Resilience of montado understorey to experimental precipitation variability fails under severe natural drought

• Autor(a) principal: Jongen, Marjan
• Data de Publicação: 2013
• Outros Autores: Unger, Stephan, Fangueiro, David, Cerasoli, Sofia, Silva, João M.N., Pereira, J.S.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.5/11479
• topic: precipitation manipulation; drought; understorey vegetation; Mediterranean ecosystem; productivity; soil inorganic nitrogen

tFuture climate scenarios for the Iberian Peninsula predict increasingly variable precipitation regimes,challenging key ecosystem processes in the Mediterranean biome. This study presents a large-scale watermanipulation experiment, exposing the understorey vegetation in a Mediterranean oak woodland to sim-ulations of precipitation variability. We hypothesized that, with no net changes in rainfall quantity, largeinfrequent precipitation events extend the period of soil moisture deficit, thereby decreasing produc-tivity and soil nitrogen availability, accompanied by changes in plant community structure. However,the herbaceous understorey was highly resilient to increased precipitation variability. Extending the dryperiod between precipitation events from three to six weeks had no effect on productivity and commu-nity structure, this lack of responsiveness being attributed to phenotypic and physiological adaptations ofthe vegetation. However, vegetation senesced earlier, the shorter life cycle potentially influencing repro-ductive success. Additionally, experimental water manipulation did not affect soil nitrogen dynamics,with nitrogen being limiting in both treatments.In comparison, non-manipulated control plots experienced a severe natural wintertime drought, sig-nificantly reducing productivity and affecting species composition, but showed less indication of nitrogenlimitation. Thus, although the understorey vegetation was resilient to changes in precipitation variabil-ity, long drought periods exerted highly negative effects, with the vegetation not being able to bufferthe drought effects through adaptive strategies when the length of the dry period exceeded ∼10 weeks.Our results highlight the necessity for further studies investigating how climate change will influencethe co-limitation of water and nitrogen availability, which in turn might affect plant productivity inMediterranean ecosystems