TABLE 1

Effects of carbon dioxide, temperature, and nitrogen increases on bacterial communities and biogeochemistry in northern forests in manipulative experimentsa

ManipulationHabitatVegetationEffects on biogeochemistryEffects on bacterial populationsEffects on bacterial taxaSelected reference(s)
[CO2]Temperate forestPinus taeda, Populus tremuloides, Populus alba, Pinus nigra, Acer saccharum, Betula papyrifera↑ NPP, ↑ efficiency of C-fixing enzymes, ↑ N sequestration= bacterial biomass, = AOB biomass, ↑ bacterial diversity= Proteobacteria (↓ Bradyrhizobium, ↑ Rhodoplanes, ↑ Pseudomonas, ↑ Nitrosospira), ↑ Actinobacteria,Bacteroidetes, ↓ Acidobacteria (except Gp4 and Gp6)207, 235, 236, 241, 271
Temperate forestPinus taeda↑ dichotomous branching index, ↑ root soil exploration, ↑ exudation (growing season), ↑ NAGase activity, ↑ phenol oxidase, ↑ NH4 turnover↑ microbial biomass (growing season)120, 121
Temperate forestPopulus tremuloides, Betula papyrifera, Acer saccharum, Pinus sylvestris↑ SOM decomposition, ↑ decomposition of low-molecular-weight organic acids= bacterial abundance, ↑ bacterial diversityAcidobacteria, ↓ Bacteroidetes, ↑ Burkholderia, ↑ Nitrosospira152, 240
Temperate forestFagus sylvatica= NPP, ↑ SOM decomposition, ↑ genes for decomposition of labile C, = NH4, ↑ NO3 depletion, ↑ exudation↓ bacterial diversityPseudomonas,Actinobacteria,Planctomycetes,Firmicutes,Acidobacteria (except Gp5, Gp6, and Gp7)144
Temperate forestFagus sylvatica, Quercus robur, Quercus petraea, Carpinus betulus= NPP, = NH4, ↑ NO3 accumulation, = C/N ratio for trees243
TempBoreal forestAbies balsanea, Pinus sylvestris, Picea abies↑ soil respiration, ↑ enzyme activities on labile C, = SOM decomposition= microbial biomass, ≠ microbial community composition231, 272
Temperate forestPicea asperata↑ root exudation rates, ↑ C/N ratio for exudates, ↑ SOM decomposition273
Temperate forestPicea rubens, Abies balsamea, Fagus grandifolia, Acer saccharum, Acer rubrum, Betula lenta, Prunus serotine, Quercus rubra↑ soil respiration, ↑ SOM decomposition, ↑ Vmax of enzymes274, 275
Temperate forestBetula papyrifera, Betula lenta, Acer rubrum, Quercus velutina, Quercus rubra, Fagus grandifolia, Picea abies, Fagus sylvatica, Abies alba↑ soil respiration, ↑ extracellular enzyme activity, = C, = N= bacterial biomass, ≠ bacterial community composition↓ Gram-negative bacteria, ↑ Acidobacteria, ↑ Alphaproteobacteria16, 246, 276
Temperate forestAcer rubrum, Betula papyrifera, Quercus velutina, Acer pensylvanicum↑ oxidative activity↑ bacterial diversityAcidobacteria, ↑ Actinobacteria234
NBoreal forestPicea abies↑ soil C (high N deposition), ↓ soil respiration (high N deposition)↓ bacterial biomass, = amoA gene abundance, ≠ AOB community composition263, 267
Temperate forestAcer saccharum↓ SOM decomposition, ↓ soil respiration, = NPP, ↑ OM in forest floor, ↓ extracellular enzyme activity, ↑ N in soil organic matter, ↑ NO3 leaching↓ bacterial diversity (site specific), ↑ carbohydrate metabolism genes, ↑ aromatic metabolism genes, ↑ respiration metabolism genes, ↓ chitin decomposition genes (site specific), ↓ lignocellulose decomposition genes (site specific), ↓ N cycle genes (site specific)Bacteroidetes, ↓ Gammaproteobacteria, ↑ Firmicutes, ↑ Actinobacteria, ↓ Acidobacteria, ↓ Verrucomicrobia213, 260262, 264
Temperate forestFagus grandifolia, Acer saccharum, Acer rubrum, Picea rubens↓ soil respiration (P. rubens site)↓ microbial biomass (P. rubens site)257
Temperate forestPinus resinosa, Quercus velutina, Quercus rubra, Betula lenta, Acer rubrum, Fagus grandifolia↓ soil respiration, ↓ SOM decomposition, ↑ C stocks (except at Pinus site), ↑ tree biomass, ↓ extracellular enzyme activity, ↑ lignin recalcitrant C, ↑ NO3, ↑ nitrification, = litter fall (except ↑ at Pinus site), = root biomass (except ↓ at Pinus site), = root productivity↓ microbial biomass, ↑ bacterial richness, ↑ specific operational taxonomic unitsProteobacteria, = Acidobacteria257, 266, 268
Temperate and boreal forests↑ aboveground NPP, ↑ belowground C, ↑ tree growth, ↑ litter fall, = litter decomposition, = soil respiration, ↑ C sink↓ microbial biomass277
  • a Arrows indicate increases and decreases of the listed parameters. =, no significant change in the parameter; ≠, significant change in the parameter.