Natural regeneration of woody species in a Costa Rican plantation of Vochysia guatemalensis (Vochysiaceae) and the effect of P and NPK fertilization.
Forest plantation management strategies, including the selection of species, may have positive or negative effects over plant regeneration in the tropics. In this case, understory woody plants density and richness were studied in Tabarcia de Mora, Costa Rica, in a monoculture of Vochysia guatemalensis (ten year old plantation). Nineteen 80 m2plots, with several fertilization treatments (0-0; 0-50; 50-0, 50-50 g/plant of P, and NPK, during the first years, P placed once at the hole) in a completely randomized factorial design, were analyzed. Afterwards, the NPK fertilizer was increased from 150 to 200 g/ plant/year until the plantation was six year old. The plots, established after the coffee plantation was eliminated, had a minimum management schedule, basically the elimination of herbaceous vegetation once or twice a year during the first three years, and a tree thinning when the plantation was four year old, to increase spacing from 2x2 to 4x4 m. All woody vegetation taller than 0.5 m was tallied. A total of circa 10 000 ind/ha, distributed in 90 species, were found, mostly native of the region, some identified for forestry use, others important for the fauna. The majority of the species had low relative densities and frequencies. Sixteen percent of the plants reached heights greater than 2.5 m. Several factors seem to explain this regeneration pattern: a canopy with an intermediate openness, a low intensity forestry management, the nearness of the plantation to a mature forest fragment, and that the Vochysia plantation substituted a coffee plantation where soil conservation strategies and an annual fertilization management plan were applied. Finally, plots with only P had significantly higher species richness and abundance (χ2=15.364, gl=3, p=0.002) probably because the trees in this treatment were less developed (when compared with the others).