Non-Native Plant Litter Enhances Soil Carbon Dioxide Emissions in an Invaded Annual Grassland

Abstract

Litter decomposition is a fundamental ecosystem process in which breakdown and decay of plant detritus releases carbon and nutrients. Invasive exotic plants may produce litter that differs from native plant litter in quality and quantity. Such differences may impact litter decomposition and soil respiration in ways that depend on whether exotic and native plant litters decompose in mixtures. However, few field experiments have examined how exotic plants affect soil respiration via litter decomposition. Here, we conducted an in situ study of litter decomposition of an annual native grass (Eragrostis pilosa), a perennial exotic forb (Alternanthera philoxeroides), and their mixtures in an annual grassland in China to examine potential invasion effects on soil respiration. Alternanthera litter decomposed faster than Eragrostis litter when each was incubated separately. Mass loss in litter mixes was more rapid than predicted from rates in single species bags (only 35% of predicted mass remained at 8 months) showing synergistic effects. Notably, exotic plant litter decomposition rate was unchanged but native plant litter decomposition rate was accelerated in mixtures (decay constant k = 0.20 month−1) compared to in isolation (k = 0.10 month−1). On average, every litter type increased soil respiration compared to bare soil from which litter was removed. However, the increases were larger for mixed litter (1.82 times) than for Alternanthera litter (1.58 times) or Eragrostis litter (1.30 times). Carbon released as CO2 relative to litter carbon input was also higher for mixed litter (3.34) than for Alternathera litter (2.29) or Eragrostis litter (1.19). Our results indicated that exotic Alternanthera produces rapidly decomposing litter which also accelerates the decomposition of native plant litter in litter mixtures and enhances soil respiration rates. Thus, this exotic invasive plant species will likely accelerate carbon cycling and increase soil respiration even at intermediate stages of invasion in these annual grasslands.

Litter decomposition in peatlands is promoted by mixed plants

“…In both laboratory and field experiments, mixing Sphagnum with Eriophorum and Pinus litter had a synergistic effect on litter decomposition. Such non-additive effects have already been reported for other ecosystems (Wu et al 2013;Zhang et al 2014), although the reasons are still unclear. Many studies have tried to explain such an effect by nutrient exchanges between litters (Vos et al 2013), litter chemical quality (Meier and Bowman 2010) or changes in habitat characteristics (Lecerf et al 2011).…”

Proteomic analysis reflects an environmental alkalinization-coupled pH-dependent mechanism of regulating lignocellulases in Trichoderma guizhouense NJAU4742

“…Briefly, the triangular flasks of solid-state fermentations were sealed with a parafilm 2 h before sampling. When sampling, 20 mL of gas in the triangular flask was extracted with a syringe and then injected into the gas sampling bag (E-SWITCH, China), and the contents of CO 2 was determined by a gas chromatography (Agilent 7890A) equipped with Porapak Q column and a flame ionization detector (FID) according to Zhang et al [44] with some modification: 500 µL of gas were injected through a septum with the temperature of 80 °C, and the carrier gas (N 2 ) flow-rate was 30 mL min −1 ; meanwhile, the temperature of the methanizer and detector were set as 450 °C and 250 °C, respectively.…”

Nitrogen Transformations Associated with N2O Emissions in Agricultural Soils

“…In general, in situ measurements could be conducted using static opaque chamber/gas chromatography method. To be speciic, circular or square grooved collars should be buried into soil, with groove illed with water to seal the gas collection chamber [32,33]. When soil N 2 O emission rate would be measured, open-botom cylindrical or cubic PVC gas sampling chamber would be it into the groove.…”

“…When cumulative emissions were needed for study purpose, total soil N 2 O emissions within a given time could be obtained by multiplying average soil N 2 O emission rate and the corresponding time span [17,33].…”