Effects Of Fire Season Research Articles

The impacts of inter- and intra-seasonal burns on the terrestrial orchid Pterostylis curta

Prescribed burning is a management tool used for both management of fuel loads and for ecological purposes across fire prone areas. While in temperate areas wildfires usually occur during the hottest summer months, prescribed burns are generally conducted in autumn and spring, when conditions are more suitable for controlling fire. Orchids maintain avoidance mechanisms, such as persisting as dormant tubers during the predominant fire season, and therefore may be at risk from prescribed burns occurring during their active life cycle period. Using a glasshouse experiment, we investigated the impacts of fire season on the Australian orchid species Pterostylis curta. This approach allowed us to i) implement seasonal burns and relate impacts to quantifiable above and belowground life cycle stages of the study species, ii) isolate and assess the role of smoke, and iii) control for fire intensity and life stage of the study species at each of the treatment levels to enable robust comparison focused on fire season effects. We found that late autumn burns caused complete failure of a cohort in our glasshouse study. Heat alone was not the driver of tuber mortality, because soil heating was similar across all burn seasons, and plants burnt in the three other seasons were able to re-emerge strongly in the growing season after fire. Furthermore, a lack of post-fire emergence was due to tuber mortality, not dormancy. Our results highlight that there is likely an interaction between fire-related heat and the life cycle stage at which burning occurs, especially replacement tuber initiation, that drives post-fire demography. We show that orchids like P. curta had the lowest risk of negative impacts when burnt in the later stages of their growing season, and that an understanding of finer-scale phenological cycles can inform more robust fire management of orchid species.

Fire season matters for midstory hardwood control: Impacts of fire season and firing technique on plant communities

In the southeastern USA, lack of historical fire regimes often leads to hardwood encroachment into early successional plant communities and managed pine stands, reducing wildlife value and timber yields. Land managers lack information on how firing technique interacts with fire season to influence plant communities. We designed an experiment to quantify these interactions in east-central Mississippi with pairs of 4 m × 8 m plots randomly assigned a backing and heading fire in each of three seasons: February (Feb), May–June (May/Jun), and September–October (Sep/Oct). We used thermocouples to monitor fire temperature and tagged midstory trees to monitor response. We lit heading fires with an 18–25 kph wind generated by a backpack blower and backing fires into the ambient wind. Despite backing fires producing longer residence times than heading fires and raising temperature above the lethal threshold of 60 °C an average of 54 s longer, firing technique did not influence midstory response one growing season post-fire. Backing and heading fires produced similar maximum temperatures. For both firing techniques, May/Jun resulted in the highest midstory mortality rates which were 3-fold greater than Sep/Oct and 4-fold greater than Feb. Among all three fire seasons, trees with a 2.5 cm diameter at breast height (DBH) had approximately a 75% chance of top-kill which decreased to <20% as trees approached 6.5 cm DBH. We found no effects of fire season on fire temperature, rate of spread, flame height, or percent crown scorch. We found no significant interactions between fire season and firing technique. Understory analysis revealed Sep/Oct produced the greatest increase in forb coverage, May/Jun resulted in the most grass coverage, and Feb produced the most brambles (Rubus spp.). On sites with similar species, weather, and fuel conditions to ours, land managers should emphasize fire season over firing technique for midstory control and understory manipulation. Where midstory hardwood control with fire is a priority, fire return intervals should be frequent enough to prevent trees from exceeding 2.5 cm DBH to avoid trees escaping fire's reach. These data can help managers reduce midstory competition with crop trees and promote understory development for wildlife.

Fire stimulates grass flowering in the Cerrado independent of season

AbstractQuestionsPost‐fire flowering is an underestimated plant trait of many fire‐prone ecosystems and is rarely considered for tropical savannas. Therefore, we analyzed the effects of fire season and history on post‐fire flowering of grass species in a tropical savanna (Cerrado), by evaluating the number of species, frequency of individuals and number of reproductive tillers after wet‐ and dry‐season fires, and under different fire histories.LocationsOpen savannas (campo sujo) of the Cerrado in central Brazil (Reserva Natural Serra do Tombador [RNST], 13°35–13°38′ S, 47°45′–47°51′ W).MethodsWe sampled flowering individuals in 10 Poaceae species and counted flowering/vegetative tillers of grass species in 1 m × 1 m plots after wet‐ and dry‐season fires and under different fire histories (3, 18 and 72 months post fire).ResultsSome of the studied species responded differently to fire according to season but most flowered after fire events. Moreover, the exclusion of fire led to a decrease in the number of flowering individuals and reproductive tillers of grass species.ConclusionsWe describe a unique event for tropical savannas: beside rapid resprout after fire events, grasses can allocate resources for both vegetative and reproductive tiller production, even during the dry season. If fire is excluded from the system, fewer grass species and individuals will flower and there will be a lower percentage of reproductive tillers, showing the importance of fire for grass flowering in these tropical savannas, independently of fire season.

Effects of fire season on the reproductive success of the post-fire flowerer Doryanthes excelsa

Fire is an integral part of many ecosystems and recent record-breaking fires in natural systems around the world are indicative of changes occurring to the fire regime. Fire seasonality is one regime element that is shifting, and can impact the reproductive success of plant species, but rarely receives the spotlight when impacts of fire regimes are studied. We examined the effect of fire season on the reproductive effort and seed resourcing of the post-fire flowering Doryanthes excelsa from eastern Australia. We used field experiments at sites of different soil moisture levels (wet vs dry) burnt in different seasons (summer, autumn, spring) to measure the reproductive output of D. excelsa, including the percentage flowering and the number of seed pods. Seed vigour including seed germination and the percentages of lipids, carbohydrates, and crude proteins of seeds produced after different seasons of burn were analysed. There was a strong effect of fire season on D. excelsa reproduction, with percentage flowering, number of seed pods, germination and lipid levels in seeds all higher after summer compared to spring or autumn burns. Burns outside of summer also delayed flowering. The results of this study highlight the importance of fire and the season in which it occurs in the reproductive success of post-fire flowering species like D. excelsa, a species representative of a functional type often dominant in some fire-prone systems. Importantly, we found that the impacts of season of burn are not merely a product of differences in fire severity. Ongoing climatic changes driving shifts in the fire regime pose an imperative to consider fire season when managing to conserve this important functional group.

High resilience of the mycorrhizal community to prescribed seasonal burnings in eastern Mediterranean woodlands.

Fire effects on ecosystems range from destruction of aboveground vegetation to direct and indirect effects on belowground microorganisms. Although variation in such effects is expected to be related to fire severity, another potentially important and poorly understood factor is the effect of fire seasonality on soil microorganisms. We carried out a large-scale field experiment examining the effects of spring (early-dry season) versus autumn (late-dry- season) burns on the community composition of soil fungi in a typical Mediterranean woodland. Although the intensity and severity of our prescribed burns were largely consistent between the two burning seasons, we detected differential fire season effects on the composition of the soil fungal community, driven by changes in the saprotrophic fungal guild. The community composition of ectomycorrhizal fungi, assayed both in pine seedling bioassays and from soil sequencing, appeared to be resilient to the variation inflicted by seasonal fires. Since changes in the soil saprotrophic fungal community can directly influence carbon emission and decomposition rates, we suggest that regardless of their intensity and severity, seasonal fires may cause changes in ecosystem functioning.

The importance of fire season when managing threatened plant species: A long-term case-study of a rare Leucopogon species (Ericaceae)

Implemented burns are a primary source of fire in natural systems and occur outside of the wildfire season. However, the impacts of fire season shift on native plant species are rarely studied. Understanding fire season effects are particularly important for managing threatened species, which are often the focus of managed burns. To assess the impacts of fire seasonality and identify potential limiting traits, I studied the threatened Leucopogon exolasius and two common congeners, all of which persist via fire-driven population dynamics. All species were monitored over a 16 year period to assess seedling survival, growth and primary juvenile period after fire. For L. exolasius and the common L. esquamatus, comparisons of survival, growth and maturation were made after winter and summer fires, to assess the effects of season of burn. A key difference was found in primary juvenile period, which was exceptionally long for L. exolasius (>11 years for 80% of the population to flower) compared to the common congeners (3.2–7.57 years). Seasonal seed dormancy mechanisms meant that winter fires delayed emergence, leading to increases in primary juvenile period for both species. A long primary juvenile period may limit L. exolasius population persistence because plants are more likely to be killed by subsequent fire before maturation, while seasonal dormancy cues is a trait that would exacerbate the effects of this interval squeeze. In fire-prone systems, fire frequency is the key factor assumed to drive persistence, however, interactions with fire season can influence recruitment success. There are scant data on recruitment variation in response to fire seasonality, a factor that may have broad implications for rare and common species with seasonal germination requirements.

Fire increases the reproduction of the dominant grass Brachypodium retusum and Mediterranean steppe diversity in a combined burning and grazing experiment

AbstractAimsWe assessed what the effects of fire and grazing are on vegetative growth and sexual reproduction of Brachypodium retusum, the dominant species of Mediterranean Thero‐Brachypodietea grasslands (“steppes”) and on species composition of the associated plant community.Location“La Crau”, southeastern France.MethodsWe set up a split‐plot experiment testing the effects of fire season (winter, summer) and grazing on plant cover, inflorescence number, seed set and germination of Brachypodium retusum in traditionally grazed grasslands. We further analyzed plant species composition and diversity in vegetation relevés. The same fire treatments were tested in a second experiment in long‐term grazing exclosures.ResultsBrachypodium retusum showed a rapid post‐fire recovery, but other species of the associated plant community, in particular annuals, recovered as fast or even faster. Fire increased Brachypodium retusum inflorescence production and seed set per inflorescence and this effect was stronger in the summer fire treatment. At the community level, fire significantly increased species richness, evenness and Bray–Curtis dissimilarity in the second post‐fire season and again, the summer fire effect was stronger. Grazing exclusion for two seasons had only a small effect on Brachypodium retusum and the associated plant community. The effect of both fire treatments on Brachypodium retusum was similar in long‐term exclosures. In these exclosures, fire resulted in a community shift towards the species composition of traditionally grazed steppes.ConclusionsThe concomitant positive effects of experimental burning on Brachypodium retusum reproduction and on plant diversity of Mediterranean steppe vegetation suggest that the system is adapted to fire as an important driver of community composition. Annual species surviving as seeds are as successful in post‐fire recovery as perennial resprouters. Prescribed burning may be an alternative strategy to restore community structure in abandoned (ungrazed) steppes showing a decline in typical grassland species after several years of grazing abandonment.

Fire season modifies the perennial plant community composition through a differential effect on obligate seeders in eastern Mediterranean woodlands

AbstractAimPlant species regenerate after fire either through vegetative growth (i.e., obligate resprouters) or seed germination (i.e., obligate seeders), with some species adopting both strategies (i.e., facultative seeders). Fire season can have important consequences for the relative abundance of plant species adopting these regeneration strategies. The present study aimed to test for differential effects of fire season on perennial plant community composition.LocationEastern Mediterranean woodland in the Judea Mountains, Israel.MethodsWe conducted, for the first time, a large‐scale field experiment, involving prescribed spring and autumn burns in a typical eastern Mediterranean woodland. We sampled the perennial plant community before and after the burns, quantifying temporal changes in community composition caused by seasonal fires.ResultsAlthough fire intensity and severity were consistent between the two seasonal fires, plant community composition differed between areas subjected to spring or autumn burns. The abundances of all common species, Pistacia lenticus (obligate resprouter), Cistus spp. (obligate seeders) and Teucrium divaricatum (facultative seeder), were all reduced by both fires. Yet, their dominance in the post‐fire perennial plant community was retained. Differential fire season effects were detected only among obligate seeders, which experienced a stronger reduction in abundance after spring than after autumn burns.ConclusionsDifferential fire season effects on the perennial plant community resulted from phenological rather than fire intensity/severity effects. Such changes in community composition may have important implications for plant community dynamics, because they affect the circle of “fire event–plant regeneration–fire reoccurrence”, determining the probability and intensity of future fires. Furthermore, even though the eastern mediterranean ecosystem is considered highly resilient to disturbances, increased spatio‐temporal variation in fire season, may result in a new vegetation mosaic, differing from the contemporary one, i.e., an alternative stable state.

Legacy effects of prescribed fire season and frequency on soil properties in a Pinus resinosa forest in northern Minnesota

Abstract Prescribed fire is a widely used ecosystem management approach and the vast majority of burns are conducted during the dormant season; however, these burning conditions (and therefore the type and persistence of fire effects) often differ from those of natural or historical fire regimes. Therefore, we leveraged a historical study (conducted 1959–70) with remeasurements in 2015 to evaluate effects of fire season (dormant, summer), frequency (annual, biennial, periodic), and their interaction on soil physical and chemical properties in a red pine (Pinus resinosa Ait.) forest in northern Minnesota, USA. To protect against across-year differences in sampling and analysis, we used a meta-analysis approach to evaluate treatment effects on soil properties. We also used non-metric multidimensional scaling (NMDS) ordination to investigate legacy (>45 years post-fire) treatment effects. The greatest effects of fire occurred in organic horizons, and decreased with depth. In the short-term, fire decreased organic horizon depths and nitrogen (N) and increased base cations (K, Ca, Mg) and pH in the mineral soil, whereas effects on phosphorus (P) were variable. Prescribed fire treatments had legacy effects on organic horizon and mineral soil properties >45 years post-fire. In general, summer burns decreased nutrient stocks, whereas dormant season burns increased nutrient stocks, and the majority of legacy effects occurred in annual burn treatments, in both seasons. Legacy effects of summer burns decreased organic horizon depths, organic matter, nutrient stocks (N, P, K), and pH, as well as lower (0–15 cm) mineral soil N; whereas, the dormant annual burn increased Ca in the total forest floor and N and P in the upper (15–91 cm) mineral soil. In contrast, the summer annual burn increased P, whereas the dormant annual burn decreased pH in the lower mineral soil. Trends in short- and long-term effect sizes appeared to differ by season of burning and further magnified by increased fire frequency within season. Relative to dormant season burns, summer burns resulted in immediate and long-lasting desirable effects for red pine ecosystems (e.g., decreased forest floor depths and nutrient stocks) without persistent undesirable effects (e.g., increased nutrient stocks or changes in cation exchange capacity, soil texture, and bulk density) in the mineral soil. Our results suggest that summer burns may be a valuable approach to increase the variability in burn schedules representative of historical regional fire regimes in red pine forests, and may help promote soil characteristics that support overall ecosystem health.

Variability in Fire Prescriptions to Promote Wildlife Foods in the Longleaf Pine Ecosystem

AbstractPrescribed fire is commonly used to restore and maintain the longleaf pine (Pinus palustris Mill.) ecosystem (LLPE). A key function of the LLPE is the provisioning of food for wildlife. Despite the plethora of literature evaluating the effects of fire season and fire-return interval on plant community dynamics, little attention has been given to the response of wildlife foods to fire season or fire-return interval. We measured the availability of key wildlife foods (fleshy fruit [i.e., seed containing a nutritious pericarp] and understory plant biomass) in upland pine forest following dormant-season (December–February) and growing-season (April–June) fires in a chronosequential design. Also, we quantified the relative contributions of the upland hardwood and bottomland hardwood forest types, which often are intentionally suppressed in the LLPE. In 2011 and 2012, we measured understory leafy biomass, biomass of forages selected by whitetailed deer (Odocoileus virginianus Zimm.), and soft mast production chronosequentially in relation to years-since-fire, fire season, and vegetation type in the LLPE at Fort Bragg Military Installation, North Carolina, USA. Understory leafy biomass increased in upland pine and hardwood forests as years-since-fire increased until two years post fire. Selected forages decreased in upland pine forest and increased in upland hardwood forest as time-since-fire increased. In upland pine forests burned during the growing season, 94% of the fruit was detected two years after fire, 6% one year after fire, and 0% the same year as fire. In June, fruit density was greatest in bottomland hardwood forest; in July, fruit density was greatest in dormant-season burned upland pine forest; in August, fruit density was greatest in upland hardwood forest; and in September, fruit density was greatest in upland hardwood and bottomland hardwood forest. Overall summer fruit density (i.e., the sum of fruit density detected each month) was greatest in upland hardwood forest. Understory leafy biomass and deer-selected forages were stable in bottomland hardwood forest because they were not burned, thereby providing a relatively high and stable availability from year to year. Our data demonstrate the importance of diversity in fire season and frequency, and diversity in vegetation types to promote key wildlife foods in the LLPE.

Prescribed fire affects female white-tailed deer habitat use during summer lactation

Prescribed fire commonly is used to manage habitat for white-tailed deer (Odocoileus virginianus). Although the effects of fire on forage availability for deer have been studied, how female deer use burned areas is not well known, particularly as it relates to fire season and the years-since-fire. We used GPS tracking data from 16 adult female white-tailed deer to assess the effects of fire season and years-since-fire on habitat use during summer lactation. Females selected unburned drainages and older (>1yr-since-fire) burned areas, and avoided recently burned areas. Individuals with a greater percentage of their summer core area burned expanded the size of their summer home range but did not change summer core area size. Furthermore, summer core area site fidelity (i.e., % overlap between 2011 and 2012 core areas) decreased as the percentage of the 2011 summer core area burned in 2012 increased. Female deer increased selection of burned areas as years-since-fire increased, likely because there was a temporary loss of cover immediately following fire with plants slowly regenerating the subsequent growing seasons. Likewise, to avoid areas depleted of cover, females shifted their core areas away from recent burns when possible but increased their core area size when burned areas were unavoidable (i.e., a large portion of their home range was burned). Burning large contiguous areas may initially have a negative effect on female deer during lactation because of the depletion of cover.

Vegetation Dynamics After Spring and Summer Fires in Red and White Pine Stands at Voyageurs National Park

ABSTRACT: Conducting dormant season or springtime prescribed fire treatments has become a common practice in many regions of the United States to restore ecosystems to their natural state. Despite the knowledge that historically, fires often occurred during the summer, the application of summer burns has been deterred, in part, by a lack of understanding of fire season effects on vegetation. We explored the differences in fire effects between spring and summer burns at Voyageurs National Park, Minnesota. The fire season effects on the ground layer vegetation were clearly different among the treatments: pre-burn, spring, and summer. Vegetation composition of pre-burn and after spring fires was similar, but differed significantly from the summer fires. Spring fires propagated the same species that were present prior to the fire, whereas summer fires promoted a new suite of species through the germination of seedbank and high seed dispersal species. Cover and richness of seed bank and intolerant species were...

Fire Season Effects on Flowering Characteristics and Germination of Longleaf Pine (Pinus palustris) Savanna Grasses

Pinus palustris (longleaf pine) savannas depend on contiguous grass cover to facilitate frequent surface fires. Enhanced flowering, seed production, and germination may be linked to season of fires. We assessed the effect of month of prescribed fire (February, April, May, and July) on percentage of plants with flowering culms (FCs%), FC/area, FC/plant, seed production, and germination for five warm seasons, fall‐flowering grasses. Multivariate analysis indicated the response of flowering and fruiting to burn month varied among the grass species. The dominant species, Sporobolus junceus and Schizachyrium scoparium var. stoloniferum, had greater numbers of most flowering characteristics when burnt during April, May, and July. Aristida purpurascens had increased FC/plant after May and July burns. In contrast, Ar. mohrii had the fewest FC/plant and seeds/FC when burnt in July. Germination was greatest (26–60%) for Ar. purpurascens. Seeds collected following July burns for Ar. purpurascens and Ar. ternarius and after May burns for S. junceus were within the highest germination values recorded. Germination of Sc. scoparium var. stoloniferum was very low after February and July burns (≤5%). With Ar. mohrii, only seed collected following February (2%) and April burns (3%) germinated. April, May, and July fires increased seed production of dominant matrix grasses, thus facilitating the potential for recruitment of these species and facilitating seed collection from potential donor sites for ground‐layer restoration projects. Varying prescribed fire burn month captured variation in flowering characteristics among these grasses.

Growing-Season Disturbance in Tallgrass Prairie: Evaluating Fire and Grazing on Schizachyrium scoparium

Historically, fire occurred throughout the year in the Great Plains, but current fire prescriptions are generally limited to the dormant season because of concerns for potential damage to fire-sensitive herbaceous plant species deemed economically and ecologically important. We coupled a field-based study and a controlled greenhouse study to quantify the effects of fire season and herbivory on plant species composition, along with survival and productivity of little bluestem (Schizachyrium scoparium [Michx.] Nash). We investigated the effects of both dormant and growing-season fire interacting spatially with grazing on plant community composition in a 10-yr field study. We also examined the influence of both growing-season fire and clipping on survival and aboveground and belowground production of potted little bluestem plants at multiple ages in a controlled greenhouse experiment. Plants were grown to 6 wk, 10 wk, or 18 wk, then either burned or clipped, followed by as many as two successive clipping events. Plant community composition and canopy cover of little bluestem were unaffected by season-of-burning in the field study. Survival of individual little bluestem seedlings in the greenhouse study was dependent primarily on plant age, with nearly 100% survival among all burning and clipping treatments at 18 wk old. Burning or clipping once did not decrease survival compared to seedlings that were not burned or not clipped, and burning followed by clipping did not decrease survival over multiple clipping events among 6-wk-, 10-wk-, or 18-wk-old plants. Both aboveground regrowth and belowground biomass increased with burning, but clipping reduced regrowth. Based on both field and greenhouse experiments, we conclude that little bluestem is well adapted to growing-season disturbance. Moreover, little bluestem responds more positively to growing-season fire than to clipping. Our results provide no evidence that little bluestem should be deferred from grazing after burning as part of a rangeland management strategy.

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.

Fire season and simulated grazing differentially affect the stability and drought resilience of a C 4 bunchgrass, C 3 bunchgrass and C 4 lawngrass

We used a fully factorial experimental design to examine the effects of fire season, simulated grazing and their interaction on the temporal stability (year-to-year variation in production) of the C 4 bunchgrass, Bouteloua curtipendula, the C 3 bunchgrass, Nassella leucotricha, and the C 4 lawngrass, Buchloe dactyloides. Treatments included three levels of fire (winter fire, summer fire, and no fire) and two levels of grazing (simulated grazing and no grazing). Additionally, a severe drought during the fourth year of the five year study allowed us to examine each species’ post-drought resilience. In the southern Great Plains, USA, these three perennial grass species are economically and ecologically important; each species is a dominant member of their functional group and important as livestock forage. Temporal stability and drought resilience of the C 4 bunchgrass, Bouteloua, were significantly greatest in the summer fire treatments. In contrast, temporal stability of the C 3 bunchgrass, Nassella, was significantly greatest in the no-fire treatments and its drought resilience was significantly greatest in the no-graze treatments. Temporal stability and drought resilience of the C 4 lawngrass, Buchloe, were not affected by any of the treatments. The contrasting effect of fire on the C 4 and C 3 bunchgrasses is consistent with the hypothesis that fire favors C 4 over C 3 grasses due to differences in post-fire soil conditions such as increased temperature, reduced moisture and reduced mineralizable nitrogen.

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).

Restoring fire as an ecological process in shortgrass prairie ecosystems: initial effects of prescribed burning during the dormant and growing seasons

Prior to Anglo-European settlement, fire was a major ecological process influencing the structure, composition and productivity of shortgrass prairie ecosystems on the Great Plains. However during the past 125 years, the frequency and extent of grassland fire has dramatically declined as a result of the systematic heavy grazing by large herds of domestic cattle and sheep which reduced the available levels of fine fuel and organized fire suppression efforts that succeeded in altering the natural fire regime. The greatly diminished role of recurrent fire in these ecosystems is thought to be responsible for ecologically adverse shifts in the composition, structure and diversity of these grasslands, leading specifically to the rise of ruderal species and invasion by less fire-tolerant species. The purpose of this study was to evaluate the ecological effects of fire season and frequency on the shortgrass prairie and to determine the means by which prescribed fire can best be restored in this ecosystem to provide the greatest benefit for numerous resource values. Plant cover, diversity, biomass and nutrient status, litter cover and soil chemistry were measured prior to and following fire treatments on a buffalograss-blue grama shortgrass prairie in northeastern New Mexico. Dormant-season fire was followed by increases in grass cover, forb cover, species richness and concentrations of foliar P, K, Ca, Mg and Mn. Growing-season fire produced declines in the cover of buffalograss, graminoids and forbs and increases in litter cover and levels of foliar P, K, Ca and Mn. Although no changes in soil chemistry were observed, both fire treatments caused decreases in herbaceous production, with standing biomass resulting from growing-season fire ∼ 600 kg/ha and dormant-season fire ∼1200 kg/ha, compared with controls ∼1800 kg/ha. The initial findings of this long-term experiment suggest that dormant-season burning may be the preferable method for restoring fire in shortgrass prairie ecosystems where fire has been excluded for a prolonged time period.

FIRE EFFECTS ON RESPROUTING OF SHRUBS IN HEADWATERS OF SOUTHEASTERN LONGLEAF PINE SAVANNAS

Woody plants in fire-frequented ecosystems commonly resprout from underground organs after fires. Responses to variation in characteristics of fire regimes may be a function of plant physiological status or fire intensity. Although these hypotheses have been explored for trees in southeastern longleaf pine (Pinus palustris) savannas, responses of other life forms and stages have not been studied. We examined effects of fire season and frequency, geography, habitat, and underground organ morphology on resprouting of shrubs. In 1994, we located replicated sites, each containing two habitats, upslope savannas and downslope seepages, in Louisiana and Florida. Each site, which contained quadrats located along transects within a 30 × 60 m plot, was burned either during the dormant or growing season and then reburned similarly two years later. Maximum fire temperatures were measured, and densities of shrub stems were censused in quadrats before and after fires. Shrubs collectively resprouted more following dorma...