Iranian journal of Forest
Year:2013 | Volume:4 | Issue:4|Papers Count:12

Success in rehabilitation activities using particular species in desert areas rely on knowing the relationships between soil and vegetation. The study area is located in eastern part of Sarbisheh, Southern Khorasan Province. The main objective of this research was to find out the relationships between soil physical and chemical properties and succulence of natural and planted Saxaul (Haloxylon spp). After field inspection, two sites including natural and planted Saxaual (Haloxylon spp) close together were selected in which the area of each site was about 200 ha. Soil and vegetation were sampled as randomized circular sample plot or transect. In each above mentioned site, five 60 m transects were established. On the longitudinal direction of each transect six soil profiles were dug and soil samples from two different depths (0-10 cm and 10-50 cm) were taken. Also, succulence degree for the nearest Saxual shrub to transect was determined. Soil samples were physically and chemically analyzed in the laboratory for texture, bulk density, humidity, organic matter, C, N, K, Caco3, Na, EC, and pH. Results of the principal component analysis (PCA) indicated that there is a significant difference between succulence of Saxual shrubs and some of soil properties. For example, increasing organic matters and Carbon content improved the succulence and this reality is more sensible in soil surface horizons. On the other hand, increasing the content of Na, K and salinity in the soil, decreased the succulence of Saxual shrubs. Also, there was not any correlation between Caco3, pH and bulk density and succulence of Saxual shrubs. Thus, soil physical and chemical characteristics were the most important factors affecting on the succulence of Saxual shrubs.

Parrotia persica is one of the few species growing naturally in the northern forests of Iran. This specie is reproduced through asexual reproduction by coppice (shoot). This research was done to study the effects of DBH on sprouting and to select the best diameter classes regarding to asexual reproduction in experimental and educational forests of Kheyrud. Nitty nine 0.1 ha circular samples plots were randomly established. Trees were classified into three diameter classes, class1: 10-30 cm, class 2: 30-60 cm and class 3: more than 60 cm. Regeneration was separated into four classes with diameter 2-4, 4-6, 6-8, 8-10 cm. To compare the mean number of coppice in diameter classes, Analysis of Variance and Duncan tests were used with 95 percent confidence level. The results indicated that Parrotia persica trees in class 2 (30-60) had the highest number of coppices (10.8).The average number of coppices in diameter class1,2 and 3 and are 6.6, 10.8 and 6.5 per base, respectively. Healthy coppices with more diameters are better than other coppices. The number of coppices with diameter 2-4 cm is higher than other classes, and class 2 (30-60) has the maximum number of coppices. The results of ANOVA showed significant difference in the average number of coppices with diameters 2-4, 4-6, 6-8, 8-10 cm. The results of this study indicated that diameters at breast height affect the asexual reproduction of Parrotia persica. To establish asexual reproduction of this species, the diameter class 30-60 cm is more important.

The aim of this study was to investigate the capability of IRS-P6-LISS IV data for forest density mapping in the Pistachio forests. So LISS IV images (5 m), dated 2007 from Khaje Kalat (500ha) in Khorasan Razavi were analyzed. The geometric correction of images was implemented using nine control points extracted from an orthorectified image of the study area. The RMSE was less than one pixel. In addition to original bands, different synthetic bands from principal component analysis and transformation methods were created and used. The suitable bands set were selected by training areas and divergence indices. In order to assess the accuracy of classification results, a ground truth map covering 7% of the total area was prepared through fieldwork using 34 sample areas and canopy percent was estimated.Satellite data were classified by supervised classification methods including minimum distance to mean (MD), maximum likelihood (ML) and fuzzy. There were spectral interferences between medium density classes (5-10%, 10-15% and 15-20%). Therefore these classes were merged. In hard supervised classification method, the highest overall accuracy and kappa coefficient, 67% and 0.40, respectively, were obtained by ML classifier with three classes (0-5%, 5-20% and >20%). Using mode filter with a 7×7 pixel increased the accuracy up to 3%. The results of Fuzzy algorithm showed higher accuracy and kappa coefficient, 70% and 0.44, respectively. In both methods, second density class (5-20%) represented highest kappa coefficient. It could be concluded that the result of classification was not desirable regarding to low kappa, even if reaching to pretty good overall accuracy. To obtain a better result, it is suggested to use higher spectral resolution data and preparing fieldwork in smaller sample area and determining canopy percentage quantitatively.

This research was carried out to study the effects of loblolly pine (Pinus taeda) and Populus sp. plantation on some forest soil properties in Lahidjan region. The experimental design was as completely Randomized Block with three treatments (Land covers) and five replicates. For each land cover, five 500 m2 sample plots were established and five trees were randomly selected within the plots. Soil samples were taken from depth 0-20 cm around each tree. Some soil properties such as pH, organic carbon, texture, microbial respiration were analyzed. The results showed that bulk density of soils differed significantly among Pinus taeda and other trees. Poplar plantation increased significantly pH, Ca+Mg, available P and K in contrast to other tree species. Microbial respiration increased significantly under soils of native forests. It is concluded that poplar plantation could increase the soil fertility index.

Forest pollarding is one of the major uses of Northern Zagros Forest. This kind of intervention cause major changes in the structure of these forests. Trees diameter distribution is one the most important attributes of forest stands structure. In this research, probability distribution of oak species including Q. branti, Q. infectoria and Q. libani in Armardeh Forests Located in Northern Zagros was investigated for studying the role of uncontrolled pollarding on forest structure. The models were fitted to diameter observations for 1021 Q. branti, 854 Q. infectoria and 1963 Q. libani trees. Diameter distribution of trees was derived from 178 0.1 hectare sample plots. Beta, Gamma, Normal, Log-normal and Weibull probability distribution function were fitted to diameter distribution of oak trees. Actual probability and probability which derived from pdfs for diameter distribution was compared using Kolmogrov-Smironov and Chi-square tests. Fitting showed different results for different species. Since, fitted properly to all species based on both tests, Beta function was chosen as the best probability distribution function. Based on results, beta probability distribution can be used for those who want to simulate changes of pollarded forests. Beside, diameter distribution showed a critical situation for forest regeneration.

The present study was conducted to explore the effects of harvest-created gaps by single-tree selection system in beech stands in Alandan Forests-Sari on the ring widths of beech trees located at the edge of gaps and unmanaged stands eight years before and after the gap formation. For this purpose, the cores facing towards 16 gaps in four area classes as well as the adjacent un-harvested stands were extracted in diameter at breast height (DBH) and measured from 110 overstory trees. The results indicated significant differences among gap classes in terms of ring widths eight years after their creation (P<0.01). Moreover, various positions within gaps showed significant differences regarding to ring width (P<0.01). Ring widths of the studied beech trees were also different for each year within the eight year period (P<0.01). There was significant difference among gaps eight years before and after cutting (P<0.01). Gaps were also significantly different from the unmanaged stands regarding to ring width (P<0.01). In general, it can be stated that the applied single-tree selection have influenced tree ring width of beech trees eight years after gap creation.

Textures are useful indices for extracting information from aerial photographs. The main objective of this study was to map forest canopy cover density based on aerial photographs using textural indices in the middle part of Zagros forests, west of Iran. Four Arial photographs with scales and spatial resolution of 1:40000 scale and 0.56 meter respectively were used. Photos were orthorectified by Arial camera parameters, digital elevation model, fiducial marks and ground control points. Texture indices including standard deviation, mean and contrast in difference dimension of co-occurrence matrix were extracted from aerial photographs. Forest canopy cover density classification was done on original and textural bands. Useful index and co-occurrence matrix dimension were chosen using accuracy assessment by maximum likelihood algorithm. Results indicated that classification using texture indices had higher accuracy than original channel. Based on the results of this study, mean index with matrix dimension, 13×13 pixel showed the best accuracy in comparison with other indices. Overall accuracy and kappa coefficient were obtained 61.36% and 0.48, respectively using mean index. Although, the results showed an average accuracy, this method is still useful for mapping forest cover. Finally, black and white aerial photographs can be used to extract more accurate information using texture.

Distribution areas and site demands of wild cherry (Prunus avium L.) were studed in Guilan province, north of Iran. For this purpose, four catchments including Asalem, Shafaroud, Siahkal and Ghalerodkhan with high presence of wild cherry were selected and 129 0.1 ha sample plots were laid out in different combinations of land form, geographical aspect, elevation and slope gradient. Quantitative parameters of dbh and height and qualitative characteristics such as crown and stem quality of wild cherry trees were studied. Moreover, 48 soil profiles were dug and the physico-chemical properties of soil were studied. Results showed that wild cherry trees are maily distributed in individual or small groups in slops at lowlands and in middle elevations with east and north aspects, where the slope gradient is between 25 and 50%. Soil of the studied sites is deep to semi-deep with sandy clay silt to clay silt texture and with good drainage in which the pH varies between 4.3 and 7.0. The PCA analysis showed that the physical properties of soil (sand, clay and silt) have an important impact on the presence of this species. Presence of wild cherry trees in vallies and slopes facing to west and south are related to sand content of soil. The maximum measured dbh and height of trees were 101 cm and 31.3 m, respectively. The highest mean dbh was measured in the lower elevations with west aspect, whereas the highest mean height was measured in the middle elevations with north aspect. About 70% of the studied cherry trees had straigth stems with first class quality.

Afforestation with native or non-native species affects understory vegetation. These effects, besides of edaphic and climatologic factors, also depend on the species of the plants which are used. In the present study, the allelopathic effects of two species of Eucalyptus (E. camaldulensis Dehnh. and E. microtheca F.Mull.) and one species of Acacia (A. salicina Lindl) on the understory vegetation in Shiraspary region, Mamasani (Fars province) were studied. Aqueous extraction of leaves of these species was prepared in the laboratory; the effects of different densities of these extractions on the vegetative factors of Avena fatua L., Lolium perenne L., were investigated. The maximum inhibitory effect was on radical length and the minimum inhibitory effect was on seed germination. 5% density of these extractions had a stimulatory effect on the seed germination. The highest inhibitory effect on Lolium perenne was on E. camaldulensis, A. salicina, while the least inhibitory effect was on E. microtheca. The highest inhibitory effect on Avena fatua germination was on E. camaldulensis; the least inhibitory effect was after exerting A. salicina. 5% density of E. camaldulensis showed a stimulatory effect on radical growth. The 5% density of extractions increased the plumule length. The maximum inhibitory effect on the length of Lolium perenne was on A. salicina, E. camaldulensis, while the minimum inhibitory effect was on E. microtheca. The maximum inhibitory effect on length of Avena fatua was on E. camaldulensis, and the minimum inhibitory effect on radical length was on E. microtheca, A. salicina. The minimum inhibitory effect on plumule length originated from A. salicina. Compared with the control, the allelopathy effect of two Eucalyptus species was more than that of the Acacia. Both the stimulatory and inhibitory effects coincide with each other, indicating the presence of both types of allelochemicals which are capable of enhancing and suppressing at the same time. However, toxic allelochemicals are more volatile in nature than the stimulatory allelochemicals. This increased the competition ability of eucalyptuses and caused them to dominate forests and woodlands. Eucalyptus should not be cultivated in sensitive and especially arid ecosystems, so that the allelopathic effects of this species can be minimized.