UC Davis Department of Plant Sciences

Aspen Stands - restoring and managing

Project 3: The Contribution of Aspen Stands to Plant Diversity in the Sierra Nevada and Cascades 

Keywords – biodiversity, California, conifer, meadow, modified-Whittaker, montane vegetation, Sierra Nevada, Cascade, Populus tremuloides
Participants
– Tim Kuhn, Bobette Jones, Natalie Stoddard, Shannon Cler, US Forest Service

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Restoration of quaking aspen stands (Populus tremuloides Michx.) impacted by conifer encroachment and excessive livestock browse has become a management priority in many of California’s National Forests and Parks. It is commonly presumed that restoration of aspen stands will enhance plant species richness and diversity at the stand level, and thus increase overall diversity upon the landscape. Our objective was to determine if functioning aspen stands contribute unique plant species and assemblages not found in adjacent conifer and meadow communities (view supporting research>>).


Aspen stands and meadows represent a minor, but diverse, component of the coniferous forest dominated landscape of the Sierra Nevada and Cascade ranges.

We used a modified-Whittaker plot survey protocol to measure plant species richness, diversity and plant assemblage composition in 30 sets of adjacent aspen, conifer, and meadow communities at multiple spatial scales (1, 100, and 1000 m2). Surveys were conducted during the summer of 2005 and 2006 in the northeastern Sierra Nevada and southeastern Cascade Region of California on the Lassen, Plumas, Tahoe, and Humboldt-Toiyabe National Forests, as well as the Lake Tahoe Basin Management Unit. Similarity indices and plant species lists were used to compare compositional overlap among the three vegetation types.

 

 

aspen stands

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We surveyed 30 aspen-meadow-conifer forest associations from the central Sierra Nevada to the southern Cascades.

Aspen stands in supported 63 unique plant species not observed in adjacent conifer forests and meadows. Aspen exhibited only 14 and 25% similarity (Jaccard’s Index) with conifer forests and meadows, respectively. Plant species richness, diversity, evenness, and dominance in aspen stands were only marginally different from meadows, but were significantly different from conifer forests. Within aspen plant communities, we found a significant negative relationship between aspen canopy cover and species diversity.

 

 

 

 

aspen diversity

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aspen diversity

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Aspen had similar diversity and richness values as meadows, but supported 63 unique species not found in either meadows or conifer forests.

Management Implications
Intact aspen stands support a distinct and unique vegetation type in northeastern California. Pronounced differences between aspen and conifer stands. Conservation and restoration of declining aspen stands in the region is important to maintain both site and landscape level diversity and richness.


 

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