Data from: The association between a nurse cushion plant and a cluster-root bearing tree species alters the plant community structure

1.Several plant species have the potential to facilitate the presence of
other plant species in the community, and yet most of our knowledge on
this phenomenon comes from studies considering only one facilitator
species. What happens when there are two facilitator species in the
community? Are the facilitation effects by one species being altered by
the presence of a potentially second facilitator species and vice‐versa
(i.e. bidirectional facilitation)?. 2.Knowing that cushion plants
ameliorate stress and improve soil fertility and that cluster‐root bearing
species mobilise soil phosphorus (P), we investigated the potential
occurrence of bidirectional facilitation via stress amelioration and
nutrient exchange in the cushion plant Acaena integerrima (Rosaceae) and
the cluster‐root bearing tree species Embothrium coccineum (Proteaceae).
3.In southern Chile, where both species naturally occur, we compared
aspects of the vegetative and reproductive performance of each species
growing in association or not. We also determined if Embothrium alters the
nurse effects of Acaena cushions on other species by evaluating species
richness, frequency, and abundance in cushion plants with and without
Embothrium. To infer the existence of nutrient exchange, we determined
soil and leaf nutrient levels of both species. 4.Species richness,
frequency, and abundance were higher within than outside Acaena cushions.
Although the presence of Embothrium did not enhance the overall positive
effects of Acaena on species composition, nine species occurred more
frequently when Embothrium was present. Embothrium occurred more
frequently and had a higher survival and leaf nitrogen (N) concentration
when growing with Acaena than without it, although its growth and leaf P
concentration were lower. In contrast, Acaena had a lower number of and
mass of fruits per inflorescence and a higher leaf P concentration when
growing with versus growing without Embothrium. 5.Synthesis. The cushion
plant Acaena integerrima facilitates the occurrence of many species in the
community, including the cluster‐root bearing species Embothrium
coccineum, which in turn enhances the facilitation effect of Acaena on
certain species. When Embothrium and Acaena occur together, the latter
improves its nutritional status but reduces its fitness, implying a lack
of bidirectional facilitation.