Effects of root diameter, branch order, root depth, season and warming on root longevity in an alpine meadow

Abstract

AbstractFine root is of importance in biogeochemical cycles especially in terrestrial ecosystems. The lack of understanding of the factors controlling root lifespan has made accurate prediction of carbon flow and nutrient cycling difficult. A controlled warming experiment was performed in an alpine meadow on the northern Tibetan Plateau (near Nagchu Town). We used a minirhizotron technique to measure root dynamics in situ during the growing season of 2013 and 2014 and survival analyses to assess root lifespan and the effects of root diameter, branch order, birth season, root depth and warming on root lifespan. Root diameter, branch order and root depth were all positively correlated with root lifespan. With an increase in diameter of 0.1 mm, mortality hazard ratio of roots declined by 19.3 %. An increase in one level in branch order was associated with a decrease of 43.8 % in root death ratio. Compared with roots born in May–mid‐July, the mortality hazard ratio of roots born in late July–August and September–October reduced by 26.8 and 56.5 %, respectively. In warming treatments, roots tended to be thinner, less branched and deeper, and there was a higher proportion of roots born in spring compared to ambient conditions. Warming shortened the median root lifespan 44 days. However, in single warming condition, root diameter had no significant influence on root lifespan. Root diameter, branch order, root depth and season of birth were all factors affecting root lifespan in the alpine meadow; however, root branch order was dominant.