Reliability of growing stock estimation using tariffs in case of a spruce treein forest with varied micro site conditions

V mikrorastiščno pestrem visokokraškem jelovo-bukovem gozdu smo na primeru drevesne vrste smreke ugotavljali zanesljivost ocenjevanja lesne zaloge s tarifami. Referenčne volumne dreves smo ugotovili s pomočjo švicarskih trovhodnih volumenskih funkcij. Ustrezno tarifo smo izbrali po ustaljeni metodi, na podlagi srednjega premera in srednje višine, ki smo jo odčitali iz prilagojene višinske krivulje. Razlike med tarifami posameznih vzorčnih ploskev so do 3 tarifne razrede. Odstopanje med lesno zalogo, ugotovljeno s tarifami in referenčno lesno zalogo za smrekov sestoj, je -2,8 %pri posameznih ploskvah pa so odstopanja večja, od -7,0 do 8,6 %. Dosedanje (prenizko izbrane) tarife dajo v konkretnem primeru za -18,1 % prenizko oceno lesne zaloge. Sklepamo lahko, da v primeru, če je tarifa za površino (odsek, sestoj) izbrana korektno in reprezentativno, dobimo z njo dobro oceno lesne zaloge tudi na mikrorastiščno pestri površini. Reprezentativni izbor tarife zagotovimo z meritvami na vzorčnih ploskvah, ki dobro predstavljajo površino.Reliability of growing stock estimation using tariffs in forest with varied micro site conditions was analysed in case of high karst fi r-beech forest fora spruce tree. Reference bole volumes were calculated with Swiss\u27s three parametric volume functions. Adequate tariffs were selected with standard method, using mean tree diameters and heights, which were calculated from adapted height curves. Adequate tariffs for single sampling plots are different for up to 3 tariff\u27s classes. Difference between growing stock calculated by tariffs and reference growing stock for a spruce tree\u27s stand is-2.8%, whereas for single sampling plots the differences are greater, from -7.0 to 8.6%. The hitherto used tariffs underestimated growing stock by -18.1%in the presented case. Our conclusion is that if tariff for a defi ned area (forest stand or compartment) is representative, with correct method used, the reliability of growing stock estimation is good regardless the varied micro site conditions. Representative selection of tariffs is provided for with measuration on sampling plots that well represent the defi ned area

The reliability of volume functions based on spruce tree species in Slovenia

Various volume functions used for tree volume estimations were compared by the authors. Using section measurements (Newton’s method), they calculated the real tree volumes of 88 felled spruce trees on the Pokljuka plateau. The real tree volumes were used to form regional three-entry volume functions, (two-entry) volume tables, and tariff functions. The standard error of the average tree volume estimation is the lowest for three-entry volume functions (5.0%), then for volume tables (11.7%), and the highest for tariffs (15.1%). The reliability and applicability of the developed regional and other volume functions was verified on two one-hectare research plots. It was established that by applying the adapted German volume tables, the measured spruce volumes were too high. As the volumes measured in this manner are used when determining the adapted tariffs in Slovenia, this procedure results in a tariff class of at least 5% too high tree volumes

Monitoring and analysis of spontaneous afforestation of Karst landscape in GIS environment

Članek predstavlja raziskavo zaraščanja kraške krajine. Pri analizi smo uporabili tehnike daljinskega zaznavanja, multitemporalne analize satelitskih slik v GIS okolju in statistične regresijske modele. Gozdnatost se je od leta 1935 povečala od 50,4% na 67,9%. Z regresijskim modelom smo pojasnili 71% celotne variabilnosti. Dejavniki, ki so največ prispevali k pojasnitvi zaraščanja so: nadmorska višina, razdalja do gozdnega roba, delež zaraslih površin v predhodnem obdobju, delež kmetijskih zemljišč in dve variabili, ki opisujeta intenzivnost kmetijske rabe. Če se procesi zaraščanja ne bodo bistveno spremenili, lahko do leta 2020 pričakujemo nadaljnje povečevanje gozdnatosti na 72,5%.This article presents Karst landscape spontaneous afforestation research. Remote sensing techniques, multitemporal analyses of satellite images in the GIS environment and statistical regression models were used in the research. Since 1935, the abundance of forests in this area has increased from 50.4% to 67.9%. About 71% of variability was explained with a regression model. Spontaneous afforestation is strongly influenced by the following factors: altitude, distance to the forest edge, share of afforested area in previous time periods, share of agricultural land, and two variables describing the intensity of agricultural use. Although various demographical, socio-economic and agro-structural factors were analysed in this research study, their influence on the process of spontaneous afforestation could not be established. If there are no significant changes in the processes of spontaneous afforestation in the future,forest abundance can be expected to increase to 72.5% by the year 2020

The reliability of volume functions based on spruce tree species in Slovenia

Primerjali smo različne volumenske funkcije za ocenjevanje volumnov dreves. S pomočjo sekcijskih meritev (Newtonova metoda) smo izračunali prave ocene volumnov dreves 88 posekanih smrek na Pokljuki. Te smo uporabili za izdelavo regionalnih trovhodnih volumenskih funkcij, (dvovhodnih) deblovnic in tarif. Standardna napaka ocene povprečne vrednosti volumna drevesa je najmanjša pri trovhodnih volumenskih funkcijah (5,0 %), nato pri deblovnicah (11,7 %) in največja pri tarifah (15,1 %). Zanesljivost in uporabnost izdelanih regionalnih ter drugih volumenskih funkcij smo preverili na dveh hektarskih raziskovalnih ploskvah. Ugotovili smo, da s prirejenimi nemškimi deblovnicami smrekam določimo previsoke volumne. Ker volumne iz teh deblovnic uporabljamo tudi pri določanju prirejenih tarif na Slovenskem, je s takim postopkom določen tarifni razred z vsaj za 5 % previsokimi volumni dreves.Various volume functions used for tree volume estimations were compared by the authors. Using section measurements (Newtonʼs method), they calculated the real tree volumes of 88 felled spruce trees on the Pokljuka plateau. The real tree volumes were used to form regional three-entry volume functions, (two-entry) volume tables, and tariff functions. The standard error of the average tree volume estimation is the lowest for three-entry volume functions (5.0%), then for volume tables (11.7%), and the highest for tariffs (15.1%). The reliability and applicability of the developed regional and other volume functions was verified on two one-hectare research plots. It was established that by applying the adapted German volume tables, the measured spruce volumes were too high. As the volumes measured in this manner are used when determining the adapted tariffs in Slovenia, this procedure results in a tariff class of at least 5% too high tree volumes

Use of 3d process-based model to determine forests protecting against rockfall – case study Kamniška Bistrica

This case study of the Kamniška Bistrica forest management unit presents a 3D process-based model for determining forests protecting against rockfall. Modelling was performed using the ArcGIS 9.3.1 tool; the kinetic energy of rockfalls was calculated using the Conefall friction model. The finished map of protective forests was compared with the map of protective functions of forests, made by the Slovenia Forest Service. The protective function map covers 90% of forests classified in the 1st category forests by the modelled map. Taking into consideration the entire forest area in the forest management unit, the maps match in 48% of cases. The differences appear predominantly in higher altitudes where the protective function map includes dwarf pine sites, and in lower altitudes where the map does not consider the possibility that trees can perform their protective functions where the terrain becomes level. The aim of this article is to draw attention to the possibilities of using the models as tools for determining forests protecting against rockfalls.