Gary M. Lovett
Institute of Ecosystem Studies

Collaborators:
Gary M. Lovett, Institute of Ecosystem Studies
Kathleen C. Weathers, Institute of Ecosystem Studies
Mary A. Arthur, University of Kentucky
Ross D. Fitzhugh, University of Illinois
Pamela A. Templer, University of California-Berkeley
Jacob Griffin, Institute of Ecosystem Studies (Graduate Student/ Research Assistant)
Brent Mellen, Institute of Ecosystem Studies (Research Assistant)
Jessica Hancock, University of Kentucky (Research Assistant)

This project is primarily focused on understanding the ecology and nutrient cycling of Catskill forests and the responses of the forests to stresses such as air pollution and introduced pests. For references to papers cited here, see our Catskill project publication list.

Patterns of Atmospheric Deposition

Because of their relatively high elevations and their proximity to sources of pollution on the east coast and in the Midwest, the Catskill Mountains receive among the highest rates of sulfur and nitrogen deposition in the Northeast (Ollinger et al 1993). We have found that high-elevation ecosystems of the mountains receive higher rates of precipitation, dry deposition (particles and gases) and cloud water deposition than low-elevation areas (Weathers et al. 2000, Lovett et al. 1999). Forest edges at high elevation are particularly exposed to pollutant deposition, and may receive up to four times the pollutant load of forests at low elevations (Weathers et al. 1995, Weathers et al. 2000).

Controls on Nitrogen Loss from Forested Watersheds

Small forested watersheds in the Catskills can vary up to 17-fold in the concentration of nitrate in streamwater (Lovett et al. 2000). This is important because nitrate is a significant acidifying agent in the streams, and can cause harmful algal bloom when it is delivered to downstream estuaries and coastal waters. We are investigating the cause of nitrate variation through comparative studies in Catskill watersheds. Most of the variance in watershed nitrate export can be explained by the carbon to nitrogen ratio (C:N) of the watershed soils, and this ratio appears to be mainly controlled by the tree species composition of the watershed (Lovett et al. 2002).

Sugar maples, in particular, seem to create soils with a low C:N ratio, which leads to high rates of nitrate release to stream water, while soils under red oak and eastern hemlock have higher C:N ratios and lower nitrate release (Lovett et al 2004, Lovett and Mitchell 2004). Other factors may also inhibit nitrate production under oak soils, such as abiotic retention of nitrogen (Fitzhugh et al. 2003a and 2003b). Increasing accumulation of nitrogen in the soils from continued atmospheric deposition may result in decreased ability of oak forest soils to retain nitrogen (Templer et al. 2005).

Effects of the beech bark disease on Catskill forests

The beech bark disease is caused by a combination of a scale insect and a fungus, which was introduced to North America from Europe. The insect penetrates the bark of the trees to feed, and the tiny holes it leaves behind allow the fungus to become established. One infected with the fungus, most trees die. The disease affects nearly every beech tree in the Catskills, and it is especially prevalent in the mid-elevation forests (Griffin et al 2003). One of the effects of the disease may a reduction in the Catskill's beech population; resulting in an increase in beech's major competitor, sugar maple. We are working on a study of stands that span a gradient- from healthy mixed beech-maple forest to stands where once-dominant beech trees have succumbed to beech bark disease and been replaced by maples. One of our recent findings in this study is that, as the percentage sugar maple in the stands increases across this gradient, the amount of nitrification (nitrate production) also increases (see graph below).