Oecologia (2009) 159:355–361 DOI 10.1007/s00442-008-1209-5 123 COMMUNITY ECOLOGY - ORIGINAL PAPER Understory plant diversity is related to higher variability of vegetative mobility of coexisting species Mari Moora · Maarja Öpik · Kristjan Zobel · Martin Zobel Received: 25 February 2008 / Accepted: 13 October 2008 / Published online: 4 November 2008  Springer-Verlag 2008 Abstract Theoretical studies claim that if co-occurring species have very diVerent mobilities this will result in greater small-scale species richness, but empirical evidence is still lacking. We measured horizontal vegetative mobility (VM) of 48 herbaceous understory species and estimated small-scale species richness in early and late successional boreonemoral herb-rich coniferous forests in central Esto- nia. VM of erosulate growth forms was signiWcantly higher than that of hemi-rosette and rosette growth forms. Erosul- ate species exhibited higher mobility in young stands, but their relative and total cover was considerably higher in old stands. Local plant richness (in 1 £ 1 m plots) correlated positively with the variability of VM of species in a plot— larger diVerences in VM resulted in a higher number of coexisting species. Our results thus suggest that species diVerences in VM can contribute to small-scale coexistence by providing diVerent ways to colonise empty space. Keywords Diversity · Forest Weld layer · Plant coexistence · Rhizome · Vegetative growth Introduction Plant communities exhibit considerable small-scale spatio- temporal turnover (van der Maarel and Sykes 1993, 1997). Recent theoretical developments indicate that spatial struc- ture in plant communities arises as an outcome of intra- and inter-speciWc competition, environmental heterogeneity, and localised dispersal (Seabloom et al. 2005). However, information on localised dispersal for plant communities is very scarce. In temperate perennial plant communities, recruitment from seedlings is generally very infrequent, and speciWc conditions are required for successful seedling establishment (Eriksson and Fröborg 1996; Eriksson 1997). Descriptive studies have concluded that most small-scale turnover in perennial communities is due to the establish- ment of new individuals in empty micro sites by clonal growth (Klimes 1999; Otsus and Zobel 2002; Benson and Hartnett 2006). Because plant species exhibit marked diVerences in the speed of colonisation of free microhabi- tats over time (Herben et al. 1995; Wildova 2004; Wildova et al. 2007), small-scale spatial structure of, and species coexistence within, plant communities evidently depends on the clonal growth parameters of individuals. Empty space in a plant community may arise either due to death of individuals or external disturbances. For peren- nial vegetation, where clonal regeneration overwhelmingly dominates over regeneration from seeds, the speed of gap colonisation via vegetative spread depends on the growth form of the species (Lovett Doust 1981; Klimes et al. 1997) and on the plastic response of a species to local environ- mental conditions (Hutchings et al. 2003). Although we know that the proportion of growth forms varies among plant communities (van Groenendael et al. 1996; Liira et al. 2002; Song et al. 2002; Klimes 2003; Halassy et al. 2005), very little is known of the actual spatial mobility of species Communicated by Melinda Smith. Electronic supplementary material The online version of this article (doi:10.1007/s00442-008-1209-5) contains supplementary material, which is available to authorized users. M. Moora (&) · M. Öpik · K. Zobel · M. Zobel Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, 51005 Tartu, Estonia e-mail: mari.moora@ut.ee