Salpichroa origanifolia (Lam.) Baillon is a perennial herb of the Solanaceae family, native to the temperate regions of South America, where it grows from 0 to 2500 m asl, often behaving as a ruderal species. The species is naturalised in Europe, is not listed as an invasive alien species of EU concern and is not included in any of the EPPO lists. Although reports from European countries are scarce, S. origanifolia has been found spreading rapidly in southern Switzerland and the Canary Islands. In Italy, the species is present in most regions and its status was recently changed from naturalised to invasive in Campania and Calabria (1). Pathways of introduction can be unintentional, through trade in seeds and potted plants containing seeds or stem fragments, or intentional, as ornamental, or melliferous plant. The first report for Tuscany dates to 1923, but around 2000 the species was still considered rare (5). Salpichroa origanifolia was not present in San Rossore before 2000 (2), and it was accidentally found in cut stone pine plantations and near the buildings at the entrance to the reserve in 2008 (3). Ten years later, S. origanifolia showed a clear invasive habit, forming dense stands at forest edges, under isolated trees and inside the forest, especially in correspondence of fallen trees. Phenological and morphological traits of this species contribute to its invasiveness. Shoots vegetate from March to December, and the flowering period is very long, from April to October. Plants spread rapidly producing scrambling and rooting aerial stems, and two types of rhizomes: fine fleshy, 3-5 mm in diameter, just below the soil surface, and around 7-mm-thick deep growing woody rhizomes. This study assessed the competitiveness of S. origanifolia against native forest species, by analysing the weekly emergence and the biomass achieved after 11 weeks. The soil seed bank was collected in the forest of San Rossore, from two sites with different levels of S. origanifolia invasion: one with a low (LD So) and one with a high (HD So) density. Two additional treatments, arranged in a split-plot design, were imposed: light conditions (full sunlight/canopy shade) and the presence or absence of S. origanifolia rhizomes. The light treatment was set to test if the invasiveness of S. origanifolia and its effect on the soil seed bank varied between undergrowth and open areas. Results showed that, in both sites, the presence of S. origanifolia rhizomes did not inhibit either the germination rate or the biodiversity of native plants. However, in the full light treatment, the presence of S. origanifolia increased the germination rate, suggesting that shading by this invasive species had an initial positive effect on the understorey species. Results concerning biomass differed between sites. In the low-density site, we observed a difference in the biomass of native species between treatments with or without S. origanifolia. In the former case, the biomass was reduced by about a half. In the high-density site, the biomass of the native species was generally very low, independently on the presence of S. origanifolia rhizomes. This is to impute to the emergence of S. origanifolia seedlings from the soil seed bank, which were very competitive against native species. In fact, their biomass was fivefold higher than that of the native seedlings. Furthermore, the biomass achieved by a single S. origanifolia seedling was 2 g, whereas that of a seed bank seedling was just 0.05 g.
Effects of the invasive alien Salpichroa origanifolia on the soil seed bank of a mixed forest (San Rossore, Migliarino, Massaciuccoli Regional Park, Pisa).
Alessandrini V.
Primo
;Arduini I.Ultimo
2023-01-01
Abstract
Salpichroa origanifolia (Lam.) Baillon is a perennial herb of the Solanaceae family, native to the temperate regions of South America, where it grows from 0 to 2500 m asl, often behaving as a ruderal species. The species is naturalised in Europe, is not listed as an invasive alien species of EU concern and is not included in any of the EPPO lists. Although reports from European countries are scarce, S. origanifolia has been found spreading rapidly in southern Switzerland and the Canary Islands. In Italy, the species is present in most regions and its status was recently changed from naturalised to invasive in Campania and Calabria (1). Pathways of introduction can be unintentional, through trade in seeds and potted plants containing seeds or stem fragments, or intentional, as ornamental, or melliferous plant. The first report for Tuscany dates to 1923, but around 2000 the species was still considered rare (5). Salpichroa origanifolia was not present in San Rossore before 2000 (2), and it was accidentally found in cut stone pine plantations and near the buildings at the entrance to the reserve in 2008 (3). Ten years later, S. origanifolia showed a clear invasive habit, forming dense stands at forest edges, under isolated trees and inside the forest, especially in correspondence of fallen trees. Phenological and morphological traits of this species contribute to its invasiveness. Shoots vegetate from March to December, and the flowering period is very long, from April to October. Plants spread rapidly producing scrambling and rooting aerial stems, and two types of rhizomes: fine fleshy, 3-5 mm in diameter, just below the soil surface, and around 7-mm-thick deep growing woody rhizomes. This study assessed the competitiveness of S. origanifolia against native forest species, by analysing the weekly emergence and the biomass achieved after 11 weeks. The soil seed bank was collected in the forest of San Rossore, from two sites with different levels of S. origanifolia invasion: one with a low (LD So) and one with a high (HD So) density. Two additional treatments, arranged in a split-plot design, were imposed: light conditions (full sunlight/canopy shade) and the presence or absence of S. origanifolia rhizomes. The light treatment was set to test if the invasiveness of S. origanifolia and its effect on the soil seed bank varied between undergrowth and open areas. Results showed that, in both sites, the presence of S. origanifolia rhizomes did not inhibit either the germination rate or the biodiversity of native plants. However, in the full light treatment, the presence of S. origanifolia increased the germination rate, suggesting that shading by this invasive species had an initial positive effect on the understorey species. Results concerning biomass differed between sites. In the low-density site, we observed a difference in the biomass of native species between treatments with or without S. origanifolia. In the former case, the biomass was reduced by about a half. In the high-density site, the biomass of the native species was generally very low, independently on the presence of S. origanifolia rhizomes. This is to impute to the emergence of S. origanifolia seedlings from the soil seed bank, which were very competitive against native species. In fact, their biomass was fivefold higher than that of the native seedlings. Furthermore, the biomass achieved by a single S. origanifolia seedling was 2 g, whereas that of a seed bank seedling was just 0.05 g.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
