Plant Communities

The terracosms are planted with a native Willamette Valley grassland plant community.
This community is ideal because it reaches a maturity within a few years, and the plants have small stature and fit well within the chambers.

We used plant surveys performed by the Institute for Applied Ecology to select 14 of the most common species in native-dominated areas, plus one rare, but easily grown native species. The final species list included annuals and perennials, forbs and grasses, and a nitrogen-fixer.


One of the unique features of the experimental design is all of the terracosms were planted in the same layout (above). That means in every chamber the same species can be found in the same location, with the same neighbors! This consistency improves our ability to separate the impacts of the temperature treatments from a plant's immediate environment. The replicated grid also helps reduce noise in other measurements that plants might impact. When we measure soil nutrient concentrations or soil respiration, we know that the plants immediately surrounding the measurement location are the same in every chamber.

The plants were started from seedlings in 2005 and allowed to become established for a year under ambient conditions before temperature treatments began.

Some of the key plant variables we measure include:
  • Plant cover
  • Root biomass
  • Timing and amount of fall green-up and summer senescence
  • Timing and amount of flowering

Measuring plant variables with the "hovercraft".

   May 19, 2009(round disk in center is soil respiration chamber)