Drought effects on root and shoot traits and their decomposability

<p>1. Drought can induce phenotypic plasticity in a range of plant root and shoot traits. These traits have been shown to explain differences in root and shoot litter decomposability between species. However, it is unknown how drought-induced plasticity of root and shoot traits alters their decomposability.</p> <p>2. To investigate this issue across a range of species, we grew a grass (<em>Lolium perenne</em>), a forb (<em>Plantago lanceolata</em>) and a legume (<em>Trifolium repens</em>) common to European temperate grasslands and subjected them to a 5-week moderate drought treatment. We compared morphological and chemical root and shoot traits of the droughted plants to well-watered controls. We then conducted a decomposition assay of the senesced root and shoot material over 16 weeks, with mass loss measurements at five timepoints.</p> <p>3. Drought had significant and sometimes strong effects on morphological and chemical root and shoot traits of all three species, sometimes similar to differences between species and generally in line with a shift to a more resource-conservative strategy. Drought also increased the labile litter fraction in roots of <em>Lolium</em> <em>perenne</em>, which was associated with a substantial increase in non-structural carbohydrates. Drought decreased the labile litter fraction in shoots of <em>Plantago</em> <em>lanceolata</em>, but this could not be explained by the traits we measured. Drought effects on litter decomposability were weaker than on plant traits.</p> <p>4. Our results suggest that plant trait-mediated effects of drought on litter decomposability can either increase or decrease vegetation feedbacks to climate change. They also show that drought-induced plasticity in root and shoot traits does not automatically translate into equivalent changes in litter decomposability.</p>