Fig. 1. Schematic illustrations of site preparation methods considered in the study. Planting with no site preparation (No MSP; top left), and after; patch scarification (top right), disc trenching (middle left), mounding (middle right), soil inversion (bottom left) and ploughing (bottom right). For further explanation, see section 2. Illustrations are made by Rose-Marie Rytter.
| Table 1. Survival rates (%) of planted Norway spruce (Ns), Scots pine (Sp) and lodgepole pine (Lp) seedlings following each mechanical site preparation method (MSP) and No MSP, in field experiments and survey studies obtained 3–27 growing seasons after planting. The character ~ indicates values estimated from a diagram and * in “No MSP” that statistical analysis was reported in that study. Bold values indicate a statistically significant difference from the control (“No MSP”) and values in brackets show differences in percentage units in relation to “No MSP”. In most experiments, the planted seedlings were protected by an insecticide to reduce pine weevil (Hylobius abietis L.) damage. In experiments where both protected and unprotected seedlings were planted values are shown for both types. View in new window/tab. |
| Table 2. Mean heights (cm) of planted Norway spruce (Ns), Scots pine (Sp) and Lodgepole pine (Lp) seedlings following each mechanical site preparation method (MSP) and No MSP, in field experiments and survey studies obtained 3–27 growing seasons after planting. The character ~ indicates values estimated from a diagram and * in ”No MSP” that statistical analysis was reported in that study. Bold values indicate a statistically significant difference from the control (“No MSP”) and values in brackets show differences in percentage relative to “No MSP”. In most experiments, the planted seedlings were protected by an insecticide to reduce pine weevil (Hylobius abietis L.) damage. In the experiments where both protected and unprotected seedlings were planted values are shown for both types. View in new window/tab. |
| Table 3. ANOVA results for the effects of mechanical site preparation method (MSP method; least-square means (lsmeans) ± stderr) of planted Norway spruce, Scots pine and lodgepole pine seedlings following each MSP method in field experiments. Survival (%) refers to analyses of the survival of all MSP treatments, as well as of the MSP-effects, i.e. the difference in percentage units between results of the MSP methods and no site preparation (No MSP). For height, both the absolute tree heights (cm) in all treatments and the relative MSP-effects are given. The relative MSP-effect on height and annual height growth refers to the difference in percentage (%) between results of the MSP methods and No MSP. Data obtained 3–27 growing seasons after planting. Values with different letters in the same row indicate statistically significant differences (p < 0.05) for tree species and MSP-method, respectively. NO MSP DATA = studies including a control treatment without MSP. View in new window/tab. |
Fig. 2. Survival of Norway spruce (Ns), Scots pine (Sp) and Lodgepole pine (Lp) seedlings planted after indicated MSP methods (PATCH = patch scarification, DISC = disc trenching, MOUND = mounding, INV = soil inversion, PLOUGH = ploughing) as functions of temperature sum (degree days °C; threshold 5 °C) at locations of the studies (upper panel), and time after planting (lower panel). Data from all experimental studies summarized in Table 1 (ALL DATA; n = 62), each of which included observations at 1–10 experimental sites.
Fig. 3. Effects on survival of indicated mechanical site preparation methods (MSP effects, i.e. differences between each method and no MSP: PATCH = patch scarification, DISC = disc trenching, MOUND = mounding, INV = soil inversion, PLOUGH = ploughing) of subsequently planted Norway spruce (Ns), Scots pine (Sp) and lodgepole pine (Lp) seedlings as functions of temperature sum (Ts; degree days °C, threshold 5 °C) at locations of the studies (upper panel), and time after planting (T) (lower panel). Data from studies presenting experimental data summarized in Table 1 including No MSP treatment (NO MSP DATA; n = 46), each of which included observations at 1–10 experimental sites.
Trend = 15.5 + 0.002 × Ts; R2 = 0.01; p = 0.57 (upper panel).
Trend = 19.7 – 0.199 × T; R2 = 0.02; p = 0.37 (lower panel).
Fig. 4. Survival of Norway spruce (Ns) and Scots pine (Sp) seedlings, without and with chemical treatment against pine weevil (Hylobius abietis L.), planted after indicated mechanical site preparation (MSP) methods. Lsmeans ± standard error. Data from six experimental studies in Table 1 (five Ns and one Sp; n = 28), each of which included observations at 1–4 experimental sites. Values with different letters within MSP method indicate statistically significant differences (p < 0.05) for pine weevil treatment.
Fig. 5. Effects on height of indicated mechanical site preparation methods (MSP effects: PATCH = patch scarification, DISC = disc trenching, MOUND = mounding, INV = soil inversion, PLOUGH = ploughing) of planted Norway spruce (Ns), Scots pine (Sp) and lodgepole pine (Lp) seedlings as functions of temperature sum (upper panel) and time after planting (lower panel). Data from the studies presenting experimental data summarized in Table 2 including No MSP treatment (NO MSP DATA; n = 36), each of which included observations at 1–10 experimental sites. For further explanations, see Fig. 3.
Poly = –41.2 + 0.227 × Ts – 0.00014 × Ts2; R2 = 0.25; pmodel = 0.008 (upper panel).
Poly = –39.4 + 17.2 × T – 0.757 × T2; R2 = 0.30; pmodel = 0.003 (lower panel).
| Table 4. Disturbed soil surface area (%) following each mechanical site preparation method (MSP) and No MSP. | ||||||
| No MSP | Patch scarification | Disc trenching | Mounding | Soil inversion | Ploughing | Reference |
| 49 | 50 | 60 | Pohtila and Pohjola (1985)1 | |||
| 54 | 35 | 69 | Bäcke et al. (1986)2 | |||
| 20–30 | Adelsköld (1986)3 | |||||
| 40–47 | 53–58 | Saksa (1987)4 | ||||
| 70 | 30 | von Hofsten (1989)5 | ||||
| 52–67 | von Hofsten (1991)6 | |||||
| 9 | 50 | Karlsson et al. (2002)7 | ||||
| 35 | von Hofsten and Nordén (2002)8 | |||||
| 61 | Nilsson et al. (2002)9 | |||||
| 14 | 55 | 51 | Hallsby and Örlander (2004)10 | |||
| 17–19 | Lehtosalo et al. (2010)11 | |||||
| 33 | 22 | Sjögren (2013)12 | ||||
| 1 A study in N Finland including eight experiments, four established in former Scots pine-dominated forest and four in former Norway spruce-dominated forest. Split-plot experiments, four site preparation methods (patch created by a scarifier; disc trenching by a TTS–35 disc trencher; ploughing by a ridge plough or a shoulder-plough). The disturbed soil surface area was measured in a circular plot (200 m2) within each treatment plot (12 000 m2) and values presented are means per MSP-treatment. 2 Means for five sites in Northern Sweden, inventoried along parallel lines. Mounding was done with an aggregate from Bracke (Bräcke mounder; at least 10 l soil placed on upturned humus) and disc trenching with a ”Murveln disc trencher” manufactured by Järvsö Skogsmekan, and ploughing with Marttini and Lönntek ploughs. See also Mattsson and Bergsten (2003). 3 Site preparation in different terrains. Two types of mounding equipment were used: Bracke and Donhög 190, which affected 20–25% and 25–30% of the surface area, respectively, in both cases with 2 m spacing between rows. 4 Practical reforestation areas with disc trenching done by TTS-disc trenchers and ploughing, mainly by shoulder-ploughs. The disturbed soil surface area was measured in ca. 50 circular plots per plantation, the plots 6 m2 or 10 m2 depending on the density of the plantation. Values presented are means of the monitored regeneration areas per MSP-method. 5 A Donaren 230 MIDAS disc trencher was used both continuously (disc trenching) and patch wise (mounding). 6 Three different site types were evaluated, following use of a Bracke aggregate creating both long patches ending with a mound (n = 1), and large mounds (n = 2). The distance between the rows with mounds was ca. 2 m. The disturbed area was calculated as the total distance monitored, minus the unaffected distance between the mounds, multiplied by the mean width of the mounds. 7 Mounding was performed using an excavator at four sites in southern Sweden. The mounds were made of 20 dm3 mineral soil and were 10–20 cm high. Presented data are means for four sites, min–max, control 4–17% and mound 41–55%. 8 A combined site preparation aggregate (GSSP97) that could be used either for mounding (the data presented here) or patch scarification was used. 9 In this study, 8% was recorded as pure mineral soil and 53% as berm, after disc trenching. 10 Site preparation completed with an excavator. The site prepared spots had areas of ca. 0.5 m2 and a 0.1–0.2 m deep layer of mineral soil covered the buried humus. Mound spacing ca. 2 m. The total area of disturbed soil surface is given. With soil inversion, there was less variation in occurrence of altered surface contours than with mounding. Average for 12 sites. 11 9–10% of the surface area recorded as ”mounds” and 8–9% as ”patches”. Means for 18 monitored sites. 12 Disc trenching equipment not specified. Mounding was done with a Bracke Planter. Three sites per method were monitored. | ||||||
| Table 5. Number of naturally regenerated seedlings (mainly birch) per hectare following each mechanical site preparation method (MSP, i.e. disc trenching, mounding, soil inversion and patch scarification) and No MSP. The total area column presents densities in the whole regeneration areas, both affected and not affected by MSP. The affected area column presents densities for different MSP methods only in the area disturbed by the MSP. Data from field experiments and surveys of stands established in operational forestry, recorded 3–14 growing seasons after planting. View in new window/tab. |