Ecological Assessment of Swiss and Danish Thinning Methods on Brutia Pine (Pinus Brutia Ten.) Reforestation in Neka Area- Mazadaran Province)

The objective of this study was ecological assessment of the Danish and Swiss thining methods in 20-years old reforestations of Brutia Pine (Pinus brutia Ten.). This research conducted under completely randomized block design (CRBD) with three replication and three treatments (Swiss and Danish thinning methods and control); a total of 9 plots each 2000 m2 (40 x 50 m). The quantitative and qualitative parameters of trees were measured by full callipering in each plot. In order to investigate the species diversity of plants and the natural regeneration in each plot, three micro samle plots of 49 m2 were randomly selected. Sampling of soil invertebrates was performed from a depth of 0 to 10 cm in the center of each micro sample plots. The parameters were measured in the years of 2013 (before thinning) and 2018 (five years after thinning). This study showed the mean diameter at breast height (dbh) and mean height of Brutia trees and the whole stands, as well as, simpson plant diversity and soil invertebrates' diversity between treatments were not statistically significant in 2018. Mean dbh of the whole stand and Pine trees were accounted to 17.02 cm and 22.74 cm in Danish method, 16.94 cm and 21.71 cm in Swiss method and 15.59 cm and 19.53 cm in the control plot. Mean height of the whole stand and Pine trees from Danish and swiss methods to the control plot were accounted to 11.13 m and 13.19 m, 10.88 m and 12.68 m and 11.44 m and 13.58 m, respectively. The average species diversity of Shannon plants in the field of Danish thinning was significantly higher than the Swiss method and the control area. Also the Simpson plant diversity was higher in the Danish method, followed by the control and the Swiss method, while the soil invertebrates’ diversity was higher in the Swiss method followed by the control and Danish method. Also the results of this research showed that the quality of the Brutain Pine and the whole stand in the thinned treatments were better than that of the control plot in 2018 (ρ=0.05). This research emphasizes the need for thinning operations in the forest plantations.  Over all this research suggests application of the Danish method in Brutia Pine plantations in terms of increasing the quantitative and qualitative characteristics of trees, along with the increasing of plant diversity