A quantitative study of poplar plantation situation in four Iran provinces

Poplars, a fast-growing species, enjoy a high significance in Iran’s industry. So far, information on poplar plantation, such as area, volume, and harvest, has been obtained by nonscientific and poor methods. A few studies have been conducted to recognize capability of poplar plantation about area, volume, harvest, distribution, and species in three high efficient provinces, i.e., Eastern/ Azerbaijan, Zanjan, Kermanshah, and Ardabil. A Cluster sampling a standard sampling method for conducting similar researches was selected, consisting of two phases. In the first phase we collected library information and half-open interview from villagers. In the second phase field measurement in the villages of these four provinces was considered. Obtained information from field measurement was erected poplar volume, cultivated poplar area, prevalent species and estimating volume via volume and weight tables. Results obtained from the present study indicate that average annual utilization volume of four provinces was 172628.84 m3, with an average error of 14.19 percent.


Introduction
Considering wood product needs of the country and disability in producing sufficient wood from northern forests, developing the poplar plantation area is inevitable in Iran. But a number of factors not only have halted the development of poplar plantation in different regions but also severely caused poplar cutting and changed these lands into agriculture land. Poplar wood volume ‹ 19 › used. In the first phase collecting library information and half-open interviews in rural areas were considered and in the second phase field survey was conducted in villages of the four provinces. Hence a general list of the towns, villages each province were taken, based on information in Iran Oasis Records Book Population and Housing Census Book of Iran (2007). Villages of these provinces were classified in six different groups, i.e., flat, mountainous, plain and mountainous, plain and forest, mountain forest and the other. To represent the whole community about 30 villages in different cities of a province were selected randomly. The number of the selected villages in each city were compatible with total of villages of the cities. Based on obtained addresses from governors of each province regarding selected regions, telephone interview was carried out. Then the necessary adjustments were carried out in selected villages. Information such as area and amount of the annual harvest was collected in each village. The second phase includes selecting villages for the field survey. Six villages from 30 villages were selected randomly from each province in order to carry out field survey.
Data collected from the field survey include: 1) cultivated area of poplar, 2) standing poplar volume, 3) dominant species in each region and 4) measurement of the diameter, height, and estimation of the volume by volume and weight tables. The number of poplar trees in each hectare, average diameter and height of cut and standing poplar for calculating area, volume and weight were determined. Criteria for measurements and calculations were high trees with a diameter of 10 cm. The volume was obtained by poplar volume tables calculated by Bagheri (1997) for poplars in Iran and by Mirsadeghi and Hedayati (1988) for poplars in Turkey. To calculate the weight, the special weight calculated by Bagheri (1997) for Iran poplars was selected.
According to information obtained from the interview and field survey, this information can be extended to the whole province with a definite error percentage. If we multiply average of the cultivated area of the villages in total number of the villages of each province, result cultivated area of each province and regarding annual harvest volume is the same rule.
To determine the sampling error, the field survey was considered as the base of the work. The error percentage of calculation was obtained from Eq. 1. EP = AI -AF / AF ×100 (1) where EP is the error percentage (an area or annual harvest), AI the area or annual harvest of interview and AF the area or annual harvest of field survey.

Results
Based on information gathered from Iran Oasis Records Book (2007), the total number of rural villages of East Azarbaijan Province was determined as 2794, 1101 for Zanjan, 2276 for Ardabil and 2797 for Kermanshah. According to the field survey, the dominant species in East Azarbaijan was shall (Populus nigra) and some modified poplar.
The dominant species of poplar in Zanjan was locally named Raji (Populus nigra) In Ardabil Province the dominant species these modified poplars were more than other Hybrid species such as Tabrizi (Populus nigra) and in Kermanshah dominant species were Tabrizi (Populus nigra).
The number of poplar trees per hectare varied among different provinces. The density of poplar trees in Ardabil was greater compared to the other three provinces. The number of trees of the four provinces on the basis of field survey is presented in Table 1. Volume and average weight of each of the standing poplar trees were calculated based on their average diameter and height by using poplar volume tables (Davision and Riggs, 2004) and average density of poplars (equal 526 kg/m 3 ;Bagheri, 1997) for each province. Table 2 shows the average height, diameter, volume and average weight of standing trees by using different methods. Similarly, the average volume and weight of each of the cut trees for each province were calculated, which are shown in Table 3.
The area of cultivated poplar plantation and volume and weight of standing poplar trees of each province are listed in Table 4. As can be seen from this Table, the area of poplar plantation in Zanjan (6343.58 ha) was more than that of the other three provinces (2031.945, 5493.427 and 3288.403 ha).
The volume and weight of the annual harvest of poplar in the four provinces, according to the interview were illustrated in Table 5. The cultivated area and the annual harvest of poplar, along with the percentage of possible errors in their estimation for each province, were listed in Tables 6-9.

Discussion
The results of Tables 6-8 show that in three poplar rich provinces, i.e., Zanjan, Eastern Azerbaijan, Ardabil and Kermanshah, the area of poplar plantation is 4712.69, 2625.183, 6705.57 and 3995.714 ha, respectively; and the percentage error obtained on the basis of a comparison ‹ 20 › between two methods of interview and field survey was 25.7%, 29.2%, 22%, and 21.5%, respectively. The annual harvest volume in four provinces was 25506.8 m 3 for Zanjan, 46233.54 m 3 for Eastern Azerbaijan, 74991.1 m 3 for Ardabil and 25891.4 m 3 for Kermanshah; and their percentage errors were 4.6%, 9.7%, 15.27%, and 27.2%, respectively, indicating that in both cases obtained error is relatively acceptable.
The percentage errors were merely calculated for the area and volume of the annual harvest. In the case of the area of poplar plantation Ardabil Province achieved a higher priority than the other three provinces (6705.57 ha and 74991.1 m 3 ) that indicate higher poplar plantation area in this province. Report of Country Forests and Rangelands Organization (1992) shows that the area of poplar plantation of the whole country was 150,000 ha, while that of four provinces was 26969 ha; accordingly, these four provinces had about 18% of the total amount of poplar plantation of the whole country (Wood Industry Technical Office. 1992).
On the other hand, based on the statistics presented on the area and rank of the forestry competition in 2003, the total forestry area in Iran has been estimated at 425645 hectares (Iran Statistical Center, 2002)).
If fifty percent of the above mentioned area, poplar plantation is assumed, then it would be two hundred thousand hectares of poplar plantation. The comparison is based on the statistics in this reference (.Iran Statistical Center, 2002). In this case, the level of poplar production (18039) will be about ten percent of the total poplar area Indicating an 8 percent decline in poplar populations in these four provinces. One of the main reasons for the decline in a poplar plantation in these four provinces over the past two decades is the establishment of new wood and paper mills near these provinces, which are major consumers of poplar wood but have not been re-planted after harvest. On the other hand, given the good conditions of Zanjan province for poplar cultivation and the greater motivation of poplar cultivators and the support provided by government institutions in the province, we are seeing an increase in the level of poplar cultivation in the province over the past two decades. According to Forestry Organization statistics in 1992, the poplar plantation area in Zanjan province was 1575 hectares, while according to the current study, the poplar area reached 4712 hectares, indicating a threefold increase.
In the other three provinces, the level of poplar cultivation has declined sharply over the past two decades. The use of modified poplar trees with higher diameter and height is one of the strengths of poplar cultivation in Zanjan province. Whereas in the Eastern Azarbaijan province, the old process of poplar cultivation is still used and there is less interest in poplar cultivation with modified poplar. Zanjan province can be considered as a suitable model for other poplar provinces in terms of poplar cultivation and its optimal utilization.
The poplar harvest in the four provinces is about 172600 cubic meters and the total poplar area is 17900 hectares, which would be 9.6 cubic meters per hectare. On the other hand, 5, 17, 11 and 6 cubic meters per hectare of wood were harvested in Zanjan, Azarbayjan, Ardabil and Kermanshah provinces, respectively.
Currently, about 750000 cubic meters of wood is used for industrial production from northern forests of Iran which due to the impossibility of harvesting it should be obtained from other sources. If the current process of poplar cultivation is maintained, not only this amount of industrial consumption can be provided through poplar cultivation, but also other local consumption and production of wood products can easily be financed by the development of poplar plantation. The use of agricultural wastes and waste also reduces the need for imports, in this case, to meet the wood industry needs of the country we only need 10 to 15 percent of imports (relative to total wood demand) which is negligible. If poplar harvesting continues with the present conditions and the necessary support is provided to poplar farmers, then poplar cultivation would be a great source of supply for the wood and paper industries in the present situation, which are facing a severe shortage of industrial wood.
In the case of poplars, the rate of harvesting as forests does not follow the continuous principle, and this is subject to market conditions in terms of price and demand for poplar wood. Nowadays most of the farmers are traditionally planting poplar and if the price of poplar rises, it is immediately harvested and marketed, so poplar harvest does not correspond to its annual growth rate.
This indicates that if relevant government agencies and the wood and paper industries are planning to set up new units or develop existing units, it is necessary to establish a link between wood industries managers and poplar farmers to reduce the risk of raw material shortages. This relationship can be achieved through the financial support of poplar farmers and the timely purchase of the poplar at affordable prices.
Proper planning in the future should focus on the cultivation of modified poplars in poplar areas such as Zanjan province in order to cope with the rest of the northern forests so that it can provide the needed domestic wood.

Conclusions
Field survey determined that the dominant species in four provinces is Populus nigra. The area of poplar plantation in Zanjan, Eastern Azerbaijan, Ardabil and Kermanshah, is 4712.69, 2625.183, 6705.57 and 3995.714 ha, respectively. The calculated standing volume of poplar plantation in these four provinces were 10638461, 3169946, 5734121 and 77518.66m 3 , respectively. The annual harvest volume was 25506.88 m 3 in Zanjan, 46233.54m 3 in Eastern Azerbaijan, 74991.1 m 3 in Ardabil and 25891.4 m 3 in Kermanshah.
The total volume of standing poplar in three provinces was approximately 19,620,046.66 m 3 , indicating a decrease of standing timber volume compared to the past decade. Zanjan can be a suitable poplar plantation pattern for other poplar provinces due to the use of modified poplar trees with higher diameter and height.
Based on the results in these four provinces on average about 9.6 m 3 per ha wood has been harvested.