PARENT SESSION
Oral Session #66: Invasions: Plants. Mechanisms, patterns, controls. Presiding: R. Mack.
Thursday, August 9, 2001. 1:00 PM to 4:45 PM. Hall of Ideas E.

Factors influencing Juniperus ashei seedling growth.

McKinley, Duncan¹, Van Auken, Oscar¹, ¹

ABSTRACT- Density of Juniperus ashei has increased in many grasslands by encroachment. Formerly, Juniperus ashei was apparently restricted to canyons, ridges and areas with shallow soils. Juniperus ashei seedlings under adult Juniperus ashei canopies have either limited or no growth until the adult Juniperus ashei trees are removed, in which case seedlings below the former canopy may grow at an accelerated rate, replacing the former parent tree. The replacement dynamics of Juniperus ashei is not understood. A factorial field experiment was set up on the southern Edwards Plateau of central Texas to investigate the possible cause or causes for seedling growth suppression below the canopy. Intraspecifc competition on Juniperus ashei seedlings from the adult trees mainly consists of light, water and nutrient availability. These variables were manipulated by canopy alterations with additions of water, nutrients and artificial shade. Data collected for this experiment was analyzed using ANOVA. Results varied slightly between the response variables, which include basal diameter, height and number of branches. Shading from the adult tree or artificial shade consistently reduced the growth of the seedlings when compared to seedlings that were exposed to higher light levels. Evidence from preliminary findings indicate that it is likely that low levels of shade coupled with the removal or reduction of the competition from the adult Juniperus ashei tree, will lead to the successful growth of Juniperus ashei seedlings.

KEY WORDS: Juniperus ashei, Juniper