Forest litter amendment during nursery stage influence field performance and ectomycorrhizal community of Scots pine (Pinus sylvestris L.) seedlings outplanted on four different sites

•The effect of litter addition in the nursery on outplanted Scots pine was assessed.•Litter stimulated root growth and beneficial mycorrhizal community in nursery stage.•After outplanting enhanced survival of litter treated seedlings was found.•Mycorrhizas on outplanted trees were rather structured by site than by treatments.•Use of forest litter to increase seedling survival after outplanting is recommended.