Differences in spatial and temporal root lifespan of three Stipa grasslands in northern China

Abstract

Lifespan of fine root plays an important role in regulating carbon (C) cycling in terrestrial ecosystems. Determination of root lifespan and elucidation of its regulatory mechanism in different plant communities are essential for accurate prediction of C cycling from ecosystem to regional scales. There are three major types of grasslands in the temperate steppes of Inner Mongolia, each dominated by a different species of common grass: Stipa krylovi, Stipa grandis, and Stipa breviflora. There have been no studies to compare the root dynamics among the three types of grasslands. In the present study, we determined root lifespan of the three grasslands using the rhizotron technique. We found that root lifespan differed substantially among the three major types of grasslands within the temperate steppes of Inner Mongolia, such that root lifespan of S. breviflora > S. grandis > S. krylovii grasslands. Root lifespan across the three types of grasslands displayed a similar temporal pattern, such that root lifespan followed the order of autumn-born roots > summer-born roots > spring-born roots. The spatial and temporal differences in root lifespan across the three types of grasslands were mainly related to contents of soluble sugars in roots of the dominant species and BNPP/ANPP ratio of the communities. The differences in root lifespan across the major types of grasslands and different seasons highlight the potential importance of taking these differences into account in models of future carbon cycling and climate change.