Abstract:

This research examined monthly dynamics of soil respiration and their relationships with soil temperature at 5 cm depth (using Lci Portable Photosynthesis System (SRS-1000)) and seasonal variations of fine root (<2 mm) biomass in 0～50 cm depth (soil core method) in an age series (1～6-year-old) of Eucalyptus grandis. The results showed that monthly (early month) soil respiration rate (SRR) ranged from 0.35 to 1.71 μmol·m^-2 s^-1, and the seasonal values were different as following descending sequence: summer (1.55), autumn (1.16), spring (0.62), winter (0.41 μmol·m^-2 s^-1) (P<0.01), and in different ages showed that 6-year-old (1.10)>5(0.99)>2(0.93)>1 (0.82)>3(0.80)>4(0.67 μmol·m^-2 s^-1) (P<0.01). The relationship between early monthly dynamics of SRR and soil temperature at 5 cm depth was significant (R²=0.706 3～0.965 7, P<0.05). The exponential equation of R_s=a·e^(b·T) and Q₁₀=e^{10b were applied to search the relationships of monthly soil temperature at 5 cm depth and SRR, and the temperature sensitivity (Q₁₀) was from 1.73 to 2.29. The binary linear regression between soil temperature at 5 cm depth, fine root (<2 mm) biomass in 0～50 cm depth and SRR is significant (P<0.01).}

Key words: Eucalyptus grandis, soil respiration rate (SRR), temperature, fine root biomass, age sequence