UVM Theses and Dissertations
Format:
Print
Author:
Comerford, Daniel
Dept./Program:
Natural Resources
Year:
2011
Degree:
MS
Abstract:
Climate projections for the northeastern U.S. predict an increase in air temperatures and precipitation. The precipitation is projected to accumulate as rain rather than snow. This combination of changes in climate may result in reduced forest snowpack, thereby decreasing thermal buffering of the forest floor. The effects of increased soil frost on tree physiology and insect communities are not clearly understood. To evaluate the potential physiological response of sugar maple (Acer saccharum Marsh.) to a reduced snowpack, I measured root injury, foliar elemental composition, and midsummer canopy carbohydrate concentrations of 24 trees in a snow manipulation experiemnt at the Hubbard Brook Experimental Forest (HBEF). Snow was removed from treatment plots for two consecutive winters, resulting in significantly lower soil temperatures to a depth of 50 cm for both winters compared to reference plots with an undisturbed snowpack. Visibly uninjured roots from sugar maple trees in the snow removal plots had significantly higher (but sub-lethal) relative electrolyte leakage (REL) than trees in the reference plots. Foliar calcium (Ca):aluminum (Al) molar ratios were significantly lower and Al concentrations were significantly higher in trees from the snow removal plots than trees from the reference plots. Snow removal significantly increased mid-summer foliar starch concentrations.
I evaluated the response ofground dwelling insect populations to decreased snowpack because they provide critical ecosystem services and are highly susceptible to changes in temperature. Insect response was also assessed relative to vegetation manipulation -a well-established perturbation to insect populations. Treatments included four vegetation removal, vegetation and snow-removal, and reference plots (each 13 x13 m²) at the HBEF. Significantly fewer total insects were found in the undisturbed reference plots compared with the treatment plots. Significantly fewer individuals of one snail-predating insect genus, Sphaeroderus spp., were found in the vegetation and snow removal plots than in the vegetation removal plots. These results suggest that for the northeastern U.S., the presence of understory vegetation has a greater impact than the presence of a snowpack on ground dwelling insect populations.
The results of both tree and insect analyses are consistent with previous research implicating soil freezing as a cause of soil acidification that leads to cation imbalances in the soil. Elevated Al concentrations in sugar maple foliage from the snow removal plots could be driven by an increase in soil acidity that mobilized pools of soil Al. Decreased populations of Sphaeroderus spp. on the snow removal plots could be caused by decreased abundance of their prey. Snails and other gastropods have a critical need for Ca and can be adversely affected by the decreased Ca availability that often accompanies soil acidification. Increased soil freezing due to a reduction in snowpack could exacerbate soil cation imbalances already caused by acidic deposition and have widespread implications for forest health.
I evaluated the response ofground dwelling insect populations to decreased snowpack because they provide critical ecosystem services and are highly susceptible to changes in temperature. Insect response was also assessed relative to vegetation manipulation -a well-established perturbation to insect populations. Treatments included four vegetation removal, vegetation and snow-removal, and reference plots (each 13 x13 m²) at the HBEF. Significantly fewer total insects were found in the undisturbed reference plots compared with the treatment plots. Significantly fewer individuals of one snail-predating insect genus, Sphaeroderus spp., were found in the vegetation and snow removal plots than in the vegetation removal plots. These results suggest that for the northeastern U.S., the presence of understory vegetation has a greater impact than the presence of a snowpack on ground dwelling insect populations.
The results of both tree and insect analyses are consistent with previous research implicating soil freezing as a cause of soil acidification that leads to cation imbalances in the soil. Elevated Al concentrations in sugar maple foliage from the snow removal plots could be driven by an increase in soil acidity that mobilized pools of soil Al. Decreased populations of Sphaeroderus spp. on the snow removal plots could be caused by decreased abundance of their prey. Snails and other gastropods have a critical need for Ca and can be adversely affected by the decreased Ca availability that often accompanies soil acidification. Increased soil freezing due to a reduction in snowpack could exacerbate soil cation imbalances already caused by acidic deposition and have widespread implications for forest health.