Plant herbivore interactions: combined effect of ground water level,
root vole grazing and sedge silication
Abstract
1. Silicon mediated plant–herbivore interactions have gained increasing
recognition and have now been studied in a wide range of species. Many
studies have also considered accumulation of Si by plants as a process
largely driven by geo-hydrological cycles. 2. To identify factors
driving the water - plant Si - herbivore nexus we analysed the
concentration of Si in fibrous tussock sedge (Carex appropinquata), the
population density of the root vole (Microtus oeconomus) and the ground
water level, over 11 years. 3. The largest influence of autumn Si
concentration in leaves (Sileaf) was the level of the current year’s
ground water table, which accounted for 13.3% of its variance. The
previous year’s vole population density was weakly positively correlated
with Sileaf and alone explained 9.5% of its variance. 4. The only
variable found to have a positive, significant effect on autumn Si
concentration in rhizomes (Sirhiz) was the current year spring water
level explaining as much as 60.9% of its variance. 5. We conclude that
the changes in Si concentration in fibrous tussock sedge are
predominantly driven by hydrology, with vole population dynamics being
secondary. Our results provide only partial support for the existence of
plant-herbivore interactions, as we did not detect the significant
effects of Si tussock concentration on the vole density dynamics. This
was mainly due to low level of silification of sedges, which was
insufficient to impinge herbivores. Future studies on plant–herbivore
interactions should therefore mainly focus on identification of
mechanisms and conditions allowing plants to accumulate silica at the
levels sufficient to act as an anti-herbivore protection.