Dormant Season Fires Research Articles

Effects of Growing Season Fire on Northern Bobwhite Nest Site Selection and Survival

Restoration and management of longleaf pine (Pinus palustris) communities necessitates frequent prescribed fire. Prior to human colonization of the southeastern United States thousands of years ago, longleaf pine forests burned primarily during the growing-season as a result of lightning-ignited fires. Growing-season prescribed fire may suppress woody vegetation and promote herbaceous groundcover better than dormant-season fire. Despite the potential ecological benefits of growing-season fire, many land managers use only dormant-season prescribed fire to avoid destruction of ground nests, including those from northern bobwhite (Colinus virginianus). Our objective was to determine bobwhite nest survival and nest-site selection in the presence of early, growing-season prescribed fire on a 3-year return interval. We compared vegetation composition and structure at nest sites and paired random sites to identify important predictors of nest-site selection and to evaluate the effects of habitat covariates on nest survival. We captured bobwhite and attached radio transmitters. Radio-marked individuals were tracked to locate nests and determine nest survival. We documented 2 nests that burned during a growing-season prescribed fire. All 14 nests were located within units that were burned at least 2 years prior, putting these nests at a greater risk for being destroyed by prescribed fire that occurred on a 3-year return interval. We suggest that restricting early, growing-season prescribed burning to April through early June should limit an overlap between prescribed burns and the peak of northern bobwhite nesting season, which occurred mid-July at our study site. Additionally, longer fire return intervals may be needed to allow development of woody understory structure selected by bobwhites for nesting, especially on poor soils like those on our study site in the Sandhills physiographic region.

Fire Effects on Wildlife in the Central Hardwoods and Appalachian Regions, USA

Fire is being prescribed and used increasingly to promote ecosystem restoration (e.g., oak woodlands and savannas) and to manage wildlife habitat in the Central Hardwoods and Appalachian regions, USA. However, questions persist as to how fire affects hardwood forest communities and associated wildlife, and how fire should be used to achieve management goals. We provide an up-to-date review of fire effects on various wildlife species and their habitat in the Central Hardwoods and Appalachians. Documented direct effects (i.e., mortality) on wildlife are rare. Indirect effects (i.e., changes in habitat quality) are influenced greatly by light availability, fire frequency, and fire intensity. Unless fire intensity is great enough to kill a portion of the overstory, burning in closed-canopy forests has provided little benefit for most wildlife species in the region because it doesn’t result in enough sunlight penetration to elicit understory response. Canopy reduction through silvicultural treatment has enabled managers to use fire more effectively. Fire intensity must be kept low in hardwoods to limit damage to many species of overstory trees. However, wounding or killing trees with fire benefits many wildlife species by allowing increased sunlight to stimulate understory response, snag and subsequent cavity creation, and additions of large coarse woody debris. In general, a fire-return interval of 2 yr to 7 yr benefits a wide variety of wildlife species by providing a diverse structure in the understory; increasing browse, forage, and soft mast; and creating snags and cavities. Historically, dormant-season fire was most prevalent in these regions, and it still is when most prescribed fire is implemented in hardwood systems as burn-days are relatively few in the growing season of May through August because of shading from leaf cover and high fuel moisture. Late growing-season burning increases the window for burning, and better control on woody composition is possible. Early growing-season fire may pose increased risk for some species, especially herpetofauna recently emerged from winter hibernacula (April) or forest songbirds that nest in the understory (May to June). However, negative population-level effects are unlikely unless the burned area is relatively large and early growing-season fire is used continually. We did not find evidence that fire is leading to population declines for any species, including Endangered Species Act (ESA)-listed species (e.g., Indiana bat [Myotis sodalis Mill. Allen] or northern long-eared bat [M. septentrionalis Trouess.]). Instead, data indicate that fire can enhance habitat for bats by increasing suitability of foraging and day-roost sites. Similarly, concern over burning and displacement of woodland salamanders (Plethodontidae), another taxa of heightened conservation concern, is alleviated when fire is prescribed along ecologically appropriate aspect and slope gradients and not forced into mesic, high site index environments where salamanders are most common. Because topography across the Central Hardwoods and Appalachians is diverse, we contend that applying fire on positions best suited for burning is an effective approach to increase regional landscape heterogeneity and biological diversity. Herein, we offer prescriptive concepts for burning for various wildlife species and guilds in the Central Hardwoods and Appalachians.

Soil Moisture Affects Growing-Season Wildfire Size in the Southern Great Plains

The increasing availability of soil moisture data presents an opportunity for its use in wildfire danger assessments, but research regarding the influence of soil moisture on wildfires is scarce. Our objective was to identify relationships between soil moisture and wildfire size for Oklahoma wildfires during the growing (May-October) and dormant seasons (November-April). We hypothesized that soil moisture influences wildfire size when vegetation is growing but is less important when most vegetation is dead or dormant. Soil moisture, as fraction of available water capacity (FAW), and commonly measured weather variables were determined for 38,419 wildfires from 2000–2012. Wildfires were grouped by size class (<4.05, ≥4.05 and <40.5, ≥40.5 and <121, ≥121 and <405, and ≥405 ha), and the Kruskal–Wallis test with multiple comparisons was used to identify differences in each variable between wildfire size classes and seasons. Large fires occurred at lower FAW than small fires during both seasons (P < 0.001), but growing-season wildfires ≥405 ha occurred over a narrow range of FAW (0.05–0.46) whereas dormant-season fires of this size occurred across the entire range of FAW (0.05–1.05). For growing-season fires ≥ 121 ha, 91% occurred at FAW < 0.5 and 77% occurred at FAW < 0.2. Our finding that large growing-season wildfires occurred exclusively under conditions of low soil moisture highlights the need to develop methods to use soil moisture data in wildfire danger assessments.

Response of Deeproot Sedge (Cyperus entrerianus) to Herbicide and Prescribed Fire in Texas Coastal Prairie

AbstractIntroduced accidentally from South America, deeproot sedge is rapidly expanding in a variety of habitats throughout the southeastern United States. Of particular concern is its rapid expansion, naturalization, and formation of monocultures in Texas coastal prairie, one of the most imperiled temperate ecoregions in North America. The objective of this research was to examine how deeproot sedge responds to prescribed fire, to the herbicide imazapic, and to treatment combinations of both. Combinations of prescribed fire and imazapic treatments and imazapic-only treatments effectively reduced deeproot sedge cover and frequency. However, plots exposed to dormant season fires (with no imazapic) had greater deeproot sedge cover after burn treatments were applied, indicating that coastal prairie management using only dormant season prescribed fire will not work toward reduction or management of this exotic invasive species. Although deeproot sedge cover was often reduced in fire–imazapic treatment combinations, it was still present in treatment plots. Moreover, desirable functional plant groups (i.e., native bunchgrasses) did not respond positively to the fire–imazapic treatments, but in some instances, woody plant coverage increased. Repeated, long-term approaches using integrated and coordinated efforts with multiple treatment options will be necessary to restore community structure to desired compositional levels. Such integrated approaches should be effective in reducing deeproot sedge frequency, cover, and extent to more manageable levels throughout its introduced geographic range.

Fire induced reproductive mechanisms of a Symphoricarpos (Caprifoliaceae) shrub after dormant season burning.

BackgroundSymphoricarpos, a genus of the Caprifoliaceae family, consists of about 15 species of clonal deciduous shrubs in North America and 1 species endemic to China. In North American tallgrass prairie, Symphoricarpos orbiculatus (buckbrush) is the dominant shrub often forming large colonies via sexual and asexual reproductive mechanisms. Symphoricarpos shrubs, in particular S. orbiculatus, use a unique sexual reproductive mechanism known as layering where vertical stems droop and the tips root upon contact with the soil. Because of conflicting societal values of S. orbiculatus for conservation and agriculture and the current attempt to restore historical fire regimes, there is a need for basic research on the biological response of S. orbiculatus to anthropogenic burning regimes.ResultsFrom 2007 through 2013 we applied prescribed fires in the late dormant season on grazed pastures in the Grand River Grasslands of Iowa. From 2011 to 2013, we measured how S. orbiculatus basal resprouting and layering stems were affected by patchy fires on grazed pastures, complete pasture fires on grazed pastures or fire exclusion without grazing for more than three years. We measured ramet height, ramet canopy diameter, stems per ramet, ramets per 100 m2, and probability of new layering stems 120 days after fire. Height in burned plots was lower than unburned plots but S. orbiculatus reached ~ 84% of pre-burn height 120 days after fire. Stems per ramet were 2x greater in the most recently burned plots due to basal re-sprouting. Canopy diameter and density of ramets was not affected by time since fire, but burned pastures had marginally lower densities than plots excluded from fire (P = 0.07). Fire triggered new layering stems and no new layering stems were found in plots excluded from fire.ConclusionsThe mechanisms of both basal sprouting and aerial layering after fire suggest S. orbiculatus is tolerant to dormant season fires. Furthermore, dormant season fires, regardless if they were patchy fires or complete pasture fires, did not result in mortality of S. orbiculatus. Dormant season fires can reduce S. orbiculatus structural dominance and maintain lower ramet densities but also trigger basal resprouting and layering.Electronic supplementary materialThe online version of this article (doi:10.1186/s40529-014-0080-4) contains supplementary material, which is available to authorized users.

Effects of Biennial Fire and Clipping on Woody and Herbaceous Ground Layer Vegetation: Implications for Restoration and Management of Oak Barren Ecosystems

AbstractSavannas and oak barrens are threatened in North America, due, in part, to removal of natural disturbance regimes. However, the periodic prescribed fires used in savanna and oak barren management sometimes accelerate the formation of a shrub layer, which can displace herbaceous species. This may be because periodic low severity fires act much like clipping, topkilling shrubs, yet allowing them to accumulate reserves in intervals without fire for more vigorous sprouting. To test this, we compared biennial dormant season burn prescriptions to a fire surrogate (clipping) using three oak barrens sites in the Bluegrass Region of southern Ohio. Fire and clipping treatments did little to suppress the resprouting ability of shrubs (woody stems &lt;2 cm dbh), which regrew rapidly and in equivalent densities following treatment. However, both treatments reduced shrub cover, resulting in a 35% decrease in shrub cover over the course of the study. In contrast, non‐manipulated plots experienced a 44% increase in shrub cover over the same time period. Despite this reduction in shrub cover, treatments had no effect on herbaceous plant cover, richness, diversity, or evenness. These results suggest that the use of biennial prescribed dormant season fire, as employed in this study, is equivalent to clipping, and although effective at temporarily reducing shrub cover, is not effective in reducing shrub densities or resprouting potential. Thus, burning during marginal conditions should be avoided for achieving a short‐term restoration goal of shrub removal, but can be effective for maintaining the current shrub layer.

A Field Test of Regeneration in an Isolated Population of Violet Collinsia (Collinsia violacea)

Violet collinsia ( Collinsia violacea ) is a winter annual ranging primarily from Missouri to Kansas. An isolated population occurs in central Illinois, 200 km from the nearest Missouri population, in a series of colonies on adjoining river bluffs. Its oak woodland habitat was undergoing vegetation changes consistent with mesophication including establishment of a subcanopy of sugar maple ( Acer saccharum ). We conducted a field study on one Illinois colony to determine violet collinsia response to early dormant-season fire and to test whether this species might be limited by leaf litter accumulation or absence of fire stimulus. We collected baseline data on plant density and frequency using a stratified-random grid of 72 plots (0.5 m2 ) overlaying the colony. We applied two experimental treatments, fire and leaf litter removal, and a no-treatment control, each with 24 replicates. We used a sheet-metal burn box in the replicate burn plots and a garden rake in leaf-litter removal plots. Only the burn plots had significant changes immediately following treatments, increasing tenfold (12 to 123 plants) between the baseline and post-treatment growing season, and increasing in frequency from 17% to 67%. Post-treatment monitoring indicated there were no carry-over treatment effects. Violet collinsia appears to be a fire-annual with the capacity for persistence in soil seed banks. Following the experiment, a prescribed burn implemented throughout the study unit during the early dormant season also yielded a tenfold increase in the colony.

Vegetation and Avian Response to Oak Savanna Restoration in the Mid-South USA

Abstract Oak (Quercus spp.) savannas are among the most imperiled ecosystems in the United States. Consequently, associated vegetation and avian communities are also in decline. Furthermore, restoration of savanna communities may be an important strategy for conserving avian species that require early successional habitat, a type underrepresented on regional landscapes. Therefore, we evaluated savanna restoration on twelve sites in the Mid-South USA. Specifically, we examined grass, forb, legume, and woody understory cover, regeneration and sapling density, and breeding bird use of the sites following mechanical overstory thinning and dormant-season fire using a hierarchical linear model. Total grass cover was negatively related to canopy cover (P < 0.01) and total forb cover was negatively related to total basal area (P = 0.04). Oak regeneration density was positively related to canopy cover (P < 0.01), while oak competitor regeneration density was positively related to percent slope (P = 0.01) and s...

Long-term (13-year) effects of repeated prescribed fires on stand structure and tree regeneration in mixed-oak forests

The survival and growth of oak advance regeneration is often limited by shade-tolerant species that are abundant in the understory of oak stands. Evidence of historic burning has prompted the use of prescribed fire as a tool to improve the competitive status of oak regeneration in mature stands. A primary shortfall of fire effects research in oak forests has been a lack of long-term studies on the effects of multiple fires. Here we describe the effects of repeated fires on stand structure and tree regeneration over a 13-year period in mature mixed-oak forests located in southern Ohio, USA. Three stands were burned 3–5 times from 1996 to 2005 with low-intensity dormant-season fires, and two stands remained unburned. Woody vegetation was sampled periodically on nine 0.125ha plots per stand. Plots were located across the upland landscape and were characterized by an Integrated Moisture Index. Fire altered stand structure by reducing the density of large saplings (3.0–9.9cm DBH) and midstory trees (10–25cm DBH) by 76% and 34%, respectively. Fire had little impact on trees >25cm DBH. Small saplings (1.4m tall to 2.9cm DBH) were dynamic over time on dry plots that were burned. After being repeatedly topkilled from year 1–8, the small sapling layer had redeveloped on dry burned plots by year 13 and species composition had shifted from dominance by shade-tolerant species to a more equal distribution of shade-tolerants, oaks+hickories, and sassafras. The density of oak+hickory and sassafras advance regeneration (stems 30cm tall to 2.9cm DBH) was significantly greater on burned plots than on unburned plots in year 13, though variability among plots was high. Advance regeneration of shade-tolerant species was equally abundant on burned and unburned plots. Density of oak+hickory advance regeneration in year 13 was positively related to its weighted frequency (a surrogate for size and abundance) in year 0 (r2=0.67, p<0.0001) and inversely related to stand density (r2=0.33, p<0.0001) and canopy cover (r2=0.31, p<0.0001), both of which were reduced by fire. Although oak+hickory advance regeneration was more abundant on burned plots, we conclude that other methods (e.g., herbicide, partial cutting) are necessary to further reduce stand density and promote the development of larger oak+hickory regeneration, particularly on mesic sites.

Portable and Airborne Small Footprint LiDAR: Forest Canopy Structure Estimation of Fire Managed Plots

This study used an affordable ground-based portable LiDAR system to provide an understanding of the structural differences between old-growth and secondary-growth Southeastern pine. It provided insight into the strengths and weaknesses in the structural determination of portable systems in contrast to airborne LiDAR systems. Portable LiDAR height profiles and derived metrics and indices (e.g., canopy cover, canopy height) were compared among plots with different fire frequency and fire season treatments within secondary forest and old growth plots. The treatments consisted of transitional season fire with four different return intervals: 1-yr, 2-yr, 3-yr fire return intervals, and fire suppressed plots. The remaining secondary plots were treated using a 2-yr late dormant season fire cycle. The old growth plots were treated using a 2-yr growing season fire cycle. Airborne and portable LiDAR derived canopy cover were consistent throughout the plots, with significantly higher canopy cover values found in 3-yr and fire suppressed plots. Portable LiDAR height profile and metrics presented a higher sensitivity in capturing subcanopy elements than the airborne system, particularly in dense canopy plots. The 3-dimensional structures of the secondary plots with varying fire return intervals were dramatically different to old-growth plots, where a symmetrical distribution with clear recruitment was visible. Portable LiDAR, even though limited to finer spatial scales and specific biases, is a low-cost investment with clear value for the management of forest canopy structure.

Fire History of a Lower Elevation Jeffrey Pine-Mixed Conifer Forest in the Eastern Sierra Nevada, California, USA

For thousands of years, fire has shaped coniferous forests of the western United States. In more recent time, land use practices have altered the role fire plays in the Sierra Nevada. By understanding the past, land managers can design better fuel treatments today. This research explores the fire regimes of Sagehen Experimental Forest in the eastern Sierra Nevada, California, through a fire scar reconstruction of lower elevation Jeffrey pine (Pinus jeffreyi Balf.) and Jeffrey pine-mixed conifer stands. Prehistoric and historic land use practices, fuel accumulation, and climate influenced the fire regime over three periods of time: pre-settlement (1700 to 1859), settlement (1860 to 1925), and suppression (1925 to 2006). Over the period of analysis, 293 fire scars were assigned calendar years. The mean composite fire return interval for all samples in the study area was two years. The mean composite fire return interval was significantly longer for the suppression period than both the pre-settlement and settlement periods. The lack of sufficient fire intervals for analysis using a filter that included fires that scarred at least three or more trees and 25% of the total sample indicates that fires in the study area are small in spatial extent. The proportion of dormant season fires increased from pre-settlement through the suppression period. No fires were recorded as middle and early earlywood during the suppression period. A superposed epoch analysis found significant correlation to warmer (Pacific Decadal Oscillation) and wetter (Palmer Drought Severity Index) conditions three years prior to large fire events during the pre-settlement period. During the post-settlement era, large fire years were correlated to El Niño conditions for two consecutive years prior. Little synchrony of fire events was recorded between fire scarred tree clusters. These findings suggest that small frequent prescribed burns would best mimic the pre-settlement fire regime if fire is reintroduced into the ecosystem.

Are vegetation—environment relationships different between herbaceous and woody groundcover plants in barrens with shallow soils?

The extent to which woody vegetation exhibits more expansive community structures and different relationships with environmental variables than herbaceous plants is poorly understood in savannas and barrens worldwide, especially those with shallow soils. We explored this question in oak barrens, which are savanna habitats characterized by shallow soils, in southern Ohio, USA. Groundcover plant aerial cover and environmental data were collected using 75 randomly located 1-m2 quadrats in 3 barrens. A combination of non-metric multidimensional scaling (NMDS) and β-flexible cluster analysis revealed 3 distinct herbaceous plant assemblages that varied in abundances of C4 and C3 graminoid species and several forbs. Herbaceous vegetation patterns were correlated with soil acidity, soil depth, plant available water, and especially soil organic matter and quadrat slope. By contrast, woody plants were more widely distributed than herbs, and woody vegetation patterns were strongly correlated only with soil organic matter, although they were weakly associated with quadrat slope and an index of tree influence. The expansion of woody plants into barrens is likely not restricted by most edaphic factors; thus, barrens are highly susceptible to woody plant encroachment that has been fostered by anthropogenic alterations to natural fire regimes (suppression, dormant season fires). We hypothesize that fires that are intended to mimic natural lightning fires during the growing season will be most effective in deterring woody plant encroachment.

Gradient analysis of an eastern sand savanna's woody vegetation, and its long-term responses to restored fire processes

Little information is available comparing historic and modern sand savannas, and how remnants respond to restored fire. We compared short- and long-term effects of restored fire on the Tefft Savanna, a 197 ha eastern sand savanna in northwest Indiana that had undergone three decades of fire protection. U.S. Public Land Survey data from Tefft in 1833 indicate black and white oak barrens, and pin oak savanna, with trees averaging 50 stems/ha and 4 m 2/ha basal area. We used ordination and a digital elevation model to assess topographic distribution of tree species in 1986. In 1986, we also compared initial effects of high- and low-intensity dormant season fire on woody vegetation among nine blocks containing black oak, white oak, and pin oak stands. Twenty years later, we compared the same blocks, all of which had been burned three times per decade with low-intensity fires. In 1986, black oak, white oak and pin oak occurred across a gradient of decreasing elevation and slope. At that time, unburned black oak and white oak stands averaged >400 stems/ha and about 10 m 2/ha basal area, and their smaller size classes contained non-oak woody vegetation that apparently had invaded with fire exclusion. After initial burns, black oak and white oak stands receiving high-intensity fire averaged <200 stems/ha and had significantly lower oak canopy cover and basal area than unburned stands. Stands receiving low-intensity fire had intermediate oak canopy cover, with basal area similar to unburned stands. Pin oak stands were more fire-resistant, apparently because spring flooding often reduced fire effects. Density, cover and basal area of non-oak tree species were much lower than oaks, and were not reduced by initial burning. Repeated low-intensity burning over 20 years tended to maintain structure caused by initial fires. However, it reduced lower size class stem densities, promoted post-fire sprouting into the shrub layer, and allowed oak basal area to increase in larger size classes. Time since fire regulated shrub layer structure on a 4-year cycle. Density and cover of trees and shrubs returned to pre-burn conditions by the second and fourth growing seasons after fire, respectively, with non-oak tree species exceeding pre-burn cover and density by the fourth season. These results suggest that high-intensity fire is more important than repeated low-intensity burning in structuring and restoring eastern sand savanna, and that non-oak tree species, once established, may be resistant to low-intensity fire.

Shifts in morphological traits, seed production, and early establishment ofDesmodium nudiflorumfollowing prescribed fire, alone or in combination with forest canopy thinning

Reintroduction of periodic dormant-season fire and overstory thinning are currently being employed for forest ecosystem management in deciduous forests of eastern North America. These manipulations usually alter the flux of light and the availability of soil nutrients to the perennial herbaceous plants that dominate the understory. We utilized Bayesian statistical methods to examine the effects of prescribed burning (B) and the combination of burning and overstory thinning (T+B) on the morphology, seed production, and early establishment of Desmodium nudiflorum (L.) DC. (Fabaceae) in mixed-oak ( Quercus spp.) forests in southern Ohio. During the fourth growing season after the first fire, plants from thinned and burned (T+B) plots were 62% larger than plants from control plots (C). Both burning alone (B) and T+B treatments decreased specific leaf area (SLA). T+B also resulted in significantly decreased root mass ratio (RMR), and increased leaf mass ratio (LMR), and specific root length (SRL). During the first growing season after a second fire, both B and T+B resulted in significantly increased plant biomass, LMR, individual seed mass, and total seed production, as well as decreased SLA and plant height; in contrast, neither B nor T+B had significant impacts on leaf area ratio or seedling establishment. Prescribed fire, especially when combined with thinning, can result in increases in total biomass, seed size, and seed production, and hence enhance the fitness of this perennial herb in these mixed-oak forests.

Demographic responses of Pinguicula ionantha to prescribed fire: a regression-design LTRE approach

This study describes the use of periodic matrix analysis and regression-design life table response experiments (LTRE) to investigate the effects of prescribed fire on demographic responses of Pinguicula ionantha, a federally listed plant endemic to the herb bog/savanna community in north Florida. Multi-state mark-recapture models with dead recoveries were used to estimate survival and transition probabilities for over 2,300 individuals in 12 populations of P. ionantha. These estimates were applied to parameterize matrix models used in further analyses. P. ionantha demographics were found to be strongly dependent on prescribed fire events. Periodic matrix models were used to evaluate season of burn (either growing or dormant season) for fire return intervals ranging from 1 to 20 years. Annual growing and biannual dormant season fires maximized population growth rates for this species. A regression design LTRE was used to evaluate the effect of number of days since last fire on population growth. Maximum population growth rates calculated using standard asymptotic analysis were realized shortly following a burn event (<2 years), and a regression design LTRE showed that short-term fire-mediated changes in vital rates translated into observed increases in population growth. The LTRE identified fecundity and individual growth as contributing most to increases in post-fire population growth. Our analyses found that the current four-year prescribed fire return intervals used at the study sites can be significantly shortened to increase the population growth rates of this rare species. Understanding the role of fire frequency and season in creating and maintaining appropriate habitat for this species may aid in the conservation of this and other rare herb bog/savanna inhabitants.

Prickly Pear Cactus Responses to Summer and Winter Fires

Prescribed fire is used to reduce size and density of prickly pear cactus (Opuntia spp.) in many rangeland ecosystems. However, effects of dormant season fires (i.e., winter fires) are inconsistent. Thus, there is increasing interest in use of growing season (summer) fires. Our objective was to evaluate effects of fire season and fire intensity on mortality and individual plant (i.e., “motte”) structure (area per motte, cladodes per motte, motte height) of brownspine prickly pear (O. phaeacantha Engelm.). The study had 4 treatments: no fire, low-intensity winter fire, high-intensity winter fire, and summer fire. Three sizes of prickly pear mottes were evaluated: small (0–20 cladodes per motte), medium (21–100), and large (101–500). At 3 years postfire, prickly pear mortality in the summer fire treatment was 100% in small mottes, 90% in medium mottes, and 80% in large mottes. Motte mortality increased in this treatment over time, especially in large mottes. Mortality from high-intensity winter fires was 29% and 19% in small and medium mottes, respectively, but no large mottes were killed. Motte mortality was < 10% in low-intensity winter fire and no-fire treatments. Summer fires reduced all motte structural variables to 0 in small mottes and nearly 0 in other motte size classes. High-intensity winter fires reduced some structural variables of medium and large mottes, but had no long-term negative effects on area per motte or cladodes per motte in surviving small mottes. Low-intensity winter fires had no long-term negative effects on motte structure in any size class. Rapid growth of mottes, and especially small mottes, in the no-fire treatment suggested that resistance to winter fires can occur rapidly.

Ecophysiological responses of two herbaceous species to prescribed burning, alone or in combination with overstory thinning

The oak-rich deciduous forests of the central Appalachian Mountains of eastern North America have changed significantly since the onset of effective fire suppression early in the 20th century. Those changes have resulted in progressively decreasing light and nutrient supplies to herbaceous perennial understory species. Application of ecological restoration treatments such as reintroduction of frequent dormant-season fire and overstory thinning to pre-suppression density often increase light, soil temperature and moisture, and short-term nutrient availability to pre-suppression levels. To persist in this environment, perennial understory herbs must be able to acclimate phenotypically to the very different resource supply combinations present with and without fire suppression. As part of a larger study of the response of the long-lived herbaceous perennials Desmodium nudiflorum and Panicum boscii to ecosystem restoration treatments in Ohio mixed-oak forests, this study examined the ecophysiological effects of prescribed burning (B) and the combination of burning and thinning (T + B) in mixed-oak forests in southern Ohio. Control (C) plants had significantly lower maximum photosynthetic rate (A(max)) than those in the treated plots. The enhancement of A(max) averaged 26.7% and 52.7% in the B and T + B treatments, respectively. Plants from the T + B plots had higher quantum yield, stomatal conductance, and photosynthetic nutrient use efficiency than B and C plants. B plants had greater intrinsic water use efficiency (WUE) than plants in the C or T + B treatments. Light saturation point (LSP), light compensation point (LCP), and "dark" respiration (DR) did not differ among treatments. Photosynthetic parameters did vary significantly between the species, but no significant treatment × species interactions were detected. Our results support the hypothesis that prescribed burning, especially when combined with overstory thinning, in these perennial herbs can result in phenotypic acclimation characterized by enhanced photosynthetic performance.

Effects of dormant- vs. growing-season fire in shortgrass steppe: Biological soil crust and perennial grass responses

This research experimentally examined seasonal effects of fire on biological soil crusts and perennial grasses in shortgrass steppe. We predicted dormant-season fire would have greater negative effects on biological soil crusts than fire during the growing season, but less of an impact on perennial grasses than fire during the growing season. Treatments were dormant- and growing-season fires and unburned reference condition plots. Response variables included biological soil crust and grass percent ground cover, and crust nitrogen fixation and chlorophyll a content. Results indicated shortgrass steppe can recover from fire in three to 30 months, dependent on fire season. Burning during the dormant-season had little effect on grass cover, but decreased nitrogen fixation and reduced chlorophyll a content in crusts. Growing-season fire negatively impacted grass cover, but reduced the impact of fire on soil crusts. Most of the fire effects in this study were of relatively short duration and strongly tied to weather patterns.

Responses of root‐crown bearing shrubs to differences in fire regimes in Pinus palustris (longleaf pine) savannas: Exploring old‐growth questions in second‐growth systems

AbstractQuestion: What are the effects of fire season and intensity on resprouting of different root‐crown bearing shrub species in second‐growth Pinus palustris (longleaf pine) savannas?Location: northern Florida and eastern Louisiana, USA.Methods: In Florida, quadrats were burned biennially either during the dormant season or the growing season. In Louisiana, we applied intensity treatments to quadrats by manipulating ground‐cover fuels, just prior to biennial growing season fires. Maximum fire temperatures were measured, and stem densities were censused before and after fires in both regions.Results: After dormant season fires in Florida, stem densities were seven times greater than initial levels for Hypericum spp. In contrast, growing season fires reduced densities of H. brachyphyllum by 65%, but did not change densities of H. microsepalum. Only resprouting of H. microsepalum decreased with increased fire intensity. In Louisiana, fire intensity influenced Ilex vomitoria, but not Quercus spp. Following fires, stem densities oil. vomitoria were five times greater in fuel removal than fuel addition areas.Conclusions: Past use of dormant season fires likely contributed to increased abundances of some species of root‐crown bearing shrubs observed today in old‐growth savannas. Reintroduction of growing season fires will be effective in maintaining or decreasing stem densities, depending on species and fuel type. Genet mortality and stem density reductions appear most likely in areas at localized scales where tree falls and needle coverage create hotspots in Pinus palustris savannas.

Responses of root-crown bearing shrubs to differences in fire regimes in Pinus palustris (longleaf pine) savannas: Exploring old-growth questions in second-growth systems

Question What are the effects of fire season and intensity on resprouting of different root-crown bearing shrub species in second-growth Pinus palustris (longleaf pine) savannas?Location: northern Florida and eastern Louisiana, USA.Methods: In Florida, quadrats were burned biennially either during the dormant season or the growing season. In Louisiana, we applied intensity treatments to quadrats by manipulating ground-cover fuels, just prior to biennial growing season fires. Maximum fire temperatures were measured, and stem densities were censused before and after fires in both regions.Results: After dormant season fires in Florida, stem densities were seven times greater than initial levels for Hypericum spp. In contrast, growing season fires reduced densities of H. brachyphyllum by 65%, but did not change densities of H. microsepalum. Only resprouting of H. microsepalum decreased with increased fire intensity. In Louisiana, fire intensity influenced Ilex vomitoria, but not Quercus spp. Following fires, stem densities of I. vomitoria were five times greater in fuel removal than fuel addition areas.Conclusions: Past use of dormant season fires likely contributed to increased abundances of some species of root-crown bearing shrubs observed today in old-growth savannas. Reintroduction of growing season fires will be effective in maintaining or decreasing stem densities, depending on species and fuel type. Genet mortality and stem density reductions appear most likely in areas at localized scales where tree falls and needle coverage create hotspots in Pinus palustris savannas.Nomenclature: Godfrey (1988).