Category: Theses and Dissertations
Title: Soil Seed Bank in Southwestern Ponderosa Pine: Implications for Ecological Restoration
Author: * Springer, J.D.
Subject: Ecological Restoration, Ponderosa pine (Pinus ponderosa), Seed bank
Abstract: The objectives of my study were to: 1) obtain a baseline estimate of the plant species in the soil seed bank in a southwestern ponderosa pine forest prior to ecological restoration treatments (such as tree thinning and prescribed burning) ; 2) determine the relationship between soil seed bank species and the aboveground vegetation; and 3) determine species composition and seed density in the forest floor organic matter (0 horizon) versus mineral soil. Results from the baseline study indicate that overstory canopy type has a significant influence on the species in the soil seed bank. In general, annual and biennial species are found in greater numbers in the soil seed bank than perennials. From a total of38 species, the most common species in the soil seed bank were Verbascum thapsus, Leonurus cardiaca, and Conyza canadensis. Six species were non-native and few perennial grasses emerged in seed emergence trials. In an area undergoing ecological restoration, 14 species emerged in seed emergence trials from seed bank samples collected after overstory trees were thinned and prior to prescribed burning, with an estimated seed density of3,152 seeds/mi. The most common species were Collinsia parviflora and Verbascum thapsus, which accounted for 45% and 30% of the germinants, respectively. Fifteen species were observed in the aboveground vegetation at this same site after thinning. Ofthese, Collinsia parviflora was the most common species. Although Verbascum thapsus accounted for 30% ofthe viable seeds in the seed bank, it accounted for only 3% ofthe plants in the aboveground vegetation. There were approximately 101 plants/m' in the thinned area, but only 0.4 plants/m' in the nearby unthinned control. There was a significant correlation between aboveground vegetation and the seed bank in the thinned area, but not in the control. There was a significantly larger number ofseeds in mineral soil than in the 0 horizon. However, a significantly greater number ofnon-native species occupied the 0 horizon versus the mineral soil. There was a significantly greater number ofviable seeds at the 0-5 em depth compared to the 5-10 em depth (including both organic matter and mineral soil).
Publisher: NAU School of Forestry, http://www.for.nau.edu