A comparison of methods for estimating available understory light in forests

Abstract

Istraživanje je provedeno na području Parka prirode Medvednica na šest različitih šumskih ploha kako bi se utvrdile sličnosti i razlike između triju metoda za mjerenje svjetlosti u prizemnom sloju šumske vegetacije. Također je testirano koliko je podataka svake metode potrebno uzeti po istraživanoj plohi da bi se dobili slični rezultati. Ispitivane metode su bile mjerenje svjetlosti svjetlomjerom, hemisfernom fotografijom te priručnom metodom. Na svakoj od ploha određeno je devet točaka u pravilnoj 3x3 mreži na kojima su uzimani podaci za navedene metode. Podaci su obrađeni te je pet njihovih kombinacija provedeno kroz statističku analizu. Pokazalo se da unutar metoda ne postoje značajne razlike na razini ploha za priručnu metodu i hemisfernu fotografiju, ali razlike su postojale kod metode svjetlomjera na razini cijelog uzorka što bi se objašnjava iznimnom osjetljivošću instrumenta na okolišne uvjete. Ustanovljena je slaba korelacija između priručne metode i ostalih metoda, što se objašnjava drugačijim principom rada te mogućim neiskustvom ispitivača.The research was conducted in Medvednica Nature Park upon six different forest plots, with aim to determine comformabilities and differences between three methods for estimating understory light in forest vegetation. An additional test was made to determine the quantity of each method data, per disquisitional plot, required to obtain similar results. The examined methods were light estimating by light meter, hemispherical hotography and manual technique. Each plot was divided in nine locations, arranged in 3x3 grid, upon which data was collected. Data was processed and than five combinations have been statisticly analysed. Results have shown that there were no signifficant differences for manual technique and hemispherical photography within plots. The differences were showed for light meter which is explained by high sensitivity of the instrument. Low corelation between manual technique and other two methods was shown, which is explained by different measuring system of examined methods and possible inexperience of observer