Decomposition dynamics of six salt marsh halophytes as determined by cupric oxide oxidation and direct temperature‐resolved mass spectrometry

Abstract

This paper presents the results of a comparative study on the aerobic decomposition of six salt marsh plant species over a period of 2 yr. In addition to ash‐free dry weight (AFDW) determination and elemental analysis (C and N), two analytic methods have been applied to obtain insight into the decomposition dynamics of lignin in the various plant tissues. The analytic methods are (1) cupric oxide (CuO) oxidation followed by gas chromatography—mass spectrometry (GC‐MS) and (2) direct temperature‐resolved mass spectrometry (DT‐MS). AFDW losses could generally be well described by double exponential relations with time. Carbon‐to‐nitrogen ratios increased during the initial stages of decomposition and decreased again afterward. For five of the six plant species, a correlation between initial lignin content and AFDW loss was observed. Decay dynamics of lignin denoted a rapid relative increase during the first weeks of field exposure, followed by stabilizing contents over the next 2 yr. CuO oxidation data indicate the establishment of a stable “lignin endmember” within 1–2 months. DT‐MS data, on the contrary, showed continuous modification of the lignin polymer throughout the duration of the experiment. Evidence was found for the incorporation of (presumably) microbial N‐acetylglucosamine in the complex residue produced upon decomposition. Combination of CuO oxidation and DT‐MS data suggested that lignin degradation products became attached to the original macromolecular material and could still be identified as lignin‐derived material. The data support a humification mechanism via condensation of small degradation products instead of the selective preservation of certain biomacromolecules (like lignin).

Lignin biomarkers as tracers of mercury sources in lakes water column

“…However, a significant increase in C/V ratios has been observed in the deeper inorganic soil horizon with respect to the organic soil horizon (Houel et al 2006). That is, [C] tend to be leached disproportionately, compared to [V] phenols upon early degradation processes (Opsahl and Benner 1995;Klap et al 1999;Dittmar and Lara 2001). The mobility of [C] in soil environments could occur not only horizontally-erosion toward lakes-but also vertically (Kaiser et al 2001;Rumpel et al 2002).…”

“…Hence, the increasing C/V ratios in the DOM fraction (prob. F: 0.0009) throughout the sampling period could be the result of a selective leaching of cinnamyls, and ester-bound acids (Opsahl and Benner 1995;Klap et al 1999). Besides, decreases of the C/V ratios were solely reported to occur during the pedogenetic or diagenetic OM degradation (Opsahl and Benner 1995;Klap et al 1999;Louchouarn et al 1999).…”

“…Lower S/V ratios could be resulting from greater gymnosperms contribution, pedogenetic processes (Otto and Simpson 2006) or selective dissolution/sorption processes in soil, prior to the introduction of the terrestrial OM Table 4 Average summer values of lignin biomarkers in the dissolved (DOM) and particulate organic matter (POM), sampled in June, July, August and September, of six boreal Biogeochemistry (2009) 94:123-140 131 in the water column (Kaiser et al 2001;Rumpel et al 2002;Houel et al 2006;Hernes et al 2007). The degradation of lignin through fungal, microbial and fractionation, during leaching and sorption in soil, has been reported to modify signatures in soils horizons from pure sources signals (Hedges et al 1988;Opsahl and Benner 1995;Klap et al 1999;Hernes et al 2007). This degradation of lignin has been associated with changes in S/V and C/V ratios (Hedges et al 1988;Opsahl and Benner 1995;Dittmar and Lara 2001).…”

Translocation of soil organic matter following reservoir impoundment in boreal systems: Implications for in situ productivity

“…This latter ratio in preflooding sediments is more characteristic of signatures from SOM sorbed on deep fine soil minerals. Although the C : V ratio is known to decrease during the transfer of terrigenous organic matter from the water column to sediment deposits due to a selective sensitivity of cinnamyl moieties to diagenetic alterations (Opsahl and Benner 1995;Klap et al 1999;Louchouarn et al 1999), in situ alteration of lignin composition is usually minor within sediments (Hedges et al 1982;Ishiwatari and Uzaki 1987;Louchouarn et al 1997a) and C : V signatures of mature organic matter can still retain a good amount of source information Hedges et al 2000). It thus seems that the strong shift in C : V signatures observed here are indicative of substantial changes in the source materials, rather than large-scale diagenetic transformation of sedimentary organic matter.…”

The feeding ecology of penaeid shrimp in tropical lagoon-estuarine systems

“…These shallow coastal environments may be characterized by gradual or sharp daily and seasonal variations in their physico-chemical water parameters, owing to their dynamic geohydrology; the regular annual fl ooding of salt marsh plants causes an important decomposition of primary land producers (Klap et al 1999). Additionally, the drying and cracking of sediments accelerates the cycling of trapped nutrients (Arenas & De La Lanza 1981, Simoes et al 2011.…”