Canopy Trimming Experiment (CTE) Plot Treatments

This data set is updated every time a trim is performed on the plots. The last trim was in 2014. The Luquillo Experimental Forest LTER program in Puerto Rico was initially focused on the understanding of the effects that two major hurricanes, Hugo in 1989 and George in 1998, had on the structure and function of a tropical mountain forest and how the biota responded to these disturbances. This focus provided insights into the key characteristics of disturbance that alter forest function over long time scales. After several years of research through the LEF-LTER program, it became clear that one primary effect of disturbances associated with the impact of a hurricane is to redistribute organic matter from live biomass compartments to the detrital pool. Then a combination of biotic and abiotic processes, all modified by the disturbance, contributes to the decomposition of detritus and to the subsequent fate of associated C and nutrients. These critical regulating processes define detrital dynamics and play a central role in the recovery of forest structure and function by regulating decomposition and therefore carbon and nutrient storage and flow. Our understanding of hurricane impacts comes from measurements of the effects of naturally occurring hurricanes on tabonuco forest and comparisons with similar disturbances in other forests (Walker et al. 1991, 1996a). Base on the evaluation of long-term measurements after the impact of hurricane Hugo and George it becomes clear that the two primary effects of hurricane disturbance are changes in microclimate and redistribution of biomass, and that the interaction of both factors propagate through the system in complex ways. These measurements are informative but cannot tease apart the effects of various aspects of hurricane disturbance and suffer from the lack of a control or reference condition. From this assessment the LUQ-LTER principal investigators jointly identified the need for an experimental manipulation to decouple the effect of shifts in resource availability due to redistribution of biomass and altered microclimate conditions due to canopy opening on community and ecosystem processes and forest recovery. As a long term experiment, the CTE is also designed to help evaluating predictions regarding the effects of an increased intensity and rate of hurricane disturbance on tabonuco forest (Sanford et al. 1991) as predicted by climate change models for Caribbean hurricanes (Emmanuel 1987, Goldenberg et al. 2001). This long-term experiment will increase the frequency of simulated hurricane effects above background levels to once every six years. The experiment will determine effects of repeated disturbance of the forest canopy and increased detrital inputs to the forest floor on germination, growth, survival, nutrient cycling, soil conditions, and trophic structure.