title: Depression of belowground respiration rates at simulated high moose population densities in boreal forests.
abstract: Large herbivores can affect the carbon cycle in boreal forests by changing productivity and plant species composition, which in turn could ultimately alter litter production, nutrient cycling, and the partitioning between aboveground and belowground allocation of carbon. Here we experimentally tested how moose (Alces alces) at different simulated population densities affected belowground respiration rates (estimated as CO2 flux) in young boreal forest stands situated along a site productivity gradient. At high simulated population density, moose browsing considerably depressed belowground respiration rates (24-56% below that of no-moose controls) except during June, where the difference only was 10%. Moose browsing depressed belowground respiration the most on low-productivity sites. Soil moisture and temperature did not affect respiration rates. Impact of moose on belowground respiration was closely linked to litter production and followed Michaelis-Menten dynamics. The main mechanism by which moose decrease belowground respiration rates is likely their effect on photosynthetic biomass (especially decreased productivity of deciduous trees) and total litter production. An increased productivity of deciduous trees along the site productivity gradient causes an unequal effect of moose along the same gradient. The rapid growth of deciduous trees may offer higher resilience against negative effects of moose browsing on litter production and photosynthate allocation to roots.
authors.affiliation: Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, SE 90183 Umeå, Sweden. inga-lill.persson@vfm.slu.se
authors.forename: Inga-Lill
authors.initials: IL
authors.lastname: Persson
authors.forename: Mats B
authors.initials: MB
authors.lastname: Nilsson
authors.forename: John
authors.initials: J
authors.lastname: Pastor
authors.forename: Tobias
authors.initials: T
authors.lastname: Eriksson
authors.forename: Roger
authors.initials: R
authors.lastname: Bergström
authors.forename: Kjell
authors.initials: K
authors.lastname: Danell
mesh_terms: D000818:Animals; D002245:Carbon Dioxide; D003670:Deer / Q000502:physiology*; D017753:Ecosystem; D010101:Oxygen Consumption; D011156:Population Density; D012987:Soil; D013997:Time Factors; D014197:Trees
chemical_list: D012987:Soil; D002245:Carbon Dioxide