Mangrove leaf potassium as a tracer of root metabolism

Belowground dynamics of rooted plants like mangroves are difficult to observe directly but elements like potassium (K) in leaves can trace root connections. A literature review of mangrove studies from the Pacific and the Americas explored these connections. While leaf K concentrations are generally maintained for osmotic homeostasis, they were hypothesized to also balance sucrose fluxes to roots. Sucrose-based root foraging and desalination could be discerned from the leaf K measurements, as well as plant sipping of soil water for evapotranspiration. The balance between belowground vs aboveground dynamics showed important contrasts between mangrove species and sites, with higher evapotranspiration and aboveground growth at high rainfall sites. Novel leaf salinity measurements, partly based on K, showed that groundwater supplies 20-35% of mangrove water demand across sites. Overall, the K-based results are part of a general elementomics approach involving elements and their isotopes, a spatial biogeochemical approach that helps understand mangrove forests for conservation and management in catchments.

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Professor Brian Fry is the author of the book "Stable Isotope Ecology", which can be downloaded free of charge HERE