DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 3-4/2013 str. 40     <-- 40 -->        PDF

In the summer of 2009, in each structural type 15 plots of 500 m2 (20 m x 25 m) were established using the stratified random sampling method. In total 90 plots were established. In site type A the slopes of the areas where the plots were established range from 0 to 10 %. In site type B the slopes of the plots range from 20 to 50 %. However the dominant slopes are between 30 and 40 %.
In each plot, all J. excelsa regeneration plants – seedlings (trees with height up to 1.3 m) were graded in 2 categories. The first category represents the seedlings that have been established and grow under the facilitation of other plants (F plants). These are seedlings found under closed canopy or the edge of the canopy (up to 30 cm out of the projection of the canopy edge) of a single plant or a group of plants of J. excelsa or other species. The second category refers to the rest regeneration plants of the plot. These seedlings are considered to grow under light, in canopy gaps without significant side shade (G plants) (see Milios et al. 2007).
Moreover in each plot under a single tree or a group of J. excelsa trees (chosen using the simple random sampling method) the depth of the ground organic layer was measured. The ground organic layer includes the plant litter and the surface soil layer where the inorganic soil is intermingled with organic matter. In the structural types STADS, STADD, STBDS and STBDD the depth of the ground organic layer was measured under a single tree or a group of J. excelsa trees where the LF appears in the height of 50–60 cm above the ground. Finally in each plot the soil depth was determined through a soil profile.
Experimental design – Plan pokusa
The scheme of data collection regarding the regeneration density is considered to apply to the following experimental designs: The sample plot of 500 m2 was considered as the experimental unit in both designs.
Design 1: It refers to J. excelsa stands or groups where in a significant number of trees the height of LF appears in 50–60 cm above the ground (structural types: STADS, STADD, STBDS and STBDD). The design includes two factors between and one factor within the experimental units. The between factors are: 1) site type (FST) consisting of two levels: site type A (FSTA) and site type B (FSTB), and 2) J. excelsa formation density (FD) consisting of two levels: sparce formations (FDS) and dense formations (FDD). The within factor is the J. excelsa regeneration category (R) with two levels: seedlings that have been established and growing under the facilitation of other plants (F) and seedlings that have been established and growing under light, in canopy gaps without significant side shade (G).
According to the above information, the STADD structural type is a combination of level FSTA of the factor FST and level FDD of the factor FD. The STADS is the combination of level FSTA of the factor FST and level FDS of the factor FD. The STBDD structural type is a combination of level FSTB of the factor FST and level FDD of the factor FD. Furthermore, the STBDS is the combination of level FSTB of the factor FST and level FDS of the factor FD.
Design 2: It refers to J. excelsa stands or groups of site type B (structural types: STBDS, STBDD, STBDSGR and STBDDGR). The design includes two factors between and one factor within the experimental units. The between factors are: 1) J. excelsa formation density (FD) consisting of two levels: sparce formations (FDS) and dense formations (FDD) and 2) living foliage appearance (FLF) with two levels: formations where the LF of trees appears at ground level (GR) and formations where in a significant number of trees the LF appears in the height of 50–60 cm above the ground (H). The within factor is the J. excelsa regeneration category (R) with two levels: seedlings that have been established and growing under the facilitation of other plants (F) and seedlings that have been established and growing under light, in canopy gaps without significant side shade (G).
According to Design 2 the STBDD structural type is a combination of level FDD of the factor FD and level H of the factor FLF. The STBDS structural type is a combination of level FDS of the factor FD and level H of the factor FLF. The STBDDGR structural type is a combination of level FDD of the factor FD and level GR of the factor FLF, while the STBDSGR structural type is a combination of level FDS of the factor FD and level GR of the factor FLF.
Data analyses – Analiza podataka
The seedling density data from the two experimental designs was analyzed using the Mann-Whitney and Wilcoxon tests (Ho 2006). The General Linear Models (GLM) were not used since the normality of distributions was not supported.
Consequently in Design 1 the interaction of the 2nd order of the factors FST, FD and R was analyzed. On the other hand, in Design 2 the interaction of the 2nd order of the factors FD, FLF and R was analyzed. In the non-parametric tests, the level of significance (p-value) was calculated with the Monte Carlo simulation method (Takeuchi et al. 2007).
The means of the depth of the ground organic layer under a single tree or a group of J. excelsa trees in site types: a) STADS + STADD, b) STBDS + STBDD and c) STBDSGR + STBDDGR were compared using the Duncan test (Freund and Wilson 2003).
Results
Rezultati
Only two J. excelsa regeneration plants of the F category were found under the canopy of other species individuals, the rest F plants grew under the facilitation of J. excelsa trees or groups of trees.