Monson and his collaborators are planning to take this a step further, studying oxygen and carbon isotope composition of the wood in tree rings.
"By looking at the isotope ratios in the wood, we can potentially resolve wet and dry years along very sensitive quantitative scales, providing even more accurate reconstructions of past monsoon intensities," he said.
The researchers will use tree-ring data to test and validate computer models that will be developed to model the monsoon and how it is expected to change over time.
A central focus of the grant is on the interconnections among invasive plants, monsoon weather patterns and fire. Monson and his co-workers decided to focus on pinion pine/juniper forest at intermediate elevations as a critical connector between low-elevation desert and high-elevation forests with respect to the upward spread of wildfires.
"Many wildfires start in the grassland at lower elevations, where dry grasses provide ready tinder for ignition by lightning strikes," Monson explained. He said grass doesn't carry a lot of fuel, but ignites quickly, causing fire to spread rapidly across the surface.
"With invasive grasses like cheat grasses and buffelgrass advancing into higher elevations, those fires can jump to pinion pine and juniper forests at intermediate elevations where there is a lot of wood and flammable needles to burn, and then to the higher-elevation ponderosa pine ecosystem where there is even more fuel," Monson said.
"We are trying to study that dynamic both through tree-ring analyses of past fire frequencies and modeling of current potential for fire frequencies in different years with different amounts of precipitation," he also said.
"An important part of what we want to study is how those invasive grasses change the fire frequency and how the monsoon rains affect that transmission of the fires from lower to higher
|Contact: Daniel Stolte|
University of Arizona