Serpentine and nonserpentine Achillea millefolium accessions differ
in serpentine substrate tolerance and response to organic and inorganic
amendments
Ryan E. O’Dell
1
& Victor P. Claassen
Department of Land, Air, and Water Resources, University of California, One Shields Avenue, Davis, CA,
95616-8627, USA.
1
Corresponding author*
Received 10 February 2005. Accepted in revised form 26 July 2005
Key words: calcium, compost, edaphic ecotype, heavy metals, macronutrients, magnesium, revegetation,
serpentine, ultramafic
Abstract
Subgrade serpentine substrates are exceptionally difficult to revegetate due to multiple limitations including
low N, P, and K, low Ca:Mg molar ratios, high levels of heavy metals including Ni, Cr, and Co, low organic
matter, low CEC, and low water holding capacity. To examine the influence of plant origin on the success
of the revegetation of serpentine substrates, granite and serpentine accessions of Achillea millefolium were
grown on subgrade serpentine substrate amended with yard waste compost, slow-release NPK fertilizer,
and/or CaSO
4
Æ 2H
2
O (gypsum). The goals of this study were to: (1) identify the substrate amendment
combination that maximized establishment of A. millefolium on serpentine substrate, (2) compare seedling
establishment, survival, and growth of the serpentine and granite A. millefolium accessions in order to
determine if a serpentine edaphic ecotype of A. millefolium exists and if this ecotype is superior to the
granite accession for the establishment of vegetation on serpentine substrate and (3) if a serpentine edaphic
ecotype of A. millefolium does exist, what physiological features with respect to mineral nutrition convey a
higher tolerance of serpentine for this ecotype than the nonserpentine ecotype. Seedling establishment,
survival, and growth were greatest for A. millefolium when the subgrade serpentine substrate was amended
with 30% (v/v) compost and 220 mg kg substrate
)1
each of N, P, and K. The serpentine A. millefolium
accession displayed a greater tolerance of the subgrade serpentine substrate, serpentine topsoil, and the
amended subgrade serpentine substrate than the granite accession. Higher capacity of the serpentine
A. millefolium accession for selective Ca translocation from roots to the shoot resulted in a significantly
higher shoot Ca:Mg molar ratio than the granite accession and appeared to be the most important
physiological feature conveying greater tolerance of the serpentine accession for serpentine substrates.
Introduction
Serpentine substrates occupy ~2860 km
2
(1%) of
the land area of California, USA (Kruckeberg,
2002). Serpentine substrates are stressful environ-
ments for plant growth due to multiple limita-
tions including deficiency of N, P, and K, low
Ca:Mg molar ratios, potentially high levels of
phytotoxic heavy metals including Ni, Cr, and
Co, low organic matter, low CEC, and low water
holding capacity. Low levels of N, P, and K in
serpentine soils are generally attributed to slow
nutrient biocycling (Burt et al., 2001). The excep-
tionally low Ca:Mg molar ratio and high heavy
metal content of serpentine soils is inherited from
the magnesic and heavy-metal rich mineralogy of
serpentine parent materials (Burt et al., 2001;
* FAX No: +530-752-1552.
E-mail: reodell@ucdavis.edu
Plant and Soil (2006) 279:253–269 Ó Springer 2006
DOI 10.1007/s11104-005-2360-y