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CO 2 fertilization and enhanced drought resistance in G reek firs from C ephalonia I sland, G reece
Author(s) -
Koutavas Athanasios
Publication year - 2013
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/gcb.12053
Subject(s) - precipitation , dendrochronology , growing season , stomatal conductance , moisture , environmental science , zoology , atmospheric sciences , horticulture , climatology , chemistry , botany , biology , geography , physics , meteorology , geology , photosynthesis , paleontology , organic chemistry
Growth–climate relationships were investigated in G reek firs from A inos M ountain on the island of C ephalonia in western G reece, using dendrochronology. The goal was to test whether tree growth is sensitive to moisture stress, whether such sensitivity has been stable through time, and whether changes in growth–moisture relationships support an influence of atmospheric CO 2 on growth. Regressions of tree‐ring indices ( ad 1820–2007) with instrumental temperature, precipitation, and Palmer Drought Severity Index ( PDSI ) indicate that growth is fundamentally limited by growing‐season moisture in late spring/early summer, most critically during J une. However, this simple picture obscures a pattern of sharply evolving growth–climate relationships during the 20th century. Correlations between growth and J une temperature, precipitation, and PDSI were significantly greater in the early 20th century but later degraded and disappeared. By the late 20th–early 21st century, there remains no statistically significant relationship between moisture and growth implying markedly enhanced resistance to drought. Moreover, growth experienced a net increase over the last half‐century culminating with a sharp spike in ad 1988–1990. This recent growth acceleration is evident in the raw ring‐width data prior to standardization, ruling out artifacts from statistical detrending. The vanishing relationship with moisture and parallel enhancement of growth are all the more notable because they occurred against a climatic backdrop of increasing aridity. The results are most consistent with a significant CO 2 fertilization effect operating through restricted stomatal conductance and improved water‐use efficiency. If this interpretation is correct, atmospheric CO 2 is now overcompensating for growth declines anticipated from drier climate, suggesting its effect is unusually strong and likely to be detectable in other up‐to‐date tree‐ring chronologies from the M editerranean.