Mr. Sabbatini et al., VEGETATION-ENVIRONMENT RELATIONSHIPS IN IRRIGATION CHANNEL SYSTEMS OFSOUTHERN ARGENTINA, Aquatic botany, 60(2), 1998, pp. 119-133
Using a multivariate approach, relationships were determined between f
unctionally defined groups of aquatic plants and the disturbance and s
tress pressures associated with ambient conditions and management regi
me in artificial channel systems of two irrigation districts located i
n the lower valleys of the Rio Colorado and Rio Negro, Argentina. Cano
nical Correspondence Analysis (CCA) of 1993-1994 survey data showed th
at the distribution and abundance of aquatic vegetation was closely re
lated to water conductivity, winter drought, water depth, water moveme
nt and management regime. Indices of disturbance and stress were const
ructed fr om combined environmental data for each site. CCA showed tha
t each variable (disturbance or stress) explained about half of the co
nstrained variation. Four functional plant groups were identified usin
g cluster analyses, occurring in different sets of disturbance and str
ess conditions. Two groups (including Charophyta, Potamogeton pectinat
us and Potamogeton pusillus) were well adapted to disturbance toleranc
e, especially from weed control procedures, bur vulnerable to higher s
aline-stress pressures. Ruppia maritima, Zannichellia palustris and fi
lamentous algae characterised a third group found in shallow, high-sal
inity, permanently filled channels. All plants of the fourth group (Po
tamogeton illinoensis, Elodea callitrichoides, Ceratophyllum demersum,
Myriophyllum aquaticum and the floating Azolla filiculoides) are comp
etitive species, which occurred in channels with low environmental str
ess conditions (low water conductivity and high light availability), b
ut with component species differing in their tolerance of disturbance.
(C) 1998 Elsevier Science B.V.