Co-occurring graminoid and forb species do not differ in their root morphological response to soil heterogeneity

We measured the proliferation of roots into experimental nutrient patches in a grassland community, distinguishing roots of graminoids and forbs. Biomass, length, and specific length were estimated for roots of each of the two functional groups, collected from patches differing in nutrient concentration, and established at four different times during a season. The ratio of graminoid and forb roots was compared with the graminoid-forb ratio in the above-ground biomass. Plant roots proliferated more intensively into patches with higher nutrient concentration, but the roots of the two functional groups had a similar ability to target richer patches. Relative proportion of graminoids was higher below-ground than above-ground and changed during the season, being lowest after mowing. Specific root length was higher for graminoid species, but did not respond to nutrient concentration in patches for either functional group. This is the first study to provide comparative information about root morphological response for graminoids and forbs, measured in a real, semi-natural plant community. The study shows no significant overall difference in the ability of these two functional types to place roots into nutrient-rich patches, but indicates other important differences among the two functional groups.