Matthew Casali and Robert Fahey Mapping temporal change in oak-dominated ecosystems in the Chicago metropolitan region Matthew Casali and Robert Fahey Forest Ecology Laboratory, Department of Research, The Morton Arboretum, Lisle, IL Oaks are a keystone species in Northeastern Illinois, driving much of the biodiversity in the region. In this region and across eastern North America oak ecosystems are in decline due to landscape-level changes such as alteration of disturbance regimes, habitat fragmentation, and urban development (Abrams 2003, Fahey et al. 2013). In addition, stand-level changes such as competition from shade- tolerant species, encroachment of invasive plant species, and lack of management or disturbance- related canopy openings have lead to widespread oak reproductive failures (Lorimer 1994, Nowacki and Abrams 2008). The goal of this project was to identify existing oak-dominated communities throughout the seven Northeastern Illinois counties of the Chicago metropolitan region (Cook, DuPage, Kane, Kendall, Lake, McHenry, and Will). The current distribution of oak-dominated ecosystems was compared spatially and temporally with records from multiple time periods dating back to the 1800s (McBride and Bowles 2007).The project provides spatially explicit information regarding the quantity and parcel size of remaining oak ecosystems, their ownership and conservation status, and relationship to drivers of change from original distribution. Introduction Results Discussion and Continuing Research Our findings indicate a significant decline in the extent of oak ecosystems from pre-settlement baselines across the region, but also high spatial variability in this landscape transition and its drivers. Estimated area of oak-dominated ecosystems declined from 782,709 acres in the 1830’s to 209,951 acres in 1939 (27% remaining), and 111,518 in 2010 (14%). The highest percentages of oak ecosystems retained in 2010 (relative to pre-settlement conditions) were found in exurban Kendall County (27%) and highly urbanized Cook County (19%) The lowest percentages of oak ecosystems retained were found in exurban McHenry County (10%) where oak ecosystems were especially dominant in the pre-settlement landscape. Conservation status also differed greatly across the region; the highest percentage of protected ecosystems was found in Cook County (82%) and the lowest in Kendall County (14%). Our findings illustrate the high degree of oak ecosystem loss and variable spatial patterns of that loss across the Chicago metropolitan region. Further data analysis from this project will illustrate the effects of patterns of urban development on landscape composition. These data will be essential in regional oak conservation efforts – including illustrating the importance of private lands and identifying high priority areas for acquisition or restoration that could create connections between existing large parcels. Table 1. Areal extent of oak ecosystems in each time period and proportion of modern ecosystems with protected status based on Green Infrastructure Maps (CMAP 2012) Oak ecosystem acreage Percentage remaining County 1830s 1939 2010 Protected (acres) % Protected Cook 119,100 34,571 22,358 29% 19% 18,369 82% DuPage 39,219 15,509 6,995 40% 18% 4,009 57% Kane 126,764 25,893 14,278 20% 11% 3,742 26% Kendall 27,516 10,879 7,440 27% 1,073 14% Lake 187,234 48,456 24,003 13% 8,494 35% McHenry 182,459 26,612 18,003 15% 10% 3,182 Will 100,417 30,028 18,441 30% 8,109 44% Total 782,709 191,948 111,518 25% 46,978 42% Figure 1. Spatial distribution of oak ecosystems in 1939 and 2010 – background shading illustrates ecosystems mapped in original landscape based on PLS notes (McBride and Bowles 2007) - green indicates forested areas. Methods Oak-dominated ecosystems were identified from pre-European settlement data,1939 aerial photography, modern soils data, and orthoimagery from 2010 and mapped using ArcGIS. The pre-European settlement data was a product of seven reports ranging from 1998 to 2005 by the Plant Conservation Lab at the Morton Arboretum (McBride and Bowles 2007). Using the 1939 aerial imagery, oak-dominated parcels were located and digitized. Probable oak dominance for each parcel was evaluated based on species data from public land survey notes, landscape position, soil data, and user interpretation of the imagery based on tone, shape, size, texture, and association. These parcels are then compared to the 2010 orthoimagery and are reshaped or removed to include only the previously existing oak communities. Figure 3. Locations of 2010 oak ecosystem parcels by protected status (CMAP 2012). Literature cited Abrams, M. D. 2003. Where has all the white oak gone? BioScience 53:927-939. Chicago Metropolitan Agency for Planning (CMAP) 2012. Refinement of the Chicago Wilderness Green Infrastructure Vision Final Report. https://www.cmap.illinois.gov/livability/open- space/green-infrastructure-vision Fahey, R.T., M. Bowles, and J. McBride. 2012. Origins of the Chicago urban forest: composition and structure in relation to pre-settlement vegetation and modern land-use. Arboriculture and Urban Forestry 38 (5).181-193 Lorimer, C. G. 1993. Causes of the oak regeneration problem. Pages 14-39 Oak Regeneration: Serious Problems, Practical Recommendations, USDA Forest Service General Technical Report SE- 84, Southeastern Forest Experiment Station, Asheville, NC. McBride, J. & Bowles, M. 2007. Pre-European Settlement Vegetation of the Chicago Region. Interactive Maps and Reports. The Morton Arboretum, Lisle, Ill. http://plantconservation.us/plspub.html Nowacki, G. J. and M. D. Abrams. 2008. The demise of fire and “mesophication” of forests in the eastern United States. BioScience 58:123-138. Acknowledgements Funding for this project was provided by USDA Forest Service State and Private Forestry, The Morton Arboretum and Chicago Wilderness. Assistance was provided by Jim Anderson, Chris Mulvaney and participants in the CW Oak Recovery Working Group. Figure 2. Spatial distribution of oak ecosystem parcels ≥100 acres in area in 1939 and 2010.