| This dissertation quantified the effects of two disturbances on the composition and structure of the northern hardwood forest. The short-term impacts of a rare ice storm were measured at the Hubbard Brook Experimental Forest (Woodstock, NH). I assessed canopy damage using leaf area index and visual damage class assessments and monitored canopy recovery for three growing seasons following the storm. Canopy cover reached pre-disturbance levels within three years. Long-term impacts of the storm will be the result of disturbance interactions. Forest stands harvested 24--28 years prior to the storm will experience accelerated succession to shade-tolerant species (e.g. Fagus grandifolia Ehrh., Acer saccharum Marsh., and Betula alleghaniensis Michx. F.). Because of the high density of advance regeneration from beech bark disease and root sprouting potential in ice-damaged beech (Fagus grandifolia Ehrh.), older stands (60--120 y) will see an increase in beech abundance as a result of the storm.; I also determined whether or not reforested pastures follow the same successional patterns as land with a history of logging and explored possible recruitment mechanisms explaining these patterns. By doing so, I questioned the legitimacy of applying successional models based on clearcutting to the entire northern hardwood forest. Pasturing was at one time the dominant disturbance on the landscape. By comparing the composition and age structure of reforested pastures to non-grazed, non-cleared woodlots, I quantified the impacts of pasturing on the composition and structure of post-abandonment forests. While structurally similar, the composition of reforested pastures is vastly different from the composition of woodlots and this difference is due to recruitment patterns. While woodlots are dominated by the classic northern hardwood species (e.g. Fagus grandifolia Ehrh., Acer saccharum Marsh.), and Betula alleghaniensis Michx. F.), pastures are dominated by Picea rubens Sarg., Abies balsamea L., Acer rubrum L., and Populus spp. The northern hardwood forest is not a uniform forest, but is comprised of at least two forest types: one originating after logging, and one originating after pasturing. This legacy of pasturing will endure at least another 100--200 years, but future disturbances will determine if reforested pastures ever converge on the northern hardwood composition. |
