Uptake of moisture and nutrients by Hieracium pilosella and effects on soil in a dry sub‐humid grassland

Abstract

In dry sub‐humid environments (<550 mm annual rainfall) in New Zealand, Hieracium pilosella (hawkweed) grows in approximately circular or irregular shaped patches surrounded by areas of bare soil. The study directly assessed the extent of root distribution, soil moisture, and nutrient uptake in the areas of bare soil zone ("haloes") surrounding patches, and how hawkweed affected the soil. The results indicate that H. pilosella exploits the halo areas surrounding the plant patches for a major part of moisture and nutrients uptake. As a result, the soil in the halo zone is drier than that under the plant patch and is relatively depleted in such nutrients as available phosphorus and basic cations. The plant increases soil acidity and soluble aluminium content in the soil immediately beneath the living patch. The combined effects of reduced moisture, reduced base cation availability, and the high soluble aluminium status and increased acidity of the soil, make the immediate hawkweed environment unfavourable for the development of competing plant species.