The efficacy and ecological impacts of herbicide and cutting regimes on the submerged plant communities of four British rivers. II. A multivariate analysis of the effects of management regimes on macrophyte communities.
Macrophyte abundance scores derived from percentage frequencies from permanent transects in four rivers were subjected to DECORANA and TWINSPAN multivariate analyses. The resulting ordination and classification sorted the samples very clearly by site and by sampling time. No pattern distinguishing the effects of cutting and chemical herbicides was observed, indicating that any alteration in the plant communities caused by management resulted in less variation than already existed between sites. The ordination suggested that several water chemistry parameters, e.g. calcium and nitrate concn, might be influencing the plant communities at each site. The value of the multivariate approach for short and longer-term management studies on river vegetation is discussed.