Estimate of the quantity of cork on pile in Tunisia
The cork oak in Tunisia occupies nearly 90,423 ha according to the result of the national forest and pastoral inventory published in 2010. Each year nearly 8000 ha of cork oak forest on average are subject of a potential harvest of 80,000 quintals of cork. The harvested cork is transported to undeveloped cork parks, and once it has been dried in the open air and reached equilibrium moisture, it is weighed by the regional forest services and then stacked. At the end, we obtain a total quantity in quintals for each cork park. In 2016, experts have shown that the quantity of cork stored and declared by the regional forest administration is overestimated in relation to the actual quantity.
- Defining a simple and reliable methodology for the quantitative evaluation of stacked cork at cork parks that will serve as a mean of controlling the quantity weighed previously,
- Create a database at each cork park to determine the weight of a cubic meter of cork reproduction.
- Train forest technicians to generalize this method on all cork parks in Tunisia from the 2020 harvest.
The method used is based essentially on data collected in the field:
- Count the number of cork stack according to the existing categories
- For each stack of cork, measure at random 2 lengths, 3 widths and 10 heights
- Determine the size of the sample to be weighed from each stack of cork, 1/10 of the length of the stack
- Select at random one end of the stack and mark with a vertical band using a touch-up bomb the limit of the sample
- Weigh the total quantity of the cork of the determined sample,
- Measure using a moisture meter the moisture content of four boards taken at random relative to each weighing
-The difference between the quantities of cork surveyed (50 649 quintals) and those actually weighed (52 738 quintals) is equal to 4%, therefore the quantities retained and sold by tender are those weighed,
-The total number of parks surveyed is 31.
-The declaration of the quantities weighed by the regional forest services must be for each pile and not on the whole cork park. Because if there is a difference between the quantities weighed and those estimated beyond plus or minus 5%, the administration will be asked to make a second estimate of all the stacks of cork.
-The weighing operation remains the best way to determine the actual quantity of cork produced. Therefore, at the time of weighing, the presence of the forest technician is mandatory to ensure regular control. Knowing that the weighing operation is done with workers sites non-qualified.
Impacts and weaknesses
- Simple to apply,
- Insure the cork manufacturers who buy this kind of product concerning the declared quantities
- Empowers the regional forest technicians for personally assisting in the weighing operation by site workers
- The size of the sample chosen and weighed (1/10) is representative of the size of the entire stack of cork
- Allows forest technicians to know the weight of a specific cork cubic meter for each park and which will serve as a means of subsequent control
- The fieldwork requires a lot of time, physical energy, precision, technical and material personnel - Some forestry technicians at the regional level do not measure the moisture content at the time of actual weighing.
-Because of the lack of human and material means which prevents the daily control of the quantities weighed by the forestry technicians at the regional level, the forest administration is in the process of looking for solutions of sale of cork in stacked cubic meter.
-Improve the theoretical and practical knowledge of forest engineers and technicians in understanding the anatomical and physical properties of cork and its behavior under the conditions of its storage (temperature, air humidity ...)