Rocky Mountain Coniferous Forests Research Articles

Changes in mass, carbon, nitrogen, and phosphorus in logs decomposing for 30 years in three Rocky Mountain coniferous forests

Estimates of decomposition rates of coarse woody debris (CWD) and fluxes of nutrients therein are essential components of carbon (C) and nutrient budget models. In a 30-year field experiment, we periodically measured mass remaining and nutrient concentrations in log segments of pine, spruce, and fir in natural, mature coniferous forests in Alberta, Canada. The predicted turnover times (t95; years) were 43–44 years for pine, 42–60 years for spruce, and 38–46 years for fir. Extrapolating from best-fit models, we predict that decomposition of these logs would be complete within 50–60 years. The ratio of carbon to nitrogen (C:N) declined for most of the decomposition period, and ratios of the three species converged at <200 at 90% mass loss. Net release of N occurred only after logs had lost 90% of their original C and C:N had declined to <200. The ratio of carbon to phosphorus (C:P) declined and converged at 500–1000 at 90% mass loss. There was no evidence of net P release from logs even at 90% mass loss. It may be possible to estimate the amounts of N and P that will be incorporated into decaying logs based on the extent to which their initial C:N differs from 200 and their initial C:P differs from 500.

Mass loss and nutrient dynamics of coarse woody debris in three Rocky Mountain coniferous forests: 21 year results

Mass loss and changes in C, N, and P concentrations were measured in 20 cm long log segments of lodgepole pine ( Pinus contorta Dougl. ex Loud.), white spruce ( Picea glauca (Moench) Voss), and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) that had been placed in three Rocky Mountain coniferous forests 21 years earlier. Pine, spruce, and fir lost 76%, 39%, and 64%, respectively, of their initial mass during the 21 years. The corresponding mean decay rates (k) were 0.072, 0.024 and 0.052·year–1. The decay patterns of pine and spruce were similar with the highest k between 6 and 14 years. Fir k increased during the course of decomposition with the highest rate between 14 and 21 years. The correlation between original dry mass and k was negative for pine (r = –0.28), positive for fir (r = 0.35), and not significant for spruce. C/N, C/P, and N/P ratios declined and converged to a similar value in relation to mass loss for all three species. The N/P ratios of logs of all three species stabilized at about 19. These findings indicate that patterns of wood decay are difficult to predict (even with 14 year data), and so models that incorporate wood-decay estimates will be associated with considerable uncertainty.

Erratum: The contribution of coarse woody debris to carbon, nitrogen, and phosphorus cycles in three Rocky Mountain coniferous forests

Erratum: The contribution of coarse woody debris to carbon, nitrogen, and phosphorus cycles in three Rocky Mountain coniferous forests

Understory plant species composition 30–50 years after clearcutting in southeastern Wyoming coniferous forests

To evaluate the long-term effects of clearcutting and slash treatment on understory plant species composition in Rocky Mountain coniferous forests, we collected comparable data from 30- to 50-year-old post-harvest stands and adjacent mature (>100-year-old) stands that originated after wildfire. In general, plant species richness was higher in the post-harvest stands than in adjacent mature stands, due in large part to the presence of species that benefit from disturbance. Species composition in post-harvest and mature stands was more similar in montane forests (2710–2805 m elevation) than in subalpine forests (2800–3164 m elevation), suggesting greater resilience of montane understories. Composition in post-harvest and mature stands was least similar when slash was piled and burned, and most similar when slash was lopped and scattered. Eighty-seven percent of the post-harvest stands had at least one exotic species, but total cover of exotic plant species in all post-harvest stands was ≤1%. Exotic species were largely absent from mature forests. Our results suggest that understory species of low-elevation montane forests recover more quickly from disturbance than do those of subalpine forests, with slash treatment and species life history traits strongly influencing this recovery.

Historic range of variability in landscape structure in subalpine forests of the Greater Yellowstone Area, USA

A measure of the historic range of variability (HRV) in landscape structure is essential for evaluating current landscape patterns of Rocky Mountain coniferous forests that have been subjected to intensive timber harvest. We used a geographic information system (GIS) and FRAGSTATS to calculate key landscape metrics on two ∼130,000-ha landscapes in the Greater Yellowstone Area, USA: one in Yellowstone National Park (YNP), which has been primarily shaped by natural fires, and a second in the adjacent Targhee National Forest (TNF), which has undergone intensive clearcutting for nearly 30 years. Digital maps of the current and historical landscape in YNP were developed from earlier stand age maps developed by Romme and Despain. Maps of the TNF landscape were adapted from United States Forest Service Resource Information System (RIS) data. Key landscape metrics were calculated at 20-yr intervals for YNP for the period from 1705-1995. These metrics were used to first evaluate the relative effects of small vs. large fire events on landscape structure and were then compared to similar metrics calculated for both pre- and post-harvest landscapes of the TNF. Large fires, such as those that burned in 1988, produced a structurally different landscape than did previous, smaller fires (1705-1985). The total number of patches of all types was higher after 1988 (694 vs. 340-404 before 1988), and mean patch size was reduced by almost half (186 ha vs. 319-379 ha). The amount of unburned forest was less following the 1988 fires (63% vs. 72-90% prior to 1988), yet the number of unburned patches increased by nearly an order of magnitude (230 vs. a maximum of 41 prior to 1988). Total core area and mean core area per patch decreased after 1988 relative to smaller fires (∼73,700 ha vs. 87,000-110,000 ha, and 320 ha vs. 2,123 ha, respectively). Notably, only edge density was similar (17 m ha−1 after 1988) to earlier landscapes (9.8-14.2 m ha−1).Three decades of timber harvesting dramatically altered landscape structure in the TNF. Total number of patches increased threefold (1,481 after harvest vs. 437 before harvest), and mean patch size decreased by ∼70% (91.3 ha vs. 309 ha). None of the post-harvest landscape metrics calculated for the TNF fell within the HRV as defined in YNP, even when the post-1988 landscape was considered. In contrast, pre-harvest TNF landscape metrics were all within, or very nearly within, the HRV for YNP. While reference conditions such as those identified by this study are useful for local and regional landscape evaluation and planning, additional research is necessary to understand the consequences of changes in landscape structure for population, community, ecosystem, and landscape function.

The contribution of coarse woody debris to carbon, nitrogen, and phosphorus cycles in three Rocky Mountain coniferous forests

The contribution of coarse woody debris to C, N, and P cycles was assessed in forests of lodgepole pine (Pinus contorta Dougl. ex Loud.), white spruce (Picea glauca (Moench Voss), and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) - Engelmann spruce (Picea engelmannii Parry ex Engelm.) in southwestern Alberta. Mass loss and changes in C, N, and P concentrations in decomposing log segments were measured for 14 years. Litter input was measured during 10 years for coarse woody debris, 1 year for ground vegetation, and 5 years for other aboveground litter types. Release of C, N and P from decomposing litter were simulated for a period of 40 years. After 14 years, log segments of pine, spruce, and fir had lost on average 71, 38, and 40%, respectively, of their dry mass. The N content of the pine logs increased, spruce changed little, and fir lost N. Phosphorus accumulated in all logs. The greatest imports of N and P occurred at the pine sites and fir sites, respectively, where these nutrients were the least available, indicating that wood decay organisms may compete with vegetation for limiting nutrients in these forests. Coarse woody debris comprised 3-24% of aboveground litter and contributed less than 5% of the N and P released. Coarse woody debris does not appear to make a significant contribution to N and P cycling in these forests.

The contribution of coarse woody debris to carbon, nitrogen, and phosphorus cycles in three Rocky Mountain coniferous forests

The contribution of coarse woody debris to carbon, nitrogen, and phosphorus cycles in three Rocky Mountain coniferous forests

Carbon to Organic Matter Ratios for Soils in Rocky Mountain Coniferous Forests

AbstractVegetation type, soils, climate, and conversion ratios influence estimates of terrestrial C. Our objectives were to (i) determine carbon to organic matter (C/OM) ratios for brown cubical rotten wood, litter, surface humus, soil wood, and mineral soils; (ii) evaluate the validity of using 0.58 and 0.50 ratios for estimating C in mineral and organic soil components, respectively; and (iii) determine if C/OM relationships were applicable across broad geographic areas. The study sites were located from the southern to northern Rocky Mountains. They differed in vegetation, soil parent material, and climate. The C/OM regression slopes we developed for organic components were quite consistent and relatively constant across vegetation types ranging from 0.43 to 0.51 and were similar to the 0.50 traditional ratio. The C/OM regression slopes for mineral soils ranged from 0.16 to 0.48 depending on vegetation type. These slopes were lower than the 0.58 ratio often applied. The reliability of simple ratios when used in estimating C as a function of organic matter is often overestimated. Error and bias can be introduced into C estimates when using simple ratios. This study refined C/OM regressions for mineral soils and provided regressions for organic soil components. Information developed in this study can be applied to improve regional and global C assessments.

Simulating effects of fire on northern Rocky Mountain landscapes with the ecological process model FIRE-BGC.

A mechanistic, biogeochemical succession model, FIRE-BGC, was used to investigate the role of fire on long-term landscape dynamics in northern Rocky Mountain coniferous forests of Glacier National Park, Montana, USA. FIRE-BGC is an individual-tree model-created by merging the gap-phase process-based model FIRESUM with the mechanistic ecosystem biogeochemical model FOREST-BGC-that has mixed spatial and temporal resolution in its simulation architecture. Ecological processes that act at a landscape level, such as fire and seed dispersal, are simulated annually from stand and topographic information. Stand-level processes, such as tree establishment, growth and mortality, organic matter accumulation and decomposition, and undergrowth plant dynamics are simulated both daily and annually. Tree growth is mechanistically modeled based on the ecosystem process approach of FOREST-BGC where carbon is fixed daily by forest canopy photosynthesis at the stand level. Carbon allocated to the tree stem at the end of the year generates the corresponding diameter and height growth. The model also explicitly simulates fire behavior and effects on landscape characteristics. We simulated the effects of fire on ecosystem characteristics of net primary productivity, evapotranspiration, standing crop biomass, nitrogen cycling and leaf area index over 200 years for the 50,000-ha McDonald Drainage in Glacier National Park. Results show increases in net primary productivity and available nitrogen when fires are included in the simulation. Standing crop biomass and evapotranspiration decrease under a fire regime. Shade-intolerant species dominate the landscape when fires are excluded. Model tree increment predictions compared well with field data.

Biomass of Coarse Woody Debris Following Disturbance in Rocky Mountain Coniferous Forests

Primary productivity, the accumulation of nutrients, and other important ecosystem processes are largely dependent on the mineral soil organic matter that has developed during hundreds or thousands of years. In forest ecosystems, the decomposition of coarse woody debris, woody roots, twigs, leaves and micro-organisms is a primary source of this organic matter. Large quantities of coarse woody debris are typically produced following natural disturbances such as fires, pest/pathogen outbreaks, and windstorms, and make a significant contribution to the formation of soil organic matter (SOM). In contrast, timber harvesting often removes most of the coarse woody debris (CWD), which could result in a decrease in the quantity and a change in the quality of mineral soil organic matter. The 1988 fires in Yellowstone National Park continue to provide an excellent opportunity to study the effects of fires of various intensities on ecosystem processes. Ecosystems develop under conditions that are constantly changing, but which remain within some range of natural variability. At present, national forest managers are uncertain as to the quantity of CWD which should be left in a stand following timber harvest in order to maintain levels of SOM which are within the range of natural variability. Little empirical data exist which help characterize the range of natural variability with regard to CWD in lodgepole pine forests, and it is therefore difficult to assess current timber harvesting practices in terms of how much CWD should be left at each site. We began a pilot study in late summer 1995 to begin to address this deficiency. A larger study of broader scope is planned for an additional two to three years, beginning this year, in 1996. This research will attempt to measure specific processes which include the distribution, decomposition, combustion by natural fires, and removal of CWD. The specific objectives of our study are: i) compare the mass and distribution of coarse woody debris that remains following fires of varying intensities to that which remains following clearcutting in the Rocky Mountain Region; ii) estimate the amount of CWD that is combusted or converted to charcoal following fires of varying intensities in stands of varying stages of development; and iii) estimate the length of time necessary for every square meter of the forest soil to be affected by CWD under natural conditions.

The Effects of Fire on Coarse Woody Debris in Rocky Mountain Coniferous Forests

Primary productivity, the accumulation of nutrients, and other important ecosystem processes are largely dependent on the mineral soil organic matter that has developed during hundreds or thousands of years. In forest ecosystems, the decomposition of coarse woody debris, woody roots, twigs, leaves and micro-organisms is a primary source of this organic matter. Large quantities of coarse woody debris are typically produced following natural disturbances such as fires, pest/pathogen outbreaks, and windstorms, which make a significant contribution to the formation of soil organic matter (SOM). In contrast, timber harvesting often removes most of the coarse woody debris (CWD), which could result in a decrease in the quantity and a change in the quality of mineral soil organic matter.

Root Gap Dynamics in Lodgepole Pine Forest: Nitrogen Transformations in Gaps of Different Size

Belowground responses to aboveground disturbance were studied in experimental gaps created in a 95—yr—old stand of Pinus contorta in southeastern Wyoming. One—, 5—, 15—, and 30—tree clusters were felled to create a series of gaps in the root mat, and solution—phase N was monitored over two consecutive snow—melt periods via tension—tube water collectors. We hypothesized that dissolved and extractable nitrogen concentrations would not exceed predisturbance levels until a threshold canopy gap size had been achieved. As predicted, NOx—N attained significantly higher solution N concentrations (2—5 mg/L) only with the death of 15 trees or more. However, dissolved organic nitrogen decreased gradually with increasing gap size. Net mineralization and nitrification were studied using 30—d in situ incubation assays in each gap. Extractable nitrate routinely was negligible until the 30—tree gaps had been attained. Predicting the effects of disturbance on nutrient cycling, including timber—harvesting practices, requires information on belowground responses to gap formation. Our experiments suggest that gap size is important; removal of 15—30 tree clusters represented a threshold above which significant losses of available N to the groundwater may be incurred, at least in Rocky Mountain coniferous forests.

Nutrient release from decomposing litter in Rocky Mountain coniferous forests: influence of nutrient availability

We examined patterns of N and P uptake and release from a wide variety of litter types, including leaves, needles, moss, roots, and wood, for 4 years in three forests (lodgepole pine (Pinuscontorta Loud.), white spruce (Piceaglauca (Moench) Voss)–lodgepole pine, and Engelmann spruce (Piceaengelmannii Parry ex Engelm.)–subalpine fir (Abieslasiocarpa (Hook.) Nutt.)) and a small clearcut, in the Rocky Mountains of Alberta. Decomposition was more rapid and N release began sooner in the clearcut than in the forests, but N release began at the same stage of decomposition at all sites. In most litter types, a period of net immobilization of N was followed by a period of net release; only litter types particularly rich in N had an initial leaching phase. Each litter type initially gained or lost N depending on its original concentration, such that N contents converged after 1 or 2 years. The N content at convergence differed among litter types. Phosphorus was usually released immediately. The rate of P loss also varied according to the initial P concentration, and the P contents of all litter types converged within 1 year. The availability of N and P in the forest floor did not affect the rate of N and P release from a standard substrate placed at all sites. The concentrations of N and P in the litter influenced the rate of uptake of N or P during the first 1–3 years, but was not consistently related to nutrient availability in the forest floors at the four sites.

Immobilization and availability of N and P in the forest floors of fertilized Rocky Mountain coniferous forests

The rates of key processes related to the recycling of nutrients in the forest floor were monitored for four years following the application of ammonium phosphate sulphate to small plots in mature stands of lodgepole pine, white spruce, and Engelmann spruce-subalpine fir, and a small clearcut. Net mineralization of nitrogen and phosphorus were initially enhanced by fertilization, but microbial activity and biomass were unchanged. Nitrification was increased on fertilized plots on the clearcut immediately after fertilizer application, and in the mature forests the following year. No changes were detected in the mass or quality of the overstorey litter, but significantly larger amounts of N and P were returned in understorey litter. Decomposition and nutrient release from Epilobium angustifolium leaves were more rapid in leaves either harvested from, or decomposed on, fertilized plots. Four years after application, mineralizable N in the forest floor was higher on fertilized plots at the most N-rich sites only, highlighting the importance of the nutrient immobilization capacity of the site in determining the duration of enhanced nutrient availability following fertilization.

Availability of nitrogen and phosphorus in the forest floors of Rocky Mountain coniferous forests

Nutrient supply rate and limitation were measured in forest floors of lodgepole pine, white spruce–lodgepole pine, and Engelmann spruce–subalpine fir (pine, spruce, and fir forests, respectively) forests in the Kananaskis Valley of southwestern Alberta. Earlier analyses of the nutrient content of foliage and litter indicated low N and P supply in the pine forest, high P supply in the spruce forest, and high N–low P supply in the fir forest. Measurements of nutrient supply (insitu rates of net mineralization, extractable P, and uptake of N and P from the forest floor in pot trials) confirmed the differences in N and P supply among the forests and indicated that nutrient concentrations in needle litter were useful as an index of nutrient supply rate. Subtractive tests were useful in identifying the most limiting nutrients in each forest: lodgepole pine seedlings grown in forest floor material from the pine and spruce stands responded with increased growth to the addition of N; those in fir forest floor material responded to P addition. Vector analysis of N and P concentrations and contents in needles from trees fertilized with ammonium phosphate sulphate showed responses to both N and P in the pine site, no response at the spruce site, and response to P at the fir site.

Substrate control of litter decomposition in four Rocky Mountain coniferous forests

The influence of chemical and physical quality of litter on its rate of decomposition was examined by measuring mass loss from 19 diverse litter types, including leaves, needles, forbs, wood, and roots in the Kananaskis Valley of Alberta, Canada. Litter samples drawn from three adjacent forests of lodgepole pine, white spruce, and Engelmann spruce – subalpine fir, and from a small clearcut area, were allowed to decompose for 3 years at their sites of origin. The best predictors of mass loss were the initial concentrations of lignin and labile material in the litter. Adding N or P contents as a second term, rather than as a lignin to nutrient ratio, significantly improved mass loss predictions. There were abrupt limits for the influence of lignin (above 28%) and N (below C:N of 30:1); similar limits were observed for all predictors except labile content. None of these chemical parameters, nor a physical measure, particle diameter, were useful in predicting rates of decomposition of high-lignin, woody substrates. The relative importance of the various litter quality parameters in determining rates of mass loss in the clear-cut area was very similar to that in the forests, despite considerably more rapid decomposition in the clearcut. Key words: decomposition, lignin, litter, nutrients, Rocky Mountains, wood.

Input, accumulation, and residence times of carbon, nitrogen, and phosphorus in four Rocky Mountain coniferous forests

Annual aboveground litterfall in forests of Pinuscontorta Loud., Piceaglauca (Moench) Voss, Piceaengelmannii Parry ex Engelm., and Abieslasiocarpa (Hook.) Nutt. in southwestern Alberta ranged from 286 to 321 g•m−2•year−1. The mass of litter accumulated on the forest floors ranged from 6.3 to 11.0 kg•m−2. Residence times of organic matter in the forest floor were 11 years in a 90-year-old P. contorta stand, 16 years in a 120-year-old P. glauca–P. contorta stand, and 23 years in a 350-year-old P. engelmannii–A. lasiocarpa stand. Residence times of litter in the L layer of the forest floor were longer in a recently clearcut area than in the older forests. Residence times of individual nutrients in the forest floors were in the order N > P > C. Litter in the pine forest had lower concentrations of both N and P than did litter in the spruce–pine forest; litter in the spruce–fir forest had relatively high N and low P concentrations. Differences in nutrient concentrations of litter among sites reflected differences in the nutrient-use efficiency of the vegetation, suggesting that the species composition of vegetation is important in determining availability of nutrients in the floor of these forests.

Biomass, productivity, and nutrient-use efficiency of aboveground vegetation in four Rocky Mountain coniferous forests

Aboveground biomass, annual production, and internal nitrogen and phosphorus dynamics of vegetation were compared among a 90-year-old Pinuscontorta Loudon forest, a 120-year-old Piceaglauca (Moench) Voss–P. contorta forest, a 350-year-old Piceaengelmannii Parry ex Engelm.–Abieslasiocarpa (Hook.) Nutt. forest, and a 13-year-old P. contorta stand in the Rocky Mountains of southwestern Alberta. Aboveground biomass of vegetation ranged from 109 to 203 t•ha−1, while aboveground net primary productivity ranged from 4.4 to 5.3 t•ha−1•year−1 in the mature forests. Approximately 30% of the N and 20–40% of the P in ground vegetation were reabsorbed during senescence; 40–50% of the N and 50–80% of the P were reabsorbed from senescing tree foliage. Annual uptake of nutrients (production minus reabsorption) was between 1.8 and 2.2 g•m−2•year−1 for N and 0.2–0.4 g•m−2•year−1 for P. Efficiency of nutrient use (milligrams of new biomass produced per milligram of nutrient taken up in 1 year) ranged from 249 to 262 for N and 1604 to 2355 for P in the mature forests, and 72 and 642, respectively, in the young pine stand. Both N and P were used very efficiently in the pine forest and relatively inefficiently in the spruce–pine forest, reflecting differences in the inherent nutrient-use efficiency of these tree species. In the spruce–fir forest, N was used less efficiently and P more efficiently than in other forests, in response to lower phosphorus availability in this forest. Differences in nutrient-use efficiency of vegetation were related to differences in the amount of biomass produced per unit amount of N or P taken up, and not to differences in efficiency of N or P reabsorption.

Epiphytic Lichens of a Ponderosa Pine Forest in Southeastern Montana

Nineteen lichen species were collected from Pinus ponderosa Dougl. in Custer National Forest in southeastern Montana; 340 trees in four vegetation types were sampled. The dominant lichen species at all heights of the trunks and on lower branches was Usnea hirta (L.) Wigg., constituting 31-74% of total lichen cover. The percentage of U. hirta was highest in the driest vegetation type (P. ponderosa-Agropyron spicatum) and lowest in the most moist vegetation type (P. ponderosa-Prunus virginiana). The majority of lichen cover and diversity on tree trunks was on the lowest 50 cm; diversity and cover increased with ascending moisture levels. Parmeliopsis ambigua (Wulf.) Nyl., Bryoria fuscescens (Gyeln.) Brodo & D. Hawksw., and Cetraria pinastri (Scop.) S. Gray increased most sub- stantially from drier to wetter sites. Most of the lichen species found in this forest type are regular components of Rocky Mountain and/or northern coniferous forests. Other conifer forest types in the Rocky Mountains and Black Hills support richer lichen floras. Because epiphytic lichens are largely dependent on atmospheric sources of water and nutrients for their survival, the study of the composition of lichen communities may fre- quently be used to document changes in atmospheric conditions (Barkman 1969). In this capacity, lichen studies have frequently been useful in documenting air quality as reflected by variation in air pollutant levels (Hawksworth 1971; Nash 1976). The high plains of Wyoming and eastern Montana contain extensive coal fields that are currently and in the upcoming decades will be a major energy source for the United States. The potential for air quality degradation due to emissions from coal-fired power-generating plants is con- siderable, and consequently knowledge of the region's lichen flora is of interest. Although much of the region is dominated by short-grass prairies, both scattered-open and extensive- dense stands of ponderosa pine (Pinus ponderosa Dougl.) do occur in the region. To the best of my knowledge, the current study is the first report on quantitative variation in epiphytic lichens of the region. The epiphytic lichen flora of most of Montana is relatively poorly known. The majority of collections have been from the diverse and extensive conifer forests of the northwest portion of the state (Habeck 1963; McCune 1979). Imshaug (1950) collected alpine lichens in Glacier National Park and one western county. A preliminary distributional study of epiphytic lichens compared presence of those species in various areas of Montana (Ev- ersman 1979). The epiphytic lichens of Pinus ponderosa, the only conifer species in southeastern Montana forests, have not been studied. Gough (1975) described the epiphytic communities of Pseudotsuga menziesii (Mirbel) France and Abies lasiocarpa (Hook.) Nutt. in Colorado, 1100 km to the south of this study area. Wetmore (1967) made a floristic study of the Black Hills, 160 km to the east, where the primary coniferous species are P. ponderosa on 007-2745/82/204-213$1.15/0

An Analysis of Forest Fire History on the Little Firehole River Watershed, Yellowstone National Park

Fire is now recognized as a major process in Rocky Mountain coniferous forests, with many ecosystem patterns and processes being affected as much by fire as by climate and soil. For this reason there is a move toward reinstating fire as a natural process within our National Parks and Wilderness Areas, a move which is proceeding cautiously, however, because there is still much that we do not know about fire's natural role in ecosystems. In Yellowstone National Park, where a fire management plan is now in effect, an important question is: What is the natural frequency and size of wildfires in different Park ecosystems? An understanding of natural fire frequency and size is important not only in formulating and evaluating fire management plans, but also in evaluating long-term effects of fire on wildlife habitat, productivity, nutrient cycling, and other ecosystem processes.