EFFECTS OF SALINITY ON GROWTH AND EVAPOTRANSPIRATION OF TYPHA-DOMINGENSIS PERS

The interactions between salinity, growth and evapotranspiration (E(t) ) were investigated for Typha domingensis Pers. in a greenhouse growth experiment and in Cienega de Santa Clara, a coastal desert marsh in t he Colorado River delta in Mexico. Although Typha is often found in br ackish as well as fresh water marshes, salinity imposed severe constra ints to its growth and distribution. In the 68 day greenhouse experime nt, growth was maximal at 1.1 ppt. (control solution), half-maximal at 3.5 ppt. and negligible above 6 ppt.; 75% mortality occurred at 15 pp t. E(t) decreased with salinity in proportion to growth reduction. In the Cienega, T. domingensis was only found in water of 5-8 ppt. or les s. When inflow water was 1.0 ppt., Typha E(t) was estimated to be 1.3 times pan evaporation (E(o)), whereas when inflow water was 3.2 ppt,, estimated E(t)/E(o) was only 0.7. An estimated half of the inflow wate r to the Cienega exited the vegetated portion of the Cienega unused, o wing to the salt tolerance limit of Typha. A practical objective of th e study was to predict the effect of brine placement from the Yuma Des alting Plant into the Cienega; it was concluded that the resulting inf low salinity of 7-10 ppt. would result in deterioration of the Typha s tands owing to excess salinity.