Diel patterns of fine root respiration in a dryland shrub, measured in situ over different phenological stages

Abstract

Fine root (<2 mm) respiration (Rfr) may play an important role in carbon cycles in drylands; thus Rfr in desert ecosystems may have important implications for belowground processes and global carbon cycles. This study aimed to (1) investigate the diel and seasonal changes in Rfr of a shrub (Caragana microphylla Lam.) in situ during the growing season and to (2) detect the relationship between both photosynthesis and phenology and Rfr. The study was conducted in an even-aged C. microphylla plantation in a semiarid area in the Mu Us Desert of China. Rates of Rfr and net photosynthesis were measured using a standard chamber equipped with a portable gas analysis system. The data revealed two diel patterns that varied with different phenological stages. Diurnal Rfr rates were 2.2-fold greater than nocturnal Rfr rates. Our results showed that diurnal changes in Rfr strongly correlated with rates of net photosynthesis, suggesting that the diel changes were strongly associated with the current supply of photosynthates. Furthermore, aboveground phenology could partially explain some of the variations in seasonal Rfr. Our results provide basic information on the link between Rfr and aboveground activities, and enhance our understanding of carbon processes in dryland ecosystems.