Luquillo LTER

The study was located in subtropical moist forest (tabonuco forest type dominated by Dacryodes excelsa) at El Verde in the Caribbean National Forest, Puerto Rico. Three blocks with four treatment plots were established. Litter decomposition baskets were placed in five randomly selected subplots per plot. Plots received the following treatments: canopy trimmed and debris added, canopy trimmed and debris removed, not trimmed with debris added, and control. One basket per subplot was retrieved at 7, 14, 28, 40.5 and 53 weeks.

Open-mesh plastic baskets 35 x 25 cm were modified by cutting out the solid bottom and replacing it with 2mm mesh woven nylon mesh. The experiment was set up between July 1 and 10, 2005. The existing non-woody forest floor (FOFL) was carefully transferred to the bottom of the basket, and a 1mm mesh plastic window screen was placed over the forest floor layer. All baskets received 10 g air-dried freshly fallen (senesced) leaves (FRFA) of Manilkara bidentata and Dacryodes excelsa in a near mono-layer covering 75%-85% of the forest floor cap screen, followed by an additional cap screen. The mixture of freshly fallen leaves in Block A was 6 g Dacryodes excelsa and 4 g Manilkara bidentata. The mixture of freshly fallen leaves in Blocks B and C was 4 g Dacryodes excelsa and 6 g Manilkara bidentata. The two treatments that received canopy debris (canopy trimming plus debris, and no trimming plus debris) received 100 g fresh weight of green leaves (GL) trimmed from the understory in the following proportions: 25 g Dacryodes excelsa, 33 g Sloanea berteriana, and 42 g Manilkara bidentata for all blocks. There wee three to four 100 g fresh weight subsamples of green leaves per batch for determination of fresh weight to oven-dried weight ratios, and initial nutrient concentrations of the green leaves. The green leaf layer was followed by a cap screen to separate it from natural new litterfall (NL). There were five litter decomposition subplots in each plot, and six litter decomposition baskets in each subplot. However, the canopy trimming and debris removal treatment only had baskets in four of the five litter decomposition subplots in blocks B and C.  One basket per subplot was picked at the following intervals: 7, 17, 28, 40.5, 53 and 80 weeks, but no microbial samples were taken at 80 weeks. At the 17 and 28 week harvests, an additional ‘cap’ screen was placed in the remaining baskets to separate litterfall cohorts. Harvested baskets were returned to the station, and 2 g of leaf litter per subplot basket were pooled within plots for microbial analysis. . DNA was extracted from a 0.3 g of the pooled sample using MoBio Ultra Clean Soil DNA Isolation Kit. The 16S bacterial rDNA was amplified using primers 27F-FAM and 1525R, and digested with MnlI. The fungal ITS region was amplified using primers ITS1-FAM and ITS4, and digested with HaeIII. Samples were analyzed in an ABI 3130 using GenScan 500 Liz Size Standard.