Document Type

Article

Publication Date

2006

Publication Title

Journal of Torrey Botanical Society

Volume

135

Issue

1

First page number:

26

Last page number:

36

Abstract

ABELLA, S. R. (Public Lands Institute and School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, NV 89154-2040) AND J. D. SPRINGER (Ecological Restoration Institute, Northern Arizona University, Flagstaff, AZ 86011-5017). Canopy-tree influences along a soil parent material gradient in Pinus ponderosa- Quercus gambelii forests, northern Arizona. J. Torrey Bot. Soc. 135: 26–36. 2008.—The distribution of canopy trees can impose within-site patterns of soil properties and understory plant composition. At ten sites spanning a soil parent material gradient in northern Arizona Pinus ponderosa-Quercus gambelii forests, we compared soils and plant composition among five canopy types: openings, Pinus ponderosa single trees, Quercus gambelii single stems, dispersed clumps, and thickets. Soil texture on average did not differ significantly among canopy types, whereas Oi horizon thickness and weight, 0–15 cm soil loss-on-ignition, and gravimetric soil moisture differed significantly among three or more canopy types. Understory plant richness per 4 m2 ranged from five species below P. ponderosa to 12 species in openings, with richness below Q. gambelii single stems significantly greater than below Q. gambelii thickets. C4 graminoids (e.g., Aristida purpurea) inhabited openings, while C3 species like Poa fendleriana also occurred below trees. The forbs Thalictrum fendleri and Lathyrus laetivirens were strongly associated with Q. gambelii dispersed clumps and thickets. We also conducted an experimental planting with T. fendleri that was consistent with these correlational results, with outplanted T. fendleri seedling survival 2–7 times greater when planted below Q. gambelii compared to openings. Previous research and our results suggest that understory species associated with Q. gambelii canopies vary regionally, but there are consistently some associated species. Canopy types affected understory vegetation similarly across soil parent materials, not supporting a hypothesis that positive plant interactions changed along soil gradients. Our results suggest that forest management that manipulates both the density and the pattern of trees, together with the growth forms of Q. gambelii trees, can induce within-site spatial patterns of soil properties and understory species.

Keywords

Forest canopies; Forest ecology; Forest soils; Lathyrus laetivirens; Pedicularis centranthera; Ponderosa pine; Positive plant interactions; Quercus gambelii; Single-tree influences; Thalictrum fendleri; Understory; Understory plants

Disciplines

Botany | Forest Sciences | Plant Sciences | Soil Science

Language

English

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