The path less taken: Long-term N additions slow leaf litter decomposition and favor the physical transfer pathway of soil organic matter formation

Eastman, Brooke A.; Adams, Mary Beth; Peterjohn, William T.

doi:10.1016/j.soilbio.2022.108567

Cited by 25 publications

(28 citation statements)

References 90 publications

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“…Modifications to CASA soil component parameters reduced the soil C:N ratio and total soil C stocks, again better capturing observed values (Table A2; Eastman et al, 2021Eastman et al, , 2022. In contrast, modifications to the MIMICS-CN soil parameters were needed to increase total soil C:N ratios and total C stocks, to better reflect observed values and reduce model-to-model differences (Table A3; Eastman et al, 2021Eastman et al, , 2022. After both CASA-CN and MIMICS-CN soil model parameters were calibrated to the Fernow Forest site for the end of the historic period, the models with these calibrated parameters became the "default" models that were used in experimental simulations that are the focus of this study.…”

Section: Site-specific Configuration Of Historic Simulationsmentioning

confidence: 57%

Section: Site-specific Configuration Of Historic Simulationsmentioning

confidence: 99%

“…Based on observed increases in light particulate organic matter (POM) and soil C:N ratios with N additions in the surface soil at the Fernow Forest (Eastman et al, 2022), we examined whether the distinct soil models could capture this pattern with an additional modification that reflected a reduction in soil enzyme activity with the elevated N perturbation (Fig. 1; Table 1).…”

Section: Experiments 3: Enzyme Inhibition Of Decomposition With N Add...mentioning

confidence: 99%

“…Stream inorganic N export has been monitored at the Fernow Forest from continuous streamflow measurements and weekly or biweekly streamwater chemistry samples since 1983 by the US Forest Service. Additionally, we used measurements of the partitioning of SOM into different soil density fractions in the fertilized and reference Fernow Forest watersheds to compare observed versus modelled SOM distributions and stoichiometry (Eastman et al, 2022). These mineral soil samples were collected at 20 plots per watershed, in four subplots per plot, to a depth of 15 cm.…”

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confidence: 99%

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Can models adequately reflect how long-term nitrogen enrichment alters the forest soil carbon cycle?

Eastman

Wieder

Hartman

et al. 2023

Preprint

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Abstract. Changes in the nitrogen (N) status of forest ecosystems can directly and indirectly influence their carbon (C) sequestration potential by altering soil organic matter (SOM) decomposition, soil enzyme activity, and plant-soil interactions. However, model representation of linked C-N cycles and SOM decay are not well-validated against experimental data. Here, we use extensive data from the Fernow Experimental Forest long-term, whole-watershed N fertilization study to compare the response to N perturbations of two soil models that represent decomposition dynamics differently (first-order decay versus microbially-explicit reverse Michaelis-Menten kinetics). These two soil models were coupled to a common vegetation model which provided identical input data. Key responses to N additions measured at the study site included a shift in allocation to favor woody biomass over belowground carbon inputs, reductions in soil respiration, accumulation of particulate organic matter (POM), and an increase in soil C:N ratios. The vegetation model did not capture the often-observed shift in allocation with N additions, which resulted in poor predictions of the soil responses. We modified the plant C allocation scheme to favor wood production over fine root production with N additions, which significantly improved the vegetation and soil respiration responses. To elicit an increase in the soil C stocks and C:N ratios with N additions, as observed, we also modified the decay rates of the particulate organic matter (POM) in the soil models. With all of these modifications, only the microbially explicit model captured a positive soil C stock and C:N response in line with observations. Our results highlight the importance of accurately representing plant-soil interactions, such as rhizosphere priming, and their responses to environmental change.

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Section: Site-specific Configuration Of Historic Simulationsmentioning

confidence: 57%

Section: Site-specific Configuration Of Historic Simulationsmentioning

confidence: 99%

Section: Experiments 3: Enzyme Inhibition Of Decomposition With N Add...mentioning

confidence: 99%

mentioning

confidence: 99%

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Can models adequately reflect how long-term nitrogen enrichment alters the forest soil carbon cycle?

Eastman

Wieder

Hartman

et al. 2023

Preprint

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“…The greatest differences in litter decomposition can be explained by litter quality, the soil environment and enzyme activities (Gunina et al, 2019;Lin et al, 2019;Joshi and Garkoti, 2021). Generally, highquality litter (with higher nitrogen and phosphorous contents and lower lignin/N) tends to degrade (Guo et al, 2021;Eastman et al, 2022); soil nitrogen availability can increase or decrease microbial activities and respiration rates and then influence litter nitrogen release (Ge et al, 2013;Martínez-García et al, 2021). In addition, time changes are vital for litter decomposition.…”

Section: Introductionmentioning

confidence: 99%

Litter C and N losses at different decomposition stages of Robinia pseudoacacia: The weaker effects of soil enzyme activities compared with those of litter quality and the soil environment

Su¹,

Zhu²,

Wang³

et al. 2022

Front. Environ. Sci.

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Litter decomposition promotes soil carbon and nitrogen cycling and is driven by litter quality, the soil environment and enzyme activities. The relative importance of these factors may change during the litter decomposition, however, very few studies have emphasized the temporal dynamics of these factors across plantation ecosystem, which limits our understanding of litter decomposition. To evaluate the temporal dynamic of above-mentioned litter decomposition drivers, we collected leaf and fine root litters from four different years of restoration of Robinia pseudoacacia on the Loess plateau of China and placed them on soil from the corresponding sites to incubate for 210 days. We constructed successive litter decomposition stages according to litter mass-loss interval, and we also used partial least squares path modelling (PLSPM) to evaluate the relative importance of these drivers. Our results showed that the C and N losses in leaf litter were significantly higher than those in root litter regardless of stand age. Leaf litter C and N losses increased with restoration duration, while root litter C and N showed an opposing trend with restoration duration, with the lowest levels of losses occurring at older stand ages. The initial litter quality, litter quality and the soil environment regulated leaf and root litter C loss, and enzyme activity also determined root C loss. Litter quality, the soil environment and enzyme activity influence leaf litter N loss, while root N loss was controlled by initial litter quality and the soil environment. Overall, enzyme activities had a relatively weak influence on litter C and N losses, and they impacted litter C and N losses only during the early stages. Therefore, our results revealed substantial differences in different restoration durations and litter types at the different decomposition stages, which has important significance for understanding carbon and nitrogen cycling on the Loess Plateau of China.

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Long‐term treatments alter acidification, fertility and carbon in soils of the Fork Mountain long‐term soil productivity experiment

Adams,

Rau,

Peterjohn

et al. 2024

Soil Science Soc of Amer J

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Historic atmospheric acidic deposition resulting from the combustion of fossil fuels may alter the pools of important nutrients and base cations in sensitive forest soils. This raises concern that chronic acidic deposition, particularly when coupled with intensive forest biomass harvesting, may diminish long‐term soil fertility, forest productivity, and carbon storage potential. To address these concerns, the Fork Mountain long‐term soil productivity experiment was initiated in 1996 at the Fernow Experimental Forest, West Virginia. The replicated experimental design consists of 16 plots (0.2 ha) that receive one of four treatments: (1) whole‐tree harvesting (removal of all aboveground biomass, WT plots); (2) whole‐tree harvesting + ammonium‐sulfate fertilization (WT + NS plots); (3) whole‐tree harvesting + ammonium‐sulfate fertilization + dolomitic lime (WT + NS + Lime plots); and (4) untreated reference plots. We present forest floor and soil chemistry responses after ∼25 years of treatment and evaluate the temporal changes to illuminate these results. Soil acidification has occurred, and base cation movement through the soil profile was observed, with effective cation exchange capacity increasing slightly in the deepest soil horizon by the end of the 25 years. However, some of our hypotheses were not supported. In particular, soil C did not increase over time with fertilization/soil acidification but was mainly altered by WT harvesting, as were other nutrients. Dolomitic lime provided some amelioration of acidification, but surprisingly, most of the changes in base cations appeared to be the results of Mg, not Ca, likely due to greater tree requirements and uptake of Ca.

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The path less taken: Long-term N additions slow leaf litter decomposition and favor the physical transfer pathway of soil organic matter formation

Cited by 25 publications

References 90 publications

Can models adequately reflect how long-term nitrogen enrichment alters the forest soil carbon cycle?

Can models adequately reflect how long-term nitrogen enrichment alters the forest soil carbon cycle?

Litter C and N losses at different decomposition stages of Robinia pseudoacacia: The weaker effects of soil enzyme activities compared with those of litter quality and the soil environment

Long‐term treatments alter acidification, fertility and carbon in soils of the Fork Mountain long‐term soil productivity experiment

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