Lab Assignment Two

Models for predicting the spatial distributions of plants

Plant Ecology Lab

Dear employee,

The science advisor for the congressman from the 7th Congressional District of Utah has contacted our office requesting information to advise the congressman, Representative I.M. “Skip” Tick, for the upcoming debates about “forest dynamics and climate change in the western United States”. In particular, the congressman is concerned about resolving two sets of very contrasting statements that constituents have emailed his office over the past week or so.

• “The pine forests of the Wasatch Front are safe from any possible future climate changes. After all, pines already grow from the mouth of the canyons up through the ski resorts. None of these trees have ever been susceptible to water stress in the past. What makes you think that they will be susceptible to drought in the future? Everybody already knows that only insects kill trees.”
• “The coniferous and riparian forests along the Wasatch Front exhibit a pronounced climate zonation, with the lower distribution limits of each tree species being determined by long-term, annual site water balance. Thus, the distributions of tree species are very sensitive to potential climate changes, particularly to factors relating to changes in available soil moisture. We can already describe and predict the north- versus south-slope differences in tree distributions on the basis of site water balance; therefore we can predict some of the anticipated future changes in forest vegetation.”

• a field trip to Big Cottonwood Canyon where all relevant data will be collected
• a manual to identify the common tree and shrub species
• an altimeter
• a compass and inclinometer
• an Excel software program to predict evapotranspiration rates
• data on the monthly maximum and minimum air temperatures
• data on the precipitation patterns along the west side of the Wasatch Front