Effects of re‐introducing fire to a central Florida sandhill community

Abstract. A southern ridge sandhill site in central Florida, USA, was burned in 1989, 1991, and 1995 after 63 years of fire‐suppression to simulate a pre‐settlement fire regime. Fire changed species abundance and vegetation structure but caused only minimal changes in species turnover and diversity. There was a general trend for an increase in the cover of herbs following fire but this was a statistically significant effect for only one species, Liatris tenuifolia var. tenuifolia. Aristida beyrichiana increased, litter cover and litter depth were significantly reduced, and ground lichens were eliminated in response to burning. Scrub oaks and palmettos in the ground cover and small shrub layers (height ≤ 1 m) either increased or did not respond to burning, reflecting strong post‐fire resprouting. Diversity in the ground cover and small shrub layers were not affected by fire. Scrub oaks and palmettos in the large shrub and overstorey layers (height > 1 m) were reduced in density, basal area, and longest canopy measurements in response to fire. Species diversity also decreased within these layers following fire. Some Pinus elliottii var. densa survived fire, but their density was reduced. All Pinus clausa were eliminated by fire. Periodic burning can suppress the dominance of shrubs (Quercus spp.) while increasing the cover of grasses and herbs in southern ridge sandhill vegetation.     

Fire and soil-plant nutrient relations in a pine-wiregrass savanna on the coastal plain of North Carolina

Summary Changes in soil and plant nutrient conditions were evaluated following various burn and clip treatments in a longleaf pine-wiregrass savanna in Bladen Co., N.C., USA. Ground fires were found to add substantial quantities of N, P, K, Ca, and Mg to the soil, though not necessarily in forms immediately available to plants. Less than 1% of the total nitrogen in the charred residue (ash) is present as nitrate or ammonium. Considerable quantities of all nutrients examined were lost to the atmosphere during burning. Green leaf tissue in recently burned areas was consistently higher in N, P, K, Ca, and Mg compared to unburned areas. Howerver, when compared to similar tissues from clipped plots, burned area tissues were significantly higher in N, Ca, and Mg only. Data presented here suggest that tissue age significantly affects nutrient content and must be considered in any analysis of tissue nutrient content following burning. Within 4–6 months following fire, burned-area tissue nutrient content decreases to concentrations found in the unburned area. Burning resulted in initial enrichment of available soil nutrients including PO₄, K⁺, Ca⁺⁺, and Mg⁺⁺, however, NO₃ ^-, and NH₄ ⁺ concentrations in burned soil were not significantly different from unbruned soil. Soil and plant nutrient changes in an area burned two years in succession indicate that repeated burning may diminish nutrient availability. Plant response to various nutrient enrichment treatments of the soil indicated that nitrogen is limiting growth in both burned and unburned soils and that burning may alter some factors other than nutrients which may retard plant growth in unburned areas.     

Factors Regulating Nitrogen Retention During the Early Stages of Recovery from Fire in Coastal Chaparral Ecosystems

Fire is a fundamental reorganizing force in chaparral and other Mediterranean-type ecosystems. Postfire nutrient redistribution and cycling are frequently invoked as drivers of ecosystem recovery. The extent to which N is transported from slopes to streams following fire is a function of the balance between the rate at which soil microbes retain and metabolize N into forms that readily dissolve or leach, and how rapidly recovering plants sequester this mobilized N. To better understand how fire impacts this balance, we sampled soil and plant N dynamics in 17 plots distributed across two burned, chaparral-dominated watersheds in Santa Barbara County, California. We measured a variety of ecosystem properties in both burned and unburned plots on a periodic basis for 2 years, including soil water content, pH, soil and plant carbon and nitrogen, extractable inorganic nitrogen, dissolved organic nitrogen, and microbial biomass. In burned plots, nitrification was significantly enhanced relative to rates measured in unburned plots. Ephemeral herbs established quickly following the first postfire rain events. Aboveground plant biomass assimilated N commensurate with soil net mineralization, implying tight N cycling during the early stages of recovery. Microbial biomass N, on the other hand, remained low throughout the study. These findings highlight the importance of herbaceous species in conserving ecosystem nutrients as shrubs gradually recover.     

兴安落叶松林不同强度火烧迹地土壤微生物群落特性研究

通过选取大兴安岭岭北部的兴安落叶松林重度、轻度火烧迹地以及为过火样地,运用磷脂脂肪酸分析方法（PLFAs）,研究了火烧对0~5和5~10 cm土层的土壤理化性质和土壤微生物群落的结构特征的影响,并探讨了火烧当年土壤微生物群落生物量和群落结构的变化规律与影响因素。研究结果表明：0~5和5~10 cm土层的土壤pH、全钾、有效磷、黏砂比等土壤理化指标受到了火烧的显著性影响;不同火烧程度对微生物类群的生物量有影响,但不显著;重度火烧迹地的土壤微生物的群落结构指标革兰氏阳性菌/革兰氏阴性菌（G+/G-）以及真菌/细菌（F/B）与轻度和未过火样地具有显著差异。RDA分析指出,G+/G-受土壤含水量影响最大,F/B受pH影响最大。说明在火烧迹地的当年,土壤水分和pH是影响土壤微生物群落结构的最重要因素。     

Causes of increased nutrient concentrations in post-fire regrowth in an East African savanna

The aim of the present study was to investigate the causes of increased macronutrient concentrations in above-ground post-fire regrowth in an East African savanna (Northern Tanzania). Experiments were set up to discriminate between the following possible causes: (1) increased soil nutrient supply after fire, (2) relocation of nutrients from the roots to the new shoots, (3) rejuvenation and related changes in plant tissue composition and (4) changes in nutrient uptake in relation to above-ground carbon gains. N, P, K, Ca and Mg concentrations in post-burn graminoid vegetation were compared with clipped and with unburned, control vegetation during the post-burn growth season. One month after burning and clipping, nutrient concentrations in live grass shoots in the burned and clipped treatments were significantly higher than in the control. This effect, however, declined in the course of the season and, except for Ca, disappeared three months after onset of the treatments. There were no significant differences in live grass shoot nutrient concentrations between burned and clipped treatments which suggests that the increased nutrient concentration in post-fire regrowth is not due to increased soil nutrient supply via ash deposition. The relatively low input of nutrients through ash deposition, compared to the amount of nutrients released through mineralisation during the first month after burning and to the total nutrient pools, supports this suggestion. There was no difference between burned and unburned vegetation in total root biomass and root nutrient concentrations. Relocation of nutrients from the roots to the new shoots did not, therefore, appear to be a cause of higher post-fire shoot nutrient concentrations. The present study shows that in this relatively nutrient-rich savanna, the increased nutrient concentration in above-ground post-fire regrowth is primarily due to increased leaf:stem ratios, rejuvenation of plant material and the distribution of a similar amount of nutrients over less above-ground biomass. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of fire intensity on understory composition and diversity in aKalmia-dominated oak forest, New England, USA

This study investigates the understory dynamics of two mixed-oak stands following fire of varying intensity. Composition and diversity of woody and herbaceous species in the understory were measured in two stands 7–8 years after a prescribed burn. On both sites, unburned areas, low-intensity fire areas, and areas where the overstory had been severely damaged were measured. Patterns of species presence and absence following fire were consistent with an initial-floristics model. Most species increased in density and frequency following fire; onlyAralia nudicaulis andQuercus alba showed statistically significant decreases in density. Overall, 29 species increased in density following fire, while 8 declined; 29 species increased in frequency, while 6 declined. However, diversity and equitability measures were depressed on the moderately burned sites, due to rapid regrowth ofKalmia latifolia. Ordination using binary discriminant analysis suggested species responded individualistically to both burning and site variation.     

Wildfire reduces carbon dioxide efflux and increases methane uptake in ponderosa pine forest soils of the southwestern USA

Severe wildfire may cause long-term changes in the soil-atmosphere exchange of carbon dioxide and methane, two gases known to force atmospheric warming. We examined the effect of a severe wildfire 10?years after burning to determine decadal-scale changes in soil gas fluxes following fire, and explored mechanisms responsible for these dynamics. We compared soil carbon dioxide efflux, methane uptake, soil temperature, soil water content, soil O horizon mass, fine root mass, and microbial biomass between a burned site and an unburned site that had similar stand conditions to the burned site before the fire. Compared to the unburned site, soil carbon dioxide efflux was 40% lower and methane uptake was 49% higher at the burned site over the 427-day measurement period. Soil O horizon mass, microbial biomass, fine root mass, and surface soil water content were lower at the burned site than the unburned site, but soil temperature was higher. A regression model showed soil carbon dioxide efflux was more sensitive to changes in soil temperature at the burned site than the unburned site. The relative importance of methane uptake to carbon dioxide efflux was higher at the burned site than the unburned site, but methane uptake compensated for only 1.5% of the warming potential of soil carbon dioxide efflux at the burned site. Our results suggest there was less carbon available at the burned site for respiration by plants and microbes, and the loss of the soil O horizon increased methane uptake in soil at the burned site.     

Responses in plant, soil inorganic and microbial nutrient pools to experimental fire, ash and biomass addition in a woodland savanna

In order to investigate the effects of savanna fires on nutrient cycling a field experiment was carried out in an open woodland savanna of southwest Ethiopia. This involved manipulations of fire, fuel load and ash fertilisation in a fully factorial design, and recording of responses in plants, soil inorganic and microbial nutrient pools up to 1 year after the disturbances. As plant biomass nitrogen (N) was only 3.5% of that in topsoil the N loss in a single fire event was relatively small. The microbial N pool size in the topsoil was similar to the N pool size in the aboveground part of the plants. Soil microbial biomass carbon increased slightly 12 days after the low severity fire, but the effect was transient and was not accompanied by an increase in microbial N. Instead, the soil inorganic N concentration increased strongly 1 day after the fire, remained higher up to 3 months after the fire and probably caused the 40% higher grass biomass in burned than unburned plots, and the similar sized increase in grass nitrogen, phosphorus and potassium pools in the following rainy season. In contrast, broad-leaved herbs showed less strong increments in biomass and nutrient pool sizes. Fire interacted with fuel load, as burning of plots with double plant biomass led to reduced microbial biomass, plant nutrient pools and herb (but not grass) biomass. Low-severity-fire nutrient losses appear to be moderate and may be replenished from natural sources. However, in areas with frequent fires and high grass biomass (fuel) loads, or with late fires, nutrient losses could be much larger and non-sustainable to the persistence of the woodland savanna ecosystem.     

The impact of wildfire on vesicular-arbuscular mycorrhizal fungi and their potential to influence the re-establishment of post-fire plant communities

Wildfires are a typical event in many Australian plant communities. Vesicular-arbuscular mycorrhizal (VAM) fungi are important for plant growth in many communities, especially on infertile soils, yet few studies have examined the impact of wildfire on the infectivity of VAM fungi. This study took the opportunity offered by a wildfire to compare the infectivity and abundance of spores of VAM fungi from: (i) pre-fire and post-fire sites, and (ii) post-fire burned and unburned sites. Pre-fire samples had been taken in May 1990 and mid-December 1990 as part of another study. A wildfire of moderate intensity burned the site in late December 1990. Post-fire samples were taken from burned and unburned areas immediately after the fire and 6 months after the fire. A bioassay was used to examine the infectivity of VAM fungi. The post-fire soil produced significantly less VAM infection than the pre-fire soil. However, no difference was observed between colonization of plant roots by VAM fungi in soil taken from post-fire burned and adjacent unburned plots. Soil samples taken 6 months after the fire produced significantly more VAM than corresponding soil samples taken one year earlier. Spore numbers were quantified be wet-sieving and decanting of 100-g, air-dried soil subsamples and microscopic examination. For the most abundant spore type, spore numbers were significantly lower immediately post-fire. However, no significant difference in spore numbers was observed between post-fire burned and unburned plots. Six months after the fire, spore numbers were the same as the corresponding samples taken 1 year earlier. All plants appearing in the burned site resprouted from underground organs. All post-fire plant species recorded to have mycorrhizal associations before the fire had the same associations after the fire, except for species of Conospermum (Proteaceae), which lacked internal vesicles in cortical cells in the post-fire samples.     

Effects of wildfire and permafrost on soil organic matter and soil climate in interior Alaska

The influence of discontinuous permafrost on ground‐fuel storage, combustion losses, and postfire soil climates was examined after a wildfire near Delta Junction, AK in July 1999. At this site, we sampled soils from a four‐way site comparison of burning (burned and unburned) and permafrost (permafrost and nonpermafrost). Soil organic layers (which comprise ground‐fuel storage) were thicker in permafrost than nonpermafrost soils both in burned and unburned sites. While we expected fire severity to be greater in the drier site (without permafrost), combustion losses were not significantly different between the two burned sites. Overall, permafrost and burning had significant effects on physical soil variables. Most notably, unburned permafrost sites with the thickest organic mats consistently had the coldest temperatures and wettest mineral soil, while soils in the burned nonpermafrost sites were warmer and drier than the other soils. For every centimeter of organic mat thickness, temperature at 5 cm depth was about 0.5°C cooler during summer months. We propose that organic soil layers determine to a large extent the physical and thermal setting for variations in vegetation, decomposition, and carbon balance across these landscapes. In particular, the deep organic layers maintain the legacies of thermal and nutrient cycling governed by fire and revegetation. We further propose that the thermal influence of deep organic soil layers may be an underlying mechanism responsible for large regional patterns of burning and regrowth, detected in fractal analyses of burn frequency and area. Thus, fractal geometry can potentially be used to analyze changes in state of these fire prone systems.     

Slash Pile Burning Effects on Soil Biotic and Chemical Properties and Plant Establishment: Recommendations for Amelioration

Ponderosa pine forest restoration consists of thinning trees and reintroducing prescribed fire to reduce unnaturally high tree densities and fuel loads to restore ecosystem structure and function. A current issue in ponderosa pine restoration is what to do with the large quantity of slash that is created from thinning dense forest stands. Slash piling burning is currently the preferred method of slash removal because it allows land managers to burn large quantities of slash in a more controlled environment in comparison with broadcast burning slash. However burning slash piles is known to have adverse effects such as soil sterilization and exotic species establishment. This study investigated the effects of slash pile burning on soil biotic and chemical variables and early herbaceous succession on burned slash pile areas. Slash piles were created following tree thinning in two adjacent approximately 20‐ha ponderosa pine (Pinus ponderosa) restoration treatments in the Coconino National Forest near Flagstaff, Arizona. We selected 30 burned slash pile areas and sampled across a gradient of the burned piles for arbuscular mycorrhizal (AM) propagule densities, the soil seed bank, and soil chemical properties. In addition, we established five 1‐m² plots in each burned pile to quantify the effect of living soil (AM inoculum) and seeding amendments on early herbaceous succession in burned slash pile areas. The five treatments consisted of a control (no treatment), living soil (AM inoculum) amendment, sterilized soil (no AM inoculum) amendment, seed amendment, and a seed/soil (AM inoculum) amendment. Slash pile burning nearly eliminated populations of viable seeds and AM propagules and altered soil chemical properties. Amending scars with native seeds increased the cover of native forbs and grasses. Furthermore adding both seed and living soil more than doubled total native plant cover and decreased ruderal and exotic plant cover. These results indicate that seed/soil amendments that increase native forbs and grasses may enhance the rate of succession in burned slash pile areas by allowing these species to outcompete exotic and ruderal species also establishing at the site through natural regeneration.     

Complex Effects of Prescribed Fire on Restoring the Soil Water Content in a High-Elevation Riparian Meadow, Arizona

One of the largest and rarest Bebb willow (Salix bebbiana) communities in the United States occurs at Hart Prairie, Arizona. Low recruitment of the willow over the past several decades has been linked to inadequate soil water content for seed germination and seedling establishment. We tested a hypothesis that a prescribed burn would reduce biomass of and evapotranspiration by herbaceous plants, thereby increasing soil water content. Three treatments (unburned control, early‐growing season burned, late‐growing season burned) were applied in year 2001 to replicated plots in fern‐ and grass‐dominated herbaceous communities. Soil water content (0–30 cm) was measured weekly in plots during the 2001, 2002, and 2003 growing seasons. Both early‐ and late‐season burning reduced herbaceous biomass in the fern‐dominated community in 2002 and 2003 and reduced biomass in the grass‐dominated community in 2002 but not in 2003. Soil water content increased for approximately four weeks in 2001 following the early‐season burn, but the early‐season and late‐season burns reduced soil water content in both communities over much of the 2002 and 2003 growing seasons. Thus, early‐season burning may benefit willow seed germination by increasing soil water content immediately following burning but be detrimental to germination in the second and third growing seasons after burning because of drier soil. Large temporal variation in the effect of prescribed burning on soil water content will complicate the use of fire as a restoration tool to manage soil water available for threatened plants such as Bebb willow and for recharge of groundwater.     

Leaf‐cutting ants,seasonal burning and nutrient distribution in Cerrado vegetation

Abstract Fire and herbivory are known to modify plant community structure. Many studies have suggested that fire ashes may increase soil nutrients in dystrophic soils. Herbivores may also change plant community structure through direct effects of herbivory and affecting nutrient cycling. Leaf‐cutting ants were traditionally viewed as herbivores, although their role may be more complex, because their nests affect both chemical and physical soil properties, thus affecting plants indirectly. We investigated the effects of frequent burning and of leaf‐cutting ants on the nutrient status of an herbaceous and a shrub species occurring in the Brazilian Cerrado, a habitat that is characterized by natural burnings. The proximity of ant nests resulted in an increase of nutrients in the leaves of both vegetation strata, whereas burning sometimes resulted in a decrease of nutrients. Our results do not lead to a possible positive effect of fire on plant nutrient content. On the other hand, ant nests may represent an important source of nutrients for plants on the nutrient‐depleted Cerrado soils and may accelerate vegetation recovery after burning.     

Burning in a New Zealand snow-tussock grassland: Effects on soil microbial biomass and nitrogen and phosphorus availability

Fire has been an important management tool in the pastoral use of New Zealand tussock grasslands. The effects of a farm-scale pastoral fire and subsequent grazing by sheep on soil biochemical properties in tussock grasslands dominated by the narrow-leaved snow tussock (Chionochloa rigida ssp. rigida) were investigated, 1.5 and 2.5 years after the fire event, in 0-2 cm depth mineral soil at a site at 975 m altitude in Central Otago, New Zealand. The nitrogen (N) and phosphorus (P) concentrations of C. rigida leaves were also measured. Comparisons were made with soil and tussock leaves from an adjacent unburned site. At both samplings, values of total soil organic carbon (C), extractable C, microbial biomass C, and basal respiratory activity were, on average, 14%, 18%, 23%, and 40%, respectively, lower at the burned than at the unburned site. In contrast, microbial N values were roughly similar at both sites, while microbial P values were 42% higher at the burned site after 1.5 years. Phosphomonoesterase and phosphodiesterase activities were then also similar at both sites, whereas invertase activity was higher at the burned site. The greater availability of N and P at the burned site was confirmed by the higher concentrations of N and P in C. rigida leaves sampled 2 years after the fire. Ratios of microbial C:microbial N and microbial C:microbial P were significantly lower at both samplings at the burned site, and emphasise the importance of the soil microbial biomass in conserving N and P after pastoral burning in a grassland ecosystem.     

Basidiomycete fungal communities in Australian sclerophyll forest soil are altered by repeated prescribed burning

Soil basidiomycetes play key roles in forest nutrient and carbon cycling processes, yet the diversity and structure of below ground basidiomycete communities remain poorly understood. Prescribed burning is a commonly used forest management practice and there is evidence that single fire events can have an impact on soil fungal communities but little is known about the effects of repeated prescribed burning. We have used internal transcribed spacer (ITS) terminal restriction fragment length polymorphism (T-RFLP) analysis to investigate the impacts of repeated prescribed burning every two or four years over a period of 30 years on soil basidiomycete communities in an Australian wet sclerophyll forest. Detrended correspondence analysis of ITS T-RFLP profiles separated basidiomycete communities in unburned control plots from those in burned plots, with those burned every two years being the most different from controls. Burning had no effect on basidiomycete species richness, thus these differences appear to be due to changes in community structure. Basidiomycete communities in the unburned control plots were vertically stratified in the upper 20 cm of soil, but no evidence was found for stratification in the burned plots, suggesting that repeated prescribed burning results in more uniform basidiomycete communities. Overall, the results demonstrate that repeated prescribed burning alters soil basidiomycete communities, with the effect being greater with more frequent burning.     

Mycorrhizal colonization of Palafoxia feayi (Asteraceae) in a pyrogenic ecosystem

Although a number of factors have predictable effects on mycorrhizal colonization, determining generalized patterns for some variables have remained elusive. In particular, fire has been identified as a major event that may influence plant–mycorrhiza interactions, yet efforts to date have yielded contradictory results. Here, we assess the impact of fire on mycorrhizal colonization in Palafoxia feayi, a plant commonly found in the fireswept, nutrient-poor scrub community of central Florida. We determined soil nutrient conditions and percent colonization patterns for plants growing in replicate plots that were burned 1 to 15 years previously. The results showed a negative relationship between mycorrhizal colonization and time since fire, but there was no effect of fire return interval (lapsed time between successive fires). Soil nutrient analyses corroborated previous studies and showed no change in soil nutrients following fire. In contrast to previous studies of mycorrhizal colonization in Florida scrub, we conclude that fire can affect arbuscular mycorrhizal fungi colonization and we speculate that this is mediated by light availability.     

The effect of fire on nutrients in a pine forest soil

The effect of a hot summer fire on soil nutrient contents in the upper 2 cm of Aleppo pine forest with a dense woody understory was studied from September 1985 to May 1986. In comparison with the adjacent unburned forest, total nitrogen decreased by 25% but available forms of nitrogen were much higher. In burned and unburned soils there was a similar trend to increase and decrease in NH ₄ ⁺ −N, However, while (NO ₂ ⁻ +NO ₃ ⁻ −N decreased in the unburned soil it rose rapidly in the burned ash soil. Total phosphorus increased by 300% after the fire but decreased again 2 months later. Also water-soluble P increased up to November and then decreased to the levels of the unburned soils. The same was true for electrical conductivity and pH, increasing immediately after the fire and then leveling off again. This increase in nutrient levels in the “ash soil” was reflected in the striking increase in shoot and root biomass and in the content of N, P, Mg, K, Ca, Zn and Fe in wheat and clover plants grown in pots in these soils. These nutrient levels were much higher in the wheat plants, which also produced 12 times more seeds in the “ash soil.” It seems that fire in these pine forests causes a short-term flush of the mineral elements in the upper “ash soil” layer which is reverted gradually via the herbaceous post-fire to the ecosystem.     

大兴安岭火烧迹地恢复初期土壤微生物群落特征

对大兴安岭兴安落叶松2003年重度和中度火烧迹地以及未过火样地的土壤微生物群落进行了考察,旨在揭示火烧迹地恢复初期土壤微生物群落变化特征。研究结果表明火烧迹地土壤养分(全氮、全碳、土壤有机质、有效氮)和土壤水分与未过火对照样地存在显著差异;火烧迹地土壤微生物量碳氮、微生物代谢活性以及碳源利用能力均显著高于对照样地;但火烧迹地与对照样地土壤微生物群落结构指标土壤微生物量碳氮比(MBC/MBN)以及多样性指数没有显著差异。相关分析结果表明:土壤微生物量、代谢活性和碳源利用能力与土壤养分指标(全碳、全氮、速效氮、有机质)和土壤水分含量有显著相关性。主成分分析的结果表明火烧与否是火烧样地与对照样地土壤微生物对碳源利用能力差异的原因。所有样地土壤微生物群落真菌比例较高,可能与该地区土壤酸碱度有关(pH=4.12—4.68)。经过6a的恢复,重度和中度火烧迹地的土壤养分和水分、土壤微生物群落的生长、代谢、以及群落多样性仍存在差异,但均不显著,表明此时火烧程度对土壤微生物群落的影响已很微弱。     

Nutrient dynamics of vegetation and detritus following two intensities of fire in the New Jersey pine barrens

The nutrient dynamics of upland forest sites in the New Jersey Pine Barrens exposed to different fire intensities were determined. Nutrient concentrations and inventories in biomass, litter, humus, and standing dead wood were determined for an unburned site, two sites burned by severe wildfire and two sites burned by light prescribed burning. Humus nutrient levels were similar among sites despite differing fire histories. Amounts of calcium, magnesium, and potassium in biomass and in litter were lower in wildfire sites than in prescribed burn sites, all of which were lower than the control. Standing dead wood nutrient levels were much higher in the wildfire sites than in the other three sites. Output of nutrients to groudwater correlated poorly with the amounts of nutrients retained in humus or standing dead wood; however strong inverse correlations were found between nutrient output and nutrient storage in biomass or biomass plus litter and humus. These results emphasize the central role of nutrient immobilization in regrowing biomass in after fire on nutrient poor soils.     

Elk grazing and vegetation responses following a late season fire in Yellowstone National Park

We studied responses of aboveground production, grazing by elk and the availability of eight elements (Ca, Fe, K, Mg, N, Na, P, Zn) in a Yellowstone National Park sagebrush grassland following a fire in 1992. We compared four areas of differing fire history: (1) an area burned in 1992, (2) an area burned in 1992 and 1988, (3) an area burned in 1988 and (4) an area with no recent fire history. The year after burning, graminoids produced more aboveground biomass on burned areas compared with unburned areas. Forages growing on burned soils were highly concentrated with all nutrients, except Ca, when elk grazed the site. Despite nutrient-rich forage on burned areas, elk consumed little forage in these areas. We hypothesized that elk ate less than expected in burned areas because of a large bloom of lupine (Lupinus sericeus), which may be unpalatable to elk.