The decay time and rate determination in oriental beech (Fagus orientalis Lipsky) dead trees in Asalem forests

According to key role of dead trees in maintaining biodiversity in forest ecosystems, the awareness of the full decay dead trees times, play an important role in developing in forest protection and management program. This research was done in the Asalem forest to investigate decay dynamic of dead beech trees. A total of 90 sample cuts of dead beech stumps were randomly selected and studied. For each sample, species, diameter and degree of decay stumps were recorded. To determine the density of dead wood, cut samples were taken with the length, width and height of 5 centimeters per two perpendicular directions to the cross-section of each sample. The results showed that the decay time of 95% and 50% of the dry mass of beech stumps take a 49 and 22 years, respectively. According to the results, the decay constant of this tree species varied 0.01 to 0.07. Meanwhile in this research the total time of dead wood recruitment in the four decay class estimated totally 36 years and 2,17,12 and 6 years, respectively. Results showed there is no significant relationship between decay rate and wood extracts. According to the results in the maintaining dead wood as source of biodiversity in the forest ecosystems, the dynamic of density and volume of dead wood must be considered.
Today, the dead woods are important to the conservation of biodiversity in forest ecosystems. The importance of maintaining diversity in natural ecosystems, has led to the formation of different perspectives of the forestry projects. In the most forestry projects, especially in the conservational projects and management based on the ecological point of view, one of the main objectives of forestry plans is maintaining biological diversity in forest ecosystems (Bollmann & Müller 2012). In addition, biodiversity have been introduced as one of the main quantitative indicators to evaluate the sustainable management of forest ecosystems and high variability in forest ecosystems demonstrate the health and sustainability of ecosystems (Parviainen & Västilä 2011).
Researchers have figured out the importance of dead trees in the 1970s. Most publications have been proved its importance in biodiversity (Müller and Schnell, 2003; Schuck et al., 2004), nutrient cycling (Hafner and Groffman, 2005; Santiago and Amanda, 2005), natural regeneration (Yan et al., 2007; Sefidi et al., 2013) wildlife habitat (Harmon et al., 1986; Hunter, 1990)
Due to the change in the overall attitude toward forest management and conservation approaches, and highlights the role of forests in carbon sequestration and storage, today aware of the time of trees stay in the forest can help managers of forest in regulating forestry plans. According to dynamics of the dead trees volume in the forest ecosystem, knowledge of the changes in volume over time will be very helpful to maintain dead woods in different period’s forestry project. This research attempts to answer these questions; (1) the total decay time of a dead beech in natural conditions it takes a few years? And (2) each of the four decay classes naturally spent how many year. The answers to these questions can help us to achieve the main objective of this research provide appropriate quantitative information from the decay rates of oriental beech trees
Method and Material:This study was conducted at Asalem Forest (37°36' N, 48°52'E). The climate of the area is temperate with an annual mean temperature from 7.3 to 8.3 C and an annual mean precipitation of 586–885 mm. Forests occupy plateaus on moderately inclined slopes, largely free of rocks with limestone bedrock. Caspian forests occupy an approximate area of 2,000,000 ha being dominated by oriental beech (Fagus orientalis Lipsky). The field sampling for the case study was carried out in August 2014. A chronological sequence of samples for 0, 2, 5, 11, 15, 19 and 25 years after the harvesting period was established) Müller-Using and Bartsch, 2003). In total, 90 stumps of beech were chosen randomly for dead wood carbon measurements.
Stumps were considered as a representative of dead trees, because their mortality age was specified and it was possible to establish chornosequence plots (Harmon et al., 1986). Consequently, the sample a cube shape with 4cm length was removed from two opposite parts of a cross-section using chain saw and axe. Consequence plots were a representative of the defined decay class in this forest. Decay class of stumps was specified by visual characteristics which were observed in the structure of the bark and tissue of the wood (Albercht, 1990; Sefidi & Marvie-Mohadjer, 2010).
All statistical analyses were performed using SAS 9.3 software. Analyses of variance (ANOVA) were used to detect differences in carbon contents, C concentration and wood density of beech and hornbeam trees. Tukey’s HSD procedure was used to determine significant differences in the mean density of wood with years at α =0. 05 level.
Discussion of The findings showed that the decrease in wood density over time follows a negative exponential function. Based on the results the total decay time of the about 95% dead wood can be estimate or in other words time of reduction to estimate the 95% of the timber weight can be estimated, which is consistent with the findings of studies in northern Iran (Alidadi et al., 2015) and correspond in other similar areas in forests (Yang et al., 2010; Garrett et al., 2012; Müller & Bartsch, 2009). The results of this research in the Asalem of beech forests revealed that the time required to decay and lose 95% of the weight of a beech tree dead wood lasts about 46 years. Different results for different tree species have been reported. The decay time varies among different species. The rate of decay in trees in addition to the sites geomorphic features (Fukasawa, 2015) and environmental conditions such as climate (Russell et al., 2014) that are influential in the decay process (Dunn & Bailey, 2012) are also influenced by genetic species there.
Numerous studies have mentioned the differences between species in the rate of decay. Mackensen et al. (2003) reported differences in the rate of decay in the eucalyptus species. The tree species of E.radiata and E.elata showed differences in the rate of decomposition of the wood. In addition conifers and broadleaf tree species also varies by the chemicals properties of wood caused to e differences in the decay rates (Mackensen et al., 2003). Studies of (Palmetto & Tohi, 2014) showed differences in the decay of tree species due to differences in moisture content and density of trees. In the in Mazandaran province, Alidadi et al (2015) reported the total time of beech dead wood decay need to approximately 36 years. The contradiction in the results can be caused by different climatic condition between two study sites. In the European beech forests Müller & Bartsch (2009) reported 30 years for total decay of beech trees. Diffrences caused by environmental factors like climate and also initial density of tree species.
In addition to the aforementioned, the chemical characteristics of wood can also be more effective on the activity of microorganisms and the development of decay process.
Today, we are witnessing a change in attitude and overall approach the managers of the forestry sector to the management of our forest ecosystems. In the concepts based on the conservation of biodiversity in forest, the health of ecosystem has been an important position. T According to the findings of this research it is recommended that in the maintenance of dead trees in the forest ecosystems, beside to the volume of dead trees in the forest floor, the dynamics and volume changes over time to be considered.