PARENT SESSION
Poster Session #6: Conservation Ecology.
Monday, August 6, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall

Environmental gradients in the establishment of relict Acer saccharum subsp. skutchii (Rehder) E. Murray-Podocarpus reichei Buchh et N. Gray communities in southwestern México.

VARGAS-R., YALMA¹, VÁZQUEZ-G., J. ANTONIO¹, ¹

ABSTRACT- We examined whether successful regeneration has taken place in a recently discovered relict community of A. saccharum subsp. skutchii (maple) and P. reichei (podocarp), forest dominants that are listed in the Mexican Endangered Species Act. What environmental variables may explain it?. Maple and podocarp presented inversed "J" height distributions, suggesting successful regeneration. 1) Bray-Curtis-ordinations of ten plots using density showed: a) axis 1 of seedlings was explained by soluble Ca (r=0.842. p<0.01) and by Ca+Mg (r=0.816, p<0.01), while axis 2 was explained by K (r=-0.886, p<0.01); b) Axis 1 of saplings was explained by sand (r=-0.776, p<=0.01), silt (r=0.867, p<0.01), Ca+Mg (r=0.768, p<0.01), while axis 2 was explained by cat-ion exchange capacity (r=0.832, p<0.01). 2) Bray-Curtis-ordination using height for seedlings and saplings together showed axis 1 was explained by sand (r=-0.774, p<0.01). 3) direct gradient analyses showed: a) podocarp seedlings density was explained by K (r=-0.84, p<0.01), while height of podocarp seedlings and saplings together was explained by sand (r=.799, p<0.01); b) height of maple seedlings+saplings was explained by pH (r=0.767, p<0.01). Seedling density is favored by Ca and Ca+Mg, this is consistent with the notion that apical dominance and photosynthesis are promoted by Ca and Mg respectively, supporting survival and maintenance under shade. For saplings, soil texture was relevant too, suggesting that nutrient-rich and more humid silt soils are important for density of saplings and height of seedlings and saplings.

KEY WORDS: Forest regeneration, Cloud forest, Acer saccharum subsp. skutchii, Podocarpus reichei