Climate Change Vulnerability Assessment for Bog Relict in Wisconsin

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1 Climate Change Vulnerability Assessment for Bog Relict in Wisconsin In 2014, the Wisconsin DNR s Natural Heritage Conservation program conducted ten vulnerability assessment workshops across Wisconsin to evaluate the potential impacts of climate change on over 50 natural communities. At one workshop, a team of conservation professionals utilized experience and published literature to assess the vulnerability of Bog Relict based on the potential impact and adaptive capacity of the ecological processes, dominant and important plant species, and stressors to the community. a Ryan O'Connor, WDNR Distribution of Bog Relict in Wisconsin based on NHI data Executive Summary Potential changes in precipitation patterns and groundwater infiltration could alter hydrologic regimes, though both floating mats and sites with abundant Sphagnum may buffer some of these potential future changes. Glossy buckthorn and non-native cat-tail are also major concerns, and will benefit from projected increases in nutrient loading of groundwater and surface water as well as longer growing seasons. Tamarack, the major tree species of Bog Relict, is projected to decline, although as a pioneer species, it has the ability to regenerate rapidly when conditions are favorable. In addition, a high diversity of native shrubs may help maintain woody structure, even if some species decline. If tamarack is lost, sites may transition to native shrub-carr or marsh, depending on local water levels. Potential Impacts: Neutral to moderately negative + Adaptive Capacity: Moderate Overall Estimated Vulnerability: Moderate to moderately high a For information on how this assessment was conducted, please see the CCVA Vulnerability Determination Process on the WICCI Plants and Natural Communities working group website.

2 Greatest Potential Impacts: Tamarack is at the southern edge of its range, is already experiencing declines, and is projected to decline further under climate change. 1, 2 In addition, tamarack is vulnerable to insects and frost damage. Potential changes to hydrology could also affect the community, but the direction of change is uncertain and could include both higher water levels due to projected precipitation increases in fall, winter and spring 3 as well as lower water levels due to increasing anthropogenic demand for groundwater resources and higher evapotranspiration rates. 3, 4 Both warmer and drier conditions generally favor shrubs like leatherleaf and bog rosemary over graminoids and bryophytes, although many bog grasses and sedges appear to tolerate warmer temperatures provided conditions stay wet. 5, 6 Non-native invasive species are a major concern, with both glossy buckthorn and non-native cat-tail likely to increase with nutrient loading of surface and 3, 7-9 groundwater, longer growing seasons, and general broad environmental tolerances. Overall, if future changes and stressors are too great, many sites may convert to shrub-carr, or, under prolonged wetter conditions, to marsh. Factors that most influence Adaptive Capacity: Depending on local site conditions, Bog Relicts may have a built-in buffer against modest changes in water levels. Sites with floating mats may naturally rise and fall with changing water tables, and sponge-like Sphagnum moss holds water, slowly releasing it during drought, and increasing growth during periods of high water. 6, 10 In addition, this community type is largely a climate relict that has already persisted through significant change, and may be somewhat resistant to modest future changes, especially if nutrient loading and water level changes are kept to a minimum. Notably, several important shrub species (e.g., leatherleaf and bog rosemary) appear to benefit from warmer conditions, 5 despite the fact that they are not found further south, 1 implying that their current range may be a function of hydrogeologic parameters rather than temperature. In addition, high species diversity may help maintain a similar structure even if particular species do decline. Although tamarack is projected to experience a decline in suitable habitat, 2 it is also a pioneer species and has the ability to regenerate rapidly when conditions are favorable, and may be able to colonize new areas within sites with more suitable habitat. Finally, although Bog Relict is uncommon and often occurs in small isolated stands, numerous remaining sites are embedded within a natural landscape, including other wetland communities, and may be buffered from stressors such as increased runoff and sedimentation from extreme storms. Key uncertainties: How will projected changes in precipitation patterns and evapotranspiration interact with future anthropogenic water use to affect long-term hydrology? What sites are the most vulnerable and which ones are the most secure? Will the early successional nature of tamarack allow it to shift to adjacent habitats if water levels rise or fall for a prolonged period of time? Several Ericaceous shrubs appear to thrive under warmer temperatures, 5, 6 however, many other important species have not been experimentally assessed. Are species that are currently near the southern edge of their range limit (e.g., poison sumac, speckled alder, bog birch, and pussy willow), sensitive to future temperature changes, or just restricted to glaciated landscapes in the Great Lake region? One study suggests that glossy buckthorn may be sensitive to a warmer climate, but also notes that no empirical evidence exists to support this assertion. 9 Will glossy buckthorn also experience a decline in suitable habitat in the future, and if so, what habitats are likely to be less suitable?

3 Climate Change Vulnerability Determination for Bog Relict in Wisconsin Low Change Scenario (PCM B1) High Change Scenario (GFDL A1FI) Potential Impacts: Neutral Moderately negative Adaptive Capacity: Moderate Moderate Overall Estimated Vulnerability: Moderate Moderately high Confidence: Medium evidence, medium agreement Participants at the Southern Wetlands workshop

4 Bog Relict Key Factors and Processes In Wisconsin, Bog Relicts occur in kettle depressions south of the tension zone, usually either in seepage basins or areas with a perched, precipitation-fed water table, usually high in the watershed. Water table is at or just below surface with constantly saturated organic soils. Sites may have a floating mat that maintains constant saturation of the root zone. Sphagnum is usually common and actively acidifies the surface, although ph deeper in the rooting zone is typically weakly minerotrophic. Maintained by relatively constant supply of groundwater, surface water, and/or precipitation. Groundwater likely supports most surface water (i.e., lake basin) sites indirectly. Periodic infestations of larch sawfly, which may have interacted with other natural disturbances to facilitate tamarack regeneration. Snow pack insulates tamarack roots from frost damage. Potential Impacts under Climate Change More frequent extreme rain events could alter hydrologic regimes, although wetlands high in the watershed may be less impacted by the averse secondary effects of extreme storm events like prolonged flooding, sedimentation, and spread of invasive species propagules. 11 If water tables drop due to increasing water withdrawals and higher rates of evapotranspiration, peat could dry, decompose, and lead to invasion by other species. Acidic bogs are projected to be highly vulnerable to climate change; 12 however peatlands with a floating mat may naturally rise and falling with changing water tables, and sponge-like Sphagnum moss holds water, slowly releasing it during drought. In addition, during long periods of low water, peat decomposes to the level of the water table, and during long periods of higher water, peat reaccumulates. 10 Groundwater recharge is projected to increase with more winter and spring rain, especially in areas with fine-grained tills, such as southeast and south central Wisconsin, 3 although rain on frozen ground may only lead to more run-off. More frequent extreme rain events could alter hydrologic regimes of precipitationdominated sites. In general, drought or inundation stress increases susceptibility of trees to pests, 13 while warmer temperatures can increase insect metabolism and feeding damage. 9 In sites invaded by glossy buckthorn, competition for light severely limits the potential for tamarack regeneration. Reduced snow pack can lead to deeper soil frost and increased tamarack mortality (Reinartz, unpublished data). Dominant/Important Species Climate Change Tree Atlas 2 Modeled change in suitable habitat from 2000 to 2100 in southern Wisconsin b Change in suitable habitat Modifying Factors 14 Model reliability Low emissions High emissions Positive Traits Negative Traits Adapt Score* tamarack High Decrease Decrease FTK COL INS 3.1 *Species with an Adapt Score of 5.3 or greater have many positive traits, higher than average adaptability and may perform better than Tree Atlas habitat suitability models project. Species with an Adapt Score between 5.2 and 3.3 have average adaptability. Species with an Adapt Score of 3.2 or lower have many negative traits, lower than average adaptability and may perform worse than Tree Atlas habitat suitability models project. b For more information on Tree Atlas, please see Explanation of Tree Atlas Model on the WICCI Plants and Natural Communities working group website.

5 In the absence of species-specific climate impact models, geographic range and edaphic requirements can be used as a surrogate to estimate the potential impacts of climate change on the following important species. Species with a wide geographic range and broad tolerance of edaphic conditions are generally anticipated to be less vulnerable to changing environmental conditions. 15 Important Shrubs, Vines, Herbs, Mosses Poison sumac (Toxicodendron vernix) Speckled alder (Alnus rugosa ssp. incana) Leatherleaf (Chamaedaphne calyculata) Labrador-tea (Rhododendron groenlandicum) Bog rosemary (Andromeda polifolia) Bog birch (Betula pumila) Pussy willow (Salix bebbiana) Silky dogwood (Cornus amomum) Red-osier dogwood (C. sericea) Few-seeded sedge (Carex oligosperma) Narrow-leaved woolly sedge (Carex lasiocarpa) Bryophytes Current Range 1 and Potential Impacts under Climate Change Ranges south though glaciated Midwest, Atlantic Coastal Plain. Shrubs generally increased in cover under drier conditions in an experimental setting. 5 Ranges south to northern IL and IN; disjunct and rare in southern IN. Ranges south to northeast IL; disjunct populations in NC & SC. Cover increased modestly under both warmer and drier conditions in an experimental setting. 5 Ranges south to southern WI. Rare in OH, PA. No change in cover observed under changes to temperature and water table in an experimental setting. 5 Ranges south to northern IL, IN. Rare in OH, PA. Cover increased under both warmer and drier conditions in an experimental setting. 5 Ranges south to northern IL, IN. Rare in IA, OH. S. bebbiana ranges south to northern IL. Ranges south to OK. Ranges south to southern IL. Ranges south to southern IL; disjunct populations in MO, AR, TN, NC, AL, MS. Graminoids generally decreased under drier conditions but increased under warmer and wetter conditions in an experimental setting. 5 Ranges south to north-central IL and IA. Cover decreased under drier conditions but increased under warmer and wetter conditions in an experimental setting. 5 Distribution varies by species. Sphagnum productivity increased under wetter conditions 6 but cover decreased slightly with warmer conditions 5 in an experimental setting. Stressors/Threats Non-native invasive cat-tail Invasive shrubs (glossy buckthorn) Nutrient enrichment of groundwater Sedimentation from surrounding agricultural and developed areas. Pests and diseases (e.g., larch sawfly, larch case bearer) Overuse of groundwater resources Hydrologic disruption (roads, etc.) Potential Changes to Stressors/Threats under Climate Change Some invasive species may have increased productivity with increasing CO 2 and reduced snowpack. 8 New invasives are likely to arrive. If water tables drop, shrubs generally increase. 5 Abundant seed production and dispersal combined with broad environmental tolerances allow invasive shrubs to take advantage of altered hydrology and tolerate rapid changes. 9 Nutrient enrichment is likely to increase in agricultural areas with shallow groundwater tables, such as southeast Wisconsin, 3 which favors cat-tail. 7 More frequent storms could increase sedimentation from overland flow. In general, drought or inundation stress increases susceptibility of trees to pests, 13 while warmer temperatures can increase insect metabolism and feeding damage. 9 If groundwater withdrawals increase due to increasing demand, water tables could be lowered, but impacts likely will be basin-specific. 4 New road construction through bogs seems unlikely, but sites with already impacted hydrology will likely be less resilient to further changes.

6 References 1 Kartesz, J.T The Biota of North America Program (BONAP) North American Plant Atlas. Accessed June 20, Iverson, L.R., A.M. Prasad, S.N. Matthews, and M. Peters Estimating potential habitat for 134 eastern U.S. tree species under six climate scenarios. Forest Ecology and Management 254 (3): Wisconsin Initiative on Climate Change Impacts [WICCI] Water Resources Working Group Report. Nelson Institute for Environmental Studies, Universty of Wisconsin-Madison and the Wisconsin Department of Natural Resources. Madison, WI. 4 Eheart, J.W., and D.W. Tornil Low flow frequency exacerbation by irrigation withdrawals in the agricultural midwest under various climate change scenarios. Water Resources Research 35 (7): Weltzin, J.F., S.D. Bridgham, J. Pastor, J. Chen, and C. Harth Potential effects of warming and drying on peatland plant community composition. Global Change Biology 9 (2): Weltzin, J.F., J. Pastor, C. Harth, S.D. Bridgham, K. Updegraff, and C.T. Chapin Response of Bog and Fen Plant Communities to Warming and Water-level Manipulations. Ecology 81 (12): Kercher, S.M., and J.B. Zedler Flood tolerance in wetland angiosperms: a comparison of invasive and noninvasive species. Aquatic Botany 80: Ryan, M.G., and J.M. Vose Effects of climatic variability and change. Pp in J.M. Vose, D.L. Peterson and T. Patel- Weynand (Eds.), Effects of climatic variability and change on forest ecosystems: a comprehensive science synthesis for the U.S. Forest sector. U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. Portland, OR. 9 Dukes, J.S., J. Pontius, D. Orwig, J.R. Garnas, V.L. Rodgers, N. Brazee, B. Cooke, K.A. Theoharides, E.E. Stange, and R. Harrington Responses of insect pests, pathogens, and invasive plant species to climate change in the forests of northeastern North America: What can we predict? Canadian Journal of Forest Research 39 (2): Dise, N.B Peatland response to global change. Science 326 (5954): Zedler, J.B How frequent storms affect wetland vegetation: a preview of climate-change impacts. Frontiers in Ecology and the Environment 8 (10): Essl, F., S. Dullinger, D. Moser, W. Rabitsch, and I. Kleinbauer Vulnerability of mires under climate change: implications for nature conservation and climate change adaptation. Biodiversity and Conservation 21 (3): Wisconsin Initiative on Climate Change Impacts [WICCI] Wisconsin's Changing Climate: Impacts and Adaptation. Nelson Institute for Environmental Studies, University of Wisconsin-Madison and the Wisconsin Department of Natural Resources. Madison, WI. 14 Matthews, S.N., L.R. Iverson, A.M. Prasad, M.P. Peters, and P.G. Rodewald Modifying climate change habitat models using tree species-specific assessments of model uncertainty and life history factors. Forest Ecology and Management 262: Thuiller, W., S. Lavorel, and M.B. Araújo Niche properties and geographical extent as predictors of species sensitivity to climate change. Global Ecology and Biogeography 14 (4):

7 Southern Wetlands Workshop Participants Workshop Date: October 9, 2014 Location: Milwaukee, Wisconsin Tom Bernthal Quentin Carpenter Dan Carter Don Reed Jim Reinartz Alice Thompson Pat Trochlell Dreux Watermolen Matt Zine WDNR-Water Quality University of Wisconsin-Madison Southeastern Wisconsin Regional Planning Commission Southeastern Wisconsin Regional Planning Commission University of Wisconsin-Milwaukee Thompson & Associates WDNR-Watershed WDNR-Science Services WDNR-Natural Heritage Conservation Facilitators: Ryan O Connor Amy Staffen WDNR-Natural Heritage Conservation WDNR-Natural Heritage Conservation dnr.wi.gov WICCI.WISC.EDU Suggested Citation: Wisconsin Initiative on Change Impacts [WICCI] Climate Vulnerability Assessments for Plant Communities of Wisconsin. Wisconsin Initiative on Climate Change Impacts, Madison, WI.