The mechanisms by which various species exert influence disproportionate to their abundance or mass on the structure of a lower intertidal algal community were evaluated experimentally. These functional roles were evaluated experimentally. These functional roles were evaluated by various controlled manipulations at seven stations along the Washington coastline ranked according to an exposure/desiccation gradient. The algae were divided into three categories: canopy species, which grow above the other species and apparently succeed in competitively dominating the light resources as demonstrated by algal blooms following their removal; obligate understory species, which die after the canopy species are removed; and fugitive species, which are quick to colonize new space. Ecological dominance was exerted in areas of moderate wave exposure by Hedophyllum sessile, which competitively displaces a large number of fugitive algal species and which furnishes a protected habitat for many obligate understory algae that die or defoliate after the removal of Hedophyllum. Hedophyllum loses this dominance in the most exposed areas, although such sites apparently represent its physiologically optimal habitat, because in these areas it is out—competed by Laminaria setchellii and Lessoniopsis littoralis. In these wave exposed habitats Lessoniopsis was demonstrated to exert a strong competitive dominance over all the other species in the association. The molluscan herbivores were not observed to express any measurable effects on the recruitment or survival of the algae. However, the echinoid Strongylocentrotus purpuratus often overexploits its prey and has a pronounced influence on most of the algal species. In this respect S. purpuratus enjoys an important community role singular among the many herbivores. Similarly, Pycnopodia helianthoides and Anthopleura xanthogrammica are disproportionately important carnivores, because their predation on Strongylocentrotus, clearing large areas of urchins, results in patches in which algal succession follows. The rate of algal succession following removal of the dominant algal species or of Strongylocentrotus is proportional to the degree of wave exposure. The Hedophyllum canopy recovery at the Eagle Point area of San Juan Island, a site exposed to relatively little wave action and thus high levels of desiccation, was relatively slow, with only 10%—26% cover reestablished after 3 yr. In contrast, Hedophyllum canopy developed up to 66% cover in only 1 yr in the exposed area of Waadah Island; it then quickly lost its dominance to Laminaria and Lessoniopsis. Algal succession in deeper Portage Head tidepools was found to be relatively slow with no clear dominance expressed after 5 yr.

Experimental Evaluation of Ecological Dominance in a Rocky Intertidal Algal Community

____________________________________ Brown, James K.; Smith, Jane Kapler, eds. 2000. Wildland fire in ecosystems: effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-vol. 2. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 257 p. This state-of-knowledge review about the effects of fire on flora and fuels can assist land managers with ecosystem and fire management planning and in their efforts to inform others about the ecological role of fire. Chapter topics include fire regime classification, autecological effects of fire, fire regime characteristics and postfire plant community developments in ecosystems throughout the United States and Canada, global climate change, ecological principles of fire regimes, and practical considerations for managing fire in an ecosytem context.

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Wildland fire in ecosystems: effects of fire on flora

Sprouting in trees, which results in the production of secondary trunks, is an induced response to injury or to a dramatic change in surrounding environmental conditions. This article reviews the forestry and ecology literature to produce an integrated view of the role of sprouting in both disturbed habitats and closed-canopy forests. Sprouting is a universal attribute of temperate angiosperm trees through the sapling stage of development but is much less common among gymnosperms. Four basic types of sprout morphologies are described: collar sprouts from the base of the trunk, sprouts from specialized underground stems (lignotubers and rhizomes), sprouts from roots, and opportunistic sprouts from layered branches. In a survey of 68 species of trees native to northeastern North America, 41% were found to retain the ability to sprout from the collar into adulthood; 26% sprout from branch layers under natural conditions; and 25% have the capacity to form root suckers.

Sprouting in Temperate Trees: A Morphological and Ecological Review

A shelterwood method is described that provides stand conditions that enhance the growth of estabhshed red oak advance reproduction, thereby improving the chances of maintaining an oak component in the next stand. Stocking of a mature, fully stocked stand is reduced to 60%, 65%, and 70% of initial stand basal area where oak site index is 70, 80, and 90 ft, respectively. The basal area reduction is accomplished from below using herbicides, leaving the main canopy essentially intact. This level and method of treatment prevents yellow-poplar, a primary competitor of red oak, from becoming established and growing prior to the final removal cut, and it eliiinates most sprout competition from shade-tolerant subcanopy species after the final removal cut. The final removal cut can be made approximately 10 years after the initial treatment. FOR. SCI. 36(4):917-929. ADDITIONAL KEY WORDS. Regeneration, prescribed fire.

A Shelterwood Method for Regenerating Red Oak in the Southern Appalachians

1. Ecological Research in the Tropics.- Physiological Ecology.- 2. Physioecological Problems in the Tropics.- Dynamics of Populations.- 3. Demographic Strategies in Animal Populations: A Regression Analysis.- 4. A Matrix Model of Tree Population Dynamics.- 5. An Analysis of Late Secondary Succession in Species-Rich Tropical Forest.- 6. The Relation Between Rainfall and Mosquito Populations.- Interaction Between Species.- 7. Impact of Sloths on Neotropical Forest Energy Flow and Nutrient Cycling.- 8. Impact of Leaf-Cutting Ants on Vegetation Development at Barro Colorado Island.- Tropical Forest Analysis.- 9. Biomass and Structure in a Central Amazonian Rain Forest.- 10. Root Distribution and Biomass in Three Ivory Coast Rain Forest Plots.- 11. Litter Production in Deciduous Forest near Udaipur (South Rajasthan), India.- 12. Litter Fall and Litter Breakdown in Miombo.- 13. Nutrients in Throughfall and Their Quantitative Importance in Rain Forest Mineral Cycles.- 14. Production, Energy Pathways, and Community Diversity in Forest Birds.- Savannas.- 15. The Structure and Function of a Tropical Savannah Ecosystem.- 16. A Critical Consideration of the Environmental Conditions Associated with the Occurrence of Savanna Ecosystems in Tropical America.- 17. Effect of Fire on Organic Matter Production and Water Balance in a Tropical Savanna.- 18. Net Primary Production in Grasslands at Udaipur, India.- Tropical Water Bodies.- 19. Tropical Rivers as Expressions of Their Terrestrial Environments.- 20. Productivity, Biomass, and Population Dynamics in Amazonian Water Bodies.- 21. Some Aspects of the Ecology of Tropical Estuaries.- 22. Diurnal Rates of Photosynthesis, Respiration, and Transpiration in Mangrove Forests of South Florida.- Island Ecosystems.- 23. Some Aspects of Island Ecosystem Analysis.- Applications.- 24. Faunal Equilibria and the Design of Wildlife Preserves.- 25. A Comparison of Soils Under Agriculture and Forests in San Carlos, Costa Rica.

Tropical Ecological Systems; Trends in Terrestrial and Aquatic Research.

Four plant communities–northern hardwoods, oak woods, goldenrod (Solidago sp.)—poverty grass (Danthonia spicata) fields, and little bluestem (Andropogon scoparius) fields–were studied in seventeen areas on west to southeast slopes which had been burned by wildfires in 1962, 1963, or 1964. Stability of oak woods after fire was greater than that of northern hardwoods as shown by the lower percentage of dead and dying trees (16% vs. 35%), higher percentage of saplings sprouting (87% vs. 43%), higher average number of sprouts per sapling 4.4 vs. 2.5), and higher percentage of ground—layer species remaining unchanged or increasing in frequency (87% vs. 67%). In goldenrod—poverty grass fields, fire caused goldenrods to increase and poverty grass to decrease. Average weight of dicots was 24% more and that of monocots was 50% less in burns than in unburned portions. These fields appeared to revert to poverty grass dominance after several years without fire. In little bluestem fields, red top (Agrostis alba) and l...

Frederick R. Swan

Papers

Post-fire response of four plant communities in south-central New York State.