The Question

What are the interactive effects of soil acidity and phosphorus availability on forest health?

Project Summary

Acid precipitation, resulting from burning of fossil fuels, is a chronic problem in areas near population centers or concentrations of industrial activity. The northeastern United States is one area that historically has received particularly high levels of acid precipitation. The resulting ecosystem acidification can impact plants, soils, and water. In hardwood forests, such as those common in Northeast Ohio, there is concern that long-term acidification of forests can decrease the availability of essential nutrients such phosphorus and calcium in soil, which could result in poor forest health and forest decline. In 2009, Holden scientists received funding from the National Science Foundation to study the interacting effects of soil acidity and phosphorus availability in deciduous hardwood forests. The soils of forested plots at Holden and Squire Valleevue and Valley Ridge Farms (Case Western Reserve Universities Experimental Farm) were manipulated to increase soil pH and fertility using crushed limestone (lime) and phosphorus fertilizer, respectively. Since these applications, we have been studying the long-term effects of this reversal of soil acidification and addition of phosphorus on forest plants, including trees and native wildflowers, and belowground organisms, including fungi and bacteria. We have conducted several studies on mycorrhizal fungi, as these plant symbionts are important for forest health. This study has shown the importance of belowground organisms for freeing up nutrients bound in organic matter and the importance of mycorrhizal fungi for acquiring nutrients for their plant hosts in acidic, nutrient poor conditions. Ongoing work is investigating the long-term effects of the lime and phosphorus applications on tree growth and allocation.

Keywords

Microbiome, mycorrhizae, forest, pH, phosphorus, NSF, soil