Spring Snowpack Research Articles

RESPONSE OF HERBS TO SHRUB REMOVAL ACROSS NATURAL AND EXPERIMENTAL VARIATION IN SOIL MOISTURE

Like many semiarid grasslands, large montane meadows of the Sierra Nevada Mountains, California (USA) have experienced widespread expansion of woody plants (here Rothrock sagebrush, or Artemisia rothrockii), a reduction in herbaceous species cover, and apparent aridification over the past century. Because soil moisture is an important limiting resource in this system, we investigated the interactive effects of shrub removal and soil moisture on herbaceous species recovery. We conducted replicated shrub removal experiments across four sagebrush habitats that differed in soil moisture, water table depth, and related characteristics (e.g., soil texture, initial total herbaceous cover, and initial shrub biomass). Changes in herb cover after shrub removal were monitored over four years that differed in spring snow pack, a critical source of water in this system. To more directly quantify the effects of soil moisture on shrub–herb competition, shrub removal was combined with experimental water addition in the most xeric habitat and monitored for two years. Total herb cover increased significantly with shrub removal, but the magnitude of this effect varied among years and habitats, and with experimental watering. Regardless of the source of soil moisture variation (i.e., experimental, spatial, or temporal variation), the absolute change in herb cover with shrub removal increased linearly with moisture at the dry end of the gradient (<15% gravimetric soil moisture). An apparent reversal of this trend under wetter conditions was not possible to evaluate due to few data points above 15% soil moisture. Sagebrush growth rates increased with surface soil moisture, suggesting that this woody species can use water sources similar to those used by herbaceous species. In xeric sites dominated by sagebrush, increasing water availability alone is unlikely to increase herb biomass because suppression by shrubs negates the positive effect of watering. Shrub removal alone has the potential to increase herb biomass at mesic sites or during wet years at xeric sites.

Genesis of Bisequal Soils on Acidic Drift in the Upper Great Lakes Region, USA

Seventeen bisequal pedons were characterized on drift primarily from the Greatlakean advance [ca. 12 000 yr before present (BP)] in northern Wisconsin and the upper Michigan. The pedons, Alfic Haplorthods and Alfic Oxyaquic Fragiorthods, contain an Orthod sequum over an Udalf sequum and are derived primarily from coarse‐loamy or coarse‐silty materials overlying stratified sand and gravel or coarse‐loamy materials. The upper sequum contains abundant roots and is very strongly acidic (pH 4.8), low in clay (<4.8%) and base cations (<20% base saturation), and high in exchangeable acidity (13 cmolc kg−1) and exchangeable Al (60% saturation). The lower sequum contains few roots, is strongly acidic (pH 5.4), is more enriched in clay (8.0%) and base cations (45% base saturation), and has lower exchangeable acidity and Al than the upper sequum. The occurrence and position of argillic and fragic horizons in the profile are favored by a lithologic discontinuity. The two horizons may form exclusive of one another. On the basis of soil solution chemistry data and mass‐balance studies, the argillic horizon has formed from neoformation of clays with some clay migration. The fragic materials are of pedogenic origin and are forming in the upper part of a degrading argillic horizon. The soils have undergone environmental changes during the past 12 000 yr, but they appear to have originated from processes that are occurring today that result from extensive leaching during melting of the spring snowpack and solute movement in two‐storied parent materials. The soils are strongly developed in view of the short snow‐free season.

Genesis of Bisequal Soils on Acidic Drift in the Upper Great Lakes Region, USA

Seventeen bisequal pedons were characterized on drift primarily from the Greatlakean advance [ca. 12 000 yr before present (BP)] in northern Wisconsin and the upper Michigan. The pedons, Alfic Haplorthods and Alfic Oxyaquic Fragiorthods, contain an Orthod sequum over an Udalf sequum and are derived primarily from coarse-loamy or coarse-silty materials overlying stratified sand and gravel or coarse-loamy materials. The upper sequum contains abundant roots and is very strongly acidic (pH 4.8), low in clay (<4.8%) and base cations (<20% base saturation), and high in exchangeable acidity (13 cmolc kg−1) and exchangeable Al (60% saturation). The lower sequum contains few roots, is strongly acidic (pH 5.4), is more enriched in clay (8.0%) and base cations (45% base saturation), and has lower exchangeable acidity and Al than the upper sequum. The occurrence and position of argillic and fragic horizons in the profile are favored by a lithologic discontinuity. The two horizons may form exclusive of one another. On the basis of soil solution chemistry data and mass-balance studies, the argillic horizon has formed from neoformation of clays with some clay migration. The fragic materials are of pedogenic origin and are forming in the upper part of a degrading argillic horizon. The soils have undergone environmental changes during the past 12 000 yr, but they appear to have originated from processes that are occurring today that result from extensive leaching during melting of the spring snowpack and solute movement in two-storied parent materials. The soils are strongly developed in view of the short snow-free season.

The Relationship between Climate and Rothrock Sagebrush Colonization Patterns

In montane meadows of the southern Sierra Nevada mountains (Calif., USA), Rothrock sagebrush (Artemisia rothrockii G.) has expanded into sites once dominated by herbaceous species. We explored the relationship between climate and shrub establishment by estimating Rothrock sagebrush age distributions from growth rings. We compared these age distributions with annual records of spring snowpack and summer precipitation across 4 vegetation types that differed in water table depth, soil moisture, and vegetation cover. In the 2 vegetation types where the water table is consistently deeper than 1 m, Rothrock sagebrush stands were up to 40 years old and had relatively even age structures that showed no strong relationship to climate. In the 2 vegetation types with a shallow water table - but with contrasting soil moisture and herbaceous cover - the majority of shrubs colonized synchronously between 1984 and 1994, a relatively dry period that followed the wet 1982 to 1983 El Nino. These and other published data suggest that initial shrub colonization of new sites is facilitated by wet years, which may increase seed production, germination, and seedling survival. However, once sagebrush stands are established and local seed supply is abundant, its continued recruitment seems independent of climate. DOI:10.2458/azu_jrm_v55i6_bauer

Dicarboxylic acids in the Arctic aerosols and snowpacks collected during ALERT 2000

Saturated (C 2–C 11) and unsaturated (C 4–C 5, C 8) dicarboxylic acids were measured in Arctic aerosol and surface snowpack samples collected during dark winter (February) and light spring (April–May) using a gas chromatography and gas chromatography/mass spectrometry. Their molecular distributions were characterized by a predominance of oxalic acid (C 2), except for few spring snowpack samples that showed the predominance of succinic acid (C 4). Concentrations of short-chain saturated diacids (C 3–C 5) and 4-ketopimelic acid in the aerosol samples increased by a factor of ∼5 from winter to spring. In contrast, those of saturated C 6–C 11 diacids and unsaturated (maleic, methylmaleic and phthalic) acids decreased by a factor of ∼4 from winter to spring aerosol samples. Snowpack samples also showed a similar trend. These results of the aerosol samples suggested that, the diacids are largely produced in spring by photochemical oxidation of hydrocarbons and other precursors that are transported long distances from the mid- and low-latitudes to the Arctic, but the production of oxalic acid is in part counteracted by photo-induced degradation possibly associated with bromine chemistry.

Growth responses of subalpine fir to climatic variability in the Pacific Northwest

We studied regional variation in growth-limiting factors and responses to climatic variability in subalpine forests by analyzing growth patterns for 28 tree-ring growth chronologies from subalpine fir (Abies lasiocarpa (Hook.) Nutt.) stands in the Cascade and Olympic Mountains (Washington and Oregon, U.S.A.). Factor analysis identified four distinct time series of common growth patterns; the dominant growth pattern at any site varied with annual precipitation and temperature (elevation). Throughout much of the region, growth is negatively correlated with winter precipitation and spring snowpack depth, indicating that growth is limited primarily by short growing seasons. On the driest and warmest sites, growth is negatively correlated with previous summer temperature, suggesting that low summer soil moisture limits growth. Growth patterns in two regions were sensitive to climatic variability associated with the Pacific Decadal Oscillation, apparently responding to low-frequency variation in spring snowpack and summer soil moisture (one negatively, one positively). This regional-scale analysis shows that subalpine fir growth in the Cascades and Olympics is limited by different climatic factors in different subregional climates. Climate–growth relationships are similar to those for a co-occurring species, mountain hemlock (Tsuga mertensiana (Bong.) Carrière), suggesting broad biogeographic patterns of response to climatic variability and change by subalpine forest ecosystems in the Pacific Northwest.

The relationship between climate and Rothrock sagebrush colonization patterns

In montane meadows of the southern Sierra Nevada mountains (Calif., USA), Rothrock sagebrush (Artemisia rothrockii G.) has expanded into sites once dominated by herbaceous species. We explored the relationship between climate and shrub establishment by estimating Rothrock sagebrush age distributions from growth rings. We compared these age distributions with annual records of spring snowpack and summer precipitation across 4 vegetation types that differed in water table depth, soil moisture, and vegetation cover. In the 2 vegetation types where the water table is consistently deeper than 1 m, Rothrock sagebrush stands were up to 40 years old and had relatively even age structures that showed no strong relationship to climate. In the 2 vegetation types with a shallow water table - but with contrasting soil moisture and herbaceous cover - the majority of shrubs colonized synchronously between 1984 and 1994, a relatively dry period that followed the wet 1982 to 1983 El Niño. These and other published data suggest that initial shrub colonization of new sites is facilitated by wet years, which may increase seed production, germination, and seedling survival. However, once sagebrush stands are established and local seed supply is abundant, its continued recruitment seems independent of climate.

MOUNTAIN HEMLOCK GROWTH RESPONDS TO CLIMATIC VARIABILITY AT ANNUAL AND DECADAL TIME SCALES

Improved understanding of tree growth responses to climate is needed to model and predict forest ecosystem responses to current and future climatic variability. We used dendroecological methods to study the effects of climatic variability on radial growth of a subalpine conifer, mountain hemlock (Tsuga mertensiana). Tree-ring chronologies were developed for 31 sites, spanning the latitudinal and elevational ranges of mountain hemlock in the Pacific Northwest. Factor analysis was used to identify common patterns of inter- annual growth variability among the chronologies, and correlation and regression analyses were used to identify climatic factors associated with that variability. Factor analysis identified three common growth patterns, representing groups of sites with different climate-growth relationships. At high-elevation and midrange sites in Wash- ington and northern Oregon, growth was negatively correlated with spring snowpack depth, and positively correlated with growth-year summer temperature and the winter Pacific Decadal Oscillation index (PDO). In southern Oregon, growth was negatively correlated with spring snowpack depth and previous summer temperature, and positively correlated with previous summer precipitation. At the low-elevation sites, growth was mostly insen- sitive to annual climatic variability but displayed sensitivity to decadal variability in the PDO opposite to that found at high-elevation sites. Mountain hemlock growth appears to be limited by late snowmelt, short growing sea- sons, and cool summer temperatures throughout much of its range in the Pacific Northwest. Earlier snowmelt, higher summer temperatures, and lower summer precipitation in southern Oregon produce conditions under which growth is limited by summer temperature and/or soil water availability. Increasing atmospheric CO 2 concentrations could produce warmer temperatures and reduced snowpack depths in the next century. Such changes would likely increase mountain hemlock growth and productivity throughout much of its range in Washington and northern Oregon. Increased summer drought stress and reduced productivity would be likely, how- ever, in mountain hemlock forests of southern Oregon and near the species lower elevation

Postglacial history of subalpine forests, Olympic Peninsula, Washington, USA

To investigate subalpine vegetation history on the Olympic Peninsula, Washington (USA), two pollen, macrofossil and charcoal records were studied in climatically distinct zones: Martins Lake (1415 m) in the moist Tsuga mertensiana zone and Moose Lake (1508 m) in the drier Abies lasiocarpa zone. The interpretation of fossil pollen assemblages was aided by comparisons with 308 modern assemblages from the Olympic Peninsula and western North America. Both pollen records show a cold/dry period following deglaciation (.10000 radiocarbon years BP) with sparse tundra and little similarity to any modern pollen assemblage. In the early Holocene, when summer temperatures are thought to have been higher than present, high percentages of Alnus sinuata-type pollen at both lakes suggest increased avalanche activity. At Martins Lake warmer summers were not accompanied by forest establishment, possibly because persistent spring snow pack, snow avalanches, and/or edaphic constraints limited tree establishment at this site. The Martins Lake record shows a steplike shift in vegetation to modern Tsuga mertensiana Abies amabilis parkland across the Mazama tephra (6730 BP). In contrast to Martins Lake, Abies lasiocarpa forest quickly established at Moose Lake in the early Holocene, though forests were probably initially open and fires may have been frequent. From 7800 to 5100 BP forests near Moose Lake shifted gradually to cooler and moister species composition, with the addition of Chamaecyparis nootkatensis, Tsuga mertensiana and Pinus, though Abies lasiocarpa remained dominant. Forest cover was probably greatest during this transition, with parklike conditions at Moose Lake beginning at c. 5100 BP. The major differences in the records between the two sites may be due to differences in the local expression of regional climatic change and/or differences in soil development and stabilization.

Covariability of Spring Snowpack and Summer Rainfall across the Southwest United States

Abstract Interannual fluctuations of observed summer rainfall across the monsoon region of the southwestern United States are analyzed to ascertain their spatial coherence and to test the hypothesis that antecedent spring snowpack anomalies may modulate the monsoon and exhibit an inverse correlation with summer rainfall anomalies. To characterize the spatial coherence of seasonal rainfall anomalies, an objective linear analysis of interannual variability is applied to climate divisional data across the Southwest. Three coherent subregions are identified, broadly representing rainfall anomalies across Arizona, eastern New Mexico/western Texas (the Southwest Plains), and most of New Mexico. Interannual fluctuations of summer rainfall in the New Mexico region exhibit a very significant negative correlation with a large-scale index of the antecedent 1 April snowpack over the southern U.S. Rocky Mountains during the 1961–90 climatic averaging period. This strong relationship seems to break down in the years be...

Lack of Spring Snowpack Bodes Ill for Many

Science NewsVolume 158, Issue 6 p. 87-87 This Week Lack of spring snowpack bodes ill for many Sid Perkins, Sid PerkinsSearch for more papers by this author Sid Perkins, Sid PerkinsSearch for more papers by this author First published: 01 July 2009 https://doi.org/10.2307/3981272AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume158, Issue65 August 2000Pages 87-87 RelatedInformation

Effects of surface warming of a dry snowpack

Changes in air temperature, and hence snow temperature, influence snow stability for skiers. This paper studies how warming in the top 20 cm of a hard `spring' like snowpack and a softer `mid-winter' like snowpack influence the stresses and strains due to a skier load in weak layers 30 and 50 cm below the surface. The temperature effects are studied using a finite element model to predict how the load is transferred through a layered snowpack. The results show that the warming front does not have to extend into the weak layer to have an effect. As the stiffness of the top slab is reduced, the peak stress and peak strain increases in the weak layers. The 30-cm weak layer was more affected by the skier load than the 50-cm layer with an increase in shear stress of 8% in the mid-winter snowpack model and 51% in the spring snowpack model. A model of a real snowpack with a surface wind slab again subject to a skier load showed an increase in shear stress of 32% when a weak layer was present at 22 cm and the top 19 cm was warmed. The increase in stress and strain in the weak layer in all models support the argument that the likelihood of skier-induced avalanche will increase after warming.

Spring Snowpack Anomaly Patterns and Winter Climatic Variability, British Columbia, Canada

The objective of this study was to describe the spatial and temporal structure of spring snowpack anomalies in British Columbia, Canada, and to relate the anomaly patterns to climatic fluctuations. Cluster analysis was used to identify relatively homogeneous groups of snow course sites, based on the April 1 snowpack measurements, for the periotd 1966–1992. Time series of cluster‐averaged anomalies were then computed. Synoptic‐scale circulation types were defined by applying a correlation‐based map classification technique to gridded data sets of surface pressure and 500‐hPa height levels. Frequencies of the circulation types were calculated for each winter (November to March). Total precipitation and mean temperature for each winter were calculated from monthly data from 16 climate stations. Snowpack anomalies from 1966 to 1976 were dominated by two patterns: one characterized by generally heavier‐than‐average snowpacks over most of the province and the other by heavier‐than‐average snowpacks in the south and lighter‐than‐average in the north. From 1977 to 1992, snowpack conditions were generally either lighter than average over the whole province or were heavier than average in the north and lighter than average in the south. Snowpack and precipitation were generally correlated, although at some stations it appears that high winter temperatures, likely causing more midwinter melt and more rain, can act to reduce the snowpack. The differences in anomaly patterns and frequencies of synoptic types between the 1966–1976 and 1977–1992 periods accord with decadal‐scale shifts in sea surface temperatures and atmospheric circulation patterns over the North Pacific, as reported in the literature. The shift in snowpack anomaly patterns following 1976 is consistent with reported shifts in glacier mass balance and rates of retreat and with streamflow fluctuations.

Snowpack Ion Accumulation and Loss in a Basin Draining to Lake Superior

The objective of this study was to relate winter precipitation ionic inputs, snowpack retention, and change in first-order stream chemistry with spring snowpack melt. During winter 1982–83, measurement of precipitation inputs, snowpack concentration and loading, and streamwater concentration and discharge of Ca2+, K+, H+, NO3−, and SO42− from a 176-ha watershed reveals that only H+ might be lost from the snowpack before first thaw. Above-freezing soil temperature beneath the snowpack may be a factor in H+ loss. An initial 1-d thaw resulted in loss of over one third (6 eq∙ha−1) of the snowpack Ca2+. Over one half the snowpack load of K+, H+, NO3−, and SO42−, was lost in a subsequent midwinter freeze–thaw period. Snowpack loading of ionic species was reduced by 70–90% before peak spring melting and stream discharge. Ecosystem H+ retention and biological uptake of NO3− further mitigate ionic "pulses" in streamwater. Sulfate discharge exceeds bulk inputs, which suggests significant dry deposition input and little forest soil retention of this anion. The snowpack was relatively small, which limits wider application of these results to the region.

Time‐Variant Differences in Chemistry Among Four Small Streams

Concentrations of the major cations and silica were monitored in four small British Columbia Coast Mountain streams during the 1976 snowmelt season. The four streams could be grouped into three unique classes using logarithmically transformed calcium and potassium concentrations. The two most similar basins fed streams that were chemically indistinguishable. The next most similar basin yielded runoff that was chemically similar to the other two except for unusually low K+ concentration, possibly due to a shortage of biotite in the bedrock. The fourth stream had unusually high Ca++, Mg++, Na+, and silica concentrations due to the long residence time of groundwater from metamorphic rocks in its basin. Another different feature of that basin was the earlier depletion of its spring snowpack due to its south aspect. Time‐variant differences in chemistry among streams were measured as changing ratios of solute concentrations over time. Differences among streams were time‐variant due to time variance of interbasin runoff components. The relative contribution of groundwater increased in the basin with the metamorphic rocks and decreased in the other three basins over the summer. The chemical differences among streams were reflected in solute loads as well as solute concentrations. Therefore the major components of variable runoff and solute sources in the study area were high runoff and low solute yield from three basins on granite and low runoff but high solute yield from a basin on metamorphic rocks.

Geochemically alkaline snowpack in northern Utah mountains in spring of 1982

Cores from the 1982 spring snowpack in the Wasatch Mountains exhibited low concentrations of NO 3 −-N ( x ̄ = 100 μg1 −1) , thus tending to discount the impact of West Coast NO x sources on the Rocky Mountains. SO 4 = concentrations, presumably originating from the Salt Lake City/Provo metropolitan area, were higher (420 to 2340 μg 1 −1), but the associated acid was effectively titrated by alkaline dust, resulting in pH's ranging from 5.89 to 6.77.