科研之友
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摘要
The dynamic of plant communities is strongly influenced by biologicalinteractions. We studied the effects of Eichhornia azurea on the growth of the free-floating macrophytes Eichhornia crassipes, Salvinia minima, Salvinia auriculata and Limnobium laevigatum. The experiments were carried out in three lakes of the upper Paran芍 river floodplain. We used 0.5 m side squares where these species grew for 11 days (S. auriculata and L. laevigatum) and 17 days (E. crassipes and S. minima), in the presence and absence of E. azurea. There were no significant differences between the relative growth rates of macrophytes growing in the absence and presence of E. azurea. The relative interaction index showed the existence of competition between E. azurea and L. laevigatum, and neutrality with the other three species. There was no evidence of facilitation related to the improvement of physicochemistry characteristics that could enhance macrophytes growth. However, we do not discard a ＆mechanical＊ facilitation between E. azurea, which offers protection against windand waves, and the other species of macrophytes. A dinamica das comunidades vegetais 谷 fortemente influenciada pelasintera es positivas e negativas que desempenham papel importante na manuten o e diversidade das esp谷cies, coexist那ncia e produtividade das comunidades vegetais. Foram estudados os efeitos da macr車fita enraizada Eichhornia azurea sobre as esp谷cies de macr車fitas flutuantes Eichhornia crassipes, Salvinia minima, Salvinia auriculata e Limnobium laevigatum, em tr那s ressacos da plan赤cie de inunda o do alto rio Paran芍, Brasil. Para os experimentos in situ foram utilizados quadrados de 0,5 m de lado, onde estas esp谷cies cresceram durante 11 dias (S. auriculata e L. laevigatum) e 17 dias(E. crassipes e S. minima), em presen a e aus那ncia de E. azurea. N o houve diferen as significativas entre a taxa de crescimento relativo das macr車fitas flutuantes crescendo na aus那ncia e na presen a de E. azurea. O 赤ndice de intera o relativa demonstrou a exist那ncia de competi o entre esta esp谷cie e L. laevigatum e neutralidade na rela o com as demais esp谷cies. N o houve, por谷m, ind赤cios da ocorr那ncia de um mecanismo facilitador relacionado a mudan as nas caracter赤sticas f赤sicas e qu赤micas, ocasionadas por E. azurea, que estimulasse o crescimento das esp谷cies flutuantes. Por谷m, n o descartamos a ocorr那ncia de facilita o ＆mecanica＊ entre E. azurea, a qual oferece prote o contra as ondas e o vento, e as esp谷cies flutuantes livres.
