The influence of stocking levels, clone, fertilization, and weed control on surface CO.sub.2 efflux in a mid-rotation Pinus radiata D. Don plantation in Canterbury, New Zealand

• Published in: Journal of forestry research Vol. 32; no. 6; p. 2567
• Main Authors: KC, Mohan, Mason, Euan G, Bown, Horacio E
• Format: Journal Article
• Language: English
• Published: Springer 01.12.2021
• Subjects: Analysis; Climatic changes; Cloning; Plantations
• ISSN: 1007-662X; 1993-0607
• DOI: 10.1007/s11676-021-01298-9

Silvicultural practices applied in managed forest plantations may help counteract the effects of climate change by influencing soil surface CO.sub.2 efflux (F.sub.s). Understanding the effects of silvicultural practices on F.sub.s will provide unbiased estimates of carbon fluxes and allow better silvicultural decisions for carbon sequestration. Therefore, we assessed how F.sub.s differed seasonally across silvicultural practices (i.e., stocking levels, clone, fertilization and weed control treatments) and evaluated the effects of soil temperature (T.sub.s) and soil volumetric water content ([theta].sub.v) on F.sub.s across these practices for a mid-rotation (14 year-old) Pinus radiata plantation in the Canterbury region of New Zealand. There were significant differences in F.sub.s (p < 0.05) over the four seasons, three levels of stocking, and five clones. The effects of fertilization and weed control applied 12 years previously on F.sub.s were insignificant. Annual estimate of F.sub.s (mean ± 1 standard deviation) from the study site was 22.7 ± 7.1 t ha.sup.-1 a.sup.-1 in the form of CO.sub.2 (6.2 ± 2.1 t ha.sup.-1 a.sup.-1 in the form of C). F.sub.s values were consistently higher in plots with 1250 stems ha.sup.-1 compared to 2500 stems ha.sup.-1, which may be related to a strong soil resource limitation because of the close spacing in the latter plantation. Significant differences in F.sub.s across clones suggest that variations in carbon partitioning might explain their growth performance. Silvicultural treatments influenced F.sub.s response to soil temperature (p < 0.05), resulting in models explaining 28-49% of the total variance in F.sub.s. These findings provide insights into how silvicultural management decisions may impact F.sub.s in mid-rotation radiata pine plantations, contributing towards developing more precise and unbiased plantation carbon budgets.