Relationship between Chemical Characteristics of Autumn-Shed Leaves and Aquatic Processing Rates

Abstract

Processing rates of autumn-shed leaves in aquatic habitats are highly variable. It has been hypothesized that these processing rates may, in part, be regulated by the concentrations of residual tannins in the leaves. Tests of this hypothesis have been inconclusive, and experimental designs may have been compromised by the use of both processing rates and tannin concentrations taken from a variety of sources using highly variable methods, sites, and experimental conditions. Here, processing rates of 48 species of deciduous leaves are measured using uniform conditions, and related to concentrations of leaf tannins, N, P, C:N, lignin, and toughness. The results indicate that condensed tannin, N, C:N, and lignin are significantly correlated with processing rates, although the predictive power of these simple relationships is weak. A multiple regression model using tannins, measured as total phenolics, N, and lignin explained almost 50% of the variation in processing rates, suggesting that the inhibition of processing by tannins is modified by other measures of leaf quality.

Diversity of Fungi, Bacteria, and Actinomycetes on Leaves Decomposing in a Stream

“…The decay rates of maple and oak leaves we determined are comparable to those reported from other studies which also found oak leaves to be processed more slowly than maple leaves (47,53). The exponential decay model explained 69 and 61% of the variability for maple and oak leaves, respectively, in our study.…”

“…White oak leaves have a higher lignin content and greater toughness than sugar maple leaves that should require greater microbial action to breakdown (47). Yet, in spite of these differences in decomposition and known differences in leaf chemistry (47), few differences in the microbial community were detected between the leaf species.…”

“…White oak leaves have a higher lignin content and greater toughness than sugar maple leaves that should require greater microbial action to breakdown (47). Yet, in spite of these differences in decomposition and known differences in leaf chemistry (47), few differences in the microbial community were detected between the leaf species. For example, fungal biomass did not differ between the leaf types, although peak fungal biomass estimates were within the range of values reported in the literature for leaves in streams (2,14,70).…”

“…The leaves of these two species were selected because of differences in their chemical composition and decomposition rates as reported in a study examining the relationship between breakdown rates and chemistry of autumn-shed leaves (47). Specifically, white oak leaves had greater lignin content, C/N ratio, and toughness than did sugar maple leaves, which decayed five times faster than oak leaves.…”

Organic matter decomposition by fungi in a Mediterranean forested stream : contribution of streambed substrata

“…The lower enzymatic activities for the biofilm on Platanus x hispanica was already observed in previous studies developed on leaf decomposition in soil and in other aquatic habitats. The high C : N ratio measured in this substratum (Bernal et al 2003, Ostrofsky 1997) may be pointed out as the cause for the low mineralisation observed for this material. Slower breakdown of Platanus leaves than other indigenous Mediterranean leaf species (e. g: Populus nigra) (Casas & Gessner 1999) is probably caused by the higher lignin and other recalcitrant compounds content in the former (Ostrofsky 1997).…”