Divergent long- and short-term responses to environmental gradients in specific leaf area of grassland species

Specific leaf area (SLA) is one of the most widely researched plant traits, integrating multiple functions and reflecting plant resource acquisition strategies. However, the underlying mechanisms that drive temporal and spatial variation in SLA are still not clear. We used a combination of transect investigation and short-term manipulative experiments to identify patterns of variation in SLA over naturally occurring and simulated environmental gradients. We measured SLA of 631 species from the Tibetan (TP), Loess (LP), and Mongolian Plateaus (MP), where plant growth is limited by temperature, soil nutrient availability, and precipitation, respectively. In each plateau, we established an east–west transect of 10 sites, including meadow steppe (meadow), typical steppe (steppe), and desert steppe (desert) habitats. We further measured SLA of 15 species from the TP and MP, using manipulative experiments that altered temperature, precipitation and soil nitrogen levels. SLA ranged from 0.9 to 58.90 m2 kg−1 on average, and was significantly larger in desert than in meadow and steppe, except in the LP. Plants from the TP had significantly lower SLA than those from the LP and MP, but variation in SLA across the environmental gradients was small and consistent across the three plateaus. Conversely, the short-term manipulative experiments revealed that SLA increased with resource availability. Shifts in SLA across the broad environmental gradients was relatively small, and SLA had high sensitivity to short-term resource enrichment, suggesting that grassland species in these plateaus express divergent short- (acclimation) and long-term responses (adaptation) to the environment, which may be an important strategy for coping with ongoing shifts in climate.