Fluridone {1-methyl-3-phenyl-5-[3-(trifluromethyl)phenyl]-4(1H)-pyridinone} and norflurazon [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone] inhibited carotenoid synthesis in wheat(Triticum aestivumL. ‘Maricopa’) seedlings and caused the accumulation of colorless carotenoid precursors, phytoene, and phytofluene. These data suggested that dehydrogenation reactions following phytoene formation were inhibited by the herbicides. Chlorophyll accumulated in the treated seedlings grown under 10 lux of light but was destroyed in seedlings illuminated with 16 klux of light. Seedlings illuminated with 16 klux of light lacked chloroplast ribosomes and normal ultrastructure whereas dark grown seedlings contained pastid ribosomes and had normal etioplast ultrastructure. The disruption of the chloroplasts and loss of chlorophyll was due to the absence of carotenoids in the treated plants, which would normally act to protect the chloroplasts from photodestruction.

We surveyed a group of rangeland managers in the Southwest about vegetation monitoring needs on grassland. Based on their responses, the objective of the RANGES (Rangeland Analysis Utilizing Geospatial Information Science) project was defined to be the accurate conversion of remotely sensed data (satellite imagery) to quantitative estimates of total (green and senescent) standing cover and biomass on grasslands and semidesert grasslands. Although remote sensing has been used to estimate green vegetation cover, in arid grasslands herbaceous vegetation is senescent much of the year and is not detected by current remote sensing techniques. We developed a ground truth protocol compatible with both range management requirements and Landsat’s 30 m resolution imagery. The resulting ground-truth data were then used to develop image processing algorithms that quantified total herbaceous vegetation cover, height, and biomass. Cover was calculated based on a newly developed Soil Adjusted Total Vegetation Index (SATVI), and height and biomass were estimated based on reflectance in the near infrared (NIR) band. Comparison of the remotely sensed estimates with independent ground measurements produced r2 values of 0.80, 0.85, and 0.77 and Nash Sutcliffe values of 0.78, 0.70, and 0.77 for the cover, plant height, and biomass, respectively. The approach for estimating plant height and biomass did not work for sites where forbs comprised more than 30% of total vegetative cover. The ground reconnaissance protocol and image processing techniques together offer land managers accurate and timely methods for monitoring extensive grasslands. The time-consuming requirement to collect concurrent data in the field for each image implies a need to share the high fixed costs of processing an image across multiple users to reduce the costs for individual rangeland managers.

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23 24 B. A. Roundy et al. limited nature of summer rainfall on abandoned farmland in the lower Sonoran Desert.

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