Chapter 5. Tapping methods and improvement

Two lines of research were pursued with respect to tapping methods and improved benzoin production. Firstly, the relationship between tree size and benzoin production was investigated; secondly, tapping methods used in Lao PDR and elsewhere in Southeast Asia were studied.

5.1 Tree size and benzoin production

Benzoin tappers in Lao PDR believe through casual observation that several factors affect resin characteristics. For example, it is often said that trees having dark, thick and rough bark produce the most benzoin. However, bark characteristics generally change with age and growth of the tree. It is natural for young trees to have smooth and light-coloured bark that becomes rough and darker with age. It is also claimed that tapping cuts positioned on the upper part of the stem secrete more resin than those lower down. These first-hand observations may well be true, but there are no substantiating published scientific research results.

Field research was conducted to attempt to answer the following questions:

1) Is there a relationship between the size of the tree (based on stem diameter) and benzoin production?

2) Is there a correlation between bark thickness and stem diameter?

3) Is there a relationship between benzoin yield and the height of tapping cuts on the stem?

5.1.1 Trial plot

A 1-hectare plot of styrax trees located opposite Ban Kachet village on the higher side of the road at an elevation of 800 m was selected for the studies. The study plot consisted of 348 trees that had regenerated in 1991, and represented a 6-year old tree stand. Benzoin tapping of the trees had been going on for 2-3 years. The study ran from May 1997 to April 1998.

5.1.2 Sample collection and methodology

After the undergrowth was cleared, 60 styrax trees were selected for the experiment. The DBH of selected trees was measured using a ribbon tape; diameters ranged from 8 cm to 23.9 cm. The 60 trees were grouped into 13 diameter classes as shown in Table 5.1.

Table 5.1 Size classes of styrax trees studied

The bark thickness at 1.3 m height from the ground was also recorded for each tree, at the time of taking the DBH measurement.

The standardized traditional Lao tapping method (Type 5) (see section 5.3.3) was used to tap each selected tree for benzoin at the end of September 1997. The method was modified from the general local method to a standard for future research. Each cut was 7.5 cm wide and 6 cm long with the lower part of the cut bark remaining attached to the tree; the beating treatment was not carried out.

On each tree, a single tapping cut was made at 1-m intervals up to 5 m above ground level. All the cuts faced north in order to reduce the influence of the tapping direction, if any. Therefore, apart from comparing the yield of resin between trees of different diameter classes, it was also possible to determine whether resin yield varied at different positions on the stem.

Careful harvesting of the benzoin was carried out at the end of March 1998 (5-6 months after tapping). The traditional Lao method was followed, using a forest knife, bamboo basket and bamboo ladder. The harvested product was weighed and simple qualitative characteristics (size, colour and purity) recorded on a tally sheet. Some samples were sent to the Food and Drug Quality Control Centre in Vientiane for chemical analysis.

The harvesting data were analyzed to determine any differences in yield according to DBH class and height of the tapping cuts.

5.1.3 Results

The styrax tree and benzoin yield data from each tapping cut at five different height levels of the 60 trees are tabulated in Table 5.2.

Examination of the benzoin yield data recorded for each of the 60 trees indicates that out of the five largest trees only two (ID Nos. 31 and 57) produced significant amounts. Of the remaining three largest trees, one did not produce benzoin at all and the other two produced only small amounts, i.e. 8.7 g and 9.6 g.

Table 5.2 Benzoin yield at different tapping heights of 60 representative styrax trees

A total of 16 out of the 60 trees did not produce any resin regardless of the height of tapping cuts. It is interesting to note that most of these 16 trees were from the small DBH classes, i.e. < 13 cm.

A plot of bark thickness against stem diameter of the 60 trees is shown in Figure 5.1. It shows a positive correlation between bark thickness and stem diameter.

Figure 5.1 Plot of bark thickness against stem diameter of styrax trees in a 7-year-old regrowth forest at Ban Kachet village, Nam Bak district, Luang Prabang province

An analysis of variance was performed by treating DBH classes as one treatment factor and height of the tapping cuts as another. Analysis of the output is shown in Table 5.3.

Table 5.3 Analysis of variance (ANOVA) of mean benzoin yield of 13 DBH classes at 5 different tapping heights

^1/* = significant differences at P<0.05 level

The results from the analysis of variance show that benzoin yield varied significantly between diameter classes while the differences in yield between tapping heights were not statistically significant.

Mean benzoin yields recorded for 13 DBH classes at five tapping heights are shown in Table 5.4.

Table 5.4 Mean benzoin yield (g) obtained for 13 DBH classes and 5 tapping heights in a study of relationship between tree size and resin yield

Benzoin yields were greater with increased DBH class. Yields were particularly low where DBH was smaller than 13 cm (DBH classes 1-5). The highest yields were recorded for DBH class 12 (19.0-19.9 cm), a mean of 32.8 g. The yields obtained for 5 trees in the largest DBH class (>20 cm) were surprisingly low, mean 14.7 g.

Although the yield of benzoin did not differ significantly between tapping cuts at different heights, it was the lowest at 1 m. The mean benzoin yield increased from 2.1 g at 1 m to a peak of 3.6 g at 3 m. The yield, however, declined when the tapping cuts were higher on the stem. The mean values recorded at 4 m and 5 m were 2.9 g and 3.0 g respectively, which were higher than those obtained at 1 m and 2 m.

5.1.4 Conclusion

Results obtained from studying the relationship between tree size and resin production demonstrate that small trees are likely to produce less benzoin than larger trees. Trees having a DBH less than 13 cm were found to be unsuitable for tapping.

There was no direct comparison of the resin yield in relation to bark thickness of the tree. However, given that bark thickness is correlated positively with tree diameter, it would be reasonable to assume that trees with thick bark are likely to produce more benzoin than those with thin bark.

The results, however, did not support the popular claim by villagers that benzoin yield is greater at higher tapping positions on the tree. Although yields increased with an increase in the height of tapping cuts from 1 m to 3 m, further increase in the height showed a decline in benzoin production.

5.1.5 Recommendations

The overall productivity of the trees in the experimental plots was extremely poor when compared to that observed for the trees tapped by villagers in adjacent areas. Therefore it was recommended that this study be repeated in another season to verify the results. The Lao traditional tapping method (without any modification) should be used for the trial. As with the first study, five cuts at 1-m intervals up to 5 m above ground level should be made on each tree.

Diameters of all the remaining trees in the study plot should be re-measured for benzoin tapping in a future season to obtain more information. Trees that were used for benzoin tapping in the previous season could also be included.

The tapping results, however, do confirm that more benzoin is produced at higher (but not the highest) positions on the stem. But the results raise more questions than answers. It was expected that the lower portion of the stem would produce more benzoin because the diameter is larger, and bark is thicker and rougher than the upper portion. This aspect of benzoin production is worthy of further investigation.

The latest findings of the relationship between tree size and benzoin production trial are described in Appendix 5.

5.2 Tapping methods

5.2.1 General tapping methods

In Lao PDR, styrax trees are tapped for the first time at 6-7 years of age. In general, the trees are felled when they reach about age 10, the exact age depending upon the demands of the shifting cultivation rotation being followed by farmers. The trees are tapped during September and November, when they are bearing fruit and the leaves are dying (the trees are deciduous). At that time, the bark is easy to cut. About 1-3 weeks after tapping, the styrax tree will close the tapping cuts with benzoin, but sap and resin will continue to be secreted. During the cooler, dryer winter season, the resin will dry and become hard and fragile. It is at this stage that the benzoin can be collected.

In Southeast Asia, three general methods are employed for benzoin tapping and these are described below.

5.2.2 Malaysian tapping

There are two Malaysian tapping methods. The first consists of tapping the trunk about 40 cm above the ground. Using a sharp knife, a triangular cut 15-20 cm long is made with the triangle pointing downwards. Three such triangles are cut into the tree bark at the same level, to a depth of about 2 mm. The bark and wood are removed from each cut and the resin begins to secrete. Resin is collected every 3 months.

The second Malaysian tapping method also employs triangular-shaped cuts pointing downwards, but is somewhat different from the first. In this method, three lines having three cuts each are made, one above the other. The first line is 40 cm from the ground, the second is at 80 cm and the third at 120 cm. As in the first Malaysian method, resin is collected every 3 months.

5.2.3 Indonesian tapping

Trees of Styrax benzoin and S. paralleloneurum are the source of Sumatra benzoin. The Indonesian method of tapping uses three tools. A hoop-shaped knife is used to rub and clean off the bark. Styrax trees in Indonesia are very old (about 60 years of age) and the bark is thick. Next, a wedge, the second tool, is inserted between the bark and wood to make the tapped area into a semi-parabola for collecting the resin. After that the bark around the tapped area is beaten. Resin is collected about 3-4 months after tapping. A semi-parabola knife (tool 3) is used to cut along the tapped area to open the bark before collecting the resin. The resin is generally of good quality and classified as Grade A. After another 3-4 months, a further quantity of resin is collected from the tapped area (Grade B). Finally, a third collection is made after another 3-4 months (Grade C).

5.2.4 Laotian tapping

A forest knife is used to cut the bark, making an incision about 5-10 cm in length, without damaging the cambium. Usually, however, the wood is injured. The knife is then twisted to open the bark before allowing it to close. Tapping occurs at about 50 cm from ground level. There are three lines cut into the bark, to the right, front and left. Village benzoin tappers also climb the trees using a fixed bamboo pole with a rope to serve as a ladder. In this manner, tapping can be done up to a height of 10 m. In some locations, the bark surrounding the tapped area is beaten to stimulate resin flow.

5.3 Tapping trials

The purpose of this study was to develop suitable benzoin tapping methods taking into account both quantity and quality, as well as the costs, equipment and time requirements.

The three main objectives of the experiments were: 1) to compare the yields of benzoin using different tapping methods; 2) to examine benzoin harvesting practices; and 3) to increase benzoin yields in terms of quantity and quality.

5.3.1 Trial plot

A trial plot suitable for the tapping methods experiment was established in the forest a short distance from Ban Kachet, Nam Bak district, Luang Prabang. The 1.2 ha plot was rectangular in shape and at an elevation of 670-690 m. The styrax trees occurring in the plot were the result of natural regeneration and were mixed with other tree species. There was dense undergrowth. The average canopy height was 9-10 m. Shifting cultivation had been practised on the site in 1989. Styrax trees of 7-8 years old and sufficient size were suitable for resin tapping.

The trial plot was established towards the end of 1996 (Kashio, 1997; and Subansenee, 1997). Undergrowth was cleared to make tapping easier. Then 160 styrax trees with DBH greater than 12.0 cm were selected for the experiments.

5.3.2 Sample collection

The 160 styrax trees were numbered and measured for DBH and height. The DBH range was 12.4-23 cm, with an average of 16 cm. The maximum tree height was 18 m and the minimum 11 m; the average was approximately 14 m. For efficient monitoring of the experiment, the locations of all study trees were recorded in a sketch map of the plot with individual numbers. The experiment lasted from May 1997 to April 1998.

5.3.3 Methodology

The 160 selected styrax trees were divided into eight groups of 20 trees each; one group for each of the eight tapping methods to be studied. A Microsoft Excel program was used to categorize the trees to ensure as even a distribution as possible in terms of tree size (DBH), to reduce the bias. Tree height was not considered in forming the groups as it was assumed to be less important in relation to resin production.

To avoid any confusion in the field, the 160 trees were clearly identified by tying a ribbon in different colours assigned to each of the eight groups.

Each tree was tapped at four different levels. The first tapping level was 50 cm from the ground. The second, third and fourth were at heights of 1 m, 1.5 m and 2 m, respectively. The north face of the tree was tapped. The date was established when each tree was to be tapped. The area to be tapped was marked and outlined using an indelible marker and a hard plastic template of the appropriate shape. The bark thickness of every tree was also measured.

The eight different tapping methods used in the study are described below.

Type 1. Malaysian Method A

The trees were tapped with a triangular-shaped cut pointing down as shown in Figure 5.2. The cut was 7.5 cm wide to a depth of about 2 mm inside the woody part of the tree (the cambium was, therefore, totally removed). A V-shaped, 5 x 5 cm galvanized metal sheet was fixed in the bark to direct the resin flow into a tin can attached to the trunk of the tree.

Figure 5.2 Malaysian Method

Type 2. Malaysian Method B

The same tapping method as Type 1, except that the bark around the tapping area was beaten to stimulate resin flow.

Type 3. Malaysian Method C

Again the same method as Type 1, except that cuts were made in the cambium layer only, not into the wood.

Type 4. Malaysian Method D

The same method as Type 3 above, except that the bark around the tapping area was beaten to stimulate resin flow.

Type 5. Standardized Traditional Lao Method A

This method was modified from the traditional method locally practised to standardize the research. Cuts were made in the shape of a rectangle, measuring 7.5 cm wide and 6 cm long (Figure 5.3). The bark was loosened to open the upper part and form a pocket. The lower bark was left attached and served as a receptacle to collect the resin.

Figure 5.3 Standardized Traditional Lao Method

Type 6. Standardized Traditional Lao Method B

The same method as Type 5, except that the bark around the tapping area was beaten to stimulate resin flow.

Type 7. Standardized Traditional Indonesian Method

This tapping method was adapted to be suitable for the research. A chisel was used to cut the bark in a straight vertical line 7.5 cm in length (Figure 5.4). Next, the chisel was inserted between the bark and the cambium at a depth of 3 cm. Then a rectangular-shaped cut measuring 7.5 x 3 cm was made on the left side of the tapping area only. This created a pocket between the bark and the wood to collect the resin produced.

Figure 5.4 Standardized Traditional Indonesian Method

Type 8. V-shaped Method

The tapping was done using a V-shaped cut, each side of the V measuring 7.5 cm in length and 2.5 cm in width (Figure 5.5). After making the cut, a 5 x 5 cm piece of zinc sheet was attached and bent into a V-shaped to direct the flow of benzoin into a tin can positioned at the bottom of the V and nailed to the trunk.

Figure 5.5 V-shaped Method

5.3.4 Initial observations

After tapping for 1-2 months, a study of the flow characteristics of the resin was made by observing each tapped area. At that time, some trees tapped by the V-shaped Method (Type 8) were harvested to increase the trial yield.

5.3.5 Harvesting

Benzoin was collected in March 1998 when it was dry, 5-6 months after tapping. A forest knife was used to remove the resin in each of the eight trials. The benzoin was weighed and each piece evaluated qualitatively. Results were recorded for each tree on a tally sheet for later analysis of the quality of the benzoin derived under each tapping method.

Three product characteristics were considered with respect to quality: size, colour and purity. These were adapted from the report by Coppen (1997) and considered the percentage of the product according to the following categories. The results were recorded on a tally sheet.

5.3.6 Analysis

The pieces of benzoin were packed in vacuum bags and sent to a laboratory for chemical analysis.

Analysis of variance (ANOVA) was conducted to determine the differences in the benzoin yields between tapping method. The final results were used to answer the following questions:

1) How efficient are each of the eight tapping methods in terms of the quantity of benzoin produced? After consideration of the tapping and harvesting period, and tools used, the most promising method can be identified for adoption and further development.

2) Is more resin produced by tapping into the wood (e.g. Type 1), or by tapping only into the cambium layer (e.g. Type 3)? The results will also answer the question as to whether the benzoin is coming primarily from the cambium or a combination of wood and cambium. Tapping depth can be adjusted accordingly.

3) Is more resin produced as a result of beating the bark around the tapping area (e.g. Type 2) as compared to not beating the tapping area (e.g. Type 1). Tapping practices can again be adjusted accordingly.

5.3.7 Results and observations

Table 5.5 shows the yields obtained using the eight tapping methods.

The following observations can be made.

1) The comparatively lower yields using the Malaysian tapping method could be improved upon. Instead of nailing the tin can to the tree to catch the resin, it could be attached more easily with wire. Another problem with the tin cans was that in some instances they filled with rainwater, which might have negatively affected the benzoin production. The collection system and perhaps also the yield would be improved by use of a plastic or ceramic container that would drain off water but hold the resin.

2) The immediate areas of the tapping cuts in the Malaysian methods (Types 1-4) and the V-shaped Method (Type 8) were examined. Small spots of black fungus were found on the wood surrounding the cuts. After one week of tapping no trace of benzoin, sap or oil was observed. However, in some of the cuts that included beating the bark (Types 3 & 4), there were traces of resin at the edges of the cuts that may later have developed into benzoin.

3) In the Standardized Traditional Lao Method A and B (Types 5 & 6) it was noted that the bark pouches contained large amounts of moisture. On the exposed cambium and wood surfaces, a light, clear resin was present, especially in those locations that had been beaten with a chisel or other tool where a large amount of crystalline resin had formed into larger resin drops. The drops were sticky to the touch which is a test for benzoin. However, in some areas of the cut where the bark had peeled away or contracted, the underlying wood surface was dry and there were no traces of resin crystals. These differences could represent a critical factor in the production of benzoin in the future.

4) A preliminary observation suggests that the Standardized Traditional Indonesian Method (Type 7) may be the most time-efficient. This method produced the highest benzoin yield, apparently due to the tight coverage of the resin in the pocket of styrax bark. However, Type 7 may require additional harvesting time and may also be limited in terms of tapping height as compared to the traditional Lao method (i.e. up to 10 m; see section 5.2.4); not the standardized Lao method used in the trials. In the Lao methods (Types 5 & 6) a wider tapping cut was made to allow a longer time for resin flow. But with the traditional Lao tapping the time requirement for cutting may be shorter and more efficient and it may be possible to tap to the higher level using only a single cut with the forest knife. The benzoin from the traditional Lao method may also be harvested more easily, but the quality of the product is lower than from the Indonesian tapping method. Both the Indonesian and Lao methods, however, may be carried out more efficiently in terms of tapping and harvesting than the methods which involve peeling off the bark (Malaysian and V-shaped).

Table 5.5 Yields of benzoin, and quality, from tapping trials in the 8-year old regrowth styrax forest at Ban Kachet

¹ Quality: Percentage of product quality proportion in each item.

² Size: Grade 1: > 60% bigger than 12 mm; Grade 2: 30-60% bigger than 12 mm; Grade 3: < 30% bigger than 12 mm.

³ Colour: Grade 1: > 60% pale; Grade 2: 30-60% pale; Grade 3: < 30% pale.

⁴ Purity: Grade 1: > 60% clean; Grade 2: 30-60% clean; Grade 3: < 30% clean.

5.3.8 Observations on resin flow

Characteristics of resin flow were studied by closely observing the conditions at the site of the tapping cuts over a 2-month period. Observations included data on any possible environmental effects on the quantity of benzoin produced, as well as on the quality of the product, i.e. size of pieces, colour, purity and dust. Through direct observations and field interviews the following provisional conclusions were reached.

1) Based upon observations made two months after tapping, along with analysis of the benzoin produced, it was concluded that the resin resulting from the trials is of the same quality regardless of tapping methods employed. It was also confirmed that the flow of resin is not from the wood, but from the area between the bark and the cambium.

2) It was observed that in the Standardized Lao Tapping Method, about 7-15 days after tapping, there was some transparent gum or oil, along with water appearing at the surface of the cut. The oil was resinous and sticky. On some cuts, the resin had formed into sizable pieces, but in other instances there was no resinous covering of the cut. In these cases, the water mixed with the resin had apparently quickly evaporated leaving a dry surface. It appears that when larger pieces of resin were present, water evaporation had occurred slowly when the weather was cool and dry; the resin was hard, brittle and ready for collection.

3) From the general observations made, it can be assumed that the tree draws nutrients from the xylem and from the leaves during the photosynthetic process, leading to the formation and flow of resin. Sap is drawn through the phloem in the cambium, which is between the wood and bark. When the bark is injured, sap is secreted and flows around the wound; clear liquid is visible at this stage. After 7-15 days the sap forms drops of resin. The size of the individual resin drop is increased if more sap is secreted. During the winter months the water in the resin drop evaporates and the residual resin becomes harder until, finally, it takes on the familiar characteristics of benzoin. The whole process takes 3-5 months.

4) In comparing the tapping methods in the experiment to the traditional Lao method, the villagers were not satisfied with the experimental tapping results. This was especially true in the case of the Standardized Lao Method because of the low resin production. It was assumed that the traditional villagers method, where the bark is cut and the knife is twisted to widen the cut, is more damaging to the bark and causes more resin to be secreted. At the same time, the cells in the bark do not become dry. A statistical analysis must be carried out to provide reliable results.

5) In the experiments with the Malaysian tapping methods (Types 1-4), resin production was low. Very few of the tin cans were found to contain resin because the small amounts secreted remained attached to the tree. It was evident that the Malaysian method is not suitable for styrax trees in Lao PDR. It is possible that in this method the size of the cut is too large, because in the V-shaped cut (Type 8) experiment, more resin was produced than in any of the experiments with the Malaysian method. The optimal size of the tapping cut may have an important effect on benzoin yield.

6) Using tin cans to collect resin was found to be impractical. Because of the 1-2 month duration required for resin formation, the can becomes a trap for insects, rainwater and dirt, thereby lowering the quality of the resin. Another disadvantage is the additional labour required to attach the can to the trees.

5.3.9 Observations on harvesting

Resin was harvested carefully at the end of March 1998. Experimental yields were low and only small quantities of resin had accumulated in the tin cans. A considerable proportion of the benzoin was still on the trees and had not flowed into the cans; this was particularly true using the Malaysian methods. The use of a tin can for collecting the benzoin is unlikely to be practical and the traditional method of collecting it directly from the tree is preferable.

Harvesting was carried out using a forest knife, bamboo basket and, as needed, a rope ladder. The villager removes or digs the benzoin out of the bark using a forest knife and places the pieces of resin in a bamboo basket. In the trials, however, the quantities of benzoin produced were low and the production from the four tapping-height positions on each tree was harvested together. Benzoin from each tree was placed in an individual sample bag to be weighed and the quality assessed (size, colour and purity). These data were entered on a tally sheet.

To harvest benzoin under the Indonesian tapping method a forest knife was used to cut the upper and lower parts of the bark pocket. The bark was then removed and the resin collected.

After recording the yields from each tree, all the benzoin from a particular tapping method was combined and kept separate from that derived from each of the other methods. A single sealed bag containing all of the benzoin harvested under each trial was clearly labeled and sent to the Food and Drug Quality Control Centre in Vientiane where the chemical analysis of the benzoin was carried out. Since France is the principal market for Lao benzoin, there are advantages in following the French Pharmacopoeia monograph for Benjoin du Laos where appropriate. The following analyses were to be done: 1) thin layer chromatography (TLC); 2) loss on drying; 3) alcohol-insoluble matter; 4) total ash; and 5) total acids. Although the TLC is not included in the Benjoin du Laos monograph, it is simple to do and is very useful in comparing the chemical composition of the production under the different tapping systems (see Chapter 8, section 8.1.3 and Appendix 2).

5.3.10 Data analysis

Quantitative and qualitative data derived from the tapping trials were shown in Table 5.5. The results of statistical analysis of the quantitative data are given in Tables 5.6 and 5.7.

Table 5.6 Analysis of variance (ANOVA) of resin yield from the tapping trials

^1/* = significant differences at P<0.05 level

Table 5.7. Duncan’s new multiple range test of yield from the tapping trials

* = significant differences at P<0.05 level

The following observations can be made:

1) Although the replications (tree size) in the experiments had a significant effect on resin yield, the analysis of variance (Table 5.6) shows the significant effect of tapping methods on resin yield. Clearly, the different tapping methods result in different quantities of benzoin being produced.

2) Table 5.5 shows that the best tapping method in terms of the number of tapping cuts which produced resin was the Standardized Traditional Indonesian Method (Type 7). Of the total of 80 tapping cuts, 56 (70%) were found to have resin. The next best methods were the V-shaped Method (Type 8), 34 cuts (43%) and the Lao Method A (Type 5), 31 cuts (39%). All four Malaysian methods gave a poor response to tapping, 9-28%.

3) The results obtained for total resin yield (Table 5.5) by tapping method correlate with the number of tapping cuts which produced resin. The highest yield was from the Standardized Traditional Indonesian Method (Type 7), and amounted to 102.3 g. This was followed by the V-shaped Method (86.0 g) and the Lao Method A (65.7 g). Of the four Malaysian methods all but one, i.e. the Malaysian D (Type 4), produced very little resin. It should be noted however that there was a large variation among the 20 trees within each tapping method and care should be taken in interpreting the results. Nevertheless, the Indonesian, V-shaped and Lao A methods are clearly the best in terms of quantity of benzoin produced. Any one of these three tapping methods could be adopted to improve production in Lao PDR.

4) Given that a number of trees in the experiments yielded no resin at all, comparing the mean differences among the eight tapping methods may not give clear results. However, analysis of the means does confirm that the Malaysian tapping methods as a group yielded less resin than the other methods. Only the Malaysian Method D (Type 4) gave a reasonable yield although, in fact, there was only a small amount of resin in the tapped area; most of the resin came from beyond the cuts under the bark which had been beaten when the cuts were made. Nonetheless, it is clear that as a group the Malaysian tapping experiments were the least productive.

5) In the Malaysian tapping experiments, making the tapping cuts into the wood rather than just into the bark had no significant effect in terms of resin production. There was no difference in resin yields related to the depth of the tapping cuts. This confirms that resin is secreted from the bark alone.

6) Beating the bark around the tapping cuts did not stimulate sap flow or increase resin yield. In fact, this treatment had an adverse effect as shown by comparing yields between the Malaysian A (Type 1) and Malaysian B (Type 2) and between the Lao A (Type 5) and Lao B (Type 6). It is possible that the bark beating was excessive and caused too much damage. It was observed that the bark of these trees was dried out and in some instances new bark was developing and covering the tapping cut. The dead bark in the cutting area produced no resin. However, a more moderate degree of bark beating may be a way to increase resin production.

7) The low resin yields make it difficult to compare the differences in quality (size, colour and purity) among tapping methods. Nevertheless, it appears that the size of the resin drops was dependent on harvesting techniques rather than tapping techniques. Resin harvest is a tedious task and there is a high incidence of breaking the resin drop when it is removed from the tree. Visual observation and analysis of the data in Table 5.5 suggest that there are no significant quality differences among the eight tapping methods.

5.3.11 Preliminary trial to increase yield

About 1-2 months after the initiation of tapping, a study of the characteristics of resin flow was carried out by observing each tapped area. At that time, some trees tapped by the V-shaped Method (Type 8) were harvested to increase the trial yield.

Results of the study to increase the production are shown Table 5.8 and the analysis of variance (ANOVA) in Table 5.9.

Table 5.8 Benzoin yield from experiments to increase resin production in the V-shaped tapping method trial (grams)

Table 5.9 Analysis of variance (ANOVA) of yield from experiments to increase resin production in the V-shaped tapping method trial

^1/ns = not significant differences at P<0.05 level

The experiment showed that removal of accumulated resin after 1-2 months, as compared to leaving the secreted resin in place for harvest at the end of the tapping season, was not significant in terms of overall benzoin yield. Nevertheless, visual observation did reveal that some new resin was secreted after removing the pieces blocking the tapping cut and cleaning it, indicating that it may be possible to achieve some increase in production by this practice. At the very least this may mean that it is possible to harvest some hardened resin after 1-2 months and the remainder at about 5-6 months. It remains to be seen if it would be efficient to harvest benzoin more than once from a tapping.

5.3.12 Recommendations

1) The tapping experiments demonstrated clear differences among tapping methods. Three methods - the Indonesian, V-shaped and Lao A - all showed satisfactory results in terms of resin production. It was not possible, however, to determine the optimal tapping method among them. Other factors such as the time required to tap and ease of application were not assessed but also must be taken into account. It is recommended that testing of the Indonesian, V-shaped and Lao A methods be repeated, taking into account factors such as the time and ease of application.

2) Tin cans should not be used with the V-shaped Method.

3) The size of the V-shaped tapping cuts should be reduced.

4) As noted previously, the overall yield of resin in the tapping trials was low compared with that observed on nearby non-experimental trees tapped by farmers. Undergrowth in the trial area was removed to facilitate access. Cutting of the undergrowth vegetation below the styrax trees exposed them to more direct sunlight and heat, and this may have caused the tapping cuts to dry out. It is recommended that the effect of undergrowth clearing be investigated.

5) Trying to stimulate sap flow by beating the bark around the tapping cut should be re-examined. In order to avoid severe damage to the bark, which appears to be detrimental, rubber hammers could be used to gently beat the bark.

6) It was observed that removing resin from the tree 2-3 months after tapping resulted in new flow of the sap and an increase in resin yield of some trees. Thus, it may be possible to promote new resin flow by removing the resin already formed 2-3 months after tapping by the V-shaped Method.

7) There is some uncertainty with regard to the optimum time of resin tapping. Discussions with some benzoin collectors indicated that early tapping (in July) is best suited for large trees while late tapping (in August-September) is good for small trees. Some consideration should be given to this factor.

8) If sustainable yield from styrax trees is to be achieved, it is necessary to study the optimal number of tapping cuts per tree which do not cause serious harm to the trees and yet assure that tapping can continue for successive seasons. In addition, a tapping rotation that provides optimal yields should be determined.

9) The orientation aspect of the tapping cuts on the tree may influence yield, due to the effects of sunlight and leafiness of the tree. One side of the tree may be leafier than another and the exposure down-slope may be different from the exposure up-slope. These site factors of individual trees may influence their resin production and should be examined in any further trials.

The results of the additional studies carried out in 1999 and 2000 have given some answers for the above recommendations, Nos. 1, 4 and 5. They are briefly explained in Appendix 5.

Photo 5.1 The tools used in benzoin tapping and harvesting operations by the villagers in Ban Kachet.

Photo 5.2 Benzoin tapping operation with the traditional Lao method in Ban Kachet.

Photo 5.3 Resin flow on the stem of a styrax tree tapped by the Standardized Traditional Lao Method (Type 5).

Photo 5.4 Indonesian tools used in benzoin tapping.

Photo 5.5 Malaysian Method and resin flow.

Photo 5.6 Indonesian Method and resin harvesting.

Photo 5.7 V-shaped Method and resin flow.

Photo 5.8 Harvesting benzoin from a notch under the Standardized Traditional Lao Method.