ABOVEGROUND BIOMASS AND PHOSPHORUS CONCENTRATIONS OF LYTHRUM-SALICARIA (PURPLE LOOSESTRIFE) AND TYPHA SPP (CATTAIL) IN 12 MINNESOTA WETLANDS

We measured standing crop biomass and plant phosphorus concentration o f Lythrum salicaria (purple loosestrife) and Typha spp. (cattails) in 12 Et central Minnesota wetlands. We wanted to determine if significan t changes in plant biomass or phosphorus concentration occur due to di splacement of native vegetation by L. salicaria. Significant changes a ssociated with plant conversion imply potential alteration of importan t wetland functions, including productivity and phosphorus cycling. Ou r results indicate that Typha has significantly greater standing crop biomass (P < 0.01) and that L. salicaria has significantly greater pla nt phosphorus concentration (P < 0.001). However, we found no signific ant difference (P > 0.1) between the two populations in phosphorus con centration per unit area (g P . m(-2)). Our results are inconclusive r egarding potential impacts to whole-wetland phosphorus cycling. Howeve r, we have developed the requisite background descriptive database for experimental work on alteration of wetland functions associated with invasion of Lythrum salicaria.