| Table 1. Summary of the main characteristics (including forest site type, soil nutrient status and type of dominant tree species) of the research sites included in the study (in Latvia). | ||||
| Drainage regime | Forest site type | Soil nutrient status, conditions | Type of dominant tree species | Number of research sites |
| Drained | Oxalidosa turf. mel. (Kp) | nutrient-rich, eutrophic | coniferous | 10 |
| deciduous | 2 | |||
| Myrtillosa turf. mel. (Ks) | moderate nutrient-rich, mesoeutrophic | coniferous | 17 | |
| deciduous | 6 | |||
| Naturally wet (undrained) | Dryopterioso-caricosa (Db), Filipendulosa (Lk) | nutrient-rich, eutrophic and mesoeutrophic | coniferous | 4 |
| deciduous | 4 | |||
| Caricoso-phragmitosa (Nd) | moderate nutrient-rich, mesotrophic | coniferous | 5 | |
| deciduous | 2 | |||
Fig. 1. Significance of peat subsidence in the calculation of soil carbon stocks.
Fig. 2. Subsidence of peat after drainage in different forest site types (Kp – Oxalidosa turf. mel.; Ks – Myrtillosa turf. mel.).
Fig. 3. Relationship between peat subsidence after drainage and distance from the ditch in forest stands with drained organic soils.
| Table 2. Soil bulk density (mean values ± confidence intervals, kg m–3) in different soil layers in hemiboreal forests in Latvia with drained and undrained organic soils depending on forest site type and type of dominant tree species. | ||||||
| Drainage regime | Forest site types | Type of dominant tree species | Soil layer | |||
| 0–10 cm | 10–20 cm | 20–40 cm | 40–80 cm | |||
| Drained | Oxalidosa turf. mel. (Kp) | all | 191.1 ± 10.05 | 190.3 ± 8.96 | 165.2 ± 9.58 | 156.5 ± 4.79 |
| deciduous | 190.7 ± 16.05 | 189.2 ± 15.18 | 184.1 ± 12.37 | 161.2 ± 4.13 | ||
| coniferous | 191.3 ± 13.69 | 191.1 ± 11.73 | 152.7 ± 11.86 | 153.4 ± 7.49 | ||
| Myrtillosa turf. mel. (Ks) | all | 165.2 ± 6.92 | 171.8 ± 6.57 | 155.2 ± 6.42 | 147.7 ± 6.82 | |
| deciduous | 176.2 ± 13.25 | 165.5 ± 13.50 | 151.9 ± 7.21 | 138.5 ± 7.49 | ||
| coniferous | 161.5 ± 7.83 | 173.9 ± 7.50 | 156.3 ± 8.24 | 150.8 ± 8.56 | ||
| Naturally wet (undrained) | Dryopterioso-caricosa (Db), Filipendulosa (Lk) | all | 159.8 ± 6.63 | 175.6 ± 6.75 | 160.2 ± 7.10 | 145.9 ± 8.21 |
| Caricoso-phragmitosa (Nd) | all | 121.8 ± 8.31 | 134.9 ± 8.38 | 155.9 ± 6.33 | 165.0 ± 4.21 | |
| All | All | deciduous | 181.1 ± 9.00 | 173.4 ± 9.35 | 162.6 ± 7.72 | 146.0 ± 5.25 |
| coniferous | 167.4 ± 6.95 | 177.3 ± 6.08 | 155.6 ± 6.28 | 151.3 ± 5.96 | ||
| Table 3. Carbon content (mean values ± confidence intervals, g kg–1) in different soil layers in hemiboreal forests in Latvia with drained and undrained organic soils depending on forest site type and type of dominant tree species. | ||||||
| Drainage regime | Forest site types | Type of dominant tree species | Soil layer | |||
| 0–10 cm | 10–20 cm | 20–40 cm | 40–80 cm | |||
| Drained | Oxalidosa turf. mel. (Kp) | all | 501.9 ± 4.1 | 524.7 ± 3.6 | 537.3 ± 8.4 | 538.3 ± 10.8 |
| deciduous | 497.0 ± 2.1 | 542.6 ± 0.8 | 543.9 ± 1.7 | 540.9 ± 3.5 | ||
| coniferous | 505.2 ± 2.9 | 512.8 ± 3.0 | 532.9 ± 5.8 | 536.5 ± 8.4 | ||
| Myrtillosa turf. mel. (Ks) | all | 520.9 ± 3.4 | 560.2 ± 4.1 | 569.9 ± 7.7 | 553.0 ± 11.7 | |
| deciduous | 504.8 ± 1.7 | 572.2 ± 3.5 | 577.2 ± 6.8 | 574.7 ± 3.9 | ||
| coniferous | 525.5 ± 5.3 | 559.1 ± 5.1 | 569.5 ± 10.0 | 544.7 ± 14.2 | ||
| Naturally wet (undrained) | Dryopterioso-caricosa (Db), Filipendulosa (Lk) | all | 478.6 ± 2.9 | 498.1 ± 2.9 | 521.2 ± 9.2 | 523.0 ± 20.0 |
| Caricoso-phragmitosa (Nd) | all | 527.6 ± 4.5 | 541.8 ± 5.3 | 575.0 ± 9.1 | 593.1 ± 18.5 | |
| All | All | deciduous | 502.2 ± 2.9 | 562.3 ± 4.1 | 566.1 ± 8.2 | 563.4 ± 9.2 |
| coniferous | 521.4 ± 3.5 | 549.8 ± 3.6 | 562.2 ± 6.9 | 543.0 ± 11.3 | ||
| Table 4. Soil pH (mean soil pH (CaCl2) values ± confidence intervals) in different soil layers in hemiboreal forests in Latvia with drained and undrained organic soils depending on forest site type and type of dominant tree species. | ||||||
| Drainage regime | Forest site types | Type of dominant tree species | Soil layer | |||
| 0–10 cm | 10–20 cm | 20–40 cm | 40–80 cm | |||
| Drained | Oxalidosa turf. mel. (Kp) | all | 4.7 ± 0.3 | 4.9 ± 0.3 | 5.0 ± 0.3 | 5.2 ± 0.2 |
| deciduous | 4.4 ± 0.6 | 4.4 ± 0.6 | 4.5 ± 0.6 | 5.0 ± 0.3 | ||
| coniferous | 4.9 ± 0.2 | 5.2 ± 0.3 | 5.3 ± 0.3 | 5.4 ± 0.3 | ||
| Myrtillosa turf. mel. (Ks) | all | 3.1 ± 0.1 | 3.3 ± 0.1 | 3.4 ± 0.1 | 4.2 ± 0.2 | |
| deciduous | 3.3 ± 0.2 | 3.3 ± 0.1 | 3.4 ± 0.1 | 4.4 ± 0.5 | ||
| coniferous | 3.1 ± 0.1 | 3.3 ± 0.2 | 3.4 ± 0.1 | 4.2 ± 0.2 | ||
| Naturally wet (undrained) | Dryopterioso-caricosa (Db), Filipendulosa (Lk) | all | 5.1 ± 0.2 | 5.0 ± 0.3 | 5.2 ± 0.3 | 5.0 ± 0.3 |
| Caricoso-phragmitosa (Nd) | all | 3.4 ± 0.3 | 3.2 ± 0.2 | 3.3 ± 0.2 | 3.4 ± 0.3 | |
| All | All | deciduous | 3.7 ± 0.3 | 3.7 ± 0.3 | 3.8 ± 0.3 | 4.6 ± 0.3 |
| All | coniferous | 3.5 ± 0.2 | 3.7 ± 0.2 | 3.8 ± 0.2 | 4.4 ± 0.2 | |
Fig. 4. Mean annual changes in soil carbon stock in drained organic soils over 53 years after drainage in Oxalidosa turf. mel. (Kp) and Myrtillosa turf. mel. (Ks) forest site types in Latvia.
| Table 5. Weighted mean CO2 emission factor for drained organic soils in forest land in Latvia based on distribution of different forest site types and emission factors obtained in the study. | |||||
| Parameters | Forest site types with drained organic soils | All forests with drained organic soils | |||
| Callunosa turf. mel. (Kv) | Vacciniosa turf. mel. (Km) | Myrtillosa turf. mel. (Ks) | Oxalidosa turf. mel. (Kp) | ||
| Total area in Latvia according to the results of the 3rd cycle of the NFI, kha | 19.9 | 68.5 | 242.1 | 91.4 | 421.9 |
| Emission factor, Mg CO2-C ha–1 yr–1 | 0.00 ± 1.24 | 4.98 ± 1.58 | 1.08 ± 1.31 | ||