地中海低木林における乾燥および窒素添加下でのローズマリー（Salvia rosmarinus）の色素再編成

Mediterranean-basin shrublands are a hotspot of biodiversity that is currently at risk due to concurrent global change drivers. Here, we investigated the simultaneous effects of a prolonged drought period and increased atmospheric nitrogen (N) deposition on photosynthetic and photoprotective pigments in rosemary (Salvia rosmarinus Spenn.), a widespread and iconic Mediterranean woody species in central Spain. We examined the concentrations and degree of coordination (coupling) of eight photosynthetic and photoprotective pigments under four N addition levels (0, 10, 20, and 50 kg·N·ha⁻¹·yr⁻¹) in response to a natural drought event and after a post-drought recovery phase. Our results showed that drought had a pronounced impact, leading to a reduction in chlorophylls, lutein, neoxanthin, and β-carotene, while increasing the concentration of photoprotective pigments associated with the xanthophyll cycle, particularly antheraxanthin and zeaxanthin. Drought also caused a disorganization (decoupling) of pigments, indicating poor metabolic homeostasis under extreme climatic conditions. On the other hand, recovery from drought resulted in increased coordination (coupling). The effects of N addition were minor and were mostly associated with greater β-carotene concentrations after drought, which we interpreted as indicative of greater oxidative stress. Our findings suggest that extreme drought events will likely have greater effects on pigment metabolism in Mediterranean woody plants compared to increased N deposition, although interactions between the two global change drivers could amplify physiological disruptions. Our results are amongst the first to show the metabolic decoupling of plants to concurrent global change drivers, paving the way for new studies focusing on understanding the coordination of physiological responses under stress rather than solely focusing on physiological responses per se.