Comparison between root and stem total nonstructural carbohydrate concentrations in three woody plant species
Davidson, Jennifer Lynn
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Concentrations of total nonstructural carbohydrates (TNC) are often used as an indicator of plant physiological status. Repeated depletion of TNC following heavy browsing may result in plant death, potentially changing the plant community structure in an area. Total nonstructural carbohydrate sampling in woody plants typically occurs immediately below the basal crown. However, sensitive areas containing cultural resources or fragile soils may require protection from soil disturbance, limiting the ability to sample root material. Sampling aboveground tissues would reduce soil disturbance in sensitive areas and may provide multiple sampling opportunities from a single plant. The hypothesis of this study is that root and stem TNC concentrations are positively correlated throughout the year. Root and stem samples were collected from three species, mountain mahogany (Cercocarpus montanus), Gambel oak (Quercus gambelii), and aspen (Populus tremuloides) from Bandelier National Monument, New Mexico. Samples were collected at 4-week intervals from May 1999 through June 2000. Total nonstructural carbohydrate concentrations were determined using an anthrone reagent procedure. Relationships between root and stem concentrations were analyzed using a Student's paired t-test (a=0.05). Sampling dates when concentrations were different between plant parts varied from species to species. There appeared to be no pattern to the variation in the differences in any of the species. Correlation between root and stem TNC concentrations of each species were determined with simple linear regression. There were no strong relationships within a single month for any species. However, monthly means for root and stem TNC concentrations were closely related across the entire sampling period for each species. The correlation between root and stem TNC in mountain mahogany had an r^2 = 0.8661. The Gamble oak root and stem TNC correlation had an r^2= 0.8863. Aspen had a root and stem correlation of r^2 = 0.7711. Although differences between root and stem TNC concentrations varied throughout the year, root TNC concentrations in mountain mahogany, Gambel oak, and aspen may be predicted from stem TNC concentrations with reasonable precision.