Uporabljivost ultrazvučnog visinomjera/daljinomjera Vertex pri izmjeri strukture brdske bukove sastojine primjenom uzoraka promjenjive vjerojatnosti selekcije ocijenjena je na temelju rezultata procjene strukturnih elemenata i vremena, odnosno novčanih sredstava utrošenih za izmjeru. Istraživanje je provedeno u čistoj bukovoj sastojini na području Uprave šuma Podružnice Karlovac, Šumariji Slunj u gospodarskoj jedinici Mašvina. Na kvadratnoj mreži 100x100 metara postavljeno je 25 stajališta na kojima je provedena izmjera prsnih promjera Bitterlichovom metodom (PPS). Za odabir stabala korišten je Bitterlichov štapić (faktor temeljnice 1) i Bitterlichov zrcalni relaskop (faktori temeljnice 1, 2 i 4). Provjera udaljenosti rubnih stabala provodila se Vertexom, a uz faktore temeljnice 2 i 4 i mjernom vrpcom. Kao referentna metoda postavljena je kružna ploha radijusa 20 m.
Na temelju izmjera različitim metodama izračunate su vrijednosti strukturnih elemenata (broj stabala, temeljnica i volumen) za pojedine plohe i sastojinu u cjelini. Analizom varijance ponovljenih mjerenja nije utvrđena statistički značajna razlika u prosječnim vrijednostima strukturnih elemenata između različitih metoda izmjere uz razinu značajnosti 0,05.
Za odabrane PPS metode provedena je studija vremena i procjena troškova inventure. Uz veće faktore temeljnice znatno se smanjuje vrijeme i trošak inventure (i do 71 %). Ukupno vrijeme i troškovi inventure primjenom faktora temeljnice 2 uz korištenje Vertexa su 20 % manji, a kod faktora temeljnice 4 su 12 % manji nego kada se udaljenost rubnih stabala provjerava mjernom vrpcom.
Ovim istraživanjem potvrđeno je da se troškovi izmjere PPS metodama mogu smanjiti primjenom Vertexa, a jednako tako i primjenom odgovarajućih faktora temeljnice, kao i organizacijom rada (prijevoz ekipa).Applicability of ultrasonic telemeter Vertex in inventory of montane beech stand was estimated. Evaluation was based on estimates of structure elements from Bitterlich variable plot sampling, time consumption and costs.
Research was carried out in pure beech stand located near Slunj, in management unit "Mašvina", Forest administration Karlovac, Croatia. Systematic sample of 25 plots was laid on a grid 100 x 100 m. Breast height diameters (DBH) and heights of trees over 10 cm DBH were measured using Variable plot sampling with different metric basal area factors (BAF). Sample trees were selected by Bitterlich stick (BAF 1) and Spiegelrelaskop (BAFs 1, 2 and 4). Distance of borderline trees was checked by Vertex telemeter and measurement tape (BAF 2 and 4). In total, seven combinations of Bitterlich plots (methods) were carried out (Table 1), and circular 20 m radius plots on the same standpoints were set as a reference method.
Diameter distributions estimated from BAFs 1, 2, and 4 were compared to distribution from 20 m radius plots by chi-square test, difference of 0.05 being considered statistically significant. Distributions from BAF 2 and 4 were found to be statistically different (Table 2), with difference mostly coming from number of trees DBHs 10 to 20 cm (Fig. 2).
Number of stems, basal area and volume were calculated for each method per each plot and whole stand (Table 4). All estimates were compared by repeated measures ANOVA with significance level 0,05. No statistically significant differences were found between estimates of N, G and V coming from different methods (Table 5).
Time study and estimation of costs were carried out for measurement methods. Bigger BAFs were found to considerably decrease time (Figure 4) and costs (Table 6), even up to 71 % (BAF 4 vs. BAF 1). Using Vertex instead of measurement tape for checking borderline trees reduced time and costs by 12 % (BAF 4) and 20 % (BAF 2). By economically organizing transport of field crews (two crews using the same vehicle) time and costs were reduced by 8 %.
This research confirmed that cost of forest stand inventory using variable plot sampling can be reduced by use of Vertex telemeter, as well as by choice of appropriate BAFs and economical transport of the field crews
