FOREST RESEARCH AND DEVELOPMENT
Year:2015 | Volume:1 | Issue:2 |Papers Count:7

The aim of this research was to determine an optimum sampling method based on best-fit probability distribution functions for modeling diameter distribution of Quercus persica in Dalab forests in Ilam province (western Iran). A total area of 37.2 hectares was full callipered in this study. Also, 37 rectangular 1000 m2 plots were sampled using both transect method, with a fixed length of 50 m, and systematic random sampling. Beta, Gamma, Exponential, Normal, Lognormal and Weibull probability distribution functions were fitted to diameter at breast height (DBH) distribution of the oak trees. The expected probability and probability derived from the above functions were compared using Kolmogorov-Smirnov and Anderson-Darling tests. The Kolmogorov-Smirnov analysis in census method showed that the applied probability distribution functions are incapable of fitting DBH distribution of the oak trees. Anderson-Darling test in our study showed that the Beta probability distribution function most appropriately fit with DBH distribution. In the systematic random sampling, the results of Kolmogorov-Smirnov showed that Weibull distribution is the most suitable function compared to other probability distribution functions. Though, Anderson-Darling test indicated that the Gamma, Weibull, Beta and Lognormal distributions are appropriate for fitting DBH distribution in a descending order. In transect sampling method, the results of Kolmogorov-Smirnov showed that the investigated probability distribution functions are unsuitable for fitting DBH distribution. According to Anderson-Darling test, the Gamma, Lognormal, Normal and Weibull are, respectively, the most applicable distribution functions in explaining the oak trees DBH distribution.

Air pollution severely damages tree growth and quality in urban areas due to constant absorption of pollutants by plants. It has been clearly substantiated that urban green landscapes considerably decrease environmental pollution. This study aimed to evaluate the effect of air pollution on carbohydrate and proline contents in oriental plane (Platanus orientalis L.) trees in Urmia city. For this purpose, five parks of supposedly different levels of pollution were sampled in two phases (i.e. August 2013 and May 2014). Five plane trees of relatively the same age were selected in each park. Leaf samples were collected from the outer branches of trees at three height levels. The carbohydrate and proline contents of the leaves, measured in two steps, were correlated with the level of O3, NH3, SO2, CO and PM10. The results indicated that, except for proline with NH3 in August 2013, the amounts of carbohydrates and proline were significantly (a=1%) higher with increasing air pollution.

The aim of this research is to study the influence of forest fragmentation on plant species composition and distribution in the northern aspects of Kermanshah oak forests. Three patches of oak forests with similar physiographic conditions were selected and vegetation data were sampled at 0, 25, 50, 100 and 150-meter intervals along three transects which was located in a distance of 200 m apart from each other. Cluster Analysis and Deterended Correspondence Analysis were used to categorize and investigate the trend of vegetation variation in different patches. Also, Indicator Species Analysis accompanied with Monte Carlo test was used to determine the characteristic species in the area. In this study, 113 plant species belonging to 97 genera and 27 families were identified., Asteraceae family with 21 species (18.58 percent) showed the highest number of plant species Two categories of sample plots, i.e. forest-edge (zero and 25 m) and inside-forest (50, 100 and 150 m) were separated And it was recognizes that the distance from the patch edge was the most important factor on distribution the distribution of these groups. Characteristic species of the first group are: Aegilops umbellulat, Alyssum menicoides, Anthemis hyalina, Calendula persica, Echinops kermanshahanicus, Euphorbia macroclada, Gundelia tournefortii, Lens orientalis, Onobrychis lunata, Picnomon acarna, Sysymbrium damascenum, Tragopogon longrostris, Verbascum pseudo-digitalis, Vicia assyriaca, V. narbonensis and for the second group: Alyssum marginatum, Anagalis arvensis, Galium aparine, Geranium tuberosum, Phlomis persica, Scandix pectin-veneris, Stipa barbata, Taeniatherum crinitum, Ziziphora capitata, Crataegus azaralous, and Quercus branttii.

Soil microbial respiration (SMR) and microbial biomass C (MBC) are two important site quality indices that can be used to assess the health status and rate of carbon cycling in forest ecosystems during litter decomposition processes. The purpose of this study was to determine the relationship between SMR and MBC with soil organic matter (SOM) in mixed beech forests in a permanent plot in compartment 32 in Shastkolate Forest, Golestan province, northern Iran. Using systematic random sampling, tree characteristics were recorded and soil samples collected in 90 sample plots. SMR determined using Closed-Bottle method, MBC by fumigation-extraction method and SOM by Walkley-Black method. Linear regression analysis, ANOVA and Duncan test were conducted. In this study, four forest types including pure beech, beech-hornbeam, beech-maple and mixed beech were distinguished. ANOVA tests revealed significant differences (a=5%) between SMR and MBC in pure beech stands compared to other forest types. Linear regression showed positively significant relation between SMR and MBC with SOM. Regression R2 was about 0.89 indicating the importance of SOM in enhanced microbial richness and litter decomposition rate. Soil quality and health were shown to be highest in beech-hornbeam forest type, suggesting the importance of hornbeam intermixed with beech. Silviculturists should thus acknowledge the crucial role of hornbeam in silvicultural interventions.

Due to fine-texture and moderate to high plasticity, the swelling capacity of forest soils is normally high. High volume variability, as a consequence of fluctuating soil moisture, is considered a destructive phenomenon in forest road construction. In this study, Road Packer Plus (RPP) was used as a new proxy agent to improve the swelling behavior of high plastic clay soil. To this end, compression tests, swelling and swelling pressure were conducted on the control samples and samples treated with values recommended by the manufacturer company, to understand the potential of volume changes in the treated soils. Also, to evaluate the effect of time on the performance of the RPP, swelling and swelling pressure tests were conducted on the treated samples seven and 14 days following the treatment. The results showed that the RPP agent relatively increased the maximum dry weight per unit volume and decreased swelling and swelling pressure, while treatment time could only slightly decrease the swelling capacity of the corresponding soil. With respect to soil type, adding the proposed doses and matter and curing time of treated samples of this chemical, has no significant effect on the amount soil swelling reduction. On the other hand, the closure of roads to traffic for a certain period of time following soil stabilization has no significant effect on the performance of this agent. Thus, neither the recommended dose nor the treatment processing time had significant impact on decreasing forest soil swelling potential. In conclusion, we propose to apply a similar approach on a wider array of soil types with different swelling properties.

This study aims at analyzing the understory plant species composition in relation to soil characteristics in forest plantations. For this purpose, two plantations with coniferous (Cupressus arizonica and Biota orientalis) and broad-leaved species (Fraxinus rotundifolia and Robinia pseudoacacia) along with a nearby non-forested control area were selected in Gerizeh of Sanandaj, Kurdistan province, western Iran. Random systematic method with a network dimension of 75×50 m was used for collecting soil samples and vegetation data. Canonical Correspondence Analysis (CCA) differentiated the three sites in terms of soil and vegetation parameters. Results show that the majority of samples belonging to the hardwood plantation contained high values of OC, N, Mg, sand, silt and Ca which had a positive correlation with pH. The control area, showed significant correlation with clay and bulk density. Most samples of conifer plantation, however, had the lowest OC, P, N, Mg and pH. The most abundant understory species in the broadleaf plantation were Geranium tuberosum and Vicia michuuxii, in conifer plantation Erysium billardieri and Galium vernum, and in the control area Bromus tectorum and Euphorbia denticulata.

This study aimed to evaluate the effects of forest management on soil physicochemical properties in compartments No. 10 (control) and 12 (managed) in Forest Series No. 1 in Khalil-Mahale Forest Management Planning, Behshahr. Twenty circular sample plots with an area of 1000 m2 were systematic-randomly sampled in a 100×75 m grid in both compartments. In eacha plot, five 1 m2 micro-plots were established: one in the center and four others in north-south, east-west directions at each corner. Soil samples were collected from 0-10 and 10-20 cm depths in the micro-plots. In each plot, the samples taken from the same depth range were pooled. According to our results, the values of moisture content, pH, EC, organic matter, nitrogen, phosphorus and potassium were significantly (a=5%) different in the two compartments. This study highlights the positive influence of single selection system on the physicochemical properties of forest soils.