Early taproot development of a xeric shrub (Larrea tridentata) is optimized within a narrow range of soil moisture

Effects of watering amount and frequency on root biomass accumulation and taproot elongation were examined 16–17 days post-germination in seedlings of Larrea tridentata, a dominant shrub in North American hot deserts. Two experimental variables manipulated in a full factorial design greenhouse study were (i) number of “triggering” days: consecutive days (2, 3, 4 or 5) at the start of the experiment on which seedlings received 10 mm of water per day; and (ii) “post-trigger” watering frequency: 5 mm of water either daily or every other day. We hypothesized that taproot elongation would increase with greater numbers of triggering days, whereas higher post-trigger watering frequency would enhance root biomass development. Increasing the number of triggering days from two to four promoted taproot extension without affecting root biomass, and higher watering frequency in the post-trigger phase generally increased root biomass, as expected. Contrary to expectations, root biomass and taproot length were significantly reduced when daily watering followed five consecutive triggering days. Taproot length correlated with root biomass, but irrigation regime also had a biomass-independent effect: with either two or five triggering days, taproots were shorter than expected based on root biomass. Thus, both too little and too much water stymied taproot extension. In natural settings, the adverse response of taproots to too little or too much water could reduce seedling survivorship and restrict establishment to a narrow range of environmental conditions.

[1]  F. Went,et al.  Ecology of Desert Plants. III. Development of Plants in the Death Valley National Monument, California , 1949 .

[2]  M. Barbour.  Germiantion Requirements of the Desert Shrub Larrea Divaricata , 1968 .

[3]  M. Barbour.  Age and Space Distribution of the Desert Shrub Larrea Div Aricata , 1969 .

[4]  D. Janzen.  Herbivores and the Number of Tree Species in Tropical Forests , 1970, The American Naturalist.

[5]  J. Hunziker,et al.  Species Disjunctions in Larrea: Evidence From Morphology, Cytogenetics, Phenolic Compounds, and Seed Albumins , 1972 .

[6]  I. Noy-Meir,et al.  Desert Ecosystems: Environment and Producers , 1973 .

[7]  J. Letey,et al.  Oxygen Requirements for Root Growth in Three Species of Desert Shrubs , 1973 .

[8]  J. C. Beatley.  Effects of Rainfall and Temperature on the Distribution and Behavior of Larrea Tridentata (Creosote‐Bush) in the Mojave Desert of Nevada , 1974 .

[9]  J. C. Beatley.  Phenological Events and Their Environmental Triggers in Mojave Desert Ecosystems , 1974 .

[10]  M. Barbour,et al.  Contributions to the Biology of Larrea Species , 1974 .

[11]  O. Reichman.  Relationships between Dimensions, Weights, Volumes, and Calories of Some Sonoran Desert Seeds , 1976 .

[12]  P. Grubb.  THE MAINTENANCE OF SPECIES‐RICHNESS IN PLANT COMMUNITIES: THE IMPORTANCE OF THE REGENERATION NICHE , 1977 .

[13]  W. Oechel,et al.  Growth and Development Form and Function , 1977 .

[14]  J. Connell.  Diversity in tropical rain forests and coral reefs. , 1978, Science.

[15]  Tom J. Mabry,et al.  Creosote bush. Biology and chemistry of Larrea in New World deserts. , 1978 .

[16]  A. Pitty.  Geography and Soil Properties , 1979 .

[17]  T. L. Ackerman.  Germination and Survival of Perennial Plant Species in the Mojave Desert , 1979 .

[18]  S. Thien.  A flow diagram for teaching texture‐by‐feel analysis , 1979 .

[19]  F. C. Vasek.  CREOSOTE BUSH: LONG‐LIVED CLONES IN THE MOJAVE DESERT , 1980 .

[20]  D. Phillips,et al.  Competition and spacing patterns in desert shrubs , 1981 .

[21]  S. P. Mclaughlin,et al.  Effects of Wildfire on A Sonoran Desert Plant Community , 1982 .

[22]  GROWTH RATES AND ROOT: SHOOT RATIOS IN SEEDLINGS OF THE DESERT SHRUB LARREA TRIDENTA TA. , 1983 .

[23]  O. Reichman.  Spatial and temporal variation of seed distributions in Sonoran Desert soils , 1984 .

[24]  R. Minnich,et al.  Fire and Changes in Creosote Bush Scrub of the Western Sonoran Desert, California , 1986 .

[25]  D. Goldberg,et al.  Vegetation Change and Plant Demography in Permanent Plots in the Sonoran Desert , 1986 .

[26]  T. V. Madsen.  INTERACTIONS BETWEEN INTERNAL AND EXTERNAL CO2 POOLS IN THE PHOTOSYNTHESIS OF THE AQUATIC CAM PLANTS LITTORELLA UNIFLORA (L.) ASCHERS AND ISOETES LACUSTRIS L. , 1987 .

[27]  L. Boddy,et al.  Water, fungi, and plants , 1987 .

[28]  J. McAuliffe.  Markovian Dynamics of Simple and Complex Desert Plant Communities , 1988, The American Naturalist.

[29]  T. Howell,et al.  Management of Farm Irrigation Systems , 1990 .

[30]  R. E. Sojka,et al.  Soil Management (Chapter 23) , 1991 .

[31]  J. Dobrowolski,et al.  Dynamics of shrub die-off in a salt desert plant community. , 1992 .

[32]  R. Callaway,et al.  Root Communication Mechanisms and Intracommunity Distributions of Two Mojave Desert Shrubs , 1992 .

[33]  J. McAuliffe.  Landscape Evolution, Soil Formation, and Ecological Patterns and Processes in Sonoran Desert Bajadas , 1994 .

[34]  C. E. Pake,et al.  Is Coexistence of Sonoran Desert Annuals Mediated by Temporal Variability Reproductive Success , 1995 .

[35]  M. McClaran,et al.  The Desert Grassland , 1995 .

[36]  C. E. Pake,et al.  Seed Banks in Desert Annuals: Implications for Persistence and Coexistence in Variable Environments , 1996 .

[37]  J. Sperry,et al.  Freezing-induced xylem cavitation and the northern limit of Larrea tridentata , 1996, Oecologia.

[38]  P. Chesson,et al.  The Roles of Harsh and Fluctuating Conditions in the Dynamics of Ecological Communities , 1997, The American Naturalist.

[39]  W. G. Spaulding,et al.  Ploidy race distributions since the Last Glacial Maximum in the North American desert shrub, Larrea tridentata , 2002 .

[40]  W. Horwath,et al.  Acid fumigation of soils to remove carbonates prior to total organic carbon or CARBON‐13 isotopic analysis , 2001 .

[41]  M. Westoby,et al.  What do seedlings die from and what are the implications for evolution of seed size , 2004 .

[42]  M. Loik,et al.  A multi-scale perspective of water pulses in dryland ecosystems: climatology and ecohydrology of the western USA , 2004, Oecologia.

[43]  T. Burgess,et al.  Temporal and spatial patterns in emergence and early survival of perennial plants in the Sonoran Desert , 2004, Plant Ecology.

[44]  S. Arundel.  Using spatial models to establish climatic limiters of plant species’ distributions , 2005 .

[45]  F. Pugnaire,et al.  Rooting depth and soil moisture control Mediterranean woody seedling survival during drought , 2007 .

[46]  F. Pugnaire,et al.  Early root growth plasticity in seedlings of three Mediterranean woody species , 2007, Plant and Soil.

[47]  F. Maestre,et al.  Where do seedlings go? A spatio-temporal analysis of seedling mortality in a semi-arid gypsophyte , 2008 .

[48]  J. Retana,et al.  Age-specific, density-dependent and environment-based mortality of a short-lived perennial herb. , 2008, Plant biology.

[49]  H. S. Gentry.  The natural history of Jojoba (Simmondsia chinensis) and its cultural aspects , 1958, Economic Botany.

[50]  S. Archer,et al.  Shrub (Prosopis velutina) encroachment in a semidesert grassland: spatial–temporal changes in soil organic carbon and nitrogen pools , 2008 .

[51]  Richard Felger.  Sonoran desert plants. An ecological atlas , 1996, Economic Botany.

[52]  B. Milne,et al.  Allometry, growth and population regulation of the desert shrub Larrea tridentata , 2008 .

[53]  A. Elger,et al.  Plant ontogeny and chemical defence: older seedlings are better defended , 2009 .

[54]  M. Estiarte,et al.  Plant community changes induced by experimental climate change: Seedling and adult species composition , 2009 .

[55]  S. Kurc,et al.  Digital image-derived greenness links deep soil moisture to carbon uptake in a creosotebush-dominated shrubland , 2010 .

[56]  M. Srivastava.  Analysis of variance and covariance: how to choose and construct models for the life sciences , 2010 .