Cg. Wan et al., SOIL-WATER EXTRACTION AND PHOTOSYNTHESIS IN GUTIERREZIA-SAROTHRAE ANDSPOROBOLUS-CRYPTANDRUS, Journal of range management, 46(5), 1993, pp. 425-430
Broom snakeweed (Gutierrezia sarothrae Shinners), a C3 evergreen half-
shrub, is a formidable competitor of grasses in the semiarid southwest
ern rangelands. Sand dropseed (Sporobolus cryptandrus (Torr.) Gray), p
erennial C4 bunchgrass, is the most drought resistant species in the s
hort-grass prairie. A comparative study on soil water extraction patte
rns, photosynthesis, and canopy development in both species during spr
ing-summer growing season of 1991 was conducted in pot- and field-grow
n plants. Sand dropseed extracts water at depths between 0 and 30 cm m
ore effectively than broom snakeweed. In contrast, broom snakeweed can
take up more water from the subsoil (30-60 cm) than sand dropseed. Ph
otosynthesis in sand dropseed was more affected by soil water deficit
than was broom snakeweed, which was related to their water extraction
patterns. Leaf area accumulation of broom snakeweed was not affected b
y spring drought, but that of sand dropseed was reduced. Because of gr
eater water extraction from the wetter subsoil by broom snakeweed duri
ng drought, it can assimilate more carbon and, therefore, prevail in a
competitive relationship with sand dropseed.