Root Architecture of Jarrah (Eucalyptus marginata) Trees in Relation to Post‐Mining Deep Ripping in Western Australia

Abstract

This research aimed to investigate coarse root systems of Jarrah (Eucalyptus marginata Donn ex Sm.) trees at a 13-year-old restored bauxite mine site in south-western Australia. Excavations in an area with small trees (lowquality site) revealed that deep ripping equipment failed to penetrate the cemented lateritic subsoil, restricting coarse roots (roots >5 mm in diameter) to the top 0.5 m of the soil profile, resulting in fewer (1,344 stems/ha) and smaller (mean height 4.5 m) Jarrah trees. An adjacent area within the same pit (high-quality site), with a stand density of 3,256 stems/ha and a mean height of 8.0 m, had a kaolinitic clay subsoil which coarse roots penetrated to the average ripping depth (1.5 m). Trees at the low-quality site did not penetrate the subsoil with their taproot, relying instead on a large number of lateral (5.3-8.0/tree) and sinker (12.0-16.5/tree) roots. Taproots of trees on crests at the high-quality site also did not penetrate the subsoil, and in contrast to trees at the low-quality site, they produced fewer lateral and sinker roots (2.3 and 2.0/tree, respectively). Taproots of trees in riplines at the highquality site directly penetrated the ripline and these trees also produced fewer lateral and sinker roots (5.0 and 3.7/ tree, respectively) than those at the low-quality site. Jarrah trees appear to have opportunistic root systems capable of responding to a variety of soil conditions encountered in the post-mining landscape.

The distribution of fine root length density for six artificial afforestation tree species in Loess Plateau of Northwest China

“…Accordingly, dry soil bulk density was related to root density, indicating physical impedance to root growth. This contrasts with previous studies on root architecture conducted on rehabilitated mine sites (Szota et al, 2007) and reconstructed profiles in mined Banksia woodlands (Rokich et al, 2001) close to the present study site, where high mechanical impedance and bulk densities restricted root growth and development due to underlying hardened iron-rich concretions (Rokich et al, 2001) and lateritic layers (Szota et al, 2007). Macinnis-Ng et al (2010) also reported that increasing bulk density increased mechanical resistance and reduced root extension.…”

“…Low dry soil bulk density values below 1.6 g cm -3 considered to be the upper threshold value for optimum root growth (Courtney & Timpson, 2005;Szota et al, 2007) was attributed to the coarse-textured and highly porous nature of the material (Gwenzi et al, 2011). Accordingly, dry soil bulk density was related to root density, indicating physical impedance to root growth.…”

“…Similarly, on a vertical gradient, the accumulation of litter on the surface soil promotes nutrient concentration and thus fine root accumulation in the upper layers of the soil (Courtney & Timpson, 2005). However, in coastal Pacific northwestern United States conifers (Szota et al, 2007) and hardwood and conifer stands in southeastern United States (Zhou & Shangguan, 2007), soil organic matter tend to limited root growth. The different patterns of root distribution observed in mineral and organic horizons may also be a response to varying levels of nutrient availability.…”

“…In addition to soil resource, bulk density, organic matter, particle size distribution and other soil characteristics possibly have an effect on plant growth and production in such regions (Janos et al, 2008). Courtney and Timpson (2005) and Szota et al (2007) reported that high soil bulk density and high clay content are thought to limit root growth. The accumulation of organic matter on the surface soil promotes nutrient concentration and thus fine roots accumulation in the upper layers of the soil (Scattolin et al, 2008).…”

Effet du stress hydrique sur l’architecture racinaire de jeunes plants <i>d’Acacia tortilis</i> (Forsk.), de <i>Balanites aegyptiaca</i> (L) Del., et de <i>Zizyphus mauritiana</i> Lam.

“…En milieu non contraignant, quelques racines assurent les besoins en eau de la plante. Par contre au champ, un système racinaire développé constitue un facteur de la productivité et de tolérance aux aléas climatiques (Szota et al, 2007). La connaissance des stratégies d'occupation du milieu tient compte de l'architecture racinaire des espèces.…”