Effect of isolation on the composition of soil seed banks on the Atherton Tableland, northeast Queensland, Australia

Pullo, Andrea L. (2005) Effect of isolation on the composition of soil seed banks on the Atherton Tableland, northeast Queensland, Australia. Masters (Research) thesis, James Cook University.

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Tropical rainforest rehabilitation is one method to recreate, establish, and accelerate natural successional processes. Tropical rehabilitation has occurred on the Atherton Tableland for 15 years. Currently, rehabilitated sites on the Atherton Tableland are monitored by tree planting agencies for two to three years to reduce exotic species. The 10-12 years following the last monitoring period provides the opportunity to investigate successional processes of these rehabilitated sites.

One method to investigate rehabilitation management is through the soil seed bank. The composition and recruitment pattern of seeds in the soil seed bank may offer information on species that have the potential to germinate in rehabilitated sites following a disturbance. This knowledge is useful to predict future successional patterns within rehabilitated sites.

This study investigated the soil seed bank composition of rehabilitated sites adjacent to – and isolated from – remnant rainforest. In addition, it was determined whether distance from seed source influenced exotic species composition and native species recruitment that occurred to rehabilitated sites. Seventeen rainforest study sites were chosen for investigation: six remnant rainforest sites, six rehabilitated sites adjacent to remnant rainforest, and five rehabilitated sites isolated from remnant rainforest. Twenty soil samples were collected (60 x 60 x 50 mm deep) for each site, and overstorey plant species were recorded. Germination of soil-stored seeds occurred for three months, and seedling identification occurred on a weekly to fortnightly basis. Following species identification, life history traits were collected including: origin (native or exotic), life form, dispersal mechanism, seed size, successional stage, and whether species were recruited to the rehabilitated sites.

Non-parametric tests, Kruskal-Wallis ANOVA and Mann-Whitney U-tests were used to determine whether differences occurred between sites in number of seeds, number of species, or life history traits. Spearman's Rank Correlation Coefficient identified positive and negative associations among life history traits.

A total of 10,938 seeds germinated from the 17 study sites, and 10,226 were exotic. Exotics represented 328 germinants and 40 species of remnant rainforest sites; 4,864 germinants and 34 species of adjacent rehabilitated sites; and 5,034 germinants and 31 species of isolated rehabilitated sites. There were no significant differences in number of exotic seeds and species between the adjacent and isolated rehabilitated sites, which indicate that distance from seed source did not affect the exotic composition of rehabilitated sites. The exotic species found in the soil seed banks were herbs and grasses. Herbs and grasses had a significant positive correlation with wind dispersal, small sized seeds, and early successional species.

A total of 238 seeds were native recruits. Native recruits represented 120 germinants and 20 species of remnant rainforest sites, 33 germinants and 5 species of adjacent rehabilitated sites, and 85 germinants and 4 species of isolated rehabilitated sites. There were no significant differences in native recruit germinants among the remnant rainforest sites, the adjacent rehabilitated sites and the isolated rehabilitated sites; however, there were significant differences in the number of native species recruited between the three rainforest site types. There were significantly more species recruited to the remnant rainforest sites than the adjacent rehabilitated sites. However, the results indicate that location of rehabilitation planting (adjacent or isolated) does not affect native species recruitment. The native recruited species were shrubs and trees. There was a significant positive association between life form and wind dispersal, small sized seeds, and early successional stage.

The soil seed bank composition suggests that 10 – 12 years following weed control, exotic species may germinate after a disturbance and establish the rehabilitated sites. These results have significant implications for future rehabilitation efforts on the Atherton Tableland due to evidence of exotic herbaceous dominance, which requires longer and more intense management.

Item ID: 1320
Item Type: Thesis (Masters (Research))
Keywords: Atherton Tablelands; composition and recruitment pattern; dispersal mechanism; distance from seed source; early successional species; exotic herbaceous dominance; exotic herbs and grasses; life form; life history traits; native shrubs and trees; North Queensland; Northern Australia; Nth Qld; recruitment; seed size; small sized seeds; soil seed bank; successional stage; tropical rainforest rehabilitation; wind dispersal
Date Deposited: 05 Jan 2007
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management @ 33%
05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050202 Conservation and Biodiversity @ 33%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060208 Terrestrial Ecology @ 34%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960505 Ecosystem Assessment and Management of Forest and Woodlands Environments @ 33%
96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960806 Forest and Woodlands Flora, Fauna and Biodiversity @ 33%
96 ENVIRONMENT > 9604 Control of Pests, Diseases and Exotic Species > 960414 Control of Plant Pests, Diseases and Exotic Species in Forest and Woodlands Environments @ 34%
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