@article {51014, title = {Nutrient resorption in shrubs growing by design and by default in Chihuahuan Desert arroyos}, journal = {Oecologia}, volume = {128}, number = {3}, year = {2001}, month = {August 1, 2001}, pages = {351-359}, abstract = {

In the northern stretches of the Chihuahuan Desert, the margins of ephemeral stream channels called arroyos support a unique vegetation dominated by a guild of winter-deciduous shrubs. To explore the dynamics of nutrient conservation in this assemblage of arroyo shrubs, we measured nitrogen (N) and phosphorus (P) resorption efficiency and proficiency in six species of shrubs growing in arroyos in southern New Mexico, USA. Collectively, these six species were no more efficient or proficient at resorbing N and P from senescing leaves than shrubs growing in other environments. Resorption efficiency averaged 53\% and 50\% for N and P, respectively, and resorption proficiency averaged 0.80\% and 0.06\% for N and P, respectively. However, resorption varied significantly between species specifically restricted in their distribution to riparian habitats (obligate riparian species) and those that were not. The two obligate riparian species combined (Brickellia laciniata, Chilopsis linearis) were significantly more efficient and proficient at resorbing N than the non-obligate riparian species combined (Fallugia paradoxa, Flourensia cernua, Prosopis glandulosa, Rhus microphylla). Additionally, both Brickellia and Chilopsis were individually significantly more proficient at resorbing N than any of the other four species. The dichotomy in resorption between obligate riparian species and those that were not may have been the result of the interplay between hydrology, geomorphology, and biology. Because arroyos move in space as the movement of water erodes banks and changes channel location, some plants are found along arroyos only because the arroyos have moved to them. These plants (plants growing by default) may be less well adapted to arroyo margins than obligate riparian species (plants growing by design). Significant differences in resorption between obligate and nonobligate riparian species suggested that evolutionary history and habitat specificity may be added to the list of factors known to influence resorption. Selected life history traits of the six species did not appear to be related to any measure of resorption, but leaf surface area, specific leaf mass, and nutrient concentrations in green leaves were all correlated with resorption efficiency or proficiency in one or more species. The only species capable of symbiotic N fixation, Prosopis glandulosa, retained at least 2.3 times more N in its senesced leaves than any other species. Patterns of resorption in arroyo shrubs strongly indicated that efficiency and proficiency are fundamentally different, complementary measures of resorption.

}, doi = {10.1007/s004420100668}, url = {/files/bibliography/01-056.pdf}, author = {K.T. Killingbeck and Walter G. Whitford} } @article {51354, title = {High foliar nitrogen in desert shrubs: An important ecosystem trait or defective desert doctrine?}, journal = {Ecology}, volume = {77}, year = {1996}, month = {1996}, pages = {1728-1737}, abstract = {

Nitrogen concentrations in green and senesced leaves of perennial desert shrubs were compiled from a worldwide literature search to test the validity of the doctrine that desert shrubs produce foliage and leaf litter much richer in nitrogen than that in the foliage of plants from more mesic environments. Mean nitrogen concentration in the green leaves of 78 species of shrubs growing in 11 deserts on five continents (2.2\%) was not different from that in 67 species of trees and shrubs growing in deciduous, and mixed deciduous forests (2.2\%), and only slightly higher than that in overstory (2.0\%) and understory (2.1\%) plants growing in tropical wet forest. Mean nitrogen concentration in the green leaves of a ubiquitous shrub that dominates large areas of desert in the United States (Larrea tridentata, 2.1\%), and in the green{\textemdash}stem tissues of leafless desert shrubs (2.1\%) were also similar to that in plants from mesic environments. Mean green{\textemdash}leaf nitrogen was similar in shrubs growing in different deserts. Mean nitrogen concentration in leaf litter was 1.1\% for 11 species of desert shrubs, and 1.0\% for the 10 species of this group that were not capable of symbiotic nitrogen fixation. Both concentrations were lower than those routinely provided to describe nitrogen in the litter of desert shrubs (1.5{\textemdash}1.7\%), and only slightly higher than the mean nitrogen concentration in 77 species of woody perennials growing in a wide variety of environments worldwide (0.9\%). Nitrogen in the leaf litter of one desert shrub (0.4\%, Brickellia laciniata) was nearly as low as the lowest leaf{\textemdash}litter nitrogen concentration known for any woody species (0.3\%). Because nitrogen concentrations in the foliage of desert shrubs are not higher than those in plants growing in more mesic environments, the tenet that desert shrubs support extraordinarily nitrogen{\textemdash}rich foliage can no longer be supported.

}, keywords = {desert shrubs, ecosystem traits, green leaves, leaf litter, nitrogen in desert shrubs, nutrient cycling}, doi = {10.2307/2265778 }, url = {/files/bibliography/495.pdf}, author = {K.T. Killingbeck and Walter G. Whitford} } @proceedings {51355, title = {Tracking environmental change with the desert shrub ocotillo (Fouquiera splendens): Prospects and pitfalls}, volume = {Gen. Tech. Rep. INT-GTR-338}, year = {1996}, note = {//LOCAL,NMSU//NONE//ProCite field[6]: InProCite field[8]: Compilers}, month = {May 23-25, 1995}, pages = {224-229}, publisher = {U.S. Department of Agriculture, Forest Service, Intermountain Research Station}, address = {Las Cruces, NM}, abstract = {Ocotillo is a drought-deciduous desert shrub capable of orchestrating rapid morphological and physiological adjustments to changes in environmental conditions. Lengths of over 2,500 stem segments from two populations of ocotillo growing in the Chihuahuan Desert were measured to explore the possibility that episodes of stem growth could be used to infer past environmental change. Stem growth was so intermittent and complex that historical projections of environmental conditions were not possible without first establishing benchmark stem segments. Once established though, benchmark stem segments and subsequent stem growth may be used as easily measurable integrators of ongoing environmental change in desert ecosystems.}, keywords = {abstract, abstracts, conference, conference proceedings, conferences, Fouquieria, environmental change, ocotillo, SEE , plant, environmental change, proceeding, proceedings, technique, environmental change, technique, Fouquieria}, author = {K.T. Killingbeck}, editor = {J.R. Barrow and McArthur, E.D. and R. E. Sosebee and R. J. Tausch} } @article {51536, title = {Inefficient nitrogen resorption in a population of ocotillo (Fouquieria splendens), a drought deciduous desert shrub}, journal = {Southwestern Naturalist}, volume = {37}, year = {1992}, note = {//NMSU//LTER II//Listed in LTER3 proposal as citing LTER2 support//}, month = {1992}, pages = {35-42}, abstract = {Ocotillo is a drought-deciduous desert shrub capable of orchestrating rapid morphological and physiological adjustments to changes in environmental conditions. Lengths of over 2,500 stem segments from two populations of ocotillo growing in the Chihuahuan Desert were measured to explore the possibility that episodes of stem growth could be used to infer past environmental change. Stem growth was so intermittent and complex that historical projections of environmental conditions were not possible without first establishing benchmark stem segments. Once established though, benchmark stem segments and subsequent stem growth may be used as easily measurable integrators of ongoing environmental change in desert ecosystems.}, keywords = {article, articles, Fouguieria,nitrogen, journal, journals, nitrogen,Fouquieria, plant,Fouquieria, plant,ocotillo, Fouquieria}, author = {K.T. Killingbeck} }