Strategies to acquire and use phosphorus in phosphorus-impoverished and fire-prone environments

Abstract

Background Unveiling the diversity of plant strategies to acquire and use phosphorus (P) is crucial to understand factors promoting their coexistence in hyperdiverse P-impoverished communities within fire-prone landscapes such as in cerrado (South America), fynbos (South Africa) and kwongan (Australia). Scope We explore the diversity of P-acquisition strategies, highlighting one that has received little attention: acquisition of P following fires that temporarily enrich soil with P. This strategy is expressed by fire ephemerals as well as fast-resprouting perennial shrubs. A plant’s leaf manganese concentration ([Mn]) provides significant clues on P-acquisition strategies. High leaf [Mn] indicates carboxylate-releasing P-acquisition strategies, but other exudates may play the same role as carboxylates in P acquisition. Intermediate leaf [Mn] suggests facilitation of P acquisition by P-mobilising neighbours, through release of carboxylates or functionally similar compounds. Very low leaf [Mn] indicates that carboxylates play no immediate role in P acquisition. Release of phosphatases also represents a P-mining strategy, mobilising organic P. Some species may express multiple strategies, depending on time since germination or since fire, or on position in the landscape. In severely P-impoverished landscapes, photosynthetic P-use efficiency converges among species. Efficient species exhibit rapid rates of photosynthesis at low leaf P concentrations. A high P-remobilisation efficiency from senescing organs is another way to use P efficiently, as is extended longevity of plant organs. Conclusions Many P-acquisition strategies coexist in P-impoverished landscapes, but P-use strategies tend to converge. Common strategies of which we know little are those expressed by ephemeral or perennial species that are the first to respond after a fire. We surmise that carboxylate-releasing P-mobilising strategies are far more widespread than envisaged so far, and likely expressed by species that accumulate metals, exemplified by Mn, metalloids, such as selenium, fluorine, in the form of fluoroacetate, or silicon. Some carboxylate-releasing strategies are likely important to consider when restoring sites in biodiverse regions as well as in cropping systems on P-impoverished or strongly P-sorbing soils, because some species may only be able to establish themselves next to neighbours that mobilise P.

A cool spot in a biodiversity hotspot: why do tall Eucalyptus forests in Southwest Australia exhibit low diversity?

“…At the other extreme were X. gracilis, X. preissii (our negative references) and M. riedlei, which grow very slowly between fires, but are among the first to resprout after a fire (Grove et al 1980). These species likely depend on elevated soil P concentrations after a major disturbance such as fire (Lambers et al 2022). In between the two extremes, some species released significant amounts of carboxylates, in accordance with their relatively high leaf [Mn].…”

Scientific impact, direction and highlights of Plant and Soil in the 30 years since Professor Hans Lambers became Editor in Chief

“…The approach has been used in ecosystems across the world, not least in China (Tian et al 2021;Yu et al 2020;Zhou et al 2021). In a review in the forthcoming Special Issue, Hans continues to use this approach to provide insight on plant phosphorus-acquisition strategies in a broad context (Lambers et al 2022). While the importance of carboxylates in the rhizosphere for improving inorganic phosphorus availability has been known for many years, innovative work has shown its importance in the availability of a range of other nutrients and beneficial elements including Mn and Si (de Tombeur et al 2021;Lambers 2022) and this is further explored in the review by Lambers et al (2022) in this special issue.…”

A novel proxy to examine interspecific phosphorus facilitation between plant species

“…When soil P availability is very low, facilitated plants may not show increased leaf [P], and hence having a proxy is very useful, especially in field observations where increased productivity may be hard to measure (Shen et al, 2023). Therefore, leaf [Mn] can be used as an easilymeasurable proxy that reflects the mobilization of sorbed soil P for a given species (Pang et al, 2018;Wen et al, 2021) or a range of species (Lambers et al, 2015(Lambers et al, , 2021(Lambers et al, , 2022Lambers, 2022).…”