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Canopy opening increases leaf-shredding arthropods and nutrient mineralization but not mass loss in wet tropical forest

Moreno, I. I., M. F. Barberena-Arias, G. González, D.J. Lodge and S. A. Cantrell. 2022.


Abstract Hurricanes alter forest habitat by opening the canopy and depositing fresh wood and leaves. The objectives of this study were to evaluate the effects of hurricane and drought-driven changes to forests on green litter decomposition, invertebrate communities, and nutrient mineralization over a short period (6 months) after disturbance. We used three complete replicated blocks with two canopy treatments: control and trim + detritus. Green leaves were enclosed in litterbags of three different mesh sizes to determine the effect of soil fauna of varying body sizes. Litterbags were retrieved from the field after 21, 35, 84, and 168 days and transported to the laboratory in individually sealed plastic bags. We extracted and identified invertebrates, measured leached and mineralized litter nutrients using ion resin membranes placed for 1 week under the leaves inside the litterbags, and determined litter mass loss. Additional resin membranes were placed in the lowest litter layer above the mineral soil. The number of arthropod taxonomic groups and nutrient mineralization differed significantly between control and trim + detritus. Regardless of mesh size, bags in control plots had consistently higher invertebrate richness than in trim + detritus plots. Nitrogen mineralization and phosphorous mineralization were significantly higher in trim detritus in large mesh size, and decomposer arthropod abundance was highest in large-sized mesh bags. These data suggest that within functional categories, variations in feeding behavior among arthropod orders may affect the release of nutrients from organic matter. Percent mass loss did not differ between canopy treatments or litterbag mesh sizes, but instead decreased during drought. Invertebrate composition, but not abundance, differed significantly between canopy treatments with greater dominance by shredders (Lepidoptera and Diptera larvae) in trim + detritus, which corresponded to higher rates of nutrient mineralization from green leaves. These results suggest that regional drought dominated the mesoclimate surpassing any microclimate variation in response to canopy treatments. Since mass loss did not differ between canopy treatments or litterbag mesh sizes, our results suggest that differences in short-term nutrient fluxes from green litter are mostly related to changes in the litter invertebrate food web rather than rates of decomposition.

Key Words

arthropods, canopy opening, green litter, hurricane disturbance, litter decomposition, Luquillo Mountains, mass loss, nutrient mineralization, Special Feature: Tropical Forest Responses to Repeated Large-Scale Experimental Hurricane Effects, tropical forest