research grounds. Science papers in this issue
• compare tropical montane elevation transects in Ecuador and Peru
• analyze the relationship of decomposer communities and leaf litter types
• demonstrate how fertilization influences the amount of bio-available phosphorus
• reveal that nutrient availability stimulates mineralization of dissolved organic matter
• show that image textures can supersede functional biodiversity analysis
• provide insights into the transformation from abandoned sites to valuable pasture land.
A report presents the completed construction of the last radar of the RadarNet Sur that is situated on a mountain peak and is the highest operating weather radar worldwide. The Data Warehouse manager describes the results of a survey taken to increase data quality and usability. And two workshops transferred gained knowledge on how to perform terrain analyses with the geographical information system SAGA.
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Keywords: |
Ecuador |
Newsletter |
Biodiversity |
DFG PAK 823-825 |
Tabebuia Bulletins |
Spannl, S.; Günter, S.; Peters, T.; Volland, F. & Bräuning, A. (2012): Which factors control tree growth in a tropical mountain forest? The case of Cedrela montana in Southern Ecuador. TRACE - Tree Rings in Archaeology, Climatology and Ecology 10, 99-105.
Peters, T.; Drobnik, T.; Meyer, H.; Rankl, M.; Richter, M.; Rollenbeck, R.; Thies, B. & Bendix, J. (2014): Environmental Changes Affecting the Andes of Ecuador. In: Bendix, J., Beck, E., Bräuning, A., Makeschin, F., Mosandl, R., Scheu, S., Wilcke, W. (eds.): Ecosystem Services, Biodiversity and Environmental Change in a Tropical Mountain Ecosystem of South ( ), Springer.
Spannl, S.; Ganzhi, O.; Peters, T. & Bräuning, A. (2013): Tree growth under climatic and trophic forcing - A nutrient manipulation experiment in Southern Ecuador. TRACE - Tree Rings in Archaeology, Climatology and Ecology 11, 10-14.
Peters, T. (2014): Water Balance in Tropical Regions. In: Michael Koehl, Laszlo Pancel (eds.): Tropical Forestry Handbook ( ), Springer, Heidelberg.
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DOI: 10.1007/SpringerReference_384452
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Within this chapter relative air humidity, evaporation, transpiration, evapotranspiration, hydrologic cycle and water balance are discussed for the Tropics. In general, atmospheric water is of high climatological importance due to its capacity to control precipitation as well as to its influence on absorption and reflection of solar and terrestrial radiation. When water changes its state of aggregation, energy is either produced or consumed. This is crucial for the tropical atmosphere where the condensation of large amounts of water vapor leads to the release of latent heat energy. The global hydrosphere consists of a couple of different water reservoirs which are connected by water fluxes in various phases. From these
reservoirs, water moves in a great series of continuous interchanges of both physical state and geographical position, known as the hydrologic cycle. Evapotranspiration is one of the most important factors for the water budget and physical processes in the tropics. It specifies the total flow of water into the atmosphere which is composed of two processes: evaporation and transpiration.
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Climate - Evaporation - Evapotranspiration - Hydrologic cycle - Relative air humidity - Transpiratio |
Peters, T. & Richter, M. (2014): The Atmospheric Circulation. In: Michael Koehl, Laszlo Pancel (eds.): Tropical Forestry Handbook ( ), Springer, Heidelberg.
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DOI: 10.1007/SpringerReference_384448
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Within this chapter the Hadley Circulation, the Monsoon System, Easterly Waves, Tropical Cyclones and the Walker Circulation are discussed. While the Hadley Circulation and the Monsoon System explain different air flow systems in a mainly meridional sense, a secondary system of latitudinal wind flow is governed by the Walker circulation which is decisive for the formation of La Niña and El Niño events. Apart from the long-term seasonal and nonseasonal variations of the tropical atmosphere, the climate of the Tropics is also affected by more frequent tropical weather disturbances. One of them are large-scale planetary waves which produce greater amounts of rainfall in many maritime tropical regions. These disturbance lines sprawl in a meridional direction from east to west and are called easterly waves.
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Easterly waves - Hadley circulation - Monsoon system - Tradewind system - Tropical cyclones - Walker |
Richter, M. (2014): Temperatures in the Tropics. In: Michael Koehl, Laszlo Pancel (eds.): Tropical Forestry Handbook ( ), Springer, Heidelberg.
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DOI: 10.1007/SpringerReference_384450
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A main character of the entire tropics are the very low longitudinal gradients of air temperature of only 1 °C/1,000 km. In Fig. 1 (above) this is indicated by the broad reddish sector around the equator between 30°N and S and even beyond. A closer look at the upper image reveals darker patterns and hence the globally "hottest ecozone" over the Sahel and southern Sahara to the SE of the Arabian Peninsula. By far most of this section is part of the outer tropics. This "heat crest" north of the equator represents a thermal asymmetry and is linked to the large dimension of landmass in the northern half of Africa. Vertical termperature gradients in tropical mountains as well as changing meridional gradients of temperature amplitudes between the outer and inner tropics are presented by Figs. 2 and 3, resp. Diurnal an seasonal
cycles are illustrated by thermoisopleths for different altitudes and under arid up to perhumid conditons (Figs. 4 and 5), which are also exampled for soil and surface temperatures (Fig. 6). Impacts of cold as well as of dry air intrusions (Figs. 7-9) are related to plant reactions and phenological aspects (Fig. 10).
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Air intrusions and surges - Continentality - Phenology - Soil temperatures - Temperature gradients - |
Peters, T. (2014): Radiation and Heat in the Tropics. In: Michael Koehl, Laszlo Pancel (eds.): Tropical Forestry Handbook ( ), Springer, Heidelberg.
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DOI: 10.1007/SpringerReference_384449
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Within this chapter different aspects of radiation and heat are discussed for the tropics. On a global scale the amount of annual solar radiation reaching the Earth's surface is determined by atmospheric and astronomical factors and the average energy budget of the Earth could be explained by the global radiation budget. Within the tropics the net radiation varies clearly across the different climatic regions. In the humid tropics the amount of net radiation shows an almost uniform annual pattern with two maxima per annum. In contrast to this, the horizontal course of the isopleths in a radiation isopleths diagram for the marginal tropics still indicates a marked diurnal cycle. At the Earth's surface, the total incoming
radiation is transformed into different heat fluxes which are either directed towards the ground or to the atmosphere. In the tropical rainforests, only 10 % of the incoming radiation reaches the ground, and only a weak flow of sensible and latent heat exists from the forest canopy towards the forest ground and vice versa.
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Tropics - Radiation and Heat - Global Radiation Budget - Heat Budget - Sensible and Latent Heat |
Richter, M. (2014): Precipitation in the Tropics. In: Michael Koehl, Laszlo Pancel (eds.): Tropical Forestry Handbook ( ), Springer, Heidelberg.
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DOI: 10.1007/SpringerReference_384451
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Large scale moisture patterns subdevide the year-round tropics from perarid up to perhumid subzones, which are combined with different degrees of cloudiness (Fig. 1) with convective heap clouds being of most importance (Figs. 2, 3, 4 and 5). A rather clear seasonal distribution of rainfall frequency and intensity (Fig. 7) governs the rythm of plant growth. Areas of highest precipitation amounts on the globe are concentrated on the inner parts of the tropics (Fig. 8), where thunderstorms are a typical feature of weather occurence. Long enduring droughts in wet as well as extraordinary rainfall intensities in arid regions are concentrated on distinct areas (Figs. 11 and 12). Most of the tropical high mounts show
obvious "bulges" of enhanced rainfall rates at mid-elevations (Fig. 15).
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Keywords: |
Clouds - Fog - Rainfall amount - Frequency and intensity - Spatial - Altitudinal and seasonal rainfa |
Richter, M. (2014): Microclimate in the Tropics. In: Michael Koehl, Laszlo Pancel (eds.): Tropical Forestry Handbook ( ), Springer, Heidelberg.
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DOI: 10.1007/SpringerReference_384453
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Microclimatic differences between site conditions of forest ecosystems and farmlands are accented to clarify the significant importance of tree canopies for ecosystem services and agroforestry. An analyis of the climate within a tropical rainforest and its impact on epiphytic structure is given by Fig. 2. After forest conversion into farmland, radiation turnovers and energy flows as well as precipitation rates change dramatically (Figs. 3 and 4). Furthermore, clear-cuts of tropical forests enhance in destructive erosion processes during tropical downpours (Figs. 5, 6, and 8), which can reach impressive amounts during hurricane events (Fig. 7).
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Buffer effects - Energy balance - Forest climate - Land conversion - Radiation turnover - Regional c |
Peters, T. (2014): Design of Data Collection Related to the Climate in the Tropics. In: Michael Koehl, Laszlo Pancel (eds.): Tropical Forestry Handbook ( ), Springer, Heidelberg.
Peters, T. (2014): Climatic Types of Water Balances in the Tropics. In: Michael Koehl, Laszlo Pancel (eds.): Tropical Forestry Handbook ( ), Springer, Heidelberg.
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DOI: 10.1007/SpringerReference_384414
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One of the most important climate criteria of the tropics is the absence of thermic seasons. Thus, hygric seasons become more relevant for ecosystem functioning and are of special importance for plant growth. Within this chapter different climate types of the tropics are discussed on the basis of their annual water budget. The humid climate type appears across the rain equator within or close to the ITCZ. It is distinguished by a clear water surplus and all months show a positive water balance in the long-term mean. The semi-humid climate type prevails at a certain distance from the Equator and the ITCZ. It is characterized by a distinct rainfall seasonality and the occurrence of more than 3 -4 arid months. In terms of the arid climate type the arid period is in general longer than the humid period and precipitation amounts decrease almost towards zero within the desert areas.
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Tropics - Climatic Types - Hygric seasons - Humid Climate Type - Semi-Humid Climate Type - Arid Clim |
Peters, T. (2014): Climate Change in the Tropics. In: Michael Koehl, Laszlo Pancel (eds.): Tropical Forestry Handbook ( ), Springer, Heidelberg.
Richter, M. (2014): Climate Aspects of the Tropics. In: Michael Koehl, Laszlo Pancel (eds.): Tropical Forestry Handbook ( ), Springer, Heidelberg.
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DOI: 10.1007/SpringerReference_384446
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Unlike the high latitudes and most of the mid-latitudes, the tropical ecozone benefits from a constant radiation surplus. In daytime, the sunrays descend at a steep angle up to 90° at noon between the tropics twice per year. Hence,long-term shaded slopes in mountain landscapes do not exist. Lengths of day and night stay almost the same at the equator (approx. 12 h.), while at the Tropics of Cancer and Capricorn, minimum and maximum day lengths vary within a time span from 10.5 to 13.5 h. As a result marked thermal seasons are absent in the tropical climates.
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"Warm" and "Cold" tropics - "Humid" and "Arid" tropics - Diurnal Temperature Amplitude - ITCZ |
Richter, M. (2014): Classification of Climates in the Tropics. In: Michael Koehl, Laszlo Pancel (eds.): Tropical Forestry Handbook ( 2), Springer, Heidelberg.
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DOI: 10.1007/SpringerReference_384447
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Differences in the thermic and hygric seasonalities cause decisive distinctions between extratropical and tropical plant growth features. Around the tropics of Capricorn and Cancer noticeable seasonal cycles of temperature still occur, which are of minor importance within the megatherm inner tropics. Two classification systems offer a subdivision of the tropical climates. Compared to the frequently used Koeppen-approach, that one of Lauer is prefered here due to its clearly defined hygrothermal regimes. Altitudinal climate belts in the tropics are presented by a general scheme, while climate and
vegetation profiles reflect a realistic situation alongside the neotropical Cordilleras.
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Classification of Köppen and of Lauer - Ecozones - Altitudinal belts |
Wagemann, J.; Thies, B.; Rollenbeck, R.; Peters, T. & Bendix, J. (2015): Regionalization of wind-speed data to analyse tree-line wind conditions in the eastern Andes of southern Ecuador. Erdkunde 69, 3-19.
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DOI: 10.3112/erdkunde.2015.01.01
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This paper presents a method to extrapolate wind-speed data and to calculate wind-speed and dynamic pressure maps for the complex topography of a mountain rainforest area in the tropical Andes of southeastern Ecuador. The spatial differentiation of dynamic wind pressure in this area is claimed to be a major determinant of the altitude of the tree-line ecotone and to affect the tree line’s physiognomy. The paper presents a hybrid method encompassing statistical data analysis using the Weibull distribution and a digital terrain analysis, taking topographical shelter effects into account. The method is used to derive mean and maximum wind-speed and dynamic pressure maps to reveal whether the tree-line ecotone is influenced by direct wind effects. On average, the tree-line ecotone on the eastern slopes shows a clear average depression of ~50 m. These slopes are affected by higher dynamic wind stress, so have a more disturbed canopy. These altered vegetation structures may be caused mainly by direct wind effects and to a smaller extent by indirect effects, such as high humidity.
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wind speed |
regionalization |
Tischer, A.; Werisch, M.; Döbbelin, F.; Camenzind, T.; Rillig, M.C.; Potthast, K. & Hamer, U. (2015): Above- and belowground linkages of a nitrogen and phosphorus co-limited tropical mountain pasture system – responses to nutrient enrichment. Plant and Soil -(-), 1-20.
Curatola Fernández, G.F.; Obermeier, W.A.; Gerique, A.; López Sandoval, M.F.; Lehnert, L.W.; Thies, B. & Bendix, J. (2015): Land Cover Change in the Andes of Southern Ecuador - Patterns and Drivers. Remote Sensing 7(3), 2509-2542.
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DOI: 10.3390/rs70302509
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In the megadiverse tropical mountain forest in the Andes of southern Ecuador, a global biodiversity hotspot, the use of fire to clear land for cattle ranching is leading to the invasion of an aggressive weed, the bracken fern, which is threatening diversity and the provisioning of ecosystem services. To find sustainable land use options adapted to the local situation, a profound knowledge of the long-term spatiotemporal patterns of land cover change and its drivers is necessary, but hitherto lacking. The complex topography and the high cloud frequency make the use of remote sensing in this area a challenge. To deal with these conditions, we pursued specific pre-processing steps before classifying five Landsat scenes from 1975 to 2001. Then, we quantified land cover changes and habitat fragmentation, and we investigated landscape changes in relation to key spatial elements (altitude, slope, and distance from roads). Good classification results were obtained with overall accuracies ranging from 94.5% to 98.5% and Kappa statistics between 0.75 and 0.98. Forest was strongly fragmented due to the rapid expansion of the arable frontier and the even more rapid invasion by bracken. Unexpectedly, more bracken-infested areas were converted to pastures than vice versa, a practice that could alleviate pressure on forests if promoted. Road proximity was the most important spatial element determining forest loss, while for bracken the altitudinal range conditioned the degree of invasion in deforested areas. The annual deforestation rate changed notably between periods: ~1.5% from 1975 to 1987, ~0.8% from 1987 to 2000, and finally a very high rate of ~7.5% between 2000 and 2001. We explained these inconstant rates through some specific interrelated local and national political and socioeconomic drivers, namely land use policies, credit and tenure incentives, demography, and in particular, a severe national economic and bank crisis.
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Ecuador |
remote sensing |
Andes |
fragmentation |
land cover change |
bracken fern |
deforestation drivers |
Landsat |
image pre-processing |
attractors of landscape change |
Vorpahl, P.; Dislich, C.; Elsenbeer, H.; Märker, M. & Schröder, B. (2012): Biotic controls on shallow translational landslides. Earth Surface Processes and Landforms 38, 198-212.
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DOI: 10.1002/esp.3320
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In undisturbed tropical montane rainforests massive organic layers accommodate the majority of roots and only a small fraction of roots penetrate the mineral soil. We investigated the contribution of vegetation to slope stability in such environments by modifying a standard model for slope stability to include an organic layer with distinct mechanical properties. The importance of individual model parameters was evaluated using detailed measurements of soil and vegetation properties to reproduce the observed depth of 11 shallow landslides in the Andes of southern Ecuador. By distinguishing mineral soil, organic layer and aboveground
biomass, it is shown that in this environment vegetation provides a destabilizing effect mainly due to its contribution to the mass of the organic layer (up to 973 t ha1 under wet conditions). Sensitivity analysis shows that the destabilizing effect of the mass of soil and vegetation can only be effective on slopes steeper than 37.9. This situation applies to 36% of the study area. Thus, on the steep slopes of this megadiverse ecosystem, the mass of the growing forest promotes landsliding, which in turn promotes a new cycle of succession. This feedback mechanism is worth consideration in further investigations of the impact of landslides on plant diversity in similar environments.
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soil characteristics |
landslide |
landslide risk |
factor of safety |
Krüger, C. (2014): Arbuscular mycorrhizal fungi for reforestation of native tropical trees in the Andes of South Ecuador LMU München, phd thesis
Krüger, C.; Walker, C. & Schüßler, A. (2014): Scutellospora savannicola: redescription, epitypification, DNA barcoding and transfer to Dentiscutata . Mycological Progress 13(4), 1165-1178.
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DOI: 10.1007/s11557-014-1005-z
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An arbuscular mycorrhizal fungus (AMF) was isolated from a south Ecuadorian reforestation site in the vicinity of a pristine mountain rainforest ecosystem. Morphologically, it corresponded with the description of an AMF first described from Cuba as Gigaspora savannicola, before it was placed in Scutellospora. No living culture of this species has been available previously to allow detailed morphological review or DNA barcoding. After comparison of the morphology of the holotype and authenticated specimens with that of the Ecuadorian isolate, it was concluded that they are conspecific. A detailed redescription of the species is provided, including morphological characters not included in the original description, and an epitype is designated. To provide an extended DNA barcode for this AMF species, intraspecific variants of the near full-length small subunit rRNA gene (SSU) and a rDNA region comprising part of the SSU, the internal transcribed spacer (ITS) region including the 5.8S rRNA gene, and part of the large subunit rRNA gene (LSU) were sequenced. Phylotaxonomic analyses confirmed the classification in the genus Scutellospora sensu lato in a phylogenetic clade that, based on questionable evidence, was considered to circumscribe a distinct genus, Fuscutata. Recently, this genus was merged with Dentiscutata. Consequently, we move S. savannicola (=Fuscutata savannicola?=?Gigaspora savannicola) to the genus Dentiscutata (Gigasporaceae).
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AM fungi |
Werner, F.A.; Jantz, N.; Krashevska, V.; Peters, T.; Behling, H.; Maraun, M.; Scheu, S. & Brehm, G. (2014): Climate Change Effects on Biodiversity and Ecosystem Functioning. In: Bendix, J., Beck, E., Bräuning, A., Makeschin, F., Mosandl, R., Scheu, S., Wilcke, W. (eds.): Ecosystem Services, Biodiversity and Environmental Change in a Tropical Mountain Ecosystem of South ( ), Springer.
Rodriguez, F.; Bräuning, A.; Gerique, A.; Behling, H. & Volland, F. (2013): Landscape History, Vegetation History and Past Human Impacts. In: Bendix, J., Beck, E., Bräuning, A., Makeschin, F., Mosandl, R., Scheu, S., Wilcke, W. (eds.): Ecosystem Services, Biodiversity and Environmental Change in a Tropical Mountain Ecosystem of South ( 221), Springer, 53-66.
Villota, A. & Behling, H. (2014): Late Glacial and Holocene environmental change inferred from the páramo of Cajanuma in the Podocarpus National Park, southern Ecuador. Caldasia 36, 345-364.
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To reconstruct the environmental history including vegetation, fire and climate dynamics, from the Cajanuma valley area (3285 m elevation) in the Podocarpus National Park, southern Ecuador, we address the following major research question: (1) How did the mountain vegetation developed during the late Glacial and Holocene? (2) Did fire played an important control on the vegetation change and was it natural or of anthropogenic origin?. Palaeoenvironmental changes were investigated using multiple proxies such as pollen, spores, charcoal analyses and radiocarbon dating. Pollen data indicated that during the late Glacial and transition to the early Holocene (ca. 16 000–10 500 cal yr BP) herb páramo was the main vegetation type around the study area, while subpáramo and mountain rainforest were scarcely represented. The early and mid-Holocene (ca. 10 500 to 5600 cal yr BP) is marked by high abundance of páramo during the early Holocene followed by a slight expansion of mountain forest during the mid-Holocene. During the mid- to late Holocene (ca. 5600–1200 cal yr BP) there is a significant presence of páramo and subpáramo while Lower Mountain Forest decreased substantially, although, Upper Mountain Forest remained relatively stable during this period. The late Holocene, from ca. 1200 cal yr BP to present, was characterized by páramo; however, mountain forest and subpáramo presented significantly abundance compared to the previous periods. Fires became frequent since the late Holocene. The marked increased local and regional fire intensity during the wetter late Holocene strongly suggests that were of anthropogenic origin. During the late Glacial and early Holocene, the upper forest line was located at low elevations; but shifted slightly upslope to higher elevations during the mid-Holocene.
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palynology |
human disturbance |
Palaeoecology |
vegetation history |
Villota, A. & Behling, H. (2013): Late Quaternary vegetation, climate and fire dynamics, human impact and evidence of past Polylepis populations in the northern Andean Depression inferred from the El Cristal record, in southeastern Ec. Ecotropica 19, 49-68.
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Late Pleistocene and Holocene vegetation, climate, and fire dynamics, as well as human impact, were studied in the El Cristal region, which is part of the Andean Depression in southeastern Ecuador. The sediment core from a small basin at 2056 m a.s.l. was analyzed by pollen and charcoal analysis and dated by six radiocarbon dates. The record indicates that during the late Pleistocene (ca. 19 750–12 500 cal yr BP) the Upper Mountain Rainforest (UMF), with some smaller areas of páramo and subpáramo were the main vegetation type in the study area. Additionally, there is evidence for Polylepis woodland in the region during this period, which does not exist in the area today. During the transition from the late Pleistocene to the early and mid-Holocene between ca. 12 500 to 3600 cal yr BP, there is a significant presence of mountain rainforest and stable proportions of subpáramo and páramo taxa. The early Holocene from ca. 11 500 to 7800 cal yr BP is characterized by UMF vegetation at the study site. Polylepis became more frequent and reached its maximum. During the mid-Holocene between 7800 to 3600 cal yr BP, the composition of the UMF changed. Polylepis decreased after ca. 4000 cal yr BP, probably due to higher fire frequency. During the mid- to late Holocene, human landscape dis- turbance is evident, especially between ca. 2000 and 1380 cal yr BP, with Asteraceae, Muehlenbeckia/Rumex, Osmunda and Huperzia all increasing in abundance. The late Holocene, from ca. 1380 cal yr BP, was characterized by an increased abundance of páramo taxa and a decrease in mountain rainforest taxa. The expansion of grassland during the late Holocene is interpreted as a result of an increase in human activity, which limited forest vegetation to isolated patches. However, between ca. 1200 and 900 cal yr BP the UMF expanded, probably due to forest recovery after the high frequency of fire. Between ca. 90
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palynology |
Palaeoecology |
Polylepis |
vegetation history |
Niemann, H.; Matthias, I.; Michalzik, B. & Behling, H. (2015): Late Holocene human impact and environmental change inferred from a multi-proxy lake sediment record in the Loja region, southeastern Ecuador. Quaternary Internation 308-309(308), 253.
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Late Holocene human impact and environmental changes were reconstructed from a sediment core of the Laguna Daniel Alvarez (2200 m asl) located on the outskirts of the city of Loja, southeastern Ecuador. Palaeoenvironmental changes were investigated by pollen, spore, algae and charcoal analysis in com- bination with X-Ray Fluorescence (XRF) scanning and element analysis of d13C, Total Organic Carbon (TOC), Total Nitrogen (TN) and radiocarbon dating. This multi-proxy study provides in detail the set- tlement history in the inner-Andean dry valley in southern Ecuador over the last ca. 1400 years.
Between 630 and 1470 AD, Zea mays was intensively cultivated around the studied lake by the native Palta culture in the Loja region. After ca. 1470 AD, Z. mays cultivation collapsed, accompanied by an increase in fallow vegetation, such as Mimosa and Poaceae, probably as a result of the Inca invasion and occupation from 1463 to 1531 AD in southern Ecuador. After ca. 1570 AD, Amaranthaceae/Chenopo- diaceae markedly increased, re?ecting the beginning of the Spanish Conquest. In 1531 AD, Loja became Spanish and, during the ?rst ca. 100 years of the Spanish regime, Loja developed into the forti?ed capital of the province. In the 17th century, crop growing strongly declined due to the diminished indigenous population that probably suffered from new diseases introduced by the Spanish invaders. Pinus and Eucalyptus as well as Plantago lanceolata were introduced in the Loja region about 220 years ago.
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Keywords: |
palynology |
human disturbance |
Palaeoecology |
vegetation history |
Huth, A.; Dislich, C.; Florian, H. & Thorsten, W. (2014): Approximate Bayesian parameterization of a process-based tropical forest model. Biogeosciences 11, 1261-1272.
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DOI: 10.5194/bg-11-1261-2014
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Abstract:
Abstract:
Inverse parameter estimation of process-based
models is a long-standing problem in many scientific disciplines.
A key question for inverse parameter estimation
is how to define the metric that quantifies how well model
predictions fit to the data. This metric can be expressed by
general cost or objective functions, but statistical inversion
methods require a particular metric, the probability of observing
the data given the model parameters, known as the
likelihood.
For technical and computational reasons, likelihoods for
process-based stochastic models are usually based on general
assumptions about variability in the observed data, and not
on the stochasticity generated by the model. Only in recent
years have new methods become available that allow the generation
of likelihoods directly from stochastic simulations.
Previous applications of these approximate Bayesian methods
have concentrated on relatively simple models. Here, we
report on the application of a simulation-based likelihood
approximation for FORMIND, a parameter-rich individualbased
model of tropical forest dynamics.
We show that approximate Bayesian inference, based on
a parametric likelihood approximation placed in a conventional
Markov chain Monte Carlo (MCMC) sampler, performs
well in retrieving known parameter values from virtual
inventory data generated by the forest model. We analyze
the results of the parameter estimation, examine its sensitivity
to the choice and aggregation of model outputs and
observed data (summary statistics), and demonstrate the application
of this method by fitting the FORMIND model to
field data from an Ecuadorian tropical forest. Finally, we discuss
how this approach differs from approximate Bayesian
computation (ABC), another method commonly used to generate
simulation-based likelihood approximations.
Our results demonstrate that simulation-based inference,
which offers considerable conceptual advantages over more
traditional methods for inverse parameter estimation, can be
successfully applied to process-based models of high complexity.
The methodology is particularly suitable for heterogeneous
and complex data structures and can easily be adjusted
to other model types, including most stochastic population
and individual-based models. Our study therefore provides
a blueprint for a fairly general approach to parameter
estimation of stochastic process-based models.
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Keywords: |
FORMIND |
aboveground biomass |
forest model |
Schmid, M. & Schreiber, K. (2015): Afforestation with Pinus patula in the Andean highlands of Ecuador: forest inventory and biomass of single trees Technische Universität München, master thesis
Posselt, S. (2010): Influence of silvicultural treatments on natural regeneration in a tropical mountain rainforest in Ecuador Technische Universität München, diploma thesis
Loaiza, P. (2011): Effects of fertilization and grass competition (Setaria sphacelata) on root development and biomass allocation in three native tree species from Ecuador Technische Universität München, master thesis