A re-evaluation of wetland carbon sink concepts and measurements: A diagenetic solution down sediments

Aquatic canopy ecosystems ability to mitigate greenhouse gases (GHG) is currently based on the rate of sedimentary organic carbon accumulation (CA) and the protection of vulnerable stocks from remineralisation. However, remineralisation of allochthonous inputs constrains CA as sequestration, assessments neglect remineralisation over climatic scales, and often fail to account for recalcitrant material. The article clarifies the meaning of stock and sequestration as mitigation services through their net ecosystem production (NEP) and addresses the concerns through a series of hypothetical evolving ecosystems. A diagenetic solution is proposed that accounts for continuous remineralisation of CA and the remineralised fraction of labile allochthonous inputs to estimate the NEP. The solution was applied and tested for a seagrass and mangrove ecosystem. Uncorrected and corrected average CA was greater than the cal. NEP values by a factor of two for the seagrass and 30 for the mangrove. Nevertheless, the NEP values fell within reported ranges i.e., 27.6 g C m-2 yr-1 (mangrove) and 7.2 g C m-2 yr-1 (seagrass). The overestimate was largely maintained after including vulnerable stocks in the total carbon accreditation calculus. However, with the inclusion of CA, the total average carbon mitigation rates converged to 1 124 (seagrass) and 1 783 g C m-2 yr-1 (mangroves), when argued, in some circumstances, as a vulnerable stock concept after hindcasting to their original time of annual deposition. Mitigation concepts and measurements require re-evaluation and will assure that carbon credits are not overvalued, which would otherwise permit GHG emissions above the capacity of the ecosystem.

Carbon dynamics at the river-estuarine transition: a comparison among tributaries of Chesapeake Bay

Sources and transformation of C were quantified using mass balance and ecosystem metabolism data for the upper segments of the James, Pamunkey and Mattaponi Estuaries. The goal was to assess the role of external (river inputs & tidal exchange) vs. internal (metabolism) drivers in influencing the forms and fluxes of C. C forms and their response to river discharge differed among the estuaries based on their physiographic setting. The James, which receives the bulk of inputs from upland areas (Piedmont and Mountain), exhibited a higher ratio of inorganic to organic C, and larger inputs of POC. The Pamunkey and Mattaponi receive a greater proportion of inputs from lowland (Coastal Plain) areas, which were characterized by low DIC and POC, and elevated DOC. We anticipated that transport processes would dominate during colder months when discharge is elevated and metabolism is low, and that biological processes would predominate in summer, leading to attenuation of C through-puts via de-gassing of CO2. Contrary to expectations, highest retention of OC occurred during periods of high through-put, as elevated discharge resulted in greater loading and retention of POC. In summer, internal cycling of C via production and respiration was large in comparison to external forcing despite the large riverine influence in these upper estuarine segments. The estuaries were found to be net heterotrophic based on retention of OC, export of DIC, low GPP relative to ER, and a net flux of CO2 to the atmosphere. In the James, greater contributions from phytoplankton production resulted in a closer balance between GPP and ER, with autochthonous production exceeding allochthonous inputs. Combining the mass balance and metabolism data with bioenergetics provided a basis for estimating the proportion of C inputs utilized by the dominant metazoan. The findings suggest that invasive catfish utilize 15 % of total OM inputs and up to 40 % of allochthonous inputs to the James.

THE ABUNDANCE OF KARST-RIPARIAN FOREST IN THE CATCHMENT AREA OF SAMPOLAWA RIVER BAUBAU, SOUTHEAST SULAWESI

<p>Riparian forest is a source energy and matter for the aquatic ecosystem. The abilities of riparian forest are to control and recycle the allochthonous inputs from the upland drainage basin and the river itself. This processess are a fundamental aspect of river ecology. We studied the riparian forest in karst ecosystem setting, at the protected forest of Sampolawa headwaters river, Baubau, Southeast Sulawesi. We focussed on the structure and composition of species richness of the forest. Data were collected using quadrate methods, 20mx20m, with 4 replicates placed at each river side. Results reveal that the forest compossed of 7 growth-forms, trees, saplings, seedlings, palm, herbs, liana, and spike moss. The tree species richness of tree and sapling was 33 and 37 species in consecutively. The tree species of Sphatolobus sp., Aglaia silvestris, and Canarium asperum dominated this riparian forest. Similarly the sapling dominance were Sphatolobus sp., Aglaia sp., and Chrysophyllum lanceolatum, as well as the seedlings of Sphatolobus sp., Palaquium obovatum and Chrysophyllum lanceolatum. Thus, the Sphatolobus sp. will be the future tree. However, Anthocephalus macrophyllus saplings were not found, thus this tree was endangered. Soil nutrients of NO3, NH4, PO4, and C organic were high, which indicated that the litterfall decomposition occurred at the forest riparian floor. The Riparian forest was a primary forest and very diversed in species richnes but had low densities. All the tree, sapling, and seedling species characterized the riparian forest of karst ecosystem at the headwaters of Sampolawa River in the karst ecosystem setting.</p><p><br /><strong>Keywords</strong>: Anthocephalus, karst-riparian forest, headwaters</p>