Possibilities and Limitations of Spatially Explicit Site Index Modelling for Spruce Based on National Forest Inventory Data and Digital Maps of Soil and Climate in Bavaria (SE Germany)

Combining national forest inventory (NFI) data with digital site maps of high resolution enables spatially explicit predictions of site productivity. The aim of this study is to explore the possibilities and limitations of this database to analyze the environmental dependency of height-growth of Norway spruce and to predict site index (SI) on a scale that is relevant for local forest management. The study region is the German federal state of Bavaria. The exploratory methods comprise significance tests and hypervolume-analysis. SI is modeled with a Generalized Additive Model (GAM). In a second step the residuals are modeled using Boosted Regression Trees (BRT). The interaction between temperature regime and water supply strongly determined height growth. At sites with very similar temperature regime and water supply, greater heights were reached if the depth gradient of base saturation was favorable. Statistical model criteria (Double Penalty Selection, AIC) preferred composite variables for water supply and the supply of basic cations. The ability to predict SI on a local scale was limited due to the difficulty to integrate soil variables into the model

UAV-Based forest health monitoring : a systematic review

CITATION: Ecke, S. et al. 2022. UAV-Based forest health monitoring : a systematic review. Remote Sensing, 14(13):3205, doi:10.3390/rs14133205.The original publication is available at https://www.mdpi.comIn recent years, technological advances have led to the increasing use of unmanned aerial vehicles (UAVs) for forestry applications. One emerging field for drone application is forest health monitoring (FHM). Common approaches for FHM involve small-scale resource-extensive fieldwork combined with traditional remote sensing platforms. However, the highly dynamic nature of forests requires timely and repetitive data acquisition, often at very high spatial resolution, where conventional remote sensing techniques reach the limits of feasibility. UAVs have shown that they can meet the demands of flexible operation and high spatial resolution. This is also reflected in a rapidly growing number of publications using drones to study forest health. Only a few reviews exist which do not cover the whole research history of UAV-based FHM. Since a comprehensive review is becoming critical to identify research gaps, trends, and drawbacks, we offer a systematic analysis of 99 papers covering the last ten years of research related to UAV-based monitoring of forests threatened by biotic and abiotic stressors. Advances in drone technology are being rapidly adopted and put into practice, further improving the economical use of UAVs. Despite the many advantages of UAVs, such as their flexibility, relatively low costs, and the possibility to fly below cloud cover, we also identified some shortcomings: (1) multitemporal and long-term monitoring of forests is clearly underrepresented; (2) the rare use of hyperspectral and LiDAR sensors must drastically increase; (3) complementary data from other RS sources are not sufficiently being exploited; (4) a lack of standardized workflows poses a problem to ensure data uniformity; (5) complex machine learning algorithms and workflows obscure interpretability and hinders widespread adoption; (6) the data pipeline from acquisition to final analysis often relies on commercial software at the expense of open-source tools.https://www.mdpi.com/2072-4292/14/13/3205Publisher's versio

Application of Haralick’s Texture Features for Rapid Detection of Windthrow Hotspots in Orthophotos

Windthrow and storm damage are crucial issues in practical forestry. We propose a method for rapid detection of windthrow hotspots in airborne digital orthophotos. Therefore, we apply Haralick’s texture features on 50 × 50 m cells of the orthophotos and classify the cells with a random forest algorithm. We apply the classification results from a training data set on a validation set. The overall classification accuracy of the proposed method varies between 76% for fine distinction of the cells and 96% for a distinction level that tried to detect only severe damaged cells. The proposed method enables the rapid detection of windthrow hotspots in forests immediately after their occurrence in single-date data. It is not adequate for the determination of areas with only single fallen trees. Future research will investigate the possibilities and limitations when applying the method on other data sources (e.g., optical satellite data)

Tracing drought effects from the tree to the stand growth in temperate and Mediterranean forests: insights and consequences for forest ecology and management

25 Pág.How drought affects tree and stand growth is an old question, but is getting unprecedented relevance in view of climate change. Stress effects related to drought have been mostly studied at the individual tree level, mostly investigating dominant trees and using their responses as indicator for the impact at the stand level. However, findings at tree and stand level may differ, as the stand responses include interactions and feedbacks that may buffer or aggravate what is observed at the individual tree level. Here, we trace drought effects on growth and development from tree to the stand scale. Therefore, we analyse annually measured data from long-term experiments in temperate and Mediterranean forests. With this analysis, we aim to disclose how well results of dominant tree growth reflect stand-level behaviour, hypothesizing that drought resistance of dominant trees’ can strongly deviate from the overall sensitivity of the stand. First, we theoretically derive how drought responses at the stand level emerge from the tree-level behaviour, thereby considering that potential drought resistance of individual trees is modulated by acclimation and tree–tree interactions at the stand level and that the overall stress response at the stand level results from species-specific and size-dependent individual tree growth and mortality. Second, reviewing respective peer-reviewed literature (24 papers) and complementing findings by own measurements (22 experiments) from temperate and Mediterranean monospecific and mixed-species forests, we are able to reveal main causes for deviations of tree-level and stand-level findings regarding drought stress responses. Using a long-term experiment in Norway spruce (Picea abies (L.) KARST.) and European beech (Fagus sylvatica L.), we provide evidence that the species-dependent and size-dependent reactions matter and how the size–frequency distribution affects the scaling. We show by examples that tree-level derived results may overestimate growth losses by 25%. Third, we investigate the development of the growth dominance coefficient based on measurements gathered at the Bavarian forest climate stations. We show that drought changes stand biomass partitioning in favour of small trees, reduce social differentiation, and homogenize the vertical structure of forests. Finally, we discuss the drought-related consequences of the social class-specific growth reaction patterns for inventory and monitoring and highlight the importance of these findings for understanding site-specific stand dynamics, for forest modelling, and for silvicultural management.The publication is part of the CARE4C project that has received funding from the European Union’s HORIZON 2020 research and innovation program under the Marie Skłodowska-Curie grant Agreement No 778322. Thanks go also to the Bayerische Staatsforsten (BaySF) for supporting the establishment and maintenance of the underlying long-term experiments and to the Bavarian State Ministry for Nutrition, Agriculture and Forestry for funding the project "Adaptability of trees and forest stands to drought stress" (klifW006 # Z3-7831-1/1015) and for the permanent support of the project W007, entitled “Long-term experimental plots for forest growth and yield research” (# 7831-22209-2013). Thanks go furthermore to the Junta de Castilla y León, Spain, and the European Union for funding the Projects VA183P20 (SMART—Bosques mixtos: Selvicultura, Mitigación, Adaptación, Resiliencia y Trade-offs) and CLU-2019-01—iuFOR Institute Unit of Excellence of the University of Valladolid through the ERDF "Europe drives our growth". We also thank anonymous reviewers for their constructive criticismPeer reviewe

UAV-Based Forest Health Monitoring: A Systematic Review

In recent years, technological advances have led to the increasing use of unmanned aerial vehicles (UAVs) for forestry applications. One emerging field for drone application is forest health monitoring (FHM). Common approaches for FHM involve small-scale resource-extensive fieldwork combined with traditional remote sensing platforms. However, the highly dynamic nature of forests requires timely and repetitive data acquisition, often at very high spatial resolution, where conventional remote sensing techniques reach the limits of feasibility. UAVs have shown that they can meet the demands of flexible operation and high spatial resolution. This is also reflected in a rapidly growing number of publications using drones to study forest health. Only a few reviews exist which do not cover the whole research history of UAV-based FHM. Since a comprehensive review is becoming critical to identify research gaps, trends, and drawbacks, we offer a systematic analysis of 99 papers covering the last ten years of research related to UAV-based monitoring of forests threatened by biotic and abiotic stressors. Advances in drone technology are being rapidly adopted and put into practice, further improving the economical use of UAVs. Despite the many advantages of UAVs, such as their flexibility, relatively low costs, and the possibility to fly below cloud cover, we also identified some shortcomings: (1) multitemporal and long-term monitoring of forests is clearly underrepresented; (2) the rare use of hyperspectral and LiDAR sensors must drastically increase; (3) complementary data from other RS sources are not sufficiently being exploited; (4) a lack of standardized workflows poses a problem to ensure data uniformity; (5) complex machine learning algorithms and workflows obscure interpretability and hinders widespread adoption; (6) the data pipeline from acquisition to final analysis often relies on commercial software at the expense of open-source tools

Are Scots pine forest edges particularly prone to drought-induced mortality?

https://cdn.iopscience.com/content/1748-9326/13/2/025001/Mmedia/abstract-video-534b3b6b232c1276012a80177bfed9eb.converted.mp4Climate change is expected to exacerbate the frequency of drought-induced tree mortality world-wide. To better predict the associated change of species composition and forest dynamics on various scales and develop adequate adaptation strategies, more information on the mechanisms driving the often observed patchiness of tree die-back is needed. Although forest-edge effects may play an important role within the given context, only few corresponding studies exist. Here, we investigate the regional die-back of Scots pine in Franconia, Germany, after a hot and dry summer in 2015, thereby emphasizing possible differences in mortality between forest edge and interior. By means of dendroecological investigations and close-range remote sensing, we assess long-term growth performance and current tree vitality along five different forest-edge distance gradients. Our results clearly indicate a differing growth performance between edge and interior trees, associated with a higher vulnerability to drought, increased mortality rates, and lower tree vitality at the forest edge. Prior long-lasting growth decline of dead trees compared to live trees suggests depletion of carbon reserves in course of a long-term drought persisting since the 1990s to be the cause of regional Scots pine die-back. These findings highlight the forest edge as a potential focal point of forest management adaptation strategies in the context of drought-induced mortality

Von Frames und Slots bis Krambambuli : Beiträge zur zweisprachigen Lexikographie : Referate der zweiten internationalen Lexikographiekonferenz Jyväskylä, Finnland 24. - 26. 3. 1994

The present volume contains a general overview of current theoretical and practical issues in lexicography with special emphasis on bilingual applications. The contributions are divided into four sections. The first three record the plenary sessions of the Second International Conference on Lexicography in Jyvaskyla in March 1994. The fourth section contains papers from workshops thematically linked more or less closely to the plenary sessions. The first section, "General theory of lexicography and lexicology" is opened by R. R. K. Hartmann (Exeter) who reviews the four traditional aspects of research on dictionaries, the history, typology, critical assessment and use of dictionaries, discussing their particular relevance to bilingual lexicography. W. Martin (Amsterdam) then discusses dictionary definitions and models for the representation of knowledge. Martin favours what he calls deliberate inconsistency whereby the lexicographer, while basing his work on an explicit system such as the frames and slots of artificial intelligence, in fact restricts his definitions to the most relevant information. The definition of meaning is but one aspect of the lemma. A further essential aspect is the question of how words can be combined. M. Järventausta (Savonlinna) shows how recent considerations in valency theory can be used to describe and compare the respective combinatory characteristics of (partial) semantic equivalents in German and Finnish. U. Heid (Stuttgart) presents a similar topic from a different theoretical perspective in his workshop paper on the ordering of information on syntactic structures in a contrastive dictionary for machine translation. The problem of combination is also discussed in the second (plenary) section on "Aspects of contrastive lexicograpy". In H.-P. Kromann's (Kopenhagen) contribution, "How much grammar does a bilingual dictionary need?" the matter is firstly reviewed from a macro-, medio- and microstructural viewpoint and then critically demonstrated using entries for the preposition über in mono- and bilingual dictionaries as an example. J. Korhonen (Helsinki) then suggests a model for describing verb-idioms in German-Finnish and Finnish-German dictionaries. The same theme is taken up by J. Toomar (Jyväskylä) in her workshop paper, an analysis of the lemmatization of standard verbal idioms in a German-Finnish dictionary. R. Frisch (Jyväskylä/Wurzburg) and I. Hyvärinen (Jyväskylä) concern themselves with word formation and dictionaries. Frisch critically assesses the treatment of lemmatized word-formation elements in German-Finnish dictionaries whereas Hyvärinen looks at the formation of antonyms to see whether lemmatized antonyms can be used to reveal systematic contrasts between languages. L. Tossavainen (Jyväskylä) also deals with word formation and lexicography in her workshop paper, concentrating especially on the lemmatization of compound nouns. The two contributions in the section on "Particular questions of lexicography" lend the volume a historical dimension. A. F. Kelletat (Germersheim) takes a look at Comenius's "Orbis sensualium pictus" from 1658, pointing out how its didactic innovations anticipate bi- or multilingual illustrated learners' dictionaries. K Keinästö (Oulu) presents a wide range of more recent German loan words in Finnish and then traces the fate of the word Krambambuli through German, Scandinavian and Finnish dictionaries and encyclopedias. The workshop papers in the fourth section draw attention to various specific aspects and problems. Apart from the papers already mentioned above they include work by B. Fuchs (Jyväskylä) and D. Neuendorff (Oulu) connecting the critical evaluation of dictionaries with dictionary user research, further lexicosemantic papers by S. Tschirpke (Helsinki/ Greifswald) and A. Uurasjärvi (Tampere) on lexical families and lexical fields and a paper by J. Boger (Jyväskylä) illustrating the special problems of dialect lexicography with experience from the Low Saxon Dictionary