Luquillo LTER

Scientific Evidence Supports Indigenous Peoples’ Palm-harvesting Practices

Recently we have found a relationship between palm leaf chemistry and lunar cycles (e.g. full moon, new moon etc.). It is well known that farmers from many cultures time planting and harvesting to lunar cycles. For example the Mayans time the harvest of palm fronds to lunar cycles with the justification that palms harvested when there is a full moon last much longer that those harvested with no moon. In a recent study we compared secondary chemistry (compounds produced by a plant that don’t have primary metabolic functions) of palm fronds at Luquillo forest and found a significant relationship to the lunar cycle, with an abundance of secondary chemicals at the time of the full moon. The justification is that there is more light and insect herbivore activity during the full moon. If this is true it not only supports indigenous knowledge but could also have a significant impact on conservation of palms in tropical forests. We have received information from scientists in Poland and the Czech Republic who are also finding relationships between lunar cycles and plant chemistry. In every case, we are still trying to quantify and understand the relationships.
These findings are critical to sustainable forest management, and without stability and resources that LTER funding provides, this work would be impossible.

Fungal Diversity Greater in Tropical Forest Litter

Also at Luquillo LTER, we have found fungal diversity in the litter layer of tropical forests to be especially high because of the high degree of differential occurrence of microfungi among different leaf species. This fungal diversity, in turn, plays a role in determining the rates of leaf decomposition because dominant fungi from a particular leaf species decompose their preferred substrate faster than dominant fungi from other leaf species. Through this work, we now know that microbial diversity is important to the rates of ecosystem processes—new information made possible by LTER funding.
These experiments were performed by a graduate student at the University of Puerto Rico (Mirna Santana) supported by a research fellowship from the LUQ-LTER. The USDA-Forest Service (both the Forest Products Laboratory and the International Institute of Tropical Forestry) assisted with some of the analyses and supplies.

Large Dams Reduce Aquatic Species' Adundance

Large dams dramatically reduce abundance of migratory freshwater shrimp and native fish, while streams with no large dams had high abundances of these organisms. This difference in native fauna is associated with benthic resources; Compared to rivers with no large dams, pools in dammed streams had nine times more epilithic algal abundance, 20 times more fine particulate organic matter, 65 times more fine particulate inorganic matter, 27 times more carbon and 18 times more nitrogen. Small-scale shrimp and native fish exclosure/enclosure experiments performed at a subset of the sampled sites caused significant differences in epilithic algae, organic matter, inorganic matter, carbon and nitrogen. For these benthic matter parameters, these small-scale experiments accurately predicted the direction and the magnitude of differences in the whole-catchment, decades-long natural experiment represented by the comparision of dammed vs. undammed sites. This research contributes to LTER goals by extrapolating small-scale experiments to the larger scales at which humans affect watersheds and by starting to regionalize Luquillo LTER stream research, examining whether interactions previously found in streams in the Luquillo Experimental Forest apply across the island.

This work is performed by Effie Greathouse, Institute of Ecology (University of Georgia) DISSERTATION IN PROGRESS, Catherine Pringle (Institute of Ecology, University of Georgia), William McDowell (Department of Natural Resources, University of New Hampshire) and Jeff Holmquist (University of Santa Barbara)