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The Effects of Climate Change on Silver Maple-Dominated Riparian Zones in the Lake Champlain Basin ENSC 202: Ecological Risk Assessment and Management Spring 2009 Wetland, Woodland, Wildland Nicole Baldwin • Kelly Hunt • Emily Melander • Meredith Simard Table of contents Problem Statement Importance of riparian buffers Projections for climate change Case study: effects on silver maple-dominated systems Conclusions & Recommendations Problem Statement Projected changes in precipitation, seasonal transitions, and annual temperatures due to climate change will affect the composition and structure of the silver maple dominated riverine floodplain forests, a common riparian forest type in the Lake Champlain watershed. Importance of a Riparian Buffer Water Quality Value of Vegetation Phosphorus uptake Sediment Removal via root systems Buffer Zone Width Buffer Zone Width Concentration of various particle sizes and runoff Particles were found to be coarser in runoff in winter as opposed to summer Syversen, N, Borch, H. (2005) Phosphorus Uptake Decrease in total P and Suspended Solids with increase in buffer width Particle size of soil is also a factor in P adsorption Syversen, N, Borch, H. (2005) Shading With complete shading algae blooms can be reduced by up to 44.2%, especially during warmer months Ghermandi et al. 2009 Disturbance: Flooding Threat of invasive species Vegetation Richness Residence time A longer residence time allows for better flood control and increased nutrient uptake Nutrient uptake Potential Marti et al. Wildlife Habitat Soil Stability Compaction of soil via root systems help to keep erosion at a minimum Climate change in Vermont Four factors of climate change will have the largest effects on Riparian areas Frost depths Ice storms Seasonal shifts/ bud break Flooding regimes View of Mount Mansfield Reduced snow cover and Frost depth Increased precipitation in winter will likely consist of rain. NECIA (2006) predicts ¼ fewer snow covered days during the winter Decrease in snow will likely increase frost depth due to exposed ground and cold temperature “Migrating Climate” Precipitation patterns in Winter are shifting from early to late in the season Vermont climate is predicted to trend towards more southern states as temperatures increase NECIA (2006) predicts more rain and less snow, this will likely turn into freezing rain Ice storms Defined by the National Weather Service as 0.25 inches of ice found on exposed surfaces Freezing rain and sleet which result in ice storms are due to warm fronts during winter months which become sandwiched between cold air (Gay & Davis, 1993) Shifts in seasons Indicators of Seasonal changes: First leaf and first bloom dates Average number of growing days Length of growing season Increased temperatures will result in a longer growing season Flood Regimes Increase in overall annual discharge Increased winter flows Earlier spring peak flows Decreased summer flows Caused by Increased precipitation Changes in river geomorphology and water catchment due to urbanization and agriculture Silver Maple-Dominated Riparian Forest Systems Snow cover and Frost depth Fine roots High surface area essential for nutrient retention. Compete with microbes for nutrients, primarily nitrogen. Spring is time of greatest nutrient loss Microbes mineralize and nitrify before development of and uptake by fine roots Disruption in production of fine roots can enhance nutrient loss Snow Cover and Frost Depth • Enhanced mortality and turnover of fine roots on sites with snow removal • Elevated levels of nitrification, NO3• Increased loss of N and P • Disruption in timing of nutrient availability and uptake Tierney et al., 2001 Implications Reduced ability to uptake nutrients in spring Increased E expenditure to re-grow fine roots Limits above-ground growth Limits ability to withstand disturbances Short-term: More snags, DWD Long-term: Transition to low, multi-layered canopy Increasingly nutrient-rich run-off Increased Frequency of Ice Storms: Susceptibility to ice damage Extent of ice damage determined by: Branch geometry Fine twigs and branches Horizontal branching Silver maple characteristics Significant branching = increased surface area Slender lateral branches = limited strength Hard, but brittle = easily damaged Hopkin et al., 2003 Implications Ice storms are major disturbance regime that will be enhanced by climate change Injured trees more likely to suffer long-term damage Increased mortality of older trees, roots Reduced demand for water and nutrients by aboveground biomass Long-term trend toward younger stand age Increased overland flow and nitrification rates Dormancy and Bud Break Three Indicators of Seasonality First leaf and first bloom dates Average number of growing degree days Length of growing season Successful Budding in the Spring Need three periods of dormancy Ecodormancy Endodormancy Paradormancy Initiation of Dormancy Shorter photoperiods Colder Temperatures* Insufficient moisture* Implications Delayed and insufficient endodormancy may postpone time of bud break and resumption of tree growth in spring Climate change may prevent the trees to achieve their chilling requirement Change in budding times can alter food webs Alteration of Flooding Regime Possible Future Flooding Regime 1 – Increased Winter Flows 2 – Earlier, more gradual rising limb 3 – Earlier Spring Peak Flows 4 – Decreased Summer Flows Changes in Seasonality Stream flow Increase in late winter flow won’t stress Silver maples too much Change in ice flow patterns could result in less suitable area for seedlings to germinate Advancement of spring peak flow may allow seedlings to germinate earlier Less summer flow will cause an increase stress for older and young trees Conclusions Change in silver maple-dominated riparian forest structure and composition Younger, multi-layered stand Encroachment of upland species Species shift Reduced competitive ability of silver maple Replacement of northern hardwoods with southern assemblages of oak, pine, red maple, aspen Recommendations Currently, restoration efforts are general and require future management A knowledge and awareness of the predicted change in species composition is important for land managers and riparian restorationists. A change in the ability of the native silver maples to survive and compete may require a transition away from traditional restoration species to those that are predicted to thrive in the projected climate of the northeast in the next century.
