Abstract:Global warming is expected to have profound effects on plant growth. The effects of global climate change on the aboveground parts of plants have been reported in many studies in the past decades. However, limited information regarding how warming affects belowground ecological processes, especially root dynamics, has restricted our ability to predict how roots will respond to increasing temperatures. Changes in ecophysiological properties of fine roots under climate change may play an important part in the growth performance of tree plantations. The aim of the present study was to explore the belowground responses and adaptability of the most important timber species in southern China, the Chinese fir (Cunninghamia lanceolata) to global warming. A field soil cable warming experiment was conducted in Chenda State-Own Forest Farm, Sanming, Fujian Province. The experiment included two treatments:soil warming (+5℃) and no-warming (control), and each treatment had 5 replicate plots. We measured changes in fine root biomass, morphology (specific root length and specific root surface area), stoichiometry (C, N, P) and metabolisme (including root respiration and nonstructural carbohydrates (NSCs)) after approximately one year of soil warming using soil coring and ingrowth core methods. Soil core diameters were 3.5 cm and were divided into 0-10, 10-20, 20-40, and 40-60 cm. Ingrowth core diameters were 20 cm and were divided into 0-10 and 10-20 cm. A two-way ANOVA showed that treatment×diameter class significantly effected the fine root biomass, C and N concentrations, and C/N ratio, whereas it had no effect on the fine root morphology, P concentration, C/P ratio, and metabolism. The one-way ANOVA showed that (1) campared with the control plots, the 0-1 mm fine root biomass increased significantly, whereas the 1-2 mm fine root biomass and fine root morphology did not change in warmed soil plots. These findings indicated that the root system adjusted the fine root biomass, especially the 0-1 mm whereas the fine root morphology responded to nutrient availability; (2) the fine root N concentration increased significantly, but the fine root P concentration showed no change; the fine root C/N decreased significantly, whereas the fine root N/P had increased significantly in warmed soil plots. Collectively, these findings demonstrated that soil warming caused nutritional imbalances, and the growth of Chinese fir seedlings was limited by P avalibility by analyzing the N/P ratio; (3) the fine root respiration did not acclimate to soil warming and the fine root NSCs decreased significantly in warmed soil plots. Soil warming caused a metabolic imbalance, which increased the fine root mortality and shortened the fine root lifespan; thus, could have an effect on nutrient and moisture absorption of the Chinese fir. It can be concluded that soil warming changed the fine root biomass allocation and caused nutritional and metabolic imbalances, which could play important roles in the growth of Chinese fir under global warming.