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

Abstract

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.