Relationships of soil phosphorus status to wood anatomical traits and to nutrient translocation in woody plants

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A variety of adaptation strategies have enabled vascular plants to survive and prosper in nearly all ecosystems on the globe. Besides facing scarcity in water and light supply, woody plants often have to overcome nutrient limitations to sustain photosynthesis and growth. Of all essential macro nutrients for plant metabolism one of the least available in the soil is phosphorus (P). Due to the low P availability plants have to either optimize their nutrient acquisition and/or reduce nutrient losses. Several functional traits have already been identified as adaptation strategies such as effective nutrient resorption from senescent leaves and increased leaf longevity. However, research on nutrient translocation in stem wood and particularly twigs and associated anatomical features remain scarce. Moreover, adaptive trade-offs as well as the control of P cycling by systemic and environmental factors are still not well understood and the integration of plant-internal P storage and mobilization in the whole-plant nutrient budget is lacking so far.In the present proposal I want to link selected plant functional traits of leaf, stem and roots with nutrient translocation patterns, growth performance and whole-plant nutrient status in tree species growing on soils with contrasting P contents. The research will be conducted at Macquarie University in Sydney, Australia, joining the research groups of Prof. Mark Westoby and Prof. Ian Wright who have profound experience in the field of plant functional traits. The focus of the proposal is to disentangle the effects of low soil P on wood anatomical traits and in particular on wood parenchymatic tissue (i.e. living cells responsible for storage) as well as to understand strategies of woody plants with respect to phosphorus translocation. To achieve this aim the investigation of functional traits in plant communities in growing on P-poor as compared to P-rich soils will be conducted. Additionally, a selection of the occurring species will be cultivated as seedlings in a P availability gradient established in a common garden experiment. The nutrient content of living and freshly senescent tissues such as leaves, twigs, stem wood, bark and roots will be analyzed and related to nutrient relocation. To explore the importance of nutrient translocation for the whole-tree budget the annual production of leaf litter, fine roots and stem growth will be investigated. Wood anatomical analyzes will focus on the relationship between parenchyma fraction and phosphorus and other nutrient content in the wood of different species and the potentially plastic response of wood tissue composition following increased P supply.I am convinced that the opportunities provided by the present proposal will not only contribute to a deeper scientific knowledge of the complex traits associated with phosphorus use, but will also let me acquire the necessary expertise, methodology and knowledge to become a future scientific leader.