Predicting duff reduction from broadcast burning in western larch--douglas-fir stands

A r t le y , Donald K., M.S., December, 1976 Forestry Predic t ing Duff Reduction from Broadcast Burning in Western Larch —Doug lasf i r Stands ( 72 pp.) D irec to r : Robert W. Steele f / t i i Broadcast burning is one e f fe c t iv e and economically feas ib le method o f s i t e preparat ion in the western la rch ( Lar ix occiden­ t al i s , N u t t . ) -D o u g la s f i r (Pseudotsuga menziesi i var. glauca [Beissn.] Franco) fo re s t type o f northwestern Montana. However, p red ic t ive guidel ines fo r the amount o f d u f f reduct ion and min­ eral so i l exposure resu l t ing from burning are needed. The ob jec­ t i v e o f th i s study was to develop such guidel ines in the form of regression equat ions. Measurements were taken on 100 p lo ts located in each o f four previously harvested blocks (2 c learcuts and 2 shelterwoods), both before and a f t e r broadcast burning. Measurements included: du f f depth, mineral so i l exposure, downed fuel inven to r ies , fuel depth, slope, aspect, shrub inven to r ies , and preburn fuel and d u f f moisture contents. Because o f the r e la t i v e l y high moisture content o f the fu e ls , the blocks burned poor ly . Mean d u f f depth reduct ion varied from 5% to 29%, and mean mineral so i l exposure ranged from 1% to 22%. The preand post-burn measurements were used as independent var iables in a m u l t iva r ia te regression analysis on d u f f reduct ion and mineral so i l exposure. The resu l ts were inconclusive y i e l d ­ ing no strong co r re la t io ns . In a l l cases, R̂ values were too low fo r s t a t i s t i c a l l y s i g n i f i c a n t equations to be presented. However, the f e a s i b i l i t y o f th is type o f study was confirmed since the v a r ia t io n was p r im a r i ly w i th in block ra ther than be­ tween block. The f a i l u r e to explain the experienced v a r ia t io n in du f f reduct ion and mineral so i l exposure was a t t r i b u te d p r i ­ mar i ly to the high water content o f the lower h a l f o f the d u f f layer .