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Afforestation programs such as the one promoted by the EU Common Agricultural Policy have spread tree plantations on former cropland. These afforestations attract generalist forest and ubiquitous species but may cause severe damage to open habitat species, especially birds of high conservation value. We investigated the effects of young (< 20 yr) tree plantations dominated by pine P. halepensis on bird communities inhabiting the adjacent open farmland habitat in central Spain. We hypothesize that pine plantations with larger surface, and areas at shorter distances from plantations, would result in lower bird species richness and conservation value of open farmland birds. Regression models controlling for the influence of land use types around plantations revealed significant positive effects of distance to pine plantation edge on community species richness in winter, and negative effects on an index of conservation concern (SPEC) during the breeding season. However, plantation area did not have any effect on species richness or community conservation value. Our results indicate that pine afforestation of Mediterranean cropland in heterogeneous agricultural landscapes has an overall low detrimental effect on bird species that are characteristic of open farmland habitat.
List of all species surveyed on farmland habitat adjacent to tree plantations in Central Spain
Table S1. List of all species surveyed at 80 1000 m long x 200 m wide transects located on farmland habitat adjacent to tree plantations in Central Spain. For each species, the following information is provided for the entire transect and for two segments of the transect (i.e. < 400 m or close to tree plantations and > 600 m or away for plantations): frequency (number of transects where the species occurred), local abundance (number of individuals km-2, mean ± sd), regional abundance at six farmland habitat types in the Mesomediterranean region in the breeding season (number of individuals km-2, mean ± sd; source: Carrascal and Palomino 2008), SPEC (source: BirdLife International 2004b) , inclusion in the European farmland bird index (EFBI, + if included, source: Directorate-General for Agriculture and Rural Development 2012) , and inclusion in the list of common farmland birds in Southern Europe (CFMSE, + if included, source: European Bird Census Council). The study area was not part of the distribution area of 10 species included in the CFBI list (Ciconia ciconia, Corvus frugilegus, Emberiza citrinella, Emberiza melanocephala, Lanius collurio, Lanius minor, Limosa limosa, Perdix perdix, Saxicola rubetra and Sturnus vulgaris) and six species included in the CFMSE list (the former but C. frugilegus, E. citrinella, L. limosa and S. rubetra). * indicates the species that were not considered for statistical analyses in this study.