Post-burn Year Research Articles

Golden Eagle dietary shifts following wildfire and shrub loss have negative consequences for nestling survivorship

Abstract Wildfires and invasive species have caused widespread changes in western North America’s shrub-steppe landscapes. The bottom–up consequences of degraded shrublands on predator ecology and demography remain poorly understood. We used a before–after paired design to study whether Golden Eagle (Aquila chrysaetos) diet and nestling survivorship changed following wildfires in southwestern Idaho, USA. We assessed burn extents from 1981 to 2013 and vegetation changes between 1979 (pre-burn) and 2014 (post-burn) within 3 km of Golden Eagle nesting centroids. We measured the frequency and biomass of individual prey, calculated diet diversity indexes, and monitored nestling survivorship at 15 territories in 1971–1981 and 2014–2015. On average, 0.70 of the area within 3 km of nesting centroids burned between 1981 and 2013, and the mean proportion of unburned shrubland decreased from 0.73 in 1979 to 0.22 in 2014. Diets in post-burn years were more diverse and had a lower proportion of some shrub-associated species, such as black-tailed jackrabbits (Lepus californicus) and mountain cottontails (Sylvilagus nuttallii), and a higher proportion of American Coots (Fulica americana), Mallards (Anas platyrhynchos), Piute ground squirrels (Urocitellus mollis), and Rock Pigeons (Columba livia) compared with pre-burn years. A high proportion of waterfowl represented a novel change in Golden Eagle diets, which are typically dominated by mammalian prey. Nestling survivorship was positively associated with the proportion of black-tailed jackrabbits and negatively associated with the proportion of Rock Pigeons in eagle diets. Rock Pigeons are a vector for Trichomonas gallinae, a disease-causing protozoan lethal to young eagles. Nesting attempts were more likely to fail (all young die) in the post-burn period compared with the pre-burn period. Dietary shifts are a common mechanism for predators to cope with landscape change, but shifts away from preferred prey to disease vectors affect nestling survivorship and could lead to population-level effects on productivity.

Indications and Predictors for Reconstructive Surgery After Hand Burns

The objective of this study was to analyze the prevalence, indications, and type of reconstructive surgery and predictors of the outcomes of reconstructive surgery after hand burns. A retrospective cohort study was conducted that included all patients admitted with acute hand burns in the Dutch burn centers from January 1998 through December 2002. The details of reconstruction including frequency, timing, indication, and techniques were collected over a 10-year follow-up period. Hand burns were seen in 42% (n= 562 of 1,334) of all patients admitted with acute burns. Reconstructive surgery during the 10-year follow-up period was required in 15%. Contractures, especially of the first web space and little finger, were the most frequent indications for reconstructive surgery. Web spaces 1 to 3 and the little finger were the location most frequently operated on. The most frequently performed surgical technique was release of the contractures and the use of a random flap. Eighty percent of the reconstructive surgery patients required more than 1 reconstructive procedure, most often within 2 years of the initial injury. Secondary operations at the same location were required in 12%. In 40% of the patients, the first reconstructive surgery was performed within the first postburn year. Significant independent factors related to the need for reconstructive hand surgery were a larger area of full-thickness burns and surgical treatment of the hand during the acute phase. Reconstructive surgery was required in 15% of patients who sustained hand burns. The majority of the patients requiring reconstructive surgery of the hand needed 2 or more operations to correct the contractures of the hand. Contractures of the little finger and first web space were the locations most frequently operated on. Patients with more extensive burns and who required hand surgery during the acute phase were more likely to need reconstructive surgery. Prognostic IV.

Is fire exclusion in mountain big sagebrush communities prudent? Soil nutrient, plant diversity and arthropod response to burning

Fire has largely been excluded from many mountain big sagebrush communities. Managers are reluctant to reintroduce fire, especially in communities without significant conifer encroachment, because of the decline in sagebrush-associated wildlife. Given this management direction, a better understanding of fire exclusion and burning effects is needed. We compared burned to unburned plots at six sites in Oregon. Soil nutrient availability generally increased with burning. Plant diversity increased with burning in the first post-burn year, but decreased by the third post-burn year. Burning altered the arthropod community, which included doubling the density of arthropods in the first post-burn year. Some arthropod Orders increased and others decreased with burning. For example, Araneae were 1.7- and 1.8-fold less and Hemiptera were 6.6- and 2.1-fold greater in the burn compared with the control in 2008 and 2009. Our results provide evidence that burning can create spatial and temporal heterogeneity in sagebrush communities and thus, it is an important component of the ecosystem. We suggest that management plans for many mountain big sagebrush communities may need to include infrequent burning. At the very least managers should be aware that fire exclusion has some potentially negative effects other than the encroachment of conifers in these communities.

Effects of short-rotation controlled burning on amphibians and reptiles in pine woodlands

Fire is being used increasingly as a forest management tool throughout North America, but its effects on reptiles and amphibians in many ecosystems are unclear. Open woodlands with understories dominated by herbaceous vegetation benefit many wildlife species, but maintaining these woodlands requires frequent burning. Although many studies have compared herpetofaunal responses in burned forests to unburned forests, fewer studies have examined changes in the herpetofaunal community during the interval between short-rotation prescribed burns. We examined changes in habitat and relative abundance of reptiles and amphibians each year within a 3-year burn cycle in nine restored pine woodlands of western Arkansas, USA. Overall numbers of reptiles did not change among the three burn years; however, capture rates for one snake species (southern black racer [Coluber constrictor priapus]) and three lizards differed among the three post-burn years. Overall capture rate for anurans and all amphibians combined was greatest the first year after burning, mostly because captures of dwarf American toads (Bufo americanus charlessmithi) were substantially greater in stands the first year after burning. Salamander captures were infrequent. Capture rates of most reptile and amphibian species declined over the 3-year sampling period. Only minor changes in capture rate occurred among the 36 species we evaluated during the intervening years between frequent burns. Capture rates for only two species were lower the first year after fire. Although not all herpetofaunal species benefited from frequent fire, most species appeared to tolerate the frequent burning necessary for maintaining open pine woodlands in the Ouachita Mountains.

Prescribed burning effects on the hydrologic behavior of gullies in the South Carolina Piedmont

Gullies found in the Piedmont of South Carolina are legacies of past land use and erosion. Although the majority of these gullies are now under forest vegetation and perceived as geomorphologically stable, the question of gully contribution to nonpoint source pollution remains undetermined, especially when these gullies are subjected to prescribed burning or other forest disturbance. Six prescribed burned and two reference gullies draining mature pine stands grown on former cotton fields were instrumented at the Long Cane Ranger District, Sumter National Forest, South Carolina to characterize the hydrologic behavior of these gullies and to investigate response to prescribed burning. Flow in the gullies was observed for one year of pre-burn and one year of post-burn conditions. Hydrologic behavior of these eight gullies varied greatly in the pre-treatment period. During the study, 48 rainfall events exceeding 12.7 mm were recorded, but one reference gully never produced flow and three treatment gullies flowed during three events or less and only in the pre-burn period. Although significant storm events occurred throughout the year, all gully flow events occurred between December and March. Double-mass and graphical analysis of relative stormflow production of the reference and treatment gullies in the pre- and post-treatment periods did not indicate an effect of the controlled burn on flow behavior, but the post-burn year was characterized by drought. The observed inter-annual variation in gully behavior was large. Observations of local groundwater conditions with piezometers and electrical resistivity surveys indicated that gully flows were controlled by the presence of a flow-restricting layer below the gully bed.

Home-Range Size and Site Tenacity of Overwintering Le Conte's Sparrows in a Fire Managed Prairie

We evaluated home-range size and site tenacity of Le Conte's Sparrows (Ammodramus lecontii) during winter 2002–2003 at Brazoria National Wildlife Refuge, Texas. Twenty-six wintering Le Conte's Sparrows were radiomarked in 1- and 2-year post-burn units, and monitored for ∼10 days. Additionally, 1-ha plots on each 1-, 2- and 3-year (n = 15) post-burn units were flush-netted once monthly. Telemetry results indicated Le Conte's Sparrows were sedentary during winter with a 50% probability mean home-range of 2.41 ha (72% < 1 ha) and a 95% probability mean home range of 10.31 ha (44% < 1 ha and 55% < 1.5 ha). Home-range size did not differ between post-burn year 1 and 2 (P = 0.227). Le Conte's Sparrows appeared to exhibit a behavioral response to flush-netting (P < 0.001) with estimated capture probability of 0.462 and recapture probability of 0.056. Our findings suggest Le Conte's Sparrows remain fairly sedentary throughout the winter.

The Response of Thurber’s Needlegrass to Fall Prescribed Burning

Thurber’s needlegrass (Achnatherum thurberianum [Piper] Barkworth) is an important component of many sagebrush communities in the Intermountain West. Prescribed fall burning is often implemented in sagebrush plant communities to mimic historic wildfires, improve wildlife habitat, and increase livestock forage production. Burning is used because it shifts dominance from sagebrush to herbaceous vegetation. The effects of prescribed fall burning on Thurber’s needlegrass are largely unexplored. The purpose of this study was to determine the response of Thurber’s needlegrass to prescribed fall burning. A randomized block design was used, and each block consisted of a fall burned and unburned (control) Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis [Beetle & A. Young] S. L. Welsh)–bunchgrass communities. Response variables measured in the first and second years after burns were Thurber’s needlegrass community foliar cover and density, vegetative and reproductive biomass, photosynthetic rates, tissue carbon (C) and nitrogen (N) content, and N ( 15 N: 14 N) and C ( 13 C: 12 C) isotope ratios. Density of Thurber’s needlegrass in both postburn years and cover in the second postburn year were not different between treatments (P . 0.05), but cover was less in the burned than control treatment in the first postburn year (P 5 0.008). Carbon isotope ratios in Thurber’s needlegrass differed between the burn (225.9 6 0.1 SE) and control (226.3 6 0.1 SE) treatments in the first postburn year (P 5 0.019). Nitrogen isotope ratios indicated nitrogen was more available in the burned than control treatment in both years (P , 0.05). Photosynthetic rates of Thurber’s needlegrass were also generally greater in the burned than control treatment (P 5 0.045). Our results suggest burning altered the availability of resources to Thurber’s needlegrass plants. Our results also suggest that prescribed fall burning is not detrimental to Thurber’s needlegrass and, thus, can be used as a method to shift dominance from sagebrush to herbaceous vegetation.

Soil C and N Pools in Chinese Fir and Evergreen Broadleaf Forests and their Changes with Slash Burning in Mid-Subtropical China

Soil organic carbon (C) and total nitrogen (N) pools of a Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) (CF) forest, and an evergreen broadleaf (EB) forest located in mid-subtropical, southeastern China, were compared before clearcutting, with the effect of slash burning on organic C and total N in the top 10 cm of soil before and after burning also being evaluated. Prior to clearcutting CF forest had significantly lower (P < 0.05) organic C and total N in the soil (0–100 cm) compared to EB forest with approximately 60% of the C and N at the two forest sites stored at the 0 to 40 cm soil. In post-burn samples of the 0–10 cm depth at 5 days, 1 year, and 5 years for CF and EB forests, significantly lower levels (P < 0.05) of organic C and total N than those in the pre-burn samples were observed. Compared to the pre-burn levels, at post-burn year 5, surface soil organic C storage was only 85% in CF forest and 72% in EB forest, while total N storage was 77% for CF forest and 73% for EB forest. Slash burning caused marked long-term changes in surface soil C and N in the two forest types.

The effect of pasture improvement and burning on Orthoptera populations of Culm grasslands in northwest Devon, UK

Very little research has been conducted into the impact of grassland management on insect populations of Culm grasslands located in northwest Devon, UK. This paper presents the effects of agricultural improvement and burning on Orthoptera populations of these wet, heathy pastures at Dunsdon National Nature Reserve. The results from this 2-year study should aid conservation management of this important UK habitat. Orthoptera populations and habitat variables of improved (drained and cropped from 1840-1875) and unimproved pastures, were monitored in 2002 and 2003. There was no significant difference in Orthoptera abundance between pasture cropped from 1840-1875 and unimproved grassland, suggesting that mobile grasshopper species such as the meadow grasshopper Chorthippus parallelus, recolonised the improved swards from surrounding pastures, after a lengthy period of arable cropping in the 1800s. Winter burning led to higher numbers of Orthoptera in the post-burn year, perhaps due to the reduced sward height and biomass on the burnt swards, making them more favorable for postdiapause development.

Response Of A Terrestrial Mollusc Community To An Autumn Prescribed Burn In A Rare Wetland Prairie Of Western Oregon, USA

Conservation and management of grasslands may involve the use of prescribed fire to reinstate a historical disturbance regime recently suppressed by humans. I used traps to describe the terrestrial mollusc community in a rare wetland prairie ecosystem of western Oregon, USA over a 3-year period in an adjacent burned and unburned wetland prairie parcel beginning 1 year following an autumn prescribed fire. Species richness was lower throughout the burned area for the duration of the study period and mollusc abundance was lower in the first postburn year, but steadily increased over time, surpassing the adjacent burned area by the third postburn year. According to Multi-response Permutation Procedure, the mollusc community in the adjacent burned area differed significantly from the unburned prairie each year since the burn, suggesting that fire history may structure the wetland prairie mollusc community. Indicator species analysis identified that Deroceras reticulatum and Monadenia fidelis were indicator species for unburned wetland prairie, while Catinella rhederi and Vertigo modesta were indicator species for burned habitat at the study site. Since fire appears to decrease wetland prairie mollusc diversity and abundance, prescribed burns should be conducted in accordance with refuges, to provide a source population for colonizing molluscs and for other animals with unknown responses to fire.

Prescribed fire affects white oak seedling phytochemistry: implications for insect herbivory

Fire suppresses vegetative competition, increases light penetration and soil nutrients, and is an integral part of the disturbance regime forming the oak ( Quercus)-dominated forests of eastern North America. Fire can affect plant foliar chemistry through changes in nutrient availability and light intensity, which can influence herbivore feeding patterns. We considered the interactions between fire and oak seedling herbivory by assessing the effects of prescribed fire on white oak ( Quercus alba L.) foliar chemistry. We hypothesized that fire would provide increased light penetration and added nutrients that would enhance the nutritional status of foliage, thereby leading to greater herbivore pressure. We compared white oak foliar chemistry and root characteristics of seedlings from once-burned (1998), twice-burned (1996 and 1998), and non-burned sites over 2 years. We also challenged seedlings with supplemental herbivory and measured foliar chemical responses to herbivore pressure. In two separate experiments, native, seasonal, host-adapted lepidopteran herbivores (eastern tent caterpillar, Malacosoma americana F., and fall webworm, Hyphantria cunea Drury) were caged and allowed to feed on seedlings from burned and non-burned sites on two dates during the 1999 growing season. We found little difference in plant chemistry among our burn treatments, but sample year strongly influenced our results, perhaps due to fluctuations in soil conditions caused by drought in the post-burn year (1999). Foliar calcium levels were moderately lower in seedlings from burned sites the year of the burn ( P=0.06), but this difference disappeared 1 year post-burn. Most phytochemical components were higher in seedlings sampled 1 year post-burn (1999) than in those sampled in the year of the burn (1998). Regardless of burn (site) treatment, caterpillar feeding resulted in foliage with lower concentrations of carbohydrates ( P=0.0001), nitrogen ( P=0.006), and tannins ( P=0.06). Foliar carbohydrates tended to increase within each year, and appeared inversely related to foliar nitrogen and tannins. Our results do not support the hypothesis that prescribed burning alters white oak seedling phytochemistry, or increases seedling susceptibility to herbivory through bottom-up changes in foliar chemistry, nor do they explain anecdotal accounts of increased herbivory on burned sites.

Vitamin D depletion following burn injury in children: a possible factor in post-burn osteopenia.

Children burned > 40% total body surface area (TBSA) have chronically low bone mineral density (BMD) and increased risk for fractures and adult-onset osteoporosis. Because they are advised to avoid sunlight to prevent burn scar hyperpigmentation, we hypothesized that they develop vitamin D depletion, which could contribute to post-burn osteopenia. We studied 24 children, ages 5-20 years, burned > or = 40% TBSA 7.1 +/- 3.8 (SD) years, range 1.9-13.3 years, previously (n = 12) and 2.0 +/- 0.2, range 1.4-2.1 years, previously (n = 12), of which half received recombinant human growth hormone during the first post-burn year. We measured lumbar spine BMD, serum 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)2D), intact PTH (iPTH), and osteocalcin. Serum 25(OH)D was low in 10/11 patients and 1,25(OH)2D was low in 5/11 at 7 years post-burn. Serum 25(OH)D was low in 10/12, while 1,25(OH)2D was low in 0/12 at 2 years; osteocalcin was low in 9/12 in the 7-year group; iPTH levels were in the lowest quartile in 5/12 patients at 7 years and 10/12 patients at 2 years. Serum 25(OH)D levels correlated with BMD z-scores, r = 0.53, p < 0.05, and inversely with iPTH levels, r = -0.66, p < 0.05, in the 7-year group. Burned children have low circulating levels of 25(OH)D which correlated with BMD z-scores, suggesting that post-burn vitamin D depletion may play a role in the chronically low bone density observed in these children.

Effects of Fire on Golden Eagle Territory Occupancy and Reproductive Success

We examined effects of fire on golden eagle (Aquila chrysaetos) territory occupancy and reproductive success in southwestern Idaho because wildfires since 1980 have resulted in large-scale losses of shrub habitat in the Snake River Plain. Success (percentage of pairs that raised young) at burned territories declined after major fires (P = 0.004). Pairs in burned areas that could expand into adjacent vacant territories were as successful as pairs in unburned territories and more successful than pairs in burned territories that could not expand. Success at extensively burned territories was lowest 4-6 years after burning but increased 4-5 years later. The incidence and extent of fires did not help predict territories that would have low occupancy and success rates in postburn years. The presence of a vacant neighboring territory and the amount of agriculture and proportion of shrubs within 3 km of the nesting centroid best predicted probability of territory occupancy. Nesting success during preburn years best predicted the probability of a territory being successful in postburn years. Burned territories with high success rates during preburn years continued to have high success rates during postburn years, and those with low success in prebum years continued to be less successful after burning. In areas where much shrub habitat has been lost to fire, management for golden eagles should include active fire suppression and rehabilitation of burned areas.

Fire and the chemistry of a South African mountain stream

The effects of a late-summer prescribed burn on the chemistry of a second-order mountain stream in the south-western Cape, South Africa, were investigated. Nitrate concentrations in stream water were significantly higher during the winter of the post-burn year. Increased concentrations of chloride, bicarbonate, polyphenols and potassium and decreased sodium concentrations were also recorded. Concentrations of ammonium, phosphate, calcium, magnesium, total dissolved solids and hydrogen ions were not significantly affected by the burn. Ionic export from the catchment was generally greater in the post-burn year. Apart from nitrate, however, values probably lie within the natural range of year-to-year variation. It is predicted that enhanced losses of nitrate will decrease progressively with the recovery of the vegetation and the re-establishment of soil/plant nutrient cycles. Atmospheric losses of nutrients in smoke were unquantified, but may be of more significance to site productivity than losses through surface runoff, which, in the case of nitrogen, appear to be compensated by precipitation inputs.

THE BENTHIC MACROINVERTEBRATE FAUNA OF A SOUTH AFRICAN MOUNTAIN STREAM AND ITS RESPONSE TO FIRE

Summary The effects of a late-summer prescribed burn on the temperature and benthic macroinvertebrate fauna of a south-western Cape mountain stream were investigated over a period of 12 months. Temperature and discharge regimes appear well-defined and relatively predictable from year to year. As in other mediterranean-type ecosystems, seasonal changes in the structure of the invertebrate community and the relative abundance of different feeding groups appear to be associated primarily with changes in the physical environment. Distinctive summer and winter communities were identified, with chironomids dominating the fauna in summer and simuliids dominant in winter. Although the riparian vegetation was only slightly damaged by the fire, a heavy, aseasonal leaf-fall occurred shortly afterwards. The canopy remained sparse for approximately four months. Stream temperature in the post-burn year was not demonstrably affected by increased exposure to solar radiation, however, probably because the canopy remained ...

Growth Delay in Postburn Pediatric Patients

Dampened height and weight velocities have been observed in our postburn pediatric population. To validate this phenomenon, the medical records of 80 patients who had sustained a greater than 40% total body surface area burn, were older than 2 years of age at the time of the burn, and were at least 1 year post burn were reviewed. All patients were treated with early excision of the burn wound within 72 hours of injury and received standard post burn resuscitational and nutritional support. Admission height and weight plots were within normal distribution parameters. Yearly growth velocities were calculated for up to 3 years after the burn. Despite adequate nutritional support and maximal exercise and/or long-bone stresses, a profound growth arrest was noted during postburn year 1, which slowly resolved to near normal distribution by postburn year 3. This retrospective study demonstrates that severe thermal injury is associated with a growth delay in the pediatric population. The exact cause of this phenomenon remains unknown.

Regional Disturbance Effects on Herb Succession Patterns in Coastal Sage Scrub

A more prolonged grazing history and higher summer air pollution loads in the basin inland of Los Angeles may be acting in concert to eliminate native perennial grasses there; such grasses comprise a significant part of the post-fire herb flora in coastal sites of coastal sage scrub. In addition, low resprouting vigour of subshrubs inland after fire permits a higher level of herb cover, initially of forbs, and later of non-native annual grasses. The divergent successional patterns of the post-fire herb stratum at the coast versus inland appear to result from subtle interactions between natural and anthropogenic forces in the region. Strict 'fire annuals' species that exhibit high cover in the first postburn year and disappear thereafter were not found in the study sites. Annuals that were present in large numbers in the first year persisted to varying degrees in the 4 years

Prescribed Burning in the Oak-pine Forest of the New Jersey Pine Barrens: Effects on Growth and Nutrient Dynamics of Two Quercus Species

To determine the effect of the transient increase in nutrient availability which follows prescribed burning in the New Jersey Pine Barrens, we monitored growth and foliar nutrient dynamics of white oak (Quercus alba) and chestnut oak (Q. prinus) in neighboring burned and unburned plots. Growth rates of oak trees in the burned plot were significantly higher in 1985 (the postburn year) than in the 4 years prior to the fire. Growth increases in the burned site averaged 55 % for white oak and 38% for chestnut oak. In contrast, relative growth rates of reference site Quercus trees did not differ between preburn and postburn years. Phosphorus resorption and calcium deposition in chestnut oak were greater in the burned site, though growth efficiencies did not differ between chestnut oak trees in the burned and reference sites. Calcium deposition and phosphorus growth efficiency of white oak were greater in the burned site; no differences in white oak N or P resorption were noted. These oaks showed rapid growth responses to the transient increases in nutrient supply produced by prescribed burning. Pinus rigida growth also increased slightly, though the increase was less than those of the oaks. These results contradict earlier assertions of the efficacy of sporadic prescribed burning as a management tool in these oak-pine forests and suggest that sporadic prescribed burning may accelerate, not retard, succession toward oak dominance. INTRODUCTION Since the early 1930s the use of prescribed burning as a forest management tool in the New Jersey Pine Barrens has been justified on the basis of four postulated benefits: (1) improvement of the seedbed for Pinus establishment; (2) preventing the exdusion of Pinus by oaks (Quercus spp.) by slowing or stopping oak growth, and killing oak saplings; (3) reduction of the fuel mass and therefore wildfire probability, and (4) improvement of soil fertility by the release of nutrients bound in the litter and humus (Little and Moore, 1945; Burns, 1952). Though we have demonstrated that prescribed burning on a 3-yr rotation does not mineralize a significantly greater mass of mineral nutrients than occurs through litter decay (Boerner and Lord, 1984), significant transient increases in nutrient availability may occur immediately after a prescribed burn. Current knowledge of the relationship between nutrient availability, nutrient use efficiency, and growth of oaks (Ostman and Weaver, 1982; Boerner, 1984) and the response of stress-tolerating trees to transient increases in nutrient availability (Grime, 1979) suggests that periodic prescribed burning would increase, not decrease, oak growth rate, though possibly at the expense of decreased nutrient use efficiency. If true, the effect of prescribed burning would be to ac'All correspondence should be forwarded to this author.

Small Mammal Populations in an Unburned and Early Fire Successional Sagebrush Community

Species composition and total numbers of small mammals changed little in the unburned sagebrush while individual species capture rates varied considerably. Following spring burning, the number of small mammal species and abundance were slightly. lower than control levels and were near unburned levels after 3 years. Species composition was greatly reduced on the fall bum in the first postburn year. Two years after burning four species were captured, although only two were caught in live-traps. Total small mammal density increased dramatically in the first two postburn years. The large increase in abundance on both bums was due primarily to Peromyscus maniculatus and Spermophilus armatus. Food use patterns on the fall burn were similar to those observed on the spring burn where small mammals utilized their preferred food types in relation to its abundance and availability. National Park. In unburned areas mountain big sagebrush (Artemisia tridentata vaseyana) is the most abundant shrub, forming dense, homogeneous stands. The most common grasses are wheatgrasses (Agropyron spp.), Idaho fescue (Festuca idahoensis), bluegrasses (Poa spp.) and needlegrasses (Stipa spp.). Characteristic forbs include yarrow (Archillea millefolium), wild buckwheat (Eriogonum umbellatum), geranium (Geranium spp.), lupine (Lupinus spp.), and northwest cinquefoil (Potentilla gracilis). Grasses and forbs form a continuous understory with few open areas. The sagebrush is bordered by stands of Douglas-fir (Pseudotsuga menziesii) and aspen (Populus tremuloides).

Dynamics of Colonization and Abundance in Central Alaskan Populations of the Northern Red-Backed Vole, Clethrionomys rutilus

Population dynamics of Clethrionomys rutilus and Microtus oeconomus were examined during colonization of a severely burned (July 1971) area of black spruce forest, located 40 km north of Fairbanks, Alaska. Livetrapping from June 1972 to September 1976 on two trapping grids, one in burned and the other in unburned forest, revealed that colonization of the burned area by Clethrionomys was gradual, characterized by midwinter abandonment until food and cover resources were sufficient to allow overwintering in 1975, four years after the fire. Reproduction did not occur on the burned area during the first two post-burn years. Despite establishment of a resident population in 1975, recruitment was dependent upon immigrant voles, particularly pregnant females. A high rate of immigration into recently burned areas, and hence successful colonization, is possible for Clethrionomys because source populations exist in all areas of mature forest. Microtus oeconomus , captured only twice on the unburned area, arrived on the burned area in 1974, three years after the fire. However, Microtus density was low, and the population consisted primarily of transient voles. Clethrionomys density underwent a simple sequence of annual fluctuations. In unburned forest, peak density, variable from year to year, was reached in the fall, and low densities occurred yearly in early summer. Density was high in 1974 and 1975, low in 1972, 1973, and 1976. High 1974 and 1975 densities were due to increased reproductive output, especially of first generation (spring-born) females. Stomach content analysis indicated that Clethrionomys relied heavily upon the fruits of several berry-producing plants in all seasons. The phenology of central Alaska fruit production results in fruit scarcity in early summer; it is hypothesized that this variable strongly influences population density each year and perhaps the amplitude of the annual cycle of abundance.