STEM AND SOIL CO2 Efflux Responses Of Pinus radiata PLANTATIONS TO TEMPERATURE, SEASON, AGE, TIME (DAY/NIGHT) AND FERTILIZATION

Abstract

H.E. Bown, and M.S. Watt. 2016. Stem and soil CO 2 efflux responses of Pinus radiata plantations to temperature, season, age, time (day/night) and fertilization. Cien. Inv. Agr. 43(1):95-109. Stem CO 2 efflux is a highly variable component of the carbon budget of forest ecosystems. It reflects the balance between the CO 2 respired by the living stem tissues, less the CO 2 dissolved in the xylem sap moving upward in the transpiration stream, plus the CO 2 transported from the roots and released at the stem. Although knowledge about such fluxes at different spatial and temporal scales has markedly increased, knowledge of the effects of silviculture treatments, such as fertilization, on stem CO 2 effluxes are still limited, particularly when connecting above-and belowground processes. Using measurements obtained from twin plots (one control, one fertilized) installed in five-, 12-and 23-year-old stands of Pinus radiata, the objective of this study was to examine the influence of the temperature, stand age, fertilization, season and time of measurement (day/night) on the stem CO 2 efflux, soil CO 2 efflux and their ratio. There was a strong significant positive relationship between the stem CO 2 efflux and temperature. The slope between these two variables declined as the stand age increased and was higher for nighttime than daytime measurements. The stem CO 2 efflux was higher in the fertilized plots compared with the unfertilized (control) plots for the 5-and 12-but not the 23-year-old age classes. In contrast, the soil CO 2 efflux was largely unaffected by the temperature, time of measurement (day/night), fertilization and stand age; however, significantly higher values of soil CO 2 efflux were measured during spring than during the other seasons. Given the relative invariance of the soil CO 2 efflux to the temperature and treatment effects, the ratio of the stem:soil CO 2 effluxes was affected by the same factors as the stem CO 2 effluxes. These results suggest that fertilization would increase wood production and wood CO 2 efflux without changing the soil CO 2 efflux, thus most likely proportionally increasing aboveground C partitioning and decrease belowground C partitioning, with this effect being enhanced at younger ages.

The influence of stocking levels, clone, fertilization, and weed control on surface CO2 efflux in a mid-rotation Pinus radiata D. Don plantation in Canterbury, New Zealand

“…The third hypothesis for this study was that fertilization would not influence surface CO 2 efflux as it was carried out 12 years before the measurements. There were no significant effects of fertilization on surface CO 2 emissions in any season during the year which is consistent with research on radiata pine in Chile (Bown and Watt 2016), slash pine in Florida, USA (Shan et al 2001), and loblolly pine in Virginia (Tyree et al 2006) and North Carolina, USA (Maier and Kress 2000). Our study, however, contains only one-year data and the absence of inter-annual variability may prevent finding F s responses to fertilization (Tyree et al 2006).…”

Effect of thinning intensity on the stem CO2 efflux of Larix principis-rupprechtii Mayr

“…Consequently, there are significant differences in temperature under different TIs, thereby supporting the above point of view. E S and temperature are strongly positively correlated (Bown and Watt 2016;Darenova et al 2018;Salomón et al 2019). Therefore, temperature is one of the mechanisms by which thinning affects E S .…”