Allelopathy of a native grassland community as a potential mechanism of resistance against invasion by introduced plants

Abstract

Successful plant invasions depend, at least partly, on interactions between introduced plants and native plant communities. While allelopathic effects of introduced invaders on native resident species have received much attention, the reverse, i.e. allelopathic effects of native residents on introduced plants, have been largely neglected. Therefore, we tested whether allelopathy of native plant communities decreases their invasibility to introduced plant species. In addition, we tested among the introduced species whether the invasive ones are more tolerant to allelopathy of native plant communities than the non-invasive ones. To test these hypotheses, we grew nine pairs of related (congeneric or confamilial) invasive and non-invasive introduced plant species (i.e. 18 species) in the presence or absence of a native grassland community, which consisted of three common forbs and three common grasses, with or without activated carbon in the soil. Activated carbon reduced the survival percentage and growth of introduced plants in the absence of the native plant community. However, its net effect on the introduced plants was neutral or even slightly positive in the presence of the native community. This might suggest that the native plant community imposed allelopathic effects on the introduced plants, and that these effects were neutralized or reduced by activated carbon. The invasive and non-invasive introduced plants, however, did not differ in their tolerance to such allelopathic effects of the native plant community. Thus, although allelopathy of native plant communities might increase their resistance against introduced plants, there was no evidence that tolerance to allelopathy of native plant communities contributes to the degree of invasiveness of introduced plants.

The Effects of Soils from Different Forest Types on the Growth of the Invasive Plant Phytolacca americana

“…Some evidence has suggested that allelopathic native plants play a role in inhibiting the growth of invaders [37][38][39]. We found that the allelopathic activity in natural forest soil and litter inhibited the growth of P. americana but that RP soil promoted its growth (Figures 2 and 3), which seems to confirm our second hypothesis: Allelopathy of natural forests inhibits P. americana growth and that of the R. pseudoacacia plantation promotes its growth.…”

“…Similarly, Hou et al [39] found that monsoon evergreen broadleaf forest soil has strong allelopathic activity towards invasive plants in lower subtropical China. Ning et al [37] provided evidence that in grassland communities allelopathic native grasses increased community resistance to introduced plants. However, this study did not produce results for succession-associated allelopathy consistent with Hou et al [39], who found that late-successional stage forest soils have stronger allelopathy than early-successional stages.…”

“…Some studies have indicated that there may be potential side effects related to soil properties, microbes and plant growth when using activated carbon to adsorb allelochemicals in the soil [70,71]. Despite this concern, activated carbon, due to its effectiveness in absorption of allelochemicals, is still utilized by many researchers to neutralize allelochemicals in order to study the allelopathy of plants [21,36,37,39,72]. Additionally, caution should be exercised when using laboratory bioassays to simulate a complex field environment [66,73].…”

When facilitation meets clonal integration in forest canopies

“…In both the survival and biomass models, we included epiphyte species, severance, removal and their two-and three-way interactions as fixed terms. We accounted for differences in initial size of the epiphyte ramets by including initial size (frond length) as a covariate in the model (Ning et al, 2016). Furthermore, we accounted for variation among host species and host trees (treeID) by including them as random terms, with individual host trees nested within host species.…”

Diversity- and density-mediated allelopathic effects of resident plant communities on invasion by an exotic plant

“…However, the resident plants may also produce allelopathic compounds, and it could be that allelopathy of resident plants provides resistance against invaders (Weidenhamer and Romeo 2005). Although this idea was already posed by Rabotnov (1982), it has rarely been tested (Cummings et al 2012;Hou et al 2012;Ning et al 2016;van Kleunen et al 2018).…”