PARENT SESSION
Oral Session #22: Plant function and response to stress. Presiding: K. Miyanishi.
Tuesday, August 7, 2001. 8:00 AM to 11:45 AM. Hall of Ideas P&Q.
The microsite ecology of C4 grasses in boreal Canada.
Kubien, David1, Sage, Rowan1, 1
ABSTRACT- C4 plants often dominate areas with warm, dry climates if they have access to moderate to high light intensities. The lack of C4 success in cool climates is widely recognised, but the mechanisms that underlie this phenomenon are unclear. Further, a few C4 grasses occur at high latitudes, suggesting no inherent disadvantage of C4 photosynthesis in cool climates. In this study, the characteristics of microsites that support Muhlenbergia glomerata in boreal fens were investigated to test the hypothesis that the increased WUE and NUE of C4 plants may compensate for the high latitude climate. Nineteen M. glomerata populations were examined in northern Ontario fens during the summers of 1999 and 2000. The presence of M. glomerata was best predicted by the ground coverage of woody vegetation and the depth of the moss layer. M. glomerata was absent when light levels were below approximately 50% of full sunlight. The C4 species was typically rooted at the interface between the living and dead moss, while the other graminoids (mostly sedges) were rooted below the water table. Because moss hummocks are the highest points above the water table in these fens, they afford the C4 species an opportunity to exploit a WUE advantage. This study indicates that the presence of C4 plants in these cool climates fens could be explained by their greater WUE and NUE enabling them to colonise dry, N-poor microsites such as moss hummocks. However, the drier microsites are frequently inhabited by woody vegetation, which reduce light intensities to levels below those that support extensive C4 success.
KEY WORDS: C4 plants, cool climates