A number of Sevilleta (SEV) LTER publications, several by graduate students, have recently been published by respectable journals in the field of ecology.
First, Robin Warne, Alaina Pershall, and Blair Wolf reported in the journal Ecology on the impact of interannual climate variability at the SEV and its effects on C3 and C4 plants (which have different photosynthetic pathways), grasshoppers, and lizards. They found that during normal rainfall years consumers (grasshoppers and lizards) used an increasing proportion of C4 derived resources over the growing season. However, during a spring with below average precipitation, the consumers relied on C4 resources that were likely carried over from previous year’s production. This finding demonstrates the degree of diet flexibility that consumers like grasshoppers and lizards need to have to survive in this highly variable system, which has implications for community composition and structure under future patterns of climate variability.
In a second paper entitled “Tissue-Carbon Incorporation Rates in Lizards: Implications for Ecological Studies Using Stable Isotopes in Terrestrial Ectotherms” in Physiological and Biochemical Zoology, Warne, Gilman, and Wolf used stable isotopes to determine the tissue incorporation rates of carbon in two species of lizards. They found that carbon incorporation rates in various tissues were much slower than for comparably sized endotherms.
Continuing with the grad student theme, Juliana Medeiros and Will Pockman recently reported in the Journal of Arid Environments that smaller (presumably younger) creosote plants are wiser than larger (older) plants. That is, smaller plants had higher growth rates but maintained larger safety margins from transpiration rates under water stress that could lead to hydraulic failure and death.
Rounding up our grad student papers for this round, Megan Friggens and colleagues recently reported in the Journal of Wildlife Diseases on a three-year survey of fleas on rodents and in prairie dog burrows in the Valles Caldera Preserve. The study, which was supported with a SEV LTER Summer Fellowship for a regional comparative study of fleas and plague, found a small number of fleas with evidence of plague, but the results suggest that fleas in burrows can be an important reservoir for plague bacteria that can result in outbreaks when conditions are appropriate.
Writing in the journal Ecosystems, Pockman and Eric Small reported that redistribution of water following a 15mm precipitation event in the grass-shrub ecotone at the Sevilleta led to enhanced infiltration and higher soil water content under grasses and shrubs compared to patches of “unvegetated” soil. However, redistribution of surface water led to a greater amount of soil water in the root volume of grasses relative to shrubs, resulting in lower plant water stress in grasses compared to shrubs following this one rain event. The results suggest that redistribution and infiltration under grasses can increase their competitive ability and perhaps slow shrub encroachment by creosote into these grasslands.
Finally, Michael Allen and colleagues reported in the Journal of Arid Environments on the effects of long-term nitrogen (N) fertilization on mycorrhizae abundance and responses of piñon pines and juniper in relation to drought. Fertilization led to a decrease in mycorrizae and an increase in leaf production in piñon but not in juniper. As a consequence, piñon pines on the fertilized plots started to suffer mortality a year earlier than piñon on control plots during the 2000-2003 drought. Thus, N enrichment and loss of ectomychorrizae from piñon could enhance their susceptibility to future climate extremes, particularly drought.
Copies of these publications in PDF format can be obtained through http://tierra.unm.edu/publications
by Scott Collins