12 results on '"Berger, Ambros"'
Search Results
2. Deriving regional pedotransfer functions to estimate soil bulk density in Austria
- Author
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Foldal Cecilie, Jandl Robert, Bohner Andreas, and Berger Ambros
- Subjects
land-use ,regional calibration ,multiple regression ,monte carlo ,cross validation ,landnutzung ,regionale kalibrierung ,kreuzvalidierung ,Environmental sciences ,GE1-350 - Abstract
Soil bulk density is a required variable for quantifying stocks of elements in soils and is therefore instrumental for the evaluation of land-use related climate change mitigation measures. Our motivation was to derive a set of pedotransfer functions for soil bulk densities usable to accommodate different levels of data availabilities. We derived sets of linear equations for bulk density that are appropriate for different forms of land-use. After introducing uncertainty factors for measured parameters, we ran the linear models repeatedly in a Monte Carlo simulation in order to test the impact of inaccuracy. The reliability of the models was evaluated by a cross-validation. The single best predictor of soil bulk density is the content of soil organic carbon, yielding estimates with an adjusted R2 of approximately 0.5. A slight improvement of the estimate is possible when additionally, soil texture and soil depth are known. Residual analysis advocated the derivation of land-use specific models. Using transformed variables and assessing land-use specific pedotransfer functions, the determination coefficient (adjusted R2) of the multiple linear models ranged from 0.43 in cropland up to 0.65 for grassland soils. Compared to pedotransfer function, from the literature, the performance of the linear modes were similar but more accurate. Taking into account the likely inaccuracies when measuring soil organic carbon, the soil bulk density can be estimated with an accuracy of +/− 9 to 25% depending on land-use. We recommend measuring soil bulk density by standardized sampling of undisturbed soil cores, followed by post-processing of the samples in the lab by internationally harmonized protocols. Our pedotransfer functions are accurately and transparently presented, and derived from well-documented and high-quality soil data sets. We therefore consider them particularly useful in Austria, where the measured values for soil bulk densities are not available. more...
- Published
- 2021
- Full Text
- View/download PDF
Catalog
3. Evaluating Tree Species Mapping: Probability Sampling Validation of Pure and Mixed Species Classes Using Convolutional Neural Networks and Sentinel-2 Time Series.
- Author
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Schadauer, Tobias, Karel, Susanne, Loew, Markus, Knieling, Ursula, Kopecky, Kevin, Bauerhansl, Christoph, Berger, Ambros, Graeber, Stephan, and Winiwarter, Lukas
- Subjects
THEMATIC maps ,CONVOLUTIONAL neural networks ,FOREST biodiversity ,REMOTE-sensing images ,FOREST surveys - Abstract
The accurate large-scale classification of tree species is crucial for the monitoring, protection, and management of the Earth's invaluable forest ecosystems. Numerous previous studies have recognized the suitability of satellite imagery, particularly Sentinel-2 imagery, for this task. In this study, we utilized a dense phenology Sentinel-2 time series, which offered consistent data across multiple granules, to map tree species across the entire forested area in Austria. Aiming for the classification scheme to more accurately represent actual forest conditions, we included mixed tree species and sparsely populated classes (classes with sparse canopy cover) alongside pure tree species classes. To enhance the training data for the mixed and sparse classes, synthetic data creation was employed. Autocorrelation has significant implications for the validation of thematic maps. To investigate the impact of spatial dependency on validation data, two methods were employed at numerous split and buffer distances: spatial split validation and a validation method based on a buffered ground reference probability samples provided by the National Forest inventory (NFI). While a random training data holdout set yielded 99% accuracy, the spatial split validation resulted in 74% accuracy, emphasizing the importance of accounting for spatial autocorrelation when validating with holdout sets derived from polygon-based training data. The validation based on NFI data resulted in 55% overall accuracy, 91% post-hoc pure class accuracy, and 79% accuracy when confusions in phenological proximity were disregarded (e.g., spruce–larch confused with spruce). The significant differences in accuracy observed between spatial split and NFI validation underscore the challenge for polygon-based training data to capture ground reference forest complexity, particularly in areas with diverse forests. This hardship is further accentuated by the pure class accuracy of 91%, revealing the substantial impact of mixed stands on the accuracy of tree species maps. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
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4. Variation in soil organic carbon stocks in Singapore with forest succession and land management.
- Author
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Kleine, Michael, Ghosh, Subhadip, Leitgeb, Ernst, Berger, Ambros, Ibrahim, Hassan bin, Gschwantner, Thomas, Ow, Lai Fern, and Michel, Kerstin
- Abstract
Land-use changes and forest management decisions can profoundly alter soil organic carbon (SOC) stocks. Therefore, the objective of this study was to investigate whether existing SOC stocks in the forests of Singapore can be related to successional stages of forest vegetation following disturbances. A forest classification system was developed using information about land use history and vegetation data from 21 inventory plots collected within the framework of Singapore's IPCC-compatible greenhouse gas reporting system. The forest successional classes obtained were related to SOC stocks (0–50 cm) determined on the same plots. The inventory plots were assigned to four classes. Primary forests (Class 1) were dominated by late succession native species. Secondary forests representing natural forest succession (Class 2) contained younger native trees and a few large trees. Secondary forests after tree plantation/fruit orchard (Class 3) and after agricultural crop cultivation (Class 4) were characterised by large proportions of exotic tree species. Maximum stocks of SOC declined from Class 1 (127.7 Mg ha
−1 ) to Class 4 (35.2 Mg ha−1 ). The results of a principal component analysis confirmed our forest classification. Plant-related parameters can be successfully used to classify the forests in Singapore, which also show clear differences in SOC. [ABSTRACT FROM AUTHOR] more...- Published
- 2022
- Full Text
- View/download PDF
5. The effects of truncating the angle count sampling method on the Austrian National Forest Inventory.
- Author
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Berger, Ambros, Gschwantner, Thomas, and Schadauer, Klemens
- Abstract
Key message : Truncating the angle count sampling plots leads to a higher stock estimate because fewer trees are missed. It also causes a higher uncertainty of the estimates. Context: The Austrian National Forest Inventory changed its plot design to angle count sampling plots that are limited to circles of 300 m2 . A fixed plot size is beneficial for multistage inventory systems. Aims: This study aims to quantify the ensuing effects on the national forest inventory on the plot and the national level regarding stock estimates and their uncertainty along with effects on as well as of upper diameter models. Methods: Fully surveyed large-scale plots with simulated angle count samples were used to gauge the increase of variability. The full NFI 2007/09 data set was employed to simulate truncations at different distances as well as to parameterise eight alternatives for upper diameter models and to analyse the effects on the stock estimates. Results: There is an increase in the stock estimate because the probability of missing sample trees is reduced. The change in upper diameter models had little effect. Conclusion: The truncation removes a source of bias, facilitates field work, and is a favourable way forward. [ABSTRACT FROM AUTHOR] more...- Published
- 2020
- Full Text
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6. Correction to: Harmonised projections of future forest resources in Europe.
- Author
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Vauhkonen, Jari, Berger, Ambros, Gschwantner, Thomas, Schadauer, Klemens, Lejeune, Philippe, Perin, Jérôme, Pitchugin, Mikhail, Adolt, Radim, Zeman, Miroslav, Johannsen, Vivian Kvist, Kepfer-Rojas, Sebastian, Sims, Allan, Bastick, Claire, Morneau, François, Colin, Antoine, Bender, Susann, Kovácsevics, Pál, Solti, György, Kolozs, László, and Nagy, Dóra more...
- Published
- 2019
- Full Text
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7. The European Forestry Dynamics Model: Concept, design and results of first case studies
- Author
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PACKALEN Tuula, SALLNAES PETTER, SIRKIA Seija, KOHONEN Kari, SALMINEN Olli, VIDAL CLAUDE, ROBERT Nicolas, COLIN Antoine, BELOUARD Thierry, SCHADAUER Klemens, BERGER Ambros, REGO Francisco, LOURO Graca, CAMIA Andrea, RÄTY MINNA, and SAN-MIGUEL-AYANZ Jesus more...
- Abstract
The European Forestry Dynamics Model (EFDM) is a joint effort between the European Commission Joint Research Centre and partners in the EU Member States for the development of a forestry dynamics model. The model is expected to project the state of Europe’s forests given different climatic, economic and management scenarios. EFDM was designed as a flexible system to facilitate the different types of data input that are available from the diverse National Forest Inventories. The model captures different typologies such as site productivity, ownership and the probability of natural disturbances. Specifically, EFDM is able to process detailed national-level input data such as National Forest Inventories (NFI) outputs, as well as related national-level expertise in social and economic domains. In this way, the system supports effective utilization of the collaborative expertise in the parameterization of scenarios. This document is intended as a general introduction to the EFDM. Experiences gained from the EFDM test applications by five NFI teams (Austria, Finland, France, Portugal and Sweden) are also summarized in this report., JRC.H.3-Forest Resources and Climate more...
- Published
- 2014
8. Austria.
- Author
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Gschwantner, Thomas, Berger, Ambros, Büchsenmeister, Richard, and Hauk, Elmar
- Published
- 2016
- Full Text
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9. An Area-Based Matrix Model for Uneven-Aged Forests.
- Author
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Sallnäs, Ola, Berger, Ambros, Räty, Minna, and Trubins, Renats
- Subjects
FORESTS & forestry ,HARVESTING ,DISASTERS ,MATHEMATICAL models ,SIMULATION methods & models ,LARGE scale systems - Abstract
In this paper a new concept for modeling uneven-aged forests (UEAF) is presented. The term UEAF in this article encloses all forests that deviate from the even-aged structure. The matrix model is area-based, in that the forest under study is described by a distribution of areas over fixed state-spaces spanned by stem number and volume per hectare classes. Dynamics is introduced as transitions of areas inside the state-space during the simulation. Harvesting activities and the occurrence of calamities are explicitly handled. The model is designed to be suitable for large-scale analyses. The concept was tested in an application to Austrian National Forest Inventory (NFI) data. Results shown, including a comparison to older inventory data, indicate that it is worth further elaborating on the concept and the model. The work will be continued and in the next step the model concept will be applied in several other countries. [ABSTRACT FROM AUTHOR] more...
- Published
- 2015
- Full Text
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10. Effects of Measurement Errors on Individual Tree Stem Volume Estimates for the Austrian National Forest Inventory.
- Author
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Berger, Ambros, Gschwantner, Thomas, McRoberts, Ronald E., and Schadauer, Klemens
- Abstract
National forest inventories typically estimate individual tree volumes using models that rely on measurements of predictor variables such as tree height and diameter, both of which are subject to measurement error. The aim of this study was to quantify the impacts of these measurement errors on the uncertainty of the model-based tree stem volume estimates. The impacts were investigated using two approaches: the law of propagation of error and Monte Carlo simulation. Estimates of total uncertainty also included variability associated with the model itself. Results for both approaches indicate that the relative standard deviation over plots of the volume estimates for all tree species is approximately 11 %. A partition of the total uncertainty by sources indicates that error in measurement of the upper diameter makes the greatest contribution. Thus, the greatest potential for improvement in the precision of overall estimates lies in increasing the accuracy of upper diameter measurements. Although the uncertainty of individual tree stem volume estimates may be considered negligible for nationwide assessments of growing stock volume, it is relevant for small-scale and plot-level estimates used as training or accuracy assessment data for remote sensing applications that rely on emerging technologies such as airborne laser scanning. [ABSTRACT FROM AUTHOR] more...
- Published
- 2014
- Full Text
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11. Event-based dynamics of the soil water content at Alpine sites (Tyrol, Austria).
- Author
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Hagen, Karl, Berger, Ambros, Gartner, Karl, Geitner, Clemens, Kofler, Thomas, Kogelbauer, Ilse, Kohl, Bernhard, Markart, Gerhard, Meißl, Gertraud, and Niedertscheider, Klaus
- Subjects
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SOIL dynamics , *SOIL moisture , *WATER storage , *REMOTE sensing , *FORECASTING - Abstract
• The event-based approach yields statistical functions and quality assessment. • The initial soil moisture conditions are crucial to the water storage capacity. • Two parameter models can estimate the in situ water storage capacity of soils. • Antecedent precipitation is unsuitable for estimating initial soil moisture content. The relevance of the soil moisture content (SMC) for runoff processes and thus for flood prediction is rather undisputed; however, there are still gaps in our knowledge of the precipitation – soil moisture reaction pattern. A new event-based approach, using statistical methods to analyse monitoring data, is presented and applied for soil moisture data of three test sites, situated in different parts of the Tyrolean Alps (Austria). The analyses revealed a significant influence of the initial soil moisture on the remaining soil storage capacity. A comparison of the value pairs initial soil moisture and soil moisture difference (SMC max caused by rain events minus initial SMC) resulted in funnel-shaped distributions, whereby the upper boundary of the data should roughly match the field capacity of the soils. For purposes of flood prediction, precipitation sums and initial conditions are the relevant variables, while precipitation duration, intensities, and antecedent precipitation have significantly less influence on SMC. However, the functions describing the relationship between precipitation and SMC showed poor model fits despite their significance. The linkage of soil moisture content between different depths, which, inter alia , are important when using remote sensing data for spatial SMC estimations, showed that the soil moisture conditions in the upper layer do not necessarily represent the water storage state of the deeper layers. The relation strongly depends on the kind of transition between the horizons, underlining the great importance of proper spatial information on soil characteristics. Approaches to estimate the initial SMC at the beginning of heavy rainfall events on the basis of antecedent precipitation sums are not very promising due to the weak relationships between these parameters. [ABSTRACT FROM AUTHOR] more...
- Published
- 2020
- Full Text
- View/download PDF
12. Harmonised projections of future forest resources in Europe.
- Author
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Vauhkonen, Jari, Berger, Ambros, Gschwantner, Thomas, Schadauer, Klemens, Lejeune, Philippe, Perin, Jérôme, Pitchugin, Mikhail, Adolt, Radim, Zeman, Miroslav, Johannsen, Vivian Kvist, Kepfer-Rojas, Sebastian, Sims, Allan, Bastick, Claire, Morneau, François, Colin, Antoine, Bender, Susann, Kovácsevics, Pál, Solti, György, Kolozs, László, and Nagy, Dóra more...
- Subjects
FOREST surveys ,POLICY analysis ,DEFINITIONS ,FORESTS & forestry ,FOREST reserves ,FOREST policy - Abstract
• Key message A dataset of forest resource projections in 23 European countries to 2040 has been prepared for forest-related policy analysis and decision-making. Due to applying harmonised definitions, while maintaining country-specific forestry practices, the projections should be usable from national to international levels. The dataset can be accessed at 10.5061/dryad.4t880qh. The associated metadata are available at https://metadata-afs.nancy.inra.fr/geonetwork/srv/eng/catalog.search#/metadata/8f93e0d6-b524-43bd-bdb8-621ad5ae6fa9. [ABSTRACT FROM AUTHOR] more...
- Published
- 2019
- Full Text
- View/download PDF
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