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Thomas J. Stohlgren

Publications and source records attributed to Thomas J. Stohlgren.

53 records · Page 3Linked to original sources
USGS1992

Evaluating wilderness recreational opportunities: application of an impact matrix

An inventory of the severity and spatial distribution of wilderness campsite impacts in Sequoia and Kings Canyon National Parks identified a total of 273 distinct nodes of campsites or “management areas.” A campsite impact matrix was developed to evaluate management areas based on total impacts (correlated to the total area of campsite development) and the density, or concentration, of impacts relative to each area's potentially campable area. The matrix is used to quantify potential recreational opportunities for wilderness visitors in a spectrum from areas offering low impact-dispersed camping to those areas offering high impact-concentrated camping. Wilderness managers can use this type of information to evaluate use distribution patterns, identify areas to increase or decrease use, and to identify areas needing site-specific regulations (e.g., one-night camping limits) to preserve wilderness resources and guarantee outstanding opportunities for solitude.

Environmental Management↗
USGS1992

Resilience of a heavily logged grove of giant sequoia ( Sequoiadendron giganteum ) in Kings Canyon National Park, California

The Big Stump Grove of giant sequoia ( Sequoiadendron giganteum (Lindl.) Buchholz) was heavily logged between 1883 and 1889 and the stand naturally regenerated from seed following logging. In 1968, as part of a 100% sequoia tree inventory, all living sequoias ( n = 3587) and dead trees and stumps ( n =588) were measured (diameter at breast height, dbh) and mapped. A comparison of pre- to post-logging (85 years later in 1968) stand characteristics showed the estimated basal area of 56.7 m 2 ha −1 in the pre-cut 1883 Big Stump Grove was very similar to the population mean basal area of 30 other giant sequoia groves (with more than 30 trees) in Sequoia and Kings Canyon National Parks. Sequoia density in 1968 was 1.5 times higher than the population mean, and over 45% of the basal area had been recovered after only 85 years. Assuming most re-establishment occurred over roughly a 9 year period (1883–1892), the diameter growth rate of trees less than 1.95 m dbh, averaged 6.1–6.8 mm year −1 but greatly varied as the 24 trees in the 1.8 m size class had a mean diameter growth rate of 21–24 mm year −1 . Data generated by dividing the grove into 0.25 ha contiguous plots indicated that only about 3.3 ha of the pre-cut 1883 grove did not have sequoia regeneration whereas 16.5 ha of the 1968 grove had sequoia regeneration but no sign of logs or stumps. The proportion of only-regeneration plots was significantly greater ( P <0.05) in peripheral areas compared to core areas of the grove. A stage projection model showed that with typical natality, growth, and mortality rates in the current ( t =0; 1968) stand, overrepresentation of 0.3–1.2 m dbh trees may produce a bimodal size distribution lasting perhaps 800 years or more into the future. Giant sequoia stand characteristics such as age and size structure are not highly resilient and may take several centuries to approach the ‘domain’ of age or size structure typical of old-growth sequoia forests. Grove boundaries may be less stable following a major disturbance.

Forest Ecology and Management↗
USGS1991

Atmospheric deposition and solute export in giant sequoia: Mixed conifer watersheds in the Sierra Nevada, California

Atmospheric depostion and stream discharge and solutes were measured for three years (September 1984 — August 1987) in two mixed conifer watersheds in Sequoia National Park, in the southern Sierra Nevada of California. The Log Creek watershed (50 ha, 2067–2397 m elev.) is drained by a perennial stream, while Tharp's Creek watershed (13 ha, 2067–2255 m elev.) contains an intermittent stream. Dominant trees in the area include Abies concolor (white fir), Sequoiadendron giganteum (giant sequoia), A. magnifica (red fir), and Pinus lambertiana (sugar pine). Bedrock is predominantly granite and granodiorite, and the soils are mostly Pachic Xerumbrepts. Over the three year period, sulfate (SO 4 2− ), nitrate (NO 3 − ), and chloride (Cl −1 ) were the major anions in bulk precipitation with volume-weighted average concentrations of 12.6, 12.3 and 10.0 μeq/1, respectively. Annual inputs of NO 3 -N, NH 4 -N and SO 4 -S from wet deposition were about 60 to 75% of those reported from bulk deposition collectors. Discharge from the two watersheds occurs primarily during spring snowmelt. Solute exports from Log and Tharp's Creeks were dominated by HCO 3 − , Ca 2+ and Na + , while H + , NO 3 − , NH 4 + and PO 4 3− outputs were relatively small. Solute concentrations were weakly correlated with instantaneous stream flow for all solutes (r 2 <0.2) except HCO 3 − (Log Cr. r 2 = 0.72; Tharp's Cr. r 2 = 0.38), Na + (Log Cr. r 2 = 0.56; Tharp's Cr. r 2 = 0.47), and silicate (Log Cr. r 2 = 0.71; Tharp's Cr. r 2 = 0.49). Mean annual atmospheric contributions of NO 3 -N (1.6 kg ha −1 ), NH 4 -N (1.7 kg ha −1 ), and SO 4 -S (1.8 kg ha −1 ), which are associated with acidic deposition, greatly exceed hydrologic losses. Annual watershed yields (expressed as eq ha −1 ) of HCO 3 − exceeded by factors of 2.5 to 37 the annual atmospheric deposition of H + .

California↗
USGS1989

Effects of herbage removal on productivity of selected high-Sierra meadow community types

We investigated the effects of herbage removal on three subalpine meadow plant communities in the Rock Creek drainage of Sequoia National Park, California, USA. In the xeric Carex exserta Mkze. (short-hair sedge) type, annual aboveground productivity averaged 19 g/m 2 in control plots (clipped once after plant senescence in late September) over a five-year period. Annual aboveground productivity was enhanced about 30%–35% when plots in this community type were clipped more frequently (i.e., “additional” herbage removal in the early, mid, and late seasons) during each of four treatment years but was reduced by 13%–19% during a fifth (recovery) year in which all but late September clipping was suspended. In a moderately mesic Eleocharis pauciflora (Lightf.) Link. (few-flowered spike rush)- Calamagrostis breweri Thurb. (short-hair grass) type, control plot productivity averaged 115 g/m 2 /yr and was reduced by 20–30% by the additional herbage removal. A more mesic Deschampsia caespitosa (L.) Beauv. (tufted hairgrass)- Carex rostrata Stokes, (beaked sedge) type had the greatest mean above-ground productivity (169 g/m 2 /yr) but also showed damage (i.e., decrease in productivity by 15%–20%) caused by the additional herbage removal. These data suggest that long-term, intensive herbage removal may be more detrimental to moderately mesic and mesic subalpine meadow community types than to xeric types.

California↗
USGS1989

Effects of varying fire regimes on annual grasslands in the southern Sierra Nevada of California

Effects of up to three successive spring and fall burns on composition and biomass of the predominantly non-native grasslands of the southern Sierra Nevada foothills were evaluated. Fall and spring burning regimes increased the number and biomass of both alien and native forb species. No native grass species became established following the treatments. Thus, whereas the biomass of alien grass species can be reduced by repeated burning, they will be replaced by increases in both alien and native forbs. Changes seen following one or two burns (spring or fall) were not sustained following cessation of burning treatment.

Madroño↗
USGS1988

Litter dynamics in two Sierran mixed conifer forests. I. Litterfall and decomposition rates

Litterfall was measured for 4 years and leaf litter decomposition rates were studied for 3.6 years in two mixed conifer forest (giant sequoia-fir and fir-pine) in the southern Sierra Nevada of California. The giant sequoia-fir forest (GS site) was dominated by giant sequoia ( Sequoiadendron giganteum (Lindl.) Buchh.), white fir ( Abies concolor Lindl. & Gord.), and sugar pine ( Pinus lambertiana Dougl.). The fir-pine forest (FP site) was dominated by white fir, sugar pine, and incense cedar ( Calocedrus decurrens (Torr.) Florin). Litterfall, including large woody debris <15.2 cm in diameter, at the GS site averaged 6364 kg•ha -1 •year -1 compared with 4355 kg•ha -1 •year -1 at the FP site (3.4:1). In the GS site, leaf litter decomposition after 3.6 years was slowest for giant sequoia (28.2% mass loss), followed by sugar pine (34.3%) and white fie (45.1%). In the FP site, mass loss was slowest for sugar pine (40.0%), followed by white fir (45.1%), while incense cedar showed the greatest mass loss (56.9%) after 3.6 years. High litterfall rates of large woody debris (i.e., 2.5-15.2 cm diameter) and slow rates of leaf litter decomposition in the giant sequoia-fir forest type may result in higher litter accumulation rates than in the fir-pine type. Leaf litter times to 95% decay for the GS and FP sites were 30 and 27 years, respectively, if the initial 0.7-year period (a short period of rapid mass decay) was ignored in the calculation. A mass balance approach for total litterfall (<15.2 cm diameter) decomposition yielded lower decay constants than did the litterbag study and therefore longer times to 95% decay (57 years for the GS site and 62 years for the FP site).

Canadian Journal of Forest Research↗
USGS1988

Litter dynamics in two Sierran mixed conifer forests. II. Nutrient release in decomposing leaf litter

The factors influencing leaf litter decomposition and nutrient release patterns were investigated for 3.6 years in two mixed conifer forests in the southern Sierra Nevada of California. The giant sequoia–fir forest was dominated by giant sequoia ( Sequoiadendrongiganteum (Lindl.) Buchh.), white fir ( Abiesconcolor Lindl. & Gord.), and sugar pine ( Pinuslambertiana Dougl.). The fir–pine forest was dominated by white fir, sugar pine, and incense cedar ( Calocedrusdecurrens (Torr.) Florin). Initial concentrations of nutrients and percent lignin, cellulose, and acid detergent fiber vary considerably in freshly abscised leaf litter of the studied species. Giant sequoia had the highest concentration of lignin (20.3%) and the lowest concentration of nitrogen (0.52%), while incense cedar had the lowest concentration of lignin (9.6%) and second lowest concentration of nitrogen (0.63%). Long-term (3.6 years) foliage decomposition rates were best correlated with initial lignin/N ( r 2 = 0.94, p < 0.05), lignin concentration ( r 2 = 0.92, p < 0.05), and acid detergent fiber concentration ( r 2 = 0.80, p < 0.05). Patterns of nutrient release were highly variable. Giant sequoia immobilized N and P, incense cedar immobilized N and to a lesser extent P, while sugar pine immobilized Ca. Strong linear or negative exponential relationships existed between initial concentrations of N, P, K, and Ca and percent original mass remaining of those nutrients after 3.6 years. This suggests efficient retention of these nutrients in the litter layer of these ecosystems. Nitrogen concentrations steadily increase in decomposing leaf litter, effectively reducing the C/N ratios from an initial range of 68–96 to 27–45 after 3.6 years.

Canadian Journal of Forest Research↗
USGS1987

Variation of wet deposition chemistry in Sequoia National Park, California

Sequoia National Park has monitored wet deposition chemistry in conjunction with the National Atmospheric Deposition Program and National Trends Network (NADP/NTN), on a weekly basis since July, 1980. Annual deposition of H, NO 3 and SO 4 (0.045, 3.6, and 3.9 kg ha −1 a −1 , respectively) is relatively low compared to that measured in the eastern United States, or in the urban Los Angeles and San Francisco areas. Weekly ion concentrations are highly variable. Maximum concentrations of 324,162, and 156 μeq ol −1 of H, NO 3 and SO 4 have been recorded for one low volume summer storm (1.4 mm). Summer concentrations of NO 3 and SO 4 average two and five times higher, respectively, than concentrations reported for remote areas in the world. There is considerable variability in the ionic concentration of low volume samples, and much less variability in moderate and high volume samples.

California↗
USGS1986

Vegetation and soil recovery in wilderness campsites closed to visitor use

Recreational use of wilderness results in impacts to vegetation and soil in trails and campsites. Traditionally, campsite impact studies have compared campsites receiving various levels of use with unused control areas. Field studies in Sequoia National Park, California, indicate that the degree of impact to vegetation and soils also varies within campsites. The central areas of campsites, where trampling is concentrated, show lower plant species diversity, differences in relative species cover, more highly compacted soils, and lower soil nutrient concentrations than do peripheral, moderately trampled, and untrampled areas within the same campsite. Three years after closure to visitor use, the central areas show less increase in mean foliar plant cover, and soils remain more highly compacted than in previously moderately trampled areas of the same sites. Changes in relative species cover over time are used to assess both resiliency to trampling and species composition recovery within campsites closed to visitor use.

California↗
USGS1986

A population model for a long-lived, resprouting chaparral shrub: Adenostoma fasciculatum

Extensive stands of Adenostoma fasciculatum H.&A. (chamise) in the chaparral of California are periodically rejuvenated by fire. A population model based on size-specific demographic characteristics (thinning and fire-caused mortality) was developed to generate probable age distributions within size classes and survivorship curves for typical stands. The model was modified to assess the long term effects of different mortality rates on age distributions. Under observed mean mortality rates (28.7%), model output suggests some shrubs can survive more than 23 fires. A 10% increase in mortality rate by size class slightly shortened the survivorship curve, while a 10% decrease in mortality rate by size class greatly elongated the curve. This approach may be applicable to other long-lived plant species with complex life histories.

Ecological Modelling↗
USGS1982

Wilderness permit accuracy: differences between reported and actual use

Wilderness permits are valuable tools for recording backcountry use patterns. They provide a valuable basis upon which management decisions are made. Unfortunately, significant inaccuracies in reporting permit data result from noncompliance, transmission errors, and changes in visitor plans. Data from Sequoia and Kings Canyon National Parks in California show that in 1978, 97 percent of the parties obtained wilderness permits. Changes in visitor plans resulted in an over-reporting of total persons by 8 percent and of visitor nights by 23 percent. The latter was due primarily to shortening of trip length. Over-reporting was greatest when permits were issued well in advance of the trip. Backcountry managers should be aware of possible inaccuracies in permit data and may want to adjust for them under certain circumstances.

Environmental Management↗
USGS1981

Establishing backcountry use quotas: an example from Mineral King, California

Increasing levels of visitor use and consequent resource damage have necessitated that backcountry use restrictions be established in the Mineral King area of Sequoia National Park, California. In this paper we review the steps taken in developing a trailhead quota system. The availability of acceptable campsites, based on a detailed inventory of site distribution and impact, was used to quantitatively derive use capacities for each camp area. Wilderness permit data on visitor dispersal patterns from the major trailheads, including length of stay at each camp area, were then used to translate the area capacities into daily trailhead quotas that would assure that these capacities were not surpassed. The general approach is applicable to any backcountry area, although large complex areas may require the use of available computer simulation models.

California↗