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

ABSTRACT Various site preparation methods are used in Swedish forestry. However, some methods can lead to unnecessary disturbance, which could be avoided by using variables from digital elevation models in management decisions. The current study aimed to investigate how different site preparation methods, and their intensities, affect Norway spruce (Picea abies (L.) Karst.) regeneration. Additional aims were to clarify how these methods affect soil disturbance and vegetation development, along with how variables from digital elevation models could be used in silvicultural decision-making. Experimental sites were established in southern Sweden to assess five different site preparation treatments with different planting densities: (1) conventional disc trenching 2500 seedlings/ha (DT2500); (2) low intensity disc trenching 1250 seedlings/ha (LDT1250); (3) low intensity disc trenching 2500 seedlings/ha (LDT2500); (4) low-intensity patch-wise 1250 seedlings/ha (PW1250); and (5) patch-wise 2500 seedlings/ha (PW2500). Site preparation intensity had no effect on seedling growth and, survival or vegetation development; the tested treatments differed in terms of soil disturbance. Planting spot properties and weather conditions influenced the seedling performance. DTW and slope could not substantially explain either seedling growth or survival. The results indicate that the choice of site preparation method should consider flexibility when planting while adapting the level of disturbance accordingly.