FOREST RESEARCH AND DEVELOPMENT
Year:2018 | Volume:4 | Issue:1 |Papers Count:9

Root competition is one of the restricting factors of plant growth. Plants have different effects on nutrient cycling in rhizosphere during competition with respect to different root physiology and morphology, rooting systems and mixture composition. Rhizosphere is a hot spot with greatest enzyme activities that is affected mainly by roots of plants. Urease enzyme activity is an index of organic nitrogen mineralization and adjustment of nitrogen dynamics in soil. The purpose is to study the variation of absolute and specific urease activities on rhizosphere in pure and mixed planting of Quercus castaneifolia and Acer velutiniumduring different seasons. 18 rhizotrons were designed and assembled with sampling capability from different locations of rhizosphere and sequential times. Three planting treatments have five replicate while control have three. Results revealed that there were significant differences (p<0.05) of absolute and specific urease activities between different planting compositions and seasons. Absolute and specific urease activities increased 18.0% and 23.5% respectively in planting treatments from autumn 2015 to summer 2016. Mixed planting and control treatment have the most and the least absolute and specific urease activities respectively during all the studied seasons. Urease activity showed significant decrease in all treatments in winter. Mixed planting with two species have different rooting structure, created complementary ecological nests in the soil space, causing a significant increase in root biomass and urease activity on rhizosphere.

This study was carried out in Noyjian forests of Khorramabad, the destructed and less destructed stands were investigated in terms of three structural aspects: species diversity, spatial pattern and dimension variation have been compared. For this purpose, at first based on the available information and see the forest closely, two classes of crown dense 35% and more than 35% were bounded. Then in each of this part, 10 (one-acre) sample plots were taken with the similar physiographic conditions. According to the results, the diversity in these stands is low, but in general, the diversity in the less destructed stands is more than the sparse stands. Among the species diversity indices, the Margalef index shows the most difference. In relation to the pattern of distribution, the mean aspect and uniform angle indices show similar results based on random distribution of most species in both stands. According to the dominant index these species (Quercus brantii, Acer monspessulanum and pears) are dominant and other species are defeated. In general, the mean of the differentiation index shows a large difference between canopy coverings in different stands, which is more than that in sparse stands. According to the result, in general, the structure of less- destructed stands is in a more favorable position in different aspects. Since the physiographic conditions of these stands are similar, human factors can be considered as the main cause of the apparent difference between these stands. Therefore, it can be concluded that in the reduction of these factors, protection and support of destructed stands, the condition of this destructed stands will be more desirable.

Heavy metals are important environmental pollutants which cause risks for humans, plants and microorganisms by entering to the food chains. This study was done to determine the adsorption of heavy metals in soil and leaves of Persian oak trees in Aleshtar - Khorramabad highway. For this purpose, on the five transects at intervals of 0, 500 and 1000 meters on each side of the road, plots whith 10×10 meters were selected. In each plot, 30 soil samples and 30 leaf samples from all directions of crown were collected. After preparation of samples, concentration of heavy metals of lead, copper and zinc on soil and leaves were measured using atomic absorption device. The results showed that the concentration of soil heavy metals decreased with increasing distance from the road. The amount of heavy metal concentration in soil was obtauid respectively in distances 0, 500 and 1000 meters 4.6, 2.65 and 3 for lead, 56.13, 55.38 and 55.32 for zinc and 44.81, 45.34 and 38.00 mg/kg for copper. Also the amount of heavy metal concentration in leaves was obtauid respectively in distances 0, 500 and 1000 meters 0.5, 0.4 and 0.2 for lead, 34.6, 57.3 and 38.00 for zinc and 8.5, 7.3 and 8.6 mg/kg for copper. The results also showed that there is a significant negative correlation between organic matter and soil copper at the 5% level. The concentrations of heavy metals in Persian Oak leaves are lower than the standard values of the world and so this tree species can accumulate heavy metals.

Through planting, Furthermore, selecting the appropriate species as well as the ability of new ecosystems for self- regeneration and restoration are also important. Currently, approximately 50 years have passed since the beginning of semi-arid plantations around huge cities of Iran like Tehran (i.e. Sorkhe-Hesar Forest Park, located in the eastern part of the city). This study aimed to investigate the regeneration in mentioned forest stands and answer to the question, whether the investigated vegetation types and species composition, despite the arid climate and tourist traffic, are able to regenerate and the grown seedlings are capable to establish? The inventory was performed in five forest types that five sample plots of 15×15 meter were established in each one. To compare the regeneration amongst different vegetation types and amongst different species the nonparametric Kruskal-Wallis test was used. The results of this study showed that regenerations of Celtis caucasica and Cercis siliquastrum were significantly higher than those of Cupressus arizonica, Fraxinus rotundifolia and Pinus eldarica. Moreover, the highest and lowest regeneration diversity were observed in Cercis and Pinus types, respectively. The species of C. caucasica and C. siliquastrum proved to play the most important roles in regeneration of studied area. Except Amygdalus lycioides, the regeneration of all studied species were highly dependent on nurse trees and their canopy. Compared to Celtis, theregeneration of Cercis was significantly dependent on water supply.

The skid trails in this study are the routs that logging has been finished. These routes should be able to infiltrate water to decrease soil erosion and hydrological cycle disturbance. In this study four treated samples were selected in order to soil recovery. The treatments were: mulching with residual slash, diagonal water bar to skid trails axis, perpendicular water bar and finally mixed treatment (includes perpendicular water bar plus residual slash). Of course there were two control samples including soil bulk density in stand and skid trail. Totally 61 soil samples were taken before and after treatments from 0 to 10 cm depth. The results showed that, only the mixed treatment causes to decrease compaction in skid trail significantly, although there was a difference between in treatments and control samples (1.06 gr/cm3) after 18 months. Also the results show that, the recovery on ruttings was more than log trace in the middle of skid trail.

For helping to regeneration and conservation of present sites, effect of cutting type (simple and heeled) and Indole butyric acid (IBA), Naphthalene acetic acid (NAA) and 2, 4- Dichlorophenoxy acetic acid (2, 4- D) were studied on rooting of Taxus baccatacuttings. After sterilization, cuttings were treated in IBA, NAA and 2, 4- D at concentration of 0, 0.02, 0.1, 1 and 2 mg L-1 for 30 minutes. They were cultured in polythene bags and factorial arrangement based on a completely randomized design in greenhouse conditions. Data analysis and comparison of means were carried out by using two ways ANOVA and Duncan test, respectively. The results showed that the maximum percentage of survival, stem and root length of simple cuttings belonged to IBA at concentration of 2 mg L-1. IBA, NAA and 2, 4- D produced only callus in heeled cuttings at different concentration. In the simple cuttings, IBA produced only root at concentration of 1 and 2 mg L-1 but NAA produced only callus in the same concentrations. Therefore the best cuttings for T. baccata propagation are simple cuttings that they are taken from green two or three years old branches and are not yet firm. IBA at concentration of 2 mg L-1 is the best hormone for rooting of T. baccata cuttings. NAA and 2, 4- D due to having slow process in root production are not recommended for rooting of T. baccata cuttings.

The study of forest structure is one of the fundamental and necessary researches to achieve the objectives of close to nature silviculture. This research was conducted to quantify the forest stand structure in the old-growth phase in compartment 419 of Shafaroud forests in west of Guilan province. Three one-hectare areas were chosen in this phase and full calipering method used to record stand structure. In each plot, 30×30 m gird plot was laid out and diameter at breast height, distance among trees and the angle between them were measured for the closest beech to the center of plot as reference tree. Three neighbor trees closest to the reference tree were also measured. According to the results meanwhile diameter and height differentiation were 0.42 and 1.7, respectively. According to the mingling index, beech trees moderately tend to occur with other species in this phase. The old growth phase is an important and fundamental stage in the development of mixed beech stands the true recognition of which is useful in facing with new challenges in forest stand management.

Increasing the world's population and increasing demand for timber have led governments to stick to wood farming. This research was conducted on the paulownia Furtoni species cultivation in Gorgan, Tuskestan area, to study of its quantitative and qualitative features. The study area is 2.9 hectares and also is outcome of the secondary growth of prior cut trees and the age of 6 years. The diameter of all trees and height of 20 percent of them were measured. Then, for the growth calculations 12 trees were chosen and cut down as well as preparing discs and recording the qualitative characteristics all of trees. After that, volume, basal area, form factor and wood density were calculated. Using by increment information, the relationship between age and height, age and diameter and trunk analysis table were determined. Results showed that average of stand diameter, average of trees height, Basel area, density of paulownia wood and stability were 11.9 cm, 9.31 m, 16.7 m ha-1, 0.22 and 64.9 percent respectively. Determination of the qualitative and quantitative characteristics of the cultivated areas are a suitable basis for a better understanding of the impact of these areas on the evolution of ecosystems and their optimal management to provide the required wood for the region and utilize their environmental services

In 2005, there were 54 extremely large fires in the forests of Neka, Mazandaran province. This study was carried out to evaluate the effect of physiographic conditions and ecological factors on fire intensity of the above mentioned areas. For this purpose, 19 fire fires were selected from the above mentioned fires with a total area of 250 to 25000 square meters. Quantitative and qualitative data of all trees in each of the selected fire spots including tree diameter at breast height, trunk quality, crown health and the frequency of trees were investigated separately in different spots. The univariate analysis of variance showed that tree type has a significant effect on the extent of fire in the forest. The largest spots of fire were belonged to vegetative types of Hornbeam – Persian parrotia and hornbeam - oak. The CCA and DCA analysis groups hornbeam- hazel and hornbeam- oak forests in one group, beech - hornbeam in the second group and other forest types in the third group. In general, the types of oak-elm zelkova and beech-hornbeam have burned more frequently than other vegetation types during the period. In addition to the tree type, other environmental factors affecting the extent of the fire in these areas were included annual precipitation, annual average temperature and altitude.