Dendrochronological analysis of baldcypress (Taxodium distichum) responses to climate and contrasting flood regimes

Baldcypress (Taxodium distichum (L.) Rich.) has been used extensively for dendrochronological reconstruction of climate and is a key species in globally important wetlands with complex, poorly understood relationships between hydrological and ecological processes. To better understand ecosystem responses to changing climate and hydrology and to test whether hydrological or climatological variables are most reflected in chronologies, we developed tree-ring chronologies for six stagnant or riverine swamps in the Mississippi River deltaic plain and modeled growth responses to historical hydrology (51 years of data) and climate (111 years of data). Decoupled flooding and local climate in this deltaic setting allowed for relatively independent assessments of the roles of hydrology and climate in baldcypress growth. Depth of annual flooding was positively correlated with growth that year but negatively correlated with growth in the ensuing year for both riverine and stagnant swamps. Depth of 10-year mean flooding was positively correlated with growth in riverine swamps but negatively correlated with growth in stagnant swamps. Results corroborate previous findings that long-term, stagnant flooding reduces productivity, but growth at these deltaic sites was less correlated with climatic variables than elsewhere. At least in these frequently flooded sites, baldcypress tree rings appear to be a better long term record of hydrological history than of climatic history.