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1. The plant economic spectrum (PES) predicts a suite of correlated traits in a continuum from resource conservation to rapid resource acquisition. In addition to competing for resources, plants need to cope with other environmental stresses to persist and reproduce. Yet, it is unclear how multiple strategies (i.e. traits uncorrelated with the PES) affect plant biomass allocation, hindering our ability to connect environmental gradients to ecosystem services.2. We examined intraspecific dimensionality of leaf and root traits in the salt marsh pioneer species Spartina anglica across salinity, redox and sand content gradients, and related them to above‐ground and below‐ground plant biomass—properties associated with wave attenuation and sediment stabilization in coastal marshes.3. Through principal component analysis, we did not find support for a single PES trait dimension (strategy), but instead identified four trait dimensions: (a) leaf economic spectrum (LES, leaf analogue of PES); (b) fine roots‐rhizomes; (c) coarse roots; and (d) salt extrusion. Structural equation modelling showed a shift towards the conservative side of the LES under increasing salinity, while redox had a positive influence on the coarse roots dimension. In turn, these trait dimensions were strongly associated with above‐ground and below‐ground biomass (BLW biomass) allocation.4. These results indicate that under high salinity, plants will adopt a conservative strategy and will invest more in BLW biomass. Yet, high sediment redox would still allow plants to invest in above‐ground biomass. Therefore, plants' trait‐mediated biomass allocation depends on the specific combination of abiotic factors experienced at the local scale.5. Synthesis. Our study highlights the importance of considering multiple ecological strategies for understanding the effect of the environment on plants. Abiotic stresses can influence multiple trait strategy‐dimensions, with consequences for ecosystem funct

1. The plant economic spectrum (PES) predicts a suite of correlated traits in a continuum from resource conservation to rapid resource acquisition. In addition to competing for resources, plants need to cope with other environmental stresses to persist and reproduce. Yet, it is unclear how multiple strategies (i.e. traits uncorrelated with the PES) affect plant biomass allocation, hindering our ability to connect environmental gradients to ecosystem services.2. We examined intraspecific dimensionality of leaf and root traits in the salt marsh pioneer species Spartina anglica across salinity, redox and sand content gradients, and related them to above‐ground and below‐ground plant biomass—properties associated with wave attenuation and sediment stabilization in coastal marshes.3. Through principal component analysis, we did not find support for a single PES trait dimension (strategy), but instead identified four trait dimensions: (a) leaf economic spectrum (LES, leaf analogue of PES); (b) fine roots‐rhizomes; (c) coarse roots; and (d) salt extrusion. Structural equation modelling showed a shift towards the conservative side of the LES under increasing salinity, while redox had a positive influence on the coarse roots dimension. In turn, these trait dimensions were strongly associated with above‐ground and below‐ground biomass (BLW biomass) allocation.4. These results indicate that under high salinity, plants will adopt a conservative strategy and will invest more in BLW biomass. Yet, high sediment redox would still allow plants to invest in above‐ground biomass. Therefore, plants' trait‐mediated biomass allocation depends on the specific combination of abiotic factors experienced at the local scale.5. Synthesis. Our study highlights the importance of considering multiple ecological strategies for understanding the effect of the environment on plants. Abiotic stresses can influence multiple trait strategy‐dimensions, with consequences for ecosystem funct

Recent studies in salt marshes have demonstrated the role of plant roots in sedimentstabilisation, and hence the importance of marshes in providing coastal protection.However, the relative role of root traits and environmental factors in controlling sedimentstability, and how intraspecific variability of root traits vary within and among marshes,remain poorly understood. In this study, we investigated which root trait(s) drive sedimentstability (resistance to lateral erosion) in two marsh species with an important role incoastal protection (Spartina anglica and Atriplex portulacoides) and how the environmentaffects the expression of these traits. We sampled three marshes along salinity gradientsin each of two estuaries in Wales (UK), establishing replicate plots in the respectivedominant zones of each species. In all plots we sampled abiotic variables (sand, redoxpotential, pH, salinity) and root traits (root density, specific root density, root volume, rootlength density); in a subset of these plots (three per species in each marsh) we extractedsoil-plant cores and assessed their erosion resistance in a flume. Sediment stability wasenhanced by increases in root density and reductions in sand content. Abiotic variablesaffected root density in different ways depending on species: in S. anglica, redox was theonly significant factor, with a positive, linear effect on root density; in A. portulacoides,redox had a non-linear (U-shaped) effect on root density, while sand had a negativeeffect. Collectively, these results show that (i) intraspecific variability in root density caninfluence sediment stability in salt marshes, and (ii) sediment properties not only influencesediment stability directly, but also indirectly via root density. These results shed lighton spatial variability in the stability of salt marshes to lateral erosion and suggest thatroot density should be incorporated into coastal vegetation monitoring programs as aneasy-to-measure root trait that links the

Recent studies in salt marshes have demonstrated the role of plant roots in sedimentstabilisation, and hence the importance of marshes in providing coastal protection.However, the relative role of root traits and environmental factors in controlling sedimentstability, and how intraspecific variability of root traits vary within and among marshes,remain poorly understood. In this study, we investigated which root trait(s) drive sedimentstability (resistance to lateral erosion) in two marsh species with an important role incoastal protection (Spartina anglica and Atriplex portulacoides) and how the environmentaffects the expression of these traits. We sampled three marshes along salinity gradientsin each of two estuaries in Wales (UK), establishing replicate plots in the respectivedominant zones of each species. In all plots we sampled abiotic variables (sand, redoxpotential, pH, salinity) and root traits (root density, specific root density, root volume, rootlength density); in a subset of these plots (three per species in each marsh) we extractedsoil-plant cores and assessed their erosion resistance in a flume. Sediment stability wasenhanced by increases in root density and reductions in sand content. Abiotic variablesaffected root density in different ways depending on species: in S. anglica, redox was theonly significant factor, with a positive, linear effect on root density; in A. portulacoides,redox had a non-linear (U-shaped) effect on root density, while sand had a negativeeffect. Collectively, these results show that (i) intraspecific variability in root density caninfluence sediment stability in salt marshes, and (ii) sediment properties not only influencesediment stability directly, but also indirectly via root density. These results shed lighton spatial variability in the stability of salt marshes to lateral erosion and suggest thatroot density should be incorporated into coastal vegetation monitoring programs as aneasy-to-measure root trait that links the