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Journal article
Early primary succession on Mount St. Helens: impact of insect herbivores on colonizing lupines
Ecology, Vol.83, pp.191-202
2002
Handle:
https://hdl.handle.net/2376/5808
Abstract
Lupinus lepidus var. lobbii, the earliest plant colonist of primary successional habitats at Mount St. Helens, can dramatically influence successional rates and ecosystem development through N fixation and other facilitative effects. However, 15 yr after the eruption, lupine effects remained localized because high rates of population growth in newly founded patches ([lambda] = 11.2, 1981-1985) were short lived ([lambda] = 1.51, 1991-1995), despite widespread habitat availability. To investigate this paradox, I examined 60 colonizing lupine patches, ranging from low-density patches at the edge of the expanding lupine population, to high-density patches in the population core, including 41 patches created in 1992. Survival, reproduction, and herbivory (for a subset of plants and years) were measured on ~12 000 plants for up to 5 yr (1991-1995). Stem-boring, leaf-mining, and seed-eating lepidopterans and anthomyiid flies, feeding in edge patches and in low-density margins of core patches, strongly affected edge patch demography, but not that of central core areas. For example, in 1994-1995, 77% of edge plants were afflicted by tortricid stem borers vs. 24% in the core, and from 1993-1995 gelechiid leafminers infested 68% of plants in the youngest edge patches, vs. only 8% at the core. Associated adult mortality was 88%, compared to ~30% when absent. Seed predators consumed 36% (range 4-92%, 1991-1995) of seeds in both core and edge patches, with seed loss negatively correlated with seedling number the following year. In contrast to edge patches, resource-dependent seedling mortality appears to govern short-term dynamics in high-density core areas. In conclusion, edge region herbivore effects can account for the observed 7.5-fold difference in [lambda] between patches founded 10 yr apart. Locally, increased lupine mortality creates access to high-quality sites, facilitating succession, but at larger spatial scales diminished population growth is likely to retard facilitation and succession.
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Details
- Title
- Early primary succession on Mount St. Helens: impact of insect herbivores on colonizing lupines
- Creators
- John G. Bishop (Author)
- Publication Details
- Ecology, Vol.83, pp.191-202
- Academic Unit
- Biological Sciences, School of
- Identifiers
- 99900502635701842
- Copyright
- In copyright ; openAccess ; http://rightsstatements.org/vocab/InC/1.0/ ; http://purl.org/eprint/accessRights/OpenAccess
- Language
- English
- Resource Type
- Journal article