Varying rectangular spacing yields no difference in forest growth and external wood quality in coniferous forest plantations

Ara, Mostarin; Barbeito, Ignacio; Elfving, Björn; Johansson, Ulf; Nilsson, Urban

doi:10.1016/j.foreco.2021.119040

Cited by 5 publications

(3 citation statements)

References 13 publications

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“…The tree species diversity in our stands were intentionally low, which sets them apart from the intended conifer forests up for thinning in the coming years will have a higher share of broadleaves. The initial spacing in future forests might also vary across the stands as the importance of proper planting spots outcompete the importance of equal spacing (Ara, Barbeito, Elfving, et al, 2021).…”

Section: Within-stand Variation Before Thinningmentioning

confidence: 99%

Evaluating thinning practices and assessment methods for improved management in coniferous production forests in southern Sweden

Persson¹

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Most of our knowledge about wood production of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) and associated silvicultural guidelines are based on field experiments. These have been established in rather small, homogenous stands. In practical forestry there is probably a comparatively larger gradient in within-stand variation due to varying site conditions and less controlled silviculture than in experiments. The extent of the within-stand variation in coniferous production stands and how thinning guides are used in relation to the within-stand variation, is not well understood. Also, the freely available Forest resource maps (sv. Skogliga grunddata) and satellite data offer the possibility to accounts for the within-stand variation in forest management, but this is also poorly researched. This thesis evaluates within-stand variation at first thinning: its extent, its effect on silviculture and its importance for future stand development. Additionally, optical satellite data from Sentinel-2 is used to detect thinning operations, estimate growth after thinning and classify tree species. The thesis is mainly based on a survey carried out in the fall of 2018 in planted conifer-dominated production stands planned for first commercial thinning in which the thinning method of the forest workers was observed. The survey was inventoried directly after thinning and three growing seasons later. The survey showed an unprecedented within-stand variation before thinning in stem volume, stem density, dominant height, mean height quadratic mean diameter and basal area. The thinning operations did not reduce the within-stand variation in any of the attributes measured with the relative standard deviation. The stands were thinned heavily, and the harvested basal area increased with basal area before thinning at sample plot level, which suggest an ambition to reduce the variation. The stands were also monitored using Sentinel-2 satellite data. The thinning detection model separated unthinned, lightly thinned and heavily thinned sample plots with a moderate overall accuracy of 62% (Kappa of 0.34). A set of satellite images over the whole observation period was used estimate the periodical annual volume increment after thinning and did so with a root mean squared error (RMSE) of 1.8 m3 ha-1 y-1 (relative RMSE: 24%). The long-term effects of optimizing the thinning regime on pixel level versus conventional stand-level thinning was evaluated using the Heureka system. No benefits in terms of stand economy or production was found, but the within-stand variation in basal area decreased over the rotation. Tree-species classification, rendering maps with the dominant tree species at pixel level over a forest holding, were made using multi-temporal Sentinel-2 satellite data and the Random Forest classifier. The major tree species in the forest holding were Scots pine, Norway spruce, Pedunculate oak (Quercus robur), Birch (Betula spp.) and Hybrid larch (Larix × marschlinsii). These species were classified with a high overall accuracy of 88.2% (Kappa of 0.82). This thesis illustrates that considerable within-stand variation could be expected before and after first thinning for coniferous dominated stands in southern Sweden. The average stand basal area after thinning was consistently lower than the required basal area in the thinning guides from the Swedish Forest Agency, which means that reduced total production over the rotation may be a result. The increasing harvested basal area with basal area before thinning, suggests an ambition to reduce the within-stand variation in basal area. Thinning at the pixel level by adapting the thinning regime to the within-stand variation did not have any long-term effects on stand economy or volume production compared to conventional stand-level thinning. Despite the non-significant results, high-resolution maps are probably needed anyway to support forest workers in thinning operations to avoid heavy thinning. The Sentinel-2 satellite data proved its relevance for practical forestry for thinning detection, assessing growth after thinning, and classifying tree species. These methods can be used in combination the already existing Forest resource maps to reduce uncertainties for the management of planted forest.

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Section: Within-stand Variation Before Thinningmentioning

confidence: 99%

Evaluating thinning practices and assessment methods for improved management in coniferous production forests in southern Sweden

Persson¹

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“…Nevertheless, it is important to take the entirety of the rotation period into account to get a clear picture of the pros and cons of a given management option (Ahtikoski et al, 2010;Uotila et al, 2010;Dahlgren Lidman et al, 2021), especially if considering that the establishment cost is not realized in the harvested crop trees due to damage or other circumstances. Ara et al (2021) showed that regeneration of Scots pine in Sweden often result in a mixture of the desired crop species and natural regeneration, deeming this as a failure given that the end goal was Scots pine dominated stands. Loss of invested seedlings in the future stand has also been shown in other studies (Holmström et al, 2019;Gålnander et al 2020), further emphasizing the issue of wasted investment in planted seedlings.…”

Section: Long-term Effectsmentioning

confidence: 99%

“…Stoniness or wet conditions can make this difficult, putting more emphasis on adapting the choice of method to the conditions and executing site preparation in areas that are more suitable (Wallertz et al, 2018). Allowing more flexibility in planting design and seedling spacing could support better adaptability to local site conditions and has been shown to not affect conifer tree growth (Ara et al, 2021).…”

Section: Effect Of Site Preparationmentioning

confidence: 99%

Regeneration measures in time and space: Site preparation, planting and digital tools

Nordin¹

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Regeneration success depends on decisions made based on factors on aregional, site, and microenvironmental level. Therefore, understanding andmapping of such factors between and within sites can guide decisions forbetter seedling establishment. Thus, the aim of this thesis was to findcombinations of regeneration measures that result in low seedling mortalityand high growth. Additionally, to explore the potential of digital tools inregeneration planning. Aims were handled using field experiments and asurvey, by integrating digital tools in the analysis and experimental set-up. Increased precipitation and decreased air temperatures between April andOctober during the planting year lowered seedling mortality. Planting inmineral soil also lowered the mortality rate, which emphasized theimportance of planting and site preparation quality (Paper I). Selection ofsite preparation method was found to be of minor importance. The sitepreparation’s ability to create suitable planting spots was most important forseedling survival and growth. Selection of site preparation affected soildisturbance, and natural regeneration was promoted with all methods usedin the experiments (Paper II). Adapting planting position choice, followingsite preparation, to within-site variation was valuable to decrease mortalityrates and promote growth (Paper II-III). In wet conditions, elevatedplanting positions were advantageous compared to lower ones, but moreflexibility could be applied in drier conditions. Norway spruce, Scots pine,and silver birch reacted differently to planting position choice (Paper III).Paper I-III indicated that digital tools could be used in regenerationplanning. A depth-to-water-raster successfully explained seedling mortalityand growth in the extreme ends of the soil moisture spectrum. Using remotesensing derived variables can be valuable for further mapping andunderstanding of between and within-site variation in future regenerationplanning. There were no long-term negative effects on stand productivityafter 30 years following site preparation. The standing volume was largestafter ploughing but disc trenching and mounding also had higher standingvolume than the unscarified control (Paper IV). I conclude that regenerationdecisions made today, regarding species selection and regeneration method,should strive for increased precision for the benefit of the forests oftomorrow.

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Successful spruce regenerations – impact of site preparation and the use of variables from digital elevation models in decision-making?

Nordin

Olofsson

Hjelm

2022

Scandinavian Journal of Forest Research

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Varying rectangular spacing yields no difference in forest growth and external wood quality in coniferous forest plantations

Cited by 5 publications

References 13 publications

Evaluating thinning practices and assessment methods for improved management in coniferous production forests in southern Sweden

Evaluating thinning practices and assessment methods for improved management in coniferous production forests in southern Sweden

Regeneration measures in time and space: Site preparation, planting and digital tools

Successful spruce regenerations – impact of site preparation and the use of variables from digital elevation models in decision-making?

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