“Multiple trait dimensions mediate stress gradient effects on plant biomass allocation, with implications for coastal ecosystem services” by De Battisti et al. is a new research article published in Journal of Ecology.

In this blog post, author Davide De Battisti summarises the recent advances in understanding how coastal plants respond to stress.

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Salt marshes are highly appreciated ecosystems for the numerous services they provide to humans: from their key capacity to protect the coast from storm surge, to their high carbon sequestration ability, and their beauty (Figure 1) which has also been inspiration for artists. My PhD at Swansea University was part of the wider Resilcoast project (http://www.nrn-lcee.ac.uk/resilcoast/). One of our key goals was to better understand the contexts under which marshes provide effective coastal protection. My work adopted the plant trait approach because of its ability to mechanistically link changes in the environment with ecosystem functions – including, potentially, coastal protection. In trait ecology, changes in the soil nutrients induce a shift in plant traits along a resource acquisition-conservation dimension, the plant economic spectrum. This economic spectrum provides a starting point for understanding how changes in abiotic factors could potentially influence ecosystem functions and services in vegetated coastal ecosystem.

Working on salt marshes, where intertidal plants grow across multiple stress gradients, raised a question: do salt marsh plants respond by simply shifting along the plant economic spectrum, or do they cope through different strategies? In other words, can we use the mono-dimensional plant economic spectrum to capture the effect of multiple abiotic stressors on ecosystem functions, or do we need to look for multiple trait (strategy) dimensions (Figure 2)?

To tackle this question we decided to focus on the widespread common cordgrass, Spartina anglica. This species occupies lower regions of the saltmarsh platform where its above- and belowground biomass respectively dissipate waves and stabilise the sediment – two processes that help protect our coasts when storms arrive. We sampled both above- and belowground traits and biomass along several Welsh estuaries, incorporating gradients in sediment salinity, redox, and nutrient availability.

Far from complying to the plant economic spectrum, Spartina’s traits were influenced by sediment salinity and redox (not nutrient availability) and spread along not one – but four – dimensions. High salinity induced plants towards a conservative strategy; in turn, these plants invested more in belowground biomass. Meanwhile, high sediment redox allowed plants to invest more in coarse roots, consequently investing more in aboveground biomass. These multiple strategies have implications for the maintenance of ecosystem services across saltmarsh landscapes: where plants experience high salinity, their investment in belowground biomass will strengthen sediment stability and, where this coincides with high sediment redox, plants can still sustain aboveground investment and therefore wave energy dissipation (Figure 3).

Our study highlights a crucial point: a single dimensional economic spectrum cannot fully capture how plants mediate the effect of several abiotic stressors on ecosystem functions. Instead, we need to consider plant adaptations to multiple stressors, i.e. multiple traits dimensions, to fully elucidate how changes in the abiotic environment influences ecosystem functions and services.

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Davide De Battisti Swansea University, UK