Growth response of ponderosa pine to intensive cultural treatments varies with site quality and plantation age

Abstract

Long-term forest experiments provide valuable knowledge in managing forests for productivity and other ecosystem services. California’s “Garden of Eden” experiment was established to determine growth potential of Pinus ponderosaplantations in response to intensive cultural treatments. We examined the 20-year growth-response of tree volume to intensive cultural treatments consisting of combinations of herbicide on competing vegetation (H), fertilization (F), and insecticide (I). We found that both H and F treatments synergistically increased tree growth at intermediate and lower-quality sites. Growth increased by 1.5–2.1 times with F, 2.1–2.5 times with H, and 2.3–3.8 times with HF treatments versus control (range = 39.3–109.2 m³ha⁻¹). Across the highest productive site, H and F effects on volume seemed additive at younger ages, but largely dissipated by age 20, with volume increasing by 1.6, 1.2, and 1.6 times relative to control in F, H, and HF treatments, respectively. However, 20-year mean annual increment was 21.7 m³ha⁻¹yr⁻¹for the F treatment, the highest volume reported for ponderosa pine in California. The results underscore how site-specific cultural treatments, especially H and F, may widely enhance plantation productivity and boost stand development.

Citation

Zhang, Jianwei; Finley, Kaelyn A; Young, David H; Fiddler, Gary O; Looney, Christopher. 2022. Growth response of ponderosa pine to intensive cultural treatments varies with site quality and plantation age. Forest Science. 68(2): 212-225. https://doi.org/10.1093/forsci/fxab065.