Boreal forested wetlands — What and where in Alaska

Forest Ecology and Management, 33/34 (1990) 425-438

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Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

Boreal forested wetlands- What and where in Alaska Willem W.S. Van Hees Pacific Northwest Research Station, Forest Inventory and Analysis, 201 E. Ninth Ave. Suite 303, Anchorage, AK 99501 (U.S.A.)

ABSTRACT van Hees, W.W.S.,1990. Boreal forested wetlands-Whatand wherein Alaska. ForEcoLManage., 33/34:425-438. Throughout interior Alaska there are extensive areas of forested wetlands. Tree cover on these lands is composed primarily of slow-growing black spruce (Picea mariana (Mill.) B.S.P. ) but also included are more productive poplar (Populus spp. ) stands. Inventory methods developed by USDA Forest Service, Forest Inventory and Analysis (FIA) Anchorage show promise for low costs of per-unit-area estimation. Current utilization of this resource is minimal largely due to low human-population levels, inadequate economic and physical infrastructures, and the dispersed nature of the resource. Utilization studies have examined such products as 'press-logs' and particle-boards.

INTRODUCTION

Forested wetlands, as a subset of wetlands in general, are not limited in range to warmer climatic areas of the world. Extensive areas of forested wetlands exist in boreal regions. This paper is an overview of the nature, locations, uses, and some of the environmental difficulties attendant to harvest of boreal, forested wetlands in Alaska. Alaska is not always the frozen winter scene that many people who have not had a chance to become acquainted with it visualize. Although much of the subsurface is frozen all year (permafrost), most of the surface is not. In fact, m u c h of Alaska is considered by many to be a wetland for most of the non-frozen period of the year. Many ecologists, foresters, botanists and other 'plant people' have tried to define what is and is not a wetland. A fairly typical working definition can be taken from Frayer et al. (1983): "... land where saturation with water is the dominant factor determining the nature of soil development and the types of plant communities living in the soil and on its surface". In addition, one or more of the following is generally true: ( 1 ) at least periodically the land supports predominantly hydrophytes; (2) the substrate is predominantly un-

Elsevier Science Publishers B.V.

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drained hydric soil; or (3) the substrate is non-soil and is saturated with water or covered by shallow water at some time during the growing-season of each year. With such a definition in mind, some have suggested that almost all of Alaska is a wetland. A substantial segment of Alaska is soggy when it is not frozen. In summer, much of the tundra is akin to a wet sponge; mountainsides are often soggy due to melting snow caps (often resulting in solifluction); there are over 3 million lakes (Eppenback and Foster, 1983); and there are hundreds of thousands of hectares affected by river meanders. There is much land-area in Alaska where water is a factor affecting soil development. What constituents a wetland is fairly definable, but it is a bit more complex when the additional modifier, 'forested', is added. One now finds it necessary to establish what is forested, which in turn, often leads to establishing 'what is a tree?'. Although there are many nebulous descriptions of what a tree is, scientists like to quantify such things. Little (1979) allowed that there is no

Fig. 1. Generalized world distribution o f boreal forests.

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uniform definition of a tree. He did, however, have a commonly used and accepted definition: "woody plants having one erect, perennial stem or trunk at least 7.5 cm in diameter at breast height, a more or less definitely formed crown of foliage and a height of at least 4 m". A colleague suggests: "if you find a plant and you can't climb it, it's not a tree". Now, how many trees make a forest? This question usually devolves to a matter of establishing an acceptable spacing limit. The U.S. Department of Agriculture, Forest Service (USFS) and Soil Conservation Service (SCS) have agreed that forest land is that "with at least 25% tree canopy cover or land with at least 10% of normal stocking by forest trees of any size, including land formerly having had such tree cover and that which will be naturally or artificially reforested". One last modifier must be considered before a description of the focus of this paper is complete. That is - What is a boreal forest? Boreal generally means 'northern'. The boreal forest is a circumpolar region extending from just south of the north polar seas to southern Canada, well into interior Soviet Union, and most of the Scandanavian countries (Fig. 1 ). It is generally characterized by various species of spruce (Picea spp. ), birch (Betula spp. ), and larch (Larix spp. ). TYPES OF BOREAL FORESTED WETLANDS IN ALASKA

In a pilot study performed for the survey of wetlands and deepwater habitats in Alaska, saturated, palustrine (marshy) forest and flooded palustrine forests were estimated to cover 19.3 and 21.8 million ha respectively (Frayer et al., 1985 ). Not all of this area is strictly boreal, but it is all in Alaska, and makes up about 1/4 of the total state area of 153 million ha. Within these two broad categories are vegetative types classified by descriptive systems of different researchers and natural-resource agencies; discussing types of boreal forested wetlands using information from these diverse sources may be confusing. Viereck et al. ( 1986 ) describe two black-spruce communities that fit in the palustrine-saturated category; upland black spruce, and lowland black spruce. Although not all of the upland category is strictly palustrine, it is very wet. (The following descriptions follow Viereck et al. (1986).) Upland black spruce (Picea mariana Mill.) is widespread in interior Alaska, is generally found on north slopes at all elevations where forests occur, on ridge tops, and most slopes when found above 400 m elevation (on drier sites at these elevations, white spruce (P. glauca (Moench) r o s s ) is more common). Permafrost is present within 50 cm of the surface throughout the summer, soils are loessal, with a mottled, saturated, silt-loam subsoil. Fire is important in succession and re-vegetation is rapid. Within 25 years after fire, willows (Salix spp.) and alders (Alnus spp.) dominate. After 30 years the tree canopy

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becomes dominant, feather mosses develop rapidly, and, after canopy closure, vegetative change slows substantially. Lowland black-spruce sites are generally old river terraces or small valley bottoms. Vegetation is similar to upland black spruce but more hydrophytic (more Sphagnum mosses than feather (Hypnum spp. ) mosses), tussocks are more abundant, and tamarack (Larix laricina (Du Roi ) K. Koch ) and birch are scattered throughout. Permafrost is common, and the most important disturbanc¢ is the thaw/pond cycle, although disturbance due to fire can still be significant. (In this cycle the ice mass in the soil thaws, a pond develops, soil subsidence occurs, the ponds are gradually filled, and the forest is re-established. ) The soils are uniformly poorly drained, shallow to permafrost, with a mottled, gray, silt-loam subsoil. Forest succession is similar to upland sites. For the purposes of vegetation inventory, Forest Inventory and Analysis (FIA), Anchorage, Alaska, has adopted a vegetation classification system where forests are characterized as coniferous vs. deciduous, open vs. closed, and short vs. tall. Although this system is in place for continuous inventory work, the results of only one inventory utilizing this have been published (Anonymous, 1986). It is from this work, in the Susitna River Basin (Fig. 2 ), that the following discussion is derived. Although specific attention was not directed at forested wetlands, four of the vegetation categories recognized in the inventory include forested wetlands: short stands of black spruce in both the open and closed coniferous categories, and cottonwood (Populus spp. ) stands in both the open and closed deciduous categories. Open stands have between 10 and 50% crown cover and closed stands have greater than 50% crown cover. Closed, short, black-spruce stands are characterized by a tree canopy less than 9 m tall, are on wet a n d / o r cold sites, and usually form islands and stringers in bog areas or transitions between bogs and drier-site forests. The understory is usually a thick moss a n d / o r sedge mat. Open, short, black spruce stands are generally bog types only, are less than 4.5 m tall, and the trees are usually of very poor form. Closed cottonwood stands are found in variety of locations depending largely on stand age. Young stands are most commonly found on new islands and on the downstream end of old islands. Medium to old stands are generally found within 2 km of rivers. Most are on alluvial soils and are flooded annually. Open cottonwood stands are segregated into two subheadings according to elevation. The high-elevation phase is often mixed with alder and willow and sometimes grows along flowing water on high elevation flats. The low-elevation phase is found on major river flood plains growing with a confusing mixture of other types such as spruce, open birch, alder, and grasses. A fifth vegetative-cover class, marginal in its 'forest-ness', is the tall shrub class, considered by FIA to be non-forest due to lack of 'tree' cover, but sub-

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TABLE 1 Areas of forested wetland vegetative cover classes in the Susitna River Basin, Alaska, 1980 Vegetative cover class Closed conifer: Short black spruce Open conifer: Short black spruce Closed deciduous: Cottonwood Open deciduous: Cottonwood Tall shrub: Alder/willow Total wetland Total unit area

Area (ha)

97 402 236 488 68 707 110 981 216 559 730 137 6 478 666

stantial amounts of woody biomass exist in this class. This category has a mixture of large alder and willow on frequently flooded ground such as new river islands and point bars. Often, young open cottonwood is found mixed in with the willow and alder. Within the Susitna River Basin inventory unit, 6.5 million ha in size, approximately 11% of the total area and 15% of the vegetated area is covered with the above five forested wetlands (Table 1 ). PRODUCTIVITY OF BOREAL FORESTED WETLANDS

Growth Productivity in terms of annual woody tree growth is rarely above 3.5 m 3 h a - 1 year- 1 on the best sites in interior Alaska. These sites are often bottomland (river bottom) with spruce and, other than an occasional flooding, are not strictly speaking forested wetlands. Generally, FIA does not estimate annual tree growth on forest land incapable of producing at least 1.4 m 3 h a year- ~of gross growth at culmination of mean annual increment (MAI); most boreal forested wetlands (excepting cottonwood stands) in Alaska produce less than this. However, estimates of growth on lands capable of at least 1.4 m 3 h a - ~MAI are indicative of the best that can be expected on most forested wetlands given the current state of non-management. Currently, average net annual growth for all stands, on good sites and poor, throughout interior Alaska is about I. 1 m 3 ha -~. The best forested-wetland sites may be more productive, but on the whole, most forested-wetland sites are equally or less productive.

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Biomass production Just as tree growth is not high in the boreal forest, standing biomass or annual biomass production are not high in comparison with tempei-ate wetlands. In the mature upland-spruce type, growth is slow, the tree canopy is upwards of 60% closed, there are between 1400 and 4000 trees h a - 1, standing-tree, oven-dry biomass is between 2000 and 10 000 g m 2, and tree productivity is between 100 and 150 g m 2 year- 1. Tree and forest productivity in the lowland black spruce c o m m u n i t y is less. Standing tree biomass is, at most, 1500 g m 2 and annual tree biomass growth is about 70 g m 2 year- 1 (Viereck et al., 1986). Yarie (1983) developed estimates of current and potential biomass productivity for a variety of mature plant communities in the Porcupine River drainage of interior Alaska (Fig. 3 ). Although he did not categorize vegetative communities according to whether or not they were wetlands, some observations are available for communities growing on poorly drained sites or flood plains. Among the poorly drained forest communities he examined are open and closed black spruce forests which typically grow on saturated soils. Some of the flood-plain communities are included in the closed white-spruce forests. Current oven-dry annual tree-biomass production for the Porcupine River drainage is about 26.0 g m 2 for open black spruce and 18.5 g m 2 for closed

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black spruce; for the closed white-spruce communities the estimate is 79.7 g m 2. Estimated potential total tree productions are 74.0, 51.0, and 137.0 g m 2 for the open black-spruce, closed black-spruce, and closed white-spruce communities, respectively. In terms of potential wood productivity only, the corresponding estimates are 16.0, 11.0, and 30.0 g m 2 year- 1. INVENTORY TECHNIQUES

Traditionally, FIA inventories throughout the United States have been aimed at developing estimates of timberland resources, typically through the use of a 2-phase sampling design using one level of remote-sensing and variable-radius ground plots. Estimates regarding other renewable resources such as marginal forestland, forested wetlands, and rangeland were secondary to timberland estimates in terms of controlling the inventory for specified error limits. The inventory system currently being examined for feasibility by FIA, the Alaska Integrated Resource Inventory System (AIRIS), is a regression-based, four-phase, unstratified, systematic sample (Winterberger, 1984). As such, it regards all aspects of the target population (all lands and water within inventory unit boundaries) as being of equal importance. Thus, if there is an abundance of forested wetlands, those will be sampled more heavily than lessabundant vegetation classes. Attributes of linear vegetative communities, such as river-bottom classes, will be difficult to capture as a result of systematic, grid-based, plot location. Briefly, AIRIS evaluates four sampling levels, three remotely. The levels are Landsat (SAT) high-altitude photography of 1:60 000 scale (HAP), largescale photography of 1:3000 scale (LSP), and a ground sample. At each level of the sampling frame, an 8-ha plot is evaluated. On SAT, these plots are located every 5 km, every 10 km on HAP, every 20 on LSP, and every 40 km on the ground (Fig. 4). Although the sampling design of AIRIS is extensive in terms of numbers of ground plots, the types and amounts of data gathered at each site are substantial. Of particular value is the horizontal/vertical profile (HV), first developed and used by researchers at the Southeastern Forest Research Station (Cost, 1979 ). The HV is a relatively simple and reproducible method of describing both the horizontal and vertical structure of the vegetative community at a site. In addition to describing structure, it may be useful for quantifying amounts of browse available to wildlife, developing vegetative diversity measures, and development of biomass-equation coefficients. In a multiresource context, the large-scale photo and ground-measurement portions of the AIRIS system provide a possible alternative to the more typical 2-phase timber inventory. They expedite efforts to quantify renewable re-

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Fig. 4. Schematic diagram of the Alaska Integrated Resource Inventory System (AIRIS) sampling frame.

sources (in addition to timberland capable of 1.4 m 3 h a - l MAI ) in areas such as interior Alaska where access is difficult and inventory areas are extensive. UTILIZATION CONSIDERATIONS

Sampson et al. (1988) conducted a study to examine possibilities for increased production of forest products in interior Alaska. They concluded that white-spruce lumber is the likely near-term target because local demand, size, and availability make it attractive. Two major problems attendant to in-

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creased utilization are the dispersed nature of the harvestable timber and associated access problems. A significant a m o u n t of space is given in this presentation to black-spruce harvesting and utilization considerations (size, use, site ) because black spruce is a significant component of the wetland boreal forest. As such, it has attracted attention in other locations such as the Clay Belt Region of the Province of Ontario, Canada. Black spruce forests capable of producing 1.4 m 3 h a - ~ year- ~ cover about 770 000 ha in interior Alaska, 5% of the total interior area. This level of productivity corresponds to FIA m i n i m u m s for inclusion of lands in the timberland category. Although precise estimates of the extent of all black spruce regardless of productivity are scarce, preliminary work by FIA indicates that black spruce grows on 30% or more of interior Alaska. Tree size

The boreal forest is not known for trees of magnificent dimensions. The typical black spruce may be as much as 20 m tall and 23 cm in diameter at breast height on a good site. Also, volumes per unit area tend to be low. In the Tanana Valley of interior Alaska, average volume for all forest types is near 70 m a / h a (van Hees, 1983). Present uses

Currently, interior Alaska's forest resource is little utilized. Major uses are for firewood, house logs, and some local lumber production. A few cabinet shops use local birch, cottonwood, and spruce but their d e m a n d does not have much influence on supply. Very little, if any, of the d e m a n d has an effect on forested wetlands other than that the wetland site may be disturbed in the process of extracting timber from the better sites. Potential uses

During the last decade, much land has been cleared for agricultural purposes through efforts by the Alaska state government to promote agriculture. Much of this clearing occurred in black-spruce forests. Sampson and Ruppert ( 1983 ) studied the possibilities of using residues from some of these clearing efforts as firewood fuel. With the assistance of a mill in Oregon, they produced densified fuel logs composed of four different combinations of landclearing residues: black spruce, moss, a mixture of paper birch and aspen, and a mixture of black spruce and moss. Logs made of spruce and birch/aspen were an acceptable alternative to cordwood for those involved in the study. Logs with moss in them burned too slowly, were smoky, and left a high pro-

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portion as ash. Storage tests showed that densified logs stored in covered, unheated areas tended to decompress over winter but those stored in heated facilities did not. Two studies in the recent past examined the possibilities for particle-board production in the Interior (Harpole et al., 1977; Anonymous, 1982). Both concluded that it was not feasible unless markets developed in the Pacific Rim nations. Plywood and pulp production are also not at present considered promising. Two physical factors recognized as hindering near-term development of any of the interior forests, much less the forested wetlands, are access and infrastructure. Infrastructure here means the physical plants and systems to harvest, move, and process forest products. In comparison with other sections of the United States, Alaska has almost no roads. There are approximately ten major highways in the interior with almost no interconnecting spur roads. Almost three-quarters of the state is not road-accessible. Much of the interior forest is accessible only by air or by river if one does not wish to walk. There is only one railroad in interior Alaska. There are no full-time, relatively highcapacity lumber mills in the Interior. Before any forested wetlands are considered for forest management, the more-productive sites will be utilized, demand must increase, and necessary infrastructures must be developed. In an effort to stimulate development of the timber economy in interior Alaska, the State Division of Forestry, Department of Natural Resources ( D N R ) has begun studies to examine the feasibility of timber harvesting in the Susitna River Basin. The area is close to Anchorage, which has a deepwater port, and is relatively close to the railroad. Additionally, the D N R has contacted major timber companies with experience in harvesting and management of boreal forests.

Site considerations Vegetation fragility Logging equipment can cause significant site disturbance during harvesting. Very-high-flotation skidders are examples of equipment that has been developed to minimized disturbance. However, the boreal forest site can be fragile and, even with new equipment, harvesting may have to occur in winter when the site is frozen and disturbance can be further reduced. In interior Alaska, a large portion of logging is carried out in the winter (Zasada et al., 1987). A component of the boreal forest that would be negatively affected by improper harvesting practices in the moss layer, a major component involved in nitrogen cycling which is easily disturbed by logging equipment. On permafrost sites, this layer may act as a nitrogen bottleneck, whereas on permafrostfree sites it can act as a nitrogen source (Weber and Van Cleve, 1981 ). The

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moss layer is also a barrier to successful white-spruce seed germination and establishment. In Newfoundland, eastern Canada, researchers are examining ecological, afforestation, and drainage considerations on fen sites, a peat-forming ecosystem (mire) with little or no Sphagnum, with a source of water and minerals outside the limits of the mire, and which is less acid than bogs (Gabriel and Talbot, 1984). Zoltai and Pollett (1983) have shown in afforestation trials that larches and pines (Pinus spp.) can grow acceptably well on fen sites; however, no mention was made of drainage efforts.

Soil disturbance Soils in boreal forest ecosystems tend to be fragile and are easily disturbed by heavy logging machinery. A major factor contributing to this fragility is the presence of permafrost. Soil temperatures vary greatly depending on the vegetative cover of the site. Not only can removal of the vegetation during harvest have dramatic effects on soil temperature regimes but an understanding of these changes may be critical to reforestation success. Viereck (1970) examined soil temperature changes due to plant succession on a river bottom in interior Alaska. He examined four sites that represent a successional sequence: feltleaf willow (Salix alaxensis Cov. ), balsam poplar, white spruce, and white spruce/black spruce (Fig. 5 ). He found that soil froze

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earliest and deepest in the earliest successional stages. Insulating moss and river alluvium probably slow freezing in spruce stands, the later successional stages. He also found that the earlier stages thawed earlier and that soil temperatures were warmer during the growing-season. But, the later stages eventually reach a conditions where the substratum remains frozen throughout the year and the area becomes a forested wetland. SUMMARY

Boreal forested wetiands are extensive throughout the northern latitudes. In Alaska there are roughly 41 million ha of forested wetlands, slightly more than three times the entire area of the state of Louisiana. Potentially, this is an extensive, if not a concentrated, resource. Although land-resource managers in Alaska are aware of the magnitude of this potential resource, specific characteristics and locational attributes are lacking. Traditional forest inventories have not generally been designed to capture information regarding this resource. Forest Inventory and Analysis Alaska, through implementation and development of AIRIS, is attempting to provide this information. Currently, large quantities of wood and fiber are not available. The dispersed nature of the resource, poor access, and lack of markets are primary reasons for the present low levels of utilization. Also, that which is produced is not widely distributed. Commercial development interests are beginning investigations into utilization of woodlands resources in Alaska. In addition to possible financial value, these forests are important in the bioeconomics of the world environment. These forests respond slowly to disturbances and must be treated with appropriate consideration of their fragility when we arrive at the need to utilize these resources.

REFERENCES

Anonymous, 1982. An investigation into land clearing methods and utilization of salvaged wood fiber from the Nenana agricultural project. Columbia Engineering/Alaska Agricultural Action Council, Juneau, AK, 95 pp. Anonymous, 1986. Timber and vegetation resources of the Susitna River Basin - Alaska. USDA Soil Conservation Service, and Forest Service, Published by U.S. Army, Fort Richardson, AK, Publications Center (not paged). Cost, N.D., 1979. Ecological structure of forest vegetation. In: W.E. Frayer, (Editor), Forest Resource Inventories: Proc. Workshop, 23-26 July 1979, Department of Forest and Wood Sciences, Colorado State University, Fort Collins, CO, pp. 29-37. Eppenbach, S. and Foster, S. (Editors), 1983. Alaska Blue Book, 1983. Dept. of Education, Division of State Libraries, Juneau, AK, 311 pp.

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Frayer, W.E., Monahan, T.J., Bowden, D.C. and Graybill, F.A., 1983. Status and trends of wetlands and deepwater habitats in the conterminous United States, 1950's to 1970's. Colorado State University Office of University Communications, Publications Service, Fort Collins, CO, 31 pp. Frayer, W.E., Monahan, T.J. and Bowden, D.C., 1985. Report on pilot study for survey of wetlands and deepwater habitats in Alaska. Unpublished Report to U.S. Fish and Wildlife Service, Contract 14-16-0009-012, 14 pp. Gabriel, H.W. and Talbot, S.S., 1984. Glossary of Landscape and Vegetation Ecology for Alaska. U.S. Department of Interior, Bureau of Land Management, Anchorage, AK, BLM/AK/TR84/10, 137 pp. Harpole, G.B., Guss, L.M., Ganes, R.C. and Grantham, J.B., 1977. Feasibility of structural particleboard manufacture in Alaska. Fairbanks Industrial Corporation, Fairbanks, AK, 128 pp. plus appendix. Little, E.L. Jr., 1979. Checklist of United States Trees (Native and Naturalized). U.S. Department of Agriculture, Washington, DC, Agric. Handb. 541,375 pp. Sampson, G.R. and Ruppert, F.A., 1983. Potential for economical recovery of fuel from land clearing residue in interior Alaska. USDA For. Serv. Pac. Northwest Res. Stn., Portland, OR Res. Pap. PNW-308, 11 pp. Sampson, G.R., van Hees, W.W.S., Setzer, T.S. and Smith, R.C., 1988. Potential for forest products in interior Alaska. USDA For. Serv. Pac. Northwest Res. Stn., Portland, OR Resour. Bull. PNW-RB-153, 28 pp. van Hees, W.W.S., 1983. Timber resource statistics for the Tanana inventory unit, 1971-75. USDA For. Serv., Pac. Northwest Res. Stn., Portland, OR Resour. Bull. PNW-109, 36 pp. Viereck, L.A., 1970. Soil temperatures in river bottom stands in interior Alaska. In: Ecology of the Subarctic Regions, Proc. UNESCO Symposium, Helsinki, 25 July-3 August 1966. Union Geographique International/Unesco, Paris, pp. 223-233. Viereck, L.A. Van Cleve, K. and Dyrness, C.T., 1986. Forest ecosystem distribution in the taiga environment. In: K. Van Cleve, F.S. Chapin III, F.W. Flanagan et al. (Editors), 1986. Forest Ecosystems in the Alaska Taiga. Springer, New York, pp. 22-43. Weber, M.G. and Van Cleve, K., 1981. Nitrogen dynamics in the forest floor of interior Alaska black spruce ecosystems. Can. J. For. Res., 81 ( 11 ): 743-751. Winterberger, K.C., 1984. LANDSAT data and aerial photgraphs used in a multiphase sample of vegetation and related resourcesin interior Alaska. In: V.J. LaBau and C.L. Kerr (Editors), Inventorying Forest and Other Vegetation of the High Latitude and High Altitude Regions: Proc. Int. Symposium. Society of American Foresters Regional Technical Conference; 23-26 July 1984, Fairbanks, AK. SAF Publ. 84-11, Bethesda, MD. Yarie, J., 1983. Forest community classification of the Porcupine River drainage, interior Alaska, and its application of forest management. USDA For. Serv. Pac. Northwest For. Range Exp. Stn., Portland, OR Gen. Tech. Rep. PNW-154, 68 pp. Zasada, J.C., Slaughter, C.W., Argyle, J.D. et al., 1987. Winter logging on the Tanana River flood plain in interior Alaska. North. J. Appl. For., 4:11-16. Zoltai, S.C. and Pollett, F.C., 1983. Wetlands in Canada: their classification, distribution, and use. In: A.J.P. Gore (Editor), Mires: Swamp, Bog, Fen, and Moor, Vol. B, Regional Studies. Elsevier, Amsterdam, pp. 245-268.