Table 1.
Chemical characteristic of leaf litter and soil after 10 years of N addition in a larch plantation (mg g-1).
Fig 1.
Mass loss and decomposition constant k (the insets) of leaf litter among different input quantity treatments during incubation in the control and N fertilization microcosms.
Values are means (n = 5) ± SE. Different letters indicate significant differences (P<0.05) among treatments. CL1 soil + 1 g litter from control plots, CL2 soil +2 g litter from control plots, CL4 soil + 4 g litter from control plots, NL1 soil + 1 g litter from N addition plots, NL2 soil + 2 g litter from N addition plots, NL4 soil + 4 g litter from N addition plots.
Table 2.
Changes in litter mass loss, litter N remaining and cumulative CO2-C release of the control and N fertilization microcosms under different litter input quantity treatments after 270 days of incubation.
Fig 2.
Percent N remaining of leaf litter among different litter input quantity treatments during incubation in the control and N fertilization microcosms.
Values are means (n = 5) ± SE. CL1 soil + 1 g litter from control plots, CL2 soil +2 g litter from control plots, CL4 soil + 4 g litter from control plots, NL1 soil + 1 g litter from N addition plots, NL2 soil + 2 g litter from N addition plots, NL4 soil + 4 g litter from N addition plots.
Fig 3.
CO2 release rates and cumulative CO2-C release (the insets) among different litter input quantity treatments during incubation in the control and N fertilization microcosms.
Values are means (n = 5) ± SE. CL0 soil + 0 g litter from control plots, CL1 soil + 1 g litter from control plots, CL2 soil +2 g litter from control plots, CL4 soil + 4 g litter from control plots, NL0 soil + 0 g litter from N addition plots, NL1 soil + 1 g litter from N addition plots, NL2 soil + 2 g litter from N addition plots, NL4 soil + 4 g litter from N addition plots.
Fig 4.
Soil microbial biomass C (MBC; a and b) and microbial biomass N (MBN; c and d) among different litter input quantity treatments during incubation in the control and N fertilization microcosms.
Values are means (n = 5) ± SE. CL0 soil + 0 g litter from control plots, CL1 soil + 1 g litter from control plots, CL2 soil +2 g litter from control plots, CL4 soil + 4 g litter from control plots, NL0 soil + 0 g litter from N addition plots, NL1 soil + 1 g litter from N addition plots, NL2 soil + 2 g litter from N addition plots, NL4 soil + 4 g litter from N addition plots. In the insets, the means of MBC or MBN among different litter input treatments during the whole incubation time in the control and N fertilization microcosms are shown (n = 7).
Fig 5.
Soil dissolved organic C (DOC; a and b) and dissolved inorganic N (DIN; c and d) among different litter input quantity treatments during incubation in the control and N fertilization microcosms.
Values are means (n = 5) ± SE. CL0 soil + 0 g litter from control plots, CL1 soil + 1 g litter from control plots, CL2 soil +2 g litter from control plots, CL4 soil + 4 g litter from control plots, NL0 soil + 0 g litter from N addition plots, NL1 soil + 1 g litter from N addition plots, NL2 soil + 2 g litter from N addition plots, NL4 soil + 4 g litter from N addition plots. In the insets, the means of DOC or DIN among different litter input treatments during the whole incubation time in the control and N fertilization microcosms are shown (n = 7).
Fig 6.
The potential responses of soil carbon and nutrient cycling to changes in litter inputs under N addition.
The relationship between the response ratio of each parameter and the quantity of litter inputs is shown in parentheses. “+” indicates a positive correlation; “−” indicates a negative correlation; ns is non-significant. MBC microbial biomass carbon; MBN microbial biomass nitrogen; DOC dissolved organic carbon; DIN dissolved inorganic nitrogen.