Within C3 plants processes regulating changes in δ13C are well understood, particularly at the leaf level,[8] but also during wood formation.[9][10] Many recent studies combine leaf level isotopic fractionation with annual patterns of wood formation (i.e. tree ring δ13C) to quantify the impacts of climatic variations and atmospheric composition on physiological processes of individual trees and forest stands.[11][12][13] The next phase of understanding, in terrestrial ecosystems at least, seems to be the combination of multiple isotopic proxies to decipher interactions between plants, soils and the atmosphere, and predict how changes in land use will affect climate change.