THE EFFECT OF COMPETITION AND SALINITY ON SHOOT GROWTH AND REPRODUCTIVE BIOMASS OF ECHINOCHLOA-CRUS-GALLI

The effect of interspecific and intraspecific competition and salinity on the growth and distribution of Echinochloa crus-galli (L.) Beauv. was investigated in the field and under laboratory conditions. A de Wi t replacement series indicated that the total dry mass of Echinochloa crus-galli decreased significantly with an increase in the density of Atriplex triangularis Willd. Under laboratory conditions, salinity had a greater inhibitory effect on the above-ground biomass production of E. crus-galli than did an increase in the proportion of the competito r, A. triangularis. Increasing salinity levels caused a decrease in th e total above-ground biomass production of E. crus-galli and probably limited its distribution in the more stressful habitats. Laboratory ex periments indicated that within the salinity range tested, Echinochloa could compete successfully with the more salt tolerant Atriplex. In t he field, we found that the distribution of E. crus-galli along a sali nity gradient was limited by salinity stress at high salinities and by competition from A. triangularis at low salinities.