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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Coordination of rooting, xylem, and stomatal strategies explains the response of conifer forest stands to multi-year drought in the southern Sierra Nevada of California

Abstract. Extreme droughts are a major determinant of ecosystem disturbance that impacts plant communities and feeds back into climate change through changes in plant functioning. However, the complex relationships between aboveground and belowground plant hydraulic traits and their role in governing plant responses to drought are not fully understood. In this study, we use a model, the Functionally Assembled Terrestrial Ecosystem Simulator in a configuration that includes plant hydraulics (FATES-Hydro), to investigate ecosystem responses to the 2012–2015 California drought in comparison with observations at a site in the southern Sierra Nevada that experienced widespread tree mortality during this drought. We conduct a sensitivity analysis to explore how different plant water sourcing and hydraulic strategies lead to differential responses during normal and drought conditions. The analysis shows the following. Deep roots that sustain productivity through the dry season are needed for the model to capture observed seasonal cycles of evapotranspiration (ET) and gross primary productivity (GPP) in normal years, and deep-rooted strategies are nonetheless subject to large reductions in ET and GPP when the deep soil reservoir is depleted during extreme droughts, in agreement with observations. Risky stomatal strategies lead to greater productivity during normal years as compared to safer stomatal control, but they also lead to a high risk of xylem embolism during the 2012–2015 drought. For a given stand density, stomatal and xylem traits have a stronger impact on plant water status than on ecosystem-level fluxes. Our study highlights the significance of resolving plant water sourcing strategies to represent drought impacts on plants and consequent feedbacks in models.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1971

Contributions to Astrogeology: Geology of the lunar crater volcanic field, Nye County, Nevada

The Lunar Crater volcanic field in east-central Nevada includes cinder cones, maars, and basalt flows of probably Quaternary age that individually and as a group resemble some features on the moon. Three episodes of volcanism are separated by intervals of relative dormancy and erosion. Changes in morphology of cinder cones, degree of weathering, and superposition of associated basalt flows provide a basis for determining the relative ages of the cones. A method has been devised whereby cone heights, base radii, and angles of slope are used to determine semiquantitatively the age relationships of some cinder cones. Structural studies show that cone and crater chains and their associated lava flows developed along fissures and normal faults produced by tensional stress. The petrography of the basalts and pyroclastics suggests magmatic differentiation at depth which produced interbedded subalkaline basalts, alkali-olivine basalts, and basanitoids. The youngest flows in the field are basanitoids.

Scott, D. H.↗
NASA NTRS1972

A reconnaissance space sensing investigation of the crustal structure for a strip from the eastern Sierra Nevada to the Colorado Plateau: April 1971

The author has identified the following significant results. An area of anomalous linear topographic grain and color expressions was recognized in Apollo 9 and ERTS-1 imagery along the Colorado River of northwestern Arizona and southern Nevada. Field reconnaissance and analysis of U-2 photography has shown the anomaly to be a zone of north to north-northwest trending dike swarms and associated granitic plutons. The dikes vary in composition from rhyolite to diabase, with an average composition nearer rhyolite. Shearing and displacement of host rocks along dikes suggest dike emplacement along active fault zones. Post-dike deformation has resulted in shearing and complex normal faulting along a similar north-south trend. The epizonal plutonism and volcanism of this north-south belt appears to represent a structurally controlled volcanogenic province which ends abruptly in the vicinity of Lake Mead at a probable eastern extension of the Las Vegas Shear Zone. The magnitude and chronology of extensional faulting and plutonism recognized in the north-south zone, support the hypothesis that the Las Vegas Shear Zone is a transform fault separating two areas of crustal spreading.

Bechtold, I. C.↗
NASA NTRS1971

Remote sensing evaluation of the Klondike Mining District, Nevada. Part 1: Geology, photography and infrared

During August of 1970 Mission 140 was flown with the NASA P3A aircraft over the Klondike Mining District, Nevada. High quality metric photography, thermal infrared imagery, multispectral photography and multichannel microwave radiometry were obtained. Geology and ground truth data are presented and relationships of the physical attributes of geologic materials to remotely sensed data is discussed. It is concluded that remote sensing data was valuable in the geologic evaluation of the Klondike Mining District and would be of value in other mining districts.

Brennan, P. A.↗
NASA NTRS1973

Remote sensing reconnaissance of faulting in alluvium, Lake Mead to Lake Havasu, California, Nevada and Arizona. An application of ERTS-1 satellite imagery

The author has identified the following significant results. Analysis of ERTS-1 MSS and other imagery for a 125 x 25 mile area in the southern part of the Basin-Range Province of southeastern California, southern Nevada, and northwestern Arizona indicates the presence of numerous color and contrast anomalies in alluvium. Field work guided by high altitude U-2 and side-looking aerial radar imagery confirmed that these anomalies are fault zones, many of which are believed to be of recent age. Few faults in alluvium have been reported from previous ground based geologic studies in the area. ERTS-1 imagery provides a synoptic perspective previously unavailable for regional geologic studies. The ability to conduct rapid and inexpensive reconnaissance of recent faulting has important applications to land use planning, ground water exploration, geologic hazards, and the siting and design of engineering projects.

Bechtold, I. C.↗
NASA NTRS1973

Mineral exploration and fracture trends in Utah and Nevada, by ERTS-1 imagery

The author has identified the following significant results. Major structural trends have been compiled on five separate maps, at a scale of 1:1,000,000, of Utah and Nevada from ERTS-1 imagery. An arbitrary length of ten kilometers has been chosen as a minimum length of the trends. The selection is based upon: (1) obvious displacement of structures; (2) continuity or persistence of trends across structures; (3) line-up of outcrop patterns, drainage, erosional features or vegetation; and (4) near-linear trends. Several recognizable trend directions have noted, viz., N 10-15 deg W, N 35 deg W, N 80 deg W, N 30 deg E, and E-W. More than 1500 structural trends have been identified, some of which are mineralized and extend into pediment or shallow alluvial cover. Those fracture trends that exhibit mineralization in exposed bedrock will be assayed for mercury content with a soil-gas analyzer and similar collection will be done over alluvial posture blankets by the same technique with the hope of discovering blind mineralized zones that are not exposed on the surface.

Jensen, M. L.↗
NASA NTRS1973

Evidence of a major fault zone along the California-Nevada state line 35 deg 30 min to 36 deg 30 min north latitude

The author has identified the following significant results. Geologic reconnaissance guided by analysis of ERTS-1 and Apollo-9 satellite imagery and intermediate scale photography from X-15 and U-2 aircraft has confirmed the presence of a major fault zone along the California-Nevada state line, between 35 deg 30 min and 36 deg 30 min north latitude. The name Pahrump Fault Zone has been suggested for this feature after the valley in which it is best exposed. Field reconnaissance has indicated the existence of previously unreported faults cutting bedrock along range fronts, and displacing Tertiary and Quaternary basin sediments. Gravity data support the interpretation of regional structural discontinuity along this zone. Individual fault traces within the Pahrump Fault Zone form generally left-stepping en echelon patterns. These fault patterns, the apparent offset of a Laramide age thrust fault, and possible drag folding along a major fault break suggest a component of right lateral displacement. The trend and postulated movement of the Pahrump Fault Zone are similar to the adjacent Las Vegas Shear Zone and Death Valley-Furnace Creek Faults, which are parts of a regional strike slip system in the southern Basin-Range Province.

Liggett, M. A.↗
NASA NTRS1973

Application of ERTS-1 imagery and underflight photography in the detection and monitoring of forest insect infestations in the Sierra Nevada Mountains of California

The analysis of ERTS-1 imagery of areas in the Sierra Nevada Mountains of California is discussed. The data is used to detect two types of insect infestational and to determine the extent of timber resources. Addition applications are the mapping of stream courses, mountain meadows, lakes, rock outcrops, and grazing land. The ERTS-1 data and underflight photography are used for this purpose.

Hall, R. C.↗
NASA NTRS1973

Geology of Utah and Nevada by ERTS-1 imagery

Repetitive ERTS-1 imagery covering Utah and Nevada is studied as an aid in structural geology, mineral exploration, and limnological and hydrological aspects. Limnological features of algal blooms and varying biological activities in Utah Lake and the Great Salt Lake are grossly evident on the imagery with more subtle details detected on the different bands. Major structural breaks, lineages, or trends are abundant throughout the area of study. The correlation of positive aeromagnetic anomalies with the trends suggests near surface intrusive bodies, not yet exposed at the surface, that can be tested for possible associated mineralization by collecting soil-gas at the surface which is analyzed for mercury that is (1) apparently associated with mineralization, (2) escapes as a vapor, and (3) can be readily measured in extremely low amounts of less than 1 ppb by absorption.

Jensen, M. L.↗
NASA NTRS1973

Fracture trends identified by ERTS-1 imagery in Utah and Nevada

The author has identified the following significant results. In the Utah-Nevada area, linear structural trends recorded on ERTS-1 imagery conform in part to previously recognized structures. In addition, the ERTS-1 imagery reveals cryptic structures not previously identified and not readily apparent in other imagery. These structures are illustrated by prominent east-west trending structures which appear to be concentrated in pre-volcanic rocks. This suggests that the structures are older than many of those with other trends which are equally prominent in volcanic and non-volcanic terrain. Since the older east-west structures may have controlled early Tertiary emplacement of magma or the ascent of mineralizing fluids, their recognition is important in minerial exploration. Soil-gas sampling and analysis for mercury content is being continued over structures, and projected trends of buried structures which appear, from studies of ERTS-1 imagery, to be favorable to mineralization. Comparison of ERTS-1 and Skylab imagery indicated that ERTS-1 imagery records more previously unrecognized linear structures than the Skylab imagery. In differentiating and identifying different rock types, the Skylab imagery appears to be more effective.

Jensen, M. L.↗
NASA NTRS1973

A reconnaissance space sensing investigation of crustal structure for a strip from the eastern Sierra Nevada to the Colorado Plateau

The author has identified the following significant results. An operational technique for producing high resolution false color composites of ERTS-1 MSS imagery has been developed. The technique uses standard NASA (NDPF) or EROS black/white data products, and permits a broad range of control on composite color balance and contrast range. The use of an additive color viewer has proven valuable for determining the optimum color balance of composites for effective interpretation. The compositing technique is adaptable for effective interpretation. The technique is adaptable to data from a variety of multispectral imaging systems, including multi-seasonal and multipolarization data. A 50 mile north-trending linear anomaly recognized in ERTS-1 MSS imagery west of Goldfield, Nevada has been confirmed as a steeply west-dipping normal fault, here termed the Paymaster Fault. This structure trends southward from the General Thomas Hills along Paymaster Valley and the east side of Clayton Valley into the Palmetto Mountains. There, it terminates against a less pronounced east-trending transverse anomaly which is also believed to be fault controlled. The Paymaster Fault is the most prominent of several large normal faults which terminate southward against this transverse anomaly.

Liggett, M. A.↗