Root trait responses of six temperate grassland species to intensive mowing and NPK fertilisation: a field study in a temperate grassland

Plant traits may characterize functional ecosystem properties and help to predict community responses to environmental change. Since most traits used relate to aboveground plant organs we aim to explore the indicative value of root traits. We examined the response of root traits (specific root length [SRL], specific root surface area [SRA], root diameter [RD], root tissue mass density [TMD], root N concentration) in six grassland species (3 grasses, 3 herbs) to four management regimes (low vs. high mowing frequency; no fertilization vs. high NPK fertilization). The replicated experiment in temperate grassland with long continuity simulated the increase in grassland management intensity in the past 50 years in Central Europe. Increasing mowing frequency (one vs. three cuts per year) led to no significant root trait changes. NPK fertilization resulted in considerable trait shifts with all species responding in the same direction (higher SRL, SRA and N concentration, lower TMD) but at different magnitude. Fertilization-driven increases in SRA were mainly caused by lowered tissue density while root diameter reduction was the main driver of SRL increases. We conclude that root morphological traits may be used as valuable indicators of environmental change and increasing fertilization in grasslands.