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We developed a phenology-based growth model(PG model) for Spartina alterniflora that incorporates the effects of light, temperature, and salinity on plant production. The PG model is the first to quantify carbon translocation between both above- and below-ground biomass across three phenological periods: growth, senescence, and dormancy periods. This model, fitted to field data from short, medium, and tall S. alterniflora types, estimates physiological parameters such as mass-specific rates of carbon translocation. Once parameterized, the model is applied in forward mode to predict whole-plant production, growth, respiration, mortality, and translocation. Model results reveals that short forms allocate 82 % of photosynthate to below-ground biomass during the growing season, compared to tall (52 %) and medium (22 %) types. However, tall forms, with extensive above-ground biomass, show the highest absolute carbon translocation to below-ground tissues during growth(ave. 3940 g dry weight m−2) and senescence(ave. 265 g dry weight m−2) period. An average mortality rate of 52 % of net production in the tall form below-ground biomass throughout the year indicates a substantial contribution to organic carbon sequestration within the habitat sediment. Model results also reveal that the carbon translocation from below- to above-ground tissues may not be required for survival during winter in milder climate like Sapelo Island, Georgia. • The first Phenology-based Growth model(PG model) for Spartina incorporates salinity effects. • The short form allocating the most photosynthate below-ground during growing season. • High below-ground biomass mortality in the tall form implies significant carbon sequestration. • Carbon translocation from below- to above-ground tissues negligible in all forms in Georgia. • Spartina in milder climates may not rely on below-ground reserves for winter survival. [ABSTRACT FROM AUTHOR]

Studies suggest that intensively tilled soils have lost 25–75% of their original soil organic C (SOC) content. No tillage (NT) can restore SOC in response to increased C inputs and reduced soil disturbance. Organic amendments provide faster recovery of SOC, ultimately promoting the saturation of soil layers. Here we present evidence of additional SOC accrual through translocation of SOC after saturation of the topsoil layer in a NT soil. Both processes were observed in a long-term (25 yr.) experiment comparing soil tillage systems (chisel tillage − CT, and NT) in central Kansas. Plots with continuous corn were amended with mineral (MF) and organic N (OF), in addition to a control treatment without N fertilization (CO). Accumulation of SOC was limited to the surface layer (0–5 cm) of the NT soil amended with MF. Organic fertilization increased SOC in the 0–5 cm soil layer from 9.5 Mg C ha −1 to a level of 16.2 and 30.2 Mg C ha −1 in CT and NT, respectively. Further analysis confirmed the saturation of physically protected SOC in the surface of NT soil under organic amendments. After saturation, significant SOC accrual (1.3 Mg C ha −1 yr −1 ) was observed in the 5–15 cm soil layer. Isotopic assessment confirmed the occurrence of SOC translocation between saturated and C-depleted NT soil layers. No evidence of SOC translocation was observed between non-saturated soil layers. Further research is needed to elucidate the mechanisms regulating this process. Nonetheless, SOC translocation and subsequent SOC accrual suggests a greater C sink potential for NT soils than previously thought. [ABSTRACT FROM AUTHOR]

Insufficient leaf photoassimilation could allow mobilized carbohydrate reserves to contribute to berry sugar accumulation. However, the extent of this contribution during rapid and slow berry sugar accumulation is undefined. The potential effect of leaf-to-fruit ratio and water availability on carbohydrate reserve distribution in potted Tempranillo grapevines was examined during berry maturation. Within each leaf-to-fruit ratio treatment (full and 50% leaves), vines were grown under full or 50% reduced irrigation regimes. Dry biomass development, and the starch and soluble sugar concentrations were determined in the roots, trunks, stems and leaves. Berry sugar and anthocyanin accumulation were also assessed. Under full irrigation, no starch remobilization from roots was observed, regardless of the leaf-to-fruit ratio. Under reduced water supply, starch remobilization from roots was concurrent with rapid berry sugar accumulation, especially in grapevines with low leaf-to-fruit ratio. Soluble sugar accumulation coincided with starch depletion in the roots of grapevines under reduced water availability. When berry sugar accumulation slowed, an increase in carbohydrates was observed in the roots. Sustained water constraints during rapid berry sugar accumulation resulted in a forced reliance on stored carbohydrates to support berry sugar accumulation, but did not significantly alter the tempo of berry sugar and anthocyanin accumulation. A reduced leaf-to-fruit ratio intensified the reliance of fruit sugar accumulation on stored carbohydrates. Besides the importance of post-harvest carbohydrate reserve replenishment when root carbohydrate reserves are depleted during berry maturation, the reserves are also refilled during maturation when berry sugar accumulation slows. This study showed distinctly that root carbohydrate replenishment could already start a few weeks before harvest, and this replenishment could be important when the post-harvest carbon assimilation period is ineffective. [ABSTRACT FROM AUTHOR]

New Zealand is currently identifying and quantifying its carbon sources and sinks to develop a national carbon budget. This will enable it to set policy and targets to reduce greenhouse gas emissions in line with the Kyoto Protocol. While soil is a major carbon sink, New Zealand also has high sediment yields to the ocean, suggesting that erosion has a significant effect on soil carbon fluxes, through CO2 emission during transport of carbon in sediment, carbon burial and recovery of carbon on eroded areas.As a contribution to the national carbon budget, a mass balance approach was used to calculate soil carbon fluxes from landslide and sheetwash erosion in the Tutira catchment in the North Island of New Zealand. This soft rock hill country catchment represents the upper limit for landslide-related soil carbon losses. It contains a lake that acts as a highly efficient trap for sediment and nutrients, and has preserved a high-resolution record of storm-induced erosion. Information from previous studies of erosion and lake sedimentation was used to construct a carbon budget for the 114-year period of European pastoral farming. The budget assumes the gross transfer of carbon by geomorphological processes and does not include biogeochemical exchanges with the atmosphere.Results indicate that 0.94±0.23 Mg C ha-1 per year enter the lake (0.50±0.15 Mg C ha-1 per year from landslide erosion and 0.44±0.17 Mg C ha-1 per year from sheetwash erosion). On a national scale this equates to an anthropogenically induced loss of 2 112 000 Mg C per year from the 10% of similar terrain under pastoral land use. However, the net loss from the landscape is significantly less due to carbon recovery on eroded sites. Landslide scars have a carbon recovery rate (after oxidation) of ∼0.61 Mg C ha-1 per year. Carbon recovery on areas affected solely by sheetwash erosion was not measured, but is significantly lower. This information is being used to constrain models of erosion-related carbon fluxes developed for landslide-prone terrains, as part of the national carbon budget. [Copyright &y& Elsevier]