Ecological characteristics of floodplain forest reference sites in the Upper Mississippi River System
Introduction
Historical and present day disturbances have contributed to long-term changes in the composition and structure of Upper Mississippi River System (UMRS) floodplain forests (Nelson and Sparks, 1998, Yin, 1998, USGS, 1999). Floodplain forest coverage has been significantly reduced from pre-settlement levels due to timber harvesting, conversion to agricultural cropland, and other land use changes (Nelson et al., 1994, Yin et al., 1997, Knutson and Klaas, 1998, Kruse and Groninger, 2003, Johnson and Hagerty, 2008, De Jager et al., 2013a). Hydrology is recognized as a primary driver of ecological processes in large river ecosystems (Junk et al., 1989, Hodges, 1997, Theiling and Burant, 2012), and contemporary floodplain forests are affected by altered hydrological regimes associated with river impoundment (Yeager, 1949, Yin et al., 2009, Theiling and Nestler, 2010, De Jager et al., 2012, Kenow et al., 2016). A corresponding loss of tree species diversity has been identified as a management concern in the UMRS (Romano, 2010, Sparks, 2010, Guyon et al., 2012). A general lack of successful tree regeneration, particularly the hard mast component, has also been documented in many areas (Battaglia et al., 2002, Battaglia et al., 2008, Thomsen et al., 2012, De Jager et al., 2013b). Further losses in floodplain forest habitat and diversity over time are likely unless active forest management can reverse this trend (Urich et al., 2002, Guyon et al., 2012). Consequently, floodplain forest restoration is a prominent ecological and management goal in Mississippi River floodplain ecosystems (Twedt and Best, 2004, Wilson et al., 2005, Allen, 1997, Heitmeyer, 2008, Yin et al., 2009).
The use of reference sites as targets for ecological restoration efforts is well documented (Allen et al., 2000, SER (Society for Ecological Restoration International Science Policy Working Group), 2004, Nestler et al., 2010, Pruitt et al., 2013, Balaguer et al., 2014). Assessing the biological and physical characteristics of remnant high quality UMRS floodplain forests will establish a suite of baseline ecological information for specific reference sites that will in turn inform potential restoration activities. However, the relationship between various environmental factors that affect ecosystem functionality in floodplain forests and the response of vegetation communities to long-term changes in those factors remain unclear (Gergel et al., 2002). In addition, restoration to historical reference conditions may not be feasible in many locations because the conditions under which mature floodplain forest reference sites were established may no longer exist (Stanturf et al., 2001). For example, maintenance of high water levels immediately upriver of locks and dams (Theiling and Burant, 2012) likely inhibits the successful regeneration of less flood tolerant taxa (e.g., Quercus spp.) that may have been present in those locations historically or even still inhabit them today as advanced members of the overstory. These hydrologic changes have also been linked to the increasing dominance of the flood-tolerant Acer saccharinum (Nelson and Sparks, 1998, Yin et al., 2009, Romano, 2010, De Jager et al., 2012).
Contemporary floodplain forest reforestation efforts may therefore be better guided by a more functional and dynamic assessment and classification of present day UMRS ecosystems that begins to align potential vegetation communities and even individual species with environmental reference conditions that exhibit spatial and temporal variability (Comer et al., 2003, Klimas et al., 2009, Nestler et al., 2010, Hiers et al., 2012, Kirkman et al., 2013). With this approach, the ability of native species to tolerate present conditions would likely be more informative for plantings than whether or not they are known to have inhabited a particular area historically. Furthermore, assessing correlations between contemporary environmental conditions and successful natural regeneration is important in determining requirements for establishment of targeted tree species in the modern floodplain (Kabrick and Dey, 2001, Gardiner et al., 2004). At any rate, tree plantings in floodplains have often met with mixed results (Stanturf et al., 2001, Dey et al., 2003, Grossman et al., 2003), and refining methods to assess site quality and suitability for plantings would benefit restoration efforts in the UMRS.
The objective of this project was to assess the physical and biological characteristics of representative floodplain forest communities in the UMRS, thereby establishing a suite of baseline ecological reference sites that will inform ongoing and future floodplain forest restoration efforts. From a management perspective, identifying a set of environmental variables significantly correlated to the occurrence of particular vegetation types would benefit agencies responsible for restoring bottomland hardwoods and other vegetation communities in the UMRS. We hypothesized that elevation, soil texture, canopy cover, and a set of hydrologic variables would be significant drivers of community composition and structure in UMRS floodplain forest ecosystems. These variables also tend to be readily accessible or measurable in site-specific locations across the UMRS, and could be used to streamline preliminary site assessments by resource managers seeking to reestablish or restore vegetation as part of an environmental management program. This project therefore aims to facilitate future restoration efforts by contributing to the development of methods to evaluate potential restoration sites based on assessments of vegetation, hydrology, elevation, soils, and canopy conditions.
Section snippets
Study sites
Fourteen reference sites were selected for the study. Nine of these were located along a ∼1140 km longitudinal reach of the Upper Mississippi River, two along the lower Illinois River, one along the lower Big Muddy River, and two in the Cache River watershed in southern Illinois (Fig. 1). Five separate locations in the northernmost part of the study area were combined into one Upper Mississippi River reference site for analysis due to the limited number of sample plots at several locations.
Overstory composition & structure
Species richness and diversity were generally highest in the lower Illinois River and southern Illinois sites (Table 1). Average overstory species richness across the study was 12.9 and diversity indices varied from a low of 1.25 at Lost Mound to a high of 3.95 at Cypress Creek. Overall, silver maple (Acer saccharinum) was by far the most dominant overstory species recorded in the study (Table 2). Other overstory species with relatively high study-wide importance values included green ash (
Discussion
A general decline in tree species diversity, particularly the hard mast component, is a notable management concern in UMRS floodplain forests (Yin et al., 2009, Sparks, 2010, Guyon et al., 2012). For example, many UMRS floodplain forests have been increasingly dominated by stands of silver maple since pre-settlement times (Nelson and Sparks, 1998, Yin, 1998, Romano, 2010, De Jager et al., 2013a). Compounding this trend, a general lack of hard mast regeneration has been documented in a number of
Conclusions
Multivariate community ordination, coupled with vector fitting, enabled us to identify a set of significant, explanatory variables that provide insight into overall community structure in Upper Mississippi River System floodplain forests. The next steps involve incorporating this information into models and decision support systems designed to guide future restoration efforts at local and/or regional scales. However, further study is needed to accurately target individual species to within-site
Acknowledgements
The authors would like to thank the United States Army Corps of Engineers Upper Mississippi River Restoration Long Term Resource Monitoring element for funding this research. We are also grateful to Megan Cosgriff and numerous undergraduate and graduate students who assisted with data collection in the field and sample processing in the laboratory.
References (63)
- et al.
The historical reference in restoration ecology: re-defining a cornerstone concept
Biol. Conserv.
(2014) - et al.
Oak regeneration in bottomland hardwood forests
For. Ecol. Manage.
(2008) - et al.
Threshold effects of flood duration on the vegetation and soils of the Upper Mississippi River Floodplain, USA
For. Ecol. Manage.
(2012) - et al.
Interactive effects of flooding and deer (Odocoileus virginianus) browsing on floodplain forest recruitment
For. Ecol. Manage.
(2013) Development and ecology of bottomland hardwood sites
For. Ecol. Manage.
(1997)- et al.
Patterns of forest succession and impacts of flood in the Upper Mississippi River floodplain ecosystem
Ecol. Complexity
(2009) Reforestation of bottomland hardwoods and the issue of woody species diversity
Restor. Ecol.
(1997)- Allen, J.A., Keeland, B.D., Stanturf, J.A., Clewell, A.F., Kennedy Jr., H.E., 2000 (revised 2004). A guide to...
- et al.
Sixteen years of old-field succession and reestablishment of a bottomland hardwood forest in the Lower Mississippi Alluvial Valley
Wetlands
(2002) - et al.
Quercus michauxii regeneration in and around aging canopy gaps
Can. J. For. Res.
(2004)
Response of floodplain forest species to spatially condensed gradients: a test of the flood-shade tolerance tradeoff hypothesis
Oecologia
Evaluating dispersal limitation in passive bottomland forest restoration
Restor. Ecol.
Floodplain forest response to large-scale flood disturbance
Trans. Illinois State Acad. Sci.
On the integrated interpretation of indirect site ordinations: a case study using semi-arid vegetation in southeastern Spain
Vegetatio
Effects of flood frequency and duration on the allometry of community-level stem size-density distributions in a floodplain forest
Am. J. Bot.
Past and predicted future changes in the land cover of the Upper Mississippi River floodplain, USA
River Res. Appl.
The Upper Mississippi River floodscape: spatial patterns of flood inundation and associated plant community distributions
Appl. Veg. Sci.
Species assemblages and indicator species: the need for a flexible asymmetrical approach
Ecol. Monogr.
Consequences of human-altered floods: levees, floods, and floodplain forests along the Wisconsin River
Ecol. Appl.
Restoration of hard mast species for wildlife in Missouri using precocious flowering oak in the Missouri River floodplain, USA
Agrofor. Syst.
Upper Mississippi River Systemic forest stewardship plan
United States Army Corps Eng.
Flooding alters apparent position of floodplain saplings on a light gradient
Ecology
Emerald ash borer invasion of North America: history, biology, ecology, impacts, and management
Annu. Rev. Entomol.
The dynamic reference concept: measuring restoration success in a rapidly changing no-analogue future
Ecol. Restor.
Cited by (16)
Species and landscape variation in tree regeneration and 17 years of change in forested wetlands invaded by emerald ash borer
2024, Forest Ecology and ManagementThreats, biodiversity drivers and restoration in temperate floodplain forests related to spatial scales
2023, Science of the Total EnvironmentCitation Excerpt :This contributes to higher biogeographical and evolutionary differences between river catchments and, at the same time, to greater similarity within them. But even within a river catchment, processes such as species habitat filtering associated with changing river dynamics, nutrient levels and disturbance regimes lead to highly diverse habitats and so to species diversity (Lytle and Merritt, 2004; Turner et al., 2004; Guyon and Battaglia, 2018). Various traditional forest uses (different forms of wood harvesting, pasture, litter removal, burning of stands) that humans have practiced since ancient times and the activities of ‘ecosystem engineers’ such as moose and beavers have greatly increased the heterogeneity of floodplain forests' microhabitats at site level and thus resulted in exceptional species diversity (Naiman and Rogers, 1997; Machar, 2009; Biró et al., 2019).
Floodplain forest structure and the recent decline of Carya illinoinensis (Wangenh.) K. Koch (northern pecan) at its northern latitudinal range margin, Upper Mississippi River System, USA
2021, Forest Ecology and ManagementCitation Excerpt :Mast from northern pecan provides critical forage for multiple species of endemic fauna (e.g. wild turkey (Meleagris gallopavo), squirrel (Sciurus niger), and white-tailed deer (Odocoileus virginianus); Jones (2008)). Due to the high wildlife, economic, and cultural value of hard mast trees, their overall decline in floodplain forest communities is a major management concern of the UMRS (Guyon and Battaglia, 2018; Yin et al., 1997). During the 20th century, the development of the floodplain forest ecosystems in the UMRS was influenced heavily by a complex history of land use change, river modification, and flood disturbance regimes (De Jager et al., 2016).
Conceptualizing alternate regimes in a large floodplain-river ecosystem: Water clarity, invasive fish, and floodplain vegetation
2020, Journal of Environmental ManagementSpatially explicit modelling of floodplain forest succession: interactions among flood inundation, forest successional processes, and other disturbances in the Upper Mississippi River floodplain, USA
2019, Ecological ModellingCitation Excerpt :This suggests that changes in the hydrologic regime of this particular river system since the establishment of the existing forests may limit forest regeneration in some places. Previous studies have suggested that the construction of the lock and dam system may influence forest regeneration on the UMRS (Yin et al. 2009; Theiling and Burant 2012; Guyon and Battaglia 2018). However, it is also possible that increased discharge in the UMR basin resulting from land-use practices in the larger watershed (e.g., tile drainage), changes in the amount of precipitation, and/or further modification of river flows for navigation have all lead to increased water levels and more frequent flooding over the past 30-40 years.