Soil CO₂ evolution and root respiration in 11 year-old Loblolly Pine (Pinus taeda) Plantations as Affected by Moisture and Nutrient Availability

Abstract

We measured soil CO₂ evolution rates with (S_ff) and without (S_ms) the forest floor litter and root respiration monthly in 11-year-old loblolly pine (Pinus taeda L.) plantations during the fourth year of fertilization and irrigation treatments. Values of S_ff ranged from less than 1 µmol·m^-2·s^-1 during the winter to greater than 5 µmol·m^-2·s^-1 in late spring. Average S_ff was significantly greater in unfertilized relative to the fertilized stands; however, there was no difference in average S_ms among treatments. Soil temperature and the mass of the forest floor (litter) explained most of the difference in S_ms among treatments. Soil temperature and volumetric water content accounted for 70% of the seasonal variation in S_ff. Annual carbon efflux from the soil averaged 14.1 Mg per year for all treatments. Most of the evolved carbon was derived from root respiration (50-73%). Net ecosystem productivity was -1.1 and 6.9 Mg C·ha^-1 per year for the unfertilized and fertilized stands, respectively. At age 11, the unfertilized stands were functioning as a net carbon source, while fertilized stands were a strong carbon sink. It was concluded that fertilization could decrease the time for a young pine plantation to change from a carbon source to a carbon sink.

Citation

Maier, Chris A.; Kress, L.W. 2000. Soil CO₂ evolution and root respiration in 11 year-old Loblolly Pine (Pinus taeda) Plantations as Affected by Moisture and Nutrient Availability. Can. J. For. Res. 30: 347-359 (2000)