Soil remineralization with silicate rock powder: nutrient effects on plant quality and ungulate foraging

Introduction Silicate rock powder (SRP), a slow‐release mineral additive, is increasingly used as a potential mitigation measure against soil acidification in natural areas. SRP addition has led to a higher soil base saturation and small increases in soil nutrient availability. This will likely improve plant quality and potentially lead to increased herbivory, which could counter restoration efforts. Objectives We tested the hypotheses that SRP application leads to increased plant quality and increased ungulate herbivory. Methods We revisited SRP addition experiments initiated 3.5–5.5 years ago, on acidified sandy soils in five different habitats (driftsand, driftsand heathland, dry heathland, grassland, and forest), within three protected areas in The Netherlands. We studied 12 pairs of SRP‐treated and control plots ≥1 ha. With camera traps, we measured ungulate foraging intensity. In nine plot pairs, we also collected plant material to quantify differences in plant nutrient content. Results We found that changes in plant nutrient concentrations were limited and sometimes concentrations decreased (Mg and Mn in Heather) in SRP‐treated plots. Similarly, feeding rates of wild ungulates were not higher in SRP‐treated plots. Rather, foraging rate estimates tended to be lower. Conclusions Experimental addition of SRP to acidified soils in quantities typical for ecosystem restoration did not improve plant quality and did not elevate foraging by wild ungulates for the SRP types and doses used. However, dose–response and long‐term studies are necessary to evaluate differential responses on different doses and time frames.