Comparison of the chemical alteration trajectory of Liriodendron tulipifera L. leaf litter among forests with different earthworm abundance

Abstract

[1] To investigate the control of earthworm populations on leaf litter biopolymer decay dynamics, we analyzed the residues of Liriodendron tulipifera L. (tulip poplar) leaves after six months of decay, comparing open surface litter and litter bag experiments among forests with different native and invasive earthworm abundances. Six plots were established in successional tulip poplar forests where sites varied in earthworm density and biomass, roughly 4-10 fold, of nonnative lumbricid species. Analysis of residues by diffuse reflectance Fourier transform infrared spectroscopy and alkaline CuO extraction indicated that open decay in sites with abundant earthworms resulted in residues depleted in cuticular aliphatic and polysaccharide components and enriched in ether-linked lignin relative to open decay in low earthworm abundance plots. Decay within earthwormexcluding litter bags resulted in an increase in aliphatic components relative to initial amendment and similar chemical trajectory to low earthworm open decay experiments. All litter exhibited a decline in cinnamyl-based lignin and an increase in nitrogen content. The influence of earthworm density on the chemical trajectory of litter decay was primarily a manifestation of the physical separation and concentration of lignin-rich and cutin-poor petioles with additional changes promoted by either microorganisms and/or mesofauna resulting in nitrogen addition and polysaccharide loss. These results illustrate how projected increases in invasive earthworm activity in northern North American forests could alter the chemical composition of organic matter in litter residues and potentially organic matter reaching the soil which may result in shifts in the aromatic and aliphatic composition of soils in different systems.

Historical land use and stand age effects on forest soil properties in the Mid-Atlantic US

“…The uncut forests are dominated by several species of oak (Quercus) with the dominant species being chestnut oak (Q. prinus) which contributes 70% of the total litter input (Szlavecz unpublished data). Previous research by our group has demonstrated that nonnative earthworms are an important component of SERC forests (Crow et al, 2009;Filley et al, 2008;Ma et al, 2013;Szlavecz and Csuzdi, 2007;Szlavecz et al, 2011). In the context of this study, the uncut forests on Hog Island, Fox Point and Big Island are earthworm-free while non-native earthworms are abundant in soils at the old and young forest stands (Szlavecz and Csuzdi, 2007;Szlavecz et al, 2011).…”

“…While agricultural legacies are still detected in old forest soils, present nutrient concentrations may be more strongly affected by the ongoing mixing of leaf litter with mineral soil. Detailed chemical analyses of plant litter residue and different fractions of soil organic matter at a subset of our sites strongly support the latter mechanism (Filley et al, 2008;Crow et al, 2009;Ma et al, 2013).…”

“…The earthworms most likely remained in the recovering forests. Altered carbon chemistry and storage due to selective feeding has been attributed to earthworms (Filley et al, 2008) and has a lasting legacy in the soil (Crow et al, 2009;Ma et al, 2013). Earthworms can indirectly affect understory plants as has been shown for orchids at SERC , ferns in Minnesota (Gundale, 2002), eventually modifying the structure and function of the entire plant community (Forey et al, 2011;Hale et al, 2006;Nuzzo et al, 2009).…”

Methodological Considerations in the Study of Earthworms in Forest Ecosystems

“…Filley et al [65] determined the use of 1 mm mesh litterbags was sufficient to exclude all macrofauna in their study including earthworms in northern temperate deciduous forests on a successional spectrum. In a comparison study between Northern deciduous and conifer forests in Colorado, González et al [63] used litterbags of two different mesh sizes to quantify the effects of different groups of soil fauna on the decay of aspen leaves and lodgepole pine needles.…”

“…Comparing mass loss rates between different mesh size leaf litterbags or between earthworm treatments may allow deduction of the direct influence of the given earthworm community on these processes [45,[62][63][64][65][66][67].…”