Jay S. Noller

Application of Remote-sensing Data and Decision-Tree Analysis to Mapping Salt-Affected Soils over Large Areas

Expert assessments for crop and range productivity of very-large arid and semiarid areas worldwide are ever more in demand and these studies require greater sensitivity in delineating the different grades or levels of soil salinity. In conjunction with field study in arid southeastern Oregon, we assess the merit of adding decision-tree analysis (DTA) to a commonly used remote-sensing method. Randomly sampled surface soil horizons were analyzed for saturation percentage, field capacity, pH and electrical conductivity (EC). IFSAR data were acquired for terrain analysis and surficial geological mapping, followed by derivation of layers for analysis. Significant correlation was found between EC values and surface elevation, bands 1, 2, 3 and 4 of the Landsat TM image, and brightness and wetness indices. Maximum-likelihood supervised classification of the Landsat images yields two salinity classes: non-saline soils (EC < 4 dSm–1), prediction accuracy of 97%, and saline soils (EC < 4 dSm–1), prediction accuracy 60%. Addition of DTA results in successful prediction of five classes of soil salinity and an overall accuracy of about 99%. Moreover, the calculated area of salt-affected soil was overestimated when mapped using remote sensing data only compared to that predicted by additionally using DTA. DTA is a promising approach for mapping soil salinity in more productive and accurate ways compared to only using remote-sensing analysis.

New light on Aetokremnos

Abstract The note reconsiders the environmental setting of Aetokremnos, the controversial site of pre-Neolithic age on the island of Cyprus. Some 12,000 years ago when the sea level was lower, the site was not situated right on the coast in an island-like context as its excavators have claimed. Instead, it was located near the top of a tall cliff at the back of a wide coastal plain. At the time there were, in addition, actively forming dune fields just in front of the site. The discussion draws attention to three ambiguities in the previous interpretation of Aetokremnos and proposes that a new series of radiocarbon dates should be run on samples of bone in order to clarify the situation at the site.

Rillenkarren at Vayia: geomorphology and a new class of Early Bronze Age fortified settlement in Southern Greece

With ever more inhibited programmes of excavation, new methods of site survey are always welcome. Here a soil geomorphologist joins forces with archaeologists to read the history of limestone blocks exposed on the surface at sites in southern Greece. Rillenkarren for example are vertical grooves caused by rainfall on stones that remained for long periods in the same place. These and other observations showed that what looked like clearance cairns had in fact been piled up in the Early Bronze Age and led in turn to the definition of a new type of settlement.

Effects of surface and subsurface water application on nitrogen and sodium relations of desert graminoids of different geographic origin

ABSTRACT This greenhouse study evaluated nitrogen and sodium relations of three desert graminoids (Distichlis spicata, Leymus triticoides, and Juncus arcticus) as affected by availability of surface water, subsurface water or both. These species are amply distributed in desert wetlands of western USA where surface and subsurface water are differentially available. Plants of the three species were collected from two areas of ecological distribution: Bishop, California and Burns, Oregon. Because nitrogen and sodium uptake by plants is highly linked to water availability we established three general hypotheses for this study: (1) nitrogen uptake would be greater when plants have surface water available, (2) sodium uptake would be greater when plants do not have surface water available, and (3) there are populations’ differences in the response of the species to water availability. We grew plants in two-layer pots in which soil water content in the upper and lower layers was controlled independently. The first hypothesis was partially supported as only Leymus triticoides seemed to preferentially depend on the top layer for nitrogen acquisition. With respect to the second hypothesis sodium concentration was indeed greatest when plants had no surface water, but only in D. spicata. The third hypothesis was also partially supported. The Oregon population of J. arcticus had 15% more nitrogen than the California population and the California population of D. spicata had 18% more sodium than the Oregon population. Our results underline the plant nutrient uptake implications of differential availability of water pools for common desert graminoid species.

Patterns of Water Use by Great Basin Plant Species Under Summer Watering

We analyzed temporal and spatial patterns of water use by a functionally-diverse group of Great Basin plant species and determined their water use rates at the whole-plant and individual-leaf scales under variable summer watering. Species studied were the desert grasses Distichlis spicata and Sporobolus airoides, the desert shrubs Artemisia tridentata, Ericameria nauseosa, and Atriplex confertifolia; the wetland/riparian plants Juncus arcticus, Leymus triticoides, and Salix exigua; and the annual exotic Salsola tragus. Plant species were individually grown in 5.8 m2 plots in a common garden in eastern California. Three irrigation treatments in the form of monthly pulses were applied during the summer: low (1.3 cm), medium (2.6 cm), and high (3.9 cm), in addition to a nonirrigated control. Whole-plant water uptake characteristics were determined by soil water depletion at different soil depths, while leaf transpiration was determined by gas exchange. Whole-plant water extraction and leaf transpiration varied similarly among species. Desert shrubs had low water extraction (35 to 395 g m−2 day−1) and were not affected by irrigation. The desert grasses and riparian/wetland species had higher water extraction, increasing with irrigation levels. L. triticoides and J. arcticus had the highest water extraction overall (>2,000 g m−2 day−1). Desert shrubs relied 10 times more on deeper water sources than herbaceous species. The average T/ET was 31%, but varied by species. Summer available water in environments such as the Great Basin favors desert grasses and riparian/wetland species, but not desert shrubs. The observed species differences provide alternatives for water and vegetation management.

Applying Geochronology in Predictive Digital Mapping of Soils

Explicitly adding time (geochronology) to the rubric of digital soil mapping enhances the results and accuracy of predictive maps for initial and update soil surveys. Experiments were performed on a data set used in the prediction of soils in the initial Malheur County soil survey, Oregon. Geochronological information was derived from (1) independently compiled Quaternary geological maps, (2) age point data, and (3) remotely sensed data. These data were incorporated in decision-tree analysis as area-class data in raster format. Experimental area consists largely of fluvial, lacustrine and/or volcanic materials and landforms. Expert soil survey maps are used as reference in making predictions with and without implicit or explicit age information. Addition of geochronological data produces predictive maps that are most closely aligned with expert maps. Improvements afforded by predictive soils mapping may be of greater magnitude in areas where the age stratification of the landscape is not obvious to the soil surveyor. Layers representing palaeogeographical changes in surficial processes and palaeoclimatological events may provide further enhancements.

Consequences of Surface and Subsurface Water Use on Wetland Graminoids of Different Geographic Origin

We evaluated growth and physiology of three wetland graminoids (Distichlis spicata, Leymus triticoides, and Juncus arcticus) as affected by surface and subsurface water. These species are common in western USA and were collected from two areas: Bishop, California and Burns, Oregon. Our hypotheses were: 1) the use of surface water by plants is higher than the use of subsurface water and 2) there are population differences in the response of the species to available water. The species of study were grown in two-layer pots with soil water content in the upper and lower layers independently controlled. The first hypothesis was partially supported by our results, but variability existed among species. However, when all species had equal access to both surface soil water and subsurface water plants tended to preferentially use surface water. We also found that J. arcticus can display reverse hydraulic lift when growing with no subsurface water. The second hypothesis was clearly supported by results. Although the mechanism is not clear, it is possible that an area with periodic and predictable shallow groundwater underlying a dry or saline soil layer, such as the California site, might favor plant populations with high proficiency in water uptake by deeper roots.