PARENT SESSION
Oral Session #28: Invasions - Resistance and facilitation.
Presiding: D. Holway
Tuesday, August 6. 8:00 AM to 11:30 AM. Gila Meeting Room, TCC.
Ecosystem engineering by an invasive tree (Acer platanoides) facilitates conspecific invasion.
Reinhart, Kurt*,1, Tirado Fernández, Reyes2, Callaway, Ragan1, 1 University of Montana, Missoula, MT2 Estación Experimental de Zonas Aridas (CSIC), Almería, Spain
ABSTRACT- Ecosystem engineers are organisms that change their surrounding environment and overall community structure. Previous studies suggest that the invasive tree, Acer platanoides alters the structure of invaded forests and facilitates conspecific seedling invasion. We hypothesized that changes in canopy structure and understory light availability following invasion of A. platanoides have a positive feedback on A. platanoides seedlings. We monitored the canopy cover and understory microclimate for native and A. platanoides invaded areas of riparian and upland coniferous forest communities in the northern Rocky Mountains. Invaded areas had increased LAI and decreased light quantity and quality (PAR and R:Fr, respectively). Physiological data were collected for A. platanoides and native seedlings grown in either high light natural riparian areas or low light riparian areas invaded by A. platanoides. Acer platanoides seedlings had lower instantaneous and maximum carbon assimilation rates relative to natives. However, increases in seedling leaf area over time were larger for A. platanoides than similar sized native woody species (i.e., Acer glabrum and Symphoricarpos albus). As A. platanoides seedlings grow, increases in leaf area offset lower photosynthetic rates and result in greater plant-level carbon assimilation rates relative to similar sized natives, especially for plants from low light environments. Overall, our results suggest that A. platanoides is functioning as an ecosystem engineer by altering light microclimate and favoring the establishment of shade tolerant A. platanoides seedlings relative to natives.
KEY WORDS: ecosystem engineer, invasive species, light quantity and quality, facilitation