Iranian Journal of Forest and Poplar Research
Year:2016 | Volume:23 | Issue:4|Papers Count:22

Variations in forest vegetation are effected by several factors, one of the most important of which being the crown canopy. This study aims to survey the effect of close and open crown canopy on the herbaceous diversity in Nav-e Asalem forests in Guilan province. To this aim, 15 canopy gaps of small (100-200 m2), medium (200-300 m2) and large (300-400 m2) sizes were selected with 5 replications each. Moreover, control plots of the same sizes were selected under the tree canopy. Along small and large diagonals in each gap microplots of 2×2 m each were measured in a randomized systematic design. The percentage of herbaceous cover was estimated using Domin scale. To assess plant diversity in each plot, diversity indices of Simpson, Shannon-Wiener, Smith-Wilson Evenness Index and herbaceous richness were derived. Results showed that increasing the gaps area resulted in a significant increase of diversity and richness. Furthermore, no significant difference was observed between diversity and richness indices between small area gaps and control areas.

In this study, 50 hectare of mixed yew stand was structurally investigated across Gazoo forest, a study area between 1100-1300 m a.s.l located 50 km from Zirab town in Mazandaran province. All yew individuals above 7.5 cm D.B.H were full calipered by measuring their height and DBH. A transect of 20×100 m was selected to study the stand vertical structure. Within the transect, DBH, height, crown diameter and distance from origin of each tree were measured. The diameter distribution curve of yew stand resembled an even-aged stand, which was yet due to a long-term decrease of regeneration which resulted in absence of young yew individuals. The stand structure was two-story (three-story in thinning area), with Fagus orientalis and Carpinus betulus trees covering the over story. Maximum height and DBH of yew trees were 30 and 2 m, respectively. Volume of standing tree was 593 m3 ha-1, which accounted for 17% of the total volume percentage within the stand.

This study was designed to evaluate the presence of some heavy metals in dust as well as their influences on soil, leaves and twigs of Brant's oak (Quercus brantii Lindl.) at a study site located in Meleh-Siah, Ilam province. For two groups intact and declined trees, we measured four elements including Pb, Zn, Ni and Cd in two different time spots (April and September 2013) during the growth period corresponding to the dust events. Sampling results showed an increase in the amount of all elements except for zinc in the sub-canopy soil for both groups of trees. By showing a significant increase (p<0.05) during early spring to late summer, all four elements were shown to be absorbed by both declining and intact oak trees. At twigs samples of intact trees Pb, Ni and Cd elements showed increased concentration at the end of growth period while similar significant increases wasn't noticed in twigs of declined trees. Also, apart from Zn content of leaves at second inventory phase, there was no significant difference between declined and intact trees whit respect to studied elements. This study concludes that the heavy metals in dust are highly able to be absorbed by leaf and root. Furthermore, these might be amongst the reasons which decrease the resilience of oak trees against stress factors such as climate change, drought, pest infestations, and overgrazing.

Soil pollution caused by cadmium has recently become a major concern. Phytoremediation is a convenient, cost-effective and eco-friendly method for remediation of polluted environments. In this study, the effect of soil texture (clay, clay-loam and silty- clay- loam) on the cadmium accumulation by leaves, stems, and roots of black locust (Robinia pseoudoacacia L.), round-leaf ash (Fraxinus rotundifolia Miller) and Arizona cypress (Cupressus arizonica Greene) was surveyed. The study was carried out in a complete random-based factorial design with four factors (plant species, plant organs, soil texture and cadmium concentration level). At the end of the growing season, the cadmium concentration in the organs was measured. Analysis of variance showed significant deference (P<0.01) of cadmium absorption amongst the species. Moreover, the three species showed significantly different absorption rate amongst different organs. In addition, different cadmium concentrations (1000, 2000, 3000 and 4000 mg/kg) applied on the species revealed significantly different absorptions. Soil texture was concluded to have no significant effect on cadmium absorption. Furthermore, R. pseoudoacacia revealed the highest absorption level which was attributed to its genetic specifications.

Density (i.e. number of trees per unit area) is one of the important structural attributes of forest stands which is appropriate to understand forest dynamics. The k-Nearest Neighbour (k-NN) method is a distance sampling method which is commonly used to estimate quantitative attributes in forest inventories. In this study, the k-NN method with five strategies of Nearest Individual (NI), Nearest Neighbour (NN), Random Pairs (RP), Point-Centered Quarter (PCQ), and Quartered Neighbour (QN) was used to estimate the density of wild pistachio (Pistacia atlantica Desf.) in Zagros woodlands. A natural stand of 45 ha was selected in Bane Research Site, and was fully callipered to derive the true density. The spatial distribution of trees was clustered (R=0.79 and z=-12.38) with a true density of 19.44 trees per ha. While applying the k-NN method, different strategies as well ask ranging between 2 and 10 were tested across 46 sample points in a 100100× m2 sampling grid. The results showed that all strategies except PCQ significantly estimated the density at a=0.05. Furthermore, the number of k and the strategy of k-tree selection affected the accuracy and precision of k-NN results, since NI in k=4, NN in k=7, RP and QN in k=2 estimated the density with the least error (RMSE and Bias). In conclusion, the optimum k-NN method with appropriate k and strategy could estimate the density of wild pistachio trees with clustered spatial distribution in an open stand in Zagros woodlands.

This study aimed at investigating a range of widely-used approaches for indirect ordination analysis of vegetation. To this aim, a black pine (Pinus nigra Arnold.) plantation (9.2 ha) located at Urmia airport was studied. Nine plots of 100 m2 each were randomly set up in 5050× m sampling grid, in which vegetation was recorded. In addition, three plots of 100 m2 with 50 meters interval were set up along transect in an adjacent meadow site as control area. We evaluated three ordination techniques (Principal Component Analysis, Detrended Correspondence Analysis, Non-Metric Multidimensional Scaling) with varying values of gradient length, Kaiser-Guttman, Broken stick, 70% of variance, eigenvalues>0.4, final stress in NMDS ordination and Procrustean analysis. Result showed that all three ordinations are able to illustrate length of environmental gradient, though Procrustean analysis of all three datasets revealed significant differences in correlation between ordination methods. DCA had eigenvalues >4.0, and the covered Kaiser-Guttman criterion with an axis. Moreover, final stress was< 10 in NMDS ordination, yet PCA covered Kaiser-Guttman and broken stick criteria at three axes. In conclusion, the most appropriate ordination methods across our test site included DCA and NMDS.

Deadwood is commonly known as an essential structural and functional element in forest communities. Thus it is important to understand its role and natural dynamics to improve the forest management strategies in both managed and unmanaged forests. This study analyzed both qualitative and quantitative characteristics of deadwoods as indicators of stand developmental stages in the unmanaged forests of Kheiroud in Mazandaran province, northern Iran. Three sample plots were established in the initial, optimal and decay stages, in which attributes such as diameter at breast height, height of all standing and dead trees as well as the decomposition stage of dead trees were recorded. Results showed differences in the amount of deadwood per ha as well as in volume, type and size of the coarse woody debris (CWD) in all the three stages. The frequency of snags was higher than logs in initial and decay stages, whereas the proportion of logs was greater than snags in the optimal stage. Moreover, maximum and minimum volume of the CWD was observed in the initial and optimal stages. Amongst the species, beech returned the highest number and volume of deadwood in all three stages. In addition, the entire deadwood showed diameter< 35 cm during the optimal stage. The majority of dead trees in the early stages were categorized as being in advanced decay or decomposition levels.

Wild pistachio (Pistachia atlantica Desf.) is one of the economically important woody species in Zagros region of Iran. Because of its economic importance, this species has an essential role in protecting soil and water resources. The possibility of seed oil extraction adds to the economic advantages of Pistacia atlantica. This study in Lordegan forests aims to determine the amount of seed production, oil percentage and chemical properties (e.g. fatty acid) to quantify the economic value of wild pistachio. Initially, 3 trees were selected in each diameter class ranging from 10 to 50 cm. The seeds of all trees were collected to measure the amount of seed and oil percentage in each diameter class. The Soxhlet analysis showed oil production of 27.16%, whereas rated 19.3% by using the mechanical analysis. Maximum oil production as measured by Soxhlet method was shown to be 32.1% for the diameter class of 45 cm. In addition, minimum production rate of 23.48% was recorded for the diameter class of 40 cm. The maximum seed oil of 24.8% was recorded by using the under pressure method in diameter class of 50 cm, while the same method resulted in the minimum oil amount of 16.85% in diameter class of 40 cm. The analysis of the samples revealed 13 fatty acids, including 7 unsaturated (Oleic, Iso-sic-oleic, Linoleic, Linolenic, Palmitoleic, Gadoleic, Behenic) and four saturated (Palmitic, Stearic, Miristic, Arachidonic) in oil extracted form Pistacia atlantica seeds.

Field-based volume renewal methods were investigated for two tree species of oriental beech (Fagus orientalis Lipsky) and Caucasian alder (Alnus subcordata C. A. Mey.) by means of 3P and fully revised volume across district No.10 of Sardabrood forest management plan. Field inventory included: 1) A full calipering based on 558 sampled trees (516 oriental beech and 42 Caucasian alder) and 2) 3P-based volume renewal using 96 sampled trees (81 oriental beech and 15 Caucasian alder). Compared to the total 613.89 m3 marked oriental beech wood, the renewal resulted in 489.65 m3 full calipering and 488.83 m3 3p method. In case of Caucasian alder, the total marked wood volume of 79.68 m3 was renewed to 88.62 m3 in full calipering and 82.87 m3 by 3Pmethod. The results indicated a reduction in volume by 10.82 m3 (Oriental beech) and 5.75 m3 (Caucasian alder) compared to full calipering method. The results obtained by t-test also revealed no significant difference between renewed volume by either of the methods for both species. Therefore, the 3P-derived values are concluded to be of high accuracy for volume renewal for practical implementations.

Assessment of research performance of scientific board in research institutes is considered as a key topic to monitor the process of knowledge production. This research was aimed to assess the performance of scientific board to adopt appropriate strategies to increase the quantitative and qualitative level of scientific products in the field of natural resources research. The DEA method was applied to assess the performance of research units. In total 872 scientific outputs of the scientific board in 11 administrative units and 27 provincial units of RIFR were investigated in a time span between 2007 and 2010. Our results showed that the average technical efficiency was lower than 0.623, while scale efficiency was relatively high. During the period of the study, research divisions of biotechnology, medicinal plants, gene bank, wood and paper, rangeland and forest showed the highest levels of technical efficiency, whereas other research divisions revealed a lower level of technical performance. The results also indicated a positive relationship between academic ranks and research productivity. By assuming constant and variable return to scale, comparing the average scale and management efficiencies of each research units showed a lesser scale efficiency than management efficiency for 28 research units during the study period. Therefore, scale efficiency was concluded to have the highest impact on technical inefficiency based on the assumption of constant return to scale. That is, the importance of optimal production scale is not taken into account by the majority of research units.

Iranian mountain ash (Sorbus persica Hedl.) is a valuable shrub species which also frequently occurs in the stands located in Isfahan province in central Zagros. Mountain ash seedling typically begins to germinate after winter. We investigated its seed germination by means of a completely randomized design with 15 treatments including the pre-chill, warm stratification then pre-chill, gibberellin, gibberellin then pre-chill, and control treatments, each in four replications. The highest germination rate (97.50%) was observed for two-week warm stratification (25°C) and the 4-month cold stratification (1-4°C) treatments. The success of cold stratification treatment suggests that Iranian mountain ash is associated with physiological dormancy. Since the pre-chilled treatment for 120 days at 1-4°C completely broke the seed dormancy, the seed dormancy was concluded to be substantially deep. Reducing the initial seed moisture content (17.3%) to 7% did not affect its survival. Moreover, seed viability was maintained following a 600-day storage at -20°C, suggesting an orthodox behavior of the seeds. In conclusion, the use of appropriate treatment resulted in a very high germination rate.

We modeled the distribution of oriental beech (Fagus orientalis Lipsky) stands to determine optimum ecological amplitude range along riparian forests of Ramsar Safaroud riverside in Mazandaran province. Data were collected on transects which were perpendicular to the water flow on both river sides. Each transect was 200 m in length, with a 200 m distance between transects. On each transect five 400 m2 quadrats were laid in 50 m intervals. At each sampling location the number of beech individuals with a diameter at breast height (DBH)>7.5 cm were recorded. In addition three soil samples per plot were taken from the upper 30 cm depth. Totally 44 transects and 220 quadrats were sampled. An extended HOF model implemented in eHOF package in R was applied to assess the response of beech to soil variables, and the corrected Akaike' s information criterion (AICc) was used for model selection based on models associated with the lowest AICc values. The results showed that only 27.5% of the models obtained a symmetric normal response curve (model IV), whereas 72.5% of models showed linear and asymmetric (i.e. I to V) curves. However, the VI and VII models were observed in none of the results. We assessed the HOF models to be of high potentials to be further employed in similarly-structured riparian forests.

We assessed the accuracy of two sampling methods by comparing their estimations to Full Calipering (FC). The two methods included 1000-m2 systematic random (SR) sampling plots designed within a 150×200 m grid, and a cluster sampling (CS) method with 7500-m2 clusters each embracing 4 plots of 1875 m2 each. Full calipering was performed in 4 parcels of 116 ha each. The inventory resulted in total 40239 trees measured in 40 SR plots (sampling intensity=9.7%) as well as 56 plots within 14 clusters of in CS approach (sampling intensity=3.44%). Results from CS method were associated with optimum accuracy for tree density and forest structure. The CS method returned results closer to the FC when estimating the beech- and hornbeam-specific no. of trees per ha and their distribution in diameter classes and in parcels. The Maximum trees diameter of 165, 110 and 125 cm were recorded for FC, SR and CS approaches, respectively. Conclusively, this study suggests a forest type and species-specific stratification to be performed prior to each parcel-based inventory. In addition, sample size should be determined on a forest type-specific basis, ideally distributed within a CS design with 1900 to 2000-m2 plot sizes.

Poplars are associated with variations in the yield which are influenced by their variable requirements. Due to restrictions in water availability across the country as caused by long-lasting drought periods, the amount and duration of irrigation has been continuously changed. Thus, the qualitative and quantitative growth properties of poplar cultivars is necessary be quantified in association with different irrigation regimes. Furthermore, seedlings and mature trees have different requirements. Therefore, we carried out a survey in Karaj to study 9 species of selected cultivars in a split plot design with 3 replications which we treated with two 4-day and 8-day irrigation regimes. For each treatment, the incoming water were measured by installing WSC flume type 3 which was used to determine section levels and timing of water through the flume by using standard curves for each flume. Data analysis resulted in significant differences observed amongst diameter growth of the clones. However, height volume growth did not show any significant difference between two treatments. The 4-day treatment spent 4500 m3 year-1 water more than the 8-day treatment. The P.e.561.41 clones were strongly affected by varying amounts of water, and the volume of produced wood from 4-day treatment was substantially higher than that of 8-day treatment. The P.e.561.41, P.e.vernirubensis, P.n.62.154 and P.n.betulifolia clones were concluded to excess other investigated clones in volume, diameter and height growth.

Criteria and indicators for national park assessment are tools for supervising the stability of national parks, which yet should be include high environmental, economic and social standards. The purpose of this study is to identify and customize ecological, economical and sociopolitical criteria and indicators for sustainable management of the national parks in Iran. In this study, views from 36 environmental experts and professionals in sectors relevant to national parks management were collected in a four-step process by means of questionnaires, followed by data analysis by Delphi method applying a set of criteria and indicators of IUCN, CIFOR and other sources. The experts were asked to express their views on the importance of criteria and indicators based on Likert scale. The results were summarized, which all in all resulted in 8 criteria and 142 indices. The fourth analysis step, 100 final indices out of initial 142 were agreed on. The criteria include extent of forest resources, conservation of biological diversity, Health, vitality and integrity, productive capacity and functions, protective and environmental functions, maintenance and development of economic functions and conditions, maintenance and development of social functions and the legal and institutional frameworks. The number of indices was 67, 15, 7 and 11 for ecological, social, economic and political aspects, respectively. The results revealed the highest number of indicators to be related to ecological aspects, while the economic aspect embraced the least indicators. The results suggest the Delphi method as a useful approach to identify and localize the criteria and indicators, which enable Department of Environment to monitor the stability of ecosystems within the national parks.

Associations between plant coverage and environmental parameters help to understand the natural habitats, as well as the effective functions on growth and establishment of plant species. The Marsdenia erecta (L.) R. Br. ex DC. is one of shrub species which occurs in forests of Chaharmahal and Bakhtiari province, about which almost no report on ecological characteristics and regional distribution has been published so far. In this study, growth regions of Marsdenia erecta were initially identified following site visits and preliminary checks, based on which two habitats of Chahartagh and Dorak Anari were selected. Field sampling was accomplished by means of 35 circular plots of 1000 m2 each. In each plot, quantitative characteristics of species, including number of standing trees, average crown diameter and height were measured. In addition, a mixture soil samples were collected from the surface soil horizon, which were then analyzed in terms of chemical and physical properties such as electrical conductivity, organic carbon, lime, phosphorus, potassium, nitrogen, sand, silt and clay contents. The properties were statistically analyses on species level. Furthermore, the relationship between Marsdenia erecta distribution and soil characteristics was surveyed by principal component analysis. The results showed maximum diameter, height and canopy of Marsdenia erecta across Dorak Anari test site, whereas Chahartagh test site revealed the highest density. Quantitative results also revealed a significant difference between the measured heights of Marsdenia erecta individuals across the two test sites. However, no significant difference was observed by comparing the mean values of soil variables (acidity, organic carbon, lime, phosphorus, potassium, nitrogen, sand, silt and clay). Based upon the applied principal component analysis, soil texture was the most influential factor on distribution of Marsdenia erecta in Dorak Anari, whereas chemical variables of soil such as organic carbon, phosphorus, potassium and nitrogen were the major determinants in Chahartagh test site.