Table 1.

Changes (%) in the photosynthetic variables (PV), net photosynthetic rates (A) and stomatal conductance to CO₂ (g_c) of J. virginiana trees over the 100-y chronology derived the simulation analysis using C_i from tree-ring isotopic data, atmospheric CO₂ (7, 8), and the relationships between A and C_i measured on J. virginiana foliage in 2009

PV	1909–1920	1920–1930	1930–1940	1940–1950	1950–1960	1960–1970	1970–1980	1980–1990	1990–2000	2000–2008
A	−1.9	−2.0	5.9	−2.5	0	−1.7	0	5.9	10.5	11.1
gc	−11.3	−10.8	14.9	−7.5	−5.6	−12.1	−4.6	3.1	15.1	18.4