© Springer International Publishing Switzerland 2016 227
M.J. Germino et al. (eds.), Exotic Brome-Grasses in Arid and Semiarid
Ecosystems of the Western US, Springer Series on Environmental Management,
DOI 10.1007/978-3-319-24930-8_8
Chapter 8
Soil Moisture and Biogeochemical Factors
Infl uence the Distribution of Annual Bromus
Species
Jayne Belnap , John M. Stark , Benjamin M. Rau , Edith B. Allen ,
and Susan Phillips
Abstract Abiotic factors have a strong infl uence on where annual Bromus species are
found. At the large regional scale, temperature and precipitation extremes determine
the boundaries of Bromus occurrence. At the more local scale, soil characteristics
and climate infl uence distribution, cover, and performance. In hot, dry, summer-
rainfall-dominated deserts (Sonoran, Chihuahuan), little or no Bromus is found,
likely due to timing or amount of soil moisture relative to Bromus phenology. In hot,
winter-rainfall-dominated deserts (parts of the Mojave Desert), Bromus rubens is
widespread and correlated with high phosphorus availability. It also responds posi-
tively to additions of nitrogen alone or with phosphorus. On the Colorado Plateau,
with higher soil moisture availability, factors limiting Bromus tectorum populations
vary with life stage: phosphorus and water limit germination, potassium and the
potassium/magnesium ratio affect winter performance, and water and potassium/
J. Belnap (*)
US Geological Survey , Southwest Biological Science Center , Moab , UT 84532 , USA
e-mail: [email protected]
J. M. Stark
Department of Biology, and the Ecology Center , Utah State University , Logan ,
UT 84322-5305 , USA
e-mail: [email protected]
B. M. Rau
US Department of Agriculture, Forest Service , Southern Research Station , Aiken ,
SC 29803 , USA
e-mail: [email protected]
E. B. Allen
Department of Botany and Plant Sciences , University of California, Riverside ,
Riverside , CA , USA
e-mail: [email protected]
S. Phillips
US Geological Survey , Forest and Rangeland Ecosystem Center , Corvallis , OR 97330-6169 , USA
e-mail: [email protected]