Abstract
Landscape patterns of quaking aspen (Populus tremuloides) seedling occurrence and abundance were studied after a rare recruitment event following the 1988 fires in Yellowstone National Park, Wyoming, USA. Belt transects (1 to 17 km in length, 4 m width) along 18 foot trails were surveyed for aspen seedlings on the subalpine plateau of the Park, along gradients of elevation and geologic substrate, during the summer of 1996. Aspen seedling presence and density were characterized as a function of elevation, geologic substrate, slope, aspect, vegetation/cover type, presence of burned forest, and distance to nearest adult aspen stand. Presence of aspen seedlings was best predicted by the incidence of burned forest and proximity to adult aspen; aspen seedlings were only found in burned forest and were more likely to occur closer to adult aspen clones. When tested against independent data collected in 1997, the logistic regression model for aspen seedling presence performed well (overall accuracy = 73%, Taup = 0.41). When present, variation in aspen seedling density at local scales (≤ 200 m) was largely explained by elevation, with higher densities observed at lower elevations. At broad scales (> 1 km), seedling density was a function of cover type, elevation, aspect, slope, and burn severity, with greater seedling density in more severely burned forested habitats on southerly, shallow slopes at lower elevations. Aspen seedling densities ranged from 0 to 46,000 seedlings/ha with a median density of 2,000/ha on sites where they occurred. Aspen seedlings were most abundant in the south central and southwest central regions of the park, approximately an order of magnitude less abundant in the southeast region, and nearly absent in the north central area. Establishment of new aspen stands on Yellowstone's subalpine plateau would represent a substantial change in the landscape. However, the long-term fate of these postfire aspen seedlings is not known.
| Original language | English |
|---|---|
| Pages (from-to) | 127-140 |
| Number of pages | 14 |
| Journal | Landscape Ecology |
| Volume | 18 |
| Issue number | 2 |
| DOIs | |
| State | Published - 2003 |
Funding
We thank our 1996 and 1997 summer field crews (Jeff Cardille, Yvonne Corcoran, Jamie Corcoran, Mark Dixon, Jeffrey Erwin, Jennifer Fraterrigo, Cynthia Gordon, Zac Harlow, Erin Lehmer, Jesse McAfee, David Melkonian, Christopher Mitchell, Josie Plaut, Michael Stevens, Daniel Tinker, and Patrick Whit-more) for their hard work and diligence in hiking miles of trail searching for aspen seedlings. Jeff Car-dille provided valuable advice for testing the predictions of the logistic regression model, Dan Kashian helped with the correlograms, and Tania Schoennagel and Dan Kashian reviewed the manuscript. Three anonymous reviewers and William L. Baker also provided helpful comments. We acknowledge local support from the University of Wyoming-National Park Service Research Center, the Yellowstone Center for Resources, and YNP District Rangers throughout the field seasons. Reed was supported in part by a Guyer Postdoctoral Research Fellowship from the Department of Zoology, University of Wisconsin – Madison. This study was funded by the US Department of Agriculture, National Research Initiative Competitive Grants Program, Forest/Range/Crop/Aquatic Ecosystems Program (Grant No. 95-37101-1689).
Keywords
- Fire ecology
- Landscape ecology
- Logistic regression
- Northern Rocky Mountains
- Population dynamics
- Populus tremuloides
- Spatial extrapolation
- Spatial heterogeneity