title: Mycorrhizal type determines the magnitude and direction of root-induced changes in decomposition in a temperate forest.
abstract: Although it is increasingly being recognized that roots play a key role in soil carbon (C) dynamics, the magnitude and direction of these effects are unknown. Roots can accelerate soil C losses by provisioning microbes with energy to decompose organic matter or impede soil C losses by enhancing microbial competition for nutrients. We experimentally reduced belowground C supply to soils via tree girdling, and contrasted responses in control and girdled plots for three consecutive growing seasons. We hypothesized that decreases in belowground C supply would have stronger effects in plots dominated by ectomycorrhizal (ECM) trees rather than arbuscular mycorrhizal (AM) trees. In ECM-dominated plots, girdling decreased the activity of enzymes that break down soil organic matter (SOM) by c. 40%, indicating that, in control plots, C supply from ECM roots primes microbial decomposition. In AM-dominated plots, girdling had little effect on SOM-degrading enzymes, but increased the decomposition of AM leaf litter by c. 43%, suggesting that, in control plots, AM roots may intensify microbial competition for nutrients. Our findings indicate that root-induced changes in soil processes depend on forest composition, and that shifts in the distribution of AM and ECM trees owing to climate change may determine soil C gains and losses.
authors: Department of Biology, West Virginia University, Morgantown, WV, 26506, USA.
authors: Edward R
authors: ER
authors: Brzostek
authors: Department of Geography, Indiana University, Bloomington, IN, 47405, USA.
authors: Danilo
authors: D
authors: Dragoni
authors: Department of Biology, Indiana University, Bloomington, IN, 47405, USA.
authors: Zachary A
authors: ZA
authors: Brown
authors: Department of Biology, Indiana University, Bloomington, IN, 47405, USA.
authors: Richard P
authors: RP
authors: Phillips
mesh_terms: D002244:Carbon / Q000378:metabolism; D019069:Cell Respiration; D065928:Forests; D006813:Humidity; D038821:Mycorrhizae / Q000502:physiology*; D009584:Nitrogen / Q000378:metabolism; D018515:Plant Leaves / Q000502:physiology; D058441:Rhizosphere; D012987:Soil; D013696:Temperature
chemical_list: D012987:Soil; D002244:Carbon; D009584:Nitrogen
keywords: arbuscular mycorrhizal (AM) fungi; belowground carbon allocation; ectomycorrhizal (ECM) fungi; girdling; rhizosphere; soil enzymes