Decomposition of Spartina anglica roots and rhizomes in a salt marsh of the Westerschelde Estuary

Abstract

ABSTRACT: Decomposition of roots of the salt marsh grass Spartina anglica was inveshgated using litter bags. The pattern of disappearance of the root matenal was essentially the same at sol1 depths of 30, 15, and 3 cm, and above-ground. Average calculated turnover time for S. anglica root material varied between 2.0 and 3.9 yr. These differences are due to variations in decay rates at the various depth levels and marsh locations. At the creek levee and low marsh study site, decomposition rate decreased with depth. This phenomenon was less obvious at the moderately vegetated middle marsh site. A possible explanation of these observations may be found in the interactions of living roots with the decomposer community in the salt marsh sedment. S. anghca roots decomposed faster wth increasing elevation of the marsh location, indicating that inundation frequency is an important factor in determin- ing the rate of decay processes. Percentage nitrogen in the litter increased in time, both below-ground and above-ground. There was a strong positive correlation between the percentage nitrogen and the percentage weight loss of root material. In contrast to nitrogen levels, the percentage of extractable protein in the root litter decreased rapidly to undetectable levels a few months after the start of the expenment. This finding underlines the difficulty in interpreting elemental N values in terms of resource quality. The course of protein decrease was similar on all depth levels and locahons; this suggests that the transformation of compounds valuable to microbial metabolism, such as proteins, is much less responsive to environmental factors than the majority of plant materials. occur