C₄ Plant Productivity and Climate-CO₂ Variations in South-Central Texas during the Late Quaternary

Abstract

A continuous record of organic carbon δ13C from a buried soil sequence in south-central Texas demonstrates: 1) strong coupling between marine and adjacent continental ecosystems in the late Pleistocene as a result of glacial meltwater entering the Gulf of Mexico and 2) ecosystem decoupling in the Holocene associated with a reduction of meltwater and a shift in global circulation patterns. In the late Pleistocene, reduction in C4 plant productivity correlates with two well-documented glacial meltwater pulses (∼15,000 and 12,000 14C yr B.P.), indicating a cooler-than-present adjacent continental environment. Increased C4 production between 11,000 and 10,000 14C yr B.P. suggests that the Younger Dryas was a warm interval responding to the diversion of glacial meltwater away from the Mississippi River. With waning meltwater flow, C4 productivity generally increased throughout the Holocene, culminating in peak warm intervals at ∼5000 and 2000 14C yr B.P. Shifts in the abundances of C3–C4 plants through the late Quaternary show no correlation to ecophysiological responses to atmospheric CO2 concentration.

Archaeological Investigations at the Ice House Site, 41HY161: Early Archaic Technology, Subsistence, and Settlement Along the Balcones Escarpment, Hays County, Texas

“…Along the Medina River in South Central Texas, a similar relationship between stable carbon isotopes was noted (Nordt, et al 2002). Nordt et al (2002) correlate major changes in C4 plant production to the major meltwater pulses at the end of the Pleistocene.…”

“…Nordt et al (2002) correlate major changes in C4 plant production to the major meltwater pulses at the end of the Pleistocene. The influx of glacial meltwaters into the Gulf of Mexico lowered surface water temperatures and decreased surface temperatures in Texas.…”

Spatial and temporal variations of C3/C4 relative abundance in global terrestrial ecosystem since the Last Glacial and its possible driving mechanisms

“…In the Kashmir Basin (Figure 1), India, almost all the paleosols in the loess, indicating climate amelioration, support significant C 4 vegetation [42,43], which is similar to the results from the Chinese loess/paleosol sequences. Soil organic   13 C records from the central Great Plains (including several sites in South Dakota and Nebraska, Figure 1) [44], and adjacent central and south-central Texas (Figure 1) [45,46] [49]. Obviously, from the Last Glacial to the Holocene, relative abundance of C 4 plants in the source regions increased; such a change trend is apparently similar to the compound-specific  …”

Archeological Testing and Data Recovery at 41ZV202, Zavala County, Texas

“…The Central Texas climate reconstructions rely on a variety of different data sets. These data sets include shifts in pollen (see Bousman 1998;Bryant and Holloway 1985;Nickels and Mauldin 2001), changes in stream flow geomorphology (Nordt 1992), variation in small vertebrate fauna (see Toomey 1993), and shifts in carbon isotopic signatures in sediments (e.g., Cooke 2005;Nordt et al 1994;Nordt et al 2002).…”

“…A rapid decline is then initiated, suggesting a return to cooler temperatures over the last 1,800 years. The Medina River sequence (see Figure 2-6) is shown as a dashed line in Figure 2-8 (see Nordt et al 2002). These stable carbon isotope data come from a series of stream terrace deposits.…”