Plant competitive ability and the transitivity of competitive hierarchies change with plant age

Abstract

Plant competitive effect and response ability are known to change with plant age, however it remains unclear how competitive hierarchies among plant species change as plants age and transition between life stages. We examined the competitive interactions among seven species in all pairwise combinations in a greenhouse experiment. Competitive effect and response were measured as the relative yield (RY) for each target-neighbor species combination for both seedling and adult plants. Competitive hierarchies were constructed based on competitive effect and response scores, and we examined the degree of transitivity in the seedling and adult competitive hierarchies. The competitive effect hierarchy did not vary substantially with plant age, while the competitive response hierarchy was highly variable between juvenile and adult plants. Competitive effect and response ability were positively correlated at both plant stages. The seedling relative yield matrix was predominantly transitive, while there were far fewer transitive competitive relationships among the adult plants. The breakdown of the clear competitive hierarchy among seedlings as plants aged may explain why competition does not appear to be an active mechanism structuring some late-successional plant communities. In early-successional communities, interactions among seedlings with a clear competitive hierarchy may establish competitive ability-abundance relationships that persist as a legacy effect even though the breakdown of the competitive hierarchy among adult plants removes competition as an active mechanism structuring some late-successional plant communities.

Everything you always wanted to know about intransitive competition but were afraid to ask

“…It has been argued that strong intransitivity may not easily occur in nature as it requires the three species involved to be present simultaneously (e.g. Gallien et al., ; but see Stouffer et al., ; Zhang & Lamb, ). In this special feature, Gallien et al.…”

“…It has been argued that strong intransitivity may not easily occur in nature as it requires the three species involved to be present simultaneously (e.g. Gallien et al, 2017; but see Stouffer et al, 2018;Zhang & Lamb, 2012). In this special feature, Gallien et al (2018) explore a potential mechanism by which initially weak intransitive competition could strengthen through time.…”

Functional traits and environmental characteristics drive the degree of competitive intransitivity in European saltmarsh plant communities

“…The hypothesis of competitive intransitivity (Gilpin, 1975) has regained attention among ecologists as new empirical approaches (Soliveres et al, 2011;Zhang & Lamb, 2012) and analytical tools (Rojas-Echenique & Allesina, 2011;Ulrich, Soliveres, Kryszewski, Maestre, & Gotelli, 2014) have revealed complex competitive interactions in multi-species ecological communities (Allesina & Levine, 2011;Engel & Wetzin, 2008;Gallien, 2017). Here, intransitivity refers to loops in the hierarchy of competitive interactions in which species A is superior to species B, B is superior to C and C is superior to A.…”

“…Westoby, Falster, Moles, Vesk, & Wright, 2002;Paine, Baraloto, Chave, & Herault, 2011; but see Kusumoto et al, 2016 andGallien, 2017), and this separation of species in trait space may generate sufficient niche differentiation to permit species coexistence (Adler, Fajardo, Kleinhesselink, & Kraft, 2013). However, a different although not mutually exclusive explanation for the observed degree of coexistence is that the mix of competitively counteracting traits, such as root and shoot competition (Zhang & Lamb, 2012), or complementary resource use (Yachi & Loreau, 2007), generates a dynamic balance of competitive strength through ICNs, which allows for species coexistence in spite of high niche overlap. Thus, we interpret ICNs as a cause, not an effect, of high species richness.…”

Differences for traits associated with early N acquisition in a grain legume and early complementarity in grain legume–triticale mixtures

“…These mechanisms will have an impact on the competitive ability of each plant later in the cycle. Zhang and Lamb (2012) found that early differences between species for competitive effect did not vary substantially with plant age. As suggested by Fayaud et al (2014), a better understanding of early growth in intercrop systems could help to adapt management practices to attain specific objectives, such as proper proportion of each species in terms of grain yield.…”