title: Effects of positive interactions, size symmetry of competition and abiotic stress on self-thinning in simulated plant populations.
abstract: OBJECTIVE
  Competition drives self-thinning (density-dependent mortality) in crowded plant populations. Facilitative interactions have been shown to affect many processes in plant populations and communities, but their effects on self-thinning trajectories have not been investigated.
  
  
  METHODS
  Using an individual-based 'zone-of-influence' model, we studied the potential effects of the size symmetry of competition, abiotic stress and facilitation on self-thinning trajectories in plant monocultures. In the model, abiotic stress reduced the growth of all individuals and facilitation ameliorated the effects of stress on interacting individuals.
  
  
  RESULTS
  Abiotic stress made the log biomass-log density relationship during self-thinning steeper, but this effect was reduced by positive interactions among individuals. Size-asymmetric competition also influenced the self-thinning slope.
  
  
  CONCLUSIONS
  Although competition drives self-thinning, its course can be affected by abiotic stress, facilitation and competitive symmetry.
authors.affiliation: MOE Key Laboratory of Arid and Grassland Ecology at Lanzhou University, Lanzhou, China. cjchu@lzu.edu.cn
authors.forename: Cheng-Jin
authors.initials: CJ
authors.lastname: Chu
authors.forename: Jacob
authors.initials: J
authors.lastname: Weiner
authors.forename: Fernando T
authors.initials: FT
authors.lastname: Maestre
authors.forename: You-Shi
authors.initials: YS
authors.lastname: Wang
authors.forename: Charles
authors.initials: C
authors.lastname: Morris
authors.forename: Sa
authors.initials: S
authors.lastname: Xiao
authors.forename: Jian-Li
authors.initials: JL
authors.lastname: Yuan
authors.forename: Guo-Zhen
authors.initials: GZ
authors.lastname: Du
authors.forename: Gang
authors.initials: G
authors.lastname: Wang
mesh_terms: D017753:Ecosystem; D008962:Models, Theoretical; D063245:Plant Development; D010944:Plants / Q000033:anatomy & histology*; D011156:Population Density