Tolerance of young seedlings of different tree species and a cereal to poor soil aeration

Abstract

Poor soil aeration restricts the establishment of plants, yet some species used in revegetation programs are more tolerant of waterlogging than others. This study evaluated the sensitivity to poor soil aeration of young seedlings of Acacia salicina, Eucalyptus camaldulensis, E. leucoxylon, and E. kochii. A reference cereal crop, barley (Hordeum vulgare var. Keel), was also included. Seedlings were grown for 21 days in a loamy sand under a range of controlled volumetric air contents of the soil (εair, 0.000–0.200 m3 m–3), then the diameter and total length of roots, plus the dry masses of shoots and roots, were measured, and water use and water-use efficiency (WUE) calculated. All plant species had some sensitivity to poor soil aeration but their tolerance varied widely. Seedlings of E. camaldulensis were highly tolerant of waterlogging, whereas seedlings of E. kochii were highly sensitive. Seedlings of barley and A. salicina showed moderate tolerance and had significantly greater WUE than any of the eucalypts. Among the more sensitive species, no single aeration state caused a consistent reduction in all plant parameters; some species responded to any restriction in aeration by reducing WUE; others showed declining WUE only when aeration fell below 0.15 m3 m–3. No single early-growth parameter adequately described a species’ sensitivity to waterlogging; some were simple (e.g. shoot mass) and others more integrated (e.g. WUE). Differences in growth rate and water use by the different species under low εair suggest that land managers and revegetation agencies have scope to select superior species for improving the establishment of trees on waterlogged soils. Furthermore, the wide variation in tolerance to poor soil aeration among the tree seedlings compared with barley suggests considerable scope for genetic improvement of cereals by using material from native trees.