Figure 1
Location of the study sites, Biebrza valley
Table 1
Mean values and standard deviations for the examined variables in four groups of soil data (n = 100). The same letters mean that differences between groups are not significant
| Group of soils with the SOC content (%) in the range | SOC | Ntot | SOM | DOC | DON | C/N | DOC/SOC | DON/Ntot |
|---|---|---|---|---|---|---|---|---|
| % | mg kg-1 | Min–max | % (min–max) | % | ||||
| 36–56 | 44.65d ±5.98 | 2.2d ±0.61 | 78.68d ±9.28 | 1741.1c ± 1469.6 | 115.23b ± 56.32 | 18–24 | 0.39 (0.07–0.63) | 0.52 |
| 16.1–35.9 | 28.61c ±6.05 | 1.73c ±0.63 | 50.54c ±16.3 | 1266.1bc ±831.7 | 109.05b ±63.32 | 15–21 | 0.44 (0.19–0.60) | 0.63 |
| 3.1–16 | 7.96b ±3.07 | 0.55b ±0.24 | 14.32b ±5.79 | 497.8ab ±383.4 | 31.04a ±16.26 | 14–16 | 0.62 (0.20–0.80) | 0.56 |
| 0.1–3 | 1.24a ±0.94 | 0.05a ±0.04 | 2.91a ±3.27 | 146.1a ±137.5 | 4.06a ± 2.51 | 24–30 | 1.17 (0.29–1.28) | 0.81 |
[i] Abbreviations: SOC, soil organic carbon; Ntot, total nitrogen; SOM, soil organic matter; DOC, dissolved organic carbon; DON, dissolved organic nitrogen
Figure 2
Relationships between values of soil organic carbon, soil organic matter, total nitrogen, dissolved organic carbon and dissolved organic nitrogen (SOC, SOM, Ntot, DOC and DON) using linear regression
Table 2
Pearson’s correlation coefficients for SOC, Ntot, SOM and DOC in the studied peat soils (all correlations were significant at p < 0.05)
| Parameters | SOC | Ntot | SOM | DOC |
|---|---|---|---|---|
| Ntot | 0.85 | |||
| SOM | 0.98 | 0.90 | ||
| DOC | 0.61 | 0.34 | 0.57 | |
| DON | 0.72 | 0.70 | 0.72 | 0.72 |
Table 3
Range of values for the soil parameters examined
| Soil property | Units | min (relative 0%) | max (relative 100%) |
|---|---|---|---|
| SOC | % | 0.16 | 56.1 |
| Ntot | % | 0.01 | 3.22 |
| SOM | % | 0.4 | 95.66 |
| DOC | mg kg−1 | 16.56 | 5287 |
| DON | mg kg−1 | 1.19 | 245.6 |
Figure 3
Relationship between relative value of soil organic carbon and soil organic matter based on linear regression
Figure 4
Relationship based on non-linear regression between relative value of A) soil organic carbon and total nitrogen, B) soil organic carbon and dissolved organic nitrogen and, C) soil organic carbon and dissolved organic carbon
Table 4
Changes in soil properties depending on relative values of SOC content within the range from 0% to 50%
| SOC (%) | 50 | 40 | 30 | 20 | 10 | 0 |
|---|---|---|---|---|---|---|
| Ntot | 59.06 | 47.12 | 33.73 | 20.42 | 8.67 | 0.00 |
| ΔNtot | 11.94 | 13.38 | 13.32 | 11.75 | 8.67 | |
| SOM | 51.40 | 41.12 | 30.84 | 20.56 | 10.28 | 0.00 |
| ΔSOM | 10.28 | 10.28 | 10.28 | 10.28 | 10.28 | |
| DON | 41.65 | 34.53 | 26.33 | 17.52 | 8.58 | 0.00 |
| ΔDON | 7.12 | 8.20 | 8.81 | 8.94 | 8.58 | |
| DOC | 19.24 | 18.58 | 17.58 | 14.99 | 9.55 | 0.00 |
| ΔDOC | 0.66 | 1.00 | 2.59 | 5.44 | 9.55 |
Table 5
Changes in soil properties depending on relative values of SOC content within the range from 20% to 30%
| SOC (%) | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| N tot (%) | 33.73 | 32.37 | 31.02 | 29.66 | 28.31 | 26.97 | 25.64 | 24.31 | 23.00 | 21.70 | 20.42 |
| ΔNtot (%) | 1.36 | 1.36 | 1.35 | 1.35 | 1.34 | 1.33 | 1.32 | 1.31 | 1.30 | 1.29 | |
| SOM (%) | 30.84 | 29.81 | 28.78 | 27.76 | 26.73 | 25.70 | 24.67 | 23.64 | 22.62 | 21.59 | 20.56 |
| ΔSOM (%) | 1.03 | 1.03 | 1.03 | 1.03 | 1.03 | 1.03 | 1.03 | 1.03 | 1.03 | 1.03 | |
| DON (%) | 26.33 | 25.47 | 24.60 | 23.73 | 22.85 | 21.97 | 21.09 | 20.20 | 19.31 | 18.41 | 17.52 |
| ΔDON (%) | 0.86 | 0.87 | 0.87 | 0.88 | 0.88 | 0.88 | 0.89 | 0.89 | 0.89 | 0.89 | |
| DOC (%) | 17.58 | 17.42 | 17.23 | 17.03 | 16.81 | 16.57 | 16.30 | 16.01 | 15.70 | 15.36 | 14.99 |
| ΔDOC (%) Table | 4 | 0.17 | 0.18 | 0.20 | 0.22 | 0.24 | 0.26 | 0.29 | 0.31 | 0.34 | 0.37 |