Biostimulants increase the growth of Podocarpus glomeratus, a native conifer from the Andes, in nursery and field conditions

Abstract

Pino de monte (Podocarpus glomeratus) is a native tree species found in the tropical montane cloud forests of the Andes from Bolivia, Perú y Ecuador, and it is vulnerable to extinction. Efforts to reforest pino de monte seedlings have faced challenges due to low survival and limited growth. Biostimulants, which are organic substances have the potential to improve the seedlings survival and growth. However, their effects on slow-growing tree species, like the pino de monte, have not been extensively studied. Therefore, we evaluated the effects of a biostimulant and a fertilizer on the survival and growth of pino de monte seedlings, both in nursery (six months) and in degraded grasslands with different topographic conditions (ridges and slopes) (six months). The study took place in the locality of Independencia, Cochabamba, Bolivia. Data analysis was performed using analysis of variance and Tukey's mean comparison tests. We found high survival rates in both the nursery and degraded grasslands, higher than 90% in nursery, and higher than 80% in grasslands, with neither the biostimulant nor the fertilizer significantly affecting survival. However, the biostimulant notably increased 17% and 20% of the height of seedlings in the nursery compared to both fertilizer and control, respectively. Additionally, in degraded grasslands, the biostimulant increased 23% the height of reforested seedlings, particularly on ridge sites, where seedlings growth was higher than on slopes. In conclusion, biostimulants enhance the growth of tree seedlings from slow-growing species. We advocate for further research and broader application of biostimulants to improve the success of reforestation efforts, particularly in challenging environments.