The role of Equisetum in nutrient cycling in an Alaskan shrub wetland

1 Although plants of Equisetum spp. are generally thought to be of little v alue to ecosystems, a study of a cold-temperate Alaskan shrub wetland showe d that they acquired and cycled phosphorus and other nutrients more efficie ntly than other plant community members. While Equisetum plants represented only 5% of the above- and below-ground biomass in the community, they cont ained 16% of the P and 24% of the K. 2 Equisetum plants accounted for 29% of the P and 39% of the K in annual co mmunity foliage litterfall. Over a 2-year period, losses from Equisetum lit ter contributed 55, 41, and 75% of the P, K and Ca litter inputs into soil nutrient pools. 3 The ability of different species of Equisetum to acquire nutrients is lin ked to their deep rooting habit. While the majority of their roots and rhiz omes, and particularly the fine roots, were located in the C horizon, the m ajority of roots and rhizomes of other species were located in the overlyin g O horizon. The biomass of Equisetum plants was also correlated with edaph ic characteristics of the C horizon. 4 The absorption of nutrients from the C horizon by Equisetum helped bring P and other minerals to the soil surface, increasing the amount of minerals in the O horizon and thus making them potentially available to other speci es, including Myrica gale, Salix spp., and Carer spp. Productivity in this community is limited by P and N, and the ability of Equisetum to act as a n utrient pump may help explain why its net primary productivity is high for a cold-temperate wetland.