Convergence patterns and multiple species interactions in a designed plant mixture of five species

Abstract

It is known that convergence and divergence can occur in complex plant communities, but the relative importance of biotic and abiotic factors driving these processes is less clear. We addressed this issue in an experiment using a range of mixed stands of five species that are common in Swiss fens (Carex elata, C. flava, Lycopus europaeus, Lysimachia vulgaris and Mentha aquatica) and two levels of water and nutrients. One hundred and seventy-six experimental mixtures were maintained in large pots (75 l) for two consecutive growing seasons in an experimental garden. The stands varied systematically in the initial relative abundance of each of the five species and in overall initial stand abundance. The changes in biomass over 2 years were modelled as linear functions of treatments and the initial biomass of each species. The dynamics of the system were mainly driven by differences in the identity of species and by a negative feedback mechanism but also by different abiotic conditions. In all mixtures, C. elata became more dominant over time, which caused an overall convergence of community composition. In addition, the rate of change of each species' biomass was negatively related to its own initial abundance. Thus, a negative feedback further contributed to the convergence of communities. Species responded differently to water level and nutrient supply, causing community dynamics to differ among treatments. However, the different abiotic conditions only slightly modified the overall convergence pattern. Competitive interactions between more than two species were weaker than the negative feedback but still significantly influenced the species' final relative abundance. The negative feedback suggests that there is niche partitioning between the species, which permits their coexistence.

Biology, chance, or history? The predictable reassembly of temperate grassland communities

“…legumes) in the resident community. However, invasion success was most strongly dependent on the biological difference between the invader and the invaded community (Strauss et al 2006, Suter et al 2007, permitting species that belonged to a functional group absent from a community to invade more easily than species belonging to a functional group already present (Fargione et al 2003, Turnbull et al 2005b). This strong negative interaction between residents and invaders of the same functional group could be due to overlapping resource requirements (e.g.…”

Comparative performance of invasive alien Eichhornia crassipes and native Ludwigia stolonifera under non-limiting nutrient conditions in Lake Naivasha, Kenya

“…The stronger intra-than inter-specific competition has been reported by many other studies (e.g. Suter et al, 2007;Johansson & Keddy, 1991). However Huckle et al, (2002) found the reverse pattern while (Aguiar et al, 2001) found equal strength of intra-and inter-specific competition.…”

“…According to Connolly & Wayne (2005), the large differences in RGR (species identity) observed in our experiment, would by themselves lead to considerable change in species' relative abundance in mixture, as they are much the strongest element in modifying structure. The importance of species identity relative to intraand inter-specific competition in structuring community final biomass has also been reported in other studies (Connolly & Wayne, 2005;Ramseier et al, 2005;Suter et al, 2007).…”

Competition alters plant species response to nickel and zinc

“…The net relative growth rate (RGR) between planting and harvesting was calculated following Connolly and Wayne (1996) and Suter et al (2007). For the calculation of RGR, the biomass of the three individuals per species and pot were pooled.…”