『Abstract
　Surface and subsurface litter fulfil many functions in the biogeochemical cycling of C and N in terrestrial ecosystems. These were explored using a microcosm study by monitoring dissolved inorganic nitrogen (DIN) (NH4⁺-N + NO3^--N), dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) concentrations and fluxes in drainage water under ambient outdoor temperatures. Subsurface litter remarkably reduced the DIN concentrations in winter, probably by microbial N uptake associated with higher C:N ratio of added litter compared with soil at 10-25 cm depth. Fluxes of DIN were generally dominated by NO3^--N; but NH4⁺-N strongly dominated DIN fluxes during freeze-thaw events. Appreciable concentrations of NH4⁺-N were observed in the drainage from the acid grassland soils throughout the experiment, indicating NH4⁺-N mobility and export in drainage water especially during freeze-thaw. Litter contributed substantially to DOC and DON production and they were correlated positively (p＜0.01) for all treatments. DOC and DON concentrations correlated with temperature for the control (p＜0.01) and surface litter (p＜0.001) treatments and they were higher in last summer. The subsurface litter treatment, however, moderated the effect of temperature on DOC and DON dynamics. Cumulative N species fluxes confirmed the dominance of litter as the source of DON and DOC in the drainage water. DON constituted 42, 46 and 62% of cumulative TDN flux for control, surface litter and subsurface litter treatments respectively.

Keywords: Litter; Dissolved organic carbon (DOC); Dissolved organic nitrogen (DON); Dissolved inorganic nitrogen (DIN); Seasonal variations; Grassland』

Introduction
Materials and methods
　Characteristics of the study site
　Litter and soil sampling and preparation
　Microcosm construction and experimental set up
　Simulated rain preparation, application and drainage water collection
　Analytical protocols
　　Litter and soil initial physico-chemical characteristics
　　Weekly drainage water analysis and flux calculations
　Statistical analysis
Results
　Initial physico-chemical characteristics of litter and soils
　Litter effects on drainage water N dynamics
　　Changes in NO3^--N concentrations
　　Changes in NH4⁺-N concentrations
　　Changes in DIN concentrations
　　Changes in DON concentrations
　　Changes in TDN concentrations
　Litter effects on drainage water DOC concentrations
　Drainage water DIN, DON and DOC fluxes
　Temperature regulation of drainage water DON and DOC dynamics
　Relationships of DIN, DON and DOC concentrations with pH, EC, SO4^-2 and Cl^-
　Net cumulative N and C flux balances in drainage water
Discussion
　Litter effects on DIN concentrations and fluxes
　Litter effects on DOC and DON dynamics
　Seasonal variations and apparent effects of temperature
　Temperature effects on DOC:DON and DON:DIN ratios
　Inter-relationships of DIN, DON and DOC concentrations
　Relationships of DON and DOC concentrations with pH and EC
　Cumulative N and C fluxes and net budgets
　How useful is it measure weekly fluxes and design a short-term study?
Conclusions
Acknowledgments
References