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Forest floor fuel loads in holm oak ( Quercus ilex L.) and pubescent oak ( Quercus pubescens Willd.) forests

Šumarski list (1945), 2023-12, Vol.147 (11-12), p.513-523 [Peer Reviewed Journal]

ISSN: 0373-1332 ;EISSN: 1846-9140 ;DOI: 10.31298/sl.147.11-12.2

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  • Title:
    Forest floor fuel loads in holm oak ( Quercus ilex L.) and pubescent oak ( Quercus pubescens Willd.) forests
  • Author: Bakšić, Darko ; Bakšić, Nera
  • Is Part Of: Šumarski list (1945), 2023-12, Vol.147 (11-12), p.513-523
  • Description: The application of newer remote sensing methods, such as aerial and terrestrial lidar scanning and the use of "Structure-from-motion" (SfM) photogrammetry, complemented field data collection and enabled 3D mapping of forest fuel layers, greatly simplifying and improving their characterization. However, these methods are not suitable for quantifying forest floor characteristics. For this purpose, it is still necessary to collect data using classical field methods, determining the presence of subhorizons and their depth, while the characteristics of the forest floor: bulk density, load, carbon concentration and carbon stock are determined in the laboratory. Therefore, it is still common practice to create regression equations that allow operatives to determine the amount of available forest floor fuel and the carbon stock it contains based on the depth of the forest floor, which is an easily measurable variable, or to determine forest floor loading by subhorizon and overall. Forest floor information is used in models for predicting forest fire behavior and spread, in fire effects models, in planning and monitoring mechanical fuel reduction, in quantifying fuel consumption and smoke emissions, in quantifying carbon stocks, in describing habitat and its productivity, and in planning for preparedness. As stands of holm oak (Quercus ilex L.) and pubescent oak (Quercus pubescens Willd.) are located in the Mediterranean part of Croatia, where the risk of forest fires is the highest, and the previously published data on the forest floor are not suitable for the models, the main objectives of the research were to determine the depth, bulk density and load of individual subhorizons of the forest floor and to create regression equations that allow estimating the amount of available fuel in the forest floor based on its depth. Sampling of forest floor in holm oak stands (60, 90 and 100 years old) was conducted on the islands of Lastovo and Mljet, while sampling in pubescent oak stands (53 and 90 years old) was conducted in Dugopolje and Biograd na Moru. The amount of forest floor and OC stock in old stands of holm oak and pubescent oak is twice as small as in old stands of Aleppo pine and Dalmatian black pine. This suggests that pine stands have a significantly greater amount of potentially available fuel in the forest floor and are therefore potentially more at risk from fire, but also that they store twice as much carbon in the forest floor. In this study, for the first time in Croatia, bulk densities of individual subhorizons of the forest floor were determined for holm oak and pubescent oak and regression equations were created that allow estimating the amount of available fuel in the forest floor based on its depth per subhorizon and overall. The results of this research have practical value in simpler quantification of forest floor fuel loading, which is important for operational use of models to predict forest fire behavior and spread, but they can also be used in other models mentioned earlier. Primjena novijih metoda daljinskih istraživanja, kao što su zračno i terestričko skeniranje lidarom te primjena „Structure-from-motion“ (SfM) fotogrametrije nadopunila je terensko prikupljanje podataka i omogućila 3D kartiranje slojeva šumskih goriva čime se značajno pojednostavnila i unaprijedila njihova karakterizacija. Ove metode, međutim, nisu uporabive za kvantificiranje značajki šumske prostirke za koju se podatci i dalje trebaju prikupljati klasičnim terenskim metodama pri čemu se određuje prisutnost podhorizonata i njihova debljina dok se značajke prostirke: gustoća, količina, udjel i zaliha ugljika određuju u laboratoriju. Stoga je i dalje standardna praksa izrada regresijskih jednadžbi koje operativcima omogućuju da na temelju debljine šumske prostirke koja je lako mjerljiva varijabla, odrede količine raspoloživog goriva te zalihe ugljika u njoj, odnosno da na temelju debljina i gustoća pojedinih podhorizonata šumske prostirke odrede količine po podhorizontima i ukupno. Informacije o šumskoj prostirci koriste se u modelima za predikciju ponašanja i širenja šumskih požara, modelima učinka požara, zatim kod planiranja i praćenja mehaničke redukcije goriva, kvantificiranja potrošenog goriva i emisije dima, kvantificiranja zaliha ugljika, za opisivanje staništa i njegove produktivnosti te planiranje pripravnosti. S obzirom na to da sastojine hrasta crnike (Quercus ilex L.) i hrasta medunca (Quercus pubescens Willd.) pridolaze u mediteranskom dijelu Hrvatske gdje je opasnost od šumskih požara najveća, a podatci koji su o šumskoj prostirci do sada publicirani nisu prikladni za navedene modele glavni ciljevi istraživanja bili su utvrditi debljine, gustoće i količine pojedinih podhorizonata šumske prostirke te izraditi regresijske jednadžbe koje omogućuju procjenu količine raspoloživog goriva u šumskoj prostirci temeljem njene debljine. Uzorkovanje šumske prostirke u sastojinama hrasta crnike (starosti 60, 90 i 100 god.) obavljeno je na otocima Lastovu i Mljetu, dok je uzorkovanje u sastojinama hrasta medunca (starosti 53 i 90 god.) obavljeno u okolici Dugopolja i Biograda na Moru. Količina šumske prostirke i zaliha OC u starim sastojinama hrasta crnike i hrasta medunca dvostruko je manja u odnosu na stare sastojine alepskog bora i dalmatinskog crnog bora. Na osnovu toga može se reći da borove sastojine imaju značajno veću količinu potencijalno raspoloživog goriva u šumskoj prostirci te su zbog toga potencijalno ugroženije požarima, ali i da pohranjuju dvostruko više ugljika u šumskoj prostirci. U ovoj su studiji za sastojine hrasta crnike i hrasta medunca, po prvi puta za Hrvatsku, određene gustoće pojedinih podhorizonata šumske prostirke te su izrađene regresijske jednadžbe koje omogućuju procjenu količine raspoloživog goriva u šumskoj prostirci temeljem njene debljine po podhorizontima i ukupno. Rezultati ovog istraživanja imaju praktičnu vrijednost u jednostavnijem kvantificiranju količina goriva, što je važno u operativnoj primjeni modela za predikciju ponašanja i širenja šumskih požara, ali se mogu koristiti i u ostalim, prethodno spomenutim modelima.
  • Language: English
  • Identifier: ISSN: 0373-1332
    EISSN: 1846-9140
    DOI: 10.31298/sl.147.11-12.2
  • Source: Alma/SFX Local Collection

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