title: Resource use efficiency and community effects of invasive Hypochaeris radicata (Asteraceae) during primary succession.
abstract: OBJECTIVE
  We sought to better understand the impacts and mechanisms underpinning a successful invasion of resource-poor sites by a nonnative plant on Mount St. Helens volcano (MSH). •
  
  
  METHODS
  We investigated the short-term effects of the nonnative plant Hypochaeris radicata on growth of native species colonizing drought-prone primary successional surfaces under N-limited and N-augmented conditions. To understand the success of H. radicata, we compared its resource use efficiency to that of a closely related native colonist, Hieracium albiflorum, under the same conditions. •
  
  
  RESULTS
  Removing H. radicata did not affect growth of the most common colonists, but N addition demonstrated strong N limitation to growth in H. albiflorum, H. radicata, and Agrostis spp. Nonnative H. radicata exhibited lower water-use efficiency than H. albiflorum but did not differ in efficiency of N use. H. radicata biomass increased faster in response to an N pulse than did the native H. albiflorum, as did the pool of N held in H. radicata tissues. •
  
  
  CONCLUSIONS
  Our findings contrast with results from Hawaiian volcanic sites, where higher short-term resource use efficiency was reported for invasive species, including H. radicata. Our results suggest that at MSH, the success of H. radicata relies on rapid uptake and utilization of N rather than on higher efficiency. This strategy is especially advantageous at MSH because N pulses commonly occur as a consequence of herbivore-induced mortality of Lupinus lepidus (Fabaceae).
authors: University of Maryland, College Park, Maryland 20742 USA.
authors: Anna C
authors: AC
authors: Schoenfelder
authors: John G
authors: JG
authors: Bishop
authors: Holly M
authors: HM
authors: Martinson
authors: William F
authors: WF
authors: Fagan