Light rings chronology from black spruce (Picea mariana [Mill.] BSP.) in subarctic Quebec: AD 706 to AD 1675.

Light rings chronology from black spruce (Picea mariana [Mill.] BSP.) in subarctic Quebec: AD 706 to AD 1675. The sampling of 1335 tree remains buried in three peatlands from subarctic Quebec allowed us to extend by more than 600 years the light ring chronology of black spruce (Picea mariana [Mill.] BSP.) from A.D. 706 to 1339. In total, 257 light rings have been identified over the A.D. 706-1675 period, among which 124 formed before A.D. 1339. Light rings of A.D.709,713,759,772,774,810,885,931, 945,973,998,1056,1067,1104,1126,1157, 1162, 1170, 1215, 1256, 1258 and 1309 occurred in more than 75% of all sampled stems. Diagnostic light rings are well distributed in time, except between A.D. 811 and 872 with no light ring occurring in more than 25% of all sampled tree subfossils. Several unfrequent light-ring years were identified because of the large number of sampled subfossil trees. In addition, light ring frequency was highly correlated between the studied sites, indicating that local site conditions have only minor influence an the formation of light ring compared to climatic conditions. Several diagnostic tree-ring sequences, including an alternation of light rings and narrow rings, are also useful for the crossdating of subfossil spruce.