Abstract: Root lifespan is an important functional trait associated with water and nutrient acquisition, species coexistence, and community diversity. Although previous studies have shown that root lifespan varies among root orders in woody plants, it remains unclear whether similar patterns occur in herbaceous species. We determined and compared root longevity of ten coexisting species using rhizotrons by monitoring 28,763 roots at a 10-day interval from May 2013 to October 2014 in a temperate steppe in northern China. Mean root lifespan of herbaceous species in temperate grasslands exhibited distinct differences among root orders, such that the averaged lifespan of second-order roots was approximately 2-fold longer than that of first-order roots across the ten species. In addition, mean root lifespan among the examined species differed substantially, ranging from 59.25 days for a forb species of Artemisia frigida to 221.5 days for a grass species of Agropyron cristatum. These results revealed that root lifespan differed among plant species in the grassland community, with grasses having longer-lived roots than forbs. As in woody species, first-order roots of herbaceous species in temperate grasslands were shorter-lived than second-order roots. Differences in root lifespan among species and plant functional types in the steppe community may highlight the diverse strategies for resource acquisition among coexisting species in grassland ecosystems.

Key words: Herbaceous species, rhizotron, root branching order, root longevity, temperate grasslands