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The effects of global warming increase the frequency and intensity of many climate events such as rainfall. We evaluated the effects of environmental conditions on early stage seedling survival of the native thorn scrub species Caesalpinia mexicana A. Gray, Celtis pallida Torr., Cordia boissieri A. DC., and Ebenopsis ebano (Berland.) Barneby and J.W. Grimes, during the summer of 2009 and 2010. The experimental design had two factors, two levels of rainfall and three microhabitats of thorn scrub: (i) open interspace, (ii) thorn scrub edge and (iii) under the canopy of dense thorn scrub. In dense thorn scrub, seedling survival was higher for Caesalpinia mexicana and Celtis pallida, and for Cordia boissieri and Ebenopsis ebano seedling survival was higher in dense thorn scrub and thorn scrub edge. The effect of rainfall on seedling survival depended on the year. Rainfall in 2010 and dense thorn scrub increased seedling survival of native species. For survival, the limiting factors of microhabitats appear to change across the years. Besides rainfall events, biological aspects like competition and mycorrhiza effects would need to be considered in models of plant establishment

-Mortality in six plant species was examined in the vegetation of a mountain region in Northeastern Mexico and hypotheses of survival pathways within populations in the ecosystem were tested. Signifi cant differences in the general mortality pattern were found among species indicating species-specifi c responses to stress gradients. Average mortality differed among species: Yucca carnerosana, 33.8%; Pinus cembroides, 29.9%; Larrea tridentata, 25.9%; Hechtia podantha, 13.7%; Agave lechuguilla, 13.0%; and Thelocactus santaclarensis, 9.0%. Within populations, mortality increased with water stress and survivorship increased with less stressful environments. Results from this study may be useful for the development of a management plan to support the conservation and sustainable use of forest vegetation in this mountain community.