Stable carbon isotope labeling reveals different carry‐over effects between functional types of tropical trees in an Ethiopian mountain forest

Summary We present an intra‐annual stable carbon isotope (δ 13 C) study based on a labeling experiment to illustrate differences in temporal patterns of recent carbon allocation to wood structures of two functional types of trees, Podocarpus falcatus (a late‐successional evergreen conifer) and Croton macrostachyus (a deciduous broadleaved pioneer tree), in a tropical mountain forest in Ethiopia. Dendrometer data, wood anatomical thin sections, and intra‐annual δ 13 C analyses were applied. Isotope data revealed a clear annual growth pattern in both studied species. For P. falcatus , it was possible to synchronize annual δ 13 C peaks, wood anatomical structures and monthly precipitation patterns. The labeling signature was evident for three consecutive years. For C. macrostachyus , isotope data illustrate a rapid decline of the labeling signal within half a year. Our δ 13 C labeling study indicates a distinct difference in carryover effects between trees of different functional types. A proportion of the labeled δ 13 C is stored in reserves of wood parenchyma for up to 3 yr in P. falcatus . By contrast, C. macrostachyus shows a high turnover of assimilates and a carbon carryover effect is only detectable in the subsequent year.