Calcifuge and soil-indifferent Proteaceae from south-western Australia: novel strategies in a calcareous habitat

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Background and aimsProteaceae are a prominent plant family in south-western Australia. Most Proteaceae are 'calcifuge', occurring exclusively on old phosphorus (P)-impoverished acidic soils, with a few 'soil-indifferent' species also found on young P-richer calcareous soils. Calcium (Ca)-enhanced P toxicity explains the calcifuge habit of Proteaceae. However, previous research has so far been focused exclusively on the roles of Ca and P in determining Proteaceae distribution, and consequently there is little knowledge on how other soil-based strategies influence this distribution. We aimed to study the effects of young calcareous soils on four soil-grown Proteaceae and assess differences between calcifuge and soil-indifferent Proteaceae to better understand their natural distribution.MethodsTwo calcifuge and two soil-indifferent Proteaceae from south-western Australia were grown in six contrasting soils, including young calcareous, and old acidic soils.ResultsWhen grown in calcareous soils all species showed root growth inhibition, micronutrient deficiency, Ca-enhanced P toxicity, and negative impacts on physiology. Calcifuge species were more sensitive to calcareous soils than soil-indifferent ones, although this varied between genera. Soil-indifferent species tended to produce more cluster roots, release more carboxylates per root mass, and allocate less Ca to their leaves, compared with calcifuges; they also had smaller seeds and were less sensitive to Ca-enhanced P toxicity.ConclusionWe surmise that a combination of these traits allows soil-indifferent species to tolerate calcareous soils. This study provides insight into how Proteaceae respond to young calcareous soils and how this influences their distribution.
Original languageEnglish
Number of pages28
JournalPlant and Soil
Publication statusE-pub ahead of print - 30 Sept 2023

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