Nitrogen and Sulfur Deposition Reductions Projected to Partially Restore Forest Soil Conditions in the US Northeast, While Understory Composition Continues to Shift with Future Climate Change

LeDuc, Stephen D.; Clark, Christopher M.; Phelan, Jennifer; Belyazid, Salim; Bennett, Micah G.; Boaggio, Katie; Buckley, John; Cajka, James; Jones, Phillip W.

doi:10.1007/s11270-022-05793-5

Cited by 2 publications

(1 citation statement)

References 79 publications

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“…This work is part of a large multiyear effort by the U.S. Environmental Protection Agency to better understand how forest communities may be impacted by changes in climate and atmospheric deposition (Clark et al, 2023; LeDuc et al, 2022; Phelan et al, 2016; Van Houtven et al, 2019). Similar to other studies (Van Houtven et al, 2019), a single cohort of trees was modeled, and only mean annual temperature and mean annual precipitation were included as climate predictors in our assessments (limitations of this discussed below).…”

Section: Methodsmentioning

confidence: 99%

Future climate change effects on US forest composition may offset benefits of reduced atmospheric deposition of N and S

Clark

Phelan

Ash

et al. 2023

Global Change Biology

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Climate change and atmospheric deposition of nitrogen (N) and sulfur (S) are important drivers of forest demography. Here we apply previously derived growth and survival responses for 94 tree species, representing >90% of the contiguous US forest basal area, to project how changes in mean annual temperature, precipitation, and N and S deposition from 20 different future scenarios may affect forest composition to 2100. We find that under the low climate change scenario (RCP 4.5), reductions in aboveground tree biomass from higher temperatures are roughly offset by increases in aboveground tree biomass from reductions in N and S deposition. However, under the higher climate change scenario (RCP 8.5) the decreases from climate change overwhelm increases from reductions in N and S deposition. These broad trends underlie wide variation among species. We found averaged across temperature scenarios the relative abundance of 60 species were projected to decrease more than 5% and 20 species were projected to increase more than 5%; and reductions of N and S deposition led to a decrease for 13 species and an increase for 40 species. This suggests large shifts in the composition of US forests in the future. Negative climate effects were mostly from elevated temperature and were not offset by scenarios with wetter conditions. We found that by 2100 an estimated 1 billion trees under the RCP 4.5 scenario and 20 billion trees under the RCP 8.5 scenario may be pushed outside the temperature record upon which these relationships were derived. These results may not fully capture future changes in forest composition as several other factors were not included. Overall efforts to reduce atmospheric deposition of N and S will likely be insufficient to overcome climate change impacts on forest demography across much of the United States unless we adhere to the low climate change scenario.

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Section: Methodsmentioning

confidence: 99%

Future climate change effects on US forest composition may offset benefits of reduced atmospheric deposition of N and S

Clark

Phelan

Ash

et al. 2023

Global Change Biology

Self Cite

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Geographic variation in projected US forest aboveground carbon responses to climate change and atmospheric deposition

Reese,

Clark,

Phelan

et al. 2024

Environ. Res. Lett.

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Forest composition and ecosystem services are sensitive to anthropogenic pressures like climate change and atmospheric deposition of nitrogen (N) and sulfur (S). Here we extend recent forest projections for the current cohort of trees in the contiguous US, characterizing potential changes in aboveground tree carbon at the county level in response to varying mean annual temperature, precipitation, and N and S deposition. We found that relative to a scenario with N and S deposition reduction and no climate change, greater climate change led generally to decreasing aboveground carbon (mean -7.5% under RCP4.5, -16% under RCP8.5). Keeping climate constant, reduced N deposition tended to lessen aboveground carbon (mean -7%), whereas reduced S deposition tended to increase aboveground carbon (+3%) by 2100. Through mid-century (2050), deposition was more important for predicting carbon responses except under the extreme climate scenarios (RCP8.5); but, by 2100, climate drivers generally outweighed deposition. While more than 70% of counties showed reductions in aboveground carbon relative to the reference scenario, these were not evenly distributed across the US. Counties in the Northwest and Northern Great Plains, and the northern parts of New England and the Midwest, primarily showed positive responses, while counties in the Southeast showed negative responses. Counties with greater initial biomass showed less negative responses to climate change while those which exhibited the greatest change in composition (>15%) had a 95% chance of losing carbon relative to a no-climate change scenario. This analysis highlights that declines in forest growth and survival due to increases in mean temperature and reductions in atmospheric N deposition are likely to outweigh positive impacts of reduced S deposition and potential increases in precipitation. These effects vary at the regional and county level, however, so forest managers must consider local rather than national dynamics to maximize forest carbon sinks in the future.

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Nitrogen and Sulfur Deposition Reductions Projected to Partially Restore Forest Soil Conditions in the US Northeast, While Understory Composition Continues to Shift with Future Climate Change

Cited by 2 publications

References 79 publications

Future climate change effects on US forest composition may offset benefits of reduced atmospheric deposition of N and S

Future climate change effects on US forest composition may offset benefits of reduced atmospheric deposition of N and S

Geographic variation in projected US forest aboveground carbon responses to climate change and atmospheric deposition

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