Interactive effects of clipping and nutrient availability on the compensatory growth of a grass species Marja A. van Staalduinen • Iker Dobarro • Begonna Peco Received: 29 November 2008 / Accepted: 26 October 2009 / Published online: 5 November 2009 Ó Springer Science+Business Media B.V. 2009 Abstract Resource availability is an important fac- tor affecting the capacity of compensatory growth after grazing. We performed a greenhouse experiment with Poa bulbosa, a small perennial grass of the Mediter- ranean and Central Asian grasslands, to test the importance of nutrient availability for compensatory growth after clipping. We also compared the results with predictions of the limited resource model (LRM). Plants were grown at low and high fertilization levels and subjected to a clipping treatment. Contrary to the LMR, we found that in Poa plants compensatory growth occurred under the high fertilization level, while it did not occur under the low level. The LMR predicts a higher tolerance for grazing in the stressful environment. Our plants showed a significant decrease in their relative growth rates (RGR) after clipping. Although the plants allocated a 32–188% greater fraction of the mass to lamina growth after clipping, this greater allocation to the leaves did not fully compensate for the initial reduction in leaf area ratio (LAR). A sensitivity analysis showed for the clipped plants under the high fertilization treatment, that changes in leaf allocation (f lam ) enabled the plants to compensate for a part of the potential loss caused by defoliation. Probably, the increased biomass allocation comes largely from the bulbs. We conclude that the inconsistency of the LRM with our results originates in the lack of compensatory mechanisms in the model. To better understand how environmental conditions affect tolerance to herbivory, the effects of compensatory growth should be taken into account. Keywords Biomass allocation  Compensation  Herbivory  Growth analysis  Poa bulbosa  Resource availability Introduction Grazing by livestock is a common practice in grasslands, whereby plants frequently are subjected to partial defoliation. This partial defoliation may result in a considerable loss of leaf area, however, this will not always result in a proportional reduction in growth. Some plant species are able to recover from defoliation and possess characteristics through which they can continue or even increase growth after defoliation (Gold and Caldwell 1990; McNaughton 1983). In several studies, it has been observed that grassland productivity is stimulated by herbivory: the plants exhibited increased photosynthetic rates (Anten and Ackerly 2001a; Gold and Caldwell 1990; Nowak and Caldwell 1984), and relative growth rates (RGR, growth rate per unit plant biomass) after grazing or clipping (Hilbert et al. 1981; McNaughton 1983; Van Staalduinen and Anten 2005). M. A. van Staalduinen (&)  I. Dobarro  B. Peco Department of Ecology, Universidad Auto ´noma de Madrid, C/Darwin 2, Cantoblanco, 28049 Madrid, Spain e-mail: marjavs@xs4all.nl 123 Plant Ecol (2010) 208:55–64 DOI 10.1007/s11258-009-9686-0