Linking leaf economic traits with forage quality across temperate grasslands under ambient and drought conditions

Intensifying droughts may disrupt grassland services, including the forage provision for herbivores. However, less is known about drought impacts on forage quality. While previous studies have shown that leaf economic traits reflect drought effects on plant communities, whether leaf traits can predict forage quality pattern under drought remains unclear. So, we simulated early- and late-season droughts in three grasslands in the Swiss Jura Mountains over two growing seasons. Early-season drought involved a 70% reduction in ambient precipitation during the first two-month growth cycle of a six-month growing season, while late-season drought reduced same precipitation during the second two-month growth cycle. We collected data on forage quality parameters (protein, minerals, water-soluble carbohydrates, neutral detergent fibre, and acid detergent fibre) and leaf traits [community-weighted mean (CWM) specific leaf area (SLA) and leaf dry matter content (LDMC)]. We used these data to address three questions: (1) how do forage quality parameters and leaf economic traits [community-weighted (cwm) SLA and LDMC] changed from early to late periods of the season under ambient conditions; (2) how do forage quality parameters and leaf traits respond to early- and late-season droughts; and (3) how do community-weighted leaf traits and forage quality parameters relate under early- and late-season ambient and drought conditions.