Soil CO₂evolution 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 (Sff) and without (Sms) 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 Sff 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 Sff was significantly greater in unfertilized relative to the fertilized stands; however, there was no difference in average Sms among treatments. Soil temperature and the mass of the forest floor (litter) explained most of the difference in Sff among treatments. Soil temperature and volumetric water content accounted for 70% of the seasonal variation in Sff. Annual carbon efflux from the soil averaged 14.1 Mg·ha-1 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.

Biotic and abiotic factors controlling the spatial and temporal variation of soil respiration in an agricultural ecosystem

“…Correlation analysis revealed that fine root biomass in soil collars was significantly related to soil respiration rates across a single site at one measurement moment (Table 1), indicating soil respiration differed in plots with greater and less root biomass under the same environmental conditions, which were similar to previous reports (Maier and Kress, 2000;Pangle and Seiler, 2002;Wiseman and Seiler, 2004;Jia et al, 2005). Fig.…”

Soil aggregate fraction-based 14C analysis and its application in the study of soil organic carbon turnover under forests of different ages

“…However, the above estimated soil CO 2 flux only includes that produced by oxidative decomposition of soil organic matter, and we need to consider the contributions from root respiration [111]. Although it is difficult to assess the relative contributions of root autotrophic respiration and microbial heterotrophic respiration to soil CO 2 flux, approximately 30%-70% of soil CO 2 flux are produced by root respiration [103,[112][113][114]. We assumed the intermediate value 50% as the average contribution of soil respiration and calculated the soil CO 2 flux in different plots.…”

Influence of Tillage Practices and Crop Type on Soil CO2 Emissions

“…In view of the heavy demands for agricultural production to meet the needs of the growing population, the role of agricultural practices and their impact on soil, climate, gaseous emission, water resources, biodiversity and others must be considered more now than in the past [1]. The soil as a potential sink for carbon can be a key factor in addressing climate change; it is the second-largest carbon reservoir, and contains twice as much carbon in relation to the atmosphere [2,3], three times more carbon compared to vegetation [4] and is also an important sink of atmospheric CO 2 [5]. The reduction of CO 2 emissions by soil carbon sequestration is of primary importance, as agricultural and forestry practices could remove atmospheric carbon by sequestration and thus mitigate climate change by maintaining and/or increasing the amount of carbon stored in the soil and plant material [6].…”