فصلنامه تحقیقات جنگل و صنوبر ایران
سال بیست و هشتم شماره 1 (پیاپی 79، بهار 1399)

In continuous cover forestry, the evaluation of forest structure by sampling plots is an important source of information for monitoring biodiversity and resistance criteria in forest ecosystems. Therefore, a precise and accurate sampling design to estimate the structural attributes is required. This study aimed to investigate the impact of plot area on variability and estimates of 1) traditional structural attributes including basal area, density and volume of living trees, and 2) unconventional structural attributes including the number of large trees, total deadwood volume, and the number of large deadwood elements. For this purpose, a 16-ha permanent research plot was divided into 256 0.0625-ha plots, in which all information on living trees and deadwoods was collected. Then, the traditional and unconventional structural attributes were calculated for all sample plots of different sizes (0.0625, 0.125, 0.25, 0.375, 0.5625, 0.75, and 1 ha), followed by calculating the coefficient of variation for each attribute. The results showed that the variability of the structural attributes decreased with increasing plot area. The coefficient of variation on unconventional structural attributes is generally higher than traditional attributes. By calculating the minimal number of plots within a 20% mean error, it was found that the small plots (0.026 and 0.125 ha) are more appropriate for estimating the structural attributes including basal area, density, the volume of living trees, and the number of large trees. Moreover, large plots (0.5625, 0.75, and 1 ha) are more effective to estimate the structural attributes including total deadwood volume and the number of large deadwood elements.

As part of project of identification and introducing old trees of Iran, this study was conducted to identify the old trees of the Mazandaran province and their ecological characteristics. Based on comprehensive field survey, 182 old trees were identified and recorded. Thirty three trees and shrub species were identified, among them chestnut-leaved oak (Quercus castaneifolia C. A. Mey.) with 30 trees was the most frequent species. Also, Siberian elm (Zelkova carpinifolia (Pall.) Dipp.) with 29 trees and plane tree (Platanus orientalis L.) with 21 trees, followed by wild pear (Pyrus Boissieriana Buhse), ironwood (Parrotia persica (DC.) C. A. Mey.), false walnut (Pterocarya fraxinifolia (Lam.) Spach), olive (Olea europaea L.), silk tree (Albizia julibrissin Durazz.) were the recorded species. The species of Quercus castaneifolia C. A. Mey. as the highest diameter and longest tree (60.4 m) in Iran was identified and its information was recorded. The long-lived trees were generally in sea side to 3000 m altitude. The most distribution was found in none slope and aspects (flat). Also the old trees had the most frequency in 400> m class. The highest mean diameter were in 400-1600 m and the highest crown area recorded at the slope range of 0 to 60%. The oldest tree in the province was estimated to be an 850-900 years old plane in Kinj, followed by an individual yew (Taxus baccata L.) of 400-450 years old in Gazo of Savadkouh, a juniper (Juniperus excels M. B.) with 850-950 years old in Babol, a Quercus castaneifolia with 550-600 years old in Bandpey of Babol, and a maple tree (Acer velutinum L.) of 650-700 years old in Tonekabon. The sites embracing the old trees included Sordar, Javaherdeh in Ramsar, Hassanabad in Chaloos, Kordmir of Chahardangeh-Sari, and Nour forest park, which should be specifically protected.

A set of phonological, vegetative and morphological data of eight clones of Populus nigra L. were collected and recorded on 9-year-old trees in the Alborz Research Station in Karaj during 2010 to 2019. The phenology results of poplar clones showed that the leaves were opened earlier in P.n.62/127 in mid-March and opened later in P.n.56/72 in mid-April than the other clones. The flowers were opened earlier in P.n.62/127 in early Marchand opened later in P.n.56/72 in early April than the other clones. Also, seed ripening and dispersal in P.n.62/149 began annually earlier than other female clones in late April. Full leaves fall were earlier in P.n.56/72 in early December and later in P.n.62/127 in late December than other clones. The shortest length of the growth period was in P.n.56/72 and longest was in P.n.62/127. The results of the vegetative characteristics analysis showed that there is the highest average volume growth increment in P.n.62/154 with 40.72 m3/ha/y. Also, study of morphological characterization showed that the trunk shape of all clones is straight except P.n.62/149 and their crown form are closed to somewhat open. There are maximum percentage of dry matter, leaf area and angle between the main vein and the second vein in P.n.62/191. Basic leaf base trait of clones is partially wedge-shaped to round wedge. There is considerable variation among the studied clones in terms of leaf and bud morphological characteristics.

To study the effect of canopy gaps on aboveground plant composition and permanent soil seed bank in mixed and pure stands of oriental beech (Fagus orientalis lipsky), artificial and natural canopy gaps with different sizes considered at the Hajikola-Tirankli forest plan, Sari. All canopy gaps were grouped in different classes including small (less than 150 m2), medium (150-350 m2), and large (350-500 m2) sizes. The variation of aboveground vegetation composition in response to the gap characteristics was surveyed by Detrended correspondence analysis (DCA), and similarity of the aboveground vegetation with soil seed bank in the two depths was compared using the Jaccard similarity index. In total, 71 plant species were identified in the region, from which 26 belonged to above ground, 24 species to soil seed banks and 21 species were similar for both sections. Species such as Carex sylvatica Huds. Carex riparia Curtis, Rubus hyrcanus Juz. and Hypericum androsaemum L. were dominant in the soil seed bank. In addition, results showed that plant composition in vegetation differed with a soil seed bank. The Jaccard similarity index indicated that the similarity rate of aboveground vegetation and the corresponding seed banks under large gaps was higher than those of small/medium gaps and control plots. Moreover, the similarity rate between soil seed bank in the upper layer (0-5 cm) with above-ground vegetation composition was higher compared with the deeper layer (5-10 cm). These differences, especially with regard to the variation of similarity between the soil seed bank and vegetation across a range of gap sizes calls for increased attention to management and rehabilitation measures that are appropriate for each of the microhabitats created by the canopy gaps.

Increasing the expansion of deforestation in forested areas and increasing soil erosion and sediment in downstream of watersheds there necessitates forest development in those areas. So, before any forestry project, site selection of prone areas and land capability evaluation should be considered. The aim of this research was to study forest expansion capability using multi-criteria evaluation method in Saqezchichay watershed located in Namin, Ardabil province. First, land use maps for years 1989 and 2019 were prepared using the Support Vector Machine algorithm (Kappa coefficient = 0.91 and overall accuracy = 95.5%). Then, the degraded forestlands were identified and introduced as priority sites for reforestation. In the next step, 12 criteria were weighted using Analytical Network Process and were transformed to the same scale using the Fuzzy method. Finally, all layers were overlaid by the WLC method and resulted in a forestry capability map. Results showed that 28.81 percent of this area have a high or very high potential for reforestation. Moreover, precipitation, temperature, and soil depth were recognized as the most important criteria. The integrated map of the current forest area and the potential map revealed 41.94 percent of the current forest area was in an area with high or very high potential class, whereas 41.1 percent was located in an area with a moderate potential class for forest expansion. Based on the results, the study area has the capability for forest expansion. In addition, the ANP Fuzzy approach was able to identify suitable areas that are appropriate for forest expansion.

The role of forest engineering is crucial for restoring and reclaiming of skid trails, one of these being to reduce sediment yields along the trails. This study aimed to measure sediment yield in the skid trails covered by different organic mulches and to compare it with an untreated trail and control plot (i.e., undisturbed forest). This research was conducted for 13 months (from September 2017 to October 2018) in the Namkhaneh district, Kheiroud forest, Nowshahr under the natural rainfall condition. Six-square-meter plots were used in three replications to determine the amount of sediment. Three natural mulch treatments were used in this study, including sawdust, leaf litter, and straw, and there were mulched at three different rates (based on material weight). The highest and lowest amount of sediment was obtained in the untreated skid trail and undisturbed forest, respectively. Our results demonstrated that the application of sawdust, straw, and leaf litter mulches reduced the sediment yield by 13.1, 10.2, and 7.3 times compared to the untreated trail, respectively. Overall, it can be concluded that the application of mulches, especially sawdust, has a significant impact on sediment reduction.

Forest soil characteristics can be strongly influenced by tree species and seasons. A few studies have been carried on the effect of single trees in different seasons on soil characteristics. Therefore, in this study, the effect of Parrotia persica (DC.) C. A. Mey., Ulmus minor Miller, Quercus castaneifolia C. A. Mey. and Populus caspica Bornm. species on some of chemical and microbial features of topsoil were considered in the fall (November 2016) and summer (August 2018) seasons in plain forest of Noor city (Mazandaran province, northern Iran). Five replication of each species was regarded; soil samples were taken from 15 cm of depth under tree canopy cover from four sides of the tree trunk and kept at 4° C for experimentation. Afterward, some chemical characteristics [i.e. organic carbon (C), total nitrogen (N) and C/N ratio], and microbial indices [i.e., basal respiration, microbial biomass carbon (MBC) and nitrogen (MBN) and their ratio] were measured and calculated. Two-way ANOVA and the Duncan multiple tests were employed to analyzing statistical characteristics. Results showed that seasonal changes, in spite of significant differences in microbial indices, had no effect on chemical characteristics. The highest MBC, MBC/MBN ratio, and organic carbon content were observed in the soil of Q. castaneifolia, while MBN and total N content were higher in soil of P. caspica. The findings indicated that P. caspica due to having the highest MBN, total N, and lowest C/N ratio, creates better conditions for microbial activities than other species and can be considered to improve soil quality in the region.

The purpose of this study was to compare the status of the Hyrcanian forests research in the level of the country, organization, researcher, and journal. The Scientometrics approach is used for this research. The population of this study consists of 376 Hyrcanian forests indexed in the Web of Science. The study was conducted during 2010-2019. HistCite software was used for further analysis and VOSviewer software has been used to drawing collaboration networks. Findings showed that Iran was in the first place with 335 documents and a very high degree of RSI, compared to the rest of the countries. Of the top 10 most productive organizations in this field, nine were Iranian-affiliated, and another was the University of Tuscia, Italy. The University of Tehran ranked first with 104 documents. Meghdad Jourgholami from the University of Tehran with 20 documents was the most productive researcher in this field. Among the top 10 most productive researchers were two from Italy and the rest were from Iran. The Journal of Forestry Research topped the list with 21 articles in the field. In general, the results indicate Iran's good position in this field, which is natural given the high share of Hyrcanian forests in Iran. Also, publications and citations in this field have been positive growth throughout the years under study.