PARENT SESSION
Oral Session #80: Plant Ecology .
Presiding: G. Platenkamp
Thursday, August 8. 9:00 AM to 11:30 AM. Grand Ballroom West, Radisson.

Spatial pattern of shrubs and grasses in a tropical alpine puna.

Kleier, Catherine^*,1, Lambrinos, John, ¹ Adams State College, Alamosa, CO

ABSTRACT- We estimated percent cover and nurse plant associations in Parque Nacional Lauca, Parinacota, Chile (18° 12' S, 69° 16' W). Vegetation cover in this high altitude (4300 masl) arid puna ecosystem was approximately 41%, with the remaining 59% being bare sand or cobble. Dominant species were, Parastrephia lucida (Meyen) Cabr. [Asteraceae] and Festuca orthophylla Pilger. [Poaceae]. To determine if F. orthophylla was acting as a nurse plant for P. lucida, we investigated associations in four 25 by 25 m plots. Densities of F. orthophylla averaged 0.482 plants m^-2 and densities of P. lucida averaged 0.156 plants m^-2. We used Chi-squared to test for nurse plant effects. Expected numbers were calculated by multiplying the percentage of coverage of bare ground or vegetation times the total number of plants of a given species within the plot. Out of 390 P. lucida individuals, none formed intraspecies associations. Parastrephia lucida did form associations with F. orthophylla (mean X² = 73.1 + 21.12, p <0.001). However F. orthophylla was found growing on bare ground more often than expected (mean X² = 85.44 + 63.68, p <0.001). These results indicate that F. orthophylla roots more often on bare ground and that P. lucida grows more often in association with F. orthophylla than would be expected.