Stature of dependent forbs is more related to the direct and indirect above‐ and below‐ground effects of a subalpine shrub than are foliage traits

Abstract

AbstractQuestionGraminoid/shrubland communities include groups of forbs (herbaceous dicots) that differ in their traits, and in their direct and indirect responses to dominant neighbours. Although we have a growing knowledge of which traits might influence species’ direct responses to dominant neighbours, and in particular the crucial importance of plant stature over foliage traits, less is known about the relationship between species’ traits and direct responses to dominant neighbours.LocationAn alpine graminoid/shrubland co‐dominated by the shrub Dasiphora fruticosa and graminoids such as the sedge Kobresia capillifolia on the Tibetan plateau (China).MethodsThe above‐ and below‐ground effects of the shrub in the absence or presence of graminoids were manipulated to quantify direct and indirect responses of forb species, which were grouped with a PCA. For the forbs, six traits characterizing both plant stature and foliage properties were measured and a redundancy analysis was used to assess their patterns of direct and indirect responses to the dominant neighbours.ResultsWe found contrasting direct and indirect responses of forb species to the graminoids, and the above‐ and below‐ground effects of the shrubs, separating the forbs into four species‐groups. A significant positive indirect net effect of the shrubs was observed at the community‐level. Traits of forb species were more tightly related to direct than indirect responses to dominant neighbours, while plant stature had a primary influence over foliage traits, which was only very weakly related to indirect responses.ConclusionsAlthough plant traits, in particular plant stature, have strong influences on species’ direct responses to dominant neighbours, relationships to indirect interactions are more subtle and variable. This inhibits our prediction of the influence of species’ traits on species composition of the community through indirect interactions.