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Published in DiRROS: 05.06.2025; Views: 120; Downloads: 53
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Abstract: Tree height and vertical forest structure are important attributes in forestry, but their traditional measurement or assessment in the field is expensive, time-consuming, and often inaccurate. One of the main advantages of using remote sensing data to estimate vertical forest structure is the ability to obtain accurate data for larger areas in a more time- and cost-efficient manner. Temporal changes are also important for estimating and analysing tree heights, and in many countries, national airborne laser scanning (ALS) surveys have been conducted either only once or at specific, longer intervals, whereas aerial surveys are more often arranged in cycles with shorter intervals. In this study, we reviewed all freely available national airborne remote sensing data describing three-dimensional forest structures in Slovenia and compared them with traditional field measurements in an area dominated by uneven-aged forests. The comparison of ALS and digital aerial photogrammetry (DAP) data revealed that freely available national ALS data provide better estimates of dominant forest heights, vertical structural diversity, and their changes compared to cyclic DAP data, but they are still useful due to their temporally dense data. Up-to-date data are very important for forest management and the study of forest resilience and resistance to disturbance. Based on field measurements (2013 and 2023) and all remote sensing data, dominant and maximum heights are statistically significantly higher in uneven-aged forests than in mature, even-aged forests. Canopy height diversity (CHD) information, derived from lidar ALS and DAP data, has also proven to be suitable for distinguishing between even-aged and uneven-aged forests. The CHDALS 2023 was 1.64, and the CHDCAS 2022 was 1.38 in uneven-aged stands, which were statistically significantly higher than in even-aged forest stands.
Keywords: uneven-aged forest, freely available national airborne remote sensing data, lidar, aerial photography, dominant height, canopy height diversity, periodic annual increment
Published in DiRROS: 09.01.2025; Views: 301; Downloads: 194
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Keywords: nacionalna gozdna inventura, gozdovi, gozdarstvo, odmrla lesna, biomasa, temeljnica, površina gozda, lesna zaloga, vzorčne ploskve, poročila
Published in DiRROS: 26.11.2024; Views: 391; Downloads: 521
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Abstract: V Sloveniji spremljamo stanje in razvoj gozdov na nacionalni ravni z Nacionalno gozdno inventuro (NGI). V prispevku smo analizirali pestrost pojavljanja drevesnih in grmovnih vrst ter preverili pojavljanje tujerodnih drevesnih vrst v slovenskih gozdovih. Glede na literaturo v Sloveniji uspeva 71 avtohtonih drevesnih vrst, od katerih jih je bilo 60 zaznanih med merskimi drevesi na mreži ploskev NGI gostote 2 x 2 km. Največje povprečno število merskih dreves in grmov, kot tudi Shannon-Wienerjev indeks vrstne pestrosti, smo ugotovili na vzorčnih ploskvah v Predalpski ekološki regiji (H' = 0,85), najmanjše pa v Alpski ekološki regiji (H' = 0,58). Lesna zaloga merskih dreves in grmov v celotni Sloveniji dosega 330,7 m3/ha ± 2,1 %, lesna zaloga podmerskih dreves in grmov (prsni premer do 10 cm) pa 9,7 m3/ha ± 5,9 %. V lesni zalogi merskih drevesnih in grmovnih vrst prevladujeta bukev (Fagus sylvatica) (31,9 %) in smreka (Picea abies) (28,2 %), med merskimi grmovnimi vrstami je največ navadne leske (Corylus avellana) (85,0 %). Na ploskvah NGI je bilo zabeleženih 10 različnih tujerodnih drevesnih vrst na 138 ploskvah, največkrat so bile popisane v Submediteranski in Predpanonski ekološki regiji. V lesni zalogi tujerodnih drevesnih vrst prevladuje robinija (Robinia pseudoacacia). V lesni zalogi podmerskega drevja z 32,4 % prevladuje bukev, več kot 10,0 % lesne zaloge prispevata še navadna smreka in mali jesen (Fraxinus ornus). V lesni zalogi popisanih podmerskih grmovnih vrst prevladuje leska z 78,3 %, več kot 2 % dosegajo še rumeni dren (Cornus mas), navadni srobot (Clematis vitalba) in črni bezeg (Sambucus nigra). Predstavljeni rezultati kažejo, da je kombinacija panelnega sistema, večjega števila vzorčnih ploskev (3027) in izboljšanega šifranta omogočila prvo celostno objektivno ovrednotenje pestrosti pojavljanja drevesnih in grmovnih vrst ter prisotnosti tujerodnih vrst v slovenskih gozdovih.
Keywords: nacionalna gozdna inventura, Slovenija, vrstna pestrost, drevesne vrste, grmovne vrste, tujerodne vrste, lesna zaloga
Published in DiRROS: 29.10.2024; Views: 891; Downloads: 1337
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Abstract: In uneven-aged forests, trees of different diameters, heights, and ages are located in a small area, which is due to the felling of individual trees or groups of trees, as well as small-scale natural disturbances. In this article, we present an objective method for classifying forest stands into even- and uneven-aged stands based on freely available low-resolution (with an average recording density of 5 points/m2) national lidar data. The canopy closure, dominant height, and canopy height diversity from the canopy height model and the voxels derived from lidar data were used to classify the forest stands. Both approaches for determining forest structural diversity (canopy height diversity—CHDCHM and CHDV) yielded similar results, namely two clusters of even- and uneven-aged stands, although the differences in vertical diversity between even- and uneven-aged stands were greater when using CHM. The first analysis, using CHM for the CHD assessment, estimated the uneven-aged forest area as 49.3%, whereas the second analysis using voxels estimated it as 34.3%. We concluded that in areas with low laser scanner density, CHM analysis is a more appropriate method for assessing forest stand height heterogeneity. The advantage of detecting uneven-aged structures with voxels is that we were able to detect shade-tolerant species of varying age classes beneath a dense canopy of mature, dominant trees. The CHDCHM values were estimated to be 1.83 and 1.86 for uneven-aged forests, whereas they were 1.57 and 1.58 for mature even-aged forests. The CHDV values were estimated as 1.50 and 1.62 for uneven-aged forests, while they were 1.33 and 1.48 for mature even-aged forests. The classification of stands based on lidar data was validated with data from measurements on permanent sample plots. Statistically significantly lower average values of the homogeneity index and higher values of the Shannon–Wiener index from field measurements confirm the success of the classification of stands based on lidar data as uneven-aged forests.
Keywords: uneven-aged forest, lidar data, canopy height model, voxels, canopy height diversity
Published in DiRROS: 13.08.2024; Views: 549; Downloads: 843
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