Undercutting conifer seedlings: effect on morphology and field performance on droughty sites

Abstract

Bareroot 2-0 Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and ponderosa pine (Pinusponderosa Dougl. ex Laws.) seedlings were subjected to five undercutting treatments, which varied by number and depth of undercut and seedling phenology at time of treatment, so that morphological characteristics at lifting and field performance 4 years after planting on droughty south slopes in southwest Oregon could be evaluated. All undercutting treatments significantly reduced seedling top growth, but changes in root system morphology depended upon treatment severity and species. Treatment effects were generally more pronounced in ponderosa pine than Douglas-fir. Multivariate analysis of variance showed significant treatment effects for both species based on seedling morphology at lifting, but discriminant analyses revealed that these differences existed primarily between undercut seedlings, regardless of undercutting treatment, and controls. In Douglas-fir this separation was largely due to differences in seedling height and in ponderosa pine it was due to differences in tap root biomass. However, no treatment effects were detectable 4 years after outplanting for either species despite record high air temperatures during the first growing season, suggesting that morphological differences at lifting were probably not of sufficient magnitude to affect field performance.

Is it possible to manipulate root anchorage in young trees?

“…However, after 7 years growth, little disparity in mean growth variables exist between the two populations of seedlings, although small differences, possibly due to root system asymmetry, still affect the relationships between F/CSA and plant growth traits. However, after several more years' growth, it is unlikely that these differences will still be noticeable (Hobbs et al 1987;Nö rr 2003).…”

Efecto de distintos regímenes de manejo radicular en el crecimiento de plantas de raulí (Nothofagus alpina (Poepp. et Endl) Oerst.) 1-0 a raíz desnuda

“…Por otra parte, la variable peso seco de raíces gruesas aunque logró diferencias altamente signi ficativas entre los distintos esquemas de manejo radicular (cuadro 3 y figura 5), éstas se produjeron esencialmente entre los tratamientos con acondi cionamiento radicular, lo que evidencia que la poda radicular inicial tiene un m í n i m o efecto en la pér dida de raíces gruesas, lo que coincide con la lite ratura (Hobbs et al, 1986), y reafirma la m a y o r relevancia en la producción de raíces finas del le vantamiento y aireación producto de los descal ces, los cuales son tratamientos m u c h o m á s seve ros que la poda (Daniels y Simpson, 1990). Esto, además, explicaría el cambio en la estructura y conformación del sistema radicular entre plantas con manejo y sin él.…”

Root wrenching and lifting date of slash pine: Effects on morphology, survival, and growth

“…ex Laws. ), radiata, and caribbean (Rook 1971;Bacon and Hawkins 1977;Hobbs et al 1987). These conifers all characteristically develop a prominent tap root as does slash pine, and with repeated severance a compact fibrous root system is formed.…”

“…These conifers all characteristically develop a prominent tap root as does slash pine, and with repeated severance a compact fibrous root system is formed. The lack of response by Douglas-fir to root wrenching has been attributed to its naturally fibrous root system and absence of a dominant taproot (Duryea and Lavender 1982;Hobbs et al 1987). …”

“…) Franco), results are less conclusive. Many studies found some morphological changes (Duryea and Lavender 1982) (Hobbs et al 1987), but Tanaka et al (1976) and van den Driessche (1983) found that those morphological differences resulted in better survival and an extension of the fall planting period.…”