Streamflow Variability Indicated by False Rings in Bald Cypress (Taxodium distichum (L.) Rich.)

Abstract

Despite growing in wet lowland and riparian settings, Taxodium distichum (L.) Rich. (bald cypress) has a strong response to hydroclimate variability, and tree ring chronologies derived from bald cypress have been used extensively to reconstruct drought, precipitation and streamflow. Previous studies have also demonstrated that false rings in bald cypress appear to be the result of variations in water availability during the growing season. In this study 28 trees from two sites located adjacent to the Choctawhatchee River in Northwestern Florida, USA were used to develop a false ring record extending from 1881 to 2014. Twenty false ring events were recorded during the available instrumental era (1931–2014). This record was compared with daily and monthly streamflow data from a nearby gage. All 20 of the false-ring events recorded during the instrumental period occurred during years in which greatly increased streamflow occurred late in the growing season. Many of these wet events appear to be the result of rainfall resulting from landfalling tropical cyclones. We also found that the intra-annual position of false rings within growth rings reflects streamflow variability and combining the false-ring record with tree ring width chronologies improves the estimation of overall summer streamflow by 14%. Future work using these and other quantitative approaches for the identification and measurement of false ring variables in tree rings may improve tree-ring reconstructions of streamflow and potentially the record of tropical cyclone rainfall events.

A Paleo Perspective of Alabama and Florida (USA) Interstate Streamflow

“…(bald cypress; Table 3). As the longest-lived tree species in eastern North America, T. distichum has been shown to provide a valuable annual archive of multi-millennial paleo-hydroclimate conditions [3,8,9,14,29,31], and thus is ideal for developing these long reconstructions. Three TRCs were retained in the Choctawhatchee (Newton), Conecuh and Escambia River models, and two were retained by the Choctawhatchee (Bruce) and Perdido River models.…”

“…While dendrochronological reconstructions of hydroclimate, including streamflow, have been widely utilized in the western United States (US) due to the arid, moisturelimited environment [6,7,[16][17][18][19][20][21][22][23][24][25][26][27][28], until recently, similar studies have been relatively limited in the southeastern US [3,8,14,[29][30][31][32][33][34]. However, Crockett et al [2] established TRCs to be useful and statistically significant proxies even in the humid subtropical climate of northern Florida.…”

Baldcypress false ring formation linked to summer hydroclimatic extremes in the southeastern United States

“…Sites were selected for this study based on previous research for their hydroclimate sensitivity (Stahle and Cleaveland 1994, Stahle et al 2006, Harley et al 2017, Therrell et al 2020, Vines et al 2021. Thirty trees at each site were each cored twice using a 5 mm Haglof increment borer above buttress height.…”

“…If high river flows caused by anomalously high precipitation occur in the later growing season (June-October), earlywood production may begin again thus producing a false ring, similar to how North American monsoon rains in the southwestern US trigger renewed growth in Pinus ponderosa (Morino et al 2021). Therrell et al (2020) suggest that years with a stand-wide high production of false rings frequently occur as a result of tropical cyclone rainfall, and Mitchell et al (2019) demonstrated that Pinus palustris false rings occurred as a result of tropical cyclone occurrences from June-October as most Atlantic hurricane rainfall along the Gulf of Mexico coast occurs during June-September Tucker 2018, Bregy et al 2020).…”

“…baldcypress) is one of the longest-lived tree species occurring in North America and records of the species' tree-ring width can robustly reconstruct precipitation for thousands of years (Stahle et al 2012). This species is known to produce false rings in the presence of late-season flooding events (Therrell et al 2020). Young et al (1993) and Copenheaver et al (2017) report that inundation stress caused young T. distichum to produce false rings, while other studies indicate that streamflow variability drives tree-ring-width within the same species (Cleaveland 2000, Keim and Amos 2012, Palta et al 2012.…”