Facilitation between species mitigates nutrient constraints in grassland

Background: Experimental work using pot trials and mesocosm studies has indicated that species combinations are more effective in mitigating the soil nutrient constraints that limit pasture productivity in New Zealand’s hill country, but there is little field evidence to support this. Aim: We question whether coexistence of species provides an opportunity to facilitate enhanced uptake and improved procurement of key soil nutrients by assemblages of plants in these mid-altitude grasslands. Methods: Native and exotic legumes and co-occurring plant species were sampled according to whether they were growing together in close proximity or in single species patches. Foliar concentrations of nutrients were compared. Results: Uptake of nutrients by a native broom, Carmichaelia petriei, was enhanced when it was growing in combination with native tussock grasses. Enhanced uptake of eight nutrients was recorded in foliage of an exotic legume, Lotus pedunculatus, when it was growing with native grasses or within the acuminate foliage of Aciphylla aurea (golden spaniard). Foliar concentrations of only P and Mn were elevated in white clover (Trifolium repens) foliage when it was growing in combination with grasses. Overall, mutual facilitation of nutrient uptake by combinations of species growing together was in evidence. Conclusions: Some species that are less desirable from an agricultural perspective may improve acquisition of soil nutrients by the plant community. Novel native species assemblages represent an opportunity to refine pasture management. Exploiting combinations of plant species that facilitate optimal exploitation of nutrients could reduce fertiliser requirements, enhancing and protecting biodiversity in pastoral grasslands