The Change of Stand Structure in Uludağ Fir (Abies nordmanniana subsp. bornmülleriana MATTF.) Forests Along an Altitudinal Gradient

Abstract

In this study carried out in mixed Uludağ fir forests in Bartın-Arıt district the change of stand structuredepending on altitude was investigated. For this reason, experimental plots were established in 5 differentaltitude ranges (1,000-1,100 m, 1,100-1,200 m, 1,200-1,300 m, 1,300-1,400 m, 1,400-1,500 m, and1,500-1,600 m) and changes of stand structure were determined in respect to the number of trees as wellas volume and mixture rate of fir in the experimental plots. According to the results of this research work,the number of individuals per hectares has decreased depending on increasing altitude. However, thereare significant differences at the P<0.01 level according to the results of ANOVA in respect to thenumber of trees per hectare of both Uludag fir (F=85.68***) and oriental beech (F=73.45***). Later on,the Duncan test was applied to the number of trees per hectare in different altitude ranges. According tothe results of Duncan test, three different groups have determined the changes of the number of trees perhectare depending on the altitude ranges at the P<0.01 significance level. The mean DBH of Uludag firchanged between 53.2 cm and 28.5cm depending on altitude range. On the other hand the mean DBH oforiental beech changed between 48.3 cm and 23.6 cm in relation to the increase of altitude. Furthermoreaccording to the results of regression analyses, there is a significant negative correlation (R2 = -0.96)between the change of DBH of Uludag fir and altitude ranges. Similarly, there is a significant negativecorrelation (R2 = -0.94) between the change of DBH of oriental beech and altitude ranges. The meanheight (H) of Uludag fir changed between 21.6 m and 11.4 m depending on altitude ranges respectively.On the other hand the mean height of oriental beech changed between 19.4 m and 10.7 m depending onthe increase of altitude. Furthermore according to the results of regression analyses, there is a significantnegative correlation (R2 = -0.95) between the change of height of Uludag fir and altitude ranges. Similarly,there is a significant negative correlation (R2 = -0.93) between the change of height of oriental beech andaltitude ranges. The mixture rates (%) of Uludag fir are increased depending on altitude meaning that theUludag fir is the more dominant tree species in respect to mixture rates than the oriental beech. Thevolume (m3/ha) of both tree species have decreased depending on increased altitude. However, there aresignificant differences at the P<0.01 level according to the results of ANOVA in respect to the volumesper hectare of both Uludag fir (F=21.82***) and oriental beech (F=17.63***). Furthermore, the Duncantest was applied to the volumes (m3/ha) in different altitude ranges. According to the results of Duncantest, three different groups have determined the changes of volumes (m3/ha) depending on the altituderanges at the P<0.01 significance level.