The effects of accelerated soil acidification on aggrading temperate deciduous forests: The Fernow Experimental Forest Long Term Soil Productivity (LTSP) Study at 13 years.

摘要

Many temperate forests in the Eastern US are young and have experienced decades of elevated inputs of acidic compounds from the atmosphere. As a result, I used the Fernow Experimental Forest Long Term Soil Productivity (LTSP) experiment near Parsons, WV to determine how ongoing acidic deposition may affect total ecosystem carbon (C) storage, stand level dynamics, and soil and foliar chemistry in a young regrowing temperate deciduous forest. I also assessed the potential for acidic deposition effects to cascade up into higher trophic levels through its effects on a soil invertebrate. The LTSP experiment is a randomized block design in which ammonium sulfate is experimentally added to the soil in order to accelerate the acidification of forest soils in a way that is similar to the effects of long-term nitrogen (N) deposition from the atmosphere.;I found that 13 years of ammonium sulfate additions to a regenerating deciduous forest stimulated its ability to store C. This response was driven primarily by increased C storage in aboveground biomass and to a lesser extent by increased C stored in the forest floor. Despite the dominance of a single tree species, the overall response was a complex mixture of species-specific changes in the growth of individuals that may have been tempered by changes in stand density. I also found that after 10 years of growth with continual N and S additions, soil and foliar chemistry in an aggrading temperate deciduous forest show signs of soil acidification and calcium (Ca) and magnesium (Mg) depletion -- suggesting that the ability of these regenerating forests to store C may diminish if acidification were to continue. Additionally, I found that liming may mitigate some of the negative impacts of acidification for experimental or management purposes. Finally, I also found that Pseudopolydesmus serratus millipedes, leaf litter processing invertebrates that contain high levels of Ca, are negatively affected by 13 years of simulated acidic deposition in temperate deciduous forests. The negative effect of N addition on millipede populations, however, could not be tied to a depletion of Ca from the soil and plants but, if widespread, could affect the Ca supply to organisms, like some bird species, that have high Ca requirements during critical stages in their life.;Overall, this research suggests that young regrowing temperate deciduous forests may currently be sequestering more C due to inputs of N from acidic deposition. However, the positive response may involve species specific and stand-level changes and may be short-lived due to soil acidification effects, which should proceed, or co-occur with, reductions in growth rates. The effects of N deposition may also potentially reach higher trophic levels such as consumers of P. serratus, whose populations were negatively affected by N inputs.