جستجوی مقالات مرتبط با کلیدواژه « soil bulk density » در نشریات گروه « جنگلداری »

Protection of forest soil is one of key factors in having sustainable productive forests. In this research extent and intensity of soil disturbance due to extraction of logs of felled trees (20.5 m3/ha) were studied in Nav-e Asalem forest in Gilan province. After finishing the skidder logging operations, soil disturbance were studied by point-transect sampling method and visual assessing. Results indicated that about 19 ± 6.2 percent of surface soils were disturbed due to winching of logs that 11.3 percent of them disturbed with shallow intensity and 7.7 percent disturbed with deep intensity. The extent and intensity of soil disturbance were decreased by increasing distance from skid trail. The extent and intensity of soil disturbance were increased by increasing of ground slope. Soil bulk density in the shallow disturbed soils (1.29 g/cm3) and deep disturbed soils (1.44 g/cm3) were increased 2.4 and 14.3 percent, respectively, than control soils. Soil bulk density of disturbed areas were increased by increasing ground slope, so in slopes greater than 50 percent soil bulk density was increased 20.8 percent more than control soils. Including ways to reducing soil disturbance during skidder logging in the study area are reduction in harvest intensity, implementation of felling direction and skidder logging limitation to slopes less than 50 percent.

Animal trails are the primary wood hauling trails from stump location to the log depot. These trails are created by animal passes. Incomplete access forest roads, low timber volume per hectare and environmental pressure in unstable and steep terrain cause to use mule logging system in some regions of northern forests of Iran. The aim of this research was to investigate the effects of the longitudinal slope of trail used by mule for wood extraction and number of mule passes on soil compaction and porosity. In addition, the optimum soil moisture was determined for scheduling mule logging in forest to reduce site damage.
A mule trail with downward direction was selected in Saad Abad forestry plan. Trail was classifies into 0-10, 10-20 and >20% with respect to longitudinal slope and classified into 2, 4, 8 and 12 passes with respect to number of mule passes. In each class the soil bulk density or compaction, porosity percentage and soil moisture at mule spoor were sampled using metal cylinder and then laboratory measurements. Experiments were done based on factorial design with two main factors of mule passes in four levels and longitudinal slope in three levels. Totally, 12 treatments plus control treatment was performed in SAS software.
Findings showed that soil bilk density increased and soil porosity decreased with increasing the longitudinal slope of trail. Moreover, soil bulk density increase rapidly with increasing mule passes. In 8th pass soil reach to its maximum bulk density and then increasing passes hadn’t significant effect of soil compaction. Interaction effects of passes and longitudinal slopes on soil moisture were significant at probability level of 99%. R2 values showed that variations in most models could describe more than 80% of variation in relationship of soil bulk density and soil moisture. The value of optimum moisture for reducing soil compaction by mule was 35-40%.
It was concluded that in steep slopes and high number of passes the rate of soil compaction was more, therefore before wood extraction in such conditions it is necessary to determine the optimum moisture of soil to schedule logging operation and reduce damage to soil.

This study investigated effects of pure and mixed plantations of Caucasian alder (Alnus subcordata C. A. Mey.) and eastern cottonwood(Populus deltoides Marsh.) on carbon sequestration and some physical and chemical soil properties. The stands across the test site were planted in 1996 under randomized complete blocks design at four replications and five treatments at Chamestan Forest Station. The treatment consisted of five pure and mixed eastern cottonwoodand Caucasian alder stands (pure eastern cottonwood, pure Caucasian alder, mixed Caucasian alder and eastern cottonwoodstands at three different levels: 50+50 %, 33+67 % and 67+33 %, respectively). Combined soil samples were taken at two depths including 0-15 and 15-30 cm. The results showed no significant difference in carbon sequestration rates amongst the treatments at both soil depths, except for pH which was significantly different at soil surface layer (P<0.05). There was a significant (P< 0.01) positive correlation between organic carbon and nitrogen, whereas negative correlations were observed between soil organic carbon and soil bulk density and carbon to nitrogen ratio. Furthermore, presence of Caucasian alder species showed positive effect on the amount of carbon and other soil properties. However, longer term investigations are required to achieve better results.

Environmental impact assessment (EIA) is an effective way to protect the natural resources. Due to needs of human to nature and undesirable effects of over-exploitation on the environment including soil, environmental impact assessment process must be applied in determining the goals, studying the basic conditions, also forecasting and estimating the environmental impacts of project implementation. In this study, fuzzy modeling has been used to assess the environmental impacts in Nour forest park. Three regions containing intensive recreation, extensive recreation and control region were selected, and 30 sample plots were then established in the region as random-systematic. The number of tourists and duration of residence in each sample plot were calculated as input indicators and soil sample was considered as output index. Output and input indicators, classification and fuzzy rules were defined based on Mamdany system. Comparing Model’s results with experimental data showed mode’s error is 6% indicating that model accuracy is favorable. The results showed that with increasing the number of tourist and duration, soil bulk density is also increased, and when the number of tourist reaches to 20 people and duration to an hour, maximum soil compaction occur and further increasing of two factors have no effects on soil compaction. The results also indicated that a fuzzy modeling capability is suitable in predicting the effects of recreation activities and determining the capability of region.