The effect of flooding regimes on decomposition of Polygonum pensylvanicum in playa wetlands (Southern Great Plains, USA)

Abstract

Plants in playa wetlands are hypothesized to have high decomposition rates due to rapidly fluctuating water levels. Therefore, Polygonum pensylvanicum (a dominant playa species) decomposition rates were studied in relation to four water regimes (F1 (flooded 30% of 321 days), F2 (41%), F3 (58%), or F4 (100%)) in playa wetlands of the Southern Great Plains of Texas, 1996–1997. Decomposition rates of stems, leaves, and seeds were generally lowest ( P<0.001) in the F3 and F4 treatments and highest in the F1 and F2 treatments. The highest rates of decomposition for all plant parts occurred within 56 days of placement in the field ( P<0.001), and gradually declined until the conclusion of the study (321 days). Crude protein levels were initially highest in leaves (21.9%) and lowest in stems (3.9%), whereas cellulose and hemicellulose levels were highest in stems (51.4 and 33.3%, respectively) and lowest in leaves (24.3 and 17.7%, respectively); seeds had moderate levels (protein (9.8%); cellulose (46.8%); hemicellulose (30.4%)). However, decomposition rates of seeds were lower ( P<0.001) than decomposition rates of stems and leaves. The natural wet–dry cycles in playas enhance decomposition and productivity of playa wetlands.