Vertical distribution of organic amendment influences the rooting depth of revegetation species on barren, subgrade serpentine substrate

Abstract

Barren, subgrade serpentine substrates are difficult to revegetate due to N, P, and K deficiencies, low Ca:Mg molar ratios, potentially high levels of heavy metals including Ni, Cr, and Co, low organic matter, low CEC, and poor water holding capacity. Several large, bare roadcuts exist in the North Coast Ranges along the west coast of California, USA. Substrate was collected from a large roadcut that has remained barren for more than a decade despite conventional surface amendment with NPK fertilizer and seeding with a mix including nonserpentine grasses and herbs. Although serpentine plant communities have been studied globally in great detail, very little information exists on how to effectively restore these communities after drastic disturbance (removal of topsoil and loss of biological activity). This rhizotron study examined how surface layering and mixing yard waste compost into serpentine substrate affected biomass production, rooting distribution, and tolerance of native, as well as invasive grass species that grow on serpentine. Roots of less serpentine-tolerant species became necrotic upon contact with the serpentine substrate in the layered compost application treatment. The roots of highly serpentine-tolerant species, however, displayed a superior tolerance to the serpentine substrate and were able to grow through its entire depth. Mixing the compost into the serpentine substrate significantly improved the Ca content of the growing medium, allowing the less serpentine-tolerant species to root through the entire depth. Although the compost surface layer treatment promoted growth of the highly serpentine-tolerant species in the serpentine substrate, mixing the compost amendment into the substrate would also permit additional desirable revegetation species to become established.

Comparison of revegetation techniques on mineral clay soil: analysis of quantitative response of vegetation cover

“…These findings match the results gained from corresponding tests performed both in short (Heereman et al, 2001;Beauchamp et al, 2006;Claassen and Carey, 2006;Grigg et al, 2006;O'Dell and Claassen, 2006;Curtis and Claassen, 2009) and medium periods (Roberts et al, 1988).…”

Plant performance in living wall systems in the Scandinavian climate

“…Both species also provided generous amounts of flowers during long periods of the growing season. Ami has a wide ecological niche in terms of water availability (Ellenberg 1974) and the roots of Ami are known to stretch deep down in a soil with low availability of water and nutrients (O'Dell and Claassen, 2006). However, they are restricted from doing so in the RS, which could have a negative effect on the quality.…”

Factors controlling germination and seedling growth of an endangered Saussurea species (Asteraceae) endemic to serpentine areas in Japan

“…Plants adapted to growing on serpentine typically exhibit specific physiological adaptations to regulate Ca and Mg uptake at the root level and translocation to the shoot. These physiological adaptations include selective Ca uptake, Ca deficiency tolerance, Mg exclusion, and/or Mg toxicity tolerance (O'Dell & Claassen, 2006). In our pot culture experiments, the shoot weights of S. ochiaiana seedlings were significantly larger in the low (0.6 and 0.3) Ca:Mg molar ratio treatments than in the high (15 and 1.5) Ca:Mg molar ratio treatments, suggesting that this species can grow under Ca‐deficient conditions.…”