The previous chapter outlined the methods of determining when to collect seed and from which trees. The present chapter describes the various methods available, both manual and mechanical, for the actual operation of collecting seed from a given tree. Although the term “seed collection” is a convenient one in common use, it should be noted that almost invariably it is the fruits which are harvested from the trees. Only at a later stage in some species are the seeds extracted and the fruits discarded; in other species seed extraction is omitted and fruits are sown in the nursery complete with the one or more seeds which they contain.
There is a great variety of methods and equipment available for collection of fruits and the choice depends on a number of factors which, following Robbins et al. (1981), may be summarized as follows:
Relative size and numbers of the natural dispersal units and of the units which can be conveniently collected by man. In the case of 1 – 3 large seeds inside a dehiscent or indehiscent fruit (e.g. Aesculus, Tectona), collection can be done most easily by awaiting natural fall of seed or fruit and collecting from the ground. At the other extreme collection from the tree of fruiting heads of Adina cordifolia at 200 per kg is the only practicable way to collect the seeds; at 11 million per kg, it would be impossible to collect them after dispersal (Campbell 1980).
Characteristics of the fruit: size, number, position and distribution of fruits; resistance of peduncles to shaking, pulling, breaking or cutting; interval between ripening and opening.
Characteristics of the tree: diameter, shape and length of bole, bark thickness; shape of crown; size, angle, density and resistance to breakage of branches; density of foliage and depth of crown.
Characteristics of the stand: distribution and stocking of trees (e.g. isolated trees, open or dense stand); density of understorey and ground vegetation).
Characteristics of the site: slope, accessibility.
The various collection methods may be classified into the following: (a) Collection of fallen fruits or seeds from the forest floor, (b) Collection from the crowns of felled trees, (c) Collection from standing trees with access from the ground, (d) Collection from standing trees with access by climbing and (e) Collection from standing trees with other means of access.
Collection from the forest floor of fruits which have fallen after natural ripening and abscission is common practice with a number of large-fruited genera. It is cheap and does not require as highly skilled labour as, for example, climbing; school children or casual labour may be used. Fruit size is very important as the larger the fruit, the easier it is to see and pick up by hand. Temperate genera commonly collected from the ground are Quercus, Fagus, Castanea and tropical genera include Tectona, Gmelina, Triplochiton and several genera among the dipterocarps.
The main disadvantages of collection from natural fruit shedding are the risks of collecting immature, empty or unsound seeds, of seed deterioration or premature germination if collection is delayed, and uncertainty in identifying the mother trees from which seed is collected. Seeds in the first fruits to fall naturally in the season are often of poor quality (Morandini 1962, Aldhous 1972). In Thailand shedding of teak fruits starts in March, but observations have shown that the most viable fruits are shed in the latter part of the season, so collection is usually postponed until April (Hedegart 1975). Clearing the forest floor of vegetation and debris, including old or prematurely fallen fruits, and/or spreading out sheeting of light canvas, calico or plastic, to catch the seed, can greatly facilitate collecting efficiency (Turnbull 1975 b). If carefully timed, this operation will also eliminate much of the risk of collecting empty or non-viable seed. Sound fruits should be gathered as soon as possible after they have fallen, to avoid damage or losses from insects, rodents or fungi and premature germination. This is of particular importance in the moist tropical forest. Observations have indicated that many of the seeds of the more important dipterocarps lose their viability within a few days of shedding and studies on Shorea platyclados in Malaysia demonstrated that seed lots collected from the ground included considerably more defective seeds than lots collected from the standing tree (Tang 1971). Collection from the ground must, therefore, be perfectly timed with seedfall.
In the Jari region of Amazonia in Brazil, Woessner and McNabb (1979) found that collection of green or yellow fruits of Gmelina arborea from the forest floor gave the best results in operations for collecting about 10,000 kg of seed a year. They could be stored temporarily in sacks during transit from the field to the fruit processing depot, without serious loss of viability. Older brown or black fruits ferment and heat in the sacks and rapidly lose viability. Collecting teams are instructed to collect only the fresh green and yellow fruits. 50 kg of fruits can be collected per man in an 8 hour working day and yield about 3 kg of dried stones. Similar results have been obtained in Malaysia where green and yellow fruits collected from the ground gave over 90 % germination, but brown fruits, on the other hand, produced only 53 % (Mohammad and Ibrahim 1980).
Seeds of some hard-coated species may remain viable on the forest floor for years, especially in temperate conditions. In Hungary seed of Robinia pseudoacacia is collected from the forest floor under 30-year-old stands in the Pusztavacs forest district (Keresztesi 1979). A special machine screens the top 10 cm of soil and yields about 770 kg of seed per hectare, which is the equivalent of the yield of approximately 10 seed years. Even in the tropics viable hard-coated seeds may be obtained by screening the soil below the mother trees. This has been done in Malaysia for Parkia javanica and Intsia palembanica of which the seeds are large enough to be picked up by hand. Where the seeds are smaller e.g. in Albizzia falcataria, sieving with a wire mesh may be more practical (Ng 1983).
The identity of the mother tree is often uncertain when fruits are collected from the ground. Isolated trees present no problem in this respect (though they may be undesirable parents because of the risk of selfing), but much mixing of fruits can occur in dense monocultures with interlocking crowns. This is of no concern in collecting commercial quantities of seed, provided that the genetic quality of the stand is average or above average. For research and breeding purposes, it is often necessary to maintain the identity of the mother tree of each seed lot. In such cases it is advisable to clear the grond of already fallen fruits and to accelerate the fall of new fruits by shaking, beating or cutting off branches, or climbing and picking fruits in the crown (Hedegart 1975). A compromise solution, suitable for commercial collections in unimproved stands containing a mixture of good and bad phenotypic trees, is to collect fruits only below the better seed bearers and within half the radius of projection of their crowns.
If fruits are easily detached but natural fruit fall is insufficiently concentrated in time, fruit fall may be induced by artificial means. Trunks of small trees and low branches may be shaken directly by hand. Higher branches may be shaken by means of a long pole and hook or by a rope. This method has produced good results in Cordia alliodora and Cedrela spp., as it facilitates rapid collection of seed with good viability as soon as visual inspection shows that the fruits are mature (Stead 1979, Robbins et al. 1981).
Use of a rope involves an initial operation to pass the rope over the branch to be shaken, which is described by Robbins et al. (1981). The same method is used to hoist a saw or pulley into the crown. A thin line is attached to a weight, which is projected over the branch by hand or by catapult. For higher branches the line may be attached to an arrow, which is shot from a bow, or to an iron rod shot from a calibre .22 rifle. A light nylon line such as a fishing line of 50 lbs. (23 kg) breaking strain is suitable and the weight or projectile used should be heavy enough to drop to the ground pulling the line with it over the branch. Care must be taken to ensure that the line unreels readily without getting entangled, for example by using an appropriate fishing reel. Once the end of the line has reached the ground, the weight or arrow can be detached and a nylon cord of 3 – 4 mm attached instead; the line is drawn back over the branch, pulling the cord with it. The two ends of the loop can then be pulled together to shake the branch. The cord should be positioned towards the end of the branch where it will have the maximum shaking effect and not close to the bole where the branch is thickest.
In New Zealand a 30 kg-pull fibreglass long-bow firing arrows 0.8–0.9 m long and 40 g in weight has been used to project a line of 5.5 kg breaking strain over a branch (Sweney and Jones 1975). This is used, successively, to pull up a 20 kg line and a 180 kg line with pulley. In Canada both a .45 calibre gun firing a steel rod of 270 g weight and a .22 calibre gun firing a cylinder of 230–300 g weight and 2 ½ inch diameter have been used successfully up to heights varying from 20–50 m. Blank cartridges were used. The line attached to the projectile was 32 kg monofilament fishing line, which was used to haul up a 320 kg plastic twine carrying a branch breaking or cutting device (Collis and Harris 1973).
Mechanical tree shakers were developed originally for fruit and nut orchards but since about 1965 the technique has been used for certain forest trees, particularly for the southern pines in the USA. (Turnbull 1975 b). The machines are expensive, need flat ground for efficient use, and experienced operators are essential to avoid excessive damage to the trees. Many cones are removed by a few seconds of shaking, but longer shaking breaks off pieces of tops and limbs (Stein et al. 1974). Tree shakers have no role in diffuse collecting operations in natural forest, but will probably continue to be used in intensively managed seed orchards or seed stands of a limited range of species.
The American Shock Wave tree shaker is mounted on a short wheel base truck chassis, equipped with an automatic transmission. It has a padded clamping device mounted on the extreme end of a 6 metre boom capable of clamping the trunk of a tree up to 90 cm diameter. A shake pattern is developed by counterrotation unbalanced weights in the shaker of varying frequency from 400 – 4000 cycles per minute (Kmecza, 1970).
The tree is generally clamped about 3 m above the ground and one 15-second shake is sufficient to remove about 80 percent of the cones from P. elliottii; but P. taeda and P. echinata are more difficult and a good operator may often remove only 25 – 30 percent of the cones after prolonged shaking. Ripe P. elliottii cones require a force of about 2 kg for removal whereas P. taeda cones are detached only by a force of 20 kg or more (McLemore, 1974). An unsuccessful attempt to reduce the force needed to remove the cones of P. taeda by the use of abscission inducing chemicals is reported by McLemore (1973). The repeated shaking of the more difficult trees can cause bark rupture and breakage of the leading shoot (Kmecza, 1970).
With five mechanical shakers the Louisiana Forestry Commission harvested cones from 34,680 P. elliottii trees in twenty days. Three-quarters of the trees released 85 percent of their cones during shaking periods from 6 – 30 seconds. Performance in one hour exceeded that of a climber in a week (Chappell 1968). Results reported by McLemore and Chappell (1973) showed that the mechanical shaking of Pinus elliottii trees by trained operators did not harm future cone production, tree growth or vigour over the following four years.
Mechanical tree shakers are now widely used in the southeastern USA for harvesting seed in seed orchards of pines. In the case of species in which ripe cones can be easily detached, such as P. elliottii and P. palustris, trees are shaken in the period after cones have reached maturity but before they open, and the cones with their contained seeds are collected from the ground. In the case of species with persistent cones, such as P. taeda and P. echinata, shaking is deferred until the cones have opened and the objective is to shake out the seeds from the cones. They can then be collected from the ground by means of the net retrieval system, described on p. 53.
In the U.S.S.R. output from the VUS-2 vibrator working on Pinus sibirica was reported to be 10 – 20 times that obtained by manual methods (Uland 1971). More recent experience with a tree-shaking machine developed in Soviet Central Asia has shown that 90 – 100 % of fruits of Juglans, Malus, Prunus, Fraxinus and Gleditsia can be collected with little stem damage. The machine is a grab-type vibrator mounted on a hydraulically operated arm on the 3-point linkage of a tractor. Optimum shaking time is 10 – 25 seconds and optimum vibration rate for most species 1000 cycles per minute (Kiktev et al. 1977). Italian CECMA vibrator machines, developed primarily for harvesting the olive crop, have also been used successfully for collecting cones of Mediterranean pines.
Although collection from the ground is most often used for fruits, it can also be used for seeds dispersed after the cones or fruits have opened. The seeds of southern pines in the USA, e.g. Pinus elliottii and P. taeda have a very short period between reaching maturity and being dispersed, and a number of methods have been evaluated for collecting loose seeds as they are dispersed. In addition to the use of sheeting spread on the ground, mentioned previously, they they include polypropylene netting round the crowns, funnel-shaped wooden frames covered with cloth or polyethylene and attached to a central hub surrounding the stem, and sheeting or nets raised on poles above the ground. Earlier experience was not very successful, as rarely more than 50 % of the available seed crop was recovered (Turnbull 1975 b). If seed is borne mainly on or near the outside of the crown, much of it falls outside the spread of a single tree catching unit. If sheeting or netting must remain in place for an extended period of natural seed fall, it is liable to get damaged from weather and a proportion of the seeds are lost to birds and animals.
4.1 The Advanced Line Technique (A)-(C) show stages from shooting the advanced line to drawing up the working rope (D)-(F) show possible uses of the working rope, (D) with block and tackle to pull man into crown (E) for branch shaking (F) to sever branches by means of flexible saw. (A.M.J. Robbins)
4.2 The Schaumann Tree Shaker. This is one of a number of makes of tree shaker now on the market. (H.C. Schaumann)
|4.3 Funnel for trapping Acacia aneura seed near Charleville, Queensland, Australia. (FAO/Division of Forest Research, CSIRO Canberra)|
|4.4 Net retrieval machine, Stuart Seed Orchard, Pollock, Louisiana, USA. (USDA Forest Service)|
More recently a net retrieval system, for use in seed orchards in southern USA, has been developed jointly by the Georgia Forestry Commission and the Missoula Equipment Development Center. It shows considerable promise (McConnell 1982) and is increasingly preferred to vacuum harvesters in P. taeda orchards. Netting used is a polypropylene plastic fabric manufactured for carpet backing. It is light, durable and available in a range of dimensions. For Pinus taeda a width of 16.5 ft (5m) and a weave count of 6 × 8 per square inch (approximately 2 × 3 per cm2) is used (Anon. 1982, Edwards and McConnell 1983). If carefully handled, the expected life is 10+ years. Netting is laid in the orchard several weeks before seed fall and trees are shaken by mechanical shaker to dislodge seeds from the cones. The power take off from a wheeled tractor provides the power (less the 30 h.p.) needed for (a) Mechanical winding of the net onto a roller and (b) Mechanical separation of seed from the twigs, leaves and cones which also fall to the ground as a result of the shaking operation. Care must be taken in separating the netting from the grass blades which tend to go through it, before starting to wind in the netting.
Gathering of fruits on the ground is usually done manually but may be assisted by using a simple hand tool, such as a long-handled rake with interchangeable heads having different numbers of, and spacing between, tines. Attempts have been made to develop mechanical or vacuum sweeper methods to pick up seeds or fruits. Tests have also been made of a mechanical harvester, with the sweeping action of a rotating drum fitted with a myriad of attached rubber fingers which pick up seeds with separation from foreign debris. These types of machine are best used in conjunction with a tree shaker, which ensures that a substantial quantity of seeds are on the ground at each sweeping operation.
Mineau (1973) described the successful use in France of a vacuum sweeper type of machine, operated by compression from a tractor engine, for collection of Fagus fruits. The machine is compact and weighs 450 kg. A Dutch vacuum seed harvester has been used successfully for the collection of Quercus acorns and is reported to be a cheaper method in the Netherlands than either hand-picking or the use of a tree shaker and tarpaulins (Arts and Kofman 1980).
In the USA, Hallman (1981) summarized the advantages of the vacuum sweeper as: it
Extends the harvesting season from about 2 weeks to 2 months.
Eliminates the need for ladders and lift trucks, permitting orchard managers to let their trees grow taller because no climbing is involved, therefore extending the useful life of the trees.
Reduces collection costs compared to hand collection.
The disadvantages of the harvester are that:
The orchard floor requires extensive preparation for the machine to operate well.
The harvester is noisy and produces large quantities of dust.
It does not operate well when the ground is wet.
The harvester has had a number of mechanical problems that have been largely corrected, but minor design changes still need to be made.
The disadvantages are now considered to outweigh the advantages, and the net retrieval system, described on p. 53, is preferred for collecting P. taeda seeds in orchards in the southern USA.
In view of the capital cost of this type of equipment and the emphasis placed on the immaculate preparation of the seed orchard floor which is needed for its operation, its use in developing countries is likely, especially if social considerations favour the use of labour-intensive manual methods as a means of increasing employment.
Animals sometimes gather together cones or fruits as a food supply and these caches may be raided for the seed, but this source of seeds is confined to limited areas. Squirrel caches are an important source of coniferous seed in western North America. Squirrels usually locate their caches year after year in the same places. Typically, they are found in damp areas near springs, small creeks or marshes, on northern exposures, and in decayed wood or duff or around old fallen trees. A single cache may contain from a few cones to many bushels. Fresh cones on the ground are a sign of squirrel activity; piles of cone scales and cores may indicate a nearby cache (Stein et al. 1974, Dobbs et al. 1976). Caution should be exercised in collecting seeds or cones from caches, because of the danger of infestation by pathogenic fungi which may reduce germination (Sutherland 1979).
Ants sometimes gather seeds together and in North Africa they have been observed to accumulate large piles of Acacia seeds (Turnbull 1975 b). Any seeds collected from rodent or insect caches should be tested for soundness by cutting test or other means.
One method of collecting large amounts of seed is to synchronise it with normal commercial fellings carried out during the seed ripening season and to collect seeds or fruits from felled trees (Morandini 1962). If fruits are to be collected from throughout the felled crop, picking should for safety reasons be postponed until felling in the area is complete (Douglass 1969). If phenotypic quality of parent trees is more important than quantity of seed, it is preferable to select, mark and, if possible, fell and harvest fruits from superior mother trees in advance of the main felling. In Pinus radiata plantations due for clear-felling in New Zealand, a method has been used whereby a trained forest officer selected and marked the best 8 – 13 stems per hectare and the seed collection gang felled and trimmed the trees and collected the cones, so as to leave no obstructions for the subsequent felling of the remaining trees (Turnbull 1975 b). Collection of fruits from early thinnings should be avoided, since it is difficult to judge phenotypic quality correctly at that age. Felling crowns into existing gaps is advisable in order to facilitate recovery of cones (Dobbs et al. 1976). It is essential to confine collection to the season when seeds are mature; adjustment of felling dates to coincide with seed ripeness should be possible wherever the same authority is responsible for both the felling and the collecting activities, e.g. national forest services operating within state forests. Hand picking of cones or fruits in the fallen crowns is common practice, assisted by rakes, hooks or machetes. Small cluster-type cones, such as those of Thuja and Tsuga, may be harvested by cutting off the cone-laden branch tips and pulling them through a cone stripper (Douglass 1969). The stripper contains a series of teeth, similar to a rake, which are set sufficiently close together to remove the cones.
In practice collection in clear-felled areas has proved little if any cheaper than collecting from standing trees by a well-trained team of climbers, at least in north-temperate conifers (Dobbs et al. 1976, Barner 1981). The tangle of fallen stems and crowns and the dispersal of some cones during felling greatly reduce productivity. Where operations are speedy and closely controlled, collection after the boles have been trimmed and removed but before the lop and top has been piled and burnt may prove the most efficient method.
Felling of selected individual trees specifically for seed collection may be necessary in areas where commercial fellings are not practised, for example when relatively small quantities of seed from a few trees are needed for provenance testing or other research purposes. Such special fellings should be avoided whenever possible, both because the bole is wasted and because the tree is lost as a future seed source, but they are sometimes inescapable in the case of tropical high forest species which are very difficult to climb and if a seed collecting expedition is severely limited in time. Felling tall but unbuttressed trees is usually a lot quicker than climbing them.
The collection of fruits from wind-thrown trees is generally undesirable, as little selection can be applied and there may be a bias towards trees with characteristics which pre-dispose them to wind damage (Turnbull 1975 b).
In the case of shrubs or low-branched trees, fruits can be picked directly from the branches by the collector while standing on the ground (Morandini 1962). Examples are Crataegus, Sorbus and Ilex spp. in temperate zones (Aldhous 1972), the smaller acacias and mallee eucalypts in Australia (Turnbull 1975 b) and many of the small drought-resistant species of the arid and semi-arid zones. Smaller fruits are generally harvested directly into a basket, bag, bucket or other container held or worn by the picker (Stein et al. 1974).
For branches out of arm's reach a variety of long-handled tools is available to enable the collector to reach the fruits from the ground. A pole and hook may be used to pull branches down within reach. Long-handled rakes, saws, chisels, hooks or pruning shears are used to pull off or sever individual fruits or fruit-bearing branchlets. Light rigid bamboo, aluminium or plastic poles 4 – 6 m in length are common. In order to reach beyond the 6 – 8 m range of single poles, multistage telescopic poles with a shear on the end have been developed (Turnbull 1975 b). Robbins et al. (1981) have noted that, in some species, fruits or cones on the lowest branches may yield little seed, because of lack of pollination in that position, and that it is therefore preferable to collect fruits from at least half way up the crown. Ability to use long-handled tools efficiently from the ground is much affected by the density and form of the crown in individual trees.
4.5 Use of vacuum seed harvester for acorns in the Netherlands (A) Collection from the ground (B) Discharge of acorns into sack. (R.B.L. De Dorschkamp, Wageningen)
4.6 A selection of Acacia seed collecting equipment used in Australia. From top left: Plant press with specimen and tags, small bag containing clean seed, large collection bag, 2×2 m collection sheet, flexible saw, leather gloves, bow saw, secateurs, fine sieve with bottom pan, large sieve, throwing rope with weight. (FAO/Division of Forest Research, CSIRO Canberra)
4.7 Saws, pruners, rakes and other hand tools for harvesting tree fruits. (A.M.J. Robbins)
A rope can be thrown or pulled over a branch as already described, but used to break off the seed-bearing branch rather than to shake it. A thicker rope is needed than for shaking. The method is not recommended for general use. It damages the tree, allows access to pests and diseases and, in the case of pines and other species which take two years to mature their seeds, destroys the next year's seed crop while collecting the current year's.
Several types of flexible saw have been used successfully to sever branches from the ground. One model, described by Anon. 1979, consists of a 3 ft. long flexible cutting cable fitted with precision-set carbon steel teeth and two 35 ft. polypropylene control lines. A sand-filled safety weight is used to project one of the control lines over the branch. An earlier model, the “commando saw”, now no longer in production, was effective in servering eucalypt branches in Australia (Boden 1972). Two operators could bring down branches up to 20 cm in diameter quickly and easily.
The method is not applicable to trees with acutely angled branches such as E. tereticornis. The other limitation depends on the efficiency of projecting the line over the desired branch.
Rigid saws can also be used to sever branches. Sweney and Jones (1975) describe a method used in New Zealand in which a pruning saw or bow saw is attached by lugs to a 180 kg line running through a pulley previously raised into the crown. The pruning saw is used for small branches <2 cm diameter, while the bow saw will cut through a 10 cm branch in 5 minutes' sawing.
Another method of severing seed bearing branches is to shoot them down with a large calibre rifle. The method was successfully used to shoot out the tops of Picea glauca trees in seed production areas in north eastern USA (Slayton, 1969). Not only was the topping of the trees found to be less expensive than climbing but the cones could also be collected at the best stage of development because of the short time in which the operation could be completed. More recently shooting off branches or tops from a helicopter has yielded promising results in Canada.
In Australia the collection of small samples of eucalypt and Araucaria seed from tall trees has been accomplished efficiently using a .222 or .243 or .308 calibre rifle with x4 telescopic sights (Green and Williams 1969, Boland et al. 1980). Branches up to 15 cm diameter could be brought down. “Pointed soft point” ammunition is more effective than “hollow point” when used with a .308 rifle.
A disadvantage of the rifle method is that very strict safety precautions must be observed. There are limitations to where a rifle may be used, for example not near roads or built-up areas. Also crowns of some species such as Araucaria and Picea may be considerably damaged by this technique.
In shooting down branches it is usually necessary to steady the rifle on a tripod or to rest the stock against a tree or the side of a vehicle (Turnbull 1975 e). A clear line of sight is required and this can be a limiting factor in dense forests. It is usually best to shoot at right angles to the branch and to sever the bark on the underside with the first shot to avoid branch hang-ups. The bark on the upper side is then cut and finally shots are placed at intervals across the branch. It is important to select branches which will fall unobstructed to the ground. Horizontal branches are more readily detached than ascending branches. The shots should be positioned to take advantage of branch leverage. The method is best suited for collecting research quantities of seed from a heavy seed crop clustered on branches or tops too inaccessible to be conveniently reached by other means.
There is a limit to the height to which long-handled tools can be used for collecting seeds or fruits from the ground. Near that limit the operation consumes much time and energy but produces little seed. For tall trees which cannot be felled, therefore, climbing is often the only practical method of collecting. Some men are excellent natural climbers, while good training and good equipment can render collection by climbing an efficient and safe, albeit energetic, operation. For convenience the operation may be described under the following subheads: (a) Climbing into the crown by way of the bole, (b) Climbing into the crown directly, (c) Climbing and picking of fruits within the crown.
Climbing with minimum equipment. Climbing without mechanical aids is practised in a number of countries (Hans 1973, Bhumibhamon 1973). In the Philippines some seed collectors climb barefooted or with the help of a rope which ties both feet together and presses them against the trunk of the tree (Seeber and Agpaoa 1976). Other modifications are for the climber to cut successive notches in the bole with a hand-axe to support his feet, or to hammer in a series of iron spikes about 20 cm long which are later withdrawn for re-use as he descends. Both of these methods are physically exhausting, whether or not a safety belt is used, and do some damage to the tree. Climbing tall branchless boles with hands and feet involves a considerable safety hazard and the risks may tempt climbers to prefer collecting from the most easily climbable trees which are often silviculturally the least desirable. It is preferable to introduce one or other of the special climbing aids now available.
Climbing irons or spurs, which are attached to the climber's boots, offer a light and inexpensive means of safer and more efficient climbing, if combined with safety belt, strap and line, safety helmet of glass fiber and heavy leather gloves. The lightness of the spurs (less than 1 kg a set) makes them particularly suitable for use in inaccessible stands in roadless country, where all equipment must be carried on foot. They have been found to be the most efficient method for climbing trees of Pinus kesiya and P. merkusii in Thailand (Granhof 1975) and for P. caribaea and P. oocarpa in Honduras and are in common use in many countries, especially for conifers (Robbins et al. 1981).
There are a number of different types of climbing irons but basically they consist of a forged iron arm and connecting piece which terminates in a pointed spur. The iron must be fastened securely by a leather strap to the foot gear and sometimes to the leg of the climber. The spur may be of varying length but it is an advantage if the point does not extend beyond the sole of the boot, so that the climber can walk on the ground without difficulty (Morandini 1962, Turnbull 1975 b). The optimum length of spur depends on the type of bark. 5 cm spurs are suitable for barkless telephone poles and thin-barked trees and are recommended for most species in Canada, while 9 cm spurs are better suited to species with soft, thick bark (Yeatman and Nieman 1978). Climbing irons should not be used when the bark is frozen and are not particularly safe on scaly bark (Morandini 1962, Stein et al. 1974).
Detailed guidance to the fitting, use and maintenance of treeclimbing spurs in Canada is contained in Yeatman and Nieman (1978). The following description of climbing with spurs closely follows their account. The climber ascends the tree using a safety belt, with a safety strap or safety chain passed around the stem and hooked to the belt. A safety line is tied to the belt and two or more carabiners are clipped onto one of the belt rings. When climbing the stem, the climber must ensure that the spikes are well into the wood of the tree by keeping the knees out from the stem when setting the spur. The lower leg and ankle must be kept at a fair angle to the stem to prevent slipping and gouging the bark. The weight is kept on the feet spaced 15 – 20 cm apart and the centre of gravity away from the stem. The hands and arms are used to balance by holding the safety strap firmly in both hands, rythmically pulling the body towards the tree, moving the strap as the weight on it is lifted and tightening it in the new position as the body moves back. The pull on the safety strap is from the arms in ascending and it should not be transferred to the safety belt except when the climber is in a resting position. When the safety strap is tight, each foot is moved in turn and the weight transferred to the other foot. The safety strap is never unclipped except to bypass branches too heavy to break off. A second safety strap or carabiner with safety rope should be fastened above the obstructive branch before the first strap is unclipped. When sound branches are reached, preferably at the bottom of the live crown, the safety line is passed through a carabiner fastened by rope above the first branch, the safety strap is unclipped, and the climber works his way into the live branches.
The main disadvantage of spurs is the damage they do to the bark, particularly of thin-barked species. If climbing is only occasional, this should not be excessive, but frequent climbing of the same tree, e.g. for pollination and seed collection in seed orchards, is liable to cause an unacceptable degree of damage; other climbing methods should then be preferred.
Ladders. For heights from about 8 to 40 metres, vertical scaling ladders in several sections provide a safe and convenient means of climbing the bole to the live crown. They can be made of a variety of materials including wood, aluminium, magnesium alloy etc., but each section must be light enough to be easily pulled up by the climber. The legs of the bottom section can be placed on adjustable platforms for greater stability (Morandini 1962, Turnbull 1975 b). The length of each section varies between 1.8 and 3 m and its weight should not exceed 3 – 4 kg.
|4.8 The High Limb flexible chain saw (A) in operation (B) close-up. (Green Mountain Products Inc.)|
|4.9 Tree climbing spurs (A) strapping on (B) climbing. (Canadian Forestry Service)|
|4.10 Two strut sectional ladder in use in Canada (A) Preparing to pass the chain around the tree to secure the top of the first section (B) Dismantling the ladder, with climber suspended on a safety line. (Canadian Forestry Service)||4.11 Single-strut sectional ladder used in Denmark. (DANIDA Forest Seed Centre)|
The bottom one or two sections of the ladder are set up parallel to the tree stem with the bracket at the top against the trunk. The climber ascends with his safety strap around both the trunk and the ladder until his shoulders are level with the top of the ladder and then fastens it to the trunk by a rope or chain (Yeatman and Nieman 1978). Subsequent sections are pulled up by rope and fitted into the section below. Each section is climbed and fastened to the tree in turn. The same procedure is used for climbing from bole into crown as described above for climbing irons. With the lighter sectional ladders the climber can carry two sections, each 2 m long, attached to his safety belt. If the bottom two sections of 3 m each are fitted together and raised into position from the ground, this means he can erect a total of 10 m before needing to use the tool line to haul up additional sections.
Sectional ladders may be designed as “one-legged” or “two-legged”. Two-legged are more common. The “one-legged” ladder comprises a central support with small bars fixed as rungs alternately on either side and is attached by chain or rope to the tree. The central support is usually made of steel or wood, so these ladders are not very different in weight from “two-legged” types. They have the advantage of being easier to lodge on uneven ground and they are also more easily manoeuvred between the branches (Morandini 1962) and on very sinuous stems.
Sectional ladders can be used without any risk of damage to the tree. They can be awkward to handle in stands with dense canopy or undergrowth and are much heavier to carry than climbing irons, especially if long clear boles impose the need for many ladder sections. They are also more expensive. They are therefore of limited use in inaccessible roadless country, but are ideal in seed orchards or plantations in flat topography.
The Swiss tree bicycle or “Baumvelo” is a device for climbing tall straight trees which are branch-free to the live crown. It is lighter to transport than sectional ladders but heavier than climbing irons. It does no damage to the tree. It is suitable for use on stems with diameters ranging from 30 – 80 cm (Yeatman and Nieman 1978). Olesen (1972) found it very useful for climbing pine trees in Mexico. In the UK it was found particularly useful for conifer species with large cones e.g. Pinus, Picea, Pseudotsuga, in which the collector seeds to move from branch to branch to pull off the cones, rather than remaining for long in the same part (Seal et al. 1965). Its use in that country is now, however, restricted mainly to research collections, since the increased area of mature plantations allows bulk seed collections to be made easily from felled trees and ladders are more convenient for seed orchard collections.
2. Foot support
3. Vamp strap
4. Instep strap
5. Strap tightener
7. Rubber pad
|4.12 Tree bicycle, tree gripper or baumvelo, showing parts. (H. Schneebeli & Co.)||8. Hinge head|
9. Hinge pin
10. Coil Spring
11. Leaf Spring
12. Holding Device
13. Locking Lever
14. Steel Band
|4.13 Tree bicycle in use, with safety harness, helmet and ropes. (British Forestry Commission)|
The tree bicycle contains two separate units, one for each foot. Each unit consists of an arm (longer in the upper, shorter in the lower unit) to which is fixed a rubber supporting block which rests against the trunk. The lower end of the arm carries a stirrup or pedal with strap and quick release clips, which holds the climber's foot. The upper end is attached to a steel band forming a circle of adjustable diameter around the stem. The tree bicycle is used in conjunction with safety harness or belt, support chain or strap, safety line, safety clips or carabiners and nylon ropes.
Operation of the tree bicycle is well described by Seal et al. (1965) and Yeatman and Nieman (1978). The steel band should not fit too tightly round the stem, which would hinder them sliding upwards. They will grip properly as long as the toe of the climber's boot does not touch the trunk when his full weight is on the stirrup; when that happens it is necessary to unclamp, shorten the loop and reclamp the band on each foot in turn. After securing the bands round the base of the tree, the climber fits his feet into the stirrup, closes the quick-release clips and fastens the straps. He also passes his safety strap or chain round the stem, adjusting its length in accordance with stem taper. The climber ascends, putting his weight alternately on one or the other stirrup and lifting in turn the free foot to raise the loosened band. He pauses to adjust the bands, one at a time, to allow for the taper of the tree. Obstructing branches must be pruned flush with the stem as they are encountered.
The climber continues to ascend until the upper steel band meets the lower living branches of the crown. He then reaches into the crown to fit a nylon safety rope to hold the safety line and proceeds to “park” the tree bicycle. The essential operation is to tighten the lower band of the bicycle so that it grips the stem tightly even when there is no weight on it; there is then no risk of the bicycle slipping down the stem out of the climber's reach. The climber opens the ankle clips on both stirrups, frees his feet from the straps, unhooks his safety strap and climbs into the crown.
The tree bicycle provides an extremely safe means of climbing straight branchless trees without damaging them and is lighter and more portable than sectional ladders. Some practice is needed but most men become competent and quick in its use within a few days. Its main disadvantages are the cost, the fact that its use is limited to a certain range of diameters and that, unlike ladders and climbing irons, it requires the bole to be pruned of branches all round the circumference up to the living crown (Robbins et al 1981). Where regular climbing of the same trees is foreseen, however, as in seed stands or seed orchards, the cost of thorough initial pruning is fully justified. It is advisable to work always with two tree-bicycles within call of each other, because a man in difficulties on a tree at a height greater than can be reached by a ladder can only be reached on another tree-bicycle (Seal et al. 1965), or by climbing irons.
4.14 Hand picking Larix cones in Britain. Note use of safety line and anchorman and tree bicycle “parked” at base of crown. (British Forestry Commission)
Ladders. Access to stout lower branches in the crown may be obtained directly from the ground or by ladder, provided that the branches are not too high. Free-standing domestic step-ladders or taller tripod ladders have the advantage that they do not need to be rested against the tree; they are awkward to handle in dense stands but are suitable for collection in seed orchards or heavily thinned plantations where trees are widely spaced. Tripod ladders up to about 6 m are available but must be guyed with ropes on each side for stability (Yeatman and Nieman 1978).
General purpose ladders are available in wood or aluminium alloy and may either be constructed as a single unit or may be extending, when they consist of two or more sections constructed so that the height may be varied by a relative sliding movement of the sections (Seal et al. 1965). Single-section ladders designed for fruit-picking have a splayed base fitted with moulded rubber feet or metal spikes to give a firm grip on soft ground and can be used to heights of 8 – 11 m. The Finnish Tarra-tikkaat ladder, designed specially for forestry, is similar but incorporates an aluminium ring which slides up and down the ladder, can be attached to the climber's belt and locks automatically if the climber should fall. It also includes a strut attached to the ladder which grips the stem and maintains a distance of about a meter between the bole and the top of the ladder. This enables the picker to reach further out into the crowns of small trees of species such as Cupressus which bear fruits near the ends of the branches. General purpose single-section ladders extend up to about 11 m, while doublesection extending ladders extend to about 14 m. They may be leaned against a stout branch or against the bole for direct access to the crown. The top must be made fast to the tree with a nylon rope and a tall ladder must be further steadied with two guy-ropes. Depending on species and crown form, the climber may leave the ladder and climb into the crown, using safety belt, safety line and nylon safety ropes as from the tree bicycle, or he may collect fruits while standing on the ladder; in the latter case he should secure himself to the ladder by means of a nylon safety rope, while foot fatique can be reduced by a movable foot stand that can be hooked on to a convenient rung (Seal et al. 1965).
The larger and heavier ladders need a vehicle for transport between stands. Extension ladders mounted on trucks can be used to reach crowns of up to 20 – 25 m, but the lack of manoeuverability restricts the vehicle to roads or very flat ground (Turnbull 1975 b). A light alloy ladder mounted on a tractor is described by Morandini (1962); it will reach to 14 m and the tractor can be used in forests without roads. In the USA a magnesium extension ladder mounted on a halfton 4-wheel truck, can be used with safety to 9 m. Sway from the vehicle suspension is eliminated by the use of four mechanical jacks attached to the support posts of the ladder platform rack (Rietveld 1975).
Ropes and hoisting equipment. Access to the crown can be achieved by suspending a rope, rope ladder or hoisting equipment from a stout branch. The same methods for projecting a thin line over the branch (throwing, catapult, shooting arrow) are used as when using a rope to shake branches (described on page 50). Because a stronger and heavier rope is needed to support the climber's weight than to shake branches, it is necessary to pull up the rope in three stages (1) Initially a light nylon line of 50 lbs. (23 kg) breaking strain which is used to pull up (2) A nylon cord of 3 – 4 mm diameter, which is used in turn to pull up (3) A nylon rope of 13 – 18 mm diameter, strong enough to carry the climber (Robbins et al. 1981).
Rope ladders have been used with particularly successful results in Czechoslovakia (Matusz 1964). They may be up to 30 m long and weigh about 20 kg. Wooden rungs are set 30 cm apart.
Hoisting equipment involves the use of a block and tackle which are hauled into position and secured by tying the rope firmly at the base of the tree. The collector is hoisted into the crown of the tree on a small bosun's chair or climbing saddle by one or two men on the ground or with the aid of a mechanical or electric winch (Strickland and Peters 1961, Matusz 1964). The method has an advantage over climbing irons or ladders because the ascent is less tiring and so reduces the risk of accidents brought on by fatique.
Tree net. Devices such as the rope ladder and hoisting equipment give access to the interior of the crown. Some genera such as Cupressus, Chamaecyparis, Tsuga and Thuja bear a large number of small cones near the tips of the branches, where they are not strong enough to bear the weight of a climber. To collect these it is necessary to reach the exterior of the crown. Mounted ladders provide one method of doing this. Another was the tree net. Its operation was described in detail by Seal et al. (1965). The tree net was triangular in shape and measured 34 feet (10.3 m) across the base and 38 feet (11.5 m) from base to apex, with a 12 × 12 inch (30 × 30 cm) mesh. It was suspended by special ropes and snatchblocks from a point near the top of the crown, covering part of the exterior crown and with the lower corners pulled taut and attached by guylines to nearby trees or driven posts. The net carried two collectors at a time.
The net did no damage to the crown and was reasonably effective, once in position, on deep-crowned trees with an abundant cone crop but it was a very slow method at best and impossible to use in dense stands. Its use has been generally abandoned in favour of less time-consuming methods.
Methods of climbing and picking fruits in the crown are independent of the method used to reach the crown, whether this is by ladder, tree bicycle or climbing irons. The following summary of the main points to be observed is based on Yeatman and Nieman (1978).
In climbing on the branches of a tree, as on the rungs of a ladder, handholds are used mainly for guidance and balance and the feet and legs are used for thrust. Only one limb - a hand or a foot - is moved at a time, gripping or standing on branches where they are strongest, close to the main stem. Doubtful branches should be tested by being pulled sharply before being trusted to carry the weight of the climber. Confidence and muscular coordination are keys to safe climbing. A sustained state of tension and reliance on strength alone can be both exhausting and hazardous. Most of the work should be borne by the legs.
Tension in a climber may be greatly reduced if he has confidence in a proven safety system. Occasional mishaps may occur even to the best climber, if only because a branch which appears safe turns out to be treacherously brittle or slippery. Modern climbing techniques and equipment are designed to ensure that, if a climber falls, he falls only a short distance before his fall is arrested.
Excellent illustrated accounts are available in Seal et al. (1965), Yeatman and Nieman (1978) and Robbins et al. (1981) and include details of the ropes and knots which the climber must know how to use.
Safety belt and strap. One essential item of equipment is the safety belt or harness. The most convenient type consists of a waist belt, which carries a number of metal rings to which may be affixed the safety line, safety strap or climbing chain, short lengths of safety rope, tool line etc., and a saddle which fits beneath the buttocks, is connected to the waist belt and can be used as a seat for the climber when this is convenient for collecting. Additional support can be provided by including a pair of shoulder straps as part of the harness. Attached to the safety belt are the equally essential safety strap or chain and one or more short nylon safety ropes which serve to secure the climber to the stem of the tree. One end is fastened to one side of the belt while the other is passed round the stem and then attached to the other side of the belt. A light chain is sometimes used as the climber ascends the bole, the length of which can be readily adjusted to the taper of the tree by taking in a few links. An adjustable safety strap is as good or better. A second, reserve short rope should be carried to enable a climber using climbing irons or ladders to surmount an obstructing branch below the live crown; the reserve rope is fitted above the branch before the original one is unfastened below it. The safety rope is also fitted to the upper stem while the climber picks fruits within easy reach. Thus safety belt and safety ropes together will, on suitable trees, ensure the safety of a climber as he ascends the bole and while he picks fruits, even in the absence of a safety line. But they do not ensure safety as he climbs within the crown.
Safety line and safety ropes.* Another important item is the safety line. Nylon rope of 12 – 14 mm diameter and weighing abour 1 kg per 10 m is commonly used. Apart from its strength and good wearing properties, it has advantage of being somewhat elastic, thus reducing the jarring effect on a climber's body as the rope tautens after a fall. Polypropylene is less suitable since it melts at relatively low temperatures. However, it has been used successfully in some countries e.g. Honduras, where nylon is inobtainable. Precautions taken are to use polypropylene rope at least 18 mm in diameter and to avoid any techniques which would involve prolonged friction on a stationary rope. Temporary friction of a moving rope, e.g. over a branch, is not dangerous since the heat generated at any one point in the rope is very little. Natural fibres such as hemp or jute need to be substantially heavier than nylon if they are to attain the same strength, in addition they are subject to rot especially if used in wet weather.
* The words “safety STROP” or “nylon STROP” have been frequently used in the past but are liable to lead to confusion if, as often happens, they are used in the same paragraph as “safety STRAP”. Both the safety STRAP and the safety STROP fulfil a similar function of securing the climber to the tree, but the STRAP is usually of leather or stout canvas and is much broader than it is thick, whereas the STROP is made of rope and is therefore circular in cross-section. In the present text the term “safety strop” has been replaced by “(short) safety rope” which is to be distinguished from the (long) safety line.
Safety lines or ropes may be conveniently divided into two classes, the short safety rope which the climber uses to attach himself to the tree while working in the crown and the long safety line which runs down to the ground and is controlled by an anchorman. The short safety rope varies in length from 3 to 10 m and is of the same gauge as the long safety line; a climber will normally carry two of them attached to his safety belt. When he is working in the crown, he attaches one of them either to a stout branch or to the stem. If he is in the upper crown where the stem is too thin to be safe, he attaches the rope to the stouter portion of the stem below him and passes it spirally upwards round the stem. If the stem is stout enough and he uses a safety rope of appropriate length, he can reach well out into the outer crown. The short safety rope is simple to use and renders the climber completely independent while collecting in the crown.
The SAFETY BELT goes round the waist of the climber. It may be used alone or may form part of a more elaborate SAFETY HARNESS.
The SAFETY STRAP goes round the bole of the tree and is secured at each end to the SAFETY BELT. It secures the climber to the bole until he climbs into the crown.
The (SHORT) SAFETY ROPE secures the climber or his (LONG) SAFETY LINE to the tree (either stem or stout branch) while he is working in the crown. It can also be used as a RESERVE SAFETY ROPE securing the climber when he is forced to disconnect his SAFETY STRAP in order to climb above a large isolated branch on the bole.
The (LONG) SAFETY LINE connects the climber to his anchorman on the ground. It provides safety while he is in the crown and a means of descent without having to climb down the bole.
One end of the long safety line is attached to the climber's safety harness, the other is controlled by an anchorman who remains on the ground. The length of the line must be at least twice the height of the tree, to allow a climber to be lowered to the ground, if necessary, from any position close to the top of the tree where he may be working. Apart from the additional safety factor it provides, the safety line can enable the climber to reach fruits in the outer crown which would otherwise be inaccessible.
Method of climbing with use of safety line. On reaching the lower crown, the climber ascends in a slight spiral round the stem, so that he takes his long safety line across branches which will hold the line in the event of a fall (Seal et al. 1965). If live branches are lacking on one side of the stem, the climber should follow a zig-zag course on the side of the stem bearing live branches. If stout branches are lacking, the climber should fit a safety rope to the stem and clip the safety line to it. The aim should be to ensure that he cannot fall freely more than 2 m before the safety line starts to take his weight. Meanwhile the anchorman, as described by Yeatman and Nieman (1978), must stand well clear of the fall line from the tree being climbed to avoid possible injury from falling branches that may be broken off as the climber ascends. The anchorman must be ready at any time to support the weight of the climber on the safety line as he feeds it under one arm, around his back, and over the other shoulder, releasing it alternately with one hand while gripping it with the other. A half turn of the rope should be made around the lower trunk of a neighbouring tree to provide additional friction and greater security should the climber slip or fall. However, the friction should be minimal during the ascent to ensure that the climber is not held back by the safety line. It is important that the unused part of the safety line remains coiled on the ground and free of obstruction so that tangles are avoided as the rope is paid out. The long safety line is of particular advantage when it is necessary to take rapid evasive action from wasps or bees that are sometimes encountered in tree climbing.
When the climber reaches the level in the crown where he is to collect, he may secure himself by passing the safety line over a stout branch and around the stem. Alternatively he may secure himself to the stem by means of a safety rope passing it over a stout branch and around the stem above him and re-attaching it to his safety belt then detaching the safety line. If the branches are not stout enough, he fixes a short safety rope to the stem as high above him as possible and passes the safety line through it. The rope should never be attached to the stem above the point where the diameter falls below 8 – 10 cm. The climber can now either go on to pick the fruits with the anchorman still holding the safety-line or he can apply a special safety line locking method, using carabiners or safety clips, and take charge of his own movements (Seal et al. 1965). In either case most of his weight can be supported by the harness saddle, enabling him to reach further out in the crown than would be the case if his entire weight had to be supported on relatively thin branches. Use of the safety line locking method allows the climber to make a controlled descent as he works downwards collecting fruits as he goes. An advantage of this method is that the anchorman is freed temporarily for other work; in this way one anchorman can look after several climbers. It is well suited to species in which cones or fruits are scattered all over the crown and picking in one tree takes some time. In species in which fruits are clustered in one part of the crown, picking is quick and it is best to keep the anchorman on the line (Seal et al. 1965).
Method of descent. For descent the climber must first climb up and release the topmost safety rope if one was used, while the anchorman takes in the slack of the safety line. Then, as described by Yeatman and Nieman (1978), the climber descends with care, following the same route down as the one he ascended by, so as not to foul his safety line on the small branches of the upper crown. When his feet reach branches that will support all his weight on the safety line and are large enough in diameter to withstand rope abrasion, he moves laterally to catch the safety line on the crotch of a branch. The climber continues down so that the trailing safety line passes up and around the stem, over a stout branch, and on around and down to the climber. Alternatively, in trees with dense crowns, it is often easier to stop, attach oneself to the tree, untie the safety line, pass it up on one side of the trunk over a branch on the opposite side and down the other side, and retie it to the body belt. With the safety line securely caught on a branch (crotched), the climber may be let down by the anchorman paying out the rope or he may control his own descent by using the safety line locking method. Descent to the ground by safety line is the best method when the ascent of the bole has been by climbing irons. When ascent has been by tree bicycle or sectional ladder it is usually preferable to descend the some way; otherwise the climber must loosen the bands of the tree bicycle or disconnect the sections of ladder while suspended from the safety line.
Method of picking fruits. With correct use of the safety harness and safety line the climber should have both hands free to pick the fruits. Methods vary according to the size, number and distribution of fruits and the firmness of the peduncular attachment. Numerous, small, clustered and accessible fruits can be picked and deposited immediately in a bag attached to the climber's belt or slung from his shoulder and with its mouth braced open. Bigger and more scattered fruits may be detached, dropped and collected from the ground later. Fruits too inaccessible to be picked by hand may be detached by long-handled pole, hook, rake or shears as described on pp. 56–57. Tools used in the crown should be pulled up by the climber by the use of a light tool line attached to his belt, after he has reached the collecting area in the crown. In Chile climbers beat the branches with a long stick to detach fruits of Nothofagus alpina, but the method is less effective with N. pumilio (Gordon 1979). Some form of hook is in common use for conifers. In Thailand the hooks used for collecting cones of Pinus kesiya and P. merkusii have been designed with two sharpened edges pointing in opposite directions, so that they can be used to detach cones with either a pushing or a pulling action, thus avoiding the breakage of twigs with new conelets. They are mounted on light steel tubes which can be extended to a length of about 3 m (Granhof 1975). Various types of hook, rake and shears are illustrated by Robbins et al. (1981). Gathering of fruits from the ground, when they have fallen after detachment by tools, is the same as described above for natural seed fall.
If fruits are small, numerous, clustered, inaccessible for hand picking or held firmly by the peduncle, it may be necessary to cut off whole fruit-bearing branchlets by long-handled shears or saw. Pinus oocarpa is an example of a species in which the cones have strong woody peduncles which are difficult to sever without damaging the branchlet. In such cases one alternative is to collect by cutting off the branchlets, but this causes destruction of the next year's crop of conelets (Robbins et al. 1981). A better solution is to devise new equipment to overcome special local problems. In Honduras a bell-shaped sharpened hook is designed to be pushed outwards from the centre of the crown towards the ends of the branches and this severs the cones while doing the minimum damage through bending or breaking the branches. The hook is mounted on a 5 m aluminium or wooden handle. It has been in use for over 5 years and has proved to be very practical for cone harvesting from P. oocarpa, P. caribaea, P. patula subsp. tecunumanii and P. maximinoi (Robbins 1982a).
If fruits are clustered at the end of long branches where they are out of reach of the climber, he may need to cut off the whole branch. In Brazil climbers cut off fruit bearing branches of Eucalyptus with a knife on a pole and the usual practice is to collect from alternate trees in successive years so that the tree crowns have a chance to recover.
4.15 Use of hand tools and safety line in picking fruits in the crown (ESNACIFOR/A.M.J. Robbins)
4.16 Climber controlling own descent by safety line locking method. (ESNACIFOR/A.M.J. Robbins)
4.17 Use of extension platform for cone picking in the Netherlands. (R.B.L. De Dorschkamp, Wageningen)
Climbers should wear boots with non-slip soles and overalls without belts or loops which could catch on branch snags. A close-fitting safety helmet, gloves and safety glasses are often useful. Anchormen must wear industrial safety helmets to protect them from objects falling from the trees. A light pruning saw is often necessary to provide a clean bole suitable for climbing by tree bicycle.
The methods described above have proved highly reliable when used on coniferous species. There is less experience and probably greater difficulty in climbing hardwood species of the tropical moist forests, where a few massive branches separated by intervals of 3 – 4 m pose a special problem. Very thorny species such as Acacia spp. present another problem but, because they rarely exceed 15 – 20 m in height, collection can often be made from the ground. Useful aids to collection described by Doran et al. (1983) include a strong vehicle roof carrier to stand on, light ladders fitting on the roof carrier, a rope and weight for throwing over a branch to shake or break it, flexible saw or long-handled pruning shears and thick leather gloves for stripping pods from thorny species. Standard collection methods will certainly need to be modified to adapt them to the peculiarities of individual tropical species.
Some types of equipment have been designed to raise the collector mechanically to a level where he can reach the fruit-bearing portion of the crown, without having to climb at all. Limited trials have shown that cable systems supporting a carriage can move pickers alongside tree crowns. Although access to several trees is obtained with one setting, the installation is time consuming (Matusz 1964, Gradi 1966, Stein et al. 1974). The system would prove most profitable in a stand where repeated collections are to be made. Experiments have also been made with cables or platforms suspended from balloons or helicopters. Balloons are not considered practical, but helicopters may have a part to play in certain conditions. Probably the most practical of all mechanical devices to raise or lower a man to within reach of the fruit crop is the Extension Platform. The following account follows that of Turnbull (1975 b).
The extension platform of a type used for the installation of overhead electric cables has been used for seed collection in many countries. There are a number of models available, including ones with telescopic raising gear and hydraulically operated articulated steel booms built on a turn-table.
Matusz (1964) describes the AGP-12 articulated extension device which has been constructed in the USSR and Seal et al. (1965) illustrate and explain the use of the British developed Simon hydraulic platform. The Russian machine could be used to collect seeds from trees to a height of 15 m and the Simon hydraulic platform to a height of 10 – 16 metres. They provide adequate working space for two men, who can dispense with safety-belts and associated gear. It was intended to develop a larger version of the Russian machine to reach to 30 m.
A trailer-mounted platform attached to, and powered by, an agricultural tractor has been developed in Australia for seed collections from heights up to 10 metres above the ground (Willcocks, 1974). This tractor-trailer unit is capable of being used almost anywhere a tractor can be safely worked. It is versatile and relatively low cost equipment. The Afron Hydraulic Drive Power Ladder has a lower reach (maximum picking height 7 m), but is highly manoeuvrable and is operated by a single person, since all the controls are on the picking platform. It is widely used in fruit orchards and could be a useful machine in intensively managed forest seed orchards provided that the trees are of moderate size. According to Seal et al. (1965), the hydraulic platforms are of most value when time and labour are short and fruits can be collected from accessible trees with good crops. Disadvantages of this equipment are the necessity for good access and the high capital cost. Where cone crops have been less accessible and prolific, the per unit cost of collection using the Simon hydraulic platform in the UK was found to be greater than using ladders or tree bicycles".
There is little detailed information on productivity in fruit collection, especially for tropical species. As pointed out by Dobbs et al. (1976), amounts collected per picker-day depend on a variety of factors which include not only the skill and energy of the picker but the size of fruits, the heaviness of the crop, the firmness of attachment of the peduncles, the presence of old or immature fruits on the branches which may confuse or slow down the pickers, the method of collection (by climbing, from felled trees, from the ground etc.) and miscellaneous factors such as weather, insects and travelling time. For Pseudotsuga in USA and Canada, Douglass (1969) and Dobbs et al. (1976) quote the same average figure of 2 – 3 hectolitres of cones per picker-day, collected from about four trees by climbing. Dobbs et al. (1976) indicated that the same rate of production can be expected from felled Pseudotsuga trees as by climbing the standing trees. 4 – 5 hectolitres of cones per climber per day can be expected for Pinus ponderosa and around 0.5 hectolitre for smaller-coned species such as Larix, Thuja and Tsuga. In IUFRO collections made in Pseudotsuga, Picea sitchensis and Abies grandis in western North America, a team of 4 experienced climbers could complete one selected stand in a day, collecting from about 20 well spaced trees (Fletcher and Barner 1978). In Thailand in stands of Pinus kesiya of medium size trees an average of 25 – 30 kg of cones is expected per climber-day, collected from 6 trees (Granhof 1975). In Honduras the collecting rate for P. oocarpa and P. caribaea averages 1 to 2.5 hectolitres from 3–5 trees per man-day, for a general bulk collection in an average crop (Robbins 1983 a, b). Matusz (1964) reported that an average collecting rate in European pine stands, 25 m tall and bearing average to good crops, with the use of climbing irons, was 20 – 50 kg of cones from 8 – 10 trees in a day, yielding 0.4 to 1.0 kg of seeds. For each tree the climber spends 15 – 25 minutes in ascending and descending and 20 – 30 minutes in picking cones. In Denmark the following yields of fruits or cones have been achieved, given the conditions of:
Easy access to stands and the standing trees.
A very good seed crop.
A very experienced team of climbers, using ladders and working 8 1/2 hours a day (Barner 1974).
|Species||hl fruits or cones/man-day|
|Picea omorica||1||1.5||(young stands)|
|Larix leptolepis||1.5||2||(young stands)|
|Pinus sylvestris||1.8||2.5||(seed orchards)|
Yields of seed per ha in a very good seed year are:
|Abies alba||150 –||200 kg|
|Abies Nordmanniana||150 –||200 kg|
|Abies nobilis (procera)||250 –||600 kg|
|Larix sp.||25 –||70 kg|
|Picea abies||50 –||150 kg|
|Picea sitchensis||15 –||25 kg|
|Pseudotsuga sp.||40 –||80 kg|
|Fagus sylvatica||500 –||1000 kg|
|Quercus sp.||2000 –||5000 kg||(?)|
|Fraxinus excelsior||400 –||800 kg|
|Acer pseudoplatanus||200 –||400 kg|
Little information is available for fruit collecting rates for tropical hardwoods.
Seed collection, especially by climbing, is arduous work and it is essential that climbers are carefully selected and well trained before they commence collecting operations. They need to be physically and mentally fit, with a natural aptitude for climbing and a combination of self-confidence and common sense. Any sizable collection programme should have a nucleus of at least one skilled climber on the permanent staff, who may be employed on other duties outside the seeding season. It will be his responsibility to conduct short training courses for any temporary climbers before the start of each collection season (Robbins et al. 1981). Good pictorial illustrations are an invaluable training aid, especially where climbers are illiterate.
Safety precautions will vary according to local conditions and particularly the species of tree and the equipment and methods of collection used. All staff taking part in collecting operations should be fully conversant with local safety rules. The selection of safety hints reproduced below is based on those of Yeatman and Nieman (1978), Dobbs et al. (1976), and Seal et al. (1965) and Isslieb 1964 (cited in Seeber and Agpaoa 1976).
All equipment should be carefully stowed, both during transport in the field and while in store between collecting seasons.
Clothing should be strong, well fitting, and suited to the weather expected.
All equipment should be checked before it is used and, if there is doubt about its condition, it must not be used until repaired or replaced.
Do not climb in wet or very windy weather, nor in poor light as at dusk, nor when overtired.
Do not climb trees with obvious signs of stem rot, severe cankers or galls, split stems, double leaders, or other abnormalities indicative of mechanical weakness.
The safety line should be coiled on the ground before the climber ascends to avoid tangling or snagging the rope in the underbrush.
The anchorman should hold the safety line under one arm and over the other shoulder. It is wise to make a half turn around a neighbouring tree. This gives control and prevents the safety line from being pulled from his hands. Pull in and pay out the safety line by alternate hand grips. A sliding rope is difficult to control and can cause painful friction burns.
Never climb with anything tied or looped around the neck.
Safety helmets and goggles should be worn to prevent injury to the head and eyes in climbing rough, densely branched trees.
Stand on and grip branches close to the point of attachment to the main stem.
Watch for brittle branches; test doubtful branches before putting weight on them. Avoid branches with bark peeling from them - they are slippery. As far as possible, decide on the climbing route while still on the ground, especially for the branchy crown region.
The climber should have three points of support at all times (one hand and two feet or two hands and one foot), moving one limb at a time, except when attached to the tree by a safety strap or rope or when suspended on a safety line. Climb calmly with regular movements, taking short steps.
Do not carry tools while climbing the crown. If there is need for a pole pruner or cone rake etc., use a light tool line to hoist the equipment to the working level. Leave the tool line attached to large tools as a lanyard while working. Return tools to the ground on the line, do not drop them or throw them down.
Beware of sharp branch stubs: they can snag clothing and may cause painful cuts and bruises.
Climb spirally or in a zigzag manner, or fasten safety strops to the stem so that you cannot fall more than 2 m before your weight comes onto the safety line.
The diameter of the main stem should not be less than 8 cm at waist level during climbing. If in doubt concerning security, do not hesitate to tie a safety strop to the stem at a safe level before climbing within reach of the seed-bearing crown.
While attaching safety rope, keep one arm securely around tree until the rope is fastened to safety belt.
Before letting go of the tree with your hands, test your weight against the safety rope and footholds.
When picking near the top of a tree, keep your body close to the stem, so that your weight bears down, not outward.
The safety strap should always be attached around the tree stem except while you are climbing or changing position in the crown or are suspended on the safety line.
Before dropping bags of cones or other material, be sure that the personnel on the ground are notified and are well clear.
When collecting fruits from a ladder, make fast the top of the ladder to the tree with a nylon strop. The ladder must be further steadied with two guylines.
Have a well-stocked first aid kit handy at the climbing site at all times.