Nitrogen deposition and the biodiversity of boreal forests: implications for the nitrogen critical load.
The critical load concept is used to establish the deposition levels which ecosystems can tolerate without significant harmful effects. Here we summarize work within the Swedish research program Abatement Strategies for Transboundary Air Pollution (ASTA) assessing the critical load of N for boreal forests. Results from both field experiments in an area with low background N deposition in northern Sweden, and from a large-scale monitoring study, show that important vegetational changes start to take place when adding low N doses and that recovery of the vegetation after ceasing N input is a very slow process. The data presented indicate that changes in key ecosystem components occur even at a lower rate of N input than the present recommended empirical critical load for boreal forest understorey vegetation of 10-15 kg N ha(-1) yr(-1). Based on the data presented, we suggest that the critical load should be lowered to 6 kg N ha(-1) yr(-1).
Nordin
Annika
A
Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, Sweden. annika.nordin@genfys.slu.se
Strengbom
Joachim
J
Witzell
Johanna
J
Näsholm
Torgny
T
Ericson
Lars
L
D003247:Conservation of Natural Resources; D017753:Ecosystem; D004784:Environmental Monitoring; D009584:Nitrogen / Q000506:poisoning*; D063245:Plant Development; D011157:Population Dynamics; D013548:Sweden; D014197:Trees
D009584:Nitrogen