title: Long-term simulated nitrogen deposition alters the plant cover dynamics of a Mediterranean rosemary shrubland in Central Spain through defoliation.
abstract: Nitrogen (N) deposition due to anthropogenic pollution is a major driver of the global biodiversity loss. We studied the effect of experimental N and phosphorus (P) fertilization (0, 10, 20, and 50 kg N ha-1year-1and 14 kg P ha-1year-1over the background deposition levels) on plant cover dynamics of a rosemary (Rosmarinus officinalis L.) shrubland after 8 years of nutrient addition in a semiarid Mediterranean ecosystem from Central Spain. We specifically aimed at testing whether N deposition has the potential to influence the observed expanding trend of woody vegetation into areas dominated by grassland, biological soil crusts, and bare soil. Our results show that N addition loads above 10 kg N ha-1year-1reverted the cover dynamics of shrubs. Under N addition conditions, N was no longer a limiting nutrient and other elements, especially P and calcium, determined the seasonal growth of young twigs. Interestingly, N fertilization did not inhibit the growth of young shoots; our estimates point to a reduced rosemary leaf lifespan that is driving individuals to death. This may be triggered by long-term accumulation of N compounds in leaves, suggesting the need to consider the old organs and tissues in long-lived perennial plants, where N toxicity effects could be more mediated by accumulation processes. Shrublands are a widely distributed ecosystem type in biodiverse Mediterranean landscapes, where shrubs play a key role as nurse plants. Therefore, the disappearance of shrublands may accelerate the biodiversity loss associated with other global change drivers, hamper the recruitment of seedlings of woody species, and, as a consequence, accelerate desertification.
authors.affiliation: Museo Nacional de Ciencias Naturales CSIC, Serrano 115 dpdo, 28006, Madrid, Spain. ccabal@princeton.edu.|Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, 08544, USA. ccabal@princeton.edu.
authors.forename: Ciro
authors.initials: C
authors.lastname: Cabal
authors.affiliation: Department of Ecology, Universidad Autónoma de Madrid, C/Darwin 2, 28049, Madrid, Spain.
authors.forename: Raúl
authors.initials: R
authors.lastname: Ochoa-Hueso
authors.affiliation: Department of Ecology, Faculty of Biology, Universidad Complutense de Madrid, C/José Antonio Novais 2, 28040, Madrid, Spain.
authors.forename: María Esther
authors.initials: ME
authors.lastname: Pérez-Corona
authors.affiliation: Museo Nacional de Ciencias Naturales CSIC, Serrano 115 dpdo, 28006, Madrid, Spain.
authors.forename: Esteban
authors.initials: E
authors.lastname: Manrique
mesh_terms: D044822:Biodiversity; D017753:Ecosystem; D005308:Fertilizers / Q000633:toxicity*; D009584:Nitrogen / Q000032:analysis / Q000633:toxicity*; D010758:Phosphorus / Q000032:analysis / Q000633:toxicity; D027542:Rosmarinus / Q000187:drug effects*; D036226:Seedlings / Q000737:chemistry / Q000187:drug effects; D012987:Soil; D012989:Soil Pollutants / Q000633:toxicity*; D013030:Spain
chemical_list: D005308:Fertilizers; D012987:Soil; D012989:Soil Pollutants; D010758:Phosphorus; D009584:Nitrogen
keywords: Defoliation; Leaf lifespan; Long-term nutrient addition; Mediterranean ecosystems; Nitrogen deposition; Phosphorus; Semiarid shrublands; Shrub cover