Ehsan Abdi

An expert-based approach to forest road network planning by combining Delphi and spatial multi-criteria evaluation

Changes in forest landscapes resulting from road construction have increased remarkably in the last few years. On the other hand, the sustainable management of forest resources can only be achieved through a well-organized road network. In order to minimize the environmental impacts of forest roads, forest road managers must design the road network efficiently and environmentally as well. Efficient planning methodologies can assist forest road managers in considering the technical, economic, and environmental factors that affect forest road planning. This paper describes a three-stage methodology using the Delphi method for selecting the important criteria, the Analytic Hierarchy Process for obtaining the relative importance of the criteria, and finally, a spatial multi-criteria evaluation in a geographic information system (GIS) environment for identifying the lowest-impact road network alternative. Results of the Delphi method revealed that ground slope, lithology, distance from stream network, distance from faults, landslide susceptibility, erosion susceptibility, geology, and soil texture are the most important criteria for forest road planning in the study area. The suitability map for road planning was then obtained by combining the fuzzy map layers of these criteria with respect to their weights. Nine road network alternatives were designed using PEGGER, an ArcView GIS extension, and finally, their values were extracted from the suitability map. Results showed that the methodology was useful for identifying road that met environmental and cost considerations. Based on this work, we suggest future work in forest road planning using multi-criteria evaluation and decision making be considered in other regions and that the road planning criteria identified in this study may be useful.

Distribution and tensile strength of Hornbeam (Carpinus betulus) roots growing on slopes of Caspian Forests, Iran

Biomechanical characteristics of the root system of hornbeam (Carpinus betulus) were assessed by measuring Root Area Ratio (RAR) values and tensile strength of root specimens of eight hornbeam trees growing on hilly terrain of Northern Iran. RAR values of the roots were obtained using profile trenching method at soil depth of the top 0.1 m. In total 123 root specimens were analyzed for tensile strength. Results indicate that in general, RAR decreases with depth, following a power function. The RAR values in up and down slopes have no significant statistical differences. In most cases, the maximum RAR values were located in soil depth of the top 0.1 m, with maximum rooting depth at about 0.75 m. The minimum and maximum RAR values along the profiles were 0.004% and 6.431% for down slope and 0.004% and 3.995% for up slope, respectively. The number of roots in the up and down slope trenches was not significantly different. In the same manner as for RAR, number of roots distributing with depth was satisfactorily approximated a power function. The penetration depths of above 90 percent of the roots were at soil depths of 50 cm and 60 cm for up and down slopes, respectively. Results of Spearman’s bivariate correlation showed no significant correlation between the RAR value with tree diameter and gradient of slope and number of roots. The mean value of root tensile strength was 31.51 ± 1.05 MPa and root tensile strength decreased with the increase in root diameter, following a power law equation. Using ANCOVA, we found intraspecies variation of tensile strength.

Developing a GIS database for forest road management in Arasbaran forest, Iran

Forest roads are an essential infrastructure and prerequisite in the management of forested areas. Sustainable management of roads depends on regular and timely forest road maintenance. A road inventory is the first step of forest road management, control of construction standards, and maintenance operation; and GIS can be a powerful tool for acquirement, analysis, and management of data in road management. The purpose of this study was to obtain the required information to assess existing road standards by way of a road inventory and use the results to schedule maintenance operations. To achieve this goal, a part of the road network from Kaleibarchay watershed in Arasbaran forest was inventoried, and cross sectional components were measured and compared to standard ones. Culverts along the road were also investigated. Road components, problems of surfacing, and slope stability were analyzed in ArcGIS9.3 software. The results showed significant differences between existing parameters and standard ones, and the exceptions were side ditch depth and roadbed. The results of culvert assessment showed that the road segment only had one culvert. According to the results, cross-slope has the highest consistency with standard values. Around a quarter (25.19%) of the road length had no signs of surfacing problems. Among surfacing problems, rutting had the highest abundance and cut slope had more stability problems than fill slope. In order to have better management of drainage systems, we suggested some places for installing new cross drains including culverts and fords. The results of this research can be used in developing effective maintenance operations for the road in this study, and also as a model to study and collect required inventory data and in applying GIS to forest roads management.

Accuracy and precision of consumer-grade GPS positioning in an urban green space environment

The use of global positioning systems (GPS) has increased in recent years, including for urban forestry management, as a result of its wide range of applications, ease of use and direct use of GPS data in geographic information systems. This study was conducted in an urban green space to assess the accuracy and precision of two consumer-grade GPS receivers with regard to ground control point (GCP) coordinates. Eleven fixed GCPs with known positions were selected and their data collected on four days (two seasons) and three different daytime periods (08:00, 11:00 and 14:00) each day. For each treatment (season and daytime) five replications were recorded. The results showed that the best mean position accuracies were provided by the Colorado receiver in leaf-off period (4–5 m), and its corresponding position accuracies for summer ranged from 9 to 12 m. The results of the Rino receiver mean position error in summer (19–36 m) and winter (10–26 m) were higher than reported in literature. Point averaging had a positive effect on accuracy in both receivers for winter. In summer, three-point averaging was more efficient than five-point averaging. During the day, the Colorado receiver had the best positional accuracy at 08:00 in winter, but in summer there was a large variation in the results. For the Rino receiver there was no general trend; however, results taken at 11:00 and 14:00 were better than those at 08:00. Regarding precision, point averaging had a positive effect on the Colorado while the Rino precision indicated the contrary. The Colorado receiver had better precision than the Rino in both seasons, and was the best in summer. The Rino receiver had better precision in summer compared to winter, and in both recievers daytime had no significant effect on precision. The measured accuracies of Colorado are acceptable for many environment and urban forestry measurement applications and satisfy mapping requirements, but the Rino receiver showed poorer results.

How deep can forest vegetation cover extend their hydrological reinforcing contribution

University of Tehran, Department of Forestry and Forest Economics, Karaj, Iran University of Tehran, Department of Range and Watershed Management, Karaj, Iran University of Minnesota, Department of Bioproducts and Biosystems Engineering, St. Paul, Minnesota, USA University of Napoli Federico II, Department of Agriculture, Division of Agricultural, Forest and Biosystems Engineering, Naples, Italy Correspondence Ehsan Abdi, Department of Forestry and Forest Economics, University of Tehran, Karaj, Tehran 3158777871, Iran. Email: abdie@ut.ac.ir

Soil water dynamics under different forest vegetation cover: Implications for hillslope stability: Soil water dynamics under forest vegetation cover

Though it is well known that vegetation affects the water balance of soils through canopy interception and evapotranspiration, its hydrological contribution to soil hydrology and stability is yet to be fully quantified. To improve understanding of this hydrological process, soil water dynamics have been monitored at three adjacent hillslopes with different vegetation covers (deciduous tree cover, coniferous tree cover, and grass cover), for nine months from December 2014 to September 2015. The monitored soil moisture values were translated into soil matric suction (SMS) values to facilitate the analysis of hillslope stability. Our observations showed significant seasonal variations in SMS for each vegetation cover condition. However, a significant difference between different vegetation covers was only evident during the winter season where the mean SMS under coniferous tree cover (83.6 kPa) was significantly greater than that under grass cover (41 kPa). The hydrological reinforcing contribution due to matric suction was highest for the hillslope with coniferous tree cover, while the hillslope with deciduous tree cover was second and the hillslope with grass cover was third. The greatest contributions for all cover types were during the summer season. During the winter season, the wettest period of the monitoring study, the additional hydrological reinforcing contributions provided by the deciduous tree cover (1.5 to 6.5 kPa) or the grass cover (0.9 to 5.4 kPa) were insufficient to avoid potential slope failure conditions. However, the additional hydrological reinforcing contribution from the coniferous tree cover (5.8 to 10.4 kPa) was sufficient to provide potentially stable hillslope conditions during the winter season. Our study clearly suggests that during the winter season the hydrological effects from both deciduous tree and grass covers are insufficient to promote slope stability, while the hydrological reinforcing effects from the coniferous tree cover are sufficient even during the winter season. Copyright

Soil hydrophysical degradation associated with forest operations

ABSTRACT Skid trails in the Hyrcanian forest of northern Iran are important for moving wood to log landings; however, they can cause soil compaction and alter water infiltration. This research therefore presents an analysis of the impact of ground-based skidding on soil hydrophysical properties in Kuhmiyan forest located in the Hyrcanian forest. Soil infiltration, bulk density, and soil resistance to penetration have been studied at three different depths of soil along the skid trails. Three sampling locations were considered: wheel ruts, center of skid trails, and undisturbed forest (control). The results showed that the total infiltration rate, and also the instantaneous infiltration rate, were significantly higher in the control treatment. The results also showed an increase of 57% and 31% for the soil bulk density at wheel ruts and centers of skid trails compared to the control. Furthermore, there was a significant difference between soil resistance in the control and the other two treatments, with wheel ruts having the highest resistance. According to the results, there was a strong negative correlation between infiltration and soil resistance (r = –0.94), and between infiltration and bulk density (r = –0.93). Using a protective layer of slash and logging debris and residual on skid trails can be highly recommended to moderate soil compaction and mitigate the destructive impact of logging equipment.