نشریه توسعه پایدار جنگل
پیاپی 2 (تابستان 1393)

The aim was to estimate canopy storage capacity (S) and the ratio of mean evaporation rate from the wet canopy to the mean rainfall intensity, and the direct through fall coefficient (p) of a Picea abies plantation using the regression methods in Kelardasht, North of Iran. To measure gross rainfall (GR), four rain-gauges were installed in an open space adjacent to the stand and through fall (TF) was measured using the twenty rain-gauges randomly located beneath the canopy cover. Rainfall interception (I) was calculated as the difference between GR and TF. Twenty-one rainfall events were recorded with a cumulative depth of 380.1 mm. The TF and (TF:GR)% were recorded 48.8% and 39.6% of the incident rainfall on the cumulative-based, and event-based (each GR), respectively. Positive linear correlation was observed between I and GR (R= 0.92) and logarithmic correlation was established between (TF:GR)% and GR (r2= 0.43). The mean value of p, S, and estimated were found to be 0.34, 2.15 mm, and 0.43, respectively. Estimating the amount of I and its components, e.g., S, p, and , as well as transpiration of trees are required while selecting the adapted species for afforestation.

The implementation of different silvicultural systems can be effective on different characteristics of forest stands, such as stand structure and diameter distribution of trees. This study was carried out in Shafaroud forests of Gilan province of northern Iran. The objectives of this research were 1) to evaluate the suitability of different probability distribution functions, including Weibull, Beta, Gamma, Johnson, Lognormal, normal and exponential, for modeling tree distribution in diameter classes and, 2) to compare changes of diameter distributions after ten years of implementation of three different silvicultural systems. The tested systems were single-tree selection, shelterwood and strip cutting. Also, there was an untreated stand. The results of Chi-square and Kolmogorov-Smirnov tests showed that the Johnson, gamma and Lognormal models were often more flexible to fit various diameter distributions, while in any case, the beta and exponential probability distribution did not provide satisfactory descriptions of the experimental data. Other results indicated the change in the diameter distribution due to the implementation of the strip management system, a decade after timber harvest. This may mean that strip cutting can disturb the stand structure in the studied forests. Also, there were no significant changes in the diameter distributions after implementation of the other silvicultural systems.

As conservationists develop strategies for managing coarse woody debris in natural areas, information on the volume and distribution of deadwood in relatively undisturbed forests provides a valuable baseline for management goals. Hyrcanian mixed broad-leaved forests, within middle elevations of the Alborz Mountains bordering the Caspian Sea in northern Iran, experience few human disturbances and provide an ideal study site to examine woody debris in a mature forest. This study had three 1) measure volume of coarse and fine woody debris in Hyrcanian mixed hardwood forests; 2) compare density of forms of coarse woody debris (stumps, logs, and snags); and 3) correlate volume of living trees with volume of coarse woody debris. To sample the density and volume of dead wood, 15 plots of 1 ha (coarse woody debris) and 15 plots of 4 m2 (fine woody debris) were established. Coarse woody debris had an average volume of 15 m3 ha-1 and fine woody debris had an average of 10 m3 ha-1. The most common form of coarse woody debris was logs (67%) and the most frequent species was Oriental beech (Fagus orientalis) (55%). The volume of Oriental beechcoarse woody debris was not significantly correlated with the volume of living Oriental beech trees (P= 0.77); however, the volume of European hornbeam (Carpinus betulus) coarse woody debris was significantly correlated to the volume of living European hornbeam (P= 0.01). According to the results and high proportion of fine woody debris in dead wood pool, we should more consider to this component of forest stands in management of natural stands.

Mangroves are one of the most important and valuable ecosystems throughout the world. Overexploitations of mangroves by local communities due to their diverse characteristics have caused severe degradation of these ecosystems. This process can be found in mangroves of Iran, so protection and development of them is essential. In this research, we will try to indentify the best sites for development of mangroves in Holor region of Qeshm Island with an area of about 300 hectare. Firstly, the most important parameters in growth of mangroves have determined that were as follows: tidal sites, soil pH, soil electrical conductivity, soil texture, soil saturation percent, soil Sodium absorption ratio and proportion of soil Mg and Na. Sixteen soil samples were obtained using a systematic-random sampling network and their physiochemical variables were measured in laboratory. Geographical Information System and satellite images of IRS were used to provide the map layers of soil variables. Layers were overlapped and the final map of suitable sites for development of mangroves was obtained. Based on results, 13.67 ha (4.56 %) of the total area were capable for development of mangroves which could be considered in afforestation plans.

Forest roads have a significant role in sediment delivery to rivers and causes water quality reduction. This study was performed in Kohmian forest in Golestan province to estimate the amount of sediment production from forest roads using WEPP model and field measurement. The inputs of the model were precipitation, temperature, road template, soil and vegetation. To calibrate the model amount of sediment production of cut slope and roadbed were measured by sediment fences that were installed in culvert outlet. Then amount of sediment production of fill slope was measurement by rainfall simulation with plot area of 1 m2. The amount of sediment production in cut slope, fill slope and roadbed for a 546 m2 segment was 37.63 kg. The estimation of WEPP model for the segment was 35.14 kg. The results showed that the amount of sediment in model was 93% of amount of sediment from field study. Therefore, WEPP model may have high capability in estimation of sediment from forest roads in the study area. WEPP model can be used as a good tool for forest manager for risk assessment if the next studies also show the suitability of the model for Iran.

In this study, the impact of ground based skidding operation on increment growths of standing beech trees placing at alongside of skid trails investigated in Hyrcanian forests. For this purpose, four abandoned skid trails were selected which 5, 10, 15 and 20 years passed from their last skidding. Each trail divided to three segments of low, medium and high traffic with regard to distance from landing and skidder traffic intensity. The number of 72 standing beech trees were sampled alongside of trails using increment borer, and annual ring width were calculated using measuring table of LINTAB 6 with 0.01 mm accuracy. The results of ring width mean comparison between years after and before skidding operation showed about 11% decreasing in trees growth of all skid trails. Ring width in all skid trails showed significant decreasing (about 18%) in mean value of wounded trees compared with sound ones. Furthermore, trees located in high traffic segments revealed lowest mean value of increment than other segments and 33% decreasing in mean annual ring width were recorded in comparison with trees placed on low traffic segments.

Determining the fitting pattern of canopy classes in Zagros forests shows that at different times, the overall status of these forests from the destruction process and ecological sequence points of view. The aim of this research was to investigate crown canopy classes probability distribution of Quercus persica trees in Dalab forests of Ilam. For this purpose, an area of 37.2 hectares in Ilam forests was selected, and based on systematic random pattern 37 transects with fixed length were measured. Finally, the numbers of 209 trees were selected. Exponential, Gamma, Normal and Log-normal probability distribution functions were fitted to crown canopy classes. Characteristics of distribution function by using of maximum likelihood method was estimated. Actual probability and probability which derived from functions was compared using Kolmogorov-Smirnov and Anderson-Darling tests. Results of fitting tests and P-P plots showed that Normal distributions is the best probability distributions for modeling distribution in crown canopy classes of oak trees.