Authors: Richard A Gill Jennifer A Boie John G Bishop Lindsay Larsen Jennifer L Apple R David Evans
Publish Date: 2006/02/07
Volume: 148, Issue: 2, Pages: 312-324
Abstract
In the two decades following the 1980 eruption of Mount St Helens in Washington State the N2fixing colonizer Lupinus lepidus is associated with striking heterogeneity in plant community and soil development We report on differences in nutrient availability and plant tissue chemistry between older dense patches core of L lepidus and more recently established low density patches edge In addition we conducted a factorial nitrogen and phosphorus fertilization experiment in core patches to examine the degree of N and P limitation in early primary succession We found that there were no significant differences in N or P availability between core and edge L lepidus patches during the dry summer months although nutrient availability is very low across the landscape In the high density patches we found lower tissue N content and higher fiber content in L lepidus tissue than in the younger edge patches The addition of nutrients substantially altered plant community composition with N addition causing an increase in other forb biomass and a corresponding competitioninduced decline in L lepidus biomass The majority of the positive biomass response came from Hypochaeris radicata In the second year of the fertilization experiment the addition of N significantly increased total community biomass while L lepidus biomass declined by more than 50 The response of every species other than L lepidus to N additions suggests that N may be the macronutrient most limiting plant production on Mount St Helens but that the gains in productivity were somewhat offset by a decline of the dominant species By the third year of the experiment L lepidus began to increase in abundance with P addition This result suggests colimitation of the community by N and P
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