Response of two perennial grasses to root barriers and fissures

Above- and belowground biomass of contrasting grass growth forms (Hilaria belangeri - shortgrass vs. Bouteloua curtipendula - mid-height grass) was quantified with respect to partial root barriers (at 35 cm soil depth) with artificial fissures. We hypothesized (a) growth would be greatest in the absence of a barrier; and (b) the shallow-rooted H. belangeri would be relatively less affected by barriers with fissures than B. curtipendula. Alternatively (c) B. curtipendula with its deeper root system would exploit fissures and access the resources below barriers better than H. belangeri. The parameters used to evaluate these hypotheses for plants grown in subirrigated 150 cm pots included above- and belowground biomass after 4 months and monthly gravimetric soil moisture at 20 cm intervals to 150 cm. Root barrier treatments had no affect on either species' above-ground growth. As expected, the mid-height grass produced more root biomass and was more deeply rooted. However, partial root barriers had no effect on total root biomass for either species. Although, some 'perching' of root biomass above the barrier occurred in both species, it had no discernable influence on the pattern of soil moisture depletion with depth. Thus, under the conditions of this experiment, the lack of a significant species×barrier interaction suggests the two growth forms were not differentially affected by partial root barriers.