TITLE:
Soil Depth and Changes in Dry Mass and Competitive Intensity of Two C4 Grasses
AUTHORS:
J. K. Bush, O. W. Van Auken
KEYWORDS:
C4 Grasses; Buffalo Grass; Little Bluestem; Dry Mass; Depth; Competitive Intensity; Semi-Arid Grasslands
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.5 No.1,
January
21,
2014
ABSTRACT:
The presence of grassland biomes and species
cannot be predicted by examining bottom up causes such as precipitation and
temperature. Top down causes including herbivory and fire seem to be major
controlling aspects with other factors secondary. We examined soil depth and
competitive ability of two North American C4 grasses in a greenhouse
experiment. Changes in dry mass were determined and competitive intensity was
calculated for both species. Species were grown separately or together in pots
30, 90, or 180 cm deep. When grown in monoculture, Schizachyrium scoparium total and belowground dry mass increased
from the 30 to 90 cm depth, with no further significant increase from 90 to 180
cm. Aboveground dry mass did not increase significantly with depth. Total dry
mass of Buchloe dactyloides increased
significantly with depth when grown in monoculture. Aboveground dry mass
increased from 30 to 90 cm depth but not from 90 to 180 cm. Belowground dry
mass of B. dactyloides did not
increase significantly with depth. In 180 cm pots, 53% of S. scoparium root dry mass was in the top 30 cm; 74% of B. dactyloides root dry mass was in the
top 30 cm. Roots of B. dactyloides were not found deeper than 90 cm. Aboveground dry mass of S. scoparium was not different in mixture or monoculture at any
depth. Buchloe dactyloides aboveground dry mass in mixture was significantly lower than monoculture at the
30 cm depth, but not at 90 or 180 cm. The greatest
competitive intensity was in the shallow soil pots. Soil depth could partially
explain mosaics found in C4 grasslands where both species were found together with S. scoparium on deeper soils and B. dactyloides on shallower soils.