Soil C/N influences carbon flux and partitioning in control and fertilized mini-plots of Pinus radiata in New Zealand

Abstract

Patterns of carbon flux and partitioning were examined in highly stocked (40,000 stems ha-1) control and fertilized mini-plots of Pinus radiata D. Don at five sites, which covered a wide climatic and edaphic gradient on the South Island of New Zealand. The gross-primary productivity (GPP) and the partitioning of the GPP to the above- and below-ground productivity and respiration were determined using a carbon budget approach. All of the components of the GPP, the above-ground net primary productivity (ANPP [r2 = 0.67, P ≤ 0.01]), above-ground plant respiration (APR [r2 = 0.66, P ≤ 0.01]), and total belowground carbon flux (TBCF [r2 = 0.41, P ≤ 0.01]) significantly increased with the GPP, but the ANPP:GPP, APR:GPP and TBCF:GPP ratios were not significantly correlated to the GPP (P > 0.41). The TBCF:GPP ratio significantly increased with the soil C:N ratio (r2 = 0.93, P ≤ 0.01), with a concomitant decrease in the APR:GPP ratio (r2 = -0.88, P ≤ 0.001) without a significant effect on the ANPP:GPP ratio (P > 0.32). None of these fractions were correlated to the soil total or extractable phosphorus (P > 0.32). Although periodic and intensive measurements were required to determine the whole carbon budget in the ten plots, by necessity, the number of sites was limited, and, therefore, our results would require further confirmation using whole carbon budgets from a wider range of soil and environmental conditions