The elevated carbon dioxide facility has arrays of both large and small open-top chambers to study the responses of plants and other organisms to rising atmospheric CO2. Enough carbon dioxide can be delivered to the experimental chambers to double the ambient concentration (control chambers). Several investigators have studied the effects of elevated CO2 on the above- and below-ground responses of native deciduous trees such as bigtooth and trembling aspen, sugar maple, and hemlock, and on herbaceous species including crucifers, legumes, C3 and C4 grasses, and several invasive species including cattails and spotted knapweed.