Study of potential long term effects of fertilizing regimes on growth and seedling establishment in a spruce stand

Despite the December darkness, snow conditions, and at times bitterly cold weather (as much as - 28°C a few days ago), outdoor activities in the forest of Svartberget Research Station are ongoing.

Manual harvest of trees in Svartberget Experimental Forest (Photo: Linnea Larsson) Manual harvest of trees in Svartberget Experimental Forest (Photo: Linnea Larsson)

Currently there is an on-going manual harvest of trees in two field trials at Svartberget Experimental Forest. The harvest has two aims; one aim is to transform the forest into what will eventually be a nice forest to stroll around in and the other is to move, as a first step, towards an example of continuous cover forestry (CCF). A common belief is that this would require a J-curve relationship between tree diameters and tree frequencies, characterized by many small trees and a few larger trees. The manual felling in the plots and the machines driving between plots, are conducted in way to leave as much as possible the existing natural regeneration intact. The forest may not look so nice now, but over time that impression will hopefully change.

The history of this particular forest is a bit complicated with three layers of field trials superimposed on top of each other. The first layer being a former scaling experiment established in 1995 at Svartberget with the aim of understanding the effects of nitrogen deposition on the composition of vegetation. The original scaling experiment constituted five plot sizes (1, 10, 100, 1000, 5000 m2) with three fertilization treatments (0, 12.5, 50 kg N/ha/year). The second layer, established in 2014 by using the original plots in the former experiment, includes two field trials, #7104 and #7105. In one of the field trials only the original 1000 m2 plot and the corresponding fertilization treatments were re-used. In the other trial, the original 5000 m2 plot was used to create 100 x 200m plots with 12 pairwise subplots, one recovering plot and one fertilized plot. All trees were measured and also their geographic positions recorded when these trials were established. The third layer is the current transition of the field trails to CCF conditions. All old trees have now been measured and also inventories of re-growth of new trees and shrubs in the plots have been performed.

What do we expect to find over time by studying the plots? For example, that the addition of nitrogen may promote seedling establishment and growth but maybe also results in more competing vegetation hampering successful seedling establishment. Time will tell.

Field trial layers at Svartberget Experimental Forest.
Field trial layers at Svartberget Experimental Forest.

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