Assessing the Effect of Age and Geomorphic Setting on Organic Carbon Accumulation in High-Latitude Human-Planted Mangroves

Mangroves are highly productive blue carbon ecosystems that preserve high organic carbon concentrations in soils. In this study, particle size, bulk elemental composition and stable carbon isotope were determined for the sediment cores collected from the landward and seaward sides of two mangrove forests of different ages (M1, ca. 60; M2, ca. 4 years old) to determine the effects of geomorphic setting and age (L1 = old mangrove and S1 = salt marsh stand in M1; L2 = young mangrove and S2 = bare mudflat in M2) on sediments and organic carbon accumulation. The objective of this study was to determine the feasibility of the northernmost human-planted mangroves in China to accumulate sediment and carbon. Our results showed that fine-grained materials were preserved well in the interior part of the mangroves, and the capacity to capture fine-grained materials increased as the forest aged. The biogeochemical properties (C/N: 5.9 to 10.8; δ13C: −21.60‰ to −26.07‰) indicated that the local organic carbon pool was composed of a mixture of autochthonous and allochthonous sources. Moreover, the accumulation of organic carbon increased with the forest age. The interior part of the old mangrove had the highest organic carbon stock (81.93 Mg Corg ha−1). These findings revealed that mangrove reforestation had positive effects on sediments and organic carbon accretion.

Land Use/Land Cover (LU/LC) Changes and its impact on Soil Organic Carbon Stock in Killiar River Basin, Kerala, India: A Geospatial Approach

The changes in the pattern of land use and land cover (LU/LC) have remarkable consequences on ecosystem functioning and natural resources dynamics. The present study analyzes the spatial pattern of LU/LC change detection along the Killiar River Basin (KRB), a major tributary of Karamana river in Thiruvananthapuram district, Kerala (India), over a period of 64 years (1957-2021) through Remote Sensing and GIS approach. The rationale of the study is to identify and classify LU/LC changes in KRB using the Survey of India (SOI) toposheet (1:50,000) of 1957, LISS-III imagery of 2005, Landsat 8 OLI & TIRS imagery of 2021 and further to scrutinize the impact of LU/LC conversion on Soil Organic Carbon stock in the study area. Five major LU/LC classes, viz., agriculture land, built-up, forest, wasteland and water bodies were characterized from available data. Within the study period, built-up area and wastelands showed a substantial increase of 51.51% and 15.67% respectively. Thus, the general trend followed is the increase in built-up and wastelands area which results in the decrease of all other LU/LC classes. Based on IPCC guidelines, total soil organic carbon (SOC) stock of different land-use types was estimated and was 1292.72 Mt C in 1957, 562.65 Mt C in 2005 and it reduced to 152.86 Mt C in 2021. This decrease is mainly due to various anthropogenic activities, mainly built-up activities. This conversion for built-up is at par with the rising population, and over-exploitation of natural and agricultural resources is increasing every year.

Humus substances in the swamp ecosystems of taiga zone of Western Siberia

Eutrophic peatlands with a predominantly humate type of humus is dominated according to content of hydrophobic humus substances accumulated in the solid phase of peat. Oligotrophic peatlands with fulvate type of humus are characterized by minimal storages. Mesotrophic peatlands occupy a transitional position, both in terms of storage and in terms of the humus type – humate-fulvate. Hydrophilic components of the water phase are characterized by fulvate humus, regardless of the type of peatland, but differ in the proportion of the contribution of humus substances in the amphiphilic system of swamp ecosystems. It is the highest in the thickness of the oligotrophic peatland almost 31%, slightly lower in the mesotrophic – 25% and much less in the eutrophic – 6%. Structural features of macromolecules of humic acids of swamp waters of various genesis are determined. The humic acids of mesotrophic waters are adjacent to the group of reduced compounds, they are more enriched with aromatic structures and carboxyl groups in relation to oligotrophic waters. The humic acids of oligotrophic waters belong to a group of oxygenated compounds, have low enrichment of nitrogen, contain more methoxyl carbon and carbohydrates (polysaccharides). These structural features are caused by geochemistry of waters feeding the peatlands and specific mechanisms of humic acids synthesis on the swamps of different genesis. The volume of dissolved organic carbon stock from wetland ecosystems through system of taiga rivers of left bank of Middle Ob is 805 kt per year.

Aggregate characteristics and aggregate-associated soil organic carbon and carbohydrates of soils under contrasting tree land use

<p><span>Protection of soil organic carbon and acid-hydrolyzable carbohydrates in aggregate-size fractions is important for appraising soil degradation and aggregation under land use types. Aggregate-associated soil organic carbon (SOC) and acid-hydrolyzable carbohydrates (R-CHO) in bulk soils and aggregate-size fractions of a sandy loam soil under Alchornea bush, Rubber, Oil palm and Teak plantations in southern Nigeria were studied. Results revealed significant differences in aggregate-associated SOC and R-CHO, bulk densities, total porosity, soil organic carbon stock and aggregate stability among the land use types. Greater SOC was stored in macro-aggregates &gt;0.25 mm, while greater R-CHO was occluded in micro-aggregates &lt;0.25 mm (p&lt;0.05). The highest mean weight diameter (MWD) was 1.01 mm in Alchornea soils and 0.92 mm in Oil palm plantation at 0-15 cm topsoil. Soil organic carbon stock in 0-15 cm topsoil was 77.7, 81.8, 92.2, and 67.5 kg C ha^-1 in Alchornea, Rubber, Oil palm, and Teak soils, respectively. Relationships showed a positive linear correlations between MWD and SOC (r = 0.793, p &lt; 0.05) and R-CHO (r = 0.789. p &lt; 0.05). Alchornea bush and Oil palm plantation increased macro-aggregate formation and macro-pores &gt;5 µm, therefore they have greater potentials to boost protection of SOC in soil macro-aggregates.</span></p>