These notes are a selection from items appearing in the 1966-67 report of the Commonwealth Agricultural Bureaux, which were taken originally from Forestry Abstracts Vol. 28, parts 2 and 3, prepared by the Commonwealth Forestry Bureau at Oxford. They are republished by special permission. The items cover the period 1964-66 and are, of course, highly selective; no attempt has been made to cover the whole field of forest science.
Forest hydrology
Tropical forestry
Forest fires
Aerial survey
Work study
Balloon and helicopter logging
Chipping in the forest
Precompressed and flexible wood
Composite wood
Storage of pulpwood chips
Probably the most important general review of present-day thinking in this field is to be found in the proceedings of the Forest Hydrology Symposium held in Pennsylvania in 1965 (FA 28: 1734). Penman's review in 1963 (FA 24: 3144) studied the general relationships between vegetation and the water regime, and a Russian monograph has been made available in English translation (FA 25: 4577).
The trend away from the classical catchment experiments toward more intensive investigations into the water balance gathers impetus. Particular emphasis is being placed upon the energy relations of evapotranspiration, as illustrated by the work of Penman and of several American workers (FA 27: 274, 276; 28: 1742).
Meanwhile, macro-scale water balances are being studied with the aid of electronic computers. Water yields and other hydrological data from numerous catchment experiments are being processed to provide generalizations and predictions for other areas, and at Harvard multipurpose catchment use is being studied to determine what combination maximizes economic returns (FA 22: 4022; 24: 1523; 28: 1735). At Stanford University the unique combination of sites that goes to make up any given catchment is being investigated by numerical simulation methods (digital hydrological synthesis) in order to predict river flow characteristics (FA 28: 1735).
Continuing interest in problems of tropical forestry is reflected in the records of conferences or symposia which appeared during the period under review. Review papers were presented to the UNCSAT (United Nations) conference1 at Geneva (1962) on silviculture in Asia (FA 25: 377, 1546) and Africa (FA 25: 378) on many subjects, including silviculture in Burma, afforestation in Taiwan, teak planting in Senegal, mechanization of plantation operations in west Africa, thinning practice for Aucoumea klaineana in Gabon, and planting of Tarrietia utilis, A. klaineana and Khaya ivorensis on the Ivory Coast. The proceedings of the All-India Tropical Moist Evergreen Forest Study Tour and Symposium (1960) (FA 26: 1965) contain review papers on regional silvicultural problems. The role of forestry in the economic development of the savanna areas of Nigeria has been examined in a series of papers presented to the 1st Nigerian forestry conference (1964) (FA 27: 1956); subjects covered include the use of Khaya senegalensis, Terminalia spp., Chlorophora excelsa, C. regia, and other species, problems of soil moisture and nutrition, and controlled burning.
1 UNCSAT= United Nations Conference on the Application of Science and Technology for the Benefit of the Less Developed Countries.
An FAO review of current silvicultural practices in rainforest in various parts of the world (FA 26: 1991) concludes (1) that liberation is the most important phase of rainforest treatment, and (2) that, in the long run, intensively managed plantations may prove to be the only economic source of timber in the tropics.
Malayan silvicultural experience has been consolidated in an enlarged and revised (looseleaf) manual (FA 27: 5682), while the application of 'LSR' sampling techniques for established regeneration of the first managed rotation of the lowland dipterocarp forest is described (FA 25: 1076). Regeneration of the Sabah dipterocarp forests (FA 27: 415) and enrichment planting, especially with Dryobalanops aromatica, in Selangor (FA 26: 584) are reviewed.
Afforestation techniques developed in Papua and New Guinea have been described for Araucaria cunninghamii, A. hunsteinii (A. klinkii), Tectona grandis, Eucalyptus deglupta and Ochroma lagopus (FA 27: 1976, 3712). Other studies from southeast Asia include: silviculture of Acacia auriculiformis in Indonesia (FA 27: 1973); and Albizzia falcata as an exotic plantation species, and as a nurse for dipterocarps, in the Philippines (FA 26: 2030). Among papers on the growth of tropical pines as exotics may be mentioned the collation of the Malayan data on Pinus caribaea, P. merkusii and P. insularis (FA 27: 1983),
In Africa, Catinot's comprehensive study of silvicultural methods in west and central African high forest is noticed (FA 27: 3670), in which the techniques of stand improvement and natural and artificial regeneration used in different countries are critically examined; failures are attributed generally to lack of light at ground level. New French equipment and techniques developed for determining the optimum light for each species, and the regeneration method now in use in Gabon (méthode du recrû), are described. In Malawi, successful establishment of Gmelina arborea is based on sowing in 6-in black polythene tubes and planting with stock 6-9 in high (FA 26:3562). The literature on the ecology, silviculture and management of African open forest has been reviewed (189 refs.) (FA 27:399). In Surinam, a detailed study of natural regeneration, giving techniques of sampling, refining (chiefly with 2, 4, 5-T arboricides) and liberation has been published (FA 27:3710).
Increasing use is being made of aircraft for detection, and long-term trials in Canada have indicated that the overall efficiency of fire spotting can be greater from the air than from lookout towers (FA 24:5122). An important development in aerial detection has been the introduction in North America of the use of infrared scanners, slung below the aircraft; these scanners can both detect fires (e.g., a fire 4 ft square from an altitude of 1000 ft) and take a photographic record (FA 27: 2324, 6121).
Tests continue on various chemicals as retardants and suppressants, including liquid phosphates that are also marketed as fertilizers in the United States of America (FA 26:798; 27: 790), and with "wet" water for extinguishing peat fires in the U.S.S.R. (FA 27:791), but particular emphasis is being placed on the use of algin-gel compounds (FA 25: 802, 2309-10;27: 2326, 4177). The practice of applying such substances from the air is becoming increasingly widespread, and the economic merits of using converted helicopters ("helitanks") have been compared favourably with those of fixed-wing air tankers in Californian trials (FA 25: 5198), but the problem of corrosion in aircraft still presents some difficulties (FA 26: 5291).
From the management point of view, one of the major problems is still that of calculating what degree of expenditure on maintaining fire protection services is economically justifiable; this has been the subject of a number of operational research surveys, such as that carried out in California to relate suppression-crew size to total fire costs (i.e., suppression costs + losses) (FA 27: 6127).
Using the parallax-difference method on aerial photographs of tropical secondary forest, it has been found possible to classify the trees into 10 m height strata with reasonable precision. A highly significant correlation (r = 0.748) was found between the crown density of the trees of the 31 to 40 m stratum as measured on the photographs, and tree volume as measured in the field, but a very low one (r = 0.138) for the 21 to 30 m stratum. A close correlation (r = 0.806) was also found between the volume of the 31 to 40 m stratum and the total volume. This method may be used, with adequate checking, to estimate the volume of secondary forests (FA 25: 5528).
Two new methods have been developed for dealing with problems encountered in mapping mountain forests from the air. (1) In Switzerland, an approximation method has been developed for correcting distortion due to slope in aerial photos by projecting the original negative on to a photosensitive material that has been bent into roughly the same planes as the terrain photographed (FA 25: 2623-24). (2) In the course of aerial surveys in Sabah, where maps were required to show land form for the selection of extraction routes, normal photogrammetric contouring was impossible because the ground surface was covered by dense forest and the establishment of height control by ground surveys would have been expensive and very difficult. It was therefore decided to fly parallel strips over the area with the Airborne Profile Recorder, using the sea as datum, from which form lines of the forest canopy could be constructed. By this means, maps on a scale of 1: 25,000 with form lines at 50 ft vertical intervals were obtained quickly and economically. The problem of precise location of flight dines over virtually featureless forest was solved by the use of the very accurate Marconi AD 2000 Doppler Navigator (FA 27: 4608).
A study of the possible error due to wind-sway in parallax measurement of tree height indicates that for e.g., a 75 ft spruce with an observed maximum sway of 7.9 ft in a wind of 15-20 mph the error could be ±18 percent. Sway varies with bole length, crown size, etc. In seven trees measured, it varied from 2 to 11 ft. representing height errors of ± 4.5 to ± 25 percent. Aerial photography should be done on calm days, or flight runs, if possible, at right angles to the wind (FA 26: 4114).
Useful new apparatus for photo interpretation includes a variable-scale stereoscope developed at the Swiss Forest Research Institute, which permits simultaneous viewing of photos or maps on different scales (FA 25: 1139).
Experiments have been made in Japan to establish the possibility of distinguishing forest types on aerial photos by the measurement of photodensity. Prints from panchromatic film were scanned by a recording microphoto density meter which traced curves of the percent of illumination (T) passing through the film at each unit (0.01, 0.02 or 0.1 sq mm) scanned, as photographs of plantations and different types of natural forest were viewed. The method is held to be promising (FA 25: 1132).
Long-term studies in Oregon and Washington indicate that colour and panchromatic aerial photos provide a reliable means of estimating large-scale tree-killing by Dendroctonus pseudotsugae, colour being the more efficient (FA 25: 5382). In connexion with the relative value and different uses of color and panchromatic film, the Russians have developed a method of using two cameras in conjunction to take simultaneous 18 X 18 cm panchromatic photos and 30 X 30 cm colour photos on spectrozonal film (FA 26: 4111).
A good deal of work has been done on the reflectivity of foliage in relation to photointerpretation. An investigation on the reflectivity of 64 species of plants forming important components of the vegetation in the Tuva region (south central Siberia) revealed differences in the curves of spectral brightness of different ecological groups of plants (trees, shrubs, steppe and semidesert plants, mosses and lichens, etc.). On spectrozonal photographs, hardwoods and larch have increased brightness, and Scots pine and spruce reduced brightness, in the infrared region of the spectrum, Pinus sibirica being intermediate. Stands damaged by Dendrolimus sibiricus or by fire can also be clearly distinguished (FA 25: 1130). In continued work on this study, a new piece of equipment was used - a mobile tower mounted on a lorry, from which the reflectivity of tree crowns could be measured from above (FA 27: 1590).
An aid to visual reconnaissance has been developed in Canada in connexion with a line-strip aerial survey of dying balsam fir, by the use of an operation recorder. Data are recorded on a moving chart which can later be related to the flight line on a map, thus relieving the observer of the necessity to mark information on a map as he goes along. He is free to observe the forest continuously as it unfolds below him. Recording is done by means of a series of switches mounted on a keyboard held in the hand, the switches being coded according to a prearranged classification based on the survey problem and the information desired (FA 26: 3965).
The increasing application of work-study methods to forestry operations is taking place against a background of advances in mechanization which highlight the need for rationalization, operational efficiency and economy of labour (FA 26: 5193; 27: 4009).
Practical applications of work and time study have been concerned for the most part with felling and primary conversion (FA 25: 724, 3585, 5117; 26: 691-4, 3740, 3742-4; 27: 2678, 5994); studies have also appeared dealing specifically with trimming by power saw (FA 26: 3746), felling and horse skidding (FA 27: 2262), comparison of the time expended on actual felling and tractor transport (FA 25: 3588), logging pulpwood in different lengths (FA 25: 3586), stacking (FA 25: 725), storage handling and stamping floating marks (FA 25: 723, 5118), and resin tapping (FA 26: 645).
Mechanization has led to an increased awareness, particularly in the Scandinavian countries, of the hazards involved in working with machines, and thus to intensified work on safety and accident prevention (FA 26: 661-2, 2246-7, 3722; 27: 668). Special clothing and equipment such as safety boots, helmets (FA 24: 3715), ear plugs or muffs (FA 26: 2248) etc., are becoming more and more popular. The importance of correct and thorough training of workers in the safe use of all forest machines and tools is now being emphasized (FA 26: 3726; 27: 5989).
Physiological studies have included measurements of energy expenditure, pulse rate and fatigue in planting by different methods (FA 25: 5027), pulling out the cable from the winch into the stand (FA 27: 2255), and felling and primary conversion, both by axe (FA 27: 5991) and by power saw (including a comparison of work on softwoods and hardwoods) (FA 27: 3998, 5993). A Czech study in which measurements were made of the energy wasted by workers in walking to their place of work underlines the economic advantages of providing transport for them (FA 25: 5553). German work has indicated that equipment used in mechanized tending, and also grass-crushing disks attached to boots, are physiologically unsuitable for women (FA 27: 673). Swedish studies on the relationship between individual characteristics and work performance have demonstrated the importance of factors such as physical build (FA 27: 5992) and oxygen uptake (FA 27: 4017-8).
Many studies have been made on the adverse effects of machine noise and vibration on workers' health, and attempts at reducing them, with particular reference to power saws (FA 24: 3717-20; 26: 3724-5), but also to lathes, etc. (FA 27: 6825).
The trend in the actual techniques employed in applying work study to forestry shows a definite move away from stop-watch methods in favour of work or activity sampling techniques (FA 25: 705, 3564; 26: 5187).
These types of logging, though fundamentally distinct, are often discussed together as "aerial logging" (cf. FA 26: 735, 2287-8) and they are so treated in this note.
The balloon logging studies published during the period under review all relate to a comparatively few trials in Oregon and British Columbia. These trials have attracted widespread interest and have been written up many times in various ways by various authors (FA 25: 3622-3; 26: 3775; 27: 2275, 4086, 6053). The most important publication is a comprehensive two-part study by the Pacific Northwest Forest and Range Experiment Station (FA 26: 5248-9) which was made for the United States Forest Service to establish the feasibility of balloon logging systems, to examine system parameters, and recommend a feasible system. The study concluded that both static and dynamic systems of balloon logging are feasible and economic. Dynamic systems promise shorter cycle times and larger payloads; helium is preferable to hydrogen. Full-scale tests with a 150000 ft3 Vee balloon are recommended. The fast haul-in of the Vee balloon gives a much greater aerodynamic lift.
Three separate helicopter logging trials have been described during the period under review. A Norwegian trial in which logs were dropped off into water showed that helicopter logging was economically possible in difficult mountain terrain (FA 26: 736, 3777). A Russian trial in which logs were released on to solid ground also proved technically successful, but no economic conclusions were drawn (FA 27: 4085). In the United States, a helicopter was used for skidding (rather than lifting) logs on land, and also for towing logs on water, but at the moment the use of helicopters for swamp logging would apparently be too dangerous (FA 26: 3776).
In the major pulp-producing countries, increasing interest is being shown in chipping in the forest: e.g., in the United States (FA 26: 3749), Canada (FA 27: 4047), U.S.S.R. (FA 27: 2235), Sweden (FA 26: 2264), Finland (FA 27: 4048), Germany (FA 27: 721) and Poland (FA 27: 2233). These papers include studies on chipping machinery, organization of work, economics, etc., and there seems to be no doubt that this method of conversion and harvesting is destined to become more and more widely used. At present, in commercial operations, the chips are transported conventionally by lorry or tractor/trailer, but research is still proceeding in North America and the U.S.S.R. on chip transport from the forest by pipeline. The Russians do not appear to have made much progress with the latter method (FA 25: 3608, 5147), and in Canada the economic feasibility studies have not yet been made public (FA 26: 708; 27: 730)
The technique of plasticizing wood with ammonia has received attention in several countries. In the United States, experiments were reported in 1963 on bending strips of birch veneer into spirals, knots, etc. without checking or failure, after immersing them in liquid ammonia for 15-20 minutes, the strips retaining their forms without clamping or control as the NH3 diffused off. Larger samples of pine, oak and basswood were also successfully plasticized (FA 25: 5719). In a fuller account of this method, the action of liquid ammonia on lignin and cellulose, and the effect of treatment variables, were described. Stock 1/8 X 4 X 40 in was sufficiently plasticized for bending in 4-5 hours, and 1/16 -in veneer strips in 15-30 minutes. Evacuation and pressure reduced treatment time. Steam-bent clips Of 1/16 in veneer opened completely when placed in hot water, but hardly opened at all when dipped in water to leach out the ammonia. Low-density and ring-porous woods were the least suitable for treatment (FA 26: 2874). In the U.S.S.R., a process is reported for softening green birch with gaseous or liquid ammonia and then compressing it cold (at 
80 kg/cm2), holding it in moulds for 4-8 minutes and finally drying it (FA 26: 1287). The properties of the wood so treated were investigated and found to be particularly suitable for bushes, bearings, etc. in machinery (FA 26: 1288). Further accounts of the method have been given, with reference to the use of ultrasonics, surfactants and radioactive radiation for improving the penetration by ammonia, to the chemistry of the changes caused by impregnation and irradiation (FA 26: 2875), and to the production of a strong thermostable material (FA 27: 1244). In the United Kingdom, methods have been developed at Princes Risborough (and patented) for making "precompressed wood" and "flexible wood" from suitable timbers e.g., beech. "Precompressed wood" is produced by compressing long (e.g., 36 in), lengths of steamed wood by about 20 percent of its initial length, using a concertina-type support to prevent buckling, and applying a force of about 3000 lb/in2. After compression and release, wood 1 in thick, retaining about 3 percent residual strain, can be bent, cold, dry, and without support, to radii of about 9 and 7 in, at 12 and 18 percent moisture content respectively. "Flexible wood" is produced by applying to precompressed wood, after remachining, a second compression (cold and dry) to about 20 percent strain, requiring about 9000 lb/in2. On release, residual strains of about 15 percent are obtainable. Samples 1 in thick can be bent to about 4 in radius without support, and can be easily resawn and machined (FA 28: 4676).
Research on continuous lamination has been carried out in several countries. In the U.S.S.R. trials with an experimental roller-type, continuous-feed machine for gluing boards, incorporating the principle of contact dielectric heating, have been described (FA 25: 1326), and a prototype machine has been developed for continuous automatic gluing of finger-jointed pieces of lumber, using dielectric heating and the application of 15 kg/cm2 of end-grain pressure, to give a joint strength of 90 percent of that of solid wood (FA 26: 4345). In Germany, a method has been described for gluing laminates (for sleepers, deck planks, etc.) that are longer than the available presses; a fast-curing phenolic resin and RF heating are used and the assemblies are passed through in stages (FA 25: 2828). In the United States a process has been developed in which the wood is preheated, glue is spread on the hot surface, and the assembly is pressed between two moving steel bands while the glue cures. By combining this process with finger jointing and edge gluing, small wood can be utilized (FA 25: 5714).
A pilot-scale machine has been constructed in the United Kingdom for producing, in one operation, from random-length planed boards with finger-jointed ends, a continuous laminated member that can be cross-cut to any required length (FA 27: 2895).
Experimental work on the reinforcement of laminated beams with steel has been described. In the United States, the use of pretensioned, high-strength steel strips bonded to the surface of laminated Douglas fir beams has been investigated; the stiffness, strength, work to maximum load, and permissible design loads of these beams were much higher than those for similar unprestressed beams, and variability in strength was much less (FA 24: 4301; 26: 5870; 27: 6885). In the United Kingdom, trials on the reinforcement of beams by mild-steel rods bonded into grooves in the laminae have shown that the construction is technically feasible and particularly applicable to structures with long spans (FA 25: 5746; 26: 4387; 27: 6884).
Studies in the storage of pulpwood as chips rather than as roundwood (FA 24: 2938-9) have continued, especially in Scandinavia. One of the main advantages of chip storage for certain species (e.g., Norway spruce and birch) is that aging of the extractives takes place rapidly, making possible a much shorter storage period than that needed for pulpwood stored as roundwood (FA 25: 4139, 5871; 26: 5989; 27: 1428-9). In experiments on storing heartwood and sapwood chips of spruce separately, the total extractive content of the former remained constant during 12 weeks, whereas that of the sapwood chips decreased rapidly (FA 26: 4488). Amount and composition of heartwood extractives changed only during storage at 50°C (FA 27: 7015). Differences in the content of ether-solubles and combined acids between birch chips and roundwood after storage are tentatively attributed to the greater surface area of the chips and to heat in the chip piles, though degradation by enzymes and microorganisms may also be a factor; changes in chemical composition varied with position in the pile. The reactions are not always favourable to sulphite and kraft pulping of birch (FA 27: 1430). Wood losses caused by fungi, etc., are higher for chip than for roundwood storage of birch, aspen, pine and spruce (FA 27: 3151), and may be considerable for longer storage periods in a range up to 13 months (spruce) and 4 months (birch) (FA 27: 1428); normally ca 5 percent by weight of wood substance is lost during the first 4-5 months of storage (FA 27: 3050). Losses in wood substance averaged ca 1 percent per month in the warmest part of a pine chip pile (FA 27: 7016).
Yields of pulp from spruce sapwood, but not heartwood, chips decreased slightly after storage, but yields as a percent of the wood cooked were generally little affected by storage (FA 26: 5988, 27: 3050). Losses in spruce pulp yields, especially in acid sulphite pulping, that occur when chips are stored at high temperatures are attributed to a prehydrolysis effect that causes lignin condensation and necessitates longer cooking, with a consequent loss in hemicellulose (FA 27: 7015). Tear strength was very little reduced compared with that of pulp from roundwood (FA 27: 3050); brightness of both birch and spruce pulps was reduced as a result of discoloration during chip storage (FA 25: 5871; 27: 3050), especially (spruce) after storage at 20°C (FA 26: 4488). Tall-oil and turpentine yields of slash pine were reduced by chip storage (FA 25: 4348); similar results were obtained for Scots pine (FA 27: 1429), although yields from roundwood stored indoors at 20°C were not much above those from chips (FA 26: 5989).
The temperature in piles of birch chips reached a maximum of 69°C in 10-14 days and in pine and spruce 63° and 58° respectively in 14-30 days (FA 27: 5008). Mean moisture content of chips from sawmill waste stored in the open fell only to 49 percent, compared with 43 percent for similar material stored in a shed, and 26 percent for chips from long logs, stored in a shed, and having a lower initial m.c. (FA 25: 4347). In Canadian studies (FA 25: 2958), fire spread in piles was slow and confined to the surface layers, and in Finland (FA 27: 3049) the fire hazard is considered less than from roundwood stacks. The reduced handling costs are considered in Sweden (FA 27: 7016) to make chip storage more economic than roundwood storage in spite of losses in wood substance and hence in total pulp yield.
Forestry abstracts is formally recognized by FAO as the authoritative source of information on all literature of interest to forestry produced in the world. It is prepared by the Commonwealth Forestry Bureau, Oxford, England, which is one of the three international documentation centres for forestry also recognized by FAO. The other two are the United States Department of Agriculture and the Bundesforschungsanstalt für Forst- und Holzwirtschaft, Reinbek, Federal Republic of Germany.
