Impact of Stand, Site and Structural Characteristics on Stand Regeneration Planning in Pedunculate Oak Forests

摘要

Starting from the fact that stand structure is significantly disturbed and from the assumption that all stands of pedunculate oak at forest level older than 100 years are potentially considered for stand regeneration, it is obvious that forest planning and management have to define their priorities on the basis of which individual, potentially mature and mature stands, will be regenerated. The general objective of this paper is to research the structure and mutual impacts of stand, site and economic factors on the elements of stand structure in a greater area of pedunculate oak forests consisting of old or potentially mature pedunculate oak stands with a disturbed structure. Based on obtained structural relations, the goal was to determine by modeling the easily obtainable elements of the variable (model), which will represent the objective criterion for stand ranking according to the regeneration priority and structural and economic requirements.The subject of the research are pedunculate oak forests in the Central Posavina region, where 37 stands, with stocking of less than 0.8, were randomly selected and divided into 3 age groups (101–120 years, 121–135 years, >135 years) in 16 management units.On a total of 146 established plots of 25 m radius, estimates and measurements were carried out of variables at the level of individual model trees (6 trees of the main species – upper storey layer – nearest to the plot centre) and of stand and site variables (2 breast-height diameters, crown diameter, tree height, base height of the crown and height of the widest part of the crown, varietal trunk structure, crown defoliation, increment core, breast-height diameter of all trees higher than 1.3 m, seedlings, potential intermediate cutting, died trees, diameters of stump of cut trees, shrub layer, microrelief, canopy, health status, litter, understorey vegetation). The estimated and measured data were processed and appropriate variables for data analysis derived. The complex potential revenue (rent) difference was defined for stand regeneration (Equation 3) as a dependent variable and objective criterion for stand ranking according to regeneration priority. By means of partial linear analyses, multivariate analysis and modeling (generalized linear modeling), mutual and complex impacts of stand, site and economic factors on elements of stand structure and potential revenue (rent) difference were investigated. Statistical analyses were performed by application of the SAS software package, whereas descriptive statistics, correlation analyses, integration of functions and development of graphical presentations were carried out by means of the STATISTICA 8.2 software package.The research included different management, stand and structural characteristics (Table 1) and determined a statistically significant mutual impact of individual variables of stand, site and economic factors on certain elements of stand structure and potential revenue (rent) difference (Table 2). Multivariate analysis revealed models of complex impacts of stand, site and economic factors on standing volume of pedunculate oak and revenue (rent) difference (Table 3). According to the obtained data, all three models are statistically significant for the estimated standing volume of pedunculate oak and also for the estimated revenue (rent) difference. The stand factors in total account for 35% variability of standing volume of pedunculate oak and for 22% variability of revenue (rent) difference. The site factors account for 39% variability of standing volume of pedunculate oak and for 34% variability of revenue (rent) difference, whereas economic factors account for even 45% variability of standing volume of pedunculate oak and for 43% variability of revenue (rent) difference. The results of the Tukey post hoc (HSD) test for statistically significant variables of multivariate analysis of the revenue (rent) difference and the standing volume of pedunculate oak (Table 4) indi