Plant species diversity on logged versus burned sites in central Alaska

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Abstract

Natural fires and logging are two of the main disturbances affecting upland boreal forest in Alaska. The objectives of this study were to determine whether logged sites differ from burned sites in (1) overall plant species richness, (2) successional trajectories, and (3) species diversity at particular stand structural development stages. We compared plant species diversity on sites burned in natural fires to sites that were logged and not subsequently burned in central Alaska. We sampled 12 logged and 12 burned former upland white spruce (Picea glauca (Moench) Voss) forests in four stand development stages representing stand initiation (stage A), early stem exclusion (stage B), understory reinitiation (stage C), and mature hardwood (stage D) stages. In this study the dates of disturbance varied from 1990 to 1994 in stage A, 1978 to 1983 in stage B, 1957 to 1965 in stage C, and 1900 to 1920 in stage D plots. All sites were similar in slope, aspect, and soil type. Vascular plants were identified to the species level (except for certain willows) and bryophytes and lichens were identified to the level of presumptive (usually unknown) species within family groups. Organic layer thickness was significantly greater on logged sites compared to burned sites overall and at each stage. Burned sites (all stages combined) supported more species (146) than logged sites (111), and more species at each stand development stage. Burned plots in stages A and B supported abundant cover of a few apparent fire specialist species (Ceratodon purpureus (Hedw.) Brid., Marchantia polymorpha L. and Leptobryum pyriforme (Hedw.) Wils.) that were present in only minor amounts on logged sites. Burned plots exhibited higher species turnover from stage to stage and among all stages than logged plots. Species dominant in burned stage A plots were nearly absent in burned stage C and D plots, while logged stage A dominants, which were common mature forest species, increased in each subsequent stage. We compared floristic similarity between our disturbance plots and mature upland white spruce stands in Bonanza Creek Long-Term Ecological Research (LTER) site. Only five species found in the LTER dataset were not also present in this study, which suggests that nearly all species compositional change in our study area occurs during the first century after disturbance. Logged sites appear to begin and continue succession with a greater share of the original mature forest understory plants, while burned sites initiate succession with more distinctive and specialized plant species.

Introduction

Fire and logging are two major disturbances in upland boreal forests of North America (Johnson, 1992), including Alaska (Viereck and Schandelmeier, 1980). Fire has long played a crucial role in the ecology of the North American boreal ecosystem, and many species of plants have evolved to depend upon this disturbance for their survival (Shafi and Yarranton, 1973). Localized logging started in interior Alaska about 1900, occurred at low levels during the middle of the 20th century, and has increased since the 1970s (Wurtz and Gasbarro, 1996).

The goal of forest policies in many boreal regions is to simultaneously develop sustainable productivity and maintain biodiversity within the framework of tested and reliable resource management techniques (Lamas and Fries, 1995, Riley, 1995). This new emphasis reflects concerns for biodiversity as logging has become widespread and natural fire has been greatly diminished or eliminated in parts of the boreal world.

In Sweden, 286 species, including vertebrates, invertebrates, vascular plants, bryophytes, lichens, and fungi, are threatened due to land use changes in forestry, especially increased logging and fire suppression (Nilsson and Ericson, 1992). Logging on short rotations has reduced many of the structural components, spatial patterns, and processes affecting plant species diversity in the post-fire disturbed Fennoscandian boreal forest (Esseen et al., 1992). The near elimination of fire in the Scandinavian landscape has made post-fire succession stands, burnt substrates, and coarse woody debris rare.

The objectives of this study were to determine whether logged versus burned sites across a range of times since disturbance in central Alaska differ in (1) overall plant species richness, (2) successional trajectories, and (3) species diversity at particular stand development stages.

Section snippets

Study area and sample site selection

All plots were located between 65°50′ and 63°20′N latitude and 142°30′ and 150°00′W longitude in the Tanana and Yukon River drainages of central Alaska. Sampling was restricted to typical commercial forest sites, which are generally south-facing slopes with inceptisols formed in deep permafrost-free loess deposits, generally overlying Precambrian schist. In this region moderately sloping southerly aspects primarily support mixed stands of aspen (Populus tremuloides Michx.), paper birch (Betula

Organic layer and canopy cover

Organic layer depth was consistently greater at each stage on logged plots compared to burned plots and overall (Fig. 2). Organic depth of was significantly different between disturbances (P>0.000, 1 d.f., F=47.6) and within each disturbance (P>0.001, 3 d.f., F=11.0). The interaction of within-disturbance versus between-disturbance effects on organic layer depth was not significant (P>0.48, 3 d.f., F=0.86). Overall canopy cover across all stages was not significantly different between disturbance

Discussion

One of the most significant findings of this study is the clear and consistent difference in organic layer depths at all stages between the two disturbance types. In central Alaska deep organic layers are poor seedbeds (large number of seeds required to produce each germinant) for a variety of species including the dominant forest trees (Zasada et al., 1992). Complete removal of the organic layer through fire eliminates vegetative reproductive structures and creates a site requiring plant

Implications for management

We have established that organic layer depth is consistently greater on logged sites in central Alaska than on burned sites. Because greater organic depth is associated with cooler soil temperatures, reduced nutrient availability, and lowered site productivity (Van Cleve and Viereck, 1981, Van Cleve and Yarie, 1986, Curran and Ballard, 1990), we recommend that managers consider broadcast burning of at least some logged sites. The benefits we expect from this treatment would include greater

Acknowledgements

Funding for this project was provided by the Natural Resource Fund of the University of Alaska, National Science Foundation Grant DEB #9211769 in support of the Bonanza Creek Long-Term Ecological Research site, and the McIntire-Stennis Cooperative Forestry Research Program. Access and location assistance were provided by the Alaska Department of Natural Resources, Division of Forestry. The USDI BLM Alaska Fire Service provided fire records. Joy Jenkins and Robert Solomon assisted in the

References (38)

  • K.P. Timoney et al.

    Vegetation development of boreal riparian plant communities after flooding, fire, and logging, Peace River, Canada

    For. Ecol. Manage.

    (1997)
  • Argus, G., Boas, F., Coupe, R., DeLong, C., Douglas, G., Goward, T., MacKinnon, A., Pojar, J., Pojar, R., Roberts, A.,...
  • F.A. Bazzaz

    Plant species diversity in old-growth successional ecosystems in southern Illinois

    Ecology

    (1975)
  • A. Berg et al.

    Threatened plant, animal, and fungus species in Swedish forests: distribution and habitat associations

    Conserv. Biol.

    (1994)
  • J.R.T. Busby et al.

    Microclimate control of growth rates and habitats of the boreal forest mosses, Tomenthypnum nitens and Hylocomium splendens

    Ecol. Monogr.

    (1978)
  • T.J. Carleton et al.

    Vegetation of the boreal forests south of James Bay: non-centered component analysis of the vascular flora

    Ecology

    (1980)
  • Crimp, P.M., Phillips, S.J., Worum, G.T., 1997. Timber resources on state forestry lands in the Tanana Valley. Division...
  • Curran, M.P., Ballard, T.M., 1990. Some slash burning effects on soil and trees in British Columbia. In: Gessel, S.P.,...
  • J.T. Curtis et al.

    The inter-relations of certain analytic and synthetic phytosociological characters

    Ecology

    (1950)
  • C.T. Dyrness

    Early stages of plant succession following logging and burning in the western Cascades of Oregon

    Ecology

    (1973)
  • Esseen, P.A., Ehnstrom, B., Ericson, L., Sjoberg, K., 1992. Boreal forests—the focal habitats of Fennoscandia. In:...
  • Fisher, N.I., 1993. Statistical Analysis of Circular Data. Cambridge University Press, Cambridge, UK, 277...
  • J.F. Franklin et al.

    Creating landscape patterns by forest cutting: ecological consequences and principles

    Landsc. Ecol.

    (1987)
  • Haugset, T., Alfredsen, G., Lie, M.H., 1996. Nøkkelbiotoper og artsmangfold i skog. Naturvernforbundet i Oslo og...
  • Hultén, E., 1968. Flora of Alaska and Neighboring Territories. Stanford University Press, Stanford, CA, 1008...
  • Johnson, E.A., 1992. Fire and Vegetation Dynamics: Studies from the North American Boreal Forest. Cambridge University...
  • G.H. La Roi et al.

    Ecological studies in the boreal spruce–fir forests of the North American taiga. II. Analysis of the bryophyte flora

    Can. J. Bot.

    (1976)
  • T. Lamas et al.

    Emergence of a biodiversity concept in Swedish forest policy

    Water Air Soil Pollut.

    (1995)
  • Magurran, A.E., 1988. Ecological Diversity and its Measurement. Princeton University Press, Princeton, NJ, 179...
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    Present address: Directorate of Public Works, ATTN: APVR-WPW-EV, 1060 Gaffney Road #6500, Fort Wainwright, AK 99703-6500, USA. Tel.: +1-907-353-9318; fax: +1-907-353-9867.

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