Demographic response of tree juveniles to reduced-impact logging in a Costa Rican montane forest

We assessed diameter and height growth, and mortality in seedlings (individuals ≥0.3, but <1.5m tall) and saplings (individuals ≥1.5m tall, but <10cm DBH) of five common canopy tree species in an oak–bamboo forest in the Costa Rican highlands (2600–2800m elevation) 5 years after a controlled logging operation under two harvesting intensities (20 and 30% basal area removal of stems ≥10cm DBH, respectively). The species were Quercus costaricensis, Q. copeyensis, Drymis granadensis, Ocotea austinii, and Weinmania pinnata. For seedlings, the overall 5-year mortality rate (exponential model) was significantly higher under the lightest harvest intensity while for saplings, no significant differences in mortality were detected among harvesting intensities. Also for all species combined, annual 5-year diameter and height growth rates did not differ significantly among harvesting intensities for seedlings, although saplings grew significantly better under the higher harvest intensity. Our results suggest that, as a whole, saplings of the study species were more responsive to overstory removal than seedlings. At the species level, however, Quercus showed the largest significant differences in growth rates across harvest intensities and also with respect to the other studied species in both size classes. Based on our findings, and given the high abundance of advance regeneration at the study site (especially for Quercus), we propose that Costa Rican oak–bamboo forests show promising silvicultural potential for timber management under low-impact logging prescriptions.