The Buxton Climate Change Impacts (BCCIL) study, established in 1992, is an experimental manipulation of climate factors in a species-rich limestone grassland in northern England. Despite 16 years of ongoing climate manipulations, community composition has remained remarkably stable in all experimental treatments. Expansion and contraction of genotypes, including fine-scale migration along a soil depth gradient, may be an important mechanism in the apparent resistance of this system to climate manipulations. The objective of this study was to determine the role of population level processes in community stability under climate change. Eighty individuals of the common perennial forb Plantago lanceolata were harvested from control and drought treatments at BCCIL across a soil depth gradient and grown in a common garden. Morphological, physiological and reproductive traits including leaf morphology, relative growth rate, photosynthetic rate, leaf turnover, and biomass allocation were collected for each individual. Amplified fragment length polymorphisms (AFLPs) were used to confirm genetic uniqueness of experimental individuals and to determine if genetic variation underlies adaptive phenotypes.

Results/Conclusions

There were shifts in functional traits of sampled genotypes among the two climate treatments. Genotypes harvested from drought treatments had earlier flowering phenology, higher reproductive allocation, and higher relative growth rate, traits consistent with a drought avoidance strategy. However, functional differences among treatments were not consistent across the soil depth gradient. Genotypes exhibiting traits conferring resistance to water loss (thicker leaves, slower growth rate, compact growth form) were more common in shallow microsites in both treatments, and most common in the drought treatment. Results from the AFLP analysis confirm the genetic uniqueness of each individual and provide evidence of genetic differentiation in response to long-term drought conditions.  Shifts in the functional characteristics of P. lanceolata in response to climate treatments suggest that the population harbors sufficient genetic diversity and could adapt to a range of environmental conditions via the expansion or contraction of genotypes. Furthermore, trait differentiation with respect to soil depth suggests that fine-scale spatial heterogeneity may buffer plant populations from harsher conditions under climate change. Taken together, the capacity of extant plant populations to adapt to climate change through physiological plasticity or genetic restructuring is likely an important determinant of the magnitude of vegetation response to anthropogenic climate change.