Impacts of Riparian and Non-riparian Woody Encroachment on Tallgrass Prairie Ecohydrology

"Impacts of Riparian and Non-riparian Woody Encroachment on Tallgrass Prairie Ecohydrology"

This open access article was published April 13, 2022, in Ecosystems. Access the article via the permanent web address (DOI). (https://doi.org/10.1007/s10021-022-00756-7)

Abstract

Woody encroachment has impacted grassland ecohydrology worldwide, prompting management strategies aimed at woody vegetation removal to prevent or mitigate loss of water yield. We measured stream discharge following sustained cutting of riparian trees (2010–2020) in a native tallgrass prairie (northeastern Kansas, USA). Discharge has declined at this site since the 1980’s despite a concurrent increase in precipitation. This decline has been previously attributed to increased transpiration of stream water by riparian vegetation. We used water stable isotopes (δ¹⁸O and δ²H) to determine whether riparian grasses, shrubs, and trees primarily used stream/groundwater or soil water. Additionally, we quantified the increase in riparian and non-riparian woody cover (1978–2020) and combined it with sap-flux data to estimate changes in transpirative water loss. Sustained cutting of riparian trees did not result in increased discharge. Rather than stream/groundwater, the largest proportion of water used by riparian trees (Quercus spp.) was deep soil water. Cornus drummondii (clonal woody shrub) used a higher proportion of stream water and had greater overall variability in water-use. Riparian shrub cover increased about 57% from 1978 to 2020. Over the same time period, shrub cover increased about 20% in areas outside the riparian zone, resulting in an estimated 25% increase in daily transpirative water loss. Although stream water use was less than 50% for all riparian zone species, the total increase in shrub cover on this watershed, coupled with higher transpiration rates of shrubs, suggests that these woody species—within and outside the riparian zone—are key contributors to observed declines in stream flow in this system.

Citation

Keen, R.M., Nippert, J.B., Sullivan, P.L. et al. "Impacts of Riparian and Non-riparian Woody Encroachment on Tallgrass Prairie Ecohydrology." Ecosystems 26, 290–301 (2023). 

Estimated Mortality and Morbidity Attributable to Smoke Plumes in the United States: Not Just a Western US Problem

"Estimated Mortality and Morbidity Attributable to Smoke Plumes in the United States: Not Just a Western US Problem"

This open access article was published August 21, 2021, in GeoHealth. Access the article via the permanent web address (DOI).  (https://doi.org/10.1029/2021GH000457)

Abstract

As anthropogenic emissions continue to decline and emissions from landscape (wild, prescribed, and agricultural) fires increase across the coming century, the relative importance of landscape-fire smoke on air quality and health in the United States (US) will increase. Landscape fires are a large source of fine particulate matter (PM2.5), which has known negative impacts on human health. The seasonal and spatial distribution, particle composition, and co-emitted species in landscape-fire emissions are different from anthropogenic sources of PM2.5. The implications of landscape-fire emissions on the sub-national temporal and spatial distribution of health events and the relative health importance of specific pollutants within smoke are not well understood. We use a health impact assessment with observation-based smoke PM2.5 to determine the sub-national distribution of mortality and the sub-national and sub-annual distribution of asthma morbidity attributable to US smoke PM2.5 from 2006 to 2018. We estimate disability-adjusted life years (DALYs) for PM2.5 and 18 gas-phase hazardous air pollutants (HAPs) in smoke. Although the majority of large landscape fires occur in the western US, we find the majority of mortality (74%) and asthma morbidity (on average 75% across 2006–2018) attributable to smoke PM2.5 occurs outside the West, due to higher population density in the East. Across the US, smoke-attributable asthma morbidity predominantly occurs in spring and summer. The number of DALYs associated with smoke PM2.5 is approximately three orders of magnitude higher than DALYs associated with gas-phase smoke HAPs. Our results indicate awareness and mitigation of landscape-fire smoke exposure is important across the US.

Plain Language Summary

The pollutants from landscape (wild, prescribed, and agricultural) fires are expected to have an increasing impact on air quality and health in the United States (US) across the current century. The implications of landscape-fire smoke on the regional and seasonal distribution of health events and the relative health importance of specific pollutants within smoke are not well understood. In the present study, we assess the seasonal and regional distribution of the health impacts from US smoke exposure from 2006 to 2018. We also estimate the long-term health impacts for both fine particles (PM2.5) and gas-phase hazardous air pollutants (HAPs) in smoke. Although the majority of large landscape fires occur in the western US, we find the majority of deaths (74%) and asthma emergency department visits and hospital admissions (on average 75% across 2006–2018) attributable to smoke occur outside the West. Across the US, smoke-attributable asthma emergency department visits predominantly occur in spring and summer. The long-term health impacts associated with smoke PM2.5 are much higher than the estimated long-term health impacts of gas-phase smoke HAPs. Our results indicate awareness and mitigation of landscape-fire smoke exposure is important across the US, not just in regions in proximity to large wildfires.

Keywords: air quality; wildfire smoke; PM2.5; hazardous air pollutants; health impact assessment

Citation

O’Dell, K., Bilsback, K., Ford, B., Martenies, S. E., Magzamen, S., Fischer, E. V., & Pierce, J. R. (2021). "Estimated mortality and morbidity attributable to smoke plumes in the United States: Not just a western US problem." GeoHealth,  5, e2021GH000457.

Wildfire, Smoke Exposure, Human Health, and Environmental Justice Need to be Integrated into Forest Restoration and Management

"Wildfire, Smoke Exposure, Human Health, and Environmental Justice Need to be Integrated into Forest Restoration and Management"

This open access article was published May 7th, 2022, in Current Environmental Health Reports. Access the article via the permanent web address (DOI). (https://doi.org/10.1007/s40572-022-00355-7)

Abstract

Purpose of Review

Increasing wildfire size and severity across the western United States has created an environmental and social crisis that must be approached from a transdisciplinary perspective. Climate change and more than a century of fire exclusion and wildfire suppression have led to contemporary wildfires with more severe environmental impacts and human smoke exposure. Wildfires increase smoke exposure for broad swaths of the US population, though outdoor workers and socially disadvantaged groups with limited adaptive capacity can be disproportionally exposed. Exposure to wildfire smoke is associated with a range of health impacts in children and adults, including exacerbation of existing respiratory diseases such as asthma and chronic obstructive pulmonary disease, worse birth outcomes, and cardiovascular events. Seasonally dry forests in Washington, Oregon, and California can benefit from ecological restoration as a way to adapt forests to climate change and reduce smoke impacts on affected communities.

Recent Findings

Each wildfire season, large smoke events, and their adverse impacts on human health receive considerable attention from both the public and policymakers. The severity of recent wildfire seasons has state and federal governments outlining budgets and prioritizing policies to combat the worsening crisis. This surging attention provides an opportunity to outline the actions needed now to advance research and practice on conservation, economic, environmental justice, and public health interests, as well as the trade-offs that must be considered.

Summary

Scientists, planners, foresters and fire managers, fire safety, air quality, and public health practitioners must collaboratively work together. This article is the result of a series of transdisciplinary conversations to find common ground and subsequently provide a holistic view of how forest and fire management intersect with human health through the impacts of smoke and articulate the need for an integrated approach to both planning and practice.

Citation

D’Evelyn, S.M., Jung, J., Alvarado, E. et al. Wildfire, Smoke Exposure, Human Health, and Environmental Justice Need to be Integrated into Forest Restoration and Management.Curr Envir Health Rpt 9, 366–385 (2022).

Functional consequences of animal community changes in managed grasslands: An application of the CAFE approach

"Functional consequences of animal community changes in managed grasslands: An application of the CAFE approach"

This open access article was published October 25, 2023, in Ecology. Access the article via the permanent web address (DOI). (https://doi.org/10.1002/ecy.4192)

Abstract

In the midst of an ongoing biodiversity crisis, much research has focused on species losses and their impacts on ecosystem functioning. The functional consequences (ecosystem response) of shifts in communities are shaped not only by changes in species richness, but also by compositional shifts that result from species losses and gains. Species differ in their contribution to ecosystem functioning, so species identity underlies the consequences of species losses and gains on ecosystem functions. Such research is critical to better predict the impact of disturbances on communities and ecosystems. We used the “Community Assembly and the Functioning of Ecosystems” (CAFE) approach, a modification of the Price equation to understand the functional consequences and relative effects of richness and composition changes in small nonvolant mammal and dung beetle communities as a result of two common disturbances in North American prairie restorations, prescribed fire and the reintroduction of large grazing mammals. Previous research in this system has shown dung beetles are critically important decomposers, while small mammals modulate much energy in prairie food webs. We found that dung beetle communities were more responsive to bison reintroduction and prescribed fires than small nonvolant mammals. Dung beetle richness increased after bison reintroduction, with higher dung beetle community biomass resulting from changes in remaining species (context-dependent component) rather than species turnover (richness components); prescribed fire caused a minor increase in dung beetle biomass for the same reason. For small mammals, bison reintroduction reduced energy transfer through the loss of species, while prescribed fire had little impact on either small mammal richness or energy transfer. The CAFE approach demonstrates how bison reintroduction controls small nonvolant mammal communities by increasing prairie food web complexity, and increases dung beetle populations with possible benefits for soil health through dung mineralization and soil bioturbation. Prescribed fires, however, have little effect on small mammals and dung beetles, suggesting a resilience to fire. These findings illustrate the key role of re-establishing historical disturbance regimes when restoring endangered prairie ecosystems and their ecological function.

Keywords: bison; community assembly; dung beetle; ecosystem function; prescribed fire; Price equation; small mammal; species richness; tallgrass prairie restoration

Citation

Hogan, Katharine FE, Holly P. Jones, Kirstie Savage, Angela M. Burke, Peter W. Guiden, Sheryl C. Hosler, Erin Rowland‐Schaefer, and Nicholas A. Barber. "Functional consequences of animal community changes in managed grasslands: An application of the CAFE approach." Ecology (2023): e4192.

Dispersal and persistence traits inform long-term herbaceous plant community change in encroached savannas

"Dispersal and persistence traits inform long-term herbaceous plant community change in encroached savannas"

This open access article was published March 2, 2023, in Plant Ecology. Access the article via the permanent web address (DOI). (https://doi.org/10.1007/s11258-023-01307-3)

Abstract

Savanna plant communities are highly diverse, characterized by an open-canopy structure with rich herbaceous diversity, and maintained by frequent low-intensity fire and grazing. Due to habitat loss and fragmentation, savannas are globally threatened, with less than 1% of former oak savanna land cover found in the Midwestern United States remaining. In remnant oak savannas, loss of fire and grazing has led to woody encroachment and canopy closure over the past century with cascading consequences for the taxonomic composition. Whether these taxonomic changes can be broadly predicted using species functional traits (morpho-physio-phenological characteristics that impact the fitness of a species) is a key question. We ask whether the impacts of woody encroachment on herbaceous species can be predicted from species’ abilities to persist (avoid extinction) and disperse (colonize new areas). Specifically, we pair persistence traits (e.g., clonality, belowground storage) and dispersal traits (e.g., seed mass, dispersal mode, flowering height) with a rare 60-year dataset from oak savannas in Wisconsin, USA to understand how the representation of these traits has changed in the herbaceous community over time. Over 60 years, change in species composition was explained both by dispersal abilities and persistence traits; small-seeded species reliant on unassisted dispersal and moderately clonal species experienced the greatest losses. These changes in functional composition are likely due to increased woody encroachment, which may impede propagule production and movement. Restoration efforts need to prioritize species that are dispersal limited and those that create fine fuels, which aid the persistence of fire-maintained open habitat savannas.

Keywords: Dispersal; persistence; woody encroachment; colonization, local extinction, temperate oak savanna

Citation

Ahler, S.J., Ladwig, L.M., Charton, K.T. et al. Dispersal and persistence traits inform long-term herbaceous plant community change in encroached savannas. Plant Ecol 224, 361–371 (2023).

Prescribed Fire Causes Wounding and Minor Tree Quality Degradation in Oak Forests

"Prescribed Fire Causes Wounding and Minor Tree Quality Degradation in Oak Forests"

This open access article was published January 25, 2023, in Forests. Access the article via the permanent web address (DOI).  (https://doi.org/10.3390/f14020227)

Abstract

Despite the adaptation of many oak (Quercus) species to repeated surface fire, many public land managers in eastern North America resist using prescribed fire as a regeneration tool because of fire’s perceived negative impacts on timber values through the wounding of overstory trees. We retrospectively quantified fire-associated wounds in 139 oak-dominated stands across four national forests, each with a history of zero to six prescribed fires within the last 30 years. For trees > 25.4 cm dbh (n = 8093), fire-associated wounds within the first 3.67 m of height were categorized by type, measured for defect size and graded both accounting for and then ignoring the fire-associated wounds. Most fire-associated wounds (n = 3403) were catfaces (32.5%), seams (30.5%) or bark slough (30.1%), although catfaces had 2.1–6.4 times the average volume loss of any other wound type (9.90 ± 0.72 bd ft). Among the 2160 wounded trees sampled, 741 had multiple (≥2) wounds. Although 29.1% of all trees had at least one wound associated with prescribed fire, only 7.0% of those trees exhibited a reduction in tree grade. The likelihood of wounding was greater in stands receiving more prescribed burns, but unaffected by tree diameter for either thin- or thick-barked species. Considering both the likelihoods of wounding and grade reduction, white oak (Q. alba), chestnut oak (Q. montana), hickory (Carya sp.), shortleaf pine (Pinus echinata) and yellow-poplar (Liriodendron tulipifera) trees were more resistant to prescribed fire damage than other species. While our findings cannot be related directly to individual fire parameters, such as fireline intensity or fire duration, these results do provide estimates of the cumulative effects of multiple management-based prescribed fires that can be incorporated into fire effects models.

Keywords: fire ecology; Quercus; timber damage; fire effects;oak regeneration; tree grades

Citation

Saunders, Mike R., David P. Mann, Shannon Stanis, Jan K. Wiedenbeck, Daniel C. Dey, and Thomas M. Schuler. 2023. "Prescribed Fire Causes Wounding and Minor Tree Quality Degradation in Oak Forests" Forests 14, no. 2: 227. 

Oak savanna vegetation response to layered restoration approaches: Thinning, burning, and grazing

"Oak Savanna vegetation response to layered restoration approaches: Thinning, burning, and grazing"

This open access article was published March 28, 2023, in Forest Ecology and Management. Access the article via the permanent web address (DOI).  (https://doi.org/10.1016/j.foreco.2023.120931)

Abstract

Temperate savannas are unique, biodiverse ecosystems that have undergone extensive habitat conversion globally. In the midwestern United States, 99% of historic oak savanna area has been lost. Most remaining patches of savanna are degraded due to woody encroachment following the removal of both fire and large herbivore disturbances from the landscape. Restoring degraded savanna remnants is challenging because we lack an understanding of how to best apply contemporary restoration tools to mimic historic disturbance dynamics. To that end, we evaluated the outcomes of ongoing oak savanna restorations that have received a gradient of restoration actions: 1) no management, 2) tree thinning, 3) thinning + burning, and 4) thinning + burning + cattle grazing. We assessed several metrics of restoration success including canopy, shrub, herbaceous, and non-native cover, herbaceous diversity, and plant community composition. We found that layering restoration approaches achieved certain, but not all, structural vegetation goals. Compared to no management, thinning and fire successfully increased canopy openness, herbaceous cover, and herbaceous diversity, but had the unwanted effect of increased shrub cover. The addition of low-intensity cattle grazing did not improve structural outcomes. We also found that each restoration treatment left a unique signature on understory plant community composition. Unmanaged and thin-only treatments were characterized by tree saplings and woodland herbs, while burned and grazed treatments were defined by shrubs and savanna-associate species. We conclude that reintroducing multiple disturbances does not guarantee the successful restoration of disturbance-dependent ecosystems such as oak savannas. Restoration outcomes are not dictated by how many management approaches are applied, but rather, the nuances of how they are applied such as burn season and livestock density.

Keywords: Oak savanna; Restoration; Vegetation; Tree thinning; Prescribed fire; Cattle grazing

Citation

Austin M. Yantes, Samuel P. Reed, Anna M. Yang, Rebecca A. Montgomery, "Oak savanna vegetation response to layered restoration approaches: Thinning, burning, and grazing," Forest Ecology and Management, Volume 537, 2023,120931, ISSN 0378-1127

The Prairie Peninsula and Climate Change

"The Prairie Peninsula and Climate Change"

This open access article was published April 19, 2023, in the Natural Areas Journal. Access the article via the permanent web address (DOI). (https://doi.org/10.3375/0885-8608-43.2.135)

Abstract

Transition and recovery from prolonged effects of climate change on an ecosystem will be affected by geography, topography, and plant physiology. Fire, grazing, flooding, succession, biodiversity, invasive species, and stewardship all affect the “resilience” (the capacity to recover) of an ecosystem to the effects of long-term changes in weather patterns. These significant “controls” should be part of climate change discussions. Research from various disciplines suggests that the actions of humans on the landscape minimized and/or ameliorated some of the impacts of past changes in climate. Today, stewardship and restoration efforts may mitigate some of the effects of climate change, especially in fire-dependent natural communities.

Citation

Harty, Francis M. "The Prairie Peninsula and Climate Change." Natural Areas Journal 43, no. 2 (2023): 135-139.

Intervention intensity predicts the quality and duration of prairie restoration outcomes

"Intervention intensity predicts the quality and duration of prairie restoration outcomes"

This open access article was published August 29, 2023, in Restoration Ecology. Access the article via the permanent web address (DOI). (https://doi.org/10.1111/rec.13993)

Abstract

Restoration of grassland ecosystems is essential for mitigating global losses of biodiversity and is typically initiated to foster persistent, long-term increases in biodiversity. Yet, evaluating long-term impacts of restoration on biodiversity is rare, especially across sites restored using consistent methods. Evaluation of restoration outcomes is particularly important for increasing predictive capacity in restoration ecology to determine the level of restoration effort that is required to achieve both short- and long-term restoration goals. We conducted a multisite study that explicitly compared the impacts of no intervention (“passive” or “natural” recovery), low intervention (seeding native plants), and moderate intervention (seeding native plants and using fire management) at 32 restored prairies differing in the age of restoration (3–23 years). Grasslands with natural recovery have equivalent native plant species richness compared to sites with low and moderate restoration intervention, however, they have significantly lower-quality vegetation, as measured by Floristic Quality (mean C). We found that managing restored prairies with fire maintains native plant richness over time and is correlated with higher vegetation quality and presence of seeded species. Seed mixes with a high mean C score are positively correlated with plant community quality. However, seed mixes with more species are negatively correlated with the proportion of seeded species present. We found that while the degree of restoration intervention has no effect on the number of native plant species, greater levels of assisted recovery are required to produce restored prairies that resemble high-quality remnant vegetation and, especially, to maintain these successes over the long term.

 Implications for Practice

The intensity of restoration interventions in prairies does not change the total number of native plant species but alters the Floristic Quality and successional stage of vegetation. Some early successional native species of low conservation value can become dominant at sites being managed with natural recovery alone.

Adding seeds to existing restored prairies may help maintain native plant species richness, Floristic Quality, and the proportion of seeded species that establish over time, ensuring the longevity of restoration investments.

Long-term care and management (particularly fire management) is required to maintain high native plant species richness, a high-quality plant community, and seeded-species establishment success.

Increased soil nutrients resulting from historical agricultural land-use are not always a predictive factor of restoration outcomes and do not always prevent successful outcomes.

Keywords: active restoration; assisted recovery; intervention intensity; land-use legacies; natural recovery; passive restoration; seed addition; tallgrass prairie; fire

Citation

McFarlane, Stephanie L., Jade M. Kochanski, Claudio Gratton, and Ellen I. Damschen. "Intervention intensity predicts the quality and duration of prairie restoration outcomes." Restoration Ecology (2023): e13993.

Habitat fragmentation decouples fire-stimulated flowering from plant reproductive fitness

"Habitat fragmentation decouples fire-stimulated flowering from plant reproductive fitness"

This open access article was published September 18, 2023, in the Proceedings of the National Academy of Sciences. Access the article via the permanent web address (DOI). (https://doi.org/10.1073/pnas.2306967120) 

Abstract

Many plant species in historically fire-dependent ecosystems exhibit fire-stimulated flowering. While greater reproductive effort after fire is expected to result in increased reproductive outcomes, seed production often depends on pollination, the spatial distribution of prospective mates, and the timing of their reproductive activity. Fire-stimulated flowering may thus have limited fitness benefits in small, isolated populations where mating opportunities are restricted and pollination rates are low. We conducted a 6-y study of 6,357 Echinacea angustifolia (Asteraceae) individuals across 35 remnant prairies in Minnesota (USA) to experimentally evaluate how fire effects on multiple components of reproduction vary with population size in a common species. Fire increased annual reproductive effort across populations, doubling the proportion of plants in flower and increasing the number of flower heads 65% per plant. In contrast, fire’s influence on reproductive outcomes differed between large and small populations, reflecting the density-dependent effects of fire on spatiotemporal mating potential and pollination. In populations with fewer than 20 individuals, fire did not consistently increase pollination or annual seed production. Above this threshold, fire increased mating potential, leading to a 24% increase in seed set and a 71% increase in annual seed production. Our findings suggest that density-dependent effects of fire on pollination largely determine plant reproductive outcomes and could influence population dynamics across fire-dependent systems. Failure to account for the density-dependent effects of fire on seed production may lead us to overestimate the beneficial effects of fire on plant demography and the capacity of fire to maintain plant diversity, especially in fragmented habitats.

Keywords: Prairie; fire; allee effect; phenology; density difference

Citation

Beck, Jared, Amy Waananen, and Stuart Wagenius. "Habitat fragmentation decouples fire-stimulated flowering from plant reproductive fitness." Proceedings of the National Academy of Sciences 120, no. 39 (2023): e2306967120.