Geology topics

David J. Parsons

Publications and source records attributed to David J. Parsons.

10 recordsLinked to original sources

USGS2009

Guiding concepts for park and wilderness stewardship in an era of global environmental change

The major challenge to stewardship of protected areas is to decide where, when, and how to intervene in physical and biological processes, to conserve what we value in these places. To make such decisions, planners and managers must articulate more clearly the purposes of parks, what is valued, and what needs to be sustained. A key aim for conservation today is the maintenance and restoration of biodiversity, but a broader range of values are also likely to be considered important, including ecological integrity, resilience, historical fidelity (ie the ecosystem appears and functions much as it did in the past), and autonomy of nature. Until recently, the concept of “naturalness” was the guiding principle when making conservation‐related decisions in park and wilderness ecosystems. However, this concept is multifaceted and often means different things to different people, including notions of historical fidelity and autonomy from human influence. Achieving the goal of nature conservation intended for such areas requires a clear articulation of management objectives, which must be geared to the realities of the rapid environmental changes currently underway. We advocate a pluralistic approach that incorporates a suite of guiding principles, including historical fidelity, autonomy of nature, ecological integrity, and resilience, as well as managing with humility. The relative importance of these guiding principles will vary, depending on management goals and ecological conditions.

Frontiers in Ecology and the Environment↗

USGS2003

Growth rate predicts mortality of Abies concolor in both burned and unburned stands

Tree mortality is often the result of both long-term and short-term stress. Growth rate, an indicator of long-term stress, is often used to estimate probability of death in unburned stands. In contrast, probability of death in burned stands is modeled as a function of short-term disturbance severity. We sought to narrow this conceptual gap by determining ( i ) whether growth rate, in addition to crown scorch, is a predictor of mortality in burned stands and ( ii ) whether a single, simple model could predict tree death in both burned and unburned stands. Observations of 2622 unburned and 688 burned Abies concolor (Gord. & Glend.) Lindl. (white fir) in the Sierra Nevada of California, U.S.A., indicated that growth rate was a significant predictor of mortality in the unburned stands, while both crown scorch and radial growth were significant predictors of mortality in the burned stands. Applying the burned stand model to unburned stands resulted in an overestimation of the unburned stand mortality rate. While failing to create a general model of tree death for A. concolor , our findings underscore the idea that similar processes may affect mortality in disturbed and undisturbed stands.

Canadian Journal of Forest Research↗

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↗

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↗

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↗

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↗