PARENT SESSION
Contributed Oral Session 124: Grassland Ecology: Water Relations; Growth
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 518 C, Level 5, Palais des congrès de Montréal
Coupling seasonal patterns of root and shoot production in grasses, shrubs and trees.
Steinaker, Diego*,1, 2, Wilson, Scott1, 1 University of Regina., Regina, SK, Canada2 INTA, San Luis, Argentina
ABSTRACT- Primary production is a key ecosystem attribute that responds to climate. Most of our knowledge about production is based on net annual aboveground data, in spite of the majority of production being belowground in temperate and arid systems. We examined seasonality in production for both roots and shoots and its relationship with microclimate (soil temperature and moisture). We used sequential images of roots (via minirhizotrons) and shoots from 8-year-old monocultures of grasses and woody plants (10 species, 5 replicates) at the northern edge of the Great Plains. We found surprisingly few differences between grasses and woody species in the timing of production, but both root and shoot growing seasons were significantly longer in C3 than C4 grass species. Seasonal trade offs between above- and below-ground production were found. Increased root production, for instance, occurred during periods of decreased shoot production. The growing season for root production was 30% longer than that for shoot production, primarily because roots continued to grow during the warmest and driest part of late summer. In addition, fine root production was greater in dry grass plots than in plots with more moisture. These results suggest that grasses and woody plants respond to seasonal and local spatial water stress by increasing fine root production and absorption area. Thus, global warming may increase root: shoot ratios in both grassland and forest.
Key words: seasonality, production, roots, grasses