Date of Award:

5-1-2014

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Advisor/Chair:

Frederick A. Baker

Abstract

Many quaking aspen (Populus tremuloides) stands throughout western North America are considered mature, overmature, or decadent, and lack root suckering to replace the overstory mortality. To mimic natural disturbance and stimulate aspen suckering, prescribed burning or harvesting is needed. It is important to identify pre-disturbance indicators so that land managers will have a way to assess potential sucker production resulting from a prescribed treatment.

In fall 2011, eight field sites were located in the Cedar Mountain study area in southern Utah, and two field sites were located on Deseret Land and Livestock land in northern Utah. At each site, two aspen stands were selected within 50 m of each other, one having a relatively low live aspen basal area and one stand having a relatively high live aspen basal area. Above- and belowground pre-disturbance site characteristics for each paired plot were measured and compared. In spring 2012, all trees within 12.2 m (40 ft) of plot center were felled to stimulate a suckering response from the root system.

Root diameter and root surface area proved to be the best predictors of sucker regeneration density after a disturbance. Sucker densities decrease with increasing root diameters, and most suckers are produced on roots less than 2.5 cm in diameter. The highest sucker densities were recorded on plots which contained abundant roots less than 2.5 cm in diameter. A simple methodology for sampling aspen roots in the field is outlined and is based on the relationship between root diameter, root surface area and sucker production. There was no relationship between total nonstructural carbohydrate (TNC) concentration in the roots (measured as starch and water soluble carbohydrates (WSC), % dry weight) and sucker density, indicating that TNC concentration cannot be used as an indicator of sucker ability of aspen after a disturbance. This study also documents the effect of herbivory on sucker height. In areas where grazing and browsing pressures were great, sucker potential was severely decreased due to the effects of repeated hedging below the browse line or complete sucker elimination. If aspen are to persist on the landscape under these circumstances, management strategies must be implemented to enhance aspen regeneration.

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