Diversity loss in grasslands due to the increasing dominance of alien and native competitive herbs

Abstract

The increasing dominance of competitive plant species may reduce species richness of plant communities. Yet, species richness may depend on spatial scale and the alien versus native status of the dominant species. To explore the dominance effects of alien versus native species on species richness, we sampled semi-natural grasslands in southwestern Poland. We established 100 m 2 squares at different grassland sites, and in two opposite corners we placed two series of five nested plots (0.001, 0.01, 0.1, 1 and 10 m 2), in which we recorded all vascular plant species. Next, we selected squares with a strongly dominant plant in one corner (high-dominance series) and with no strong dominant in the opposite corner (low-dominance series). The number of species per plot and the slopes of the species-area curves fitted to each nested-plot series were used to assess whether the alien vs. native status of the dominant species influences species-richness pattern across scales. We found a significantly lower number of species in the high-dominance series than in the low-dominance series, regardless of the alien versus native status of the dominant species. The slopes of the species-area curves indicated that the rate of species accumulation with increasing area was faster in the high-dominance series than in the low-dominance series; however, this pattern did not depend on the alien vs. native status of the dominants. Our study confirms that increasing dominance is linked to a decline in species richness, but reveals that alien dominants do not have a stronger impact than native dominants.

Negative impacts of dominance on bee communities: Does the influence of invasive honey bees differ from native bees?

“…A small number of species typically dominate communities, and they often have outsized impacts on the communities they inhabit (Smith and Knapp 2003, Sasaki and Lauenroth 2011, Czarniecka-Wiera et al 2019. Invasive species are notorious for their ability to reach high abundances and dominate native environments (Goulson 2003, Torchin et al 2003, David et al 2017).…”

Invasion Success of Bunias orientalis (Warty Cabbage) in Grasslands: A Mesocosm Experiment on the Role of Hydrological Stress and Disturbance

“…Grasslands are important biomes rich in biodiversity, accounting for nearly 25% of land surface on Earth (Gang et al, 2015); they offer key ecosystem services balancing the concentrations of global atmospheric greenhouse gases (O'Mara, 2012), protecting soil and water resources (Vogt et al, 2019) and providing livestock forage and therefore meat and milk for human consumption (O'Mara, 2012). Nevertheless, they are one of the most sensitive ecosystems to global climate change drivers (Seastedt and Pyšek, 2011), where anthropogenic influence accelerated their decline over the last decades (Czarniecka-Wiera et al, 2019). Indeed, as a consequence of abandonment and changing of traditional management toward intensification, European grasslands have experienced a decrease in species richness and changes in competitive regimes (Römermann et al, 2009), being also increasingly disturbed by frequent mowing or grazing (Stampfli et al, 2018).…”

Passive regeneration of subtropical grassland vegetation in a chronosequence of ex‐cultivated fields in Australia

“…It is generally accepted that exotic species can suppress recovery in grasslands (Camill et al, 2004; Tognetti et al, 2010) but there are also examples where a dominant native species impedes succession, particularly in the semi‐natural grasslands of Europe (Bobbink & Willems, 1987; Albert et al, 2014; Ruprecht et al, 2016; Czarniecka‐Wiera et al, 2019). For instance, Ruprecht (2006) found out that the native grass Stipa pulcherrima suppressed recovery in Romanian grasslands.…”