UVM Theses and Dissertations
Format:
Print
Author:
Engel, Benjamin James
Dept./Program:
Natural Resources
Year:
2014
Degree:
MS
Abstract:
Acidic deposition depletes cations such as calcium (Ca) from forest soils and has been linked to the decline of red spruce (picea rubens Sarg.) trees in the northeastern United States. To better understand the spatial nature of the connection between Ca depletion and tree health and productivity, we used data from an existing geographically-referenced, steady-state model for New England and New York that produces fine scale (30 m) maps of critical loads (the capacity of a site to tolerate pollution) and exceedance (amounts to which incoming pollution exceeds the critical load) estimates for forests. We examined how woody growth (i.e., xylem basal area increment) of dominant and co-dominant red spruce trees within Vermont and New Hampshire is related to modeled estimates of critical loads and exceedance. This comparison was done by examining patterns of growth in red spruce xylem increment cores from sites with a wide range of modeled critical loads and exceedance levels.
Exceedance was associated with average growth for the study period (1950-2010) overall, and for the 1970s and 1980s when acid deposition was at its highest, whereas critical load was associated with growth only for the most recent decade (2001-2010). An analysis of the rebound in growth from the region-wide 2003 red spruce winter injury event found the exceedance was linked with growth rebound both overall (2003-2010), as well as annually from 2006-2010, while critical load was not related to this rebound. Regression analyses found similar results, and may indicate potential linear modeled critical load and exceedance estimates can help account for tree growth, variability and rebound from injury in the field, and that dendrochronological analysis may help infuse a temporal component to steady state critical load models that otherwise lack this context. Recent growth for red spruce exceeds average growth over loading in the region. The cause of this recent surge in red spruce growth is currently unknown.
Exceedance was associated with average growth for the study period (1950-2010) overall, and for the 1970s and 1980s when acid deposition was at its highest, whereas critical load was associated with growth only for the most recent decade (2001-2010). An analysis of the rebound in growth from the region-wide 2003 red spruce winter injury event found the exceedance was linked with growth rebound both overall (2003-2010), as well as annually from 2006-2010, while critical load was not related to this rebound. Regression analyses found similar results, and may indicate potential linear modeled critical load and exceedance estimates can help account for tree growth, variability and rebound from injury in the field, and that dendrochronological analysis may help infuse a temporal component to steady state critical load models that otherwise lack this context. Recent growth for red spruce exceeds average growth over loading in the region. The cause of this recent surge in red spruce growth is currently unknown.