Gorgan University Of Agricultural Sciences and Natural Resources Journal of Wood and Forest Science and Technology 2322-2077 29 2 2022 06 22 Meta-analysis of snag volume variable in Hyrcanian forests Meta-analysis of snag volume variable in Hyrcanian forests 121 136 6157 10.22069/jwfst.2022.20263.1971 FA Kiomars Sefidi University Of Mohaghegh Ardabili Mohammad Esmaeilpour Ahar Faculty of Agriculture and Natural Resources, University of Tabriz, Ahar, Iran Journal Article 2022 06 03 Background and Objectives: In close-to-nature silviculture, snag and/or dead trees have great importance because of their essential role in the conservation of biodiversity in forest ecosystems. In this regard, estimating the volume of snag trees in old-growth forests can be a guide for its maintenance in managed forests. One of the most important questions in recent years is how much snag trees can be recommended for retention in the managed natural forests. Related resources show different results for this variable. Therefore, in a meta-analysis, studies in Hyrcanian forests were collected and analyzed. This is the first meta-analysis study of an important structural factor in close-to-nature silviculture, namely the snag volume in the Hyrcanian forests. Materials and Methods: This study includes design and search strategy, articles collection and data extraction, inclusion and exclusion criteria, and finally statistical analysis of extracted data. Snag and/or dead tree related literature was searched in national and international database, including SID, Science Direct, Web of Science, Scopus, Google Scholar and IranDoc until May 2022. In this study, after a detailed literature review, finally, the data (i.e., mean, standard deviation and sample size) of 16 original studies related to the snag tree volumes in Hyrcanian forests were used, which has 163 samples with a total area of 92.44 hectares. After data extraction, Cochran's Q test and I2 index were used to assess the heterogeneity of the studies and choose the appropriate model for analysis. To find the source of heterogeneity, a subgroup analysis was performed based on geographical areas (province) and tree composition. In this study, Egger's and Beggs' tests were employed to investigate the publication bias. Data analysis was performed with Comprehensive meta-analysis ver. 3.7. Results: The average snag volume was estimated at 35.293 m3/h (95% confidence interval: 24.769 - 45.817) for Hyrcanian forests according to the significance of the Cochrane Q test (P=0.0001) and I2 index (99.735) based on the random effects model. Subgroup analysis showed that the highest snag volume was estimated based on a random model in the Golestan province forests at 50.520 m3/h (95% confidence interval: 45.669 - 55.372). In this study, the publication bias test was not significant (p-value for Egger's and Beggs' tests were 0.28 and 0.24, respectively). Conclusion: The average volume of snag trees in the Hyrcanian forests was estimated to be "average". Thus, the maintenance of at least 35 m3/h of snag tree in Hyrcanian-managed forests can be a guarantee for the preservation of the biological functions of these trees. Background and Objectives: In close-to-nature silviculture, snag and/or dead trees have great importance because of their essential role in the conservation of biodiversity in forest ecosystems. In this regard, estimating the volume of snag trees in old-growth forests can be a guide for its maintenance in managed forests. One of the most important questions in recent years is how much snag trees can be recommended for retention in the managed natural forests. Related resources show different results for this variable. Therefore, in a meta-analysis, studies in Hyrcanian forests were collected and analyzed. This is the first meta-analysis study of an important structural factor in close-to-nature silviculture, namely the snag volume in the Hyrcanian forests. Materials and Methods: This study includes design and search strategy, articles collection and data extraction, inclusion and exclusion criteria, and finally statistical analysis of extracted data. Snag and/or dead tree related literature was searched in national and international database, including SID, Science Direct, Web of Science, Scopus, Google Scholar and IranDoc until May 2022. In this study, after a detailed literature review, finally, the data (i.e., mean, standard deviation and sample size) of 16 original studies related to the snag tree volumes in Hyrcanian forests were used, which has 163 samples with a total area of 92.44 hectares. After data extraction, Cochran's Q test and I2 index were used to assess the heterogeneity of the studies and choose the appropriate model for analysis. To find the source of heterogeneity, a subgroup analysis was performed based on geographical areas (province) and tree composition. In this study, Egger's and Beggs' tests were employed to investigate the publication bias. Data analysis was performed with Comprehensive meta-analysis ver. 3.7. Results: The average snag volume was estimated at 35.293 m3/h (95% confidence interval: 24.769 - 45.817) for Hyrcanian forests according to the significance of the Cochrane Q test (P=0.0001) and I2 index (99.735) based on the random effects model. Subgroup analysis showed that the highest snag volume was estimated based on a random model in the Golestan province forests at 50.520 m3/h (95% confidence interval: 45.669 - 55.372). In this study, the publication bias test was not significant (p-value for Egger's and Beggs' tests were 0.28 and 0.24, respectively). Conclusion: The average volume of snag trees in the Hyrcanian forests was estimated to be "average". Thus, the maintenance of at least 35 m3/h of snag tree in Hyrcanian-managed forests can be a guarantee for the preservation of the biological functions of these trees.

https://jwfst.gau.ac.ir/article_6157_d1034150f1fbea10f7082de0080cfe85.pdf