Artemisia sieberi shrubs have contrasting specific effects on understory species in Iranian steppes

Questions (a) Are there contrasting short‐ and long‐term effects of shrubs on understorey species that may balance at the community level? (b) Are these effects due to the responses of different understorey species groups? (c) Are these effects contributing to community composition? Location An Artemisia steppe community in Golestan National Park (North‐East Iran). Methods We used both the removal and observational methods to separate short‐ from long‐term effects of Artemisia sieberi Besser on the cover of 18 subordinate species and the relative interaction index (RII) to calculate species’ responses. We conducted a principal components analysis (PCA) on species RII and grouped species with a cluster analysis depending on their responses to the shrubs. Another PCA on understorey composition plots was conducted to assess the consequences of shrub effects for community composition. Results Artemisia had negative short‐term and positive long‐term community‐level effects that balanced each other to produce neutral net effects. Short‐ and long‐term effects were due to the responses of different species groups, dominantly annuals and perennial grasses, respectively. Although balancing at the community level, the different shrub effects significantly contributed to explain community composition. Conclusions Our study highlights that a dominant foundation shrub may have contrasting short‐ and long‐term effects on different groups of understorey species that contribute to explain community composition, although balancing at the community level. We quantified the cover of understorey species under Artemisia sieberi, in plots with the shrub‐removed and open plots in order to separate short‐ from long‐term effects. Understorey species were grouped with a cluster analysis following a PCA conducted on their responses to the shrub. Artemisia had negative short‐term and positive long‐term effects on different groups of species that balanced at the community level.