Középhegységi lomberdők természetes bolygatásainak vizsgálata távérzékeléses módszerekkel = Study of natural disturbance patterns in submontane deciduous woods using remote sensing techniques

Elvégzett kutatásunkkal mind az erdők finom-léptékű mintázatát meghatározó lékdinamika, mind a durva mintázatot meghatározó intenzív, nagy kiterjedésű bolygatások mértékéről, jellemző mintázatairól gyűjtöttünk új - eddig szinte teljesen hiányzó - ismereteket távérzékeléses technikák alkalmazásával. A börzsönyi gazdasági erdőket ért jég- és szél által okozott bolygatások mintázatainak leírásán felül megmutattuk, hogy az egyes állományok kárérzékenysége nem csak domborzati helyzetüktől (magasság, kitettség, meredekség), hanem olyan állományjellemzőktől is függ, amelyekre az előgazdálkodó befolyással bír (pl. előhasználatok intenzitása, kor- és méreteloszlás). Két természetközeli állomány lédinamikai jellemzőit tártuk fel 25 éves időintervallumra, leírtuk a lékek mennyiségét, méreteloszlását az egyes időpontokra, illetve a feltártuk az egyes lékdinamikai események (új lékek keletkezése, régiek bezáródása, szomszédosak összenyílása) fontosságát. Vizsgáltuk a felújulás lékméret- és nagyvad-sűrűség függését. Eredményeink felhasználhatók a természetközeli erdőgazdálkodás megalapozásában, olyan alternatív kezelések kidolgozásával, amelyek az erdők szerkezeti diverzitását növelik, stabilitását nem csökkentik, és ezért természetvédelmi és gazdasági érdekeket is kiszolgálhatnak. | Our research provided new information on the extent and characteristic patterns of both fine-scale patch dynamics and of intensive large-scale disturbances affecting our forests. We used remote sensing techniques. In addition to quantifying aerial extent and intensity of the the large-scale intensive ice and wind disturbances that hit the commercial forests of the Börzsöny Mts., we also showed how the sensitivity of the stands was related to topographic features (elevation, aspect, slope steepness) and also to stand characteristics affected by management (intensity of former cuts, age- and size distribution). We also studied how regeneration is related to gap size and to effects of browsing game. We studied 25 years of gap dynamics in two near-natural beech stands by describing aerial extent, size distribution and spatial pattern of canopy gaps for each time step. We also quantified the importance of different dynamical processes (gap creation, gap closure, merger of gaps). Applications of our results might contribute to the development of new techniques that increase biodiversity, maintain stability, hence serving nature-based silviculture and conservation management

LIDAR ÉS TOPOGRÁFIAI TÉRKÉP ALAPÚ DIGITÁLIS TEREPMODELLEKBŐL LEVEZETETT, ILLETVE KÉZZEL DIGITALIZÁLT TÖBÖR-KÖRVONALAK MORFOMETRIAI ÖSSZEHASONLÍTÁSA AZ AGGTELEKI-KARSZT PÉLDÁJÁN

An advantageous consequence of the rapid evolution of topographic data acquisition techniques is possibility to define the topography with increasingly higher accuracy. New remote sensing techniques and data processing methods allow to detect microtopographic features of karst phenomena with unprecedented precision. Our aim in this study was to compare the digital terrain models (DTMs) generated from various data sources acquired by different technologies to define dolines in the Hungarian part of the Gömör-Torna karst. An automated method of doline recognition is presented here; the results of this processing technique is compared to that of the classic outlining. We compared the three doline database using geomorphometric tools. Our conclusion is that, however, the classic method is efficient, but the LiDAR DTM-based method is more accurate in detecting and analyzing doline

The advantage of lidar digital terrain models in doline morphometry compared to topographic map based datasets – Aggtelek karst (Hungary) as an example

Doline morphometry has always been in the focus of karst geomorphological research. Recently, digital terrain model (DTM) based methods became widespread in the study of dolines. Today, LiDAR datasets provide high resolution DTMs, and automated doline recognition algorithms have been developed. In this paper, we test different datasets and a doline recognition algorithm using Aggtelek Karst (NE-Hungary) dolines as a case example. Three datasets are compared: “TOPO” dolines delineated by the classical outermost closed contour method using 1:10,000 scale topographic maps, “KRIG” dolines derived automatically from the DTM created by kriging interpolation from the digitized contours of the same topographic maps, and finally “LiDAR” dolines derived automatically from a DTM created from LiDAR data. First, we analyzed the sensitivity of the automatic method to the “depth limit” parameter, which is the threshold, below which closed depressions are considered as “errors” and are filled. In the actual case, given the typical doline size of the area and the resolution of the DTMs, we found that ca. 0.5 m is the optimal depth limit for the LiDAR dataset and 1 m for the KRIG dataset. The statistical distributions of the morphometrical properties were similar for all datasets (lognormal distribution for area and gamma distribution for depth), but the DTM-based methodology resulted larger dolines with respect to the classical method. The planform area (and related characteristics) showed very high correlations between the datasets. Depth values were less correlated and the lowest (moderately strong) correlations were observed between circularity values of the different datasets. Slope histograms calculated from the LiDAR data were used to cluster dolines, and these clusters differentiated dolines similarly to the classical depth-diameter ratio. Finally, we conclude that in the actual case, dolines can be morphometrically well characterized even by the classical topographic method, though finer results can be achieved for the depth and shape related parameters by using LiDAR data.Key words: doline morphometry, LiDAR, interpolation, slope histogram, sink point. Prednost lidarskega digitalnega modela reliefa za raziskavo morfometrije vrtač v primerjavi s podatkovno bazo topografskih kart − primer Agteleškega krasa (Madžarska)Morfometrija vrtač je bila vedno v središču kraških geomorfoloških raziskav. V zadnjem času so pri raziskavah vrtač postale zelo razširjene metode, ki temeljijo na digitalnem modelu reliefa (DMR). Lidarski podatki zagotavljajo visoko ločljivostne DMR-je, razviti so bili avtomatski algoritmi za prepoznavanje vrtač. V tem prispevku smo na primeru Agteleškega krasa v severovzhodni Madžarski preizkusili različne podatkovne baze in algoritme za prepoznavanje vrtač. Primerjali smo tri podatkovne baze: "TOPO" vrtače so razmejene na klasičen način z zunanjo zaprto plastnico na topografski karti v merilu 1: 10.000, "KRIG" vrtače so v istem merilu s pomočjo kriginga samodejno pridobljene iz digitaliziranih plastnic DMR, in "LiDAR" vrtače so samodejno pridobljene iz DMR, ki je ustvarjen iz lidarskih podatkov. Najprej smo analizirali občutljivost avtomatske metode parametra "mejne globine", ki predstavlja prag, pod katerim se depresijske oblike štejejo kot "napake" in so zapolnjene. V konkretnem primeru smo glede na običajno velikost vrtače in ločljivosti DMR ugotovili, da je optimalna globinska meja za LiDAR ca. 0,5 m in 1 m za KRIG. Pri vseh podatkovnih bazah so bile statistične porazdelitve morfometrijskih lastnosti (logaritemska normalna porazdelitev za prostor in gama porazdelitev za globino) podobne, vendar metodologija, ki temelji na DMR privede do rezultatov, ki kažejo na večje vrtače v primerjavi s klasično metodo. Rezultati območij vrtač (in njihovih značilnosti) so pokazali zelo visoke korelacije med podatkovnimi nizi. Pri globinah so bile korelacije manjše in najnižje zabeležene korelacije (srednje močne) so bile med podatki različnih podatkovnih bazah. Histogrami naklona, izračunani iz lidarskih podatkov, so bili uporabljeni za združevanje vrtač, in ti grozdi razlikujejo vrtače glede na klasično razmerje med globino in premerom. Na koncu smo ugotovili, da lahko v konkretnem primeru dobro določimo morfometrične lastnosti vrtač s klasičnimi topografskimi metodami. Podrobnejše rezultate o globinah in oblikah lahko dosežemo na podlagi lidarskih podatkov.Ključne besede: morfometrija vrtač, LiDAR, interpolacija, histogram naklona, ponor

Relationship of Tree Stand Heterogeneity and Forest Naturalness

The aim of our study was to investigate if compositional (tree species richness) andstructural (vertical structure, age-structure, patterns of canopy closure) heterogeneity of the canopylayer is related to individual naturalness criteria and to overall forest naturalness at the stand scale. Thenaturalness values of the assessed criteria (tree species composition, tree stand structure, speciescomposition and structure of shrub layer and forest floor vegetation, dead wood, effects of game, sitecharacteristics) showed similar behaviour when groups of stands with different heterogeneity werecompared, regardless of the studied aspect of canopy heterogeneity. The greatest difference was foundfor criteria describing the canopy layer. Composition and structure of canopy layer, dead wood andtotal naturalness of the stand differed significantly among the stand groups showing consistentlyhigher values from homogeneous to the most heterogeneous group. Naturalness of the compositionand structure of the shrub layer is slightly but significantly higher in stands with heterogeneous canopylayer. Regarding other criteria, significant differences were found only between the homogeneous andthe most heterogeneous groups, while groups with intermediate level of heterogeneity did not differsignificantly from one extreme. However, the criterion describing effects of game got lowernaturalness values in more heterogeneous stands. Naturalness of site characteristics did not differsignificantly among the groups except for when stands were grouped based on pattern of canopyclosure. From the practical viewpoint it is shown that purposeful forestry operations affecting thecanopy layer cause changes in compositional and structural characteristics of other layers as well as inoverall stand scale forest naturalness

A novel forest state assessment methodology to support conservation and forest management planning

A new forest state assessment methodology to complement existing conservation and forestry data has been developed. The aim is to provide tools for strategic planning including spatial distribution of conservation priorities. The method is point-based using a dense systematic sampling grid and provides more detailed information than vegetation maps or forest subcompartment descriptions, but requires less effort than forest inventories. Indicators include canopy composition and structure, deadwood, herbs, microhabitats, disturbances, shrubs and regeneration. The results can inform managers about the structural and compositional diversity of forest stands in the form of thematic maps and can provide the basis for analysis of habitat suitability for forest-dwelling organisms. A smartphone application has been developed to enable electronic data collection. PostGIS and Python scripts were used in the data flow. In this paper, we outline the development of the assessment protocol, and present the sampling design and the variables recorded. The main advantages of the survey methodology are also shown by case-studies based on data collected during the first field season in 2014. The protocol has been designed for low mountain forests in Hungary, but it can be modified to fit other forest types