Canopy Trimming Experiment (CTE) Microbial diversity DNA data

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Hurricanes are common disturbances in the Caribbean region that affect tree distribution, species diversity and biomass in forests. Little is known of how microbial communities in soil and litter are affected by natural or anthropogenic disturbances. The objective of our study was to determine the relative abundance and diversity of microorganisms in leaf litter at different stages of decomposition, and the effect of canopy opening and debris addition or removal.

Results: Leaf mass loss was slowest in the treatment with canopy trimming and debris removal. Canopy opening was associated with lower litter moisture, lower fungal connectivity between litter layers and slower mass loss after three months. Addition of green leaves increased moisture, and frequently accelerated mass loss of the senesced leaves below them at 17, 28 and 40.5, but not 53 weeks. After 28 weeks, mass loss showed a significant treatment interaction, and was concordant with fungal connectivity between litter cohorts. TRFLP profiles of the 16S rDNA digested with MnlI and fungal ITS digested with HaeIII shows that the microbial communities at 17, 28 and 53 weeks were highly divergent among treatments (Sorensen index of similarity). In comparisons of green versus senesced leaves within treatments, bacterial communities’ differed somewhat, fungal communities differed strongly, but mass loss did not differ. Conclusions: Microbial community changes through time can be related to microclimate and the availability of labile compounds. Fungi appeared to control the succession of microorganisms in decomposing leaves.

Date Range: 
2006-07-05 00:00:00 to 2006-07-13 00:00:00

Publication Date: 

2011-06-11 00:00:00



Additional Project roles: 

Name: Eda Melendez-Colom Role: Data Manager
Name: D. Jean Lodge Role: Associated Researcher


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.

Additional information: 

This data set was previously published as luqmetadata159 and moced to 180 for technical reasons. 8/3/2013- ECMC, LUQ IM.



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