Enhanced decomposition of selenium hyperaccumulator litter in a seleniferous habitat—evidence for specialist decomposers?

Abstract

Selenium (Se) hyperaccumulation, when plant species accumulate upwards of 1,000 mg Se kg �1 dry weight (DW), protects plants from a variety of herbivores and pathogens. The objective of this study was to determine the effect of plant Se concentration on the rate of litter decomposition by invertebrates and microbes in a seleniferous habitat. Decomposition, Se loss, the decomposer community and soil Se concentration beneath leaf litter were compared between litter from two populations of the Se hyperaccumulator Astragalus bisulcatus (one population with 350 and the other with 550 mg Se kg �1 DW) and from the related non-accumulator species Astragalus drummondii and Medicago sativa containing 1- 2m g Se kg �1 DW using a litterbag method. High-Se litter decomposed faster than low- Se litter and supported more microbes and arthro- pods than low-Se leaf litter after 8 and 12 months, respectively. Soil collected from under high-Se litter had higher Se concentration than soil from beneath low-Se litter after 8 months. The higher decompo- sition rate and abundance of decomposers in high- Se litter indicates the presence of Se-tolerant decomposers in this seleniferous habitat that may have contributed to increased decomposition rates of high-Se litter.