The responses of seven co-occurring woodland herbaceous perennials to localized nutrient-rich patches

1 Nutrient-rich patches can occur in soils at a wide range of spatial and t emporal scales. Differences in the root proliferation response between spec ies may be due to differing abilities of root systems to locate and recogni ze patches of differing size and nutrient concentration. 2 We investigated the root proliferation responses of seven co-occurring he rbaceous perennial British woodland species (Ajuga reptans, Glechoma hedera cea, Oxalis acetosella, Silene dioica, Stachys sylvatica, Veronica montana and Viola riviniana) and the effect of mycorrhizal colonization on any resp onse. 3 Plants were planted in nutrient-poor sand in the centre of rectangular po ts, with a nutrient-rich patch to one side and a control (sand) patch on th e other. Size and nutrient concentration of the patches were varied between treatments. 4 Species differed in the size of their root systems and in their ability t o respond to localized nutrient-rich patches. Oxalis acetosella and Viola r iviniana, which produced the smallest root systems, showed similar root gro wth in nutrient-rich and control patches. All other species responded to th e presence of a nutrient-rich patch by various combinations of root prolife ration, changes in root branching pattern and by an increase in specific ro ot length. 5 In some species the response was affected by patch attributes: Silene dio ica and Veronica montana were sensitive to the nutrient concentration of th e patch, and Glechoma hederacea did not respond to the smallest sized patch . 6 Mycorrhizal colonization had little effect on root proliferation. Only on e species (Oxalis acetosella) could be shown to benefit from colonization b y increased phosphate uptake. 7 The soil is a heterogeneous environment in terms of nutrient availability ; differences between species in the ability to exploit this heterogeneity may affect their distribution, and could be a mechanism that reduces inters pecific root competition.