INTRODUCTION
The North forest of Iran needs to manage and to plan fundamentally by designing forest road network. Up to now, road planning was based on studying topography map and field. It is very important to know everything about area of road planning. According to the statistic data issued by Forest and Rangelands Organization of Iran (2000), only 7% of Iran covers by forests form which the portion of the North is less than 1%. Kind of Vegetation is the main factor for soil conservation, water storage, wild habitat and biotic storage, tourism, entertainment and recreation and finally as a productive resource has many material and spiritual values (Sarikhani and Madjnonian, 1996; Sarikhani, 2002). The road way grade should be carefully selected, not only to minimize the total road cost but also to reduce the environmental impact and to improve driver safety (Akay, 2005). An optimized plan can be considered as a design that is characterized by attributes of technical-economic environmental conception especially using GIS (Goudarzi, 1999; Hruza, 2003). Optimum planning of forest roads network is the basis and foundation for reasonable and practical preparation of forestry management and utilize it safely. Precise tracing of the path to plan the access roads networks for conservation and exploitation of the forest is the basis for forest management. Geographical information system can be used to gather all needed layers for selecting correct paths (Akay 2004). This system is used for a set of information series and modeling methods, which play their role through offering Geographical Information structure, analysis, offering quantitative information from geographic places in different forms and graphical and digital methods. Geographical Information System capabilities uses for reasonable decision making through increasing precision and decreasing expenses to implement path tracing and optimum recognition of the land (Makhdoum, 2003). A variety of studies in different fields of forestry, watershed management were implemented on the research area. In this research, fairly complete recognition of the strong areas to perform the path, slope map, geographical direction of the slopes, type of soil and bed rock, current type of trees, stock per hectare and finally their analysis were studied to assist us planning and designing Forest road environmentally and safely.
MATERIALS AND METHODS
Study area: It is located on the west of Nowshahr (Mazandaran Province,
Training and Research Forest of Natural Resources Faculty of Tehran University),
between North latitude of 36° 27’ and 36° 40’ and eastern
longitude of 51° 32’ and 51° 43’ including 7 districts which
their area figure out to 8800 hectares. A district with the area of 1075 hectares
called Namkhaneh (Goudarzi, 1999). The precipitation rate fluctuates from 1300
to 1600 mm and the minimum rainfall occurs in the middle of summer.
Its geological structure is made of limestone of the third era of geology and
due to geomorphologic phenomena such as Dolin in the zone, there is a proper
drainage all over this district. Five southeastern parcels out of 27 parcels
in the study zone are so called protective parcels. They are excluded from the
forest road network planning due to their excessive dip and their area amounts
to 285 hectares. According to the statistics data the extent of
main (First Degree) and tributary roads in Namkhaneh district amounts to 11.340
km, the length density of which is 14.36 (m ha-1).
Research method: The first step in through study was recognition of
effective factors of the area for finding proper paths, which were processed
in GIS software. Thus Arcview software was selected to produce maps and analyze
database. In spite of the literature review and history of the research, the
recognition of the study area soil, its bedrock and dip condition, geographical
direction of the slopes, the amount of stock per hectare and the percent forest
type were needed. So it was decided to collect them as digital information.
Dip (slope) map and geographical directions of slopes were prepared using GIS
capabilities and by Digital Elevation Model (DEM). Dip map was classified based
on the percentage using topographic map of the zone and was extracted by Arcview
software. By defining the geographical directions of the slopes in the software,
its map was also achieved in separation with its classes. The type of different
soils on the study zone was very important and extracted from the pedology studies
of Kheyroud Forest (Sarmadyan and Djafari, 2001). Using the prepared digital
maps for all districts of this Forest, the border of research district was separated
in Arcview software and the map of soil types in Namkhaneh district and soil
drainage condition were provided. Some of the characteristics were achieved
from last Project booklet such as stock per hectare and
tree types percent were used to produce some maps by Arcview software. After
regulating achieved data and database from the study area, dip percentage maps,
soil type and its drainage, percent type of the growing stock, number of trees
per hectare and geographical directions of the slopes were composed and a number
of ecological homogenous units were extracted.
RESULTS
After collecting information from the study zone, they were studied and then
were processed using GIS capabilities in Arcview software, the following maps
and tables were produced and extracted for further study and discussion:
| • |
Digital map of the study zone topography (Fig.
1). |
| • |
Slope map separated into three classes (0-25, 25-40, >40%) (Fig.
2). |
| • |
The map of the geographical direction of slopes separated into five classes
(North, South, East, West and Plate) (Fig. 3). |
| • |
Map of the soil drainage condition, which was prepared, based on the map
of soil types and classified into three categories (Good, Medium and Poor)
(Fig. 4). |
| • |
Map of present forest type was prepared using growing elements of the
parcels and three major types were specified (Beech, Beech-Hornbeam and
Hornbeam) (Fig. 5). |
| • |
Map of volume per hectare using GIS capabilities (100-200, 200-350, 350-450,
>450 m3) (Fig. 6). |
|
| Fig. 2: |
Slope map Kheyroud forest area |
|
| Fig. 3: |
Soil map of Kheyroud forest area |
|
| Fig. 4: |
Aspect map of Kheyroad forest area |
|
| Fig. 5: |
Forest type map of Kheyroud |
|
| Fig. 6: |
Volume per hectare map of Kheyroud forest area |
| Table 1: |
Characteristics of the study area |
|
|
To study the effective factors for tracing the proper paths, the frequency rate of the areas of each specified class on the research area map was studied and the tables of the their codes cover areas were extracted:
| • |
Characteristics table of the study zone parcels extracted
from the forestry Project booklet (2002) are given in Table
1. |
| • |
Based on topographic map of the study area (Fig. 1 and
2) surface of each slope class was determined (Table
2). |
| • |
According to the forest project booklet (Table 1) and
soil condition on the study area, table of soil type factor and its characteristics
are classified. |
Figure 4 and Table 3 showed that soil type
was deep dark brown with fairly good drainage as the widest part of soil surface
with 44.62%.
| Table 2: |
Slope percentage factor, area and frequency percentage of
each class |
|
| Table 3: |
Percentage of soil type |
|
|
| Table 4: |
Number of soil type based on Fig. 4 |
|
|
| Table 5: |
Geographical direction factor, area and frequency percentage
for each category |
|
|
| Table 6: |
Volume per hectare, area and frequency percentage for each
category |
|
|
Figure 3 and Table 5 showed that the most percent was western direction and Good condition about slope direction with 47.76%.
| • |
Based on Table 1 (col.7) volume per hectare
was arranged in Table 6. |
DISCUSSION
Investigation and studying of effective factors for path tracing in forest
is very important environmentally and socio-economically (Goudarzi, 1999; Tan,
2000; Hruza, 2003). Precise tracing of the path to plan the access roads networks
for conservation and exploitation of the forest is the basis for forest management
(Sarikhani, 2002). According to the statistic data that issued by Forest and
Rangelands Organization (2000) only 7000 km were constructed and used. Based
on the total forest cover area in the north of Iran that is 1.9 million hectare,
need to have 38000 (km) road optimally distributed with 20 m ha-1
length density. A long time and much money should be spend for this length of
forest roads planning,. If we use new technology such as GIS technique, the
information and exact data will prepare to analyze for path tracing. Effective
factors including (DEM) Digital Elevation Model, soil map, bedrock map, drainage
map were classified carefully. Figure 4 and Table
3 showed that soil type was deep dark brown with fairly good drainage as
the widest part of soil surface with 44.62%. The major soil type was deep dark
brown forest soil with fairly good drainage condition that was suitable for
path tracing in this district. Figure 3 and Table
5 showed that the most percent was western direction and Good condition
about slope direction with 47.76%. The bedrock was Marn about 44.6% (Table
4). Table 2 and Fig. 3 showed that the
most slope percent was between 25-40% and geographical direction was West that
was a dry side and drainage condition, infiltration of soil was good (Sarikhani, 2002; Modyri, 1999). So there was no treat to path selecting on most part of
the study area. With these factors the costs of construction and maintenance
were decreased logically the project line can be planned technically and environmentally,
so low slope needs low cutting or filling then cost of soil transporting will
be low. As a whole, it was concluded that research area had some effective factors
to path tracing (road selecting) for planning forest roads. Finally, using GIS
for identifying road selecting factors in mountain forest caused to increase
precision decreasing expense in path tracing, building and maintenance (Acar,
1997; Amiri, 2000; Akay 2004). The most important of all was saving the time
of performance and soil conservation. In this study, logical justification of
precision of Geographical Information System was approved clearly.