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The properties of secondary salt-affected soils developed from improper irrigation and drainage management and their effects on rice growth and yield are well documented. However, relevant informat...

Elevated CO2 concentration ([CO2]) and air temperature (Tair) as well as changed soil water availability (Wsoil) may affect quantity, chemistry, and microbial decomposability of tree leaf litter. However, our understanding is limited mainly to the effect of elevated [CO2]. This study investigated the effects of elevated [CO2] and Tair in combination with two Wsoil regimes on the quantity and chemistry including the ratio of lignin to nitrogen (lignin/N) of litter produced by Pinus densiflora and Quercus variabilis saplings, and microbial respiration of the soils amended with the litters. Either elevated [CO2] or high Wsoil alone increased litter production; meanwhile elevated Tair alone decreased litter production. However, co-elevation of [CO2] and Tair did not change litter production regardless of Wsoil regime for both species. Among litter chemistry, the lignin/N, which is a robust indicator of litter decomposability, of litter was changed in parallel with litter quantity (i.e., lignin/N ratio increased when litter quantity increased and vice versa) mainly due to dilution of N. Due to the opposite effect of warming and elevated [CO2] on litter quantity, lignin/N was not changed under co-elevated [CO2] and Tair at a given Wsoil regime for both species. Other litter chemistry including non-structural carbohydrates and minerals was also affected by [CO2], Tair, or Wsoil. However, changed litter chemistry did not change the CO2 emission from the soils amended with the litters; however, addition of litter with low lignin/N and high nutrients increased microbial biomass in the soil. This study enlarges our understanding of the effects of changed climatic variables on litter quantity, chemistry, and microbial decomposability and suggests that co-elevation of [CO2] and Tair may not cause a significant change in the litter parameters regardless of Wsoil. Study with mature trees at a natural forest should further improve our understanding.

Waterlogged paddy and water-unsaturated upland ecosystems have contrasting soil nitrogen (N) processes that affect the natural 15N abundance (15N/14N, expressed as δ15N) in different N pools. In this study, we investigated the δ15N patterns in soil and plant N pools of paddy and upland ecosystems. Samples were collected from 20 each of paddy and upland fields at the active growing season and analyzed for N concentration and δ15N. The higher (P

Only limited information is available in the research area on the effect of elevated CO2 concentration ([CO2]) and air temperature (Tair) on the fertilizer N uptake by rice. This study was conducted to investigate changes in rice uptake of N derived from fertilizer (NDFF) and soil (NDFS) as well as fertilizer N uptake efficiency (FUE) with elevated [CO2] and Tair in two soils with different fertility. Rice (Oryza sativa L.) plants were grown with 15N-urea for two growing seasons (2007 in the less fertile and 2008 in the more fertile soil) in temperature gradient chambers under two (ambient and elevated) levels of [CO2] and Tair regimes. At harvest, dry matter (DM) and N uptake amount of rice compartments (root, shoot, and grain) were determined. The DM of whole rice increased (P

Fly ash can reduce CO2 emission from soils via biochemical (i.e., inhibition of microbial activity) and physicochemical (i.e., carbonation) mechanisms. This study investigated the effects of fly ash amendment on biochemical and physicochemical reduction in CO2 emission from normal and saline soils. The physicochemical mechanisms of reduction in CO2 emission by fly ash were estimated in a batch experiment with carbonate solution as a CO2 source by the scanning electron microscope (SEM) and inductively coupled plasma analyses. Biochemical mechanisms of reduction in CO2 emission by fly ash were investigated in a 3-day laboratory incubation experiment with normal and saline soils in the absence and presence of fly ash. Finally, the effects of fly ash amendment at a variety rate from 2 to 15 % (w/w) on CO2 emission from normal and saline soils in the presence of additional organic carbon source (glucose) were investigated through a 15-day laboratory incubation study. In the batch experiment with carbonate solution, both the SEM image of fly ash and changes in soluble Ca and Mg concentrations during reaction with carbonate suggested that the formation of CaCO3 and MgCO3 via carbonation was the principal physicochemical mechanism of carbonate removal by fly ash. In the 3-day incubation study conducted to examine biochemical mechanisms of reduction in CO2 emission by fly ash, microbial respiration of saline soil was inhibited (P

Purpose Since substrate quality can influence the C mineralization pattern of compost in soils, proper selection of compost is important in increasing soil organic carbon (SOC) levels. This study investigated the effect of substrate quality of livestock manure composts on compost C mineralization and retention in soils.

BACKGROUND: Soil acidification, which is known to be one of the reasons of forest decline, is associated with decreases in exchangeable Ca and increases in Al concentration, leading to low Ca/Al ratio in soil solution. As tree rings are datable archives of environmental changes, Ca/Al ratios of annual growth ring may show decreasing pattern in accordance with the progress of soil acidification. This study was conducted to investigate Ca/Al pattern of Pinus densiflora tree ring in an attempt to test its usefulness as an indicator of historical soil acidification. METHODS AND RESULTS: Three P. densiflora tree disks were collected from P. densiflora forests in Jeonnam province, and soil samples (0-10, 10-20, and 20-30 cm in depth) were also collected from the tree locations. Soils were analyzed for pH and exchangeable Ca and Al concentrations, and Ca/Al was calculated. Annual growth rings formed between 1969 and 2007 were separated and analyzed for Ca/Al. Soil Ca/Al was positively (P

BACKGROUND: Application of urea may increase CO2 emission from soils due both to CO2 generation from urea hydrolysis and fertilizer-induced decomposition of soil organic carbon (SOC). The objective of this study was to investigate the effects of increasing urea application on CO2 emission from soil and mineralization kinetics of indigenous SOC. METHODS AND RESULTS: Emission of CO2 from a soil amended with four different rates (0, 175, 350, and 700 mg N/kg soil) of urea was investigated in a laboratory incubation experiment for 110 days. Cumulative CO2 emission (Ccum) was linearly increased with urea application rate due primarily to the contribution of urea-C through hydrolysis to total CO2 emission. First-order kinetics parameters (C0, mineralizable SOC pool size; k, mineralization rate) became greater with increasing urea application rate; C0 increased from 665.1 to 780.3 mg C/kg and k from 0.024 to 0.069 day -1 , determinately showing fertilizer-induced SOC mineralization. The relationship of C0 (non-linear) and k (linear) with urea-N application rate revealed different responses of C0 and k to increasing rate of fertilizer N. CONCLUSION(s): The relationship of mineralizable SOC pool size and mineralization rate with urea-N application rate suggested that increasing N fertilization may accelerate decomposition of readily decomposable SOC; however, it may not always stimulate decomposition of non-readily decomposable SOC that is protected from microbial