Water level impact on pine seedlings in greenhouse conditions: assessing growth and survival potential in ditched and managed peatlands

Tree establishment on peatlands has various adverse effects on the environment, with one of the most significant being their transformation from carbon sinks to carbon sources. This transformation has largely been instigated by economic-driven ditching initiatives. In this study, 80 peat-rooted pine seedlings were subjected to hydrological scenarios corresponding to natural, ditched, and rewetted conditions to investigate how different management strategies affect tree growth and survival. The study was conducted in a greenhouse where all plants were exposed to identical conditions except for the water level, and focused on factors like stomatal conductance, plant survival, length, biomass, and radial tree growth. Wet conditions, specifically treatments rewetted and natural, resulted in consistently lower stomatal conductance compared to drier treatments. Plant survival was affected, with 15 deaths in the rewetted and 2 in natural groups. Moreover, length, biomass, radial growth, and cell formation were significantly lower for the groups exposed to wet conditions. Rewetting can therefore effectively control tree colonisations, and thereby preventing water consumption, litter fertilisation, and other positive feedback effects for the trees that might be negative for the carbon uptake and biodiversity in peatlands. This study thereby offers valuable insights for rewetting initiatives in tree colonised peatland ecosystems.