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1 A 3-year field study examined the physiological and demographic consequences of resource pulse use by an herbaceous, aridland perennial, Cryptantha flava, as well as potential competitive and facilitative interactions with larger shrubs. 2 We applied a pulse of urea and faecal pellets, simulating Mule deer excretions, to plants growing between and under Sagebrush and Rabbitbrush canopies. 3 We hypothesized that C. flava would show strong positive responses to N pulses in open microhabitats, and such plants had approximately 50% increases in leaf N concentrations within days of pulse application, accompanied by increased photosynthetic rates. Over the next year, higher rates of growth and reproduction were found...
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Juniper species are noted for long-lived foliage, low and persistent gas exchange activity and drought tolerance. Because leaves and roots of the same species are thought to be similar in structure and life history, we hypothesized that Juniperus osteosperma (Torr.) Little (Utah juniper) fine roots would reflect the persistent aboveground foliage characteristic of this species. We monitored fine roots, less than 1 mm in diameter, by minirhizotron imaging to a depth of 150 cm over two growing seasons from April 2002 to December 2003. We measured fine root numbers, lengths and diameters, and noted the time of birth and death of root segments. We correlated our root data with soil water potential measured by thermocouple...
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1 Resource pulses generally result in a burst of biological activity at multiple scales. For plants, the increased activity is generally considered positive due to an overall up-regulation of physiological activity during the pulse. Longer-term effects remain an understudied aspect of resource pulses. 2 We monitored the short- and long-term effects of nitrogen (N) pulse to the long-lived desert perennial, Cryptantha flava. One group of plants were treated with a one-time application of N in the spring of 1999, a second group received two N pulses (one in the spring of 1999 and one in the spring of 2000), and a third group received ambient N (controls). 3 In the short-term, N-pulse treated plants rapidly increased...
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Water conservation is important for plants that maintain physiologically active foliage during prolonged periods of drought. A variety of mechanisms for water conservation exist including stomatal regulation, foliage loss, above- and below-ground allocation patterns, size of xylem vessels and leaf pubescence. Using the results of a field and simulation study with Artemisia tridentata in the Great Basin, USA, we propose an additional mechanism of water conservation that can be used by plants in arid and semi-arid environments following pulses of water availability. Precipitation redistributed more uniformly in the soil column by roots (hydraulic redistribution of water downward) slows the rate at which this water...
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