Seedling root traits strongly influence field survival and performance of a common bunchgrass

Abstract

Seedling survival is a limiting factor in arid-land restoration. We investigated how variation in the root traits of glasshouse-reared seedlings related to the field performance of different genotypes from two populations of Elymus elymoides (squirreltail), a common bunchgrass native to the Western United States. Seeds from 100 E. elymoides individuals were collected from two sites in northern Nevada. We planted offspring of these 100 individuals in the glasshouse to characterize 10-day root traits of each maternal family. Root traits of glasshouse-reared plants and seed size measures were correlated with the performance of siblings grown in field plots close to the seed collection sites. Seedling root traits were related to performance of siblings at both sites. We estimate that within-population variation in root traits was associated with a more than six- to nine-fold increase in seedling survival probability and a two-fold increase in height at the less productive site, and a two-fold increase in survival and 1.2-fold increase in size at the more productive site. At both sites, effects of root traits were complex, with extreme values of some traits favoured and intermediate values of other traits favoured. There is a recognized need to integrate understanding of plant functional traits into larger conceptual frameworks of ecological restoration. Here we show that within-population variation in a suite of root functional traits relates to large variation in seedling survival and size of an arid-land grass species, improving our understanding of how trait variation affects performance in the field. Understanding such variation may be used to positively impact restoration outcomes.