Formation of aggregates and storage of carbon mediated by earthworms in two soil series of Puerto Rico

dc.contributor.advisor Sánchez-de León, Yaniria Morejón, Mauricio College of Agricultural Sciences en_US
dc.contributor.committee Sotomayor-Ramírez, David
dc.contributor.committee Flores Mangual, Mario
dc.contributor.department Department of Crops and Agro-Environmental Sciences en_US
dc.contributor.representative Rodríguez, Daniel 2019-08-16T16:53:17Z 2019-08-16T16:53:17Z 2019-06-03
dc.description.abstract Earthworms play an important role in soil aggregate formation and carbon incorporation. However, there are no currently published reports of soil aggregate formation mediated by earthworms in the soils of Puerto Rico. This study investigated the carbon incorporation from maize leaves litter (C4 plant) into aggregates in field conditions and the effect of endogeic earthworms on water stable aggregates and carbon incorporation into the aggregates in laboratory conditions. The 6-month field experiment was conducted after application of maize leaves residue on micro-plots of Dagüey and Consumo soils within a secondary forest at Alzamora farm of the University of Puerto Rico at Mayagüez (UPRM). Measurements of aggregate size distribution, total carbon and nitrogen concentratios, 13C concentration, earthworm abundance and biomass were performed. Relation of the earthworm abundance and biomass with aggregate size proportion was analyzed. Only Consumo soil presented change in δ 13C signal between treatments. There was a negative relation between earthworm abundance and large macroaggregates+C4 (P=0.02; R2=0.49) and small macroaggregates+C4 (P=0.01; R2=0.51) for Dagüey soil. In Consumo soil with large macroaggregates+C4 (P=0.001; R2=0.95) and small macroaggregates+C4 (P=0.01; R2=0.80). The microcosm experiment was conducted by 20-day laboratory incubation using 13C naturally labeled maize leaves (-13.76 ±0.08 ‰) and soil collected from Dagüey (-25.48 ± 0.31 ‰) and Consumo (-27.02 ±0.15 ‰) soils. Soil crushed and sieved (< 250 µm) was subjected to four treatments: (I) soil; (II) soil + C4-leaf litter; (III) soil + C4-leaf litter + earthworms (low abundance); and (IV) soil + C4-leaf litter + earthworms (high abundance). At the end of the experiment, aggregate size distribution, total carbon and nitrogen concentrations, 13C concentration, and carbon concentration from soil and C4-leaf litter were measured. The results showed that treatment with earthworms (III and IV) had approximately 3 to 5 times higher small macroaggregates than treatments I and II for Dagüey soil. Also, Consumo soil showed higher mass proportion of small macroaggregates in treatment IV than treatments II and III, however it was similar to treatment I. This study showed that endogeic earthworm species increase the small macroaggregate mass proportion at the expense of other fractions. en_US
dc.description.graduationSemester Summer en_US
dc.description.graduationYear 2020 en_US
dc.description.sponsorship Financing from the United States Department of Agriculture (USDA), project H-461 en_US
dc.language.iso en en_US
dc.rights Attribution-NonCommercial-ShareAlike 3.0 United States *
dc.rights.holder (c) 2019 Mauricio Morejón Centeno en_US
dc.rights.uri *
dc.subject Aggregates en_US
dc.subject carbon en_US
dc.subject incorporation en_US
dc.subject earthworms en_US
dc.subject endogeic en_US
dc.subject.lcsh Soil structure -- Puerto Rico en_US
dc.subject.lcsh Soil -- Analysis en_US
dc.subject.lcsh Soils -- Carbon content en_US
dc.subject.lcsh Earthworms en_US
dc.title Formation of aggregates and storage of carbon mediated by earthworms in two soil series of Puerto Rico en_US
dc.type Thesis en_US
dspace.entity.type Publication Soil Sciences en_US M.S. en_US
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