These papers are a contribution to the long-standing question : what is a plant communtiy ? I was just about to start my Ph.D. thesis when my dear colleague Richard Michalet and I met Ray Callaway from the University of Montana, USA. This fortuitous meeting with Ray held in the Caucasus mountains near Kazbegui (!) and certainly changed my life as a scientist. We have been embarked in a global-scale analysis of of plant-plant interactions in mountain grasslands testing the hypothesis of a shift from competition (negative interactions) to facilitation (positive interactions) when environmental conditions for plant life get harsher. We came out to the conclusion that in stressful environments a plant community is an integrated level of organisation challenging the individualistic’ paradigm of plant community organization. I am very grateful to all the "alpine pals" for the great time we have had working on facilitation. Callaway & al. (2002) for a momentum of this research.

• Carboni, M., T. Munkemuller, S. Lavergne, P. Choler, B. Borgy, C. Violle, F. Essl, C. Roquet, F. Munoz, W. Thuiller, and C. DivGrass. 2016. What it takes to invade grassland ecosystems: traits, introduction history and filtering processes. Ecology Letters 19:219-229. [pdf]
  
  
• Michalet, R., J.-P. Maalouf, P. Choler, B. Clement, D. Rosebery, J.-M. Royer, C. Schoeb, and C. J. Lortie. 2015. Competition, facilitation and environmental severity shape the relationship between local and regional species richness in plant communities. Ecography 38:335-345.[pdf]
  
  
• Schöb, C., P. M. Kammer, Z. Kikvidze, P. Choler, S. von Felten, and H. Veit. 2010. Counterbalancing effects of competition for resources and facilitation against grazing in alpine snowbed communities. Oikos 119:1571-1580. [pdf]
  
  
• Gross, N., P. Liancourt, P. Choler, K. N. Suding, and S. Lavorel. 2010. Strain and vegetation effects on local limiting resources explain the outcomes of biotic interactions. Perspectives in Plant Ecology Evolution and Systematics 12:9-19. [pdf]
  
  
• Brooker, R., Z. Kikvidze, F.I. Pugnaire, R.M. Callaway, P. Choler, C.J. Lortie, and R. Michalet. 2005. The importance of importance. Oikos 109:63-70. [pdf]
  
  
• Kikvidze, Z., F.I. Pugnaire, R. W. Brooker, P. Choler, C.J. Lortie, R. Michalet, and R.M. Callaway. 2005. Linking patterns and processes in alpine plant communities: A global study. Ecology 86:1395-1400. [pdf]
  
  
• Newingham, B.A., G. Boquien, P. Choler, and R.M. Callaway. 2005. Effects of Festuca paniculata on the compensatory growth response of Centaurea uniflora in the French Alps. Plant Ecology, 176, 237-244. [pdf]
  
  
• Lortie, C.J., R.W. Brooker, R. M. Callaway, P. Choler, Z. Kikvidze, R. Michalet, and F.I. Pugnaire. 2004. Rethinking plant community theory. Oikos 107:433-438. [pdf]
  
  
• Callaway, R.M., R.W. Brooker, P. Choler, Z. Kikvidze, C.J. Lortie, R. Michalet, L. Paolini, F.I. Pugnaire, B. Newingham, B.J. Cook, and E.T. Aschehoug. 2002. Positive interactions among alpine plants increase with stress. Nature (London) 417:812-820. [pdf]
  
  
• Michalet, R., C. Gandoy, D. Joud, J.-P. Pagès, and P. Choler. 2002. Plant community composition and biomass on calcareous and siliceous substrates in the northern French Alps: comparative effects of soil chemistry and water status. Arctic, Antarctic, and Alpine Research 34:102-113. [pdf]
  
  
• Choler, P., R. Michalet, and R.M. Callaway. 2001. Facilitation and competition on gradients in alpine plant communities. Ecology 82:3295-3308. [pdf]