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Geology topics

Jill Baron

Publications and source records attributed to Jill Baron.

At least 109 records · Page 6Linked to original sources
USGS1998

Effects of landcover, water redistribution, and temperature on ecosystem processes in the South Plate Basin

Over one-third of the land area in the South Platte Basin of Colorado, Nebraska, and Wyoming, has been converted to croplands. Irrigated cropland now comprises 8% of the basin, while dry croplands make up 31%. We used the RHESSys model to compare the changes in plant productivity and vegetation-related hydrological processes that occurred as a result of either land cover alteration or directional temperature changes (&minus;2&deg;C, +4&deg;C). Land cover change exerted more control over annual plant productivity and water fluxes for converted grasslands, while the effect of temperature changes on productivity and water fluxes was stronger in the mountain vegetation. Throughout the basin, land cover change increased the annual loss of water to the atmosphere by 114 mm via evaporation and transpiration, an increase of 37%. Both irrigated and nonirrigated grains became active earlier in the year than shortgrass steppe, leading to a seasonal shift in water losses to the atmosphere. Basin-wide photosynthesis increased by 80% due to grain production. In contrast, a 4&deg;C warming scenario caused annual transpiration to increase by only 3% and annual evaporation to increase by 28%, for a total increase of 71 mm. Warming decreased basin-wide photosynthesis by 16%. There is a large elevational range from east to west in the South Platte Basin, which encompasses the western edge of the Great Plains and the eastern front of the Rocky Mountains. This elevational gain is accompanied by great changes in topographic complexity, vegetation type, and climate. Shortgrass steppe and crops found at elevations between 850 and 1800 m give way to coniferous forests and tundra between 1800 and 4000 m. Climate is increasingly dominated by winter snow precipitation with increasing elevation, and the timing of snowmelt influences tundra and forest ecosystem productivity, soil moisture, and downstream discharge. Mean annual precipitation of <500 mm on the plains below 1800 m is far less than potential evapotranspiration of 1000&ndash;1500 mm and is insufficient for optimum plant productivity. The changes in water flux and photosynthesis from conversion of steppe to cropland are the result of redistribution of snowmelt water from the mountains and groundwater pumping through irrigation projects.

Ecological Applications↗
USGS1998

Using geostatistical methods to estimate snow water equivalence distribution in a mountain watershed

Knowledge of the spatial distribution of snow water equivalence (SWE) is necessary to adequately forecast the volume and timing of snowmelt runoff. In April 1997, peak accumulation snow depth and density measurements were independently taken in the Loch Vale watershed (6.6 km 2 ), Rocky Mountain National Park, Colorado. Geostatistics and classical statistics were used to estimate SWE distribution across the watershed. Snow depths were spatially distributed across the watershed through kriging interpolation methods which provide unbiased estimates that have minimum variances. Snow densities were spatially modeled through regression analysis. Combining the modeled depth and density with snow-covered area (SCA produced an estimate of the spatial distribution of SWE. The kriged estimates of snow depth explained 37-68% of the observed variance in the measured depths. Steep slopes, variably strong winds, and complex energy balance in the watershed contribute to a large degree of heterogeneity in snow depth.

Conference Paper↗
USGS1997

Nitrogen fluxes in a high elevation Colorado Rocky Mountain basin

Measured, calculated and simulated values were combined to develop an annual nitrogen budget for Loch Vale Watershed (LVWS) in the Colorado Front Range. Nine-year average wet nitrogen deposition values were 1·6 ( s =0·36) kg NO 3 -N ha −1 , and 1·0 ( s =0·3) kg NH 4 -N ha −1 . Assuming dry nitrogen deposition to be half that of measured wet deposition, this high elevation watershed receives 3·9 kg N ha −1 . Although deposition values fluctuated with precipitation, measured stream nitrogen outputs were less variable. Of the total N input to the watershed (3·9 kg N ha −1 wet plus dry deposition), 49% of the total N input was immobilized. Stream losses were 2·0 kg N ha −1 (1125 kg measured dissolved inorganic N in 1992, 1–2 kg calculated dissolved organic N, plus an average of 203 kg algal N from the entire 660 ha watershed). Tundra and aquatic algae were the largest reservoirs for incoming N, at approximately 18% and 15% of the total 2574 kg N deposition, respectively. Rocky areas and forest stored the remaining 11% and 5%, respectively. Fully 80% of N losses from the watershed came from the 68% of LVWS that is alpine. © 1997 John Wiley & Sons, Ltd.

Hydrological Processes↗
USGS1997

Assessment of climate change and freshwater ecosystems of the Rocky Mountains, USA and Canada

The Rocky Mountains in the USA and Canada encompass the interior cordillera of western North America, from the southern Yukon to northern New Mexico. Annual weather patterns are cold in winter and mild in summer. Precipitation has high seasonal and interannual variation and may differ by an order of magnitude between geographically close locales, depending on slope, aspect and local climatic and orographic conditions. The region's hydrology is characterized by the accumulation of winter snow, spring snowmelt and autumnal baseflows. During the 2–3-month ‘spring runoff’ period, rivers frequently discharge > 70% of their annual water budget and have instantaneous discharges 10–100 times mean low flow.

Hydrological Processes↗
USGS1997

Chemical characteristics of particulate, colloidal, and dissolved organic material in Loch Vale Watershed, Rocky Mountain National Park

The chemical relationships among particulate and colloidal organic material and dissolved fulvic acid were examined in an alpine and subalpine lake and two streams in Loch Vale Watershed, Rocky Mountain National Park. The alpine lake, Sky Pond, had the lowest dissolved organic carbon (DOC) (0.37 mgC/L), the highest particulate carbon (POC) (0.13 mgC/L), and high algal biomass. The watershed of Sky Pond is primarily talus slope, and DOC and POC may be autochthonous. Both Andrews Creek and Icy Brook gain DOC as they flow through wet sedge meadows. The subalpine lake, The Loch, receives additional organic material from the surrounding forest and had a higher DOC (0.66 mgC/L). Elemental analysis, stable carbon isotopic compositon, and 13C-NMR characterization showed that: 1) particulate material had relatively high inorganic contents and was heterogeneous in compositon, 2) colloidal material was primarily carbohydrate material with a low inorganic content at all sites; and 3) dissolved fulvic acid varied in compositon among sites. The low concentration and carbohydrate-rich character of the colloidal material suggests that this fraction is labile to microbial degradation and may be turning over more rapidly than particulate fractions or dissolved fulvic acid. Fulvic acid from Andrews Creek had the lowest N content and aromaticity, whereas Sky Pond fulvic acid had a higher N content and lower aromaticity than fulvic acid from The Loch. The UV-visible spectra of the fulvic acids demonstrate that variation in characteristics with sources of organic carbon can explain to some extent the observed nonlinear relationship between UV-B extinction coefficients and DOC concentrations in lakes.

Colorado↗
USGS1994

Effects of mesoscale vegetation distributions in mountainous terrain on local climate

Even a casual observer from an aircraft will note the varied landscape of mountainous terrain. These variations in land surface include the terrain features themselves as well as patchiness from different vegetation types, surface geology, urbanization, etc. There are two major questions related to climate system dynamics that need to be addressed concerning this landscape heterogeneity: (i) how would a large-scale climate change influence this landscape, and (ii) does landscape spatial and temporal structure influence the larger-scale climate?

Book chapter↗
USGS1993

Winter phytoplankton dynamics in a subalpine lake, Colorado, U.S.A

The temporal dynamics of phytoplankton were examined in The Loch, a subalpine lake in Rocky Mountain National Park, over the winter seasons of 1987-88 and 1988-89. The Loch was ice-covered from early November until early to mid May. The pattern of phytoplankton biovolume during ice-cover was consistent between the two years with maxima occurring in November/December and February/March. This pattern resulted principally from the contribution of Asterionella formosa Hass. Other dominant phytoplankton species in terms of biomass ( Dinobryon sertularia Ehrenb., Cryptomonas ovata Ehrenb., and Peridinium cinctum (Müll.) Ehrenb.) collectively contributed from 10 to 90 % of the total cells. Algal composition changed throughout the winter and individual species varied in abundance with depth. The same dominant (and most of the rare) taxa were present both years. They varied in time of occurrence and abundance, but did not occur at the same time in both years. Phytoplankton species composition continually fluctuated throughout the winter. Because of the stability afforded by ice-cover, algal species succession was not driven by thermal regime or by wind induced changes in the mixed depth. Nor did grazing by the winter zooplankton assemblage, composed nearly exclusively of cyclopoid copepods and rotifers, adequately explain the phytoplankton dynamics. Freeze concentration of water (concentration as ions are excluded in the formation of ice) in early winter may be responsible for the early phytoplankton bloom.

Colorado↗