Arboreal arthropods in response to repeated canopy opening in a tropical rainforest

This study describes canopy arthropod responses to repeated experimental canopy opening at the Luquillo Experimental Forest Long-term Ecological Research Site (LTER) in Puerto Rico. The Canopy Trimming Experiment (CTE1) was started in 2004 and a second trimming (CTE2) was conducted in 2014, in order to study effects of increased hurricane frequency at the site. In addition to the experimental manipulation, the CTE site was also directly hit by Hurricane Maria (category 4) in September 2017, providing an additional natural canopy opening to the experiment. Paired experimental plots, disturbed plots (trim), with canopy trimmed, and undisturbed plots (no-trim), with no trimming, were replicated in three blocks. Arthropods were sampled by bagging branches on seven representative early and late successional overstory and understory tree species annually from 2015 to 2019. Responses were analyzed at population and community levels for CTE2 and for CTE1 and CTE2 combined. Responses at the population level were generally similar between CTE1 and CTE2. The red wax scale, Ceroplastes rubens increased in abundance in the trimmed plots following treatment in both CTE1 and CTE2. The abundance of some scale insects increased at greater magnitude after Hurricane Maria than after experimental trimming. The intensity and frequency of hurricanes are likely to play a major role in determining future responses of canopy arthropods. Subsequent trimmings and sampling in the CTE are valuable to better understand the ecological processes in response to the predicted increase in intensity and frequency of wind disturbances.