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Even though drought impacts on tree physiology have been identified, whether drought affects leaf litter chemistry that, in turn, influences litter decay rates is still poorly understood. We compared litter quality and decomposition for two cohorts of leaves from five co-occurring seasonally deciduous tree species: Acer saccharum, Tilia americana, Quercus rubra, Quercus alba, and Ostrya virginiana. One cohort experienced a growing-season drought, and the other cohort came from the same trees in the ensuing, post-drought growing season. Leaf litter production was greater for drought litter than post-drought litter for all five species. Specific leaf area and nitrogen concentrations were 20% greater for the drought cohort than the post-drought cohort. Concentrations of non-structural carbohydrates were about 14% greater for the drought cohort, except for greater values for post-drought A. saccharum litter. Pectin in the middle lamella of leaf litter was 31% lower for the drought cohort compared to post-drought cohort. We found few differences in litter decay rates between drought and post-drought cohorts, although Q. rubra litter had more decomposition for the post-drought cohort than the drought cohort, whereas A. saccharum litter had more decomposition for the drought cohort than the post-drought cohort. Leaf litter decay rates for the drought cohort were related to litter nitrogen and lignin concentrations, whereas decay rates for the post-drought cohort were related to litter carbohydrate concentrations. Our findings suggest that the role of drought events on seasonally deciduous forest ecosystems must recognize species-specific, idiosyncratic responses in leaf litter quality and decomposition. [ABSTRACT FROM AUTHOR]

Aims: We conducted a suite of tracer studies using the stable isotope 13C to follow and quantify the flow of carbon from leaf litter and roots into soil components including aggregates and biota with and without invasive earthworms. Methods: Ten-year-old saplings of sugar maple growing in the understory of a thinned northern hardwood forest were labeled with 13CO2. The 13C labeled leaf litter was applied to forest plots with and without invasive earthworms (Lumbricidae) and traced for three years. We also traced the label from the trees through the roots and into soil components in the labeling chambers. Labeled fine roots and stem wood were incubated in a forest and the label was quantified over six years of decomposition. Results: We were able to detect the litter tracer to 10 cm soil depth in plots without earthworms and to 20 cm with earthworms present, and earthworms promoted C incorporation into soil aggregates. The soil food web was much more enriched in the label from roots than from aboveground plant litter.. Rapid fine root decay was observed (k = 0.9 yr−1), and although labelled wood was almost completely decayed, little 13C was recovered in soil (0.33%). Conclusion: The approach was successful for quantifying transport and fate of tree carbon in forest soils and could be enhanced with careful quantification of gross assimilation. [ABSTRACT FROM AUTHOR]

Decomposing leaf litter is a large supply of energy and nutrients for soil microorganisms. How long decaying leaves continue to fuel anaerobic microbial activity in wetland ecosystems is poorly understood. Here, we compare leaf litter from 15 tree species with different growth forms (angiosperms and gymnosperms, deciduous, and longer life span), using litterbags positioned for up to 4 years in a forested peatland in New York State. Periodically, we incubated partially decayed residue per species with fresh soil to assess its ability to fuel microbial methane (CH) production and concomitant anaerobic carbon dioxide (CO) production. Decay rates varied by leaf type: deciduous angiosperm > evergreen gymnosperm > deciduous gymnosperm. Decay rates were slower in leaf litter with a large concentration of lignin. Soil with residue of leaves decomposed for 338 days had greater rates of CH production (5.8 µmol g dry mass d) than less decomposed (<0.42 µmol g dry mass d) or more decomposed (2.1 µmol g dry mass d) leaf residue. Species-driven differences in their ability to fuel CH production were evident throughout the study, whereas concomitant rates of CO production were more similar among species and declined with degree of decomposition. Methane production rates exhibited a positive correlation with pectin and the rate of pectin decomposition. This link between leaf litter decay rates, biochemical components in leaves, and microorganisms producing greenhouse gases should improve predictions of CH production in wetlands. [ABSTRACT FROM AUTHOR]

Plant litter is a crucial source of energy and nutrients for soil microorganisms, and thus plant species identity may help account for variation in rates of soil microbial activity via species dependent differences in litter chemistry. This may be particularly important in forested wetlands where the composition of conifer tree species can vary. We explored the relationship between conifer litter identity and anaerobic microbial activity by adding fresh needle litter from nine conifer species to soils from two contrasting forested wetlands and quantifying rates of anaerobic respiration (CO 2 production) and methanogenesis (CH 4 production). We characterized litter chemistry as the amounts of structural polysaccharides and polymers (cellulose, hemicellulose, pectin, lignin) and examined changes in these fractions during incubation. Litter from Pinus species supported the largest rates of CH 4 production, whereas litter from Picea species supported the lowest rates. Litter from two deciduous conifers ( Metasequoia , Larix ) supported intermediate rates of CH 4 production. Tree species identity had less impact on rates of anaerobic CO 2 production. Rates of CH 4 production correlated with hemicellulose and with covalently bonded pectin, whereas rates of anaerobic CO 2 production showed a positive correlation with initial acid-detergent lignin concentration and with pectin. Gaining a better understanding of how hemicellulose and pectin in decomposing plant litter promote anaerobic microbial activity, especially specialized methanogenesis in soil provides insight that links plant litter identity and leaf traits to anaerobic microbial activity in the underlying soil. [ABSTRACT FROM AUTHOR]

We investigated how soil fauna impact leaf litter decomposition in north temperate forests using litter bags with different mesh sizes (5 mm, 0.5 mm, and 0.01 mm) to exclude specific fauna by size. The experimental design included two regions (warmer, cooler) in New York State, two forest types (coniferous, deciduous), and litter bags with four tree species (yellow birch, sugar maple, red oak, red pine) that varied in litter resource quality. Excluding most soil fauna with 0.01-mm mesh decreased mass loss from litter bags by 8.8 % overall; by 19 % in the relatively warmer region; by 12 % in coniferous forest stands; and by 18 % for high-quality yellow birch litter but not for high-quality sugar maple litter or low-quality red oak and red pine litters. Mass loss rates were predicted by initial nitrogen concentrations and by initial ratios of carbon / nitrogen and lignin / nitrogen of the leaf litter; these relationships were stronger for litter bags that excluded soil fauna. Fauna extracted from the leaf litter residue were predominantly Acari (mites) and Collembola (springtails). Soil fauna mediated the extent that biochemical fractions (nitrogen, hemicellulose, cellulose, lignin) were lost from decomposing litter but in idiosyncratic ways. Not only are soil fauna impacts on leaf litter decomposition widespread, but, as shown here, they can be idiosyncratic when evaluated with several litter species that differ in resource quality, placed in different forest types, and across a climate gradient. Future analyses of soil fauna impacts on leaf litter decomposition should combine litter-, site-, and climate-related variability to improve understanding and enable prediction. • Excluding soil fauna decreased leaf litter mass loss by 8.8 %. • Soil fauna weakened leaf litter resource quality as a predictor of mass loss. • Acari and Collembola were most common; density varied with tree species. • Soil fauna are idiosyncratic in leaf litter decomposition in north temperate forest. [ABSTRACT FROM AUTHOR]

Accurate measurement of decomposition of fine roots in forests is important for understanding nutrient cycling, carbon dynamics and biotic responses; however, various sources of error or bias interfere with commonly used approaches. Most studies of fine root decomposition have used the buried root litter bag method, but this method may underestimate decay rates based on comparisons with the less disruptive, intact soil core approach. We compared these two methods for one year for seven temperate forest trees growing in twelve monospecific plantations in central New York. The experimental design included four species that form arbuscular mycorrhizae (sugar maple, red maple, cherry, tulip poplar) and three with ectomycorrhizae (pine, spruce, oak). We also examined macronutrients (N, P) release and fungal community composition of decaying fine roots using Illumina sequencing. Across the seven species and 12 plots, fine root decay rate was significantly higher for intact cores than litter bags, with the difference being approximately 12 %, a smaller disparity than that observed in previous comparisons. However, one species (Norway spruce) showed the opposite trend. Similarly, N and P release from decaying roots was significantly greater for the intact core method, but again with an exception (red oak). No consistent effects of mycorrhizal type on the method effect or decay rate and nutrient release were detected. Fungal communities in decaying roots differed between the two methods; nevertheless, Mycena spp. dominated most plots for both methods. These results further emphasize the notion that decay rates and nutrient mobilization of fine roots in forests are usually underestimated by the litter bag approach. • Fine root decay rate was greater for roots in intact cores than in litter bags. • Nutrient release from decaying roots was greater for intact soil cores. • A fungal Mycena species dominated fine root decay. • Decay of fine roots in forests is underestimated by the litter bag approach. [ABSTRACT FROM AUTHOR]