Comparison of understory plant community composition and soil characteristics in Quercus pyrenaica stands with different human uses Reyes Ta ´rrega a, * , Leonor Calvo a , Elena Marcos a , Angela Taboada b a Area de Ecologı ´a, Facultad de Ciencias Biolo ´gicas y Ambientales, Universidad de Leo ´n, Campus Vegazana, 24071 Leo ´n, Spain b Departamento de Biologı ´a Animal, Facultad de Ciencias Biolo ´gicas y Ambientales, Universidad de Leo ´n, 24071 Leo ´n, Spain Received 17 May 2006; received in revised form 23 October 2006; accepted 11 January 2007 Abstract The species composition of the plant community and the soil characteristics in Quercus pyrenaica ecosystems according to the degree of disturbance and the type of human intervention (burning, cutting, livestock grazing) were compared. Four types of oak communities were selected, each with five replicates: oak shrublands (SL), dehesas (DE) or open woodlands used for grazing, and two types of mature oak forest, one with abundant shrub biomass in the understory (FS) and the other with little shrub biomass in the understory (FO). A total of 175 species were found in the 20 sites studied, 52 appeared in a single site. The dehesas were the most different regarding species composition, with 30 species only found there. This was verified by a qualitative similarity analysis, in which the five dehesas formed a group clearly distinguishable from the other sites; the oak shrublands also formed a group, but it was not possible to distinguish between the mature oak forests with and without a shrubby understory. However, the soil characteristics were similar across all sites and differences could only be detected in organic matter and nitrogen content, which were significantly higher in the mature forests without a shrubby understory. When the plant community and soil characteristics were analysed as a whole using a canonical correspondence analysis, the separation of the dehesas was observed on the first axis, due to its greater richness and abundance in herb species, especially annuals. The other sites were ordered on the second axis, with greater differences between the oak shrublands, associated with higher shrub species cover, and the mature open forests, associated with forest herb species and a soil with a higher nitrogen, organic matter and cation exchange content. The mature forests with abundant shrub biomass were in an intermediate position. Therefore, although the differences in soil were not important and many species were common to all types of Q. pyrenaica communities, the type of human intervention did determine changes, as shown by the results of the multifactorial analyses. In addition, given that all the community types presented some species which were not found in the other types, greater biodiversity would be attained by preserving all of them. # 2007 Elsevier B.V. All rights reserved. Keywords: Oak shrublands; Dehesas; Mature forests; Management; Land-use history; Grazing; Disturbances; Low layer species; Soil conditions 1. Introduction The species composition and characteristics of a forest understory depend to a great extent on both past and present events, including the frequency and intensity of disturbances (Bormann and Likens, 1979). Forest management is one of the human disturbances that affects species diversity and composi- tion, as well as forest structure and function (Hunter, 1999; Tybirk and Strandberg, 1999). In addition, these disturbances usually produce alterations in the soil processes (Kimmins, 1987). However, there are not always clear relationships among soil properties and forest management (Rubio et al., 1999). It is generally assumed that after tree harvesting total species richness increases in temperate forests, mostly due to the establishment of shade intolerant ruderal species (Bormann and Likens, 1979; Elliott et al., 1997). Other types of management, like grazing, determine changes in species composition and in species diversity, but the effects are not the same for all forest ecosystems (Gonza ´lez-Herna ´ndez and Silva-Pando, 1996; Krzic et al., 2003; Weisberg and Bugmann, 2003; Onaindia et al., 2004). Many authors found no changes in the diversity values as a result of management but did find changes in species composition (Fredericksen et al., 1999; Brosofske et al., 2001; Nagaike et al., 2003). However, the opposite occurred in other cases, as in the study by Schumann et al. (2003), where differences in total species richness appeared between harvest gaps and controls but the species composition overlapped considerably. As regards effects of forest management on the www.elsevier.com/locate/foreco Forest Ecology and Management 241 (2007) 235–242 * Corresponding author. Tel.: +34 987 291567; fax: +34 987 291409. E-mail address: r.tarrega@unileon.es (R. Ta ´rrega). 0378-1127/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2007.01.011