The effects of tree species richness and management type on diameter growth of Kazdağı fir (Abies nordmanniana subsp. equi-trojani))

Although tree species richness generally has positive effects on stand productivity and stand density generally has negative effects, various studies show that our current knowledge of stands' richness-productivity relationships is insufficient for forests consisting of different tree species. In this study, it was observed whether tree species diversity and stand type affect stand productivity when Oriental beech (Fagus orientalis L.) joins to the mixture in Kazdağı fir (Abies nordmanniana subsp. equi-trojani) forests. For this purpose, four different stands were selected; a) uneven-aged fir forest, b) fir even-aged forest, c) mixed fir-beech uneven-aged forest, and d) mixed fir-beech even-aged forest. The variation of diameter increment was investigated in these four different stand types. This thesis study was carried out within the boundaries of Sinop Regional Directorate of Forestry, Ayancık Forest Management Directorate, Akgöl Forestry Operation Unit. Fifteen plots of 20x20 m were taken from each of the four different stands studied. "Random Effects Model" regression analysis was used to determine the effects of tree species diversity and stand density on 5-year diameter increase. It has been determined that "Species Diversity" and stand density have a significant effect on 5-year diameter increase. There is an inverse relationship between species diversity and diameter increase. There is also an inverse relationship between stand density and diameter increase. The increase in stand density caused a decrease in the 5-year diameter increase. When the effects of the stand type on the 5-year diameter increase were compared, it was determined that the stand type had a significant effect on the 5-year diameter increase (p<0,05). The findings of this study will improve our understanding of species diversity controls in fir and beech stands. KEYWORDS: Beech, fir, productivity, richness, yield