Download
1 / 21
210 likes | 349 Views
Comparison of structural attributes between old-growth and adjacent managed forests in Bosnia and Herzegovina. Sr dj an Keren Renzo Motta Dusan Rozenbergar Zoran Govedar Jurij Diaci. Birmensdorf , 201 4. Introduction.
E N D
Comparison of structural attributes between old-growth and adjacent managed forests in Bosnia and Herzegovina Srdjan Keren Renzo Motta Dusan Rozenbergar Zoran Govedar Jurij Diaci Birmensdorf, 2014
Introduction • Mixed forests composed of Fagussylvatica L., Abies alba Mill and Piceaabies L.H. Karst represent ecologically and economically most important forest category in Bosnia and Herzegovina. • Of special interest to scientific community are also three wide-known mixed old-growth forests (OGF): Perucica, Lom and Janj.
Introduction • An important aspect of sustainability verification is a comparison of managed forests with unmanaged references. • Specific objectives of this study were to test for differences in terms of: tree density, dbh distribution shapes, tree species composition, mean diameters, BA, growing stock and CWD.
Materials and methods • The research was carried out in old-growth forests Janj and Lom and ten adjacent managed stands (by five on both sites), which are located on mountainous massifs of central and western Bosnia and Herzegovina.
Measurements Regular 100x100 m grid of sampling plots was superimposed (total 80 plots in OG forests and 120 plots in managed forests). Following inventories were carried out: in circular plots (r = 12 m) species dbh for all living trees above 7,5 cm were measured. Heights of living trees were measured for a sample of 100 trees for each species (spruce, fir, and beech). In smaller inner plots (r = 5 m) species and height of regeneration individuals from 10 cm height to 7,5 cm dbh were tallied.
Measurements CWD measurements were carried out on two 50 m line intersect oriented northward (the first) and eastward (the second) from the centre of the sampling point.
Results Tree densities (N/ha) Independent t-tests involving total means of number of trees indicated significant differences between pairs OGF Janj - MF Janj (p = 0.0000) and OGF Lom - MF Lom (p = 0.0010), but also between MF Janj and MF Lom (p = 0.0190)
Diameter distributions (sensu Janowiak et al., 2008) The best-fitting multiple regression models for dbh frequency distributions
Mean diameters (cm) Independent t-tests indicated significant differences in mean diameters at p ≤ 0.05 between all possible pairs: OGF Janj vs. MF Janj, OGF Lom vs. MF Lom, OGF Janj vs. OGF Lom, and MF Janj vs. MF Lom.
Basal area (BA) and growing stock (GS) in studied forests Results of t-tests showed no significant difference in basal areas between MF Lom and OGF Lom, while between other pairs difference was statistically significant at p ≤ 0.05.
Tree species composition above 7.5 cm dbh OGF Janj was similar to MF Janj regarding basal area composition, but very different regarding tree number composition. OGF Lom and MF Lom differred considerably upon both criteria.
Considering composition based on tree number non-significant results were yielded for pairs OGF Janjvs. OGF Lomand MF Janjvs. MF Lom, while significant difference at p ≤ 0.05 was indicated for two pairs: OGF Janj vs. MF Janj χ2 = 26.77 OGF Lomvs. MF Lom χ2 = 16.81 Considering composition based on basal area similar outcomes of testing were obtained as shown above
Replacement patterns and neighborhood effects In all studied forests overall 14 transition matrices were calculated. One example from OGF Janj (poles to upper story) is shown here: Transition probability matrices indicated domination of beech regeneration under mature trees in OGF Janj and both managed forests, whereas beech poles had potentially greatest chance to reach the upperstory in both old-growth forests. Silver fir poles were given rather high chances to replace mature trees in the upperstorey of managed forests. On the other hand, despite significant shares of Norway spruce in the upperstorey of all studied forests, regeneration and poles of this species were given low chances to replace mature trees in both old-growth and managed forests in the near future.
Coarse woody debris (m3/ha) Independent t-tests indicated significant differences in CWD amounts between pairs: OGF Janj vs. MF Janj (p = 0.0000) and OGF Lom vs. MF Lom (p = 0.0000), whereas no significant difference was found between two OG forests nor between two managed forests.
CONCLUSIONS Smallest dbh class contained more trees in managed forests, whereas in OG forests there was incomparably more large living trees and snags above 50 cm dbh. Nevertheless, dbh distributions in managed and OG forests Janj and Lom exhibited shapes considered to provide demographic equilibrium; High growing stocks with dominant conifers in the upperstorey did not cause deviations from sustainable dbh distributions; however, the issue of regulating tree species composition came to surface. Neither low-intensity disturbance in OG forests nor single tree selection system in managed forests led to sufficient recruitment of spruce in understorey and midllestorey despite significant presence of this species in the upperstorey.
4.Contrary to highly stocked OG forests, small canopy openingsin managed forests made through single tree selection cutting provided small but constant share of maple. 5.If the share of spruce and maple is to be increased in these managed forests in the future, slight change in silvicultural approach may be necessary.
