Spatial distribution of soil and leaf litter microbial communities in a simulated hurricane experiment.

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Microbial communities play important roles in litter decomposition and nutrient cycling. The Canopy Trimming Experiment, started in 2003 at the Luquillo Experimental Forest in Puerto Rico, focused on the immediate effects of hurricanes on forest floor processes and recovery in a tropical wet forest ecosystem. Changes in microbial community structure in the forest soil and litter layer may influence ecosystem recovery. Canopy trimming was applied again in October-November 2014 with the purpose of understanding long-term effects of increased hurricane frequency on forest productivity and carbon sequestration. We used the treatment to study unresolved short-term effects of canopy opening and debris deposition on litter and soil processes. Nutrient leaching and mineralization from green leaves was determined using WesternAg Plant Root Simulator (PRS) Probes placed in the leaf litter fermentation layer (above the mineral soil)  one week prior trimming (T0), and one (T1), two (T2), three (T3), five (T4), and 12 (T5) weeks post trimming. Differences between treatments and among times were analyzed using a linear model in MiniTab. Soil and leaf litter were collected at T0, T1, T2, T3 T4 and T5. DNA was extracted using MoBio Power Soil DNA Isolation kit. The TRFLP technique was used to obtain profiles of the microbial communities in each sample using the fungal ITS region and the 16S for the bacterial communities. Changes in microbial community structure between samples were analyzed using NMDS and UPGMA. Significant differences in nutrient concentrations between unmanipulated control and trimmed plus debris plots were observed for total N, NH₄, Ca, K, P, S and Mg in leachates. Leachate nutrients were higher in the trimmed plots. Total leachate N, NH₄, P and S also changed significantly with time, and there was a significant treatment by time interaction for N, NH₄ and P. Leaching of P, K, S and Mg began immediately in trimmed plots. All nutrients showed a peak at T4 (5 weeks). The results indicate that microbial communities are significantly different between unmanipulated controls and trimmed plus debris plots.