Efecto de sustrato y densidad en la calidad de plántulas de cedro, caoba y roble

reforestation in mexico is important to recuperate the productivity of deforested and degraded areas and to maintain that of commercial forests. only 40% of reforested areas have an acceptable level of survival. characteristics of seedlings out planted, including shoot/root ratio, are essential factors for achieving the desired results of high survival and good growth after transplanting. this study describes the characteristics of mahogany (swietenia macrophylla king), spanish cedar (cedrela odorata l.) and "roble" (tabebuia rosea (bertol.) dc when planted at two densities (100 and 50 plants/m2) and in two substrates [soil, and soil + compost (s+c)] in a nursery. the s+c treatment had a significant effect on diameter, height, root biomass and the shoot/root ratio. in soil 76% of seedlings had a shoot/root ratio of 3.0 or less and in s+ c, 21 % of seedlings had a ratio less than 3.0. for conifers a ratio of 2/1 is recommended for dry sites and 4/1 for humid sites. for broadleaves the optimum shoot/root ratio is not known. two months after transplanting in the field more swietenia produced with the s+c treatment died but less cedrela and tabebuia seedlings did. for the three species the seedlings that died were smaller.