Comparison of tree growth and ecosystem nutrient distribution of douglas fir (Pseudotsuga menziesii (Mirb.) Franco var. viridis) and the native tree species of the western black sea region of Turkey

Experiments have been conducting since 1940?s with fast growing species in Turkey. The most intensively studied species are from USA origins. Douglas-fir (DF) (Pseudotsuga menziesii (mirb.) Franco var. viridis ) represented with adequate origins and it is pronounced as one of the most promising species in terms of industrial wood production. Marmara and western Black sea regions have the similar growing conditions with the DF?s natural distribution regions in the coast of North American Pacific.Numerous experiments, conducted with different origins of DF in the eastern- and western black sea region, has failed. Researchers attributed these failures to the variations of the sites. Experiments which are named successful contain results obtained only several years after stand initiated. One of the biggest DF experimental sites in Turkey is located in Yesilyayla region in the Melen Forest Management Chiefship of the Düzce Forest Management Directorate in the western Black Sea region. Objectives of this study; to compare the tree biomass and some of the ecosystem properties of DF and the native species of the region 16th year after stands initiated.Experimental sites are located at 900 m elevation with 1200 mm annual precipitation and an average of 10 0C annual temperature. Soil is ranged between loam and clay-loam and classified as brown forest soil. In 1988 study sites were clear-cut and cleared from weeds. Bare-root DF seedlings (2 + 0) from Washington seed origins were planted with 2.5 x 2 m spacing. Bare-root (2 + 0 ) Scotch pine (SP) (Pinus sylvestris L.) seedling with 1.25 x 2.5 m space were planted in an adjacent 18.5 ha site. In the same year eastern beech (EB) (Fagus Orientalis, Lipsky) was naturally regenerated in 95 ha forest land in another adjacent area. In some part of the natural regeneration sites a mixture of hornbeam (Carpinus betulus), chestnuts (Castane sativa), willow (Salix caprea), and poplar (Populus tremula) stand was clear-cut. Saplings from these species has vigorously grown and dominated the site as a mixture stand (MS) in 16 year.In the 16th year after stands initiated (2004) trees were cut-down with a chain saw in 4 randomly located 5 x 5 m plots in each site. Trees were separated for leaf , branch and bole. Biomass for each species was calculated from the samples. Then leaf total nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sulfur (S) and magnesium (Mg) concentrations and their amounts in hectare bases were determined. Forest floor organic matter was sampled on 5 randomly located 20 x 20 cm areas on each plot. Amount of organic matter, nutrient concentrations and total amount of nutrient organic matter contains were calculated for each stand. Soil samples were collected from randomly located 5 points at 0-10 and 10-20 cm soil depth on each plot. Soil bulk density, pH, cation exchange capacity (CEC), total carbon (C), total N, total P and K, Ca, S, Mg concentrations and amounts were determined for each experimental units. To analyze the data ANOVA were run for randomized design.In the 16th year of the experiment SP and DF biomass were similar. However, biomass of EB was 148 % higher than the average of SP and DF biomass. EB also accumulated 10 times more biomass than MS did. EB leaf has 25 and 45 % higher N concentrations than those of DF and SP, respectively. Total amount of EB nitrogen was about 4.9, 8.6, 2.6 times higher than those of DF, MS and SP, respectively. P content of EB was 5 times higher than the average of DF and MS?P contents. EB stands have 5.2, 10.6 and 2.3 times more K content than those of DF, MS and SP, respectively. Calcium had the similar trend with K. Ca content of EB was 4.5, 8 and 3 times higher than those of DF, MS and SP, respectively. There were no statistical differences among the sites for soil bulk density, CEC, pH and soil nutrient concentrations. Total ecosystem (leaf + OM +soil) N content was 1.9 times higher for EB sites than that of MS. EB sites had 1.6 and 2.5 times more ecosystem P than those of DF and MS sites.