Search USGS⌕ Search
Home/Archive/USGS

USGS · 70026829

Composition, dynamics, and fate of leached dissolved organic matter in terrestrial ecosystems: Results from a decomposition experiment

C.C. Cleveland·J. C. Neff·A.R. Townsend·E. Hood
View original source ↗Export metadata ↓

Abstract

Fluxes of dissolved organic matter (DOM) are an important vector for the movement of carbon (C) and nutrients both within and between ecosystems. However, although DOM fluxes from throughfall and through litterfall can be large, little is known about the fate of DOM leached from plant canopies, or from the litter layer into the soil horizon. In this study, our objectives were to determine the importance of plant-litter leachate as a vehicle for DOM movement, and to track DOM decomposition [including dissolve organic carbon (DOC) and dissolved organic nitrogen (DON) fractions], as well as DOM chemical and isotopic dynamics, during a long-term laboratory incubation experiment using fresh leaves and litter from several ecosystem types. The water-extractable fraction of organic C was high for all five plant species, as was the biodegradable fraction; in most cases, more than 70% of the initial DOM was decomposed in the first 10 days of the experiment. The chemical composition of the DOM changed as decomposition proceeded, with humic (hydrophobic) fractions becoming relatively more abundant than nonhumic (hydrophilic) fractions over time. However, in spite of proportional changes in humic and nonhumic fractions over time, our data suggest that both fractions are readily decomposed in the absence of physicochemical reactions with soil surfaces. Our data also showed no changes in the δ 13 C signature of DOM during decomposition, suggesting that isotopic fractionation during DOM uptake is not a significant process. These results suggest that soil microorganisms preferentially decompose more labile organic molecules in the DOM pool, which also tend to be isotopically heavier than more recalcitrant DOM fractions. We believe that the interaction between DOM decomposition dynamics and soil sorption processes contribute to the δ 13 C enrichment of soil organic matter commonly observed with depth in soil profiles.

Explore related subjects

EcosystemsArticle

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

C.C. Cleveland, J. C. Neff, A.R. Townsend, E. Hood. 2004-04-02. Composition, dynamics, and fate of leached dissolved organic matter in terrestrial ecosystems: Results from a decomposition experiment. https://doi.org/10.1007/s10021-003-0236-7

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Identifying headwater streams across the conterminous United States

Headwater streams play critical roles in hydrologic and biogeochemical processes and functions, yet their spatial distribution and land cover context remain poorly understood at continental scales, and no dedicated geospatial dataset exists. Building from a high-resolution conterminous United States (CONUS) hydrography network dataset, we quantified the spatial extent, density, and upstream catchment characteristics of headwater stream segments across the CONUS. We identified approximately 8.4 million kilometers of headwater streams, finding that 77% of the total stream network consists of headwaters, nearly double the total length represented in prior estimates. Stream density varied fivefold across regions, from < 1 km·km −2 in arid basins to > 5 km·km −2 in humid, forested areas. Over 73% of the CONUS landmass drains from headwater streams. The majority of headwater stream length occurred in forested and cultivated catchments across the CONUS, while substantial regional differences were evident for headwater stream distribution in other land cover classes (for example, wetlands, urban areas, shrublands, and herbaceous-dominated catchments). The dedicated and novel geospatial dataset, HELiOS (HEadwater streams and Low-Order Systems) is introduced for management and research use. The HELiOS dataset provides the first continental-scale, high-resolution characterization of headwater streams, offering new insights and opportunities for hydrologic modeling, ecological assessments, and environmental policy.

conterminous United States↗
USGS2025

Variation in soil organic carbon across a latitudinal chronosequence of mangrove poleward expansion

The critical carbon sink provided by coastal wetlands, known as blue carbon, can be affected by multiple aspects of climate change. One important example is warming-induced mangrove poleward expansion, which is shifting dominant plant cover across tropical–temperate transitional zones and altering ecosystem structure and function. We examined how mangrove expansion affects soil organic carbon (SOC) quantity and source, using measurements of SOC density and isotopic signatures (δ 13 C and δ 15 N) at 15 sites across Florida’s west coast (USA). The sampled sites represent examples of three expansion stages: a latitudinal chronosequence of mangrove expansion, spanning mature mangroves in the south, former ecotones at mid latitudes, and current ecotones in the north. Our analyses of soil core data indicate that mangrove expansion stage is a significant predictor of SOC density, δ 13 C, and δ 15 N, but not C:N ratio. Current ecotones exhibited significantly lower SOC density but higher δ 13 C, suggesting a greater contribution of preexisting C 4 salt marshes, while no difference was found between former ecotones and mature mangroves. SOC density, δ 13 C, and δ 15 N were found to vary with mangrove aboveground biomass, stage, and sedimentary setting along the latitudinal gradient. For all three mangrove expansion stages, SOC density decreased with depth, but δ 13 C showed no vertical trend, suggesting that mangroves contributed organic carbon to the entire 20-cm soil profile. The observed regional trend of SOC across mangrove expansion stages highlights the ecological impacts of warming-driven vegetation shifts in coastal wetlands, though further evidence is needed to determine the primary drivers and mechanisms, while also considering local and regional environmental factors.

Florida↗
USGS2025

Quantifying benthic flux of Mysis biomass through diel vertical migration at the ecosystem scale

Mysis diluviana is a macroinvertebrate that couples benthic and pelagic habitats on a daily timescale through diel vertical migration (DVM). However, quantifying how much Mysis biomass is exchanged between benthic and pelagic habitats at an ecosystem scale is difficult because of sampling limitations and variability in Mysis DVM behavior related to light and depth. Although Mysis are benthic-pelagic migrators, a portion remains pelagic during the day offshore in Lake Ontario, partially contradicting the assumption of population-level DVM over deep areas. To estimate the amount of biomass transferred from benthic to pelagic habitat via DVM in Lake Ontario, we estimated the portion of pelagic biomass at night originating from benthic habitat as the difference between night and day pelagic estimates from net tows along a bathymetric depth gradient. We then modeled the portion as a function of depth, extrapolated these depth-dependent estimates to an existing lake wide night-pelagic dataset, and summed amounts across depth strata. We estimated more biomass was transferred from benthic to pelagic habitat at intermediate lake depths (100–160 m) despite greater offshore (> 180 m) night-pelagic biomass. Our results suggest ways to improve estimates of Mysis habitat coupling and how to account for important factors such as depth and light for modeling Mysis DVM behavior at the population- and ecosystem-levels.

Lake Ontario↗