Improving Fruit Production in Agroforestry Plantings Using Low-cost Thinning Practices in Puerto Rico’s Novel Forests.

Commodities

Practices

The forest cover of the archipelago of Puerto Rico increased from a low of 4% in the 1940's to over 50% by 2019, primarily due to the establishment of novel forest ecosystems on abandoned agricultural fields. Novel forests are often dominated by introduced species and this makes them more appealing for management and transformation into agroforestry systems that can provide food and other products in tandem with other ecosystem services. However, because of the recent emergence of novel forests, management practices have yet to be developed. This project will evaluate the effects of thinning on understory light availability and its impact on fruit tree growth and productivity on 30 novel forest stands in the northern moist region of Puerto Rico where experimental agroforestry plantings were established in 2017. The plantings included avocado, breadfruit, cacao, coffee, genip and jácana. On 15 of these stands, basal area will be reduced by 50% by girdling of canopy trees and the remaining stands will serve as controls. We will sample thinning effects on incident solar radiation and on the crop productivity and growth of planted fruit trees. We will sample the abundance of vines growing atop planted trees before and after thinning. We hypothesize that thinning will enhance fruit tree growth and productivity, and that this effect will vary according to the dominant canopy tree species. The results of this project will enable the implementation of practices to increase the economic productivity of farmers and ecosystem service provision on forested lands.

1.Evaluate whether thinning operations via girdling of overstory trees affect the growth (DBH and height) and productivity (quantity of flowers and fruits) of understory fruit trees established in agroforestry systems within the novel forests of Puerto Rico as well as changes in incident solar radiation (Understory PAR) following thinning operations.
2. Simultaneously assess how dominant canopy species within thinned stands influence the growth and productivity responses of understory fruit trees.
3. Monitor the abundance of vines on understory fruit trees within plots following changes in the canopy produced by the removal of overstory trees after 1 year.