Few effects of invasive plants Reynoutria japonica, Rudbeckia laciniata and Solidago gigantea on soil physical and chemical properties

Biological invasions are an important problem of human-induced changes at a global scale. Invasive plants can modify soil nutrient pools and element cycling, creating feedbacks that potentially stabilize current or accelerate further invasion, and prevent re-establishment of native species. The aim of this studywas to compare the effects of Reynoutria japonica, Rudbeckia laciniata and Solidago gigantea, invading non-forest areas located within or outside river valleys, on soil physical and chemical parameters, including soil moisture, element concentrations, organicmatter content and pH. Additionally, invasion effects on plant species number and total plant coverwere assessed. The concentrations of elements in shoots and roots of invasive and native plants were also measured. Split-plot ANOVA revealed that the invasions significantly reduced plant species number, but did not affect most soil physical and chemical properties. The invasions decreased total P concentration and increased N-NO_{3} concentration in soil in comparisontonative vegetation, though the latter only in the case of R. japonica. Theinfluenceof invasiononsoil propertiesdidnot dependon location(within- or outsidevalleys). The lack of invasion effects onmost soil properties does not necessarily imply the lack of influence of invasive plants, butmay suggest that the direction of the changes varies among replicate sites and there are no general patterns of invasioninduced alterations for these parameters. Tissue element concentrations,with the exception ofMg, did not differ between invasive and native plants, and were not related to soil element concentrations.