Variation In Vegetation Density Research Articles

Hydraulic Resistance by the River Red Gum, Eucalyptus camaldulensis, in Ephemeral Desert Streams

Channel roughness in desert streams is generated by the colonisation of beds and banks by trees including the river red gum, Eucalyptus carnaldulensis. Often growing densely over the bed surface, these trees contribute channel roughness which is distributed through the flow; the effects are heightened by substantial barriers of flood‐transported debris which lodge against trunks and branches, offering additional obstruction to water movement. Bed scour often occurs around such obstacles.Field mapping of channels in the Barrier Range, western NSW, where E. camaldulensis growth is common, has permitted the quantification of channel roughness. Results suggest that just under half of the total channel roughness may be contributed by in‐channel vegetation, the remainder coming from boundary friction effects. Site‐to‐site variations in vegetation density are great and assessment of flood discharges and sediment fluxes in these streams without due incorporation of a roughness correction could result in substantial errors of overprediction.

Variation in vegetation density and foredune complexity at North Padre Island, Texas : Blum, Micheal and J.R. Jones, 1985. Tex. J. Sci., 37(1): 63–73. Dept. of Geography, The Univ. of Texas at Austin, Austin, TX 78712, USA

Variation in vegetation density and foredune complexity at North Padre Island, Texas : Blum, Micheal and J.R. Jones, 1985. Tex. J. Sci., 37(1): 63–73. Dept. of Geography, The Univ. of Texas at Austin, Austin, TX 78712, USA

Estimation of the vegetation contribution to the 1·65/2·22 μm ratio in airborne thematic-mapper imagery of the Virginia Range, Nevada

Abstract Previous investigations have successfully used the 1·65/2·22μm ratio to map the concentration of hydroxyl-bearing minerals in imagery of sparsely vegetated terrain. However, difficulties arise in applying this ratio to semiarid regions where there is a wide variation in vegetation density. Besides mapping the mineralogic features of interest, the 1·65/2·22μm ratio also maps the density of vegetation by responding to leaf water content. A technique has been developed to estimate the vegetation contribution to this ratio based on the near-IR/red ratio. The technique has proved useful in mapping supergene alteration in the Virginia Range, Nevada

Monitoring roadside lead deposition by sampling vegetation — Some problems of interpretation

Analysis of samples of roadside vegetation has often been used as a means of investigating the pattern of lead deposition in relation to such factors as traffic density. Longer term monitoring presents a number of difficulties: differing Pb retention capacities of different kinds of plant material, seasonal and spatial variation in vegetation density, height, live/dead ratio and longevity. Seasonal variation of deposition rates and possibly deposition routes are apparently superimposed on these variables. The problems of interpretation are discussed in the light of experience of a 3-year sampling programme.

Soil Moisture Patterns on Two Chained Pinyon-Juniper Sites in Utah

Highlight: Soil moisture patterns were studied under chaining-with-windrowing, chaining-with-debris-in-place, and natural woodland at one site each in both southwestern and southeastern Utah. Results of the study indicate the greatest moisture accumulation occurred under the debris-in-place treatment (as compared to woodland controls), during the first 6 months of each year at Milford and regardless of season at Blanding. The woodland had the least soil moisture throughout most of each year. Most moisture flux took place in the upper 60to 90-cm of soil profile, with only minor changes occurring at greater depths. Differences in soil moisture patterns have been attributed to changes in microclimates due to chaining, different rooting depths and length of growing season, mulching effect of litter on the debris-in-place treatment, and possible differences in snow accumulation. Variation in vegetation density on the chained treatments did not influence soil moisture patterns. There was no evidence of deep seepage on any chaining treatment at either site.