The boreal forests: An overview

K. Kuusela

Dr. Kullervo Kuusela is professor emeritus of the Finnish Forest Research Institute. This article is based largely on The dynamics of boreal coniferous forests, written by Dr Kuusela and published by the Finnish National Fund for Research and Development (SITRA). Helsinki, in 1990

The boreal forests, stretching around the northern tip Of the globe, account for 29 percent of the world's total forest area. They are one of the largest pools of living organic carbon on Earth and are almost certainly a significant factor in the determination of global climate. They are a major source of softwood timber resources and are important as a habitat for both animals and humans. Yet their special characteristics are poorly understood. This article examines the boreal forests and sets out some of the challenges related to their management in the future.

The boreal forests constitute a homogeneous circumpolar vegetation belt

The boreal forest is a homogeneous, circumpolar vegetation belt (see Figure) with temperature being the most influential environmental factor determining its geographical location.

The northern boundary of the zone corresponds to about the July 13°C isotherm, while the southern boundary coincides with the July 18°C isotherm. Therefore, the boreal forests of the world fall entirely within the borders of Russia, Canada, Alaska and the Nordic countries (Finland, Norway, Sweden).

Forest resources

Because the boreal coniferous forest zone extends across a number of states and administrative units that also include other forest zones, there is no precise estimate of the boreal coniferous forest area. However, the zone covers about 920 million ha (FAO/ECE, 1985; Korotkov, personal communication); that is, 29 percent of all forests and 73 percent of the coniferous forests of the world.

The forest resources of the boreal countries, including Alaska, and their share of the world totals are presented in Table 1. Of the total area of closed boreal forest, 73 percent is in Russia (within the area of the former USSR), 22 percent in Canada and Alaska and 5 percent in the Nordic countries. Approximations of growing stock are provided in Table 2, while the principal boreal tree species are indicated in Table 3. Although most boreal tree genera occur throughout the zone, pine is missing in Alaska and balsam fir is absent westward of about longitude 125°W. In Eurasia, the western limit of the ranges of larch and fir is about 40°E. Either these two genera are bound to a continental climate, or the time after the most recent glacial era has been too short for them to adapt and invade northwestern Eurasia. In the northwestern areas of Eurasia, the only two conifers found are Scots pine and Norway spruce.

TABLE 1. Major categories of forest land within countries and within their boreal zones

Forest category	Former USSR	Alaska	Canada	Norway	Sweden	Finland	Total
Country (state) totals according to FAO/ECE, 1985
(Million ha)
Forest and other wooded land	929.6	52.2	436.4	8.7	27.8	23.2	1477.9
Closed forest	791.6	8.5	264.1	7.6	24.4	19.9	1116.1
Exploitable closed forest	534.5	6.4	214.8	6.6	22.2	19.4	803.9
Proportion of country totals in boreal zone*
(Million ha)
Forest and other wooded land	(790)	46	327	(7.0)	21.4	22.7	(1214)
Closed forest	673	5	198	5.9	18.4	19.5	920
Exploitale closed forest	(450)	5	144	5.1	16.1	19.0	(639)

*Country notes:

Former USSR. Closed forest corresponds to total forested we. In the outlook study of 1989 this area was reported to be 810.9 million ha instead of the 791.6 million ha reported here. According to estimates of a USSR correspondent, the proportion belonging to The boreal zone is 85 percent.

Canada. According to Canada's 1986 forest inventory, the boreal forest region accounts for 299.2 of the country's 397.9 million ha of inventoried forests. The same proportion (75 percent) has been applied to derived was of forest and other wooded land and of closed forest belonging to the boreal zone. From the same source it can be derived that 67 percent of the inventoried productive forest is in the boreal zone. This percentage has been applied to the exploitable closed forest.

Alaska. The FAO/ECE source only shows data for the whole of the United States but, since it indicates how national standards are translated into FAO/ECE standards data for Alaska could be extracted from Forest Statistics of the United States, 1987. Thus, the United States total forest land has been taken as forest and other wooded land, the United States timberland - reserved and unreserved - as closed forest and the United States unreserved timberland as exploitable closed forest. For the boreal forest of Alaska, Mr La Bau from the United States Forest Service has kindly helped me with information.

Norway. The boreal zone covers all counties except Østfold, Akershus and Oslo, Vestfold, Aust-Agder, Vest-Agder, Rogaland and Hordaland. From official statistics it can be derived that 78 percent of the "productive forest land" belongs to the boreal zone. The same percentage has been applied to closed forest and exploitable closed forest.

Sweden. Boreal forest covers Värmland, Örebro, Västmanland, Gävleborg and counties to the north of these. The area of these counties located in the boreal zone has been derived from country statistics.

Finland. All forests except those of the forestry board districts, Ahvenanmaa and Helsingin, belong to the boreal zone. According to official statistics, this corresponds to 98 percent of the (productive) forest land. The same percentage has been used throughout this table.

Ecology of the boreal zone

The boreal zone can be divided into maritime, continental and high continental subzones, of which the continental area is the largest. In the maritime zone, the range of climatic extremes is relatively small. Winters are comparatively mild and summers are often cool. the mean temperature of the warmest month is + 10 to + 15°C and of the coldest month +2 to -3°C. The annual precipitation, much of it as snow, ranges from 400 to 800 mm but can be I 000 mm or more in western Norway and Newfoundland.

Continental winters are long and cold and there is abundant snow for five to seven months. Considerable variation of the monthly mean temperature, especially in winter, is a marked feature of the zone, requiring adaptability on the part of trees. Desiccating winds and temperatures of -20 to -40°C can be lethal for trees in the northern parts of the zone. Warming in the spring is rapid, however, there is a great variation in the time at which photosynthesis begins. Summer weather is comparatively warm but it can be very changeable. The vegetation period, measured by the number of days when the mean daily temperature is more than +10°C, lasts from 100 to 150 days. The mean temperature of the warmest month ranges from +10 to +20°C. During the year, the range of the mean monthly temperature is from 20 to 40°C and the maximum range can be from 60 to 70°C. The annual precipitation varies from 400 to 600 mm, with the major part of it falling during the summer months.

In the high continental climate of eastern Siberia and the Far East, the winter is very long, extremely cold and dry. The mean annual temperature varies from -7 to -10°C. The range of the mean monthly temperature can be more than 40°C and the lowest temperature can be -50 to -60°C. The mean temperature of the coldest month can be colder than -25°C. Spring comes rapidly and summer is short and comparatively warm but frost is possible every night, even in summer. At around 300 to 400 mm, annual precipitation is generally lower than in other subzones. The greatest part of the precipitation falls during the growing season but, in spite of this, the precipitation/evaporation ratio is less than one in warm summer months.

Tree species dynamics

In the boreal forest ecosystem, tree species composition in any given area is undergoing constant change. The basic principles of the ecological interdependencies in boreal tree species dynamics can be illustrated by natural successions from pioneer stands, dominated by broad-leaved trees, to climax stands, dominated by spruce.

Pioneer trees. Pioneer trees are specialized in colonizing bare forest sites with unmodified soil parent materials, e.g. land emerging from seas and lakes or exposed by retreating glaciers, and open sites after wild fires, windthrows and other calamities, as well as abandoned fields and other treeless lands. The boreal pioneers proper, the broad-leaved genera Alnus, Betula and Populus, are characteristically multiform. They hybridize easily and genetic diversity is an advantage for them as pioneers.

TABLE 2. Growing stock

Growing stock	Former USSR	Alaska	Canada	Norway	Sweden	Finland
Country (state) totals according to FAO/ECE, 1985
(m3/ha)
Forest and other wooded land	90.5	...	62	...	87	70
Closed forest	...	158	...	87	97	80
Exploitable closed forest	125	158	107	...	100	81
Boreal zone*
(m3/ha)
Forest and other wooded land	90	...	54	...	...	69
Closed forest	...	100	...	65	86	79
Exploitable closed forest	125	100	94	...	89	80

*Country notes:

Former USSR. Volumes per hectare in the boreal zone are assumed to be the same for the whole of the former USSR. Only minor parts have been logged so far.

Alaska. The volumes per hectare reported by La Bau for productive boreal forest in Alaska have been used for closed and exploitable closed forest.

Canada. The volume per hectare for boreal forest is derived directly from Canada's 1986 forest inventory for stocked. productive forest

Norway, Sweden, Finland. Growing stock per hectare has been differentiated into boreal and other zones following the proportions derived from recent official national statistics.

TABLE 3. Principal boreal tree species

North America		Eurasia
Coniferous		Coniferous
Pinus contorta Douglas	Lodgepole pine	Pinus sylvestris L.	Scots pine
Pinus banksiana Lamb.	Jack pine	Pinus cembra L. var. sibrica	Siberian cembra
Pinus resinosa Aiton	Red pine	Pinus pumila Rig.	Japanese stone pine
Pinus strobus L.	Eastern white pine	Larix sibirica Ledeb.	Siberian larch
Pinus rigida Miller	Pitch pine	Larix gmelini (Rup.) Litv.	Dahurian larch
Larix laricina (Duroi) K. Koch	Tamarack	Picea abies (L.) Karsten	Norway spruce
Picea mariana (Miller) Britton, Sterns & Pogg.	Black spruce	Picea abies var. abovata Ledeb.	Siberian spruce
Picea glauca (Moench) Voss	White spruce	Picea jezoensis (Siebold & Zucc.) Carr	Yeddo spruce
Picea rubens Sarg.	Red spruce	Picea glehnii (Fr. Schmidt) Masters	Sachalin spruce
Tsuga canadensis (L.) Carrière	Eastern hemlock	Abies sibirica Ledeb.	Siberian fir
Thuja occidentalis (L.)	Eastern white cedar	Abies nephrolepis Maxim.	Khingan fir
Abies balsamea (L.) Miller	Balsam fir	Abies sachalinensis Masters	Sachalin fir
Broad-leaved		Broad-leaved
Alnus rugosa (Duroi) Sprengel	Hazel alder	Alnus incana L.	Grey alder
Alnus incana L. Moench	Speckled alder	Alnus hirsute Tures.	Manchurian alder
Betula neoglaskana Sarg.	Alaskan birch	Alnus kamschaitic Call. Kam.	Creeping alder
Betula papyrifera Marshall	Paper birch	Betula pendula Roth	White birch
Betula occidentalis Hook.	Water birch	Betula pubescens Ehrh.	Downy birch
Betula alleghaniensis Britton	Yellow birch	Betula plaatyphylla Sukacz.	Asian white birch
Populus balsamifera L.	Balsam poplar	Betula ermani Cham.	Erman's birch
Populus tremuloides Michaux	Trembling aspen	Betula dahuric Patt.	Dahurian birch
Populus deltoides Bartram ex Marshall	Eastern cottonwood	Betula japonica Sieb.	Japanese white birch
Populus grandidentata Michaux	Largetooth aspen	Betula costata Trautv.	Yellow birch
Populus tremula L.			Aspen
Populus suaveolensis			Mongolian poplar
Populus sibolda			Siebold aspen

In the boreal forests, much of the annual precipitation is in the form of snow

Mixed broad-leaved and conifer forest in central Finland

A spruce stand in northern Sweden

Birch (Betula spp.)

Spruce regenerating under pine on poor soil about 90 years after burning in northern Finland

Their reproductive strategy is characterized by profuse crops of small, light and winged seeds dispersed by the wind, and by vegetative sprouts. Germination requires a bare, nutritious and humid or moist site. Because of their rapid height increment at the seedling and sapling stages, the pioneer trees compete successfully with the herbaceous ground vegetation.

Pioneer trees are considered to improve the micro-environment and activate the nutrient cycle. Their litter contains more nutrients and decomposes faster than that of conifers. Birch litter restricts decay fungi which cause stem and root rot in some coniferous species. At least hypothetically, alternating broad-leaved and coniferous dominance is required to maintain the productivity of some boreal sites.

Intermediate trees. Tree species with both pioneer and climax qualities can be called intermediaries. They are able to occupy bare and treeless sites and, under specific conditions, form true or seemingly true climax stands. Dahurian larch (Larix gmelini) is both a pioneer and climax tree in the northern part of far eastern Asia. Together with scrubby Japanese stone pine (Pinus pumila) it is the only tree that can endure the extremely harsh climate of this region.

The status of Scots pine (Pinus sylvestris) is ambiguous. In spite of obvious pioneer qualities, it is often described as a climax tree on dry land, barren sands and gravel. The climax nature of Scots pine, however, seems to be based on repeated forest fires which prevent the true climax trees, such as spruce, from forming a dominant stand on barren sites where it is very slow growing. Invading spruce undergrowth does not have enough time to conquer the site before a new fire sweeps it away. In western Eurasia, pine may be a true climax tree on most barren sands and peat that are too poor for spruce and fir.

Climax trees. The role of the climax trees in the boreal forest ecosystem is to invade stands formed by pioneer trees, dominate them and create a micro-environment that disadvantages other competing species. The main mechanisms are shade tolerance and tolerance of suppression. Growth is slow in youth but rapid when released from suppression, and it continues to an older age than is the case for most pioneers. The biomass per hectare is considerable when given an appropriate quality site and their shading crowns and litter create a micro-environment that favours raw humus.

In good years seed crops are abundant, thereby providing great numbers of seedlings able to await an opportunity to conquer the site. Nutrient and water drainage requirements vary according to species. Most climax species require rich loamy and clayey soils as well as plenty of moving water, although some can endure barren conditions. Self-thinning and tree - size stratification are relatively weak and, consequently, the number of trees per hectare and the size and age variations are greater than in the case of pioneers. Maturity age varies according to species. Stands of some species mature and degenerate at a relatively young age, while some reach an old age, although not as old as the longest living pines and larches. In North America, the primary climax species include black spruce (Picea mariana), white spruce (P. glauca), red spruce (P. rubens), Eastern hemlock (Tsuga canadensis), Eastern white cedar (Thuja occidentalis) and balsam fir (Abies balsamea). European and Asian climax species include Norway spruce (Picea abies) and its variant Siberian spruce, Yeddo spruce (P. jezoensis), Sachalin spruce (P. glehnii), Siberian fir (Abies sibirica), Khingan (Okhotsk) fir (A. nephrolepis) and Sachalin fir (A. sachalinensis).

Climax trees suffer more from drought, frost, windthrow, insects and fungi than most pioneers and they are extremely sensitive to forest fires. Fires affect about one million ha and pests about 0.5 million ha of stocked forest land per annum in Canada. In Norway, Sweden and Finland these losses are negligible. However, the negative impact of reduced forest fires on soil fertility also needs to be considered [Ed. note: see second Kuusela article in this issue]. Forest fires affect at least one million ha per annum in the area of the former USSR. It is estimated that approximately 140 million ha of forest land, cut or burnt, are currently under scrub vegetation and in the slow succession toward climax conifer domination.

Human impacts

Beyond natural forces, human disturbances affect tree stand successions and composition. Before the preindustrial period, most of the boreal zone was beyond permanent human settlement. The climate was hostile and infertile soils restricted agriculture which was based on primitive tools and manual labour. The slow-growing human population was concentrated in the warmer temperate zone and in those subtropical and tropical areas where soils were fertile and eventual water shortages could be compensated for by irrigation.

When Europe's population exceeded the production capacity of the prevailing agricultural technology, humans started to colonize the boreal zone. The first colonizers lived on hunting, fishing, the shifting cultivation of scanty crops and cattle raised on forest pastures. At first, people did not change the boreal forest environment significantly, although there is evidence that nomadic pasturalists deliberately introduced fires to improve pastures for their herds.

By the nineteenth century, the virgin forests within the reach of manual labour and waterways had been thoroughly changed by shifting cultivation, forest pasturing, tar extraction, charcoal burning, the construction of wooden houses and the use of wood for fuel and many other household purposes as well as for ships and boats. During the era of shifting cultivation and forest pasturing, human activities disturbed the natural successions and maintained a kind of false climax, favouring pioneer and intermediate species.

Shifting cultivation decreased rapidly from the end of the nineteenth century through to the beginning of the twentieth century, and spruce started returning to its earlier sites. However, the same period saw the advent of industrialized production and, consequently, a rapidly increasing need for raw materials, including wood. The coniferous forests became a source of wood for the increasing population. Homogeneous virgin wood stocks were seen as huge mines that could be profitably exploited by loggers and, later, harvesting machines - and wood production became the prime disturbance to the boreal forest ecosystems.

Environmental threats to forest on the Kola peninsula near Montsegorsk, Russia (1991)

The deliberate growing and harvesting of trees by proper logging and silvicultural methods began when populations increased to the extent that the need for wood exceeded the available natural resources under humankind's jurisdiction. Silviculture, based on the results of scientific research and practical experience, commenced in the eighteenth century in central Europe and in the early twentieth century in Scandinavia. In Canada and the former USSR, until very recently forest resources were considered limitless and certainly their physical potential does still exceed the demand for wood. There are huge areas of virgin forests, especially in the Asian region of the former USSR. On the other hand, over large areas of Russia, logging seems to have reached the limits of sustainable production. The farther logging extends from the mills and forest product consumption centres into the wilderness, the greater the costs of logging, transport and infrastructure become. The risk of exceeding the economic sustainability of wood supply has promoted efforts to implement silvicultural measures that are feasible and profitable in these extensive conditions.

TABLE 4. Annual wood removals in boreal countries, 1978-82 annual averages

	Alaska	Canada	Norway	Sweden	Finland	Nordic countries	Former USSR	Total	Share of world total
(1000 ha)									(%)
Exploitable closed forest	4512	214780	6600	22230	19445	48275	534500	802067	41
Coniferous	...	137910	5280	21103	17884	44267	405900	588077	591
(Million m3)
Growing stock o.b.	1294	22958	575	2264	1568	4407	66996	95655	45
Coniferous o.b.	1222	18310	459	1934	1290	3683	54669	77884	53
(1000 m3)
Net annual increment o.b.	3583	356000	17310	78500	61930	157740	750300	1267623	31
Coniferous o.b.	1863	267000	13710	65155	48119	126984	601500	997347	45
Removals per annum u.b.	3132	152048	9103	50404	42460	101967	357220	614367	21
Coniferous u.b.	2999	139459	8339	43251	34464	86054	297680	526192	45
Industrial timber u.b.	2900	147182	8461	46278	38376	93115	277420	520617	37

Note: o.b. = over bark: u.b. = under bark.
¹Estimate.

Threats caused by environmental changes

In the recent past, human-produced emissions have changed the composition of the atmosphere, while precipitation has changed to such an extent that considerable effects on the boreal ecosystems are inevitable. Sulphur and nitrogen fumes have killed trees in the immediate vicinity of the emission sources, although the forest has recovered in most cases. Nevertheless, exceptionally large emissions, especially from mining industries, have killed off entire forests in limited areas. The effects of radioactive fallout on forests following the Chernobyl incident in Belarus are still unclear but will certainly be significant.

TABLE 5. Boreal region removals as a proportion of world and boreal totals, 1978-82 annual averages

	Alaska	Canada	Nordic countries	Former USSR	Total
(Percentage of world total)
Removals	0.1	5.2	3.5	12.2	21.0
Coniferous	0.3	11.9	7.3	25.4	44.9
Industrial timber	0.2	10.4	6.6	19.7	36.9
(Percentage of boreal total)
Removals	0.5	24.8	16.6	58.1	100.0
Coniferous	0.5	26.5	16.4	56.6	100.0
Industrial timber	0.5	28.3	17.9	53.3	100.0
(m3/ha)
Removals	0.69	0.71	2.11	0.67	0.76

Some of the liveliest discussions have centred on forest decline as a result of acid rain. Observed losses of foliage have often been considered as indicators of forest decline related to acid precipitation. However, the situation is unclear because the impact of many other factors causing defoliation, including excess density, overmaturity, drought and cold periods and poor resistance of natural regrowth, is not fully understood.

Utilization of boreal forest resources

Wood removals

The approximate areas of annual final cutting are: 0.9 million ha in Canada, 0.4 million ha in Norway, Sweden and Finland and at least two million ha in the former USSR. Per annum wood removal (harvested timber assortments) in the boreal countries and Alaska around 1980 as well as their shares in the world totals are presented in Table 4. Country shares in the world and boreal totals are given in Table 5. It should be noted that, in both the tables and the data that follow, except when specifically noted, figures refer to countrywide data. Specific data covering the boreal forests are generally unavailable. but in all of the countries with boreal forest resources, removals and production from boreal forests make up a substantial portion of the total.

Commercial thinning of birch stands at 25 to 30 years

Commercial thinning of 30-year-old trees

Nordic removals per hectare are about three times greater than those of other boreal areas. From the beginning of the 1960s to the first half of the 1980s, annual removals increased by 30 percent in the world as a whole, and by 35 percent in Canada. In the Nordic countries, removals increased up to 1975 but then decreased to the level of the beginning of the 1960s. In the former USSR, removals decreased by about 8 percent around 1975.

There are indications that Canadian removals are continuing to increase more rapidly than the world mean. Removals in the area of the former USSR have also started to rise from their lowest levels. In spite of increasing industrial production, in the Nordic countries removals have stabilized at the level reached around 1980. Although removals are 15 to 20 percent less than the maximum allowable cut on the basis of sustained yield, the bulk of Nordic forests are under private ownership and the owners are not willing to utilize them fully. The need for wood has consequently been satisfied by increased imports.

Forest industry production

The boreal countries' forest industry and wood production around 1980 are presented in Table 6, and these countries' shares in the world totals are given in Table 7. As can be seen, the boreal countries produced an average of 52.8 percent of the world's output of mechanical pulp and newsprint, 37.6 percent of sawnwood and 21. I percent of paper end paper board from 1978 to 1982.

Canada is a major producer of sawnwood, mechanical pulp and newsprint while the area of the former USSR produces considerable quantities of sawnwood and wood-based panels. The Nordic countries, on the other hand, are major producers of paper and paper board as well as writing and printing papers in the case of Finland. Canadian production continued to increase rapidly during the 1980s in all major areas, especially in that of writing and printing papers.

TABLE 6. Forest industry production in boreal countries, 1978-82 annual averages

	Canada	Norway	Sweden	Finland	Nordic countries	Former USSR	Total	Share of world total
(Tonnes)								(%)
BASIC INDUSTRY
Sawnwood	18174	1001	4742	3714	9457	42948	70579	38
Wood-based panels	2254	267	846	745	1858	4926	9039	19
Mechanical pulp	7386	886	1870	2276	5032	1773	14191	53
Chemical and other pulp	11614	628	6645	4612	11885	7274	30773	32
Total	39428	2782	14103	11347	28232	56921	124581	35
PAPER AND PAPER BOARD
Newsprint	8641	600	1441	1482	3523	1384	13548	53
Writing and printing	1453	301	978	2015	3294	1166	5913	15
Other	3187	437	3624	2268	6329	6376	15892	16
Total	13281	1338	6043	5765	13146	8926	35353	21

TABLE 7. Boreal countries' share in world forest industry production, 1978-82

	Canada	Norway	Sweden	Finland	Former USSR	Total
(Percentage)
Production
Timber	5.2	0.3	1.7	1.5	12.1	20.8
Sawnwood	9.7	0.5	2.5	2.0	22.9	37.6
Wood-based panels	4.8	0.5	1.8	1.6	10.4	19.1
Mechanical pulp	27.5	3.3	6.9	8.5	6.6	52.8
Chemical and other pulp	12.1	0.6	6.9	4.8	7.6	32.0
Total basic industry	11.0	0.8	3.9	3.2	15.9	34.8
Newsprint	33.7	2.3	5.6	5.8	5.4	52.8
Writing and printing paper	3.6	0.7	2.4	5.0	2.9	14.6
Other paper products	3.1	0.4	3.6	2.3	6.3	15.7
Total paper and paper board	7.9	0.8	3.6	3.5	5.3	21.1
Value of exports
Roundwood	2.0	0.4	0.7	1.5	10.6	15.2
Sawnwood	26.3	0.5	10.5	8.4	9.1	54.8
Wood-based panels	5.6	0.4	3.3	7.7	3.9	20.9
Wood pulp	34.6	2.5	15.8	8.9	3.8	65.6
Paper and paper board	20.8	2.8	13.3	13.6	2.0	52.5
Total	20.0	1.7	10.3	9.3	5.3	46.6
Value of imports
Roundwood	0.9	0.6	1.9	1.2	0.3	4.9
Sawnwood	1.8	0.9	0.5	0.1	0.6	3.9
Wood-based panels	1.9	1.4	1.9	0.2	0.8	6.2
Wood pulp	0.8	1.1	0.3	0.2	1.4	3.8
Paper and paperboard	1.2	0.6	0.9	0.3	2.8	5.8
Total	1.3	0.8	1.0	0.4	1.5	5.0
Population	0.5	0.1	0.2	0.1	6.0	6.9

TABLE 8. Value of exports and imports of forest products, 1978-82 annual averages

	Exports			Imports
	Value	Share of world total	Per caput value	Value	Share of world total	Per caput value
	(Million US$)	(%)	(US$)	(Million US$)	(%)	(US$)
World	48144	100.0	11	54040	100.0	12
Canada	9650	20.0	403	701	1.3	29
Norway	802	1.7	196	438	0.8	107
Sweden	4949	10.3	596	527	1.0	63
Finland	4502	9.3	942	221	0.4	46
Nordic countries	10253	21.3	597	1186	2.2	69
Former USSR	2548	5.3	10	789	1.5	3
Boreal total	22451	46.6	73	2676	5.0	9

In the Nordic countries, the production of Sawnwood has stabilized over the past 15 years, while that of wood-based panels has decreased since 1973. The average profitability of sawmilling has been poor. High production and, especially, transport costs have led to decreased exports of particle board and fibreboard.

The Nordic countries' specialization in paper products continued throughout the 1980s. The increase in their production of mechanical pulp in the 1970s was greater than it was for chemical pulp, but chemical pulp was a profitable product in the late 1980s. This, together with the uncertainty of obtaining electricity supplies at a reasonable price, increased the share of chemical pulp, mainly in the creation of new capacity.

The former USSR's production had recovered to some extent from the stagnation of the 1970s. However, actual production has not reached the targets set by planning organizations and there are considerable difficulties in satisfying the domestic demands for all forest products because of the old age and small size of many mills and because of growing demands to reduce emissions. Moreover, recent political changes may have far - reaching and unpredictable effects on forest industries.

The value of boreal countries' forest exports and imports as well as the values per caput and country shares in world trade are presented in Table 8. Boreal countries accounted for 46.6 percent of world exports and 5 percent of imports. In terms of specific products, the share of sawnwood exports was 54.8 percent; wood pulp, 65.6 percent; and paper and paper board, 52.5 percent (see Table 7).

The future of the boreal forests

Boreal forests and forestry are at the centre of the many vital issues and contradictory challenges facing humankind at the end of the twentieth century. World population has passed the 5000 million mark and is continuing to grow exponentially while the demand for material products is growing even faster. The developing countries are struggling to approach the material standards of the industrialized countries while the post-industrial countries aim for still higher standards.

On the basis of demographic, production and consumption statistics, the inevitable conclusion is that the demand for wood production from boreal forests will increase. However, the physical dimensions of the boreal forest resources may lead to exaggerated estimates of the feasible potential of wood production. Forests located far away from populated areas and the users of wood, in difficult terrain, such as mountains, or in extremely rigorous climates are beyond the economic limits of logging and transportation. In addition, the harsh northern climate, desiccating winds, erosion and avalanches on mountain slopes - even those relatively close to population centres may prevent the full utilization of the boreal forests' potential. According to the statistics of the ECE Timber Committee, the areas of unexploitable closed forest and their proportion to the total closed forest in 1980 were: Canada, 49.3 million ha (19 percent); Norway, one million ha (14 percent); Sweden, 2.2 million ha (9 percent); Finland, 0.4 million ha (2 percent); the former USSR 257.1 million ha (32 percent). Most of the Alaskan forests in the boreal zone proper are also excluded from wood production.

The task ahead, therefore, is to harmonize the growing and harvesting of wood in accessible areas with other benefits demanded from these forests. In Canada and Russia the most crucial questions from the point of view of sustainable wood production are what species will afforest the cut-and-burnt sites, what the time-scale of the natural succession to valuable coniferous stands is and which silvicultural measures to accelerate successions in different site conditions are feasible and profitable. Important individual measures include the recommended combinations of the tending and spacing of seedlings and sapling stands; natural versus artificial stand establishment; thinning schedules for the production of usable wood; and the use of machines as well as other equipment.

In many regions where exploitative harvesting has been the common practice, there is a growing need to increase the production per unit area of exploitable forest land and to guarantee the sustainable production of wood with silvicultural measures. The supply of wood cannot be based on the past practice of opening new and increasingly distant virgin forests for exploitation.

There are unavoidable boundaries beyond which the costs of logging, transport and infrastructure exceed the price that consumers of wood are willing to pay. In all probability, the area of forests in which the production of wood is partly or totally prohibited in order to protect undisturbed nature, among other environmental reasons, will increase. The remote areas of Canada, far-away Siberian forests and forests in other areas of Russia where clear-cutting is prohibited are current examples.

Silvicultural options

More and more new seedling stands will be established by silviculturally guided natural seeding; developing undergrowth seedling stands made available by the harvesting of mature trees; and artificial planting and seeding. Young stands will be tended and spaced, while thinnings that produce usable wood will be adopted to a much greater extent than at present. One of the most profitable measures is to clean away low-value trees and scrub from the seedling and sapling stands growing on the cut-and-burnt sites. This accelerates the successional development leading to valuable climax stands. However, more research and experience are required to guide successions and monitor tree species compositions.

In the current stage of exploitative forestry, thinnings are often considered unprofitable. This may be the case in conditions where the self-thinning ability of the stand is poor and the primary aim is to grow pulpwood. Young stands are spaced according to the number of trees per hectare of the final crop, and mortality losses are small. On the other hand, if the aim is to grow good-quality saw logs, thinning with suitable machinery is probably a profitable form of management. Thinnings reduce mortality losses and logging residues, shorten the rotation period and increase the value of the final crop by increasing the mean diameter while decreasing the diameter range of the crop trees.

Opinions concerning the economy of thinnings may be based more on logging tradition than on the results of unbiased analyses of the economy or available technology. In exploitative forestry, a common harvesting method consists of felling, skidding delimbed stems or total trees to a roadside and transporting them by semitrailer trucks to timber depots or users. This method is impossible, or at least very expensive, when applied to thinnings.

On the other hand, technology developed in Scandinavia, where timber assortment logging has a long tradition, may be profitable in thinnings even outside this region. Trees are felled, delimbed and bucked by manual labour and power saw or by medium- or small - sized harvesters. Timber assortments are moved to a roadside by front-end loaders and transported by trucks equipped with loaders and trailers.

Problems of under utilization

In the Scandinavian countries, the greatest problem is the inability to utilize forest resources to their fullest. In these countries at the end of the 1980s, the annual net increment of stem volume, over bark, in exploitable closed forest was about 178 million m³ and of annual fellings about 144 million m³. Thus, underutilization is about 19 percent. Consequently, stands are becoming denser and older, with higher natural losses.

The higher the area of dense and old stands with an increasing dominance of spruce, the greater the risk of degrading the nutrient regimes, particularly under conditions in which repeated forest fires have been eliminated. Degradation can be prevented only by sufficiently intensive final cuttings, small-scale successions in the regeneration stages and appropriate silvicultural measures such as the changing of tree species, site preparation and fertilization.

Norway, Sweden and Finland have all the physical prerequisites for effective forest management. Silvicultural and harvesting techniques are modern, the infrastructure is satisfactory and stumpage prices are high. Nevertheless, the private forest owners and the various organizations concerned are not willing to utilize the production potential to its utmost. Public opinion prefers forests devoid of the marks of wood production.

The situation is unlikely to change in the near future, in spite of arguments against the naturalistic point of view, "let it grow": "While it is true that it is cheapest to sit back and allow the forest to develop in the absence of further interference, it does not necessarily follow that the greatest net return will similarly be realized either in tangible or intangible values" (Spurr and Barnes, 1980).

Environmental considerations

According to often contradictory scenarios, carbon dioxide and other greenhouse gases may increase the temperature and considerably change wind and precipitation conditions over the next few decades. In the boreal zone, the temperature is expected to rise more in the winter than in the summer and precipitation is likely to increase.

From the point of view of forestry, rising temperatures and increasing precipitation would have both beneficial and harmful effects. Forest productivity would obviously increase. The competitive ability of broad-leaved trees with respect to conifers would be improved so that, without silvicultural measures, the species composition would develop slowly into temperate mixed and broad-leaved summer green forests.

However, the valuable species compositions dominated by conifers could be maintained, as are the conifers in central Europe where oak and beech are the natural dominators. If a species loses its ability to regenerate naturally, new stands can be established artificially.

The risk of insect and fungal damages would obviously increase. New pest species from temperate zones would invade the boreal areas quicker than the genotypes of resistant trees could be introduced. There would therefore be the need for more preventive measures than are currently in force.

Boreal forests proper would be pushed northward and would form a narrow belt between the Arctic Ocean and temperate mixed forest zone. Permafrost would melt over extensive areas, causing damage to the current infrastructure and transport systems.

Efforts to develop boreal forestry and outline the future of boreal forest in a new environment such as that described should be based on research and experience within an ecological frame of reference and with special reference to tree species dynamics.

Bibliography

Bonan, G.B. & Shugart, H.H. 1989. Environmental factors and ecological processes in boreal forests. Annu. Rev. Ecol. Syst., 20: 1-28.

FAO/ECE. 1985. The forest resources of the ECE region. ECE/TIM/27. Geneva.

FAO/ECE. 1989. Outlook for the forest and forest products sector of the USSR. ECE/TIM/48. Geneva.

Kauppi, P. & Posch, M. 1985. Sensitivity of boreal forests to possible climatic warming. Climatic Change, 7: 45-54.

Kuusela, K. 1987. Northern boreal forest resources, their utilization and ecology. Introductory paper presented at IUFRO Symp., 16-22 August 1987, Rovaniemi, Finland.

Larsen, J.A. 1980. The boreal ecosystem. New York, Academic Press.

Spurr, S.H. & Barnes, B.V. 1980. Forest ecology. New York, John Wiley.