Geology topics

Lyle J. Guyon

Publications and source records attributed to Lyle J. Guyon.

5 recordsLinked to original sources

USGS2026

Patterns of floodplain forest mortality and recruitment along the Upper Mississippi and Illinois Rivers: Associations with forest fragmentation and flood inundation

Context Different rates of floodplain forest recruitment and mortality can reveal important changes in ecosystem processes that drive forest dynamics, resulting in net changes in forest cover, thereby influencing a wide range of river habitat and morphological characteristics. Objectives We evaluated characteristics of forest change areas in the Upper Mississippi River System. Methods An overlay technique was used to map patches of forest loss, gain, and persistence between 2010 and 2020 in relation to a series of explanatory variables. Results We quantified a net decline in forest cover ranging from 3.2 to 16.8% in the uppermost five study reaches, and a net increase in forest cover ranging from 0.5 to 4.6% in the southernmost three reaches. Patches of forest loss and persistence were similarly tall (> 15 m), dense (> 90% cover), silver maple ( Acer saccharinum ) dominated forests, whereas forest gain patches were short (< 15 m), less dense (< 66% cover) and more likely to be dominated by willow ( Salix) species. Both forest loss and gain patches were smaller than forest persistence patches and were typically found in areas with low neighborhood forest density (< 50% forested 10 ha neighborhood). Areas that experienced more than three flood events per growing season, more than 100 consecutive days of inundation during a single flood event, and more than 60 mean total days of inundation per growing season from 2011 to 2020 showed a net loss of forest cover in all study reaches. In contrast, net increases in forest cover were restricted to areas that experienced less than a single flood event per growing season, less than 40 consecutive days of inundation during a single flood event and less than 30 mean total days of inundation per growing season from 2011 to 2020. Conclusions Forest mortality along these river reaches is associated with forest fragmentation and an increasingly wetter hydrological regime.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗

USGS2026

Proceedings of the Floodplain Vegetation Monitoring Workshop for the Long Term Resource Monitoring Element of the Upper Mississippi River Restoration Program, January 7–8, 2025, Moline, Illinois

Preface In anticipation for increased funding made possible by the Water Resources Development Act of 2020, the Upper Mississippi River Restoration (UMRR) Program identified a need to conduct river-wide assessments of floodplain vegetation. In January 2025, we assembled a group of subject matter experts to perform the following tasks: Review Upper Mississippi River Restoration’s current floodplain vegetation research portfolio, Identify important features and goals for long-term floodplain vegetation monitoring, Evaluate the suitability of existing datasets for system-wide vegetation assessments, and Discuss emerging opportunities to learn about floodplain vegetation dynamics from local-scale restoration and management projects. This document is a summarization of what occurred at the meeting and provides suggested next steps toward developing the capacity to conduct routine long-term monitoring and assessment of floodplain vegetation as part of the Upper Mississippi River Restoration Program.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗

USGS2025

Quantifying floodplain forest community change following large-scale flood events in the Upper Mississippi River System

Effects of large-scale flooding on forest composition and structure are a function of flood duration, depth, timing, and frequency. Throughout the Upper Mississippi River System (UMRS), floods in 1993 and 2019 were record-setting events followed by high rates of tree mortality. These events generated interest in species adaptations to flood event characteristics and how forest communities have changed in response to large-scale floods. We investigated associated tree mortality, how the floods differed spatially, and how floodplain forest communities have changed since 1993. Eight UMRS reaches were surveyed in a 1995 study, documenting vegetation species composition, size, and abundance. In 2021, a selection of plots (63%) were revisited and surveyed to quantify 2019 flood effects. For each site, we extracted daily inundation data for flood years and preceding decades from a surface water inundation model. We found post-flood mortality varied spatially and generally reflected inundation duration patterns. Lower latitude reaches experienced longer inundation durations and greater tree mortality in 1993 than in 2019, while higher latitude reaches experienced similar inundation duration and depth and similar mortality between events. Decadal inundation attributes also differed. During 2009–2018, inundation duration was greater and events occurred later than during 1983–1992 in all reaches. Most forest trajectories were Acer saccharinum -dominated and changed relatively little in species composition and structure. The greatest change in composition occurred at plots with high mortality from the 1993 flood, particularly in more flood-prone locations or where there were many small-diameter individuals. In plots dominated by either Quercus spp. or Populus deltoides , species importance shifted toward more shade and flood-tolerant species after 1995 surveys. Self-replacement of these species may be limited by a change in regeneration conditions resulting from an ongoing inundation regime shift in the case of Quercus spp., or succession to more shade-tolerant species in the case of Populus communities. Overall, effects on floodplain forests from the two flood events were heterogeneous. In some cases, forest change was likely just as influenced by shifts in flood regime as it was from singular flood events.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗

USGS2020

Forest canopy gap dynamics: Quantifying forest gaps and understanding gap – level forest regeneration in Upper Mississippi River floodplain forests

In most forest systems, the dynamics of forest canopy gap development play an important role in the transition from relatively short-lived early successional tree species to longer-lived, late successional tree species. In resilient forest systems, tree seedlings establish within newly created canopy gaps and grow to close the gap within one or two decades of disturbance. However, evidence in portions of the Upper Mississippi River System indicates that floodplain forests do not appear to be following these same trajectories, with canopy gaps instead seeming to fail to recruit new tree seedlings and reverting to non-forested cover types. Because of the heavy dominance of short-lived tree species in current UMRS forests, there is concern that continued failure of canopy gaps to recruit back to forest could be an early indicator of long-term, widespread forest loss as gaps become larger and larger and begin to coalesce into large, non-forested areas. Little research to date has documented either the density and distribution of forest canopy gaps across the UMRS or the vegetative conditions within those gaps to provide an initial assessment of forest dynamics in those areas. The current study utilizes both remotely sensed data and field sampling to assess the conditions of forest canopy gaps within 6 navigation pools on the Upper Mississippi River and one pool on the Illinois River. In general, canopy gap distributions and characteristics are similar across the study, with most pools ranging from 3% to 5% of forest canopy in gaps. Gap sizes are also relatively uniform, with most pools averaging 0.09 to 0.14 ha per gap. The highest proportion of forest cover in canopy gaps at the pool level was driven by the total number of gaps and not gap size, indicating that canopy gap formation in this system is commonly due to individual tree or small clump mortality. Undesirable competing vegetation was dominant in most canopy gaps, with reed canarygrass and native forbs being most prevalent in upper pools and vines most problematic in the lower pools. In the upper pools, very little viable forest regeneration is occurring within canopy gaps. The viability of forest regeneration increases in middle and lower pools, though competing vegetation continues to be a problem. Overall, canopy gaps appear 3 most likely to recruit back to forest in lower pools, and chronic forest loss facilitated by regeneration failures seems most likely in upper pools. However, competing vegetation in lower pools may still interact with woody regeneration to limit effective reestablishment of forest canopy.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗

USGS2019

Spatially explicit modelling of floodplain forest succession: Interactions among flood inundation, forest successional processes, and other disturbances in the Upper Mississippi River floodplain, USA

Simulation models are often used to identify hydrologic regimes suitable for different riparian or floodplain tree species. However, most existing models pay little attention to forest successional processes or other disturbances that may interact with the hydrologic regime of river systems to alter forest dynamics in space and time. In this study, we introduce a flood disturbance module to the LANDIS-II forest succession modelling framework to enable investigations into how inundation interacts with other disturbances and successional processes to alter floodplain forest cover and community dynamics. We illustrate the functionality of the model using a case study with multiple scenarios in the Upper Mississippi River floodplain, USA. We found that model predictions of total forest cover and the abundance of specific forest community types were generally related to uncertainty in the susceptibility of different species and age classes to inundation. By simulation year 100, increases or decreases in total forest cover and forest type distributions were roughly proportional to the initial differences in the susceptibility of species and age classes to inundation. The largest decrease in total forest cover was associated with a scenario that included disturbance by the emerald ash borer ( Agrilus planipennis ) and when using susceptibility parameters corresponding to the weakest flood tolerance. In contrast, changes in the composition of aboveground biomass were not sensitive to differences in susceptibility, and generally showed shifts toward later successional species with higher shade tolerance and longer lifespans for all scenarios. Our findings suggest that flood inundation interacts with other disturbances (e.g., insect outbreaks) and forest successional processes to alter forest abundance, distribution, and species composition in this system. Our modelling framework should allow for future studies that examine such interactions in other systems, and in the context of alternative hydrologic scenarios and other disturbance regimes.

Minnesota, Wisconsin↗