Iranian journal of Forest
Year:2010 | Volume:2 | Issue:1|Papers Count:11

Tree felling is the most important component among tree harvesting consisting of cutting, limbing, bucking and topping. Bucking is the operation resulting in a felled tree being cut into logs. Motor-manual tree bucking in hardwood forest is the effective and important components that will result in the greatest value being recovered from the tree for a specific end use. This research was carried out in two compartments of Namkhaneh district, in Kheyrud Forest to assess the efficiency of bucking operations. This research was aimed to time study of tree bucking operation in short and long log methods, estimate the productivity and costs of chainsaw, and develop a regression model. Factors affecting the bucking time regression model were DBH and tree length in short log and DBH in long log method. The hourly production of bucking in short log method with and without delay time was 35.57 m3/h and 56.86 m3/h, respectively. However, in long log method, the hourly productions with and without delay time were 79.85 m3/h and 134.12 m3/h, respectively. Bucking productivity in those methods were increased related to DBH as power. The unit cost of bucking operation in short and long log method were decreased as power when DBH increased. Total bucking cycle time with delay averaged 6.77 and 3.44 minutes in short and long log method, respectively.

This study assessed the effect of import tariff of wood products upon forest conservation. We especially noted that per capita gross domestic product, crude oil price, currency exchange rate, import tariff, imported and exported value of wood products as well as their volume, domestic wood production price and conservation unit were the most important determinants of illegal wood logging as a forest conservation indicator. To achieve more delicate assessment some factors including imported wood products such as price, volume and tariff was categorized to three classes; raw wood (RW), intermediate and final wood products (IWP, FWP). Followed by, multivariable regression analysis (MRA) was applied to model the determinants of illegal wood logging in the period 1995-2005. Finally, the effects of above-mentioned factors on illegal wood logging were determined using least square methods. According to the estimated model, increasing in volume of IWP and decreasing in tariff of RW caused the illegal wood logging to decrease. Volume of IWP was appeared to have the most important impact on illegal wood logging. Average Smuggling elasticity showed that one percent change in tariff of RW and volume of IWP can cause 0.2% and 0.25% change in illegal wood logging, respectively. These low elasticity’s show that other variables like entrance barriers as in the case of skinned log import affected raw wood import and therefore had more influence upon illegal wood logging. We observed that reduction of raw wood tariff can not be merely effective on illegal wood logging.

The increasing concerns about global warming and climate change have caused a special attention to soil and its potential to sequestrate the carbon permanently. Afforestation in barren lands with optimal management can have the noticeable effect to increase the soil carbon sequestration in the way that the soil of forest ecosystem in balance with tree and plant coverage would be the main store of organic carbon. This research was done by factorial design in Pinus eldarica, Robinia Pseudoacacia stands and the surrounding barren land (as blank) in Chitgar forest park of Tehran. The amounts of soil carbon sequestration were measured. The relation between some physical and chemical factors of soil and soil organic carbon were also investigated. The results indicated that soil carbon sequestration of R.Pseudoacacia (78.19 mg/ha) was significantly (p<0.01) more than P.eldarica (57 mg/ha) and barren land (10.8 mg/ha). Their economic values for mentioned species were computed 2.790 and 3.741 million dollar’s respectively. The soil organic carbon in depth of 0-15cm of planted stands was more than depth of 15-30cm, in contrast to barren land. The result of stepwise regression showed that the percentages of clay and Nitrogen were respectively the most important factors for soil organic carbon. Totally it could be said that the process of carbon sequestration is important for water and soil quality, fertility increment, Hydrology system of soil improvement and also preventing the erosion and wasting the nutrients. Therefore the forest ecosystem should be managed in order to increase the carbon sequestration potential.

Tang Ban watershed basin is located in Behbahan city, the southeast of khuzistan province. Phyto geographically, this basin is located between Irano-Turanian (subregion of Zagrosian forests) and sudanian regions. Thereby it has the specific conditions of both. Field studies and plant sample collections were carried out in 2006 and 2007. The objective of this study was to investigate and study the flora and plant cover. In addition, endemic and rare plants were identified and also the interactions of vegetative regions were investigated. Over all, 202 species from 45 families were identified, out of which 16 and 4 species were the endemic and rare plants, respectively. The results showed that 34.7 and 6.61 percent of identified plants belonged to the Irano-Turanian and sudanian regions respectively, and 8.7 percent belonged to the common vegetative elements of Irano-Turanian and Sudanian regions. Because of the distance between the study area and Mediterranean region, the influence of the Mediterranean elements in this study was 5.1 percent. The common elements of Irano-Turanian and Mediterranean included 17.35 percent of identified plants. Although, the basin is covered by forest types, which Phanerophytes included 7.9 percent of life forms. Therophytes and Chamephytes with 58.9 and 6.0 had the highest and lowest percentage of plant forms, respectively.

In order to analysis the importance value and spatial pattern of woody species, Sardabrrod forests located in Chalous were studied. With considering the study areas covers 306.2 ha, and 84 sample plots with 400m2 (20 m × 20 m) were established by a random systematic method. All trees larger than 7.5cm in diameter at breast height on plots were recorded for analysing to spatial pattern. Seven ecological units were indentified using Pc-Ordination software. After calculating the relative frequency, density, abundance and mean importance value (IV) index, Carpinus betulus had the most importance value compared to the other woody species. Based on the importance values, Parrotia persica, Fagus orientalis, Acer insign and Acer compester had the most importance values, respectively. Thus, the spatial pattern of these species was statistically analysed. Variance to mean ratio (general procedure) showed that Parrotia persica have higher spatial index than other dominant woody species. Carpinus betulus, Fagus orientalis and Acer insigne had next priorities. Clumped pattern were confirmed for all mentioned species considering spatial index > 1 and these results coincide with Green and Morisita standardized indices.

In Iran Eucalyptus (E. camaldulensis Dehnh) has been planted across a wide rang of environmental conditions. Despite of expantion of E. camaldulensis planting in wide rang of Iran, no study has been done about its water requirement. The objective of this study were to determine the evapotranspiration (Et), production function (PF) and water use efficiency (WUE) of 3-year old  plants under lysimetery conditions and different regimes of irrigation. The trials were carried out in Yazd Shahidsadoge control desert research station under drainage lysimeters with 121 cm diameter and 160 cm depth. The treatments were 100% (well watered),70% (medium stress) and 40% (high stress) field capacity (FC), With three replicate under complete  randomize design. The results showed that evapotranspiration dependend on soil water content and sufficient soil moisture (of the field capacity) can increase crop coefficient (Kc) up to 1.7. Total dry mass (stems, leaves and roots) also increases with increasing soil moisture. The higher the soil moisture, the higher the evapotranspiration rate and plant production function can be improved. Water use efficiency (dry mass/t) improved with increasing drought stress, so that treatments of 70% and 40% of field capacity showed significant difference with 100% of field capacity (P<0.05). However, the increase of drought stress from 70% to 40% of field capacity, showed no significant effect on Water use efficiency. The highest water use efficiency belonged to 40% field capacity treatment with 2.5 g dry weight in kg water consumed in transpiration.

Renewal of volume using inventory sampling known as 3P replaced the one hundred percent renewal in northern forests from 2000 up to 2001 to decrease field works and costs and enhance the forest interprise. In this method after choosing sample trees among marked trees, its field operations starts with measuring the volume of industrial and fire wood of sample trees for each authorizer cut and the obtained coefficients were generalized to all trees of same cut authorization. To assess and compare the precision of 3P method with 100% volume renewal a study is conducted in restored and semi-degraded forests in Babolkenar forestation plan district 2 part 10 on two species: Parotia persica and Carpinus betulus. After generalization of industrial coefficient of 3P method in total volume, industrial volume was 1.8% less than 100% industrial volume in Parotia persica and in Carpinus betulus after generalization of industrial coefficient 3p in total volume, industrial volume had 3.9% difference to 100% industrial volume. In this method, we saved both the time spent measuring sample trees of 3P (field work) compared to 100% volume renewal and the cost of operation (about 33%) and the time for calculation of volume. However, writing volume renewal (staff work) is also saved about 23%. It could be expected that following the technical principles in cutting, measuring, computation and also improving volume tables of 3P method gives logical and acceptable results.

Managers in conservation biology are continually faced with the dilemma of needing to demonstrate which areas should receive conservation priority based on their diversity of species. Darenasab (Hashtadpahloo) forest catchment with dominant oak species in centeral Zagross of Iran was chosen as a study area. Field methods that sample both trees and herbs strata simultaneously, (modified multi-scale Whittaker plots) was used to make species-area curves. Three species-area, species-log (area) and log (species)-log (area) curve models were constructed for four vegetation types using modified multi-scale Whittaker plots data, based on comparisons of estimated and observed species in each vegetation types. Species - log (area) curve corrected by Jaccard’s coefficient had the highest accuracies and were chosen to compare plant diversity in different vegetation types. The index of vegetation types contribution to regional diversity for conservation priority, based on ranking of the mean number of species per plots, slopes of the species - log (area) curves, mean of Jaccard’s coefficient, mean number of unique species, and the number of threatened species in each vegetation types were calculated. This composite index may provide an appropriate approach to rank vegetation types for high conservation value.