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? Rhizodeposition, or the addition of C from roots to soil C pools, is expected to increase if net primary production is stimulated and some excess C is allocated below-ground. We investigated the effects of 5 yrs of elevated CO2 on below-ground C dynamics in a native, C3?C4 grassland ecosystem in Colorado, USA. ? Cylinder harvests following each growing season and monolith excavation at the end of the experiment provided data on root biomass, root C : N ratios, and root and soil ?13C values. We applied an isotopic mixing model to quantify new soil C inputs on elevated and ambient CO2 treatments. ? Root biomass increased by 23% and root C : N ratios increased by 26% after 5 yrs of elevated CO2. Species-specific...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: 13C/12C,
C : N ratio,
New Phytologist,
elevated CO2,
rhizodeposition, All tags...
root biomass,
roots,
soil carbon,
stable isotopes, Fewer tags
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Shrub encroachment into grass-dominated biomes is occurring globally due to a variety of anthropogenic activities, but the consequences for carbon (C) inputs, storage and cycling remain unclear. We studied eight North American graminoid-dominated ecosystems invaded by shrubs, from arctic tundra to Atlantic coastal dunes, to quantify patterns and controls of C inputs via aboveground net primary production (ANPP). Across a fourfold range in mean annual precipitation (MAP), a key regulator of ecosystem C input at the continental scale, shrub invasion decreased ANPP in xeric sites, but dramatically increased ANPP (>1000 g m?2) at high MAP, where shrub patches maintained extraordinarily high leaf area. Concurrently,...
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Shrub encroachment into grass-dominated biomes is occurring globally due to a variety of anthropogenic activities, but the consequences for carbon (C) inputs, storage and cycling remain unclear. We studied eight North American graminoid-dominated ecosystems invaded by shrubs, from arctic tundra to Atlantic coastal dunes, to quantify patterns and controls of C inputs via aboveground net primary production (ANPP). Across a fourfold range in mean annual precipitation (MAP), a key regulator of ecosystem C input at the continental scale, shrub invasion decreased ANPP in xeric sites, but dramatically increased ANPP (>1000 g m?2) at high MAP, where shrub patches maintained extraordinarily high leaf area. Concurrently,...
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The shortgrass steppe is a semi-arid grassland, where elevated CO2 reduces stomatal conductance and promotes soil moisture storage. Enhanced biomass growth from elevated CO2 has been attributed in part to soil moisture effects. However, the influence of this soil moisture feedback on C cycling has received little attention. We used open-top chambers to increase atmospheric CO2 concentrations to twice-ambient for four growing seasons. Soil respiration rates and stable C isotopes of soil CO2 were measured during the third and fourth seasons. Elevated CO2 increased soil respiration rates by ?25% in a moist growing season and by ?85% in a dry season. Stable C isotope partitioning of soil respiration into its components...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: 12,
13,
American Geophysical Union,
C,
C/, All tags...
Global Biogeochemical Cycles,
decomposition,
rhizosphere respiration,
shortgrass steppe,
soil C cycling,
stable isotopes, Fewer tags
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Shrub encroachment into grass-dominated biomes is occurring globally due to a variety of anthropogenic activities, but the consequences for carbon (C) inputs, storage and cycling remain unclear. We studied eight North American graminoid-dominated ecosystems invaded by shrubs, from arctic tundra to Atlantic coastal dunes, to quantify patterns and controls of C inputs via aboveground net primary production (ANPP). Across a fourfold range in mean annual precipitation (MAP), a key regulator of ecosystem C input at the continental scale, shrub invasion decreased ANPP in xeric sites, but dramatically increased ANPP (>1000 g m?2) at high MAP, where shrub patches maintained extraordinarily high leaf area. Concurrently,...
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