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Abstract The “Gadgil effect” hypothesizes that root associations may slow down decomposition through pre‐emptive competition. In the context of recalcitrant litter decomposition, specifically coarse wood debris, it is uncertain as to what is the relative importance of soil communities associated with living roots when compared to those without roots. Here, it is hypothesized that the presence of live roots and active photosynthates will enhance wood decomposition. To test this hypothesis, the presence or absence of temperate tree roots was used in this study. Sugar maple (Acer saccharum) and white oak (Quercus alba) roots were manipulated at three sites of either limestone or shale parent rock residuum. At each site, wood substrate was placed in soils beneath the canopy of eitherA. saccharumorQ. alba, while in the presence of roots (root+). At the same time, wood substrate was placed in the same soil community, but live root exposure was eliminated by trenching (root−). This eliminated active photosynthate supply to the soil microbial community. Results determined that live root exposure promoted faster decomposition and greater mycelial colonization of wood substrate. Also, sites of shale parent rock residuum had higher rates of decomposition in comparison with limestone parent rock residuum. Although additional work is needed to determine the extent in which roots and lithology can facilitate wood decomposition, these findings suggest that living roots impact decomposers and provide a pathway towards humus and soil organic matter formation.
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Meio‐epifaunal wood colonization in the vicinity of methane seeps
Abstract In deep‐sea environments, plant remains of several origins are found, including branches, twigs, leaves, and wood pieces, among others. As most of the deep‐sea bottoms are oligotrophic and nutrient‐limited, plant remains provide an oasis of localized organic enrichment and a substrate for colonization. Sunken wood was suggested to play an important evolutionary role in the diversification of chemosynthetic ecosystems, possibly representing stepping stones for the colonization between vent and seep ecosystems. In order to understand colonization processes of the Pacific Costa Rican meio‐epifaunal assemblages associated with sunken wood, a field experiment was conducted on Mound 12 (8°55.778′N, 84°18.730′W) at ~1,000 m water depth. Woodblocks were placed in four different habitats (Mussel beds, tube worms, near mussel beds, rubble bottoms), and different local environmental conditions (seepage‐active and seepage‐inactive sites). Seven experimental Douglas fir woodblocks (each 1,047 cm2in surface area) were deployed from the R/V Atlantis using the manned submersibleAlvinin February 2009 and recovered after 10.5 months in January 2010. Sample processing and analyses led to a data set of abundance (total 9,951 individuals) and spatial distribution of nine meio‐epifaunal higher taxa/groups. Meio‐epifaunal densities on individual woodblocks ranged from 3 to 26 ind.10 cm2. Copepods accounted for the highest abundances (75.1%), followed by nauplii larvae (11.7%) and nematodes (9.8%). The maximum number of individuals (26.3 ind.10 cm−2) was found in blocks placed in seepage‐inactive areas (near active mussel beds) in contrast to 2.9 ind.10 cm−2in active areas (within a mussel bed). A hierarchical cluster analysis grouped blocks according to seepage activity and not to habitat, but tests of similarity showed no significant differences in higher taxon composition and abundances, probably owing either to substrate homogeneity or low sample size. Copepods were the most abundant representatives, suggesting that this group is one of the most successful in colonizing in the early stage of succession, in this case while hardwood substrates are not yet decomposed or bored by bivalves.
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- Award ID(s):
- 1634172
- PAR ID:
- 10458200
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Marine Ecology
- Volume:
- 41
- Issue:
- 1
- ISSN:
- 0173-9565
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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